>-----Original Message----- >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] >Sent: 30 May 2006 21:06 >To: 'Microcontroller discussion list - Public.' >Subject: [OT] Model engine starting > > >Guys, >I know there are a few people that have some experience with >glow engines on here so here is the dilemma . I have a Saito >100 four stroke engine that is being built into a model >trike... Due to the arrangement of the power train it has a >c/f clutch that's in line with the differential so I have no >access to the end of the engine for starting it. So I have >modified a traxas ezstart so that it fits on the nose of the >engine using a sprag (one way) bearing type HSK8 this fits on >the main shaft and the final gear is glued on to the outer shell. > >Now comes the problem... > >When the engine is dry the system works fine, When it is >fuelled it backfired and blew the guts out of the bearing (the >sprags reversed) its rating is 3.2nM and an overrunning speed >difference of 12000 rpm with a 8mm core and 22mm outer diameter. > >How do you >1. Stop a glow engine backfiring Difficult, the point of ignition at very low engine speeds is unpredicatble with a glow plug. Converting to spark igntion could solve your problem, no doubt creating many others in the process! >2. Calculate how much energy comes from a backfiring >engine so I can >accurately size a starter bearing. Not easy to calculate, but worst case I guess you could assume that it's simmilar to peak torque of the normaly running engine (if you know that of course!). >3. Start the thing a different way (with an onboard starter) > Some kind of cush drive or friction clutch between the starter and the engine sounds like a good idea to absorb any torque peaks. This could be as simple as using a flat belt drive and adjusting the tension so that it slips above a certain torque. You could use a shear pin to protect the bearing, but that would need replacing once failed which could start to get annoying. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist