wheel, axle, and car tuning

[yzboy250]

4 questions:
1)Which axle will give me the best performance .092 or .094 diameter?
2)If the axle is undercut to reduce friction should I bend the axles and set up for a rail rider or would this cause the wheel to have issues with the bore of the wheel hanging up on the grooved areas?
3)Our pack track is aluminum how much drift should I have for best performance?
4)How do I do a drift test flat and push the car or on a slight angle so the car doesn't need any effort from me for more accuracy(please provide instructions if you don't mind)?

Thank you for the help

 

[Vitamin K]

1) A lot of people run the .092s, but somebody else is probably better equipped to answer that one.

2) The overriding opinion here is that you should not bend your rears for rail-riding, but drill cant and use straight axles, instead. For bending your front axle, if you're using a thick aftermarket axle, you may wish to cut a bend groove to get a sharper bend angle. Either way, the speed groove should still rest in the proper position within the wheel bore.

3) Your drift numbers will vary depending on your car's CoM, but 4" over 4' on the tuning board is a good starting point.

4) Build a tuning board so that you can let your car roll down hill and watch how it behaves. A piece of 1' x 4' MDF works well. Attach a yardstick to the other side so you can watch how your car behaves when running against a center rail.

 

[ngyoung]

1. Go with 92s.

2. The only axle you should be bending is the dominant front wheel for rail running. The rear axles should be straight with the axle holes drilled at the desired angle, typically 3* negative canter.

3. The baseline is typically 4" of steer over 4'

4. If you can find a smooth flat board or maybe use a tall bathroom mirror. I used a mirror and just layed it on the floor and propped up one end with something to get a slight ramp. I use a bubble level to make sure it is level side to side. I marked 1 inch increments across the bottom edge. I set my car up in the top corner and made a few reference marks to make sure I have the car pointed straight and just let the car roll. Takes a few times to get your release right to make sure you let it go the same way each time.

 

[ngyoung]

The jargon can get a little confusing if you are new, there are 2 separate grooves that can be used. There are speed grooves that are cut into the area where the wheel rides that reduces the contact area between the axle and wheel bore. If you are getting the 92 axles from DD4H then that groove will have plenty of area on either side of the groove for the wheel to ride without catching on the edge of the wheel hub. Bending the axle doesn't change that. Then there is the bend groove which is just a thin cut in the axle to get it to more accurately bend where you want. If you make a bend groove it helps to make sure you don't end up putting a curve in the section where the wheel rides. You want the portion the wheel rides on to be as straight as possible. This pic may be more helpful then trying to write out the whole process:

 

[yzboy250]

This then leads me to one more question oil or graphite?

 

[ngyoung]

If it is allowed, use oil.

 

[Eliminator Racing]

I sent in two cars with 94X Pro Axles and the cars where slower. I believe the 94 where made for Awana wheels, but I had to try them.
Go with the .092s from DD4H.

 

[yzboy250]

Here is the car for this year. Currently the car has a COM of .85 inches in front the rear axle. The weight at the front axle is .75 oz and the car with all wheels and axles is 5.000 oz total. Is this a good COM or should I try to move it back more? My son wanted raindrops this year.

 

[Vitamin K]

Here is the car for this year. Currently the car has a COM of .85 inches in front the rear axle. The weight at the front axle is .75 oz and the car with all wheels and axles is 5.000 oz total. Is this a good COM or should I try to move it back more? My son wanted raindrops this year.

In my opinion, .85" in front of the rear is a fine CoM for a scout race. Unless your pack is super-competitive with a lot of dads who frequent Pinewood Derby boards. /images/boards/smilies/wink.gif

 

[yzboy250]

In my opinion they are very competitive the same guys son wins 1st every year closely followed by his nephew.
Top 5 breakdown from the last race:
Place time speed(mph)
1st 2.4195 211.4
2nd 2.4333 210.2
3rd 2.4525 208.5
4th 2.4683 207.2
5th 2.4920 205.2
My son about middle of the pack roughly 30 kids currently. If there is any suggestions you can give to get him closer to the front of the pack it would be appreciated. I attached their pack rules below. Thanks

Our pack rules are as follows:
MATERIAL: All cars entered shall be constructed from the "Official Grand Prix Pinewood Derby Kit" (referred to below as “the kit”, Diagram #1). Materials from the kit can be supplemented with officially licensed material only and as described below.

