Electrathon America Forum

jakeb2011 · Member

Chains vs. Belts

electrathon · administrator

Belts are quieter. Chains have less friction.

If you are going for comfort, belts rule. Going for effiency, there is a very slight advantage to chains.

Zaine Stapleton · Senior Member

David Douglas has a belt drive on the #55 car. It works great after we figured out how to fix a couple of problems with it. It runs great now!

Orinoco · Member

We've done a lot of work testing chain and belt efficiency, the test rig consists of motor, speed controller and axle rigidly mounted to a bench and driving an airbrake, the controller is used to maintain a specified axle speed. The airbrake is sized to give the same resistance as the motor would encounter during a typical race. During the tests the power supplied by the controller is logged and because comparisons are done for a fixed axle speed we're measuring power input required to achieved the same amout of work done at the airbrake.

We use 3/8" chain and sprockets and have done numerous tests of the same drive ratio but different sprocket sizes, i.e. 10/30, 11/33, 12/36, etc, the general consensus before hand was the smaller sprockets would be more efficient due to less teeth in contact with the chain so less friction; reality was somewhat different with a 19/57 being 16% more efficient than 10/30.

Tests were also done on an A-section belt drive incorporating an internally tensioned variable pitch pulley, this is planned to be used as a CVT so it was compared to several chain drive ratios from 23/57 down to 16/57. At the highest ratio there was no difference in efficiency, at the lowest the belt was around 2-3% more efficient than the chain.

Kirk Swaney · Veteren Racer

It's a great debate. confuse

I haven't run belt drive on Electrathons, but I experimented with friction drive in two cars. One got 8th at the Pentad Nationals in LA on a velodrome in 1999. I still have the aluminum drive wheels made from $3 pulleys, turned the v-groove down to a flat (on a lathe) and knearled the outer surface. The wheel mounted directly on the bigger Scott/Pentad motor shafts and was pressed against the tire. It competed well unless it was adjusted too loose or if it got wet.

The next year, I worked with the Hewlett-Packard Electrathon team to design & build a cone friction drive for it's honeycomb based AeroCoupe. The drive cone mounted to the motor shaft. Motor and cone were mounted to a servo-actuated linear slide bearing. The driver could adjust drive ratio on the fly. We never got the point of automating it's position, but it was a cool concept. I bet if someone wanted to play with it, the HP team would donate it to a good cause if they still have it.

Getting back to the belt vs. chain...

If interested, here's a short & simple Belt vs. Chain article, leveraged from an email reply I sent to a customer inquiring about belt driving a BugE build which I was quoting for him.

Some of you that have been racing Electrathon for years will remember Richard Kay's aerodynamic Kevlar Electrathon which used a V-belt on a very large diameter drive pulley that clipped onto the spokes.

-Kirk

electrathon · administrator

Orinoco wrote:
, the general consensus before hand was the smaller sprockets would be more efficient due to less teeth in contact with the chain so less friction; reality was somewhat different with a 19/57 being 16% more efficient than 10/30.

As I understand it the larger the sprocket, the less friction. The primary friction is not from drag against the sprocket teeth, but from rotation. The chain is being forced to bend, then go straight. There are many differant qualities of chains, so one chain to another can really mess with the outcome. The lube used on the chain can also have a big effect on rotational friction. A tight chain will really up the friction too (then you are in a situation similar to that you have with a belt).

Orinoco · Member

That's exactly what we found out through experimentation, it's the rate of angular change of the chain links that seems to be the primary factor in determining friction. However this isn't something that's widely known even by well quailfied Mechanical Engineers, one of the entries in the Greenpower Corporate Challenge this year was Jaguar/Landrover who had designed their transmission around a 10 tooth motor sprocket.

Regarding lubrication, we've found chain oil for chainsaws to be the most effective, seems to cuase less resistance than proprietry "chain lube".