Model Engine Maker

Engines => From Plans => Topic started by: petertha on January 19, 2021, 02:21:46 AM

Title: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 19, 2021, 02:21:46 AM
Iíve been working on this radial engine on & off for <ahem> more than a few years now. You may have seen some of my prior questions or random posts scattered elsewhere on the forum. Progress has been pretty slow with the usual factors - time constraints, distractions & learn-as-you go snailís pace. I also had a few unwelcome interruptions with my machines. The drive train on my í97 Taiwan 14x40 lathe developed problems which took some time to source parts & repair. Then shortly thereafter my same vintage RF-45 mill gearbox decided it wasnít happy with the world. Ultimately I decided to upgrade the mill but that required some shop shuffling & electrical work.

Anyway, rolling time forward to present day, I might actually be on the home stretch. So I figure itís a good time to post my prior construction journey and transition into present day work so it will appear as a normal, continuous construction exercise. Actually, looking back at some of my pictures & notes leaves me wondering what I actually did myself, so this documentation exercise will benefit me as well.

I really wanted to build a radial and avoid castings to mess up, so 5 cylinders is kind of the minimum order, at least of the more common radial plans available. The Ohrndorf seemed well designed from my amateur comparisons to other 5-cyl radials. Nothing stood out as radical or unconventional. There is a YouTube video of it running. Hard to tell, but possibly it is an early prototype. I liked the overall proportions & some aesthetic features. Anyways, it ticked most of the boxes for me at the time.

Experience wise, this is my first engine. Iíd made a few prior metalworking gadgets, but nothing remotely close to this level. I decided to attempt a single cylinder assembly prototype and if that turned out OK, then Iíd carry on with the rest of the engine. The engine has yet to run, so weíll ultimately see if that path was the right decision. Wish me luck!
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 19, 2021, 02:23:20 AM
Design
The engine is designed by Martin Ohrndorf of Modellbau & Technik (Germany). On his web site he offers various other plans if you are so inclined (no personal affiliation). There are also some YouTube videos of his engines running.
https://www.engineman.de/
https://www.engineman.de/produkt/bauplan-5-zylinder-sternmotor/

Engine Specs
Methanol fuel, glow plug ignition
Bore = 24 mm
Stroke = 22 mm
Displacement = 50 cc (10 cc per cylinder)
Weight ~ 1900 g
RPM ~ 950 Ė 5,500
Outer diameter ~ 225 mm
Length ~ 165 mm
Propeller size 18x14 to 22x12 inch
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 19, 2021, 02:24:07 AM
Plans
The 2D hardcopy plans are most certainly derived from a 3D CAD model. They are metric dimensions, corresponding to metric components & tooling. The instructions are in German & quite brief, however I was able to occasionally communicate with Martin by email to answer the odd question.

Once I had the plans, I set about re-drawing parts into my own CAD model. This isnít a necessity but it certainly helped me on multiple fronts. I was better able to understand the assembly details, make my (imperial dimensioned) shop drawings, design jigs & fixtures etc. Ultimately I made a few changes here & there which Iíll detail, but for the most part stuck to the original design.

Iíll use the abbreviations O5 & O9 for the (Ohrndorf) 5 & 9 cylinder engines respectively. The 05 shares about half its parts with the 09. Unfortunately you need to purchase both O5 & O9 plan sets in order to build the 05. I suspect the O9 came first & the O5 later. The O5 plans have a pseudo assembly sheet that specifies whether to use a stock O9 part, or modify an O9 part, or make a new O5 part. This involves a bit of juggling to keep straight. A single set of O5 plans would certainly have been more convenient, but it is what it is. Who knows, maybe Iíll build the O9 one day.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 19, 2021, 02:27:47 AM
Plans overview & video link

Wod5S4XuKTM
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 19, 2021, 02:29:39 AM
Cad pics missing pushrods, carb, inlet/exhaust accessories & some other bits
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 19, 2021, 02:33:11 AM
Construction & Design
The engine is bar stock, no castings. Hardening is required on some specific parts. Remaining commercial components include metric fasteners, bearings, spur gears, ring gear, O-rings, circlips & such. I planned on cutting the spur gears for the learning experience, but ended up purchasing them along with the internal (ring) gear because all the gears require modification. Apparently ring gears are a bit involved to (properly) cut teeth profiles in the home shop. I found all the gears readily available at https://www.maedler.de/

RC glow plug ignition was my preference on a first build because it seemed simpler than spark in some respects. I have some RC experience so maybe it was more the devil you know, albeit no prior involvement with multi-cylinder engines or radials. Iíll have to figure out an igniter system when the time comes.

Lubrication is somewhat similar to other glow engines, oil is premixed with the methanol fuel. Specific to the O5, intake charge enters from the rear mounted carb into the crankcase where it mists over the moving master/link rod assembly, then flows backwards out through the induction tubes into the heads. One unique feature of the O5 is that the nose case is compartmentally sealed from the crankcase & partially filled with oil bath for the planetary gear train & cam plates to splash in. I liked this concept because it mitigates an oil pump system. But Iím also wondering what keeps oil from seeping out past the lower, submerged tappets (cam followers). He uses the same bath philosophy on the larger O9, although there seem to be seal differences between engines. Alternately, other glow radials allow the intake mist to continue further forward, flowing into the nose case via openings in the front gear plate. This option is still available to me with some modifications. So Iím still mulling this issue over in terms of how to proceed. I assume the rocker assembly gets lubricated by occasional maintenance oiling & fuel residue working its way between the valve stem & guide. At least thatís how commercial RC 4S engines seem to work.

The pistons have a single compression ring. My plan all along was to use commercial RC rings, specifically from an OS-56-4S engine because the nominal bore dimensions are very close to the O5. I thought this might provide some insurance against making inferior rings & experiencing running problems. I just assumed by matching the O5 bore & piston geometry to the OS-56, I would be good to go. What I didnít appreciate at the time is that this construction path actually requires more exacting work on multiple fronts, but Iíll save that for later. I still intend to make my own rings because thatís part of model engine building. Whether itís worth swapping them into this engine to see the difference remains to be determined. Because the liners are also cast iron, I assume they will run in together with the rings, as opposed to commercial RC liners which are typically hard chromed. Iím not sure I will ever fly the engine so I doubt Iíll wear them out between the test stand & trophy shelf.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 19, 2021, 02:40:49 AM
Pics of the prototype. If only I knew what was ahead of me LOL.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Laurentic on January 19, 2021, 11:03:25 AM
Peter - this is an interesting project, and one close to me.  I am in the process of completing a 3 cyl radial that was part built before the originator died and a friend of his sold it on to me.  Mine came with crankcase and end covers, division plate to crankcase, cylinders, heads, crankshaft and conn rods done but no more.  And NO plans!  So I have had to laboriously measure all the bits I had then design the missing bits to fit into what existed, drawing it all up in CAD, and then go back and modify some of the drawn parts as my thoughts changed.

Interestingly, mine is also designed for glow fuel, as the inlets are plumbed into the crankcase, so I modified the division plate to the gear area to solid with JB Weld so the gearbox/cam area could be lubricated by oil bath.  I also arranged the gears and cams very similar to how yours looks, but not nearly so neat!!  I have been making progress on this area, having just made the cams, cam support ring and gears including an internals gear and am in the process of fitting it in all together to make sure all fits as it should.  Making the gears including the internal gear was all new to me.  Made the internal gear using my RF-25 derivative mill as a broach.  It all works, sort of, now needs running in.

Will follow your build with considerable and very close interest!!

Chris

PS Can't believe how readily the engine started in the video, it certainly is a runner!
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Vixen on January 19, 2021, 12:18:44 PM
Hello Peter,

This is an interesting engine to build. As you said it looks well designed, quite conventional with no obviously 'quirky' bits.

The engine parts you have shown look great. Your write up and presentation are also a credit to you. I will be following your progress as you proceed. 

The Ohrndorf O5 and my Seidel ST540 are very similar in both design and size, so we should be able to compare notes.

Mike   :atcomputer:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Mike R on January 19, 2021, 05:53:39 PM
Iíve been working on this radial engine on & off for <ahem> more than a few years now.

Too painfully familiar with that phrase.  You're intro to this engine build reads very similar to my experience, but I dove into the radial engine world on a 9 cylinder with castings version! 
I will be following along closely as well.

Mike
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 20, 2021, 04:57:35 AM
Mike.R - Look forward to seeing your build progress. Hopefully my ramblings will inspire you as others have inspired me. Or put another way, provide you specific knowledge of how NOT to do certain things!

Laurentic - Same message. Sounds like a very interesting project. Would love to see some details when you are ready to share.

Vixen - thanks for the interest & nice comments
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 20, 2021, 05:05:56 AM
Crankcase 1. The crankcase is made from 2024 aluminum. My notes show that I started the first one in 2017, but there were a few binners along the way.

The turning operations went well, but I ran into issues cutting the cylinder facets. Possibly the setup shifted slightly. But I suspect it was my poor choice gripping the fixture OD with a 3J chuck and/or not properly confirming things where it mattered. Near the end of cutting depth, I noticed the facets were not breaking through quite equally to the internal master rod clearance groove. Not a good sign. Since the internal groove was turned in the same lathe operation as the OD, it could only mean one thing Ė radial runout. Therefore the facets were not equal distance relative to the CC centerline. Therefore each cylinder assembly would end up slightly up or down & a domino effect of bad things thereafter; piston geometry, compression ratioÖ. That that would never do. Lesson learned. Aluminum Gods = 1 point, Apprentice = Zero.

The dud part did provide some utility value. I used it to go through the motions of boring & finishing the cylinder skirt holes to tolerance as I was kind on new to boring head operations.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 20, 2021, 05:08:33 AM
Crankcase 2. Turning operations went good. Repetition builds confidence. This time I reverted to an independent 4J chuck for the radial operations to ensure no runout & tight grip. I also made some improvements to the mounting plate. Radial & axial runout was confirmed, this time the facets came out good. The cylinder liner holes were bored. Then while tapping the proverbial last hole (or thereabouts) for the cylinder flanges, I experienced the dreaded broken off tap. ACK!

It was entirely my own fault. The holes were blind end M3 thread. A bit finicky but nothing onerous. After feeling quite confident with my shiny new tapping head, I decided this would be a good application. However, in hindsight, I didnít properly factor the over-depth allowance as the instructions clearly convey. So with tap firmly stuck in hole, what now. I tried drilling on the end with a carbide, no go. I tried heat. I didnít have access to EDM or anything like it. After some forum Q&A and very convincing YouTube testimonials, I decided to try the alum solution. It was a disaster. The process slowly turned the part into something that resembled an artifact from the Titanic. The tap was slightly smaller but still there. Rather than take up more space, Iíll just insert a few choice R.I.P. pics if you want to read the original saga on the other forum and weíll carry on. Aluminum Gods 2 points, Apprentice still zero.
https://www.homemodelenginemachinist.com/threads/broken-tap-in-aluminum-cranckase.26470/
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 20, 2021, 05:14:02 AM
Crankcase 3. After 2 warm up exercises, this was the keeper. WellÖ maybe. Dimensionally everything was good but as I look back on the pics of so-so thready finish, I think my lathe was trying to tell me something even at that point. Forewarning of ominous events around the corner. Anyways, pleasant thoughts for now. This is how it crankcase making SHOULD have gone.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 20, 2021, 05:18:50 AM
Crankcase
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 20, 2021, 05:20:48 AM
CC cleaned up a bit, nearing completion
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Vixen on January 20, 2021, 12:47:44 PM
Hello Peter,

Top marks for persistence.  :ThumbsUp: :ThumbsUp: :ThumbsUp:        I suspect I would have given up before the third attempt.

