COM-wobble- right front raised or not

[jb]

Good Morning,
My question relates to COM and running all four wheels. My sons car ran last week. The setup was right front raised, COM 0.600 from rear axle. All the axles are flat wit no camber. The car had a severe wobble toward the end of the track. To aggressive COM I believe. It was still fast and won the pack race. This car is very similar to the car we ran last year except that COM was 0.660 and all four wheels were down. It was also fast. We won the pack race and placed 7th out of 85 in the districts.
So I am wondering what to do now.
1. Will lowering the right front stabilize the car and eliminate the wobble with the 0.60 COM.
2 Move the COM forward and leave the right front raised

I haven't worked with cambered wheels. The alignment is very good for parallel,level and perpendicularity. Tires and axles are good as well. The race is Saturday so I cant go to crazy.

Thanks for any advice and it is great to find some people with the same interest as myself. Everybody else thinks I'm nuts.

[derbydominator]

Hey JB,

We're all nuts by the way!!! This stuff is way too addicting to stop though!

If you are running that aggressive on the COM's then you need to try to incorporate a rail rider technique. With one wheel up, it is pretty easy. Doubtful you can do any body modifications at this time, but the basics are : Start by cutting the front dominant wheel in 1/16" so that wheel will touch the center guide rail before its following rear wheel will make contact. Then get the axles canted on the rear such that the wheels migrate to the head of the axles going forward and backward. Then cant the forward wheel and create enough toe-in such that that wheel is pushing the car towards the center guide rail. In other words, if the left front is touching, then toe-in such that the car will head to the right. The amount is not huge, just enough such that the car would go to that side about 1 - 1 1/2" over a 4-5 ft. stretch of flat table. The car will then hug the center guide rail all the way down the track but reduce your speed wobbles and more importantly the major friction reductions from the rear wheels hitting the center guide rail.

Best of luck and let us know how you do.

[jb]

A good day racing. We moved the COM forward to one inch and left everything else the same. This is with number two son who is a tiger cub. I gambled that the competition wouldn't be as tough as a lot of people get their first exposure to derby racing here. This is my fourth. I thought that if i could reduce the wobble then we would still be a bit faster. The car was straight as an arrow. Took first place and set track record for time.
Your comments on rail riding really got me thinking of a big change from the way we have been building our cars. But at the race the track was aged and very rough. There were a number of wrecks, cars actually bouncing up and out of their lanes. It sure did make it exciting but it made me think that perhaps this would not work well for a rail rider. Can you tell me if a rail rider would be better on aluminum rather than the wooden and rougher tracks that we have always been on? I think that a rail rider would have had a tougher time on this track.
I have started building a track in my basement and plan on entering a car for R+D in April. I appreciate your advice, thanks again

[the woodbutcher]

If you can imagine, while rail riding, the wheel you use to steer into the rail will be in contact the entire time. Any seem from the segments of track will effect it. How much would depend on how rough the seems are. From the reports of the action from your race, it sounds like rail riding may have been risky
There are some terrific threads on this site devoted to this set up. Check them out and give it a try.