SIZE: As determined by the official “box” during the Registration and Inspection, race cars shall not be longer than 7 inches, nor wider than 2-3/4 (2.75) inches. Underside ground clearance of at least 3/8 (0.375) inches and inside wheel to wheel clearance of at least 1-3/4 (1.75) inches is mandatory. The overall height of the vehicle shall not exceed 2-3/4 (2.75) inches.

WEIGHT: Race cars shall weigh no more than five (5.000) ounces total weight as determined on the official scale during the pre-race inspection and registration. Weight can be added to the car and will be considered part of the car for purposes of all measurements. All weight must be securely fastened to the car by permanent glue, nails or screws, and not by "sticky substances", such as tape, or tack spray. Weights shall be passive, meaning non-moveable, non-magnetic, non-electric, non-sticky, etc. All weight mounted to the rear of the car must not exceed below the underside clearance of 3/8.

WHEELS: The car shall roll on approved BSA Pinewood Derby wheels, only. Alternate colored wheels and “old” or “new” wheels (Diagram #2) will be acceptable. The wheels shall turn about the axle nails. Wheels cannot be altered to a beveled, conical, thinned, edged or knifed condition (Diagram #3). Wheels may be sanded and polished or lathed to remove mold casting burs and surface imperfections. The small detailed marks on the edge of the wheels must remain visible around the entire circumference. Upon truing of the mold cast marks, the wheel cannot weigh less than 2.4 grams. There must be at least four wheels on the car, however, it is not required that all four wheels make contact with the track surface. Each wheel must be mounted on an axle, on the outside of the car, in the vertical position. No part of the car or any attachment to the car may be capable of coming into contact with the track other than the wheels (no guide pins allowed). Winning cars are subject to a post race inspection to verify the wheels do not weigh less than 2.4 grams.

AXLES: Cars must use axles provided in the "Official Grand Prix Pinewood Derby Kit". The axles must be firmly affixed to the wood on each side of the car body. They can be moved forward or back to accommodate different wheel base. Polishing and/or modifications are allowed as long as the overall diameter is not reduced below the 0.084 inch requirements. Grooving of the axles is allowed as long as the non-grooved portion of the axle meets the minimum 0.084 diameter requirement.

CANTING/CAMBER (Axles/Wheels): Camber, also known as “Canting”, is the inward or outward tilting of the top of the wheel from the true vertical of the wheel (Diagram #4a). Toe-in/out is the inward or outward direction of the wheels (Diagram #4b). Camber and Toeing of the rear wheels are prohibited. Toe-in/out with a combination of camber is allowed on the front wheels for alignment purposes. Camber can be checked by placing the car on a flat surface and providing a light source at the bottom of the wheel.

LUBRICANTS: Oil, Graphite, and Teflon "white lube" will be allowed for lubricating the wheels. Over-application of lubricant which results in excessive shedding onto the track is not allowed. Once the car is impounded after the inspection and weigh-in, it may NOT be re-lubricated. Lubricants may not foul the track!

GRAVITY POWERED: Cars must be powered by gravity only! This means no engines, rubber bands, wind up motors, springs as used for propulsion, rocket motors, CO2 cartridges, thermo-nuclear reactors, plasma boosters, rodents on hamster wheels, or any other thrust generation or enhancement devices.

 

[Vitamin K]

In my opinion they are very competitive the same guys son wins 1st every year closely followed by his nephew.

My son about middle of the pack roughly 30 kids currently. If there is any suggestions you can give to get him closer to the front of the pack it would be appreciated.