As for Alum to remove broken taps  :facepalm: It's usually credited as being the way to go . Now; having tried it several times, without success, I believe it is just an 'old wives tale' which is repeated time and time again by those believers, who have not actually quite got it to work.

Radial engine are a lot of repetitive work. Just stick with it.

Mike   :atcomputer:

Title: Re: Ohrndorf 5 Cylinder Radial
Post by: ozzie46 on January 20, 2021, 01:33:31 PM
Actually I usex the alum trick when I made my "Mastiff" engine and it worked great. Used a teflon pan, kept the alum mixture saturated and the tap evaporated into bits. No discoloration to the aluminum part.

Ron
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Vixen on January 20, 2021, 02:06:16 PM
I stand corrected.

It never worked for me, I only got discoloured aluminium with the broken tap unmarked and intact. Maybe there is more than one substance being sold as 'alum'.

Was it a carbon steel tap or a high speed steel tap?

Mike
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Roger B on January 20, 2021, 02:44:35 PM
There are a range of different Alum compounds. Alum alone usually refers to potassium aluminum sulfate KAl(SO4)2∑12H2O. I have also used this to sucessfully remove broken HSS taps from brass aluminium parts. It requires time, some heat and some agitation to ensure that there is fresh alum solution in contact with the tap. It has no effect on carbide taps. I don't know if the type of aluminium also has an effect  :headscratch:

The picture is what was left of an M2 tap that was broken in a big end cap after alum treatment. It also took the marking blue off the cap.
 
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Vixen on January 20, 2021, 02:54:25 PM
Hello Roger

Where did you source your potassium aluminum sulfate KAl(SO4)2∑12H2O? Was it from a chemicals firm?

E-bay may not be the best place to buy it. The product descriptions are not always as reliable as we would like.

Mike
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Roger B on January 20, 2021, 05:05:12 PM
Hello Mike,

This came from the lab at work so I am fairly certain that's what I got.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Vixen on January 20, 2021, 05:08:31 PM
Hello Mike,

This came from the lab at work so I am fairly certain that's what I got.

Ha ha,  :ThumbsUp: :ThumbsUp: I think I would trust your lab at work any day, compared to the e-bay sellers.

Do they take outside orders????

Mike
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: ozzie46 on January 20, 2021, 06:19:15 PM
I stand corrected.

It never worked for me, I only got discoloured aluminium with the broken tap unmarked and intact. Maybe there is more than one substance being sold as 'alum'.

Was it a carbon steel tap or a high speed steel tap
Used grocery store alum.

Mike

HHS tap.
Ron
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 21, 2021, 01:35:06 AM
Questionable grocery store alum may have been part of my issue. Another factor may have been this particular tap. It had a coating which may have provided a permeability barrier to inhibit chemical action? The tap is suited for aluminum & cuts like a damn. But all bets off if you drive any kind of tap into the celler. Initially there was an encouraging stream of bubbly-bubbly's coming directly from the tap shrapnel top, possibly acting only on the exposed core metal? I really don't know. I've seen YouTubes where much larger (I suspect conventional bright HSS) taps were fizzed out in no time & native part looked no worse for wear. I treated time lapse YouTube video as one step more believable over well meaning, but likely unproven recipes of Grampa's surefire pickle juice concoctions.

FWIW, after this episode I made a rudimentary coring plug cutter from O1. My edge was just hand ground with a Dremel, but the basic idea was like an annular cutter. Unfortunately without nice sharp sidewall flutes, just reduced diameter for clearance. We're talking only 3mm nominal here. I simulated a broken tap with a pin sticking out of the hole. I peck drilled the material with WD-40. It did make progress, I went in about 0.2" & got bored. I think this might better with proper edge grinding. Maybe even a single edge D-bit principle? The idea is drill out the surrounding area to base of tap & avoid dealing with the tap altogether. Dress the hole, insert tight fitting plug of native material with Loctite or whatever & never tell anyone.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Admiral_dk on January 21, 2021, 11:33:54 AM
Your crankcase looks very nice - shame about the mishap ....  :-\

I must admit that I don't see any real reason for not drilling the holes all the way through .... other than the builder knows it's done ....

On a full size it will help preventing it from 'sweating oil' - but I can't see this with this model that has a vacuum in the crankcase.

Another subject - ball bearings works best with an oil mist to lube them ..!!.. no mention of it being mixed with fuel - but the most durable Danish moped from my youth was a single speed SCO where the whole engine and gears are inside the crankcase and lubed from the gasoline / oil mix (5%) and they regularly ran more than 250,000Km. before any rebuild.
So I'm not sure that having a seperate oil section for the cam-box is necessary .... but I will not claim that it's a bad idea either ....

Best wishes

Per
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Laurentic on January 21, 2021, 02:00:17 PM
Per - there is not just the ball race in the gearbox/cam section there are also the gears and the cams.  It was to ensure that these were well lubricated that on my 3 cyl radial I went for a separate section (from the crankcase) with an oil bath, perhaps Peter had the same reasoning I don't know.  Different ships different splices as the saying goes, not to say either way is right or wrong, just the way one sees it!

Chris
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Vixen on January 21, 2021, 03:19:54 PM
Chris,

My five cylinder 40 cc Seidel ST540 radial engine does not have a separate oil bath for the gears and cam section, it uses the oil mist in the fuel (10%).

My big, 350 cc, Bristol Mercury engines have a wet sump and the oil bath arrangement for the cam and gears.

Seems either arrangement can be made to work.

Mike
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Laurentic on January 21, 2021, 03:48:04 PM
Mike - exactly! 

Like I said,  "Different ships different splices as the saying goes, not to say either way is right or wrong, just the way one sees it!"

You pays yer money and yer takes yer choice - as another saying goes!!

Chris
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Vixen on January 21, 2021, 04:20:22 PM
 :ThumbsUp:
Mike
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: AlexS on January 21, 2021, 05:16:55 PM
wow tasty project petertha, would follow this one! And love the sound of the engine in the example video.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 21, 2021, 07:33:25 PM
... I don't see any real reason for not drilling the holes all the way through

... ball bearings works best with an oil mist to lube them no mention of it being mixed with fuel


Hi Per.

On my last crankcase I decided to drill/tap the cylinder flange holes right through vs blind. Much easier. I figure the holes will be plugged with threaded bolt or stud, maybe a drop of weak Loctite for good measure & provide some degree of seal. I'm going on the assumption the crankcase can never be under much vacuum or pressure because at any stage its rear end is connected to ambient via the inlet path from carb/manifold. So just trying to make it not be liquid leaky. Every RC engine I've seen has a collective puddle of oil residue in the bottom & suspect this will be no different. In fact I'm contemplating a removable drain plug.

I mentioned in post#5 that oil is premixed with the methanol fuel in typical RC proportions, even though the design calls for nose case with bath oil. I'm just writing up some further elaboration of the lubrication details with pics & example of other radials as it relates to my crankcase assumptions & decisions thus far.

Your comment about bearings is what crossed my mind too. My RC experience has been to remove the bearing shields to allow the oily fuel mist to lubricate the balls & race. No shields on completely internal bearings, leave the outside shield on external facing bearing. So that's another question mark on the stock design. It kind of infers shields are left on for nose case bearings. But if they contain original grease, the oil will act as a solvent over time. If the shields are removed & grease cleaned out like normal exposed bearings, well that's an open door for oil to migrate from nose case to crankcase. But obviously he is running them like that in some manner so I'm perhaps missing something. But for these collective reasons, that's why I'm leaning towards opening up the now solid face plate with aperture's to allow intake mist to extend further into the nose case for lubrication & drop the bath altogether. This will maybe make more sense with my forthcoming pics.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Art K on January 22, 2021, 02:57:24 AM
Petertha,
Don't have much to add, but this does look like an interesting project. I must say I've always liked radials. I will be following along. I have long considered the big version of the Kinner K5 from SIC. but haven't made any movement on it, To much other stuff going on.
Art
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Admiral_dk on January 22, 2021, 11:17:22 AM
OK, you're right - vacuum is technically not correct in this case - more like negative pressure.  I guess that it's around 85-95% of the outside pressure ....
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 04:35:53 PM
I have long considered the big version of the Kinner K5 from SIC. but haven't made any movement on it
Art

Hi Art. I know the Kinner you are speaking of. In SIC magazine there was the 1/4-scale gasoline spark version & then I believe a 1/5? scale glow version 'JZ5'?
I actually started drawing those up before going down the O5 path. I preferred the big one but the ignition system scared me off. The smaller one is methanol glow. Kinners are very different animals with the rear bank of gears & individual cam shafts as opposed to single I/E cam plates & planetary reduction gears. Choose your poison. It certainly would make for an interesting project. Its been a while since I dabbled in this but I recall some headscratching on the plans. That may have been the JZ5 though. You have to get all the SIC issues in front of you, there are little nuggets of errata here & there. Kens build if you haven't already seen
http://modelicengine.la.coocan.jp/kinner%20index.htm

I even bought a service manual of the B5 & looked at one at a local museum. Thats what my cad snap shot work in progress is about.
https://en.wikipedia.org/wiki/Kinner_B-5

But speaking only from my own (in)experience level, I thought it would be an even bigger gamble versus embarking on an engine like O5, Jung-5 or Edwards-5. Now having more of an appreciation of work that goes into any engine, I think that was the right choice for me. And I repeat, my O5 hasn't even run! LOL

Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 04:40:48 PM
Crankcase Details
The plans call for a tiny 1mm section O-ring groove recess in the front face of crankcase. I think the purpose is to prevent nose case bath oil from exiting along that joint, possibly through some of the faster holes. The gear plate mounts to this face and then the nose section mounts over the plate, both also with O-rings.

As mentioned, Iím still deliberating this nose bath lubrication method & intend to do some simple leak tests with the engine assembled to help me decide. I can still cut this O-ring groove, but Iím dragging my heels a bit. I find them to be a bit fiddly dimensionally so you end up with the fit. If the ring is slightly too proud it will take extra bolt-up pressure to compress enough & still mate the parts. If it ends up too deep in the groove & doesnít get squeezed enough, then the seal is compromised. Also the groove occurs dangerously close to the facet edges & bolt holes.

