Won Den & Pack Race

[iceman61]

Good news & bad news

Good news: My son's last year as a cub scout & we won the 2011 den & pack race again this year. Niby was even close this year & it was our fastest car ever following the 3 wheel rail rider steps again from the guys here at Derby Talk.

Bad News: Just looked over the District rules (race is weekend after this up coming weekend) and "all 4 wheels must touch" was the only thing different.

This is a killer unless I can figure something out quick. Can I plug the raised axle hole with glue & a tooth pick & redrill (1/16" lower) or do I strip the weight out of another car & make another one from scratch & hope for the best? Can rail riding be done with 4 wheels touching?

[Stan Pope]

Can rail riding be done with 4 wheels touching?

Oops!!!

Yes!

Set off-side front wheel to carry no more than 1/2 the front weight and align it parallel to the DFW, i.e. equal toe-out. Riding the inside edge of the off-side wheel (if you are allowed to camber) is good idea, too.

Getting the front wheels to distribute weight nicely may be a bit of a juggling trick. If you find that you can not get nice distribution with negative camber on the off-side front wheel ... there is little variation in height due to adding inside edge camber ... then switch to positive camber and choose whichever front wheel as RR which gives best control of weight distribution. If you used DFW indent to keep rear wheel off the rail, then either indent the new DFW OR realign rear axles.

[FatSebastian]

Can rail riding be done with 4 wheels touching?

This post from Sporty may help.

[3 Cub Dad]

Iceman,

No problems. Is your front dominant canted? If so, on the non-dominant side, you will need a half a degree more to make up for the raised hole. (just add a business card over the axle when using the axle bending tool. Start with the non-dominant rotated so that it is not touching, and slowly rotate it down, with toe out, to where it just makes contact with the ground. Make sure your drift hasn't changed on your aligment board. Four wheels will touch when sitting still and when you roll it back and forth on the check-in table, but when the wheel spins up to speed, it lifts itself from the track. Four wheels touching static, three wheels touching running.

3 Cub Dad

[quadad]

Is your front dominant canted? If so, on the non-dominant side, you will need a half a degree more to make up for the raised hole. (just add a business card over the axle when using the axle bending tool. Start with the non-dominant rotated so that it is not touching, and slowly rotate it down, with toe out, to where it just makes contact with the ground. Make sure your drift hasn't changed on your aligment board. Four wheels will touch when sitting still and when you roll it back and forth on the check-in table, but when the wheel spins up to speed, it lifts itself from the track. Four wheels touching static, three wheels touching running.
3 Cub Dad

That sounds like a new 'recipe' . I would be bit concerned that the NDFW might get spun up on occassion though, with an imperfect wooden track, taking some precious energy away. Do you normally setup for 4-wheel RR this way ? Or how would you do it from scratch (without having drilled a raised hole) ?

[*5 J's*]

Is your front dominant canted? If so, on the non-dominant side, you will need a half a degree more to make up for the raised hole. (just add a business card over the axle when using the axle bending tool. Start with the non-dominant rotated so that it is not touching, and slowly rotate it down, with toe out, to where it just makes contact with the ground. Make sure your drift hasn't changed on your aligment board. Four wheels will touch when sitting still and when you roll it back and forth on the check-in table, but when the wheel spins up to speed, it lifts itself from the track. Four wheels touching static, three wheels touching running.
3 Cub Dad

That sounds like a new 'recipe' . I would be bit concerned that the NDFW might get spun up on occassion though, with an imperfect wooden track, taking some precious energy away. Do you normally setup for 4-wheel RR this way ? Or how would you do it from scratch (without having drilled a raised hole) ?

Quadad - that is pretty much how I do it. You can calculate the axle heights for a four wheel rail rider, but ultimately you end up tweaking the negative camber of the non-DFW and the positive camber of the DFW. Tweaking such that both wheels touch - the DFW steers to the rail - and the non -DFW toed slight out away from the rail - while biasing as much front end weight as you can on the DFW (I believe we had something like 0.1 ounce on the non-DFW for our last build) . The added complication for our rules is that the tread must sit FLAT, so I am limited to about 1.5 degrees of cant which limits the range of adjustment.

[iceman61]

Interesting reading. We built the car in Nov. & for the life of me I can't remember how we set the front axles up & neither can my son. I did drill the rear holes for negative camber & 0 degree toe. Bit I'll have to get the car out tonight & check out what we did on the front axles. I do remember bending one front axle 2.5 degrees & turning it to give it just enuff toe in to gently drive it to the rail. 1" in 3 ft Im thinking. The raised wheel (1/16" higher) front end was sanded back by 1/16". I'll have to check the particulars on what I did to the raised front axle later tonight. I do have other axles I can swap out with if I need to change out either of the front axles. Maybe what I described so far will help until I can get the particulars.

[iceman61]

ok not remembering what I did was eating me up so I ran & grabbed the car. Here is how I initially set it up:
rear axles:straight
rear axle holes: drilled -2.5° camber
DFW axle: bent at 2.5° Not exactly sure about the bend angle
NDFW axle: straight
front axle holes: drilled straight

The DFW axle is installed with positive camber (bent axle) turn to give a slight toe in. It may have alot of positive camber because the raised front wheel is 1/8" high. The hole was drilled 1/16" higher than the other 3 & along with the positive camber it raises the wheel 1/8". It is fast right now. I hope it will be again with the corrections. It's this years pack winner & it beat our last years pack winner & 3rd place district winner.

[3 Cub Dad]

Iceman,

The positive cant on the DFW is why the non-dominant is higher than you drilled it. That is why you'll have to put a slightly greater, (3 degrees) positive cant on the non dom axle to get it to touch.

When I tweak the non-dom to just barely touching, the time differential is usually .002 or less from a "pure" 3 wheel.

@Quadad - yes, this is the "recipe" we've been using for four wheels touching, rail riding, when canting is allowed. My recipe's a little different than some listed here. when starting from scratch, all four axles are bent to 2.5 degrees. So far we've been undefeated in pack and district, (except by other brothers!), and have won a few in leagues too. HOWEVER, our previous pack and district really wasn't that competitive. Our pack this year was more competitive, but basically because I've been working and teaching a lot of them, so we're all doing pretty much the same thing. The district we're in now is supposed to be very competitive. District race is this Saturday, sooooooo, I'll hold back in going into detail of our current "recipe" until I see if its as competitive as I think. If we get whooped bad, we may have to go back to the drawing board. At least I'm the inspector for the District race, so I know it'll be a fair race!

3 Cub Dad