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[CVOThunder]

At the risk of being a moron, why don't they use a solid crank and plain bearing side by side rods? Too much change and deviates from the look and what has been done in the past? I think I've asked this before but don't recall an answer.

[djkak]

Picture a rotating Harley crank assembly.  Now picture the left (drive) side being snatched to a halt (a worst-case scenario)....What will the right side want to do?  It's pretty heavy and it's only pumping oil and operating the valves through the camshafts.  Won't its momentum tend to make it want to continue rotating?....

It's easier for me to picture this happening by hard deceleration of the left wheel than by merely operating at a lower engine speed on a regular basis.  Hard deceleration of the left wheel is easy to see happening by sudden downshifting without matching engine speed to the new gear, or by somehow locking up the rear wheel.  It's not so easy for me to see it happening sufficiently because of motoring down the highway at 2k RPM and adding some throttle.

I believe that the intensity of the snatch force (torsional vibration) increases dramatically as the engine is lugged down and the compensating sprocket begins to hammer against its stops. My sense is that 2,000 rpm is probably outside of the critical range, but 1,300 to 1,500 rpm in 6th gear would probably get you there with an aggressive throttle setting.

The shift occurs when the right flywheel's inertia overcomes the interference fit of the crankpin. That is to say that in this scenario the rotational energy stored by right flywheel overcomes the friction at the crankpin, allowing the right flywheel to continue rotating while the left flywheel rapidly decelerates; essentially what glens said in his post.

While it is certainly possible to shift a set of wheels with behavior like a clutchless upshift, (rapid downshifting would increase the crank’s speed) it is my understanding that lugging an early Cruise Drive, as described, will produce load spikes of 1,400 - 1,600 foot-pounds at the crankpin in a stock Twin Cam, which exceeds the capacity of that joint. JMHO

[djkak]

At the risk of being a moron, why don't they use a solid crank and plain bearing side by side rods? Too much change and deviates from the look and what has been done in the past? I think I've asked this before but don't recall an answer.

H-D has a prototype engine setup like this on their engine wall at their Museum. I believe that this was built somewhere around 1975, and of course the V-Rod runs a one piece crank with plain bearing rods and offset cylinders.

[GMR-PERFORMANCE]

The new style sprocket shafts with the fine spline, are prone to twisting and bending... they can do one or the other or both .. I have a left half of a Jims crank here that was replaced .. not by Jims ha ha that would be funny. But anyways it is twisted up and bent very nicely.

It's not easy to check and really unless you relieve the crank of valve spring pressure you will not get a correct reading.  Is there is reason you want to check it?

[glens]

The shift occurs when the right flywheel's inertia overcomes the interference fit of the crankpin. That is to say that in this scenario the rotational energy stored by right flywheel overcomes the friction at the crankpin, allowing the right flywheel to continue rotating while the left flywheel rapidly decelerates...

While the thought is substantially the same I prefer that collection of words to those I'd submitted

While it is certainly possible to shift a set of wheels with behavior like a clutchless upshift, (rapid downshifting would increase the crank’s speed)...

I guess what I'd had in mind earlier regarding the [hard] downshifts is the possibility that the right wheel may find itself with sufficiently less rotational energy than the left.  I suppose I could express my thoughts better by the suggestion that any time the speed of the wheelset isn't being driven fairly evenly by the crankpin itself the chances for shifting increase in proportion to wheel momentum differential.

[HD Street Performance]

There are a few things that can make either side scissor. The root cause is shock loading torsionally and or a loose press fit. That can happen on either or both sides.