So the plan on my radar is to first try making a thin Teflon / PTFE gasket. I found some material samples that vary between only .002-.005Ē thick. Iím satisfied that I can make pretty clean gaskets just using a scalpel blade along the edge of a simple CAD/plywood cut out template. I may have to make a simple punch for the holes, but surprisingly even drilling the material came out OK as long as there was backing material. A gasket should provide more surface area be re-usable with disassembly.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 04:44:45 PM
The O5 plans also call for an O-ring groove in the crankcase under each cylinder flange. Curiously the O9 does not have these. It kind of has the appearance of an afterthought. But if it was deemed necessary, than why wasnít it similarly incorporated into the O9 plans? When I drew up my plans I decided to extend my liners a bit deeper into the crankcase, partially for other reasons. They have a sliding snug fit so hoping this will provide additional sealing area. Also I intend to make similar Teflon sheet gaskets under each cylinder flange.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 07:54:45 PM
Before leaving the crankcase for now, I wanted to elaborate on the oil bath lubrication details. I mentioned the O5 design calls for the nose housing to be partially filled with oil. The cam plates, planetary gears & bearings spin inside this housing so bath makes great sense from that perspective.

This view shows the approximate oil level based on recommended fill up volume. Notice how the bottom set of tappets (cam followers) would always be submerged in oil. I envision even medium viscosity oil working its way out through the annulus gap between the cylindrical tappet & the bronze bushing ID hole. The tappets are sliding fit & perpetually moving up & down. So possibly even some light pumping action. Maybe any bypass oil volume is minimal & just migrates down the pushrod tube where it ends up in the lower covers. Iím not really sure. Obviously it must work because itís common to the larger O9
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 07:56:02 PM
Here are some other methanol radial engines for comparison. The common theme seems to be that the gear plate mounted to front side of CC has openings to allow oily fuel itís to carry forward & lubricate the gears, cams & bearings. There is no compartmental liquid oil bath like the O5 & O9.

OS Sirius
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 07:57:12 PM
Jung 7-cylinder radial (Jung-5 is similar)
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 08:01:21 PM
The Edwards radial has an integrated oil pump actuated off the crankshaft. Oil from external tank is directed to specific areas. It drains by gravity into a lower elevation sump where it is recirculated.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 08:17:04 PM
Mike (Vixen) has mentioned his Seidel glow radial. I hadnít come across that engine at the time but maybe for completeness we could have a look at that one too.

I like the Edwards principle. I seem to recall the recommended fuel was straight methanol/nitro and either zero or low percentage (insurance?) oil added because of the pump. I think itís too late to integrate a similar mechanical pump into the O5, it would require be significant modifications.

Iíve toyed with the idea of external electric oil pump. I suppose itís maybe kind of a cheat from vintage standpoint, but so are glow plug drivers & other modern necessities. The engine wouldnít look out of place with external oil feed lines to the nose area. But I know nothing about what kinds of pumps would work so any thoughts welcome.

But if I trust what I think Iím seeing of the mentioned designs which includes established commercial RC engines that probably see much tougher service, then all I would have to do is cut an array of openings into the front gear plate & it might closely resemble that arrangement. Remove the bearing shields as previously mentioned & fingers crossed that rear entering intake mist sufficiently coats the important rotating bits in the nose case.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Vixen on January 22, 2021, 09:12:39 PM

This view shows the approximate oil level based on recommended fill up volume. Notice how the bottom set of tappets (cam followers) would always be submerged in oil. I envision even medium viscosity oil working its way out through the annulus gap between the cylindrical tappet & the bronze bushing ID hole. The tappets are sliding fit & perpetually moving up & down. So possibly even some light pumping action. Maybe any bypass oil volume is minimal & just migrates down the pushrod tube where it ends up in the lower covers. Iím not really sure. Obviously it must work because itís common to the larger O9

Peter,
It may not do any harm to fit a small baffle plate across the engine more or less level with the oil level shown. It would act as a small oil reservoir. Oil mist would easily find it's way forward, oil droplets could collect in the oil well you have formed, from there it would be distributed all around by the cam gear. True, some oil would migrate down the pushrod tubes but that would be just like every other radial engine, full size or a scale model. It's called authentic.

Just my thoughts

Mike

PS any residual oil left in the crankcase after a run, will drain down into the lower cylinders. past the pistons and into the cylinder heads. There is a danger of a hydraulic lock if too much oil reaches the cylinder heads. It is normal practice to walk the engine through at least 2 complete revolutions (eight blades)  to clear the oil before appalling the starter
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Laurentic on January 22, 2021, 10:37:42 PM
Peter - when I was at sea it was common to use old chart paper (from the bridge!) for making gaskets, or joints as we called them, especially on centrifugal pumps.  The joints, smeared in a thin coating of grease which helped when disassembling the parts, worked brilliantly.  They are about 0.008" thichness.  I guess a decent quality ink jet A4 printer paper 80gms, I say decent quality as some good papers seem slightly thicker and smoother, as opposed to the bog standard cheap crap A4 printer paper one (ie me) usually buys, would work well for you in this instance too and would probably be about 0.005-6" thick max.  They work very well, I've not seen them leak, and they are cheap and readily available, and saves having to buy in Teflon or PTFE sheet! 

Just a suggestion!

Chris
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 22, 2021, 11:59:44 PM
Thanks for the tip. I've heard of gasket solutions like that. Even made from (ideally lowest) currency bills which are tough linen & cotton.

I found this stuff on Amazon, quick shipping &relatively inexpensive. I'm not even sure why its as popular & available as it is. Someone suggested easy release lining for baking sheets or something. None of these parts will see that kind of (oven) temperature. I was hoping it would seal obviously but be somewhat tough & replaceable with disassembly & thin as possible. My only beef with some of the gaskets I've encountered on RC engines is if they stick & hang up anywhere, they are sure to tear. Maybe its the bit of castor oil or long term storage just clamped together but something in the fuel recipe makes an effective adhesive. well, at least my shapes seem easy enough to make by hand & I can avoid a laser or vinyl cutter.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 23, 2021, 12:09:19 AM
PS any residual oil left in the crankcase after a run, will drain down into the lower cylinders. past the pistons and into the cylinder heads. There is a danger of a hydraulic lock if too much oil reaches the cylinder heads. It is normal practice to walk the engine through at least 2 complete revolutions (eight blades)  to clear the oil before appalling the starter

Good advice. On my inverted RC engines I disconnect fuel, remove the plug & rotate prop around many times to drain anything that shouldn't be there for that exact reason. Or particularly if it didn't start right away & there was any chance of fuel flooding.

I could probably look it up, but do you happen to know if your Seidel radial has openings to the gears/cams for induction mist lubrication like the other engines I've shown?
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Admiral_dk on January 23, 2021, 10:24:48 AM
OS uses a nice circulation system without any pump in their four strokes. It works with the oil that pases the piston ring and ends up in the crankcase. Some of it is hit by the crank and lubes the bottom end and piston pin(s). As it has a positive pressure in the crankcase, the oil is pushed out into the bearings and to the cam gears and shaft. From there it goes up the push rod tubes and lubes the rockers, axle and valves.
And now to the really smart detail - there is a very small diameter short length hole from this cavity to the inlet port, where there is a negative pressure -> the oil is sucket back into the combustion chamber - repeat (as some is burned - you need some in the fuel too).
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 23, 2021, 06:20:33 PM
Re the OS 4S, I kind of figured that must be how it works on majority of RC 4S engines because they all have tubes enclosing the push rods & silicone O-ring type seals on both ends of the tubes. When I've dissassebled them the rocker assembly is completely oily looking.The valve cover usually has a gasket, so you know lubrication is working to the extent they don't want it to leak out.

The O5/O9 has pushrod tubes as well but... its another one of those things I'm scratching my head a bit now that I'm getting into it. The tappet bushing is kind of a conical external shape, presumably so the tube can rest on it at a 3D angle (maybe with a bit of mitering). Where it gets interesting is the rocker perch end. Now the receiving tube hole has to be at a funky 3D angle because the inlet & exhaust pushrods are at different angles based on the forward/aft positions of cam plates. Then he has a lateral set screw through the perch base that indexes into the tube. I'm no expert but it looks fiddly to me. 

Then when I look at the the shop made radials like Edwards & Jung, they all have exposed pushrods, no tubes at all. So are the rockers getting sufficient lubrication from valve/cage blow by or is an occasional manual drip before running all thats required? I'd like cover tubes & I've spent some time looking at the motion geometry. Its yet another kick-the-can-down-the-road theme, but my plan is to drill oversize holes in the rocker perch & then figure out some kind of rubbery fitting that will both capture the tube & seal it a bit. I've had a little bit of experience making rubbery-like urethane or silicone parts from aluminum molds. These are pretty teeny. But I'm getting ahead of myself.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: dieselpilot on January 23, 2021, 10:23:11 PM
OS uses a nice circulation system without any pump in their four strokes.

Some OS engines used one form or another for a very long time. FS-120 Surpass since the 80's. SurpassII versions of FS70 and 91 also used it (case vented to intake manifold).  The most recent iteration you describe above was used in the first Alpha series (https://www.os-engines.co.jp/english/line_up/fsalpha56/index.htm) which added passages by the cam followers (only low volume car versions of FS-26S-C and 40 had this prior) and the hole to the intake in the head. They have reverted to a normal case vent in the II versions of FSa-56 and 72. In the real world, with overly rich needle setting, excessive oil in the fuel, inverted installations, that system caused inconsistent running in the smaller engines due to randomly pulling rather large volumes of oil when orientation promoted it. I have added this system to several engines and never noticed unusual behavior, but I don't run typical fuels or oil ratios. OS rarely used gaskets.

Some complained about rusty bearings due to the closed case. I ran mine up, got them hot and let it idle for a while prior to shutdown. Some people like to push after run oil into the breather vent, and this wasn't possible with the closed system. There was one I left on the test bench for a week and ended up with bad bearings.

Exposed rockers need regular oiling, just like full scale. Even enclosed valve train can end up quite dry in RC four strokes. Varies with type of oil, how hot it runs, fits of parts, though most seem get oil. Valvetrain doesn't need much being properly hardened. Until recently as mentioned above, rockers were lubed by want managed to squeeze by the followers and valve stems.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 23, 2021, 11:31:15 PM
Interesting, dieselpilot. I'm probably mistaken then about valve cover gasket being present. I cannot honestly recall which of my dads 'castor-bunged' engines I disassembled (there were so many haha). Thought it was an OS but like you say they have spanned many years. Looks like the newer OS 4S are no gasket. I might be confused with YS which was more familiar to me, but maybe that was related to the air box boost? Interesting the Saito gasoline (with premix oil) has gasket.

Maybe the silicone fittings at the ends of the pushrod tubes are more about fitting up the 3D angle geometry & withstanding vibration etc as opposed to sealing oil residue.

Also attached OS methanol snip regarding crankcase drain.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Art K on January 24, 2021, 03:29:24 AM
You got a bit ahead of me, had a busy evening yesterday. The small Kinner was a 1/6 scale. I did Talk to someone at the NAMES show in Detroit who built Jemma and said there were discrepancies and get in touch with him if I built that. Didn't get anywhere with that one either.
Art
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on January 24, 2021, 04:45:25 AM
Ya. This is just my own beginner opinion, but design discrepancies scare me. Especially if discovered late in the game. I'm sure all plans have the potential for boo-boos, its just to what degree. I get it, these creations originate from human minds. And many designs created in the absence of modern software to validate things. And we have to pick a project we enjoy & stay motivated through tough times. That's kind of how I landed on this engine for better or worse. I figure if I can build it & get running, I'll be in a better position on future projects. Happy to pay my dues following others with much more experience than me.

