Engine Technique

Engine Technique George Aldrich FOR OUT FIRST column lets take some pain out old engine break-in problem some proven safe methods Break-in run-in consists mating new parts operating temperature combine make up new engine will deliver its maximum intended power operating temperature key whole break-in process As new engine heats up parts start expand move around crankcase expands allowing ball bearing outer races seek ideal seating top edge piston heats up cylin der thus begins wear times causing shine top edge lapped pistons As piston metal heats up highest operating temperature reaches controls much will expand After engine stopped piston will retain some growth cools thus taking permanent set Another way think what happening think operational heat treating After reaching operating temperature engine parts cease moving around tending reach run ning stabilization relative temperature will take great deal continuous run ning stabilized temperature achieve desired wearing engine parts preceding mind quicker break-in lets repeat heating cooling process often series two-minute runs has proven preferable method over continu ous period running hotter can get engine safely the parts expand shortening break-in time safe method achieving faster break-in reduce prop size increases rpm friction fore heat added friction heat added danger over-heating damage Obviously what want get extra revs just leaning mixture using smaller prop fuel ade quate proper lubrication much better faster break-in can achieved Considering above now have series fast two-min ute runs using proper fuel allowing normal cool-down between run selecting break-in prop use nylon exception 1 /2A sizes best break-in prop have found made rock maple epoxy impregnated continu ous glass carbon fiber Start prop two sizes larger normal flying prop much heavier and/or wider blades Carefully measure amount cut blade use razor saw neatly remove required amount Leave tips blunt square gives clubish prop ample strength withstand high rpm list prop sizes along trimmed lengths 04906 09 15 1923 2936 40-46 60 78 6x4 7x4 7x4 8x4 9x4to9x6 9x6 10x6 l2x6or 11x8 Trim 4 5 Dia Trim to5Dia Trim 53/4 6 Dia Trim 6 6 Dia Trim to7Dia Trim 7 Dia Trim 9 9 Dia Play safe never stand side running engine thrown prop blade could put out eye Check props regularly discard signs cracks damage years speed flying working thousands engines run various all-synthetic oil fuels has convinced no oil like castor oil An engine run over-lean has infinitely greater chance being damaged all-synthetic lubricant fuel operated fuel containing least 5 percent cas tor oil say castor oil Im speaking least AA degummed grade Hopefully some manufacturer will come up adequate self-sustaining synthetic date have found can carry load alone engine used FAI event prohibits nitromethane check existing rules run no other fuel An engine completely run-in non-nitrated fuel 5 percent nitro mix will require further run-in 25 percent 30 percent nitro mix used bit unsure start 5 percent nitro mix containing less 10 percent castor oil total least 25 percent lubricants correct prop run engine fast will run comfortably means sagging possible make first few runs muffler engines made out side USA toleranced non-nitrated fuel require careful break-in cause being fit together tend overheat muffler just adds heat As lapped engine breaks-in bright shiny band top piston will gradually widen turn dull gray succeeding two-minute run ringed engines take little care run rich side very import ant get rings fully seated before trying really open up full power As ringed engine breaks-in properly compression will increase needle valve setting will come less critical smaller props used method present bit problem starting engine way keep getting finger hit safer know call Bump Flip Dont ever flip prop first grabbing prop fist pulling engine over particular true flooded engine dont feel engine bump passes through top dead center battery connected dont flip Continue pulling over until feel bump immediately flip prop flipping best place finger close hub possible Remember bump before flip wont get hit What appears column depends great deal AMAers What would like know read about depends whether let us hear address George Al drich 128 Austin Blvd Edinburg Tex 78539 Home-built Russian in-line single-cylinder en gine talk Control-Line World Champion ships last summer flown built V Kramarenko An-14M Left George Al drich work shop discusses engine break-in highpoint gadgetry attained Polish entry AerOlympics Constructed L Podgoraki partial view Storma vik gives some idea level competition