stunthanger.com
Engine basics => Engine set up tips => Topic started by: Ty Marcucci on September 05, 2017, 12:59:13 PM
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Ever been at the flying site with your gang and up comes one plane, OS .25 LA-S engine with the right front motor mount hole busted out? Not unusual on trainers. It ran fine before, but this day is just would not start. Not even a pop. Fuel tank definitely full, line clear, filter clear, new glow plug, primed, tried three different glow drivers, has some compression but no popping, NONE. So, Jim removed the engine, gave it to me as I said I'll get it to run. This morning I started the disassembly, assuming some one had got things backward inside. It happens all to often on ebay specials. Right? Well, off comes the back plate and a chunk of the engine falls into my hand. LL~
A hair line crack, not visible when mounted on the plane, allowed all crankcase pressure/vacuum to be gone with each flip, thus no fuel was flowing into the combustion chamber, thus no pop and no starting. Would not even pop with prime. That simple once the engine was out of the plane.
A new crankcase is on the way. H^^
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Ty I made the mistake a while back to bolt one of my engines to a swap meet plane I was just given at end of day
Not a bad looking Giles 202 (RC plane) that I had a Magnum 45 for same as original builder
As I tightened down the 4-40 mount screws I heard a loud pop.... silly me
poor eyes and never really thinking anyone would build in that much twist and out of alignment
Hard lesson learend
It actually was much later when Marvin Denny schooled me that many Fox Mount pads were not machined true flat and parallel...as he was explaing why all the combat engines he sent me has been milled
I actually build my engine crutches with the engine lightly bolted down.... so far the several OS LA and FP .20~25s seem to have nice flat and parallel bottoms of the mounts
I have significantly dorked in my RST with LA 25 too many times and not yet broken more than a prop or slide forward tin tank...hell the stupid muffler even takes that abuse...
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Ty, if the crash broke the mounting lug it's not surprising there was other damage. That kind of damage may happen over rock hard turf or pavement. Also the weight of the plane may have been too much for it.