Just as an aside, I mentioned the Edwards (free plans) & Jung designs (purchase plans) were next in line on my list
https://www.cad-modelltechnik-jung.de/construction-plans-model-engines.html
Jung recently revamped his website & lots of links of running engines, which for me is a confidence builder

I like this link. Lots of construction pics & he had the kahunas to strap it in a model. Its not an gasoline/ignition like Jemma but 7 cylinders.
http://philsradial.blogspot.com/
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: dieselpilot on January 24, 2021, 12:52:21 PM
OS machining has been very nice for a very long time, so they don't use gaskets in the four strokes for the most part. YS on the other hand, operation depends on proper sealing. Another intersting note is that virtually all steel components of the better glow engines have been coated for rust for over a decade now.

Saito have a similar design with the pushrod covers. They use fairly thick gaskets at the perch to seal and a sleeve at the follower guide. https://www.horizonhobby.com/product/pushrod-cover-and-rubber-seal-2-ca/SAIG60R340.html

Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on February 10, 2021, 03:33:22 AM
Crankshaft Intro

The O5 crankshaft was turned from a bar of 1144 SP (stress proof) steel. This was the first time I've machined this material & I donít have much comparative experience to similar tougher alloys like 4xxx series, but I was pleased with the results. The material specs are: 83% machinability (1212 reference = 100%), 132 ksi tensile, 100 ksi yield, 27 RC hardness. It turns & finishes well with my offshore carbide inserts. But the important claim to fame by other engine modelers is that itís less prone post machining stress relief distortion on parts like crankshafts with irregular geometry.

The crankshaft is solid, by that I mean the counterweight profile and crankpin are cut from the same stock (as opposed to a built-up crankshaft with separate components). While probably stronger, a one piece also means quite a lot of waste material removal to get down to the much smaller shaft OD area.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on February 10, 2021, 03:36:49 AM
Rough turning was relatively straightforward, I just took it easy for the most part. It was around this time that my complaining lathe threw in the towel, even with moderate DOC. The clutch started rattling (disengaging), the finish was progressively crappier & I could feel this was more serious. So, reluctantly I had no other option but to remove the stock before the critical finishing stage & deal with the lathe.

The repair was a long, drawn out process. I wonít go into details but some of the story is documented here. https://www.homemodelenginemachinist.com/threads/14x40-lathe-power-feed-improvement.27629/#post-318716
The problem likely originated on the factory floor Ė somewhat flaky design, skewed power feed rod & misaligned related driveline components. I hope I donít have to repeat this anytime soon, but the upside is that itís never run better & I have a deeper understanding of my machine.

The rear end stock was held in 3-jaw and front end in live center. With the rough turning complete, it was critical dimensions time. There are 4 bearing races and a spur gear which are slip fit on various OD sections. In retrospect this was my first real go at having to produce ODís within a couple tenths and simultaneously with good finish. My lapping methodology was kind of crude, & learn as you go, but eventually the job got done. It is important to let the part heat stabilize to room temp after turning because that can easily trick the OD measurement. Something I would now do when it comes to bearing fits on a CS or part with a lot of time invested is turn or utilize a dummy gage pin to establish the bearing fit beforehand, then use the same (quality) micrometer to translate that dimension to your part as you transition from turning to finishing or lapping. The last of the turning related operations were completed Ė groove for retaining ring and (hand) threading for the spinner nut. The part was removed from the lathe & band sawed to rough length.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on February 10, 2021, 03:39:15 AM
Crankpin Roughing
I decided to rough most of the excess material in the mill leaving a remaining square of crank pin material for finish turning in the lathe. This setup also allowed me to make a center drill mark to the exact crankpin throw radius and also drill/tap the 2 holes for the added counterweight slug fasteners.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on February 10, 2021, 03:45:27 AM
Crankpin Turning
Next I made an aluminum holding fixture that was a close sliding fit over the finished shaft OD. It has 2 through holes to match the counterweight tapped holes. It also has a milled flat on one side parallel to the bolt hole line, a reference surface for later. This fixture provided something for the chuck to grip & the bolts acted as kind of dog to transfer rotation. The crankpin center was dialed in with a DTI against a pointer rod extending from the tailstock. With setup established, the crankpin was turned down to diameter as well as the rear face of the counterweight profile and a thin boss profile for the master rod bushing. I tried a different style of lapping tool which was kind of a squeeze clamp affair.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on February 10, 2021, 03:48:56 AM
Counterweight Profiling
Back to the mill. With the holding fixture still on & reference surface presented to the vise, the counterweight profile was cut out. Then the roundover profile was milled & hand filed away using a slip on guide bushing.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on February 10, 2021, 03:51:37 AM
Crankshaft Counterweight
The design calls for an additional counterweight mass which is bolted to the matching crankshaft profile. One of those 5 minute jobs that took 3 hours. It has a relief arc cut to accommodate the master rod, but its center occurs at a different center than the OD, so required 2nd setup in the 4 jaw. I integrated that registration point in the same fixture used to hold the crankshaft for crank pin turning. Brass face mills really nice with the sharp uncoated inserts used on aluminum.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on February 10, 2021, 03:54:53 AM
Some partial assembly at this point
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Admiral_dk on February 10, 2021, 11:23:33 AM
Congratulations on a very important part made, to a high degree of accuracy  :ThumbsUp:

I do not see what holds the gear for the camshaft i place - key or ?

Best wishes

Per
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on February 11, 2021, 01:12:47 AM
Hi Per. The designer recommends high strength retaining fluid (Loctite) for the gears. So the spur gear ID on the crankshaft OD (where there is very little hub meat left for a key anyways). The ring gear OD on the cam plate part. And the face to face mate surface between the 2 idler gears. I'm a little concerned by the last one. I may silver solder those. But holding off until it comes to clocking the timing. I'll determine which are the better gears to lock & which can be allowed to move into position.

I was a bit apprehensive about 'glue' but I've also seen many example where cam lobes & such were attached this way. I actually don't know what kind of forces are involved on the planetary gears, their sole purpose is to lift the valve rockers against spring pressure.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 02:57:19 AM
Sorry for the long lapse again. I will now continue on with the cam drive assembly. The O5 is similar to other radial engine layouts where the crankshaft drives a planetary gear reduction assembly, the output of which is connected to two separate cam plates. One plate is dedicated to intake, the other to exhaust where cylindrical cam lifters ride along the cam profile. As the cam lobe raises the lifter, the connected pushrod act on the rocker arms to open the valves.

The O5 planetary gear is a 4:1 reduction ratio. A 15-tooth module-1 crankshaft gear drives a 15-tooth intermediary gear which is sandwiched against a 10-tooth gear, which drives a 40-tooth internal (ring) gear. The intermediary 15/10 tooth gear cluster rotate together on an idler shaft. Because of 4:1 ratio, each cam plate has 2 identical lobes 180-deg apart for 2 corresponding events per single cam revolution. The intake & exhaust cam plates are phased angularly to each to achieve timing relative to TDC. Both plates are attached to a cup which contains the ring gear. Here are some overview sketches. Hopefully this will make more sense as the parts & assembly are shown in real life.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 03:00:15 AM
The gear plate is made from 2024 aluminum. It houses one of the 4 crankshaft bearings on the rear side & also holds the idler gear shaft on the front, nose case side. The plate attaches flush to the crankcase front face retained with M3 screws & also snugly fits the crankcase ID with a matching boss. The plans called for 1.5mm OD O-ring seal on the internal boss & another on the lip OD to seal the nose case.

I mentioned earlier that the original O5 design called for the nose case chamber to be partially filled with oil to splash lubricate the gear & cam assembly. The O-rings are to seal this bath oil from the crankcase & the outside world. But I was becoming less comfortable with potential oil migration issues & dragged my feet on this matter for as long as possible. For example, even though the rear bearing was presumably left shielded I thought oil would eventually get in behind the shield, dilute the grease & ultimately leak into the crankcase. Then the risk becomes hydraulic lock on lower cylinders. Also, because the lower cam lifter bushings would always be submerged in oil, it seemed like another potential migration path out.

So, after a lot of deliberation, I finally decided to abandon the oil bath mode. Rather, I made a series of modifications to my existing parts & this gear plate was one of them. Therefore, you will see a mashup of old & new pictures, hopefully itís not too confusing. I decided to subsequently drill an array of passage holes in the front plate to allow intake mist charge originating from the rear via the carb & crankcase, into the nose case & lubricate the gears & cams that way. This is actually the established lubrication method of other commercial & shop made radial methanol glow engines, so hopefully will prove to be the right decision. For added insurance I will make a threaded/capped port hole on the nose case to squirt lubrication oil in prior to running. I'll be careful during break-in runs to see how wet things are. The O-rings are already done & will still serve their intended purpose.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 03:03:36 AM
The basic gear plate profile was turned from solid bar. The main diameters & bearing counterbore were done in one setting. The O-ring groove dimensions also need to be done at this point before removing the part. The grooves were a bit fiddly to obtain the right fit to the matching components. Iíve seen some O-ring groove formulas that get you pretty close, but in the end, it was a progressive trial & error thing. I used 70 durometer Viton O-ring cord & spliced a custom ring using CA glue. That part went amazingly well. If you ever need oddball O-ring diameters to make, I can recommend this as a cost-effective alternative.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 03:06:32 AM
Pictures showing the stock gear plate design confirming fit to crankcase.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 03:08:22 AM
Once the plate was machined, it was set up in rotary table for hole drilling. I trusted the CAD pitch circle calculation to drill & ream the idler shaft hole using mill DRO.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 03:10:09 AM
Then I made an MDF fixture to hold the plate, return to lathe & counterbore the relief for idler bearing spur gear.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 03:12:31 AM
Here are some pictures of the subsequent plate modifications to drill the array of oil mist holes. Of course, that required a new fixture to reestablish the geometry which would have been SO much easier the first go-round. I managed to get the 2 lower apertures slightly intersecting the gear cluster so hoping it will get directly misted.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Admiral_dk on October 11, 2021, 11:51:14 AM
I think that there is a very good chance that you will be very happy with you desicion to use mist lubrication  :cheers:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 05:15:59 PM
I purchased the steel module-1 spur gears from Maedler, the same company I got the internal gear from https://www.maedler.de/
Originally, I contemplated making the spur gears myself. But these were reasonably priced, high quality & each gear requires quite a bit of modification. At my snailís pace construction, this was probably a good decision in hindsight. 

For the crankshaft gear, I first machined a closefitting aluminum pot chuck in the lathe. Then swabbed the ID surface with acetone. Then without disturbing this setting, inserted the gear blank which was as a tight push fit on the teeth & back face. Checked the bore with a DTI, all good. Then I spotted some CA in glue among the teeth to prevent it rotating loose & a spritz of kicker. Then bored out the ID to fit the crankshaft diameter & faced/profiled to length. The steel was reasonably hard but machined well. The glue held things firm, even during interrupted tooth cuts.

