Author Topic: Ohrndorf 5 Cylinder Radial  (Read 1741 times)

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.