Author Topic: Ohrndorf 5 Cylinder Radial  (Read 23954 times)

Offline scc

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Re: Ohrndorf 5 Cylinder Radial
« Reply #360 on: November 19, 2023, 08:46:26 PM »
Great achievement............ :cheers:             Terry

Online Kim

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Re: Ohrndorf 5 Cylinder Radial
« Reply #361 on: November 19, 2023, 08:56:26 PM »
I did find the video eventually - way down, close(ish) to the bottom of the page.  Lots of adds though :(

It was a great run!  I can see why you are pleased, you should be!  ;D :ThumbsUp:

Kim
Were you logged in there? I was not, found the post where it said heres a video  but it didn't  show. Great reminder of why I  stopped posting there, horrible load of ads.
Humm... not that I know of.  I may have been a member of the site many years ago, but I haven't logged in for years. And it was offering to let me logon through Google.  I opted not to.  So I don't think I was logged in...
Regardless, Ron posted it here, so that solves the problem.
Kim

Offline jcge

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Re: Ohrndorf 5 Cylinder Radial
« Reply #362 on: November 19, 2023, 09:04:03 PM »
Congratulations petertha !! I can well imagine how pleased you must be.
I have thoroughly enjoyed following your progress via this thread. Thank you for posting in such detail throughout.
Regards
John

Offline Admiral_dk

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Re: Ohrndorf 5 Cylinder Radial
« Reply #363 on: November 19, 2023, 10:04:06 PM »
Sounds and Runs Great + with some Urgency when you open the Trottle  :praise2:

Per     :cheers:

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #364 on: November 19, 2023, 10:09:37 PM »
I imported the video into my own youtube account, and post it here. I hope you don't mind, petertha! I did not make it public, only "unlisted", so only those with the link can view it.

Thank you Ron!

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #365 on: November 19, 2023, 10:20:33 PM »
I think I did about 5 runs of a couple minutes duration each. I didn’t want to push my luck any further the first outing. Mostly what you will now see is lots of oily pictures from initial teardown. The components looked acceptable, but I also discovered some near miss problems which I’ll discuss in more detail. The good news is there appeared to be a decent oil slick on all the internal parts. Oil residue was migrating sufficiently forward in the engine to lubricate the cam plates, gear train, front bearings & rod assembly either by blowby or induction charge. I did see quite a bit of cast iron ‘dust’ entrained in the oil which would be quite abnormal for a commercial engine break-in. It doesn’t look very nice but I couldn’t feel anything one could describe as grit by just rubbing the oil residue between my fingers, more like a dark watercolor like stain. For now, I chocked this up to bedding in new rings within shop made cast iron liners. Of note, this blackness diminished more & more with every subsequent run but I stopped taking pictures.

The cam plates showed shiny skid tracks from the lifters wearing through the black heat treat coloration, more like polishing but no grooves. I could also detect some unequal contact wear thickness near the rise & fall cam fillets, but too early to comment on that.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #366 on: November 19, 2023, 10:25:07 PM »
On my last runs I noticed a few cylinder flange screws loosened again after I had already tightened them the prior run. This may have been contributing to what my ear said was rougher running. One of my pushrod tubes was starting to jiggle around, probably as a result. Another good reason to stop while ahead. A floating cylinder is a bad thing. Thankfully the M3 threads were still in good shape but this issue required attention. Some other parts pics.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #367 on: November 19, 2023, 10:26:46 PM »
Crankshaft & rods

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #368 on: November 19, 2023, 10:28:18 PM »
The #1 piston assembly looked pretty good overall. Lots of lubrication, no shiny wear areas or hot spots. The ring looked like it was just starting to wear in evenly enough around the periphery. A few vertical scratches on the piston here & there but nothing of consequence. However, I noticed a little divot on the piston top which I assumed maybe from particle ingestion or something, but on closer inspection looked remarkably like a crescent shape valve impression. It was on the exhaust side only. I immediately checked around the edge of the edge of the exhaust valve but could not see any deformation of feel a burr. As I proceeded to each cylinder I saw more or less the exact same impression on all piston crowns. Not good. I immediately suspected my cam timing was perhaps incorrectly set a gear tooth off, but my witness marks were correct… unless I somehow messed up the clocking from the initial get go. I also noticed considerably more valve gap on the exhaust rockers than was pre-set. I’ll return to this issue under remediation, but I think I used up one cat life. This could have been much worse.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #369 on: November 19, 2023, 10:31:26 PM »
Remediation pics. First the easier stuff. Here is my initial makeshift drill starter. It mostly turned the engine over OK to where it would fire, but the prop engagement pegs were mangling the delicate trailing edge root despite my attempts to rubberize it with tubing, heat shrink & electrical tape to help snub the contact. I was concerned about weakening the prop to the point of it breaking.