Once the assembly was removed, my plan was to heat the assembly with light torch heat, expand the aluminum more, break down the glue & gear would drop out. It put up a bit more resistance than I expected but eventually parted ways with slight persuasion from a rod. The crankshaft OD was just a hair over diameter near the rear stop so a bit of lapping compound got the two-parts fitting snug. The gear will be permanently bonded with Loctite retainer.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 05:24:04 PM
The 15T idler gear blank was held in a 5C collet for opening up the bore & machining to length. The 10T gear was positioned on an axle fixture to turn down a portion of the gear which then fits inside the 15T bore. The inner 10T gear bore rides on an idler shaft. The gear cluster will be bonded together with Loctite retainer.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 11, 2021, 05:28:38 PM
The gear idler shaft is made from 5mm O1 tool steel. The end has a M2.5 threaded hole for flathead screw that retains a brass end washer in position. Including some pictures of one of my (many) lapping trials. My experience with drill rod is that is always within the stated tolerance, but is often eccentric in cross section. So, the purpose of lapping here is to bring it to size with appropriate finish, but also make it circular section. Here I have a steel clamp with a thumb screw tightening nut. It holds a sacrificial aluminum lap, slit through & also some internal relief slots made with a jeweler blade in scroll saw. I have a selection of inexpensive (AliExpress/Ebay) diamond lapping compound of graduated grits. The method worked reasonably well. But I have subsequently come up with an easier, less messy tool which is now my go-to method. Iíll show that tool a bit later.

After lapping & parting off, I torch heated & oil quenched. Then into the toaster oven to tan brown. I discovered it is sufficiently hard because I discovered the countersink was a teeny bit shallow & had to grind it bit to deepen, because my HSS tool just rubbed it. All good, everything seems to run smooth.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 13, 2021, 04:35:08 AM
Cam Plates. I only have limited hardening experience with O1 tool steel & that was confined to relatively simple parts using a torch. I donít have heat treating equipment, but I discovered a local fellow who does heat treating for knifemaker community. He has all the appropriate equipment & experience with the many flavors of air quench blade steels. Considering the work that would go into producing the cams & the form factor, I had visions of it distorting into a Pringle chip, or cracking across the internal holes. I figured successfully heat-treating knife blades would present a tougher challenge than my cam plates. So, I sourced the (Starrett brand) A2 from my local KBC dealer, choosing a bit thicker Imperial stock which had to be thinned to prescribed metric dimensions.

I made a simple aluminum fixture puck for the lathe with 2 threaded holes. After a facing the puck face true, the A2 stock was mounted with matching screw holes & brought to thickness. The ID was rough bored with annular cutter then finished with boring bar.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 13, 2021, 04:37:57 AM
The cam outline was band sawed roughly to outline but leaving 2 sacrificial ears with the original screw holes, which now served second duty to secure the part to the mill fixture. The ears correspond to where the cam lobes will occur. The lobe profiles are identical shape between intake & exhaust cams, but the four M3 mounting holes are angularly phased different to each other to achieve proper timing. One plate has M3 clearance holes, the other plate holes are threaded. Therefore, the cams donít lend themselves to be stacked together to make both intake/exhaust plates simultaneously.

The rotary table was first zeroed to the quill center. Then the fixture assembly was positioned concentrically on the ID hole with DTI & also along an edge of rectangular jig plate. Now the M3 holes could be drilled as well as the array of larger holes. These holes were a bit of foresight on my part relating to the same possibility that mist lubrication might be in my future, because drilling these holes after the cams were hardened would be very difficult. So, I came up with a CAD pattern which I could also replicate on the ring gear cup which the plates mount to & this would allow mist lubrication to flow through from rear to front. I was a bit concerned these holes would be great places for the cam to crack during heat treating but it turned out OK. Actually, the plans called for larger holes & non-symmetric spacing so it was a bit of faith.

I used an endmill & rotary table to cut the main profile, which is the valve closed, non-action surface. Overall, it went according to plan. Just have to be careful about entering & exiting the cut accounting for RT direction & backlash. The lobe ramp profile shape was created by the radius defined by the EM diameter as per the plans.  You can see I have a small Sherline 4Ē RT clamped in my mill vise bolted to an intermediary plate held in my main 6Ē vise. I feel the RT was accurate enough but found myself doing light cuts because I could feel the cutting action on the handwheel. Next time I would use my larger RT which is a bit more solid.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 13, 2021, 04:39:58 AM
The cam part was released from the mill fixture & ears band sawed off. Now I could transfer to another lathe fixture, this time with a boss which fit the cam hole ID & retained with screws through the holes. Now I could turn the cam lobe OD which is the valve open segment. That just left a small radius to blend the ramp segment to the open segment which was done by hand. I didnít take a picture but basically, I blued the part, scribed a line using a radius gage tangent to both surfaces & filed it to shape. That left finishing the outer profile with rubber abrasive in a Dremel.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 13, 2021, 04:42:04 AM
Once the cams were finished, I shipped them to the heat treat person along with some sacrificial coupons. A few weeks later they arrived back by mail. He verified the hardness & came as you see here. There was negligible distortion. They fit the ring cup the same way. The bolt threads engaged nicely so I was happy.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 13, 2021, 04:45:24 AM
Some partial assembly pics
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Kim on October 13, 2021, 05:42:26 AM
Wow!  Very nice work Pertha! The cams look beautiful!  Did they just come back the nice black color?  Or is that the color of hardened A1?  Regardless,it looks great.

Kim
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 14, 2021, 03:17:25 AM
Thanks Kim, yes that's the way they came. I'm not quite sure how far the black actually penetrates. It doesn't scratch or buff off easily. I guess we'll see after running. I know he quenches A-steel blades between slabs of ground aluminum to quench & also help prevent distortion. My memory is foggy now but he also mentioned salt bath. Would that be for the secondary tempering stage? I've been meaning to call him back because I will have some more parts to do. Unfortunately timing didn't work out for a shop tour, I would have liked to see it.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 14, 2021, 03:21:08 AM
The 40-tooth module-1 steel ring gear blank I purchased needed to be reduced in diameter & also in thickness. I purchased 2 gears just in case, but managed to get it completed on the first try. I first made a lathe fixture with a shoulder boss sized to tightly fit the tooth crowns. With this boss feature turned, the gear was positioned to preserve concentricity. It was held with a CA glue on the fixture back face & a clamp plate sandwiching the gear to the fixture with a cap screw. It held sufficiently tight & the material machined quite nicely. I was able to turn the OD to size by eventually cutting both the gear & fixture cap until there was some remnant gears to trim off. Maybe there was a better machining sequence to accomplish this, but the end result doesnít leave much of a gear one way or another. It worked out in the end
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 14, 2021, 03:24:25 AM
The ring gear cup is made from 2024 aluminum. It is supported on the crankshaft with the 2 smaller intermediary bearings. Once the timing is set, the ring gear is permanently bonded to the inside cup lip with Loctite. The cup has 4 countersunk holes for the M3 flathead screws to secure the cam plates. The cup was subsequently drilled with lubrication mist passage holes that match the holes in the cam plates so that lubrication mist can frow from crankcase into nose case & hopefully wetting everything in itís path with oil film. Aside from careful turning to match all the fit tolerances, it was pretty straightforward machining.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 14, 2021, 03:28:05 AM
Ring gear cup machining.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 14, 2021, 03:31:36 AM
Subsequent modifications to add mist passage holes.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Admiral_dk on October 14, 2021, 11:52:56 AM
More beuatiful parts and nice description of the proces of making them  :ThumbsUp:

I got one question though - as you can't move the cams nor the rest of the gears - did you use a slow setting Loctite, so you can keep on 'turning the assembly until you are happy with the timing ?
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: 90LX_Notch on October 15, 2021, 01:01:07 AM
Excellent work.

-Bob
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Mike R on October 15, 2021, 03:23:05 AM
Nice work, I always follow along on radial builds!
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 15, 2021, 05:45:02 AM
I got one question though - as you can't move the cams nor the rest of the gears - did you use a slow setting Loctite, so you can keep on 'turning the assembly until you are happy with the timing ?

Thanks for the compliment. I haven't timed the engine yet, that part is coming, hopefully before hell freezes over LoL. The plan is to fix the crankshaft gear and also fix the idler gear cluster together face to face. That secures that relationship & leaves the remaining ring gear OD temporarily able to slide within the ring cup ID, thus cam plate pair can rotate independent of the crankshaft in this setup mode. But since the cams are bolted together through the cup, they cant vary between each other. I will make an arbitrary witness line across both ring gear & cup edge. The business end of the engine and one cylinder stack are temporarily assembled. Then an indicator probe  in the glow plug hole to identify TDC. The target cam position occurs when intake & exhaust are mid way of their 20-deg overlap relative to TDC. So comparing this actual event point (indicated by valve lift) will reveal how far out it is in CS degrees. Divide by 4 equals how much to rotationally adjust the ring gear relative to cup using the witness line as reference guide. Hopefully converge after a few iterations. Once convinced, make a suitable sacrifice to the engine Gods & glue the ring gear in this position & mark the intersecting teeth. At least this is my plan, reality may have something different to say.

I'll have more to say about timing in a few posts. I was curious to figure out what the exact resultant engine time actually was & how that compared to other engines. The plans didn't specify this. I mean intake/exhaust open/close relative to TDC, BDC etc.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Roger B on October 15, 2021, 08:46:04 AM
Looking good  :praise2:  :praise2:  :wine1:

I have a similar set of Chinese diamond lapping pastes  :)
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 18, 2021, 10:37:53 PM
Before leaving the construction aspect of gears & cams for now, this might be a good opportunity to discuss the engine timing. The O5 plans provide all the necessary dimensional information to construct the cam drive train, but the specification sheet did not express inlet/exhaust timing in terms relative to piston TDC/BDC. Iím not sure why some engine designers omit this information, but it is what it is. The instructions are also somewhat Ďabbreviatedí in terms of how to set the timing. Translation from another language probably doesnít help matters. So, I wanted a firmer grasp of this stuff & also understand how the O5 timing compares to other 4-stroke (methanol/glow) model engines. Not that I felt qualified to modify it, but more for the sake of interest & future projects as well.

What follows is not intended as a detailed How-To. More of an overview of how I stumbled my way through this timing aspect, which is kind of a reverse engineering process starting with the parts drawings & references. Hopefully this will be of value to others.

