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Old 04-28-2002, 10:13 AM   #21
SlowBear
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Default Re: Hybrid Power for Motorcycles?

Seems like a nice idea but I'd says its chance of success is about the same as my chances of winning the lottery. BTW, I don't buy lottery tickets. I'm not an ME but here are the problems I can see in this engine:



The bottom end will (if it works at all) give new meaning to the term "rocking couple". The entire weight of the piston and rod and a part of the "horizontal member" is completely uncompensated, in a normal engine each cylinder partly balances its reciprocating weight with additional weight opposite the big end. When the left side is at BDC, the right will be at TDC, both will be trying to spin the engine counter-clockwise. When the left side is at TDC the engine will be trying to spin clockwise. Given that the power is routed out the bottom of the engine any rubber mounting would be difficult, the rocking couple would be centered at the middle of the horizontal member and would produce a pretty large movement in the output shaft if the engine was allowed to move. This would make it difficult to put enough flex in the drive train to let the engine vibrate. Moving the output to the side of the engine would make rubber mounting work but would entail even more power loss with a set of right angle gears.



BTW, that "horizontal member" will be pretty heavy and/ or expensive for a given size engine since its loads will be bending loads, not compression/ tensile like a connecting rod or twisting like a crankshaft. I'd also love to see how they lubricate the connecting rod and piston, I can't see a path to move oil to either bearing, that leaves spray jets, splash or oil-in-fuel, not very appealing options.



Also, the bearing shown between the connecting rods and the horizontal member in the illustration can't work since the drawing indicate a simple pin. The end of the horizontal member describes an arc, the connecting rod can only move in straight lines, how is the "left-right" movement allowed without bending of one or both parts? They may have a clever scheme, the ones I can think of involve a large cost in terms of friction, money or both.



Finally, it seems to me the "friction tax" on the device that converts the linear motion of the horizontal member to rotating motion would be very high. Honda does something similar in some (automatic) ATV transmissions, in that use I think it is called a "swash plate'. IIRC, they rate the transmissions as 65% efficient, i.e. 10 HP in is 6.5 HP out. The 35% loss includes the hydraulic pumps and all but even if the swash plate is only half the loss it would be 10 HP and 8.25 HP out. This doesn't seem like the hot set-up for a fuel efficient engine.



I'd be much more impressed if they had sourced a conventional engine from Honda or Rotax, at least for the first version.



JMHO,



SlowBear

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Old 04-28-2002, 04:09 PM   #22
jmeyn
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Default I agree but...

They're willing to sacrifice something to seal the combustion volume from the "crank case" to improve pumping efficiency. This improves control of emissions as well by eliminating blow-by.



Whether the trade-off is worthwhile is subject to measurement, which they haven't published so far. I've asked for numbers.
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Old 04-28-2002, 08:17 PM   #23
SlowBear
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Default Re: I agree but...

If memory serves me correctly, "crankcase stuffing" (drastically reducing the volume below the piston) has been out of favor for about 30 years. Modern two-strokes use fairly high volume crankcases, bigger transfer ports and slower air flow to increase the time it takes for the charge to cycle through the combustion chamber and out the exhaust port. This is, I would say, the next big step in the evolution of the two-stroke after the development of the loop scavenging pattern expansion chamber exhaust. This is a major reason two-strokes power bands are much wider now than they were in the sixties. Power bands were measured in hundreds of RPM back then and race bikes had as many as 18 gearbox ratios. When the FIM limited all bikes to six speeds in it forced development of wider power bands and the end of crankcase stuffing.



BTW, I was wrong when I said there was no easy way to lubricate the connecting rod, I realized after I posted that they could pass oil up the connecting rod via either the upper or lower guides. I still can't figure out where (other than out the exhaust port) the small end or piston lubrication oil would go.



Finally, this bottom end layout has been bugging me all day, I finally figured out why. I've seen it before in stationary engines. I think it was called a "Walking Beam" design. IIRC, it fell out of favor when engines began to run at more then 1000 RPM.



My point in all this, beyond enjoying critical thinking, is that this whole this smells very much like an Al Melling project, seen any Norton V8s lately? This when I really, really miss the late, great Gordon Jennings. I would love to see his analysis of this design. Kevin Cameron could also do a good analysis but he it not as cruel as Jennings so it wouldn't be as much fun.



Cheers,



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Old 04-29-2002, 03:33 AM   #24
jmeyn
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Default Re: I agree but...

I prefer to think that these are un or under-employed mechanical artists trying to fund their hobby.



The low volume narrow power band approach would make a lot more sense if the engine operated only between max torque and max power.

The engine would help power the bike only during excelleration. The rest of the time it would charge the battery as required; during braking and coasting, the motor would recharge the battery without engine drive.

A continuously variable transmission between the motor and the wheel would be needed to keep the motor rpm high enough to charge the battery.

Complicated and expensive, but it's already been done.
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