Oh, you've got a no-camber rule! Those are...fun.

- So, for your rears axles, you're going to want to set them to about 1 degree of negative camber. This is not visually perceivable, but will still get the wheels to migrate to your axle heads. Make sure you have a proven method for getting your rear alignment dead-on. The Silver Bullet tool is popular among denizens of this forum. Make sure you have a way to verify the alignment too...look up Lightninboy's thumbtack and triangle method.

- For your front axle, you can do standard bent axle for toe-in and positive camber. Since the rules don't say you can't, make sure you raise that non-dominant front wheel.

- Since you're racing against another "Pinehead", you might consider going with a more aggressive CoM, say 5/8".

- For wheels, your easiest solution would be to go with the BASX or BASX pro wheels from DD4H's site, since they are guaranteed not to weigh less than 2.4 grams.

- .092" grooved axles sound like a solid bet.

- Definitely do oil. Krytox. Search around this site or others regarding how to use the oil, or buy the instructional DVD. For axle pre-treatment, Jig-A-Loo is the most popular product, though there are alternatives.

 

[microbrush]

Our pack rules are as follows:
MATERIAL: All cars entered shall be constructed from the "Official Grand Prix Pinewood Derby Kit" (referred to below as “the kit”, Diagram #1). Materials from the kit can be supplemented with officially licensed material only and as described below.



AXLES: Cars must use axles provided in the "Official Grand Prix Pinewood Derby Kit". The axles must be firmly affixed to the wood on each side of the car body. They can be moved forward or back to accommodate different wheel base. Polishing and/or modifications are allowed as long as the overall diameter is not reduced below the 0.084 inch requirements. Grooving of the axles is allowed as long as the non-grooved portion of the axle meets the minimum 0.084 diameter requirement.

How is it that he could use the .092? They do not originate from the "Official Grand Prix Pinewood Derby Kit" Could he even use the Revel ones? Does't sound like it to me.

 

[Vitamin K]

Our pack rules are as follows:
MATERIAL: All cars entered shall be constructed from the "Official Grand Prix Pinewood Derby Kit" (referred to below as “the kit”, Diagram #1). Materials from the kit can be supplemented with officially licensed material only and as described below.



AXLES: Cars must use axles provided in the "Official Grand Prix Pinewood Derby Kit". The axles must be firmly affixed to the wood on each side of the car body. They can be moved forward or back to accommodate different wheel base. Polishing and/or modifications are allowed as long as the overall diameter is not reduced below the 0.084 inch requirements. Grooving of the axles is allowed as long as the non-grooved portion of the axle meets the minimum 0.084 diameter requirement.

How is it that he could use the .092? They do not originate from the "Official Grand Prix Pinewood Derby Kit" Could he even use the Revel ones? Does't sound like it to me.

You're right! I completely misread that! Looks like he'll have to use BSA Grand Prix axles. But he can groove them himself, if desired! Thanks for the catch!

 

[yzboy250]

What is the part number on the can or an image if possible for JigALoo? I have a TSC and a Home Dept that cary different part numbers for this stuff. I just ordered the wheels and axles today. Thanks

 

[ngyoung]

Looks like whoever wrote those rules did some research on league racing.

What VK suggested for wheels is the best option. For axles you should still be able to use the Revell official BSA axles that are sold at hobby stores. They are still officially licensed BSA parts and the axles don't have the crimp marks that the scout shop axles have. This at least lets you skip having to file off the crimp marks.

Your CoM is on the conservative side but still not a big deal if you don't feel there is a good way to move it back more without wrecking the car.

One trick that you can take advantage of with the slop between the axle and wheel bore is to still canter your rear axles 1*. This still allows the wheels to sit flat on the floor but give better consistency to migrate out to the heads.

It looks like you have already drilled your axle holes though so maybe keep that in your back pocket for next year.