First, one needs to know the gear ratio between the crankshaft (CS) & cam plate. As mentioned, the O5 planetary gear ratio is 4:1 which comes as a result of each gear-to-gear tooth count in the train from CS to idler cluster to ring gear. The rotational direction is also important. The O5 cams rotate in the opposite direction of the CS as shown by the sketch looking at the engine from the front. 
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 18, 2021, 10:38:53 PM
One needs to understand the intake & exhaust cams relative to each like a sub-assembly. The exhaust cam is to the front, intake to the rear, specifically orientated to one another with index bolt holes. Each cam pushes on its own dedicated lifter & respective pushrod / valve rocker. It is also important to be aware of the lifter geometry relative to the overall assembly. The sketch shows the O5 lifter action (red lines) extending radially from the CS center. Therefore, the cam contacts are occurring at different clock positions relative to the cylinder engine datum. This is important because other radials may orient their lifters differently. For example, if the lifter axis were coincident to the cylinder center (purple line) then the inlet/exhaust timing relative to TDC/BDC would be different on the exact same cam plate, all other things equal.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 18, 2021, 10:39:36 PM
This sketch is a bit busy, but shows how I then superimposed the lifter reference lines on the cam assembly. Then I determined the corresponding rotation angles marking the beginning & end of each lobe event which correspond to intake open, intake close, exhaust open, exhaust close.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 18, 2021, 10:40:34 PM
These numerical values were input into a homebrew spreadsheet from which I could calculate timing metrics in more familiar terms relative to TDC & BDC. I also determined valve overlap, lobe separation angle & made a plot to better visualize things.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 18, 2021, 10:42:32 PM
(Note, I posted a variation of this information elsewhere on the forum, so if it looks familiar, that's why)

I recently found this website which is an excellent resource for model engines http://sceptreflight.com/
What is particularly useful is the library of past engine review articles from magazines & other sources back in the day. Some reviews were very detailed. They disassembled, measured & photographed parts & assemblies & bench tested engines to provide useful power & rpm information. So just for the sake of a gut check comparison to my radial, I limited the data extraction to O.S. 4-stroke engines, although other brands are also represented. O.S. are generally considered to be reliable, powerful sport engines & encompass a wide range of displacements & layoutís including multi-cylinders. Of course, many design factors influence resultant engine timing which is outside the scope of this post. I have also been adding a few engines of interest here & there so donít read too much into the individual data points. Itís kind of a work in progress. You can see the O5 timing as it relates to other engines. The overlap is relatively narrow & (I think) the values suggest conservative timing, but Iíll leave that for you to decide.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 18, 2021, 10:43:22 PM
Also, because there have been a few builds of the Edwards 5-cylinder engine posted on the forum & the two engines are similar in many respects, I did a timing plot overlay for comparison. If anyone spots any errors along the way, please let me know.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 21, 2021, 05:17:10 AM
The nose case was machined from a round of 6061-T6 aluminum. I canít recall if I chose incorrectly from my intention to use 2024 or it was my subconscious saying Ďodds favor a mess up somewhere along the wayí. I decided to machine the outside profile first, then flip the part around to do the inside surfaces. This seemed like a better way to grip the part for ID hogging & hopefully concentricity on internal features.

The front was first drilled for the crankshaft clearance. Then a recess feature counterbored for the front bearing, which is a light press fit. The section profile contour was defined in the plans by various blended radii. I generated a series of corresponding X,Y intercept dimensions in a shop drawing. I cut these stepover terraces with a parting tool & blued the surface. Then finished the surface with file & sandpaper until the blue was gone & finished off with a 3M pad. I left the part this way in the chuck & transferred to bandsaw vise where it was lopped off.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 21, 2021, 05:20:24 AM
The plans had some internal pocket relief (milling) features & contouring around the lifter area which I stared at for a long time. It looked very nice & it yielded a slightly thinner case section in certain areas. But to my eye actually seemed a bit thin around the front mounting bolt head recesses. So, I opted to modify the section profile a bit so that all the internal surfaces could be done in the lathe in one setting as a series of steps. This provided a bit more meat around the bolt heads, but same annular thickness around the bushing radial holes. It cost some grams of aluminum which I didnít really care about anyways but erred on the side of bit more strength since it was 6061 & not 2024. I also wasnít entirely clear about how the pushrod tubes were being retained on the conical lifter bushings, but trusted the plans for now.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 21, 2021, 05:22:54 AM
Next step was to chuck the part for the rear side internal cavity work. A spacer was positioned between the chuck face & nose as a mechanical stop. I wrapped some tape on the OD surface to protect it from jaw bite. The DTI said my 3-jaw was accurate, but in instances where required, an extra layer of tape under a jaw allows you to micro-shim. In hindsight the 4-jaw chuck would have been a better choice on 2 counts. You can dial it in exactly & also it provides one more gripping surface. This can be an issue on thin-walled parts where high initial gronk when the part is solid can result in slight deviations when the internal surface is machined out. Another thing I have subsequently learned is that not all tape adhesives play well with cutting fluids. They can dissolve, become unglued & I suppose risk the jaw grip.
I now favor an aluminum tape for protection applications like this. It also works well in shimming applications where its preferrable to pre-attach the material. I think this tape is used for furnace duct work.

So, after some material hogging, I just had to be careful as I approached the ID lip surface which becomes quite thin & must fit the gear plate OD properly c/w with its O-ring in place. Itís important to let the part cool to room temperature & take spring passes at different feed settings.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 21, 2021, 05:24:35 AM
Some interim assembly testing pictures
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 21, 2021, 05:27:07 AM
Next step was to make a fixture to hold the nose case by the ID lip so that the part could be gripped in a rotary table. It has a threaded hole for a retention stud. After some trial fit-ups that were a bit too tight & concerning moments where the parts were firmly stuck, I put a smear of anti-seize on the surface.

The fixture/part assembly was gripped in a RT & 4-jaw chuck & 5 bolt holes drilled & counterbored. Now the RT was flipped upright. I used a parallel & DTI to register what is equivalent to horizontal reference off 2 bolt holes & then proceeded to drill & recess the holes for the lifter bushings. These are offset on either side of center nose case center & also offset fore & aft corresponding to the respective cam plates positions.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: bent on October 21, 2021, 07:06:56 PM
Nice work Peter! :popcorn:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Craig DeShong on October 26, 2021, 03:26:54 AM
Hi Peter

Iíve been following along; your radial and my rotary share many similarities.  I especially enjoyed your discussion regarding the cam disks.

Your work is superb.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 27, 2021, 02:11:40 AM
Thanks for the kind words.

The lifters (or maybe they are called tappets, Iím never sure) are made from nominal 3mm O1 tool steel. The internal end is a dome shape which runs along the cam plate profile. The external end has a partial depth 2mm OD spherical socket seat which mates the ball ended pushrods. The lifters slide up & down within bronze valve guides. So, I made some test guides first so that the drilled & reamed bores could be used as guides for lapping the lifter stock OD.

The male dome profile was formed by a ball turner accessory. Then the part was flipped in the collet, trimmed to length & the female radius profile made with a ball end mill. These lifters were sent at the same time to the same heat treat guy who did the cams so I wanted to get the finish as good as possible now. The lifters would have been easy enough to heat treat with a torch to Ďsomeí level of hardness but I wanted them to be a few points softer than the resultant cam plate hardness so as to preferentially wear the (easier to replicate) lifters. I didnít trust my repurposed toaster oven to deliver accurate temperature for tempering. The male end was polished by gripping in my Dremel chuck & lightly running in a shallow well drilled in MDF wood with a smear of compound.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on October 27, 2021, 02:13:19 AM
The lifter guides are made from bronze as per plans. The turning profile is pretty straightforward. I used my 5C collet chuck & sharp, uncoated insert like I use on aluminum. The holes were drilled & reamed. Its interesting when you make a bunch of the same parts, you gain an appreciation for variation. Some lifters slid nicely in the guides as planned, others felt a bit scratchy on entry or exit. The bore looked good. Turns out my handheld hole chamfer gizmo was leaving a micro burr, so I used a small polishing point to dress the edge.

The lifter guides will eventually get bonded into counterbored holes in the crankcase with Loctite. The conical shape is intended to accommodate the ID of the pushrod cover tubes which meet the guides at a mild 3D angle relative to the lifter axis. At this point Iím not really crazy about the metal on metal contact & mitered end. I would prefer some kind of rubberized or silicone material between tube & cone or somehow making a union. The plans call for the tubes being retained in the rocker perch with a small lateral set screw. I have some hopefully better ideas to test but donít yet have a clear game plan. So, I have deferred this for now & maybe some divine inspiration will occur closer to final assembly. If I have to re-make the guides m, itís not a big deal.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Roger B on October 30, 2021, 07:18:37 AM
Looking good  :praise2: Radial engine cam rings and valve gear looks an interesting topic  :thinking:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 02:09:39 AM
I will discuss the cylinders next. Spoiler alert Ė in my case it wasnít quite a straightforward path making 5 cylinders, liners & heads as per drawings in batch mode. I first make some tester parts as per design to get an idea of what was in front of me. This highlighted a few issues where I thought some modifications might be a better way to go. But these 3 components in particular closely integrate with one another, so a design change to one part for whatever reason very likely has a direct knock-on effect to the other parts they mate. I guess we will ultimately see if my decisions were right, wrong or somewhere in between. Overall, I tried to stick to the critical dimensions.

So why the departure from the plans?  The cylinder head (to be discussed later) is really the most critical part to have nailed down first because it encompasses many features (read lots of invested machining time). The inlet & exhaust ports are comprised of a smaller diameter gas passage drilled through into the valve cage. And a larger ID counterbore segment, threaded for a steel screw-in fitting which retains the tubing into the head against the counterbore ledge. This threaded style is used in other model engines, including commercial RC engines. Because the port axis is orientated to the head at an oddball angle in top view, the threads of the retention fitting are not initially fully engaged the way they would be like a bolt enters a nut. They must first hook up to a portion of the head thread for a few turns before becoming fully engaged around the port ID. At that point, itís only a few more turns before the fitting bottoms out, sandwiching the tubing flared end to the counterbore step. No mention was made in the plans of a seal washer at the end of the pipe which I wanted to use particularly for induction pipe, but this would further reducing the engaged thread length. In other words, the design counterbore length is kind of short IMHO. To complicate matters, the heads also have a series of radial cooling fins cut through the port area which further reduces thread contact area. I figured with heat cycles & fuel mung & vibration, it might be asking a lot of these threads. I could select a finer pitch bottoming tap, but I was trying to avoid turning oddball metric threads in my imperial lathe for the matching fittings if possible. As it turns out, some imperial threads might be better candidates. This is a very longwinded way of saying that I really wanted the head to be slightly larger diameter to get more threaded meat in port area.

