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This note is primarily a response to Mike Phillips question related to
drive types for a donor EV motorcycle. Most of the posts here have hit well on
the characteristics of belt or chain or shaft type final drives for 2 wheeled
applications. I just wanted to touch on some of the other points in a bit more
comprehensive evaluation.
Efficiency in order best to worst
1) chain
2) belt (in this case I am referring to a toothed synchronous type like
Gates Poly Chain GT2)
3) shaft
Please note that drive chains come in two basic types, industrial and
"O-Ring". Modern motorcycle applications all use the o-ring type that
seals a small reserve of oil to allow a longer wearing chain with
less attention to maintenance. O-Ring types do reduce efficiency compared
to industrial types. Over the past few years manufacturers have
created things like X-Rings to address the efficiency
loss issue.
Weight in order lightest to heaviest
1) belt (aluminum cogged pulleys, kevlar fiber reinforced toothed
belt)
2) chain
3) shaft
Most people do not realize that in a typical motorcycle application the
chain and sprockets are fairly heavy. This is why you see aluminum sprockets and
slotted chain side plates used in racing applications. On my 750cc Suzuki ICE
street bike (all steel) a 14t front sprocket, 41t rear, and 96 links of #630
chain weigh ~12 pounds.
Noise in order of quietest to noisiest
1) belt
2) shaft
3) chain
My Kawasaki Ninja EV uses a std. motorcycle type #525 chain drive. Once
the ICE is gone the noise of the drive chain is really LOUD. This is true
on every EV motorcycle I have ridden. The noise is enough to be really annoying
even when wearing a full coverage helmet. Of course this helps in parking lots
as people can hear me coming and I don't scare my neighbors. I have to admit
that I lust after a quiet belt drive.
Handling
Note that the shaft drive has an unusual behavior under hard acceleration
like exiting a corner. I think of the shaft drive as much like the ring and
pinion gears in the rear end of a rear drive car. This may not be completely
accurate for a motorcycle, but bear with me. When accelerating hard the ring
gear attempts to climb the pinion causing the rear seat of the motorcycle to
rise instead of the expected squatting behavior. This feels funny to most riders
the first time they are on a shaft drive bike. The short story is that you get
used to it and modern motorcycles have attempted to minimize this
behavior.
Durability most to least
1) shaft
2) chain
3) Belt
The average well maintained O-Ring type chain should last well over 15,000
miles which might be 8 to 10 years on the average EV motorcycle. The downside is
that periodic adjustments ~ every 1,000 miles are required to accommodate for
the chain stretching and of course there is some throw off of the oil used
to lubricate the chain. The oil throw off on my rear wheel and electric
motor really offends my EV sensibility.
Also note that riders may want to factor in their riding conditions before
choosing a belt drive. Small rocks form dirt, gravel, or even a freshly
coated blacktop rock chip type surface can tear the crap out of belt quickly
causing complete failure while driving.
Cost cheapest to most expensive
1) chain
2) belt
3) shaft
A good chain set up costs $150 to $200 including replacing the
sprockets.
Conclusions
- I really don't mind the maint. associated with a chain drive, but the
weight, noise and mess are unpleasant. Cost and availability of
modular replacement parts is also an advantage.
- I recognize that a shaft drive does offer quiet operation with no mess,
little maint. and great durability at the expense of weight and
handling.
- However I believe that the ideal drive for an EV motorcycle is a
synchronous belt drive. The benefits are no messy oil, light weight and
quiet operation. The downside is cost, potential durability issues and
maintenance to adjust for belt stretch.
Mike Bachand
DEVC
Colorado |
