Super Track - ugh!

[montanaDERBY]

Hi guys-
My son and his friend built their cars last Monday - they had the day off of school. 12 hours in the shop, including 50 min of class time. I printed out some of Doc Jobes lectures and some posts off of this site. They both have a great understanding of pinewood physics now. They were part of every step of construction (hence the 12 hours) and are proud of their cars.

We still have to install axles/wheels and align. I found out that our pack's track is a plastic "trough" style track. I found this out after hours of rail riding research, but BEFORE we started building our cars, thank goodness.

We read all of the posts related to this type of track. We narrowed the rear of the cars by 1/16" on each side, so that the rear wheels don't hit the sides of the track. Our bodies are from Maximum Velocity (Wing style). The axle holes were factory drilled with an extended wheelbase and a raised left front wheel. We drilled 1" lightening holes in the front and middle of the bodies, and have a COM of 1" in front of the rear axle. This is a bit conservative, but maybe ideal on the slick plastic track (from what we've read). We will be installing grooved MV axles (polished on Monday), and have to use the bsa wheels from the box.

As far as alignment goes, general concensus on this site says to align for a straight running car with negative camber on rear wheels and either neutral or negative camber on the DFW. Here are my questions...
1. Would flat aligned wheels be better to "track" on the slick plastic track surface? Or are the neg camber rear wheels way better?
2. Would a flat DFW be better, or a neg camber DFW?

If necessary, we will be bending the axles by notching them slightly, then bending in a vise with a light tap of a screwdriver above the notch.

Thanks a ton guys, this site is incredible!

[montanaDERBY]

Forgot to mention that we will run our raised front wheel inside out to fight friction when hitting track. I'd like to run our DFW inside out as well, but am afraid that any added body cone may be contrued as a bushing which is against the rules. Any thoughts there? Also, Our width limitations are 2 3/4"... I thought of mounting a thin plastic bumper guide under the car that sticks out farther than the wheels. I don't see any rules that would discourage such. This would negate the need for flipped front wheels. Would this be cheating or simple ingenuity?

[montanaDERBY]

Forgot another issue... Since we have to use the BSA wheels from the box, will running a negative camber axle (which pushes the wheel to the axle head) cause too much friction to be a benefit? Once again we are using maximum velocity grooved axles. We also bought mv pro stock wheels (before the rules were posted), and these wheels are trued on a lathe, and have coned inner and outer hubs, which would work better with negative camber. Can't use these wheels now, since the rules were posted.

I'm dissapointed that the rules were posted so late - a week before the race. A scout is supposed to be prepared. We researched and purchased the mildly tuned wheels with plenty of time to build. It seems as though our pack is determined to keep this a dumbed down race. The type of track they bought (plastic "hot wheels" supertrack) rings true to this idea as well. Certainly doesn't capture the pure essence of the historic "center guide rail" derby track, and all of the research, testing, and engineering that has been taking place since 1953.

[JEG68]

Please add me to the list of interested people on this topic. I am in the same boat as montana. Track used by our pack is SuperTrack.

After reading some posts on this site, I thought the main idea behind the negative camber was to reduce the amount of tread riding on and keeping the wheel away from the body. If this is the case, would it not make sense that these principles would still apply to a track that does not have the center guide strip.

Thanks in advance for your responses. I am new to the board and in the last month my building skills have increased 10 fold. Of course my skills were pretty low to begin with.

[FatSebastian]

Please add me to the list of interested people on this topic. I am in the same boat as montana. Track used by our pack is SuperTrack.

As evidenced by the lack of responses to Montana, there aren't very many people experienced on the SuperTrack. This topic is the most informative I've seen. Hopefully more people will share their experiences as the SuperTrack becomes more common.

If this is the case, would it not make sense that these principles would still apply to a track that does not have the center guide strip.

Camber reduces the amount of tread touching the roadway, which applies whether there is a central rail or not. But how much benefit reduced wheel contact has with a plastic surface...

[montanaDERBY]

Thanks for the reply, FS. The crickets were beginning to drive me nuts.

I'm struggling with this one still... have to make a decision in a couple hours because the boys will be arriving at the shop to align and tune.

Two issues I keep stumbling on...

1. On outer guide rail track, the rear must be narrower than the front. We narrowed our bodies at the rear by 1/16" to compensate. Negative camber on the rears will bring the bottom edge of the wheel further out from the body, closing the small gap we produced. Running the front wheels flipped on a body cone would increase front width, and still keep within width rules, but this brings up issue #2...