I modelled the new head in CAD. Everything looked good except aesthetically the head diameter was now extending over the original cylinder top diameter, not as pretty as when they were the same diameter. Iíve seen full size radial examples of both, but I preferred the original look & it solved other issues. So, I changed the cylinder crown diameter, which then meant a different taper angle to end up the same base skirt area dimensions. I also changed the cooling fin thickness & pattern to match my grooving inserts & a more nominal inch spacing pattern. The net change helped provide a bit of cylinder meat for what were shaping up to be slightly thicker liners. More on that later.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 02:12:51 AM
So, with a new plan in place, on with actual cylinder making. They start out as drops of 6061-T6. I rough drilled them 7/8" in a batch mode. Then each is chucked & machined with most all features to preserve the setup. A boring bar was used to open ID to ~0.005" undersize. Then a 1.0625" reamer passed through so the ID would all be consistent diameter & finish in preparation for the liners.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 02:15:37 AM
Next was the bring the crown and skirt flange to finish OD & turn the taper portion
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 02:17:19 AM
Next was cutting the cooling fin grooves. I used a 0.043" wide Nikcole insert. They cut like a dream, just keep a bit of cutting fluid on it. Some groove depths are different. The top 3 are a bit shallower to stay clear of the threaded head bolt holes. The next 3 are limited by maximum DOC of the insert ~0.220". Then the remainder grooves are one constant base diameter which then & matches the diameter occurring above the skirt flange. All the edges were lightly chamfered using one of those HSS triangular scraper tools & cleaned up with fine 3M pad. Then parted off.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 02:18:48 AM
I had one of those machinable expansion arbor blanks handy, so turned the main portion to match the cylinder ID with the bolt lightly engaged & also a raised step datum surface for the cylinder top to rest against. With the cylinder lightly gripped I could face the bottom flange & bring the cylinder to final length.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 02:20:50 AM
Next, I turned a spacer collar so the chuck jaws could grip the head portion, because at this point the skirt flange is a larger diameter. Using a rotary table, drill & tap the 5 x M3 holes for the head bolts. These holes were then utilized to attach a rectangular fixture plate. The assembly was held in a vise so the flange could be drilled for clearance bolt holes & milled to the rectangular profile. I have a choice to use SHCS, or threaded studs in the crankcase with topside nuts on the flange.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 02:22:13 AM
Partial assembly pics. BTW, the liners will extend through the cylinders bottoms and that portion is what mates the matching hole in the crankcase 
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Don1966 on November 01, 2021, 04:34:49 AM
Oh wow! A whole lot of things going on in this thread. Thatís a very interesting buildÖÖ. :Love:



Don
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Admiral_dk on November 01, 2021, 11:09:32 AM
So now we can see a 'Round Engine' appearing  :praise2:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Zephyrin on November 01, 2021, 11:17:30 AM
this is a great build, very informative, thanks to share this...

on the new design of the cylinder head, I wonder how the threaded fitting will be inserted, as the extremity of the pipe is enlarged in the head and bent in the other extremity, which may hinder the insertion of the threaded ring ?
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Craig DeShong on November 01, 2021, 01:20:17 PM
Great work.  :ThumbsUp:

Love the machinable expansion arbor blank, had never seen one used before.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 06:37:00 PM
on the new design of the cylinder head, I wonder how the threaded fitting will be inserted, as the extremity of the pipe is enlarged in the head and bent in the other extremity, which may hinder the insertion of the threaded ring ?

You will see some actual parts pretty soon as I continue to post pictures. But yes, it is a rather delicate balance of accommodating the flared or trumpet shaped tubing end inside the threaded port. Then the threaded fitting must be able to slide over the tubing bend radius. Therefore the fitting length + ID + chamfer must all be sized accordingly. Threaded ports seem straightforward just looking at them, but actually there are a few things going on behind the scenes. Personally I don't care for them much. Next engine I will do what it takes to have bolted flanged tubes. I spent quite bit of time in CAD to see if I could modify the existing design for this, but it got to be a deeper & deeper rabbit hole. Next engine I will mill the outer head profile in rotary table (as opposed to turn it round in the lathe) so that an extending boss for the port can be integrated. Then the fins would also have to be milled on a rotary table.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 01, 2021, 06:59:45 PM
Great work.  :ThumbsUp:
Love the machinable expansion arbor blank, had never seen one used before.

Thanks. I was lusting over some expanding ID collets but they are spendy. At least in 5C which i would prefer because I have a set-tru chuck. Other systems you are relying on runout or need to chuck in 4J to dial in. (I'm talking hardened non-machinable collets here of course). The nice thing about the pre-slit blanks is they are turned in-situ prior to mounting work so should be very close to concentric. I have since made a few blanks with a single slit just to see if they can be replicated in the home shop less expensively. They work 'ok'. Ideally they should be turned quite close to ID because a single slit requires more screw torque to open the beak. Maybe a better plan is drill a larger hole traversing the end of the slit. The commercial one is steel with more slits. Theoretically you can keep turning it down for successively smaller jobs.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: crueby on November 01, 2021, 07:03:41 PM
I've made several expanding arbors, drilled/tapped for the screw, counterbored and tapered slightly the end of the hole for the screw head (which was also tapered). Sawed in two slots 90 from each other so it expands out better. Works quite well, used that setup for eccentric followers and such. As you say, you want the OD turned to a close fit on the bore of the part you are holding.
 :popcorn: :popcorn: :popcorn:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: bent on November 02, 2021, 08:01:08 PM
Neat work. :popcorn:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Roger B on November 02, 2021, 08:07:01 PM
Looking good  :) :) :) there's a lot of work in those pieces  :praise2:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: 90LX_Notch on November 02, 2021, 10:37:08 PM
Itís coming along very nicely petertha.  Iím really starting to think that I need to build a radial someday. 

-Bob
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: bent on November 03, 2021, 03:45:58 PM
With all the radials and rotaries being built lately, I too have had the urge to make one.  Then I lie down for awhile, and the urge passes.  :Lol:
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 10:56:55 PM
Next up are the liners. I should mention upfront that the path I took detoured a bit as things progressed, so the pictures might seem a bit out of sequence without some elaboration. When the CI liners were lapped to final bore & heat shrunk into the aluminum cylinders, the cylinders squeezed back under cooling. The bores reduced to the extent that they needed to be lapped all over again to return them to target dimension. I figured any shrinkage would be quite small, like within a few tenths, thus only requiring a quick lapping correction tweak. But they reduced more like 0.0005-0.0015Ē & also non-linearly down length of liner. Likely a function of the cylinderís tapered shape squeezing it differently on the top vs. bottom of liner. Anyways the bottom line is my careful bore finishing work before mating into the cylinders kind of went out the window. I could have opted for something more like a slip fit, but I started to read articles suggesting some liner interference is required to achieve proper heat transfer. And as the engine warms up under running condition, a sliding fit will only get looser yet as the aluminum cylinder expands more than CI liner.

My initial workflow was to first establish the bores of the aluminum cylinders to a consistent diameter & finish, which was brought about by a reamer. It was an imperial size next closest to the nominal metric size specified on the plans. I was already modifying the cylinder barrels as mentioned earlier, so this change was incorporated. This resulted in a slightly thicker liner wall which I thought was fine, maybe even desirable. With the cylinder ID established, I would finish the liner OD to whatever dimension was required for the correct slight interference fit. The interference amount was driven by being able to place the mated liner/cylinder assembly into an oven at moderate soak temperature so that they would release from one another based on the different thermal expansion of the two materials. Iíve done this operation many times on RC engines with my small toaster oven to replace liners.

But let me back up a step. This is my first engine & I was intimidated by making good quality piston rings. This topic has been beaten to death in many other posts, so letís just say I found myself at the same fork in the road I suspect others have arrived. I was aware of the Trimble ring method documented in Strictly IC magazine. There are also some excellent build posts on this forum where others followed Trimbleís procedures with great results. I find Terry Mayhughís (Mayhugh1) build posts on the other forum to be particularly informative. Making the ring fixtures represents some work, but didnít seem too onerous. But I didnít have access to heat treating equipment or related experience which seemed pretty important to success. I wanted this engine to run & rings are crucial to success. So, to my thinking, there are 2 main paths:

(A) Bring all liner bores to Ďwhateverí diameter they arrive at, as long as each are identical to one another & appropriate final finish. Using that resultant measured bore as an input value, all of the dimensions to make the ring blanks & heat set fixtures can be determined using Trimbleís equations. The advantage here is that all the liners can proceed along together somewhat as a group. They receive the same tool setup treatment one after another, especially up to the latter stage of finishing where it counts most.

(B) Purchase commercial rings, assuming they can be reliably sourced. This solves the ring making issue. But you need to make the bores exactly the same as the liners they were intended to run in. The O5 is a nominal 24mm bore which happens to be the same as an OS-56 4 stroke engine. Therefore, it seemed like a good idea at the time in my case to purchase 5 rings, including spares for unforeseen replacement. So, I somewhat naively, went down this path. Although it seems like a good plan, in reality itís actually more work & higher potential for mess up. At least for multi-cylinder engines where the count increases. The issue is the dimensional target Ė trying to stay within say 0.0001Ē bore target and simultaneously arriving at that target with the appropriate finish. If the bore is inadvertently exceeded for whatever reason, thatís kind of the end of the trail as it will no longer match the commercial ring. Next engine I will likely go the Trimble route.

When the rings arrived, I measured the cross section against the Trimble values & they were quite closely which is assuring. I also got a new OS-56 liner to closely examine for fit, finish & use as a dedicated glorified bore gage. And added a piston to obtaining corresponding dimensions like ring groove, crown & skirt ODís etc. to replicate for my pistons. Thus, the shopping list expanded but I figured I could sell the piston & liner as spares one day & recoup some costs. As of today, several years later, they are still sitting in my box. :/
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 10:58:15 PM
So, onto the liners. They start out as drops of 1.25" nominal diameter Class 40 grey cast iron bought from Speedy Metal in USA. They arrive ~1.35" OD I think so you arrive at the good stuff under the skin. Previous to the real liners I also made some testers out of 12L14 & 1144 Stressproof. The 12L14 finishes beautifully but I was a bit concerned about corrosion in methanol fuel environment. The Stressproof machined well, likely a bit stronger & probably a good choice too according to others experience. But sourcing the appropriate diameter was more difficult at the time & sadly 90% of material core ends up in the swarf bin. CI seems to have a reputable track record in conjunction with CI rings. Iím sure wear will be just fine for my occasional running. CI is relatively inexpensive & available in progressive sizes for expected mess ups, so CI it was!

I took a skim cut to get through the crust, faced the end, then pilot drilled 0.375Ē to 0.875. On my prior testers I experienced a bit of harmonic ringing & minor chatter which I assumed was because I turned the OD to size first & then the bore work. This time I reversed & did the boring first while there was more meat on the wall. Seems to have helped but could also be CI itself vs the prior steel alloys. I found I could hold dimensions quite well as long as one account for any heat buildup. CI is a bit messy so I cover the ways.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 10:59:42 PM
I used the thickest section boring bar with carbide insert & bored to 0.940Ē ID. This lands me with 0.005" left to remove for target 0.945" finish bore.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:01:35 PM
I rough turned the main OD slightly oversize, then did the upper liner features. The crown is an extended lip with an undercut so the liner registers onto the cylinder top deck. Then I used some homebrew sanding sticks made from 2" wide MDF boards with wet-o-dry paper bonded with 3M spray adhesive. I found this to be an expedient way to remove the turning grooves & work the material down to size in a controlled manner. The board width spans the entire liner length which helps correct & minimize undulations that can result from traversing a narrower abrasive belt strip back & forth because the dwell time & tension can be different across the length. For reference the OS-56 liner was within a tenth OD all along the surface.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:03:16 PM
The final 0.0010-0.0015" came off with a homebrew OD lapping tool of sorts. This was kind of an experimental venture driven by how much time it took me to achieve acceptable surfaces on my prior test liners. I hoped these generic lapping blanks could be utilized used for this job & future projects if they worked out. Commercial tools are available but they are expensive, especially in larger sizes.

