Author Topic: Ohrndorf 5 Cylinder Radial  (Read 1718 times)

Offline petertha

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Ohrndorf 5 Cylinder Radial
« 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!

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #1 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

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #2 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #3 on: January 19, 2021, 02:27:47 AM »
Plans overview & video link


Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #4 on: January 19, 2021, 02:29:39 AM »
Cad pics missing pushrods, carb, inlet/exhaust accessories & some other bits
« Last Edit: January 19, 2021, 02:45:09 AM by petertha »

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #5 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.
« Last Edit: January 19, 2021, 02:42:21 AM by petertha »

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #6 on: January 19, 2021, 02:40:49 AM »
Pics of the prototype. If only I knew what was ahead of me LOL.

Offline Laurentic

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Re: Ohrndorf 5 Cylinder Radial
« Reply #7 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!
« Last Edit: January 19, 2021, 12:47:57 PM by Laurentic »

Offline Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #8 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:
It is the journey that matters, not the destination

Offline Mike R

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Re: Ohrndorf 5 Cylinder Radial
« Reply #9 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

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #10 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

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #11 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #12 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/
« Last Edit: January 20, 2021, 05:45:05 AM by petertha »

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #13 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.
« Last Edit: January 20, 2021, 05:46:32 AM by petertha »

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #14 on: January 20, 2021, 05:18:50 AM »
Crankcase

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #15 on: January 20, 2021, 05:20:48 AM »
CC cleaned up a bit, nearing completion

Offline Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #16 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:

It is the journey that matters, not the destination

Offline ozzie46

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Re: Ohrndorf 5 Cylinder Radial
« Reply #17 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

Offline Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #18 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
« Last Edit: January 20, 2021, 02:36:33 PM by Vixen »
It is the journey that matters, not the destination

Offline Roger B

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Re: Ohrndorf 5 Cylinder Radial
« Reply #19 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.
 
Best regards

Roger

Offline Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #20 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
It is the journey that matters, not the destination

Offline Roger B

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Re: Ohrndorf 5 Cylinder Radial
« Reply #21 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.
Best regards

Roger

Offline Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #22 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
It is the journey that matters, not the destination

Offline ozzie46

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Re: Ohrndorf 5 Cylinder Radial
« Reply #23 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

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #24 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.

Offline Admiral_dk

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Re: Ohrndorf 5 Cylinder Radial
« Reply #25 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

Offline Laurentic

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Re: Ohrndorf 5 Cylinder Radial
« Reply #26 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

Offline Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #27 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
It is the journey that matters, not the destination

Offline Laurentic

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Re: Ohrndorf 5 Cylinder Radial
« Reply #28 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

Offline Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #29 on: January 21, 2021, 04:20:22 PM »
 :ThumbsUp:
Mike
It is the journey that matters, not the destination

Offline AlexS

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Re: Ohrndorf 5 Cylinder Radial
« Reply #30 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #31 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.
« Last Edit: January 21, 2021, 07:50:54 PM by petertha »

Offline Art K

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Re: Ohrndorf 5 Cylinder Radial
« Reply #32 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
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Admiral_dk

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Re: Ohrndorf 5 Cylinder Radial
« Reply #33 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 ....

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #34 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


Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #35 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #36 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #37 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

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #38 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

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #39 on: January 22, 2021, 07:57:12 PM »
Jung 7-cylinder radial (Jung-5 is similar)

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #40 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #41 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.

Offline Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #42 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
« Last Edit: January 22, 2021, 09:26:06 PM by Vixen »
It is the journey that matters, not the destination

Offline Laurentic

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Re: Ohrndorf 5 Cylinder Radial
« Reply #43 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

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #44 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #45 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?

Offline Admiral_dk

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Re: Ohrndorf 5 Cylinder Radial
« Reply #46 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).

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #47 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.

Offline dieselpilot

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Re: Ohrndorf 5 Cylinder Radial
« Reply #48 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 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #49 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.

Offline Art K

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Re: Ohrndorf 5 Cylinder Radial
« Reply #50 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
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #51 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/

Offline dieselpilot

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Re: Ohrndorf 5 Cylinder Radial
« Reply #52 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


Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #53 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #54 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #55 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #56 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #57 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #58 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.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #59 on: February 10, 2021, 03:54:53 AM »
Some partial assembly at this point

Offline Admiral_dk

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Re: Ohrndorf 5 Cylinder Radial
« Reply #60 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

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #61 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.