2. Stock BSA wheels have the "tread" on the outer surface of the rim. When running flipped (inside out) wheels on a negative camber the notched "tread" creates a very noticable rumble of friction - even at a low degree of camber.

At this point my plan is to run a flat DFW with a very minute negative camber angle to the axle - large enough angle to bring the wheel to the axle head, but small enough to keep the wheel flat. I'm guessing around <1.5 degrees. This slight angle should also help with front alignment tuning. I'll run the raised wheel with more negative camber for the sake of creating a bit more outer track guide clearance for the rear wheel behind it.

I'll explain all of this to the boys, and see if they want to run the rear wheels flat or on a negative camber. Regardless, the rear wheels will have to run with the lettered sidewall to the outside in order to keep the rear wheels tucked.

Any ideas on how to create a simple body cone? Our cars are already painted with a sweet 4 color automotive paint job (left over paint from some jobs in our shop), so the new cone will stick out like a sore thumb. I'm thinking a laminated 1/32" ply cone, shaped with a dremel after CA glue lamination. Space out the laminations for the axle hole.

[mebetree]

From the link FS gave "The irregularities of the track were so bad, the "better" your car was the "worst" you finished. Bottom line is large, fat, center-weighted cars took home the prize as they were able to stay stable. "

That was my guess after reading a description of the track.

Cars with too light a front end are going to dance, badly. But I wouldn't suggest center weighting either as it would allow the car to spin easier on that point and just go back and forth hitting each side. I would instead suggest weighting it like a barbell. Feather light in the center with mass on each end. Maybe go 60-40 or 70-30 if you want to get aggressive but not too light in the front.

I would also go negative camber and have the front be wider than the rears so its likely only one wheel touches the side if it ends up rubbing the whole way down. I'd also be leery of running a wheel lifted because the sides are so low. Too high and it might climb right over the ridge.

I could be wrong though. Just my two cents.

[FatSebastian]

DFW with a very minute negative camber angle to the axle - large enough angle to bring the wheel to the axle head, but small enough to keep the wheel flat.

I wonder if there is any benefit in introducing minute DFW camber in this situation (flat tread contact). We would likely try to run negative camber on the rears and no camber on the DFW while trying to navigate straight ("trying" meaning that any residual tendency for steer should be slight and tend toward the side of the DFW to avoid impacting the non-DFW?). Based on what others have said about the SuperTrack, we'd also likely try for a CoM placement that was not overly aggressive. We'd certainly minimize the gap between the wheels and body (0.035" max) to help maintain directional control.

Any ideas on how to create a simple body cone?

We've yet to try it, but others have.

I'd also be leery of running a wheel lifted because the sides are so low. Too high and it might climb right over the ridge.

Insightful - not too high!

[gpraceman]

FS is right that not many members here have had experience with that track. That manufacturer has been around a long time, but there are still far more center lane guide tracks out there.

With the really steep start section on that track, I would think that you would not want to go too aggressive with your COG towards the rear, for stability sake as the car transitions to the flat. If you do a raised wheel, I agree that you do not want to raise it by much, as there have been several reports here about cars jumping lanes on that track.

The other thing that you may want to stay away from is building an extended wheelbase car. The stop garage can be rather harsh on the cars and is more likely to mess with the front wheel alignment on an extended wheelbase car.

[tkp]

My sons have been running on this track- all lengths, for about 8 years now- Please email me your phone and an offline conversation will no doubt assist and hopefully it's not too late.
Or additionally, I just sent you my contact info.

Any good points, we'll bring back to this discussion.

TKP

[montanaDERBY]

Well, Race Day has come and gone. My son and his friend each built a car to race on the Super Track. Both cars were identical (with minor paint differences) except my son wanted to camber his front wheels to match the rear. His friend, Oliver, wanted flat front wheels. The flat front wheels prevailed, and brought home a 4th place trophy out of about 55 cars. Best time was 2.58. Oliver's car got a 4th with 2.63. My son missed out on standings with a 2.85. Here are some photos... the first is the type of body cone we made from laminated 1/64" ply. The lightening holes were covered with clear monocote.




Thanks everyone for your help and advice. We were majorly concerned with friction from the side rails on this track. That is why we widened the front end, and ran our wheels flipped on the front with a body cone on the DFW (the left front wheel was raised). Turns out these cars were aligned so well that they rarely, if ever, hit the side rails. The winning car was a three wheel flat-aligned car.