The idea was to have some aluminum blanks cut with the radial pie segment slit pattern you see. Then they could be bored out to the requisite ID & either lap directly on the bored surface, or perhaps in conjunction with a sacrificial split lapping collar to get more utility out of the bore size, kind of like how a collet grips a part. I made a CAD drawing & send it to a waterjet outfit. They cut the slit profile including end holes leaving me to drill & tap for a cross screw for setting lap pressure. I tried different lapping compounds & settled on some cheapo oil based AliExpress diamond paste that comes in a syringe tube.

I guess I could say my lapping tool worked out OK in that any diameter undulations (hilltops) are worked down & the diameter can become quite consistent. But I find lapping to be messy business & best confined to removing small material thickness. It also requires a bit of hand technique like stroke & dwell time & re-charging the lapping goop & fiddling with the clamp tension. Then you have to clean everything spotless, measure at various spots down the length & go at it again. It all takes time. I left the last 0.0005" for 1000 & 1200 paper using my full width backing boards & in all honesty might be just as quick as lapping. Eventually I arrived there. Itís Interesting how CI can get a finish, eh?
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:04:34 PM
The skirt ID has a shallow chamfer to provide clearance for the rod motion. One last check of finish dimensions, lightly knock down any corner edges, then part off the liner. Then apply a single layer of protection tape, hold reversed in collet chuck & face the lip surface to final length.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:08:13 PM
Onto finishing the bores. A while back I acquired a Themac tool post grinder (TPG) grinder & played around with it on my previous test liners. I now have mixed feelings about TPGís. I suppose it suites this kind of application where relatively short length work sticks out of the headstock cantilever mode. Accurate surface dimension & finish combinations can be achieved with the right technique. If the work involves hardened materials, grinding may be the only way to go, but I donít consider CI to fall in this class. I also had hopes of using TPG for several other applications & thatís where some shortcomings & complications become apparent, especially if the project involves tailstock support. The TPG assembly just wants to occupy the same real estate as TS assembly which really is difficult to work around. I also had a tough time finding suitable wheels, meaning the right diameter & grit & composition combination. I ended up buying a surface grinder wheel from KBC & had a water jet cutter make me a bunch of wheel blanks. I was a bit apprehensive about them blowing up but so far so good. Dumore is another popular name. I canít speak for their wheel arbors but the Themac has an oddball taper that doesnít match any common taper, seems to be unique to them. Ultimately, I figured it out, but suffice to say making your own arbors is more work.

Most of the time you will see a TPG lathe setup where people pre-align the lathe compound at a shallow angle & finely increment cross travel depth that way. The magic trig number for convenience is 5.739 degrees compound angle (off of spindle axis) which yields the relationship of 0.001Ē increment on compound dial equates to 0.0001Ē of cross bed travel, times 2 equals 0.0002Ē in bore increment. Just remember that the same rule of removing backlash applies. And this is not exact because unlike a cutting tool, the wheel is slowly eroding in diameter as grinding proceeds. So, you have to measure & re-calibrate more so than other lathe operations.

My compound leadscrew is in pretty good shape. But when I secure the compound dovetail between each pass, the clamping action itself can drift the actual position a bit. Iíve made some improvements to the lock, but itís still there. So, I donít completely trust this setup on my machine although I do like the fine incremental feed aspect. Alternatively, I made a fixture to hold a tenthís reading dial gauge to bear against the end of the cross slide itself which directly measures Y infeed displacement that way. This removes both backlash & table lock issues simultaneously. A sensitive dial gage also acts as a sober indicator of machine vibration which is flowing through to the grinding wheel. The needle fluctuates on either side of the true reading. Ideally, deflection is low & somewhat dependent on where the indicator is mounted & how things are tightened down. I think the TPG is probably approaching the limits of my lathe rigidity & spindle bearing condition. If you donít have dovetail locks, my opinion is that TPG might be the wrong weapon of choice because once the motor winds up, the sliding surfaces can become Ďbuzzyí & prone to free floating, even with a good quality TPG. A suitable DRO can measure displacement independent of dials so long as you have the right resolution. But consider even typical 0.0005Ē step increment on DRO display represents 0.001Ē of bore gone. Thatís what made me a believer in a mounted analog indicator. So, after some trials I kind of considered the TPG as a Ďtruingí tool, not a finished bore tool. At least on my lathe & limited experience. That leaves the last thou or more for lapping but TPG is still a time saver. Whether this warrants the expense & setup of TPG is probably another discussion. So, who knows, it may get traded for a TIG welder one day which costs about as much & would see a lot more use in my shop, but thatís another story. What I REALLY need is a Sunnen hone LOL.

Back to liner grinding. I plugged off the back end of my collet chuck so grinding debris would not migrate in behind. I used a single wrap of tape on the liner OD for protection & gripped it in 5C collet chuck.
The wheel was dressed in-situ with a homebrew diamond tool holder. Cover the machine & use a vacuum for this operation please. Then it was a matter of selecting a low spindle RPM, power feed the TPG on low traverse setting & start opening the bore in small ~0.0005Ē bore increments. It is a somewhat satisfying experience to see partial geometry patches being removed under grinding, meaning non circular sections features you thought were quite true by a boring bar alone. The liner never got warm because of low DOC & more time measuring & futzing. I tried a fluid but t didn seem to be adding any value, the wheel looked clean at these removal rates. The bore finish was Ďokí not stunning. The geometry & roughness seemed acceptable but I think it exhibited skip or maybe secondary vibration. Iíve been told my grit selection was too fine, that actually coarser would be better. Grinding is a science in itself. But they popped off pretty quickly. I have been making 6 cylinders, 1 guinea pig & hopefully 5 keepers.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:09:08 PM
TPG grinding examples work in progress
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:10:18 PM
At this point I was ready to lap the liners using a brass Acro brand lapping tool and a tenths reading bore gauge. I used my OS-56 liner as a glorified bore gage setting tool.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:11:26 PM
Many hours later of mind-numbing work I had 6 liners to a nice matt finish & within a tenth. And all this was basically a warm up run.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:12:13 PM
Now we arrive at the nasty bit. I put a cylinder in the oven at 450F for a set time & dropped in an ambient liner with no drama. But as mentioned previously, once the assembly cooled, the bore had reduced differentially. About +0.0015Ē near the top & ~ 0.0005Ē near the skirt. So not only a significant bore diameter change, but the barrel walls were no longer parallel either. I returned the assembly to the oven & repeated what Iíd done a few times already on the tester; heat up & separate to evaluate what was going on. Well, this time even a light love tap after heating was not removing them. This always worked with my test cylinder.

When I carefully remeasured all the cylinders, I had more questions than answers. Maybe because the new cylinder design had more mass. Maybe the reaming was not quite as perfect as I imagined. Maybe the cylinders relaxed a little post-machining because I could measure as much as 0.0005Ē oval in spots. Or maybe there are micro undulations in the surfaces kind of acting like a screw thread where the mean distance between hill tops is correct, but the surface itself can act like a secondary grip once the shrink has occurred? I decided I wanted these parts separated to be utilized so had to resort to light torch heat. They finally let go. The liner came out a light tan color but amazingly neither seemed worse for wear. They had the same dimensions as when they started out.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:13:25 PM
At this point it was time to weigh my options. I already sunk some effort making the liner ODís nice & consistent between one another. But the interference just seemed a bit excessive now. It was obviously shrinking the bores quite a bit. Had the liner bores remained unfinished at this stage, it would be of no real consequence, I could have just carried on. I no longer saw much merit pursuing the ability to swap in a replacement liner at some later time because I had already decided to make a complete 6th cylinder assembly spare to just bolt on the crankcase if something bad happened.

I tried mounting my test liner to an offshore expanding arbor held between centers in the lathe to see how easy it would be to somehow lap off a thou in a controlled manner. Iím not sure if I received a Monday arbor but it did not turn concentrically. I put a dial on the OD & it had about 0.002Ē TIR. I didnít need more bad geometry problems so abandoned that idea. Glad I didnít buy a complete arbor set!

So, I bought another Acro brass lap barrel to slightly enlarge the cylinder ID, thus reducing the amount of liner interference & simultaneously tuning up the surface geometry & finish. Hopefully I could use the liners as they were & reduce the amount of subsequent bore correction once shrunk again. Kind of bass-akwards to the original plan but seemed like the best option. This worked quite well. I havenít lapped aluminum like this before with brass but it yielded a nice light matt finish & the bore gage said it was consistent down the length.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:14:40 PM
Some trial & error futzing, eventually I arrived at combination where the liners could be re-inserted & the bores were undersized in the 0.0005 Ė 0.0010Ē range.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 13, 2021, 11:15:31 PM
So once again, the liner bores were re-lapped to target ID, this time as a mated assembly. I will now call these good. I had the bright idea to submerge the assemblies in my ultrasonic cleaner again to remove trace lapping compound. But very shortly thereafter I noticed some corrosion stains starting to form on the liner surface, so I immediately pulled them out. Swabbing & rinsing with mineral spirits is a better way to go. Then a light coat of oil for storage.

Next engine I would leave the liner bores unfinished (undersized) at the boring bar stage. Some of the interference surface conditioning could probably be minimized, particularly if there was no need to pull & replace the liner. The cylinder assembly would now have to be jigged so that the grinding / lapping / honing operation could proceeded on the mated surfaces.
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Roger B on November 14, 2021, 07:43:58 AM
That was quite a journey  :ThumbsUp:  :praise2:  :wine1: I do like Acrolaps  :)  :)
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: Admiral_dk on November 14, 2021, 11:42:07 AM
Woa - that part of the journey ended up being a lot more winding than anticipated ....

So I hope that you are really satisfied with the result !!!
I think they all look good and should work very nicely on the finished engine.

Per
Title: Re: Ohrndorf 5 Cylinder Radial
Post by: petertha on November 14, 2021, 06:15:56 PM
A question came up on the other forum, so pasting reply as further elaboration if my saga verbiage was not quite clear.

I don't think there is an advantage to excessive interference, in fact several potential disadvantages. For example, in my case where the cylinder shape is tapered & thicker wall near the top can contribute to different shrink force on upper vs. lower liner. Pretty much every RC engine I have disassembled requires oven heat to install & remove the liner, even when brand new. My initial heat testing was based on a separate spare test cylinder which was the original design, not my subsequent modified design. But I think either reamed ID surfaces were not as consistent, or possibly they stress relieved a bit. In this kind of application, a half thou one way or another seems to make a big difference. My longwinded story was just to say in hindsight I would not bother grinding & lapping the liner bore until mated to cylinder & completely stabilized. Unless you have good shop methods to very tightly control both OD & ID dimensions & finishes. Jung provides these instructions in his 5-cylinder engine which is probably not far off how mine ended up after lapping the cylinder ID (0.02mm = 0.0008Ē).

To ensure optimum heat transfer, the cylinder liners must be shrunk into the cylinders. The inner diameter of the cylinder is about 0.02 mm smaller than the respective outer diameter of the liners to unscrew. After uniform heating of the aluminum cylinder by means of gas burner or hot plate (to about 200 į C), the cold liners are inserted into the cylinder.