Sprocket/Rotor Combo

[DoItDoug]

I noticed that a few teams (including UMC, I think) were running a sprocket/rotor combo in the rear. If anyone on this forum ran one, what did the design judges say about it? Design for servicability (changing sprocket size could be a problem). What about materials? Most sprockets are aluminum and wear quicker than a stainless rotor. What did you decide on and did you have any problems?

Doug Temple
'02 VT FSAE
www.vtmotorsports.com (http://www.vtmotorsports.com)

[Kevin Hall]

There is another post made quite a while ago that discusses the merits of this....however, any judges comments would be great.

Kevin Hall
University of Saskatchewan
Engine Guy in Need of Help

[JDF]

The judges loved ours. Even with the bare aluminum sprocket. Seemed to think it was a great way to save weight. We plan to add a hard-anodized finish making surface wear insignificant. Not sure about warping yet. A 520 sprocket is about 1/4" thick, pretty thin for an aluminum rotor. Options would be to use a 530 sprocket and thin the teeth down for a 520 chain, or make our own from scratch. I'll probably try making a few this summer, trying different materials, thickness, and surfaces.

We can fit either a 54 or 53 tooth on right now. Possibly a 52, have not checked. With careful placement of your caliper, you should be able to get a few sizes to fit. Or you could use some type of radial mount caliper with spacer blocks to adjust for different sprockets. Our caliper was machined into the diff mounts, saving weight, but limiting sprocket options.

We use the term "sprotor"� to refer to our sprocket/rotor. That was decided on in a state of near drunken stupidity caused by too many late nights. The term stuck and is in common use around here. Even Rebel Gear, who makes our sprockets, uses sprotor. You should too...sprotor.

JDF
Tennessee Tech
Golden Eagle Motorsports

[Bob Wright]

dont bother unless you run a limmited slip that lets you tune the lock up differently from drive to brake through the diff housing. We ran a brake on the skrocket for a few years and we're getting rid of it now. You really want to control your rear brakes better so you can make the thing turn in- there's lap time gains that are bigger than the weight savings.
Some Judges like it, but then again some judges live under bridges picking off billygoats for the rest of the year, so that proves nothing.

dont do it- its painfull

Bob Wright
Monash University
Australia

[gus]

judges loved ours, and to my knowledge, we've had no problem from the design.

[MercerFSAE C. Burch]

Also ran a sprotor and did very well in the competition too. The judges loved that it saved UMC at least a pound of that vital rotating inertia mass. They validated their concept through testing to make sure that the chain grease didn't affect the braking performance, among other testing parameters. These facts were noted during the design finals by the judge giving the "Carrol Smith" talk.

Chris,
Mercer Unversity - Drive!
Coming to an Auto-X track near you, May 2004!

[terc04]

I did the design work for the University of Missouri - Columbia sprocket/rotor. We had a few reasons for going to this design. The biggest one is that we were using it to validate its design for a unique differential we are testing for next year. For that purpose it worked great. Other benefits we noticed while testing- lower weight (~1lb), a lot more packaging room, and a clean design. Problems- chain abuse, added slop in drivetrain contributing to a nasty chattering under braking over the bumps on the enduro, explaining the design a billion times.

Overall, I am pleased with the "sprotor". It does require a careful design and a few more custom parts, but for our objectives it worked perfectly.

Tim
Mizzou Racing

[Patrick W. Crane]

Has anybody had the problem of getting grease on the rotor surface from the chain?

- Patrick
quote: "i do not approve of racing near concrete walls"
- Speaker at Team Captain's meeting, Detroit 2003.

[Brent Howard]

As far at the sprotor I really like that the rotating mass is reduced and that the packagina is much easier(packaging is nearly always a huge concern). However I do have a couple of problems with it and was wondering if anyone could come up with easy solutions. First is that if anything fails withing the drive train you would lose rear braking. We have had our sprocket twist before and our diff rip out. Had we not been running a sprotor our rear braking system would not have functioned and our stopping would not have been controlled. The other thing that worries me about a sprotor is that the adjustability as far a sprocket sizes just went out the window...or does it? Is there any way to adjust sprotors for larger or smaller sprokets without a whole lot of work and completly changing the braking system? There are probably solutions to these questions, but i would like to know what they are.

Brent

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)