Need help finishing a four on the floor car.

[Larry c]

My friends son has no Dad so I was asked to help him build a car by this Friday's weigh in. The little guy has a Mom and three sisters and is a great kid that needs some confidence. Here is what We've got so far.

Rules
basic rules plus these
All 4 wheels touch at the same time
standard BSA wheels and axles. You cannot remove material from them or change their shape. You can sand and polish them to remove burs.
Beyond that, I think everything is up the creativity of the boys.

Below is a picture of our first run at building something. I did order the pro driller tool from pinewood. Plan on canting the rear axles 2.5 degrees. As for the front we were going to shoot for a rail car with the passenger side axle bent to allow a 3-4" steer into the rail over a 4 foot run. The other front I was going to either keep straight or bend also slightly toed out and try and get it to where it's barely touching. The wheel base will end up around 5 3/8". Also the tires have been prepped (lathed and coned). We will use pledge with the pipe cleaners and then graphite. I'm planning on distributing the extra weights in the pocket to get the COG between 3/4" and 1 ". I have extra tungsten on the way. Not sure how best to place the weights from side to side weighting and how to secure them to the wood. The vinyl is a sticker used on airplane wings that will wrap around the entire car.
Any help is much appreciated as I've tried to read everything I could on the forum and appreciate the information I've gained so far.

 

[T-Bone Racing]

If you plan on building a second car, and can make the adjustment, a 3 degree cant is typically what you want in the rear.

To secure the weights, try running a piece of tape from the end of the weight pocket, and then wrap it around the back and leave a little bit on the top. You can also use a little bit of school glue to secure them, this way, you can get them out.

Another huge thing for scout cars is the rear axles. Rotating the position after they’re installed makes a difference! If you can, tune them and see if the car sounds better rolling on a table of some sort.

 

[bracketracer]

Just for clarification, regarding the wheel rules you said "You cannot remove material from them or change their shape." but then you said you have lathed and coned wheels. Are you sure those are going to be accepted?

When you go to set the steer on a four touching car, set it first with the fourth wheel not touching. When you get the number you're looking for, then lower the fourth wheel until it rolls but does not change the steer you set.

 

[Keith A.]

Just for clarification, regarding the wheel rules you said "You cannot remove material from them or change their shape." but then you said you have lathed and coned wheels. Are you sure those are going to be accepted?

When you go to set the steer on a four touching car, set it first with the fourth wheel not touching. When you get the number you're looking for, then lower the fourth wheel until it rolls but does not change the steer you set.

Whoa, is this actually effective? With all other things being equal, does a rail-rider with 4 touching actually perform better than a proper aligned straight car?

 

[karlaj]

Whoa, is this actually effective? With all other things being equal, does a rail-rider with 4 touching actually perform better than a proper aligned straight car?

What bracketracer said sounds right. Tune the car w/ 3 touching, get the wheel barely touching but not affecting the steer (guessing weight on 4th wheel is below 1 gram). Rail-riding vs straight? I'm pretty new here but unfortunately, I can tell you from experience that straight is slower b/c our car bounced around the rails alot. But I'm happy to be shown otherwise.

 

[TRE]

You will never get the car to run straight..a rail rider is always faster

 

[bracketracer]

Whoa, is this actually effective? With all other things being equal, does a rail-rider with 4 touching actually perform better than a proper aligned straight car?

You've heard the expression that the shortest distance between two points is a straight line? Well, a rail rider is your best shot at running a straight line down the track. Regarding three vs four wheel touching, you'll give up about .010 sec on a 42ft BestTrack having the fourth wheel down but if the rules require four touching, I feel the alignment technique I posted gives the best result. If you have four mini scales to set the car on, you should see a little less than the bare wheel weight on that fourth scale. We had to run stock weight wheels so the bare wheel would be around 2.5g, the scale would show 2.0-2.1g. If you don't have enough weight showing, the wheel may not roll reliably for check in.

 

[Scott Porter]

I have to deal with this, this season. How do you lower the fourth wheel to just barely touching? And not effect the steer? Thanks!

 

[T-Bone Racing]

I have to deal with this, this season. How do you lower the fourth wheel to just barely touching? And not effect the steer? Thanks!

I’ve never done this before and I’d like to hear what other racers would do for this, but I would drill the axle hole just a little bit higher on the non dominant side. The main question would be, how much higher? I would just practice it on a different block or something like that, or just keep testing the drill until on planks until one comes out with the 4th wheel barely touching.

 

[CastleCrasher]

I haven't had to do this either but I'd agree with T-Bone's suggestion: drill 4th hole slightly higher than the DFW-steering wheel, practice on spare block first. If using a drilling guide jig that includes a raised hole (example: Pinewood Pro PRO Driller Tool), maybe try using the raised hole guide but put varying number of really thin shims under block until right distance is found (usually raised hole guide is considerably higher). On the spare block just drill the rears like normal and mount a spare set of wheels, drill your DFW hole and mount wheel, tune your steering angle, then try multiple holes for 4th wheel until result found, you should only need one block.

 

[T-Bone Racing]

I haven't had to do this either but I'd agree with T-Bone's suggestion: drill 4th hole slightly higher than the DFW-steering wheel, practice on spare block first. If using a drilling guide jig that includes a raised hole (example: Pinewood Pro PRO Driller Tool), maybe try using the raised hole guide but put varying number of really thin shims under block until right distance is found (usually raised hole guide is considerably higher). On the spare block just drill the rears like normal and mount a spare set of wheels, drill your DFW hole and mount wheel, tune your steering angle, then try multiple holes for 4th wheel until result found, you should only need one block.

This is what I would do. And CastleCrasher’s reply reminded me that you only need one block because you can refill the whole. I’ve plugged up holes with toothpicks and drilled a second time on the other side of the car, but for the non dominant side, filling the hole and drilling again won’t mess it up.

 

[Scott Porter]

Thanks for the input guys. My mind is going in another direction though. High wheel is usually drilled high to insure carrying the wheel, but if drilled straight across and if I put an aggressive steer axle in one front side, the other side will carry a little. I had a practice drill block with holes as straight across as I could drill, I put a steer axle in one side and straight in the other and the straight axle wheel is partially rolling, but might not pass tech as always touching? If I use a less aggressive steer axle maybe it would, but might not steer as well?. Not sure? I am inclined to drill the race block with the straight axle side a fraction lower than the steer side and see what happens. Likely will have to tweak tings a little. Heck last year my cars were built as four wheels flat (as per rules last year) and the cars warped and ended up being three wheel touching cars without building them that way, so who knows how this thing will go by race time in a couple of months. Thanks again!

 

[Loud2ns]

I agree with your theory. The dfw will push the ndfw up so you don't want to drill it higher. You'll want it a smidgen lower. Then adjust the bend of the ndfw axle to barely touch. I would make sure it is bent straight down(6 o'clock) so not to influence the steer much.
This is the method I would try if in your shoes. Let us know what you go with and how it works.

 

[DerbyDad4Hire]

Here you go...

 

[Scott Porter]

Thanks John, Very helpful and good to have it in video too. Best!

 

[Loud2ns]

I defer to what John said. He has way more experience than I do.