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Old 01-11-2020, 09:49 AM
madprofessor madprofessor is offline
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Default Worried about motor torsion.....

My current ongoing build ("SchizoBallz") is getting to the stage where I mock up the motor mounting location, including with the CVT (TC, whatever) installed. Looks like the original idea is still in play, the motor's level of course, and the CVT is hanging straight down from it, and it looks like the chain angle will be about 45 degrees down and toward the front from the 12 tooth sprocket (#35).
The 12 tooth will engage a 24 tooth on the jackshaft/swingarm pivot with about 13-15hp if all goes to plan. Question is with that kind of angle on the motor/CVT combo and that kind of pull on it from the chain angle, does anybody foresee a possible problem with torsion trying to twist the motor off its mounting, ie; snapping off a corner of the case where the bolts go through?
Mechanically my mind says all things locked down tight will defy any motion, but the picture in my mind looks like a recipe for trouble. Especially since rubber motor mounts, no matter how tight, do by their nature mean a less than weld-rigid result, and provides that gap under the casing where I worry it might torque.
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Old 01-11-2020, 01:53 PM
numscul numscul is offline
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Pictures would help give us a better idea of the situation you are currently dealing with

I wouldn't suggest mounting your engine with rubber mounts ever, ever ever ... rubber mounts will allow the engine twist and take the chain with it .... You ever been whipped with a #35 chain ? I have ... It feels good
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Old 01-11-2020, 02:32 PM
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Another problem with rubber mounts is that it interrupts the usual frame-engine circuit that most kill switches utilize. So you'd have to have an engine mounted ground point to the block, meaning at least two wires. I guess it's kind of a small price to pay, but as numscul said, I'd also be worried about the chain alignment.

Could you sketch out a diagram of what you are talking about?? If either sprocket is twisting, there's no way the chain will stay on.
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Old 01-12-2020, 09:11 PM
madprofessor madprofessor is offline
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Default Build is almost ready for chains.....

Only just now stopped laughing at the mental picture of getting whipped by a chain. That motor is going to be right behind my head, the build got that far today.
Picture the motor up in the air on a fixed rack behind the 2-person seat (4-point harnesses for 2 or for just 1 in the middle, steering will move over, dual pedals, etc.). That spot would let the swingarm come up and aroud it if I wanted 3 feet of travel in the rear. The CVT is hanging straight down now, no forward inclination, didn't want to trim the head of the forward dipstick.
The CVT 12-tooth to the jackshaft/swingarm pivot 24-tooth angle is about 45 degrees forward from the CVT. You can just imagine the possibility of torque twist when 15 hp slams it, but an answer popped into my head yesterday.
I'll completely rigid mount the motor to become one with a way oversized mounting plate, then put the hard rubber motor mount grommets (MFG S_____) under the four corners of the plate instead of under the motor. Same vibration dampening effect.
Yes, the motor could be electrically isolated, but okay as I would never cheap out on multiple ground jumpers, the more the merrier.
Pictures will follow in the next couple of days.
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Old 01-13-2020, 12:36 PM
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Still the same thing. The engine can move seperate from the chain and break it or it will pop off often. Just hard mount it to the frame. Don't worry about the vibration.
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Old 01-14-2020, 11:54 AM
madprofessor madprofessor is offline
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Default Physics of size........

Didn't explain it thoroughly...
The "hard rubber" motor mount grommet kit from MFG only allows maybe 1/16" of motion in any 360 degree direction when rubber both above and below the casing is snugged down tight between the washers. I won't depend on any motion of the thru-bolts at all, just the hi-freq. dampening in the rubber alone.
The size factor is maybe 15:1 over the tiny footprint of the motor casing itself. A really big plate since the framing there has to be that big anyway to leave room for servicing between the support braces. All I need to worry about on that is the adjuster slots and a hole for oil draining when changing oil.
The overall motion transmitted to the drive sprocket after all of that won't even be measurable.
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