Track Length and alignment

Mike a

Lurking
Feb 27, 2017
3
0
1
52
Auburn, AL
We won pack our first year with a rail rider, extended wheel base, 1.25 COM from rear axle, wedge. This was on a 42 ft best track that had a few rough spots. District was on a 35 ft best track that seemed to be fairly new and set up well with no apparent rough spots or alignment problems. Anyway, I was never able to test on the district track so I just went with the set up from the pack race. Our car ran consistent 2,55 and came in second overall to a car that ran 2.53.

My question is should we set up different for a shorter, faster track? Should the set up be less steer or more steer into the rail? For the pack race I had about 4 inches of steer over 4 feet.

Thanks
 
The shape of the track is the bigger factor than the length. You can get away with less steer on a well-maintained track.

Wheelbase is another factor affected by track maintenance. You can get away with a shorter wheelbase on a better track, whereas a longer wheelbase will offer more stability on a lesser track.
 
4 inches of steer over 4 feet is a safe bet.

Your COM seems a little long. If you have access to a testing track, I would try to move the COM back a little bit to see if you can pick up some speed. You are going to need as much speed as possible. Their will be less separation of the cars on a shorter track.. More like less than one inch. Maybe .9 inches. You should be able to get a little more speed with a shorter COM.

What does the car look like? Why is the COM 1.25?
 
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Yeah, the COM is a little more forward than I wanted. I used zinc so I had trouble getting all the weight back. On the 42 ft track, with the alignment issues it had, I think the COM was o.k. but on the 35 ft I could have gone with less than an inch and been fine. Unfortunately, I didn't see the track until race day. The car is in my profile and was my first attempt. I'll definitely try to get a test run on the district track next year to get the alignment down. With this track I think less steer would have made the difference.
 
I agree. COM was probably a big factor. If I could've tested the night before I would've installed a new dfw wheel and axle. I wasn't that happy with my set up. It's tough when you know you won't be able to test.
 
Getting your CoM back another 1/2" is good for about 0.0066s on a 42' track (according to my calculations).

Using lead instead of zinc, or tungsten instead of either, will let you condense where all that weight is. I'm not sure if anyone has tested this and marked times, but I believe that having the weight more densely located is better. You can update this current car by drilling pockets behind and before your rear axles, weigh the car (with the wheels), and then adding lead to make up the difference.

Plenty other factors come into play. Wheel roundness and weight. Axle and bore polishing. Trueness of rear axle drilling/placement. Wheel to body friction on the DFW. Etc. etc.

If you KNOW that the district track is well set up, with no gaps or jutting seams, you can lighten up your steering and go with a way more aggressive CoM (like 1/2"). But as it's an unknown, go with standardized values (3/4" CoM, 4" over 4') and for the vast majority of cases, you'll win.
 
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Any of the racers here own and test on a 35' best track? I have been using this track and wanted to know what kind of times I should be expecting- I know there are a thousand factors that change from track to track but assuming a well maintained track what ball park should I be in with my times? My car is 5" wheelbase 3/4" com about 4 over 4 derby dads cheetahs and some max velocity straightened non-grooved axles, everything polished with dd4h kits and some dd4h special krytox some balsa fenders installed in front of front and back wheels. No washers or air sliders just some Sally Hanson nail protector at the hubs?
 
My car ran a 2.531 on a 35 ft track. Did I mentioned that was up hill in the snow?:D
Both ways no doubt haha- thanks guys for the times on the 35' track looks like I need to look at what is allowed in the basx class to see how I compare
 
So I looked up the basx rules and there are a few things I am doing against the rules- my wheels are 1.7 g each and I have fenders. However my axles are stock axles so the diameter is something like .87 which I think will definitely slow me down. This car is just for my pack race though - there is no district race or council race which is really annoying. I am about to finish the final prep of my car on the wheels and axles and tuning and see what she is runnin. Our families cars usually runs from 2.46 I believe was our fastest to 2.48 so I'm hoping to beat our track record
 
So I looked up the basx rules and there are a few things I am doing against the rules- my wheels are 1.7 g each and I have fenders. However my axles are stock axles so the diameter is something like .87 which I think will definitely slow me down.
If you put stock wheels onto that car, it would be legal to run in Box Stock (a class that doesn't allow purchased wheels or axles).

I just looked up the NPWDRL rules for Street Stock (which allows fenders and lightened wheels); the wheels are limited to 2g.

NPWDRL Street Pro rules do not mention a minimum weight for the wheels. But this class is populated with highly modified cars with three wheels and a pin.

I would recommend getting a set of stock wheels, polishing their bores, and submitting the car to Box Stock.

Good luck in your upcoming race, and in your race with us! :)
 
Thank you I just might do that! Looks like box stock would be the cheapest option for me because I just have to get new wheels- if I did street stock I would need new wheels and axles(92s) for a tighter fit. Now... Just have to convince the wife to be on board with sending in a car haha