How much time do you have? I assume if you are considering ordering 92 axles and oil you have some time. Even more then getting good axles and wheels, the polishing process I feel provides the biggest boost in speed. You can get the kits from DD4H and follow the wheel and axle polish process and you should be right up there with the top scouts in your pack. You can also assemble your own axle and wheel polish supplies locally, depending on how much you already have it may not save money.

High grit sandpaper for the axles can be found at Hobby Lobby that goes from 400-12k. Using their 40% off coupon you can get the pack for about $5. Novus2 can usually be found at motorcycle shops or Ace hardware to polish the wheel bore using a q-tip stalk chucked in a drill. Bare minimum those 2 steps should be done to the wheels and axles.

Now falling deeper down the rabbit hole...the next level stuff you will want the step 2 part of DD4H's wheel bore prep, Red Rocket. It is sold with the wheel prep kit or separately. A slightly lesser substitute would be Liquid Glass but it is usually $30 for a bottle at Advance Autoparts but it also works great on your own car so you don't have to use it just for PWD.
The most readily available option to substitute Jig-a-loo is Dupont Chain Saver. That is for coating the axles before applying the oil and installing the wheels. You can find the process if you dig around in the forum. Jig is hard to find since it is no longer being distributed in the US so any left is leftover from before they stopped.

 

[Vitamin K]

Guys, make sure you read microbrush's catch of my recommendations. According the rules, he can't run the aftermarket axles. (Although, it's highly unlikely that they'll be able to tell if you do...but that's a matter of conscience.)

 

[yzboy250]

I was going to bend the rear axles I bought a press for it at the local BSA store. Time wise we got some but not an excess. I never cared much for fast just good looks but my son is of the opposite feelings regarding this he likes good looks but wants speed first. I can refinish the car with the raindrop graphics in roughly 4 hours so I have wrecked the bottom and started adjusting the weight to the back of the car more. Is 5/8 COG in front the axle to aggressive causing it to wheel hop and bounce off the track or will that be the best location for the COG with respect to the times listed earlier for 1-5 place? Should I use any old axle for the wheel that doesn't touch the ground?

 

[Obsessedderbydad]

I was going to bend the rear axles I bought a press for it at the local BSA store. Time wise we got some but not an excess. I never cared much for fast just good looks but my son is of the opposite feelings regarding this he likes good looks but wants speed first. I can refinish the car with the raindrop graphics in roughly 4 hours so I have wrecked the bottom and started adjusting the weight to the back of the car more. Is 5/8 COG in front the axle to aggressive causing it to wheel hop and bounce off the track or will that be the best location for the COG with respect to the times listed earlier for 1-5 place? Should I use any old axle for the wheel that doesn't touch the ground?

That would be a derby worx tool. Highly recommend against bending your rear axles. Also you did put axles in your holes which is good, but you're going to need something over the paint where your wheel hub is going to touch the body. That paint will slow you down. You would be extremely lucky to find jig in a store in the US. 92x's if allowed. .85" in front of rear axle is fine for scouts as said before, but you can go less and make your car faster. 5/8 is not too aggressive. 1/2 is too aggressive for scout races and not needed. Every answer you're asking can be found via the search button on the forum. They have been answered 100s of times.

 

[yzboy250]

Thanks for catching the axle issue I will just take the stock BSA ones to my uncles machine shop and modify them to match the .092 axle dimensions w.r.t the undercut areas and head adjustments of course less the fact that they are not the same diameter. Its harder to put metal on than take it off. I got the COG to .620 if front of the axle exactly. I also took into account the ordered wheels will be slightly lighter than the factory ones when measuring. Based off obsessedderbydad's post why wouldn't I wan't to bend the rear axles? Also would the paint mater I use automotive products as I paint custom cars for a hobby. The paint material is House of Kolor.

 

[ngyoung]

I usually prep 4 wheels and if everything goes right save the 4th as a backup in case there is a crash.

How hard does your clear coat dry? Most are too soft and create more friction then not.