HTD (High Torque Drive) pulleys and belts are made by many people around the
world. There are various upgrades in belts, usually with some tradeoff in
efficiency (stiffer, thicker belt). There are various modified belt and
tooth forms which also give greater load capacity. Some are compatible with
HTD pulleys/belts, some are not and must be used in sets. Lots of companies
here in the UK cut custom HTD pulleys (for upgraded adjustable cam belt
drives or water/alternator conversions) and I've even got a shaper-cutter
that would allow me to cut my own on a gear shaver, or modified shaping
machine if I ever get around to it. You can get away with a much smaller
belt that the manufacturer would be happy with as they generally have a much
longer service life in mind. It's often an advantage to run a narrower
pulley because they are more tollerant of missalignment.
I can get off the shelf Aluminium pulleys from http://www.medwaypt.co.uk/
(take a look at their Karting catalogue). Ally is not the ideal material on
the road, it's too soft and abrades (Ask a Corbin Sparrow owner) cast iron
is ideal, but so is an engineering plastic like Nylon. An Aluminium rear
pulley with a Nylon tyre would work very well and I believe Asmo in Sweden
use them on their race Karts.
Paul Compton
www.sciroccoev.co.uk
www.bvs.org.uk
www.morini-mania.co.uk
www.compton.vispa.com/the_named
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, October 03, 2006 8:35 PM
Subject: [ElectricMotorcycles] Belts and Drive Pulleys For
ElectricMotorcycles
I'm looking to start a discussion about drive pulleys and belts for
motorcycles. Here are some things to start us off. First there seem to be 2
major
players/suppliers....
1) Gates Poly-Chain and
2) ContiTech (which I believe are the same folks out of Germany that make
the Continental tires)
Second there is really nothing unique to an electric motorcycle that would
preclude one from using a set up similar to that found on a gas production
motorcycle like the Kawasaki 440LTD from the mid 1980s (there are a large
number
of other examples from production bikes). These seem suitable unless the
ratios required for most EVs can not be reached.
Third I took advantage of Gates Application Design consulting service
(using
my 1994 Kawasaki Ninja EV as an example) and their response follows for
those of you with time to read it through. You may want to read it from
bottom to
top to understand the original questions I posed.
I appreciate any and all comments.
- Mike B.
DEVC - Colorado
Mike,
There are several potential issues with a belt drive on your motorcycle
application:
1) In order to get a 6 to 8:1 speed ratio and keep a similar sized front
(driver) sprocket diameter, the rear sprocket would be 18â? to 24â? in
diameter.
2) To get the above diameters, an 8mm pitch belt would have to be used.
14mm pitch belts are the most common pitch on motorcycles, with a few 11mm
pitch applications. The larger pitch is valuable in providing not only a
higher
strength belt, but also bigger/deeper teeth. The larger teeth help the
belt
avoid ratcheting (jumping teeth). This is important on motorcycle
applications, since they usually run at fairly low belt tensions and have
center
distances that change over the swingarm travel.
3) You mentioned using off the shelf components â?" the 8mm option would
only
be available as stock items by using industrial parts. These sprockets
will
be made of cast iron, and will be heavy and bulky for a motorcycle
application. We can make custom sprockets, but there would be a 6-8 week
lead time,
and an additional price premium over stock sprockets.
4) Without knowing the exact center distance (at rest, full bump, full
droop), I cannot tell you if we have a belt length available that would fit
(assuming solutions were found for 1,2,3 above). If you can get the center
distance measurements to me, I can perform the calculations.
As you can see, there are many significant issues for retrofitting a belt
drive onto an existing bike. We usually spend 2 to 3 years working with
motorcycle manufacturers for new drives before they are commercialized.
Unfortunately, that means that retrofits on existing bikes are usually not
practical
for many of the reasons above. As much as it pains me to say so, this may
be a
better application for chain.
Brent Oman
Manager
IGM PT Product Application
Gates Corp.
303-744-4768
____________________________________
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Wednesday, September 20, 2006 10:28 AM
To: Oman, Brent
Subject: Fwd: Belt Drive Application Design Question
In a message dated 9/14/2006 12:07:48 P.M. Mountain Standard Time,
Mbachandz
writes:
Hello Brent,
I am trying to come up with a belt drive replacement for a motorcycle
application. I would prefer not to resort to custom machining work if
necessary for
the (I'll call them) cogs required on the drive side and the wheel side.
First to the Gates Poly Chain related question.
The application is a 540 pound street (not race) 500cc engine sized
motorcycle, a 1994 Kawasaki Ninja (low power twin cylinder sport bike).
This bike has
been modified with an electric motor replacing the original gas engine. It
now puts out 6 continuous and 32 peak horse power with an estimated 40 to
50
foot pounds of torque. The current chain is a standard cycle chain in the
520
size.
My question related to the belt.....what size belt do I need keeping in
mind
that clearance related to width may be an issue?
The front sprocket (chain today) is ~3" across and the rear is ~9". The
gear
ratio is 12t fr to 45t rear. There is no transmission. The front shaft will
fit a standard cog sprocket I believe although it may be larger than what I
am suing now. The shaft size is 7/8" with a standard electric motor hey of
3/16". Again for the front I want to use standard off the shelf products
for
cost reasons.
The rear is a standard Kawasaki motorcycle wheel. This may be a harder
problem to solve. After some research I find that since the early 1980s a
number
of mid size Japanese motorcycles including several Kawasaki models have used
belt drives (e.g. 1983 KZ440). The ideal solution would be to find a fairly
large rear cog from one of these applications. The overall gear ratio that I
am shooting for is 6 or 8 to 1.
Please contact me with questions and your recommendations.
Mike Bachand
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