How to alter derby wheels?

[AnaMaria]

Our district is allowing just about anything this year, which is a major change for them. I'd like to trim the wheels so they only run a narrow strip. What's a good method for getting the excess off? Craft knife? Sanding? Something else?

[FScouter]

You could mount them in a lathe, or better yet just turn new ones.

[evmori]

I'm gonna guess these are the plastic wheels??? If so, get an Exacto knife & cut the tread part off. The sand 'em so the edge is smooth.

 

Ed Mori

1 Peter 4:10

[AnaMaria]

Yes, the plastic BSA wheels. My not-yet-old-enough to be a Cub Scout son and I are collaborating on a car for our "open" division. He designs and paints and I engineer. We were 2nd last year, and I'd really like to win!

 

Wolf scout son may or may not get altered wheels. I'll let him decide.

[Eagledad]

Chuck it up to any drill and cut them down with a file or sandpaper. Ive never had to narrow them down as much as you want, but Ive trimmed and tuned many wheels with this method. I dont think it will take you very long with a heavy grit paper and then you can smooth them out with smaller grit when you get close to the width you want. Each wheel will be very balanced. Even with narrow tires, I think most or your speed will still come from how you dress and polish your axles.

 

Barry

 

[AnaMaria]

I agree with you and feel pretty good about my plans for that. There are some higher tech polishing materials that I don't have access to, but I'm pretty happy with what we have.

 

The other key seems to be getting as much weight as possible on the car and I feel pretty good about the plans for that as well.

 

My impression is that this is only a moderately competitive group and the tips I've dug up over the last couple of years will serve me well.

[packsaddle]

Well if they're going to let you 'cheat' any way you want, Eagledad's approach is good. Keep in mind that there are two things to minimize: friction and wobbling (which translates into friction).

Making sure the car runs straight and true is important. Cutting the wheels down to narrow them helps as well.

BUT if you can manage it, mount them so that only three are touching the track. If you can do this and maintain a straight track, you've eliminated 25% of wheel friction with no effort whatsoever. I've seen this done and it seems to work best with one of the outside wheels slightly off the track surface. Then to keep the remaining ones at minimal friction, cut them to a knife edge. Keep the overall radius but minimize the wheel-to-track contact.

If they allow lubricants, don't mess with the teflon stuff but stick to the tried-and-true silicone lubes. And don't load the moving parts so much that they are gummed up, just apply enough to do the trick. Finally, to perfect your scheme, set up a short section of track with identical design to the official track and 'fine tune' your options.

Above all else, make sure the boy has minimal input and learns that he should, Win if you can, lose if you must, always cheat, and if they take you out, leave tearing down the ring.

http://www.cantstopthebleeding.com/?p=8089

[AnaMaria]

The district rules would allow only 3 wheels on the track, but our Cubmaster has outlawed it for our Pack.

 

We're limited to the standard dry lubricant applied outside the facility only.

 

I also cut new slots for the axles, but I'm not sure I got them straight enough. I left the originals and will decide when it's time to install the wheels which ones to use.

 

This is all within the boundaries of the rules this year (much of it was not for last year, so I have no experience with it). And I'm only going all out on "my" car, which is raced at the Pack level in an "open" class only. My Wolf gets to decide how much of the extra stuff he's interested in. We didn't lengthen the wheel base on his car because it would look funny with his design. My guess is he won't want his wheels cut down for the same reason.

 

 

[msnowman]

Because so many people use the internet to get PWD ideas, and because rules vary some by Council (or District, or Pack) we always hold a PWD meeting where we hand out car kits and Council rules. Our Council does not allow ANY modifications to the wheels AND requires all 4 wheels to be touching. We also can't alter the axle slots or change the wheelbase and must by under 3 inches tall.

 

It is interesting though to see the variations allowed by different Councils on the race. Its a good reminder that Irving sets the base rules, but your actually mileage may vary.

 

YiS

Michelle

[AnaMaria]

all four wheels touching, the rules you describe have been our District's rules in the past. The email that accompanied the rules this year seems to me to imply that they are tired of dealing with irate parents and are going liberal to see how it goes. My guess is that they'll be back to stricter rules next year.

[SSScout]

If the weight is held constant, and therefore balanced between the wheels that support the car, why would one less wheel necessarily mean less over all friction? The "normal" force is still the same and instead of four wheels each having 1/4 the force/friction, eliminating one wheel would mean each of the remaining wheels would have 1/3 the force/friction.

By that reasoning, eliminating TWO wheels might be better still. Anyone try this: Balance the cars weight such that 95% is on the rear axles (two wheels) and the front axles only hold a token 5%

(or less!) of the cars weight. Then, as the car rolls down the track, aero forces might even take more weight off the front axles.

 

Polish the axles and clean up the wheels to eliminate "chatter" and "wobble", so the car does not rub unnecessarily on the guide rail.

 

One problem perculiar to some tracks: as the down grade curves up and bottoms out to the flat, some nose heavy cars will drag on the curve up of the track. Watch for that.

 

Alright, touch cars and come out of your corners rolling. *ding*