My spinner nut fell off a few times which caused a few Keystone Kops episodes of locating parts in the grass, so I made a more robust wrench to tighten.


Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #370 on: November 19, 2023, 10:38:05 PM »
After subsequent runs it was becoming obvious the drill starter had to go. It continued to chew the prop and had more difficulty turning it over as compression improved. I also suspect that as the engine began firing, the drill’s gear drive was probably limiting it from free running until I could withdraw the peg drive, which is probably not healthy vs. a one-way clutch mechanism or freewheeling motor with power off. I searched for gear reduction drive RC starters & realized the RC world has changed. There are some big boy starters for much larger, typically 2-stroke engines. I was aware of Kavan planetary gear starters used on RC 4-strokes back in the day, but they are no longer made. Eventually I found this PGD reduction starter from Just Engines in UK. I bought a dedicated 4S (14.4v) LIPO hard shell RC battery pack & made a plywood carrier frame. So far it has worked very well. Fortunately, the silicone cone could be flipped to expose a smaller diameter hole, so I made a matching, lager spinner nut.

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #371 on: November 19, 2023, 10:47:05 PM »
I actually made a tester Teflon gasket for under the cylinder flange earlier but elected to omit them initially. I wasn’t too keen about using Loctite on the threads if it could be avoided. I sourced some 0.002” thick sheet so it wouldn’t affect CR very much. As it turns out, the gaskets did some good. The screws thereafter stayed intact on subsequent runs, so maybe it provided a bit of conformance to the prior metal on metal contact?

Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #372 on: November 19, 2023, 10:54:52 PM »
The exhaust valve indentation on the piston tops was a serious issue to address. My first suspicion was that I had incorrectly placed the ring gear cam plate assembly onto the idler gear cluster off by a tooth. This would have the timing effect of lagging the exhaust valve closing beyond TDC (black bars on the timing diagram). This might explain why there was no matching intake valve indentation on the intake side of the piston. All pistons had the same exhaust only mark dent. One would think altered timing would mean rougher running, but I really had no smooth/rough reference experience yet. It seemed to idle & transition reasonably well but this was my first rodeo. I didn’t take it beyond half throttle for more than an occasional blip. But it turns out, I my cam position was indeed correct, my original witness alignment marks were correct.

This engine is relatively simple to set up & verify in this regard. Exhaust valve closure & intake valve opening occurs equally either side of TDC.


Offline petertha

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Re: Ohrndorf 5 Cylinder Radial
« Reply #373 on: November 19, 2023, 11:04:59 PM »
So, I commenced measuring all the contributing dimensions (there are many). Rod throw, piston height, cylinder deck height, cam lobe rise, valve clearance… Everything was within a thou of drawings. I did deviate slightly from drawings by decreasing the valve seat width, but net effect actually increased the valve cage submergence up into the head chamber & served to provide even more valve clearance.

I did a little bit of CAD motion study & concluded there was indeed theoretical clearance but it was actually quite close which I never bothered to consider before. If I was seeing the effects of valve float or temperature increase, this might add up to several thou & that seemed to be the extent of valve strike impression.

I’m really not sure but in any event, it needed to be dealt with, so I considered my options. I could add a head shim & gain some valve clearance that way, but at the expense of compression ratio. I estimated I was nominally at or under 9:1 but CR drops to 8.6:1 with only 0.005” shim or 8.3:1 with 0.010” etc. Maybe I had sufficient CR to spare but it seemed counterproductive to chase that option if the interference represented the same 0.010” confined to a tiny, localized impression area.

I could add a shim under the cylinder flange which raises the head from the fixed piston throw. That has the same CR reduction effect, but I was already contemplating some kind of gasket under the cylinder flanges to help with metal-on-metal mating & bolts loosening.

The other option was to cut extended crescent shaped recess pockets into the piston tops aligned to the valve strike area. I couldn’t go too crazy on this depth wise, limited by the piston crown thickness, but on paper it bought me significantly more potential clearance with minimal CR change. I could always still do the shimming if required.

I still had my piston holding fixture used for milling the rod clearance pockets. The fixture has a through hole for the wristpin, so that would self-align the piston orientation. Then it was a relatively simple matter of angling the piston/fixture in the mill vise to the valve angle & dropping down an endmill to increase the pocket dimensions. I did the other (intake) side the same just as a precaution & smoothened the edges with rubber abrasive. You can see the before & after net result.

Online Vixen

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Re: Ohrndorf 5 Cylinder Radial
« Reply #374 on: November 19, 2023, 11:07:30 PM »
Hello Peter

You could try opening the exhaust valve tappet gap and ride higher up the exhaust cam lobe.

Mike
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