Car design for a track with no center rail

[boiler]

The track our pack races on does not have a center rail, only side curbs. I think it is a SuperTrack http://www.supertimer.com/track/supertrack.html
The track starts at ~60° at ~4' and then curves to flat. http://www.supertimer.com/track/trackramp.html
After every round we have to go down the track and push the sections back together as small gaps have started to develop.

Since most car designs are for a car running on a center rail, what alterations would you make for a track like this?

How to design an edge runner versus a rail runner.

• We can run fenders, do you extend the fender and let it rub the edge instead of the wheel? Do you coat the fender with something like EZ Slide?
• Do you cant the wheels differently?

How to make a car that if it wins and goes to district can be used as a rail runner.
Any changes on how to weight the car since it has to rotate through 60°?

 

[Crash Enburn]

This has come up a couple times before. You can try searching for "reverse" (as in reverse the front and rear wheel canting and indentation) or maybe "edge" or "super track".

Basic gist of differences from a car made for a center rail track:

• DFW running negative cant (top closer to car than bottom ► /-===- )
• Steer to the outside of DFW
• Indent the rear wheel on dominant side by 1/16"-1/8"

One result I hit on my "reverse" search: http://www.pinewoodderbyonline.com/post/super-track-council-race-6271253

 

[ngyoung]

Crash pretty much summed up the wheel canting and steer for outer rail riding. I haven't read about if any of those that race on that type of track using fenders. If comparing riding on the wheel of the fender, you want the wheel touching. It is rolling along the rail vs the fender dragging along the rail.

I would also thing using a spacer and reversing the front wheel may gain some speed. Someone more experienced can hopefully confirm that though. I am just speculating. What is confirmed is what Crash suggested for the DFW. You can still run 3 wheels, raising the opposite front wheel if your rules allow.

 

[Redstone Racing]

If there isn’t serious competition in your pack, you may want to consider building the car as a typical railrunner (Cant the rears and drill the fronts straight). For the pack race I would run the front dominant wheel with a straight axle and use the bent axle to lift the ND wheel off the track. Granted, since the car is set up as a 3 wheel straight running car, it will bounce off the side rails some but probably no more than any other car. For a straight running set-up I would arrange my weight so the COM is around 1”. Considering the track sections tend to separate you may not realize the full benefit of running on the outside rail anyway. For the district race all you have to do is adjust your weight so your com is around 5/8” and move the bent axle to your dominant wheel. Reprep, set the steer and you’re ready to go. Keep it simple. Good alignment and axle/wheel prep will win most pack races.

 

[Crash Enburn]

Excellent point about continuing on to the District race. /images/boards/smilies/thumb.gif

 

[boiler]

The rules require us to use the slots for the axles.
Since there is no center rail...........
What if we flip the block upside down? How close to the track should we get? Would we get some sort of an aerodynamic advantage, i.e. ground effect?

If we cant the wheels for an edge runner for the pack meet, when we flip the car over, the wheels should be properly canted for the district meet as a rail runner?

 

[Crash Enburn]

A) Ride Height: I don't believe that there is much aero advantage to be had. However, there is a little speed gain to be had by having your CoM closer to the track. In that situation, the weight actually falls further than if the weight was placed high in the car. You can take your car down to under 1/8".

B) Flipping the car: Good thinking, but... If you have the car one way, your DFW is contacting the track. Flip it over, and the NDFW is the one on the track. Also, setting up for an edge runner, you want the *rear* wheels to have the narrower width. A rail runner is just the opposite. "Aha!" you say, "I'll flip it front to back!" Nope. Now your weight is on the wrong end, and you are steering with the rears.

 

[bracketracer]

How about if he flips it and swaps the DFW to the other side?

Better not have much overhang if you're building a lowrider though. Extended wheelbase?

Might be better to construct two cars?

 

[Crash Enburn]

Better not have much overhang if you're building a lowrider though.

No different than on a standard car. On a standard track, the rail is 1/4" high, and recommended height is 3/8"; for a differential of 1/8". If you only have to clear the bottom of the track, your car can run 1/8" of clearance. And, since the Supertrack has a gentler transition, it should be possible to go even lower w/o fears of contact.

 

[Kinser Racing]

There's really no gain. Yes I said no gain to be had with higher or lower weight, at least with the 1/4" tungsten cubes we use. I did this by using an unlimited I built with low weight placement. I flipped the car over, tuned it to turn the other direction and turned the guide pin, same exact times.