Newbie Question

[Tri Running Faster]

Hi Experts!

My son is in his first year of scouts and this is our first venture into Pinewood Derby. I asked if he wanted to make a car for fun or speed, and of course he wanted a fast car! So here I am trying to help him out and figuring our some basic things to do. After some reading I take it we have a strict pack. The pack is pretty large with probably 80ish kids so my thinking is they know there are probably some good builders and they want to keep all pretty competitive by limiting what can be done. Here are a few basics of the rules. You have to use the kit. Standard 5 oz weight limit, the axles have to be BSA and can't be bent, but can be polished, the wheels have to be the kit wheels with no alterations besides light sanding to remove flashing. All 4 wheels have to touch the track and be flat. The distance between the wheels has to be 1 3/4" (no shorter) and you have to use the slots to insert the axles. No washers and etc. There's more but that is the gist. So basically I was going to get the weight back as far as I can for him. How much weight can I put behind the axle with the standard measurements and slots? If I did 2 oz behind and 2 in front I would think the COM would be barely in front of the axle so should I be aiming for 1" in front of the axle, or does it matter as long as it is in front? I have no idea about the type of track as well. They did say they hired a company to run the race, so I guess it would be a decent one. Any other ideas you would like to toss out there I would appreciate as well. Thanks!

 

[robo4881]

Hi Experts!

My son is in his first year of scouts and this is our first venture into Pinewood Derby. I asked if he wanted to make a car for fun or speed, and of course he wanted a fast car! So here I am trying to help him out and figuring our some basic things to do. After some reading I take it we have a strict pack. The pack is pretty large with probably 80ish kids so my thinking is they know there are probably some good builders and they want to keep all pretty competitive by limiting what can be done. Here are a few basics of the rules. You have to use the kit. Standard 5 oz weight limit, the axles have to be BSA and can't be bent, but can be polished, the wheels have to be the kit wheels with no alterations besides light sanding to remove flashing. All 4 wheels have to touch the track and be flat. The distance between the wheels has to be 1 3/4" (no shorter) and you have to use the slots to insert the axles. No washers and etc. There's more but that is the gist. So basically I was going to get the weight back as far as I can for him. How much weight can I put behind the axle with the standard measurements and slots? If I did 2 oz behind and 2 in front I would think the COM would be barely in front of the axle so should I be aiming for 1" in front of the axle, or does it matter as long as it is in front? I have no idea about the type of track as well. They did say they hired a company to run the race, so I guess it would be a decent one. Any other ideas you would like to toss out there I would appreciate as well. Thanks!

I'm not an expert by any means, I would go with around 3/4" COM. Also the way some of the rules sound you could probably go with some wheel and axles from John. I'm sure some of the pros will give you some better answers than I could You can still Do a slight angle on your axles and have the wheels run "flat".

 

[CTDerbyDad]

Seems clear that you have to use the kit axles and wheels, but you can get great polishing supplies from DerbyDad4Hire. Hobby Lobby) if there's one near you also has good supplies.

The four touching rule can be frustrating. Can you drill your own holes or do you have to use the slots?

 

[Tri Running Faster]

Hi. Thank you for the responses. We have to use the slots. I think the spirit of the rules is to have it as close to standard items and use as possible. We worked on the car today and without wheels it seems to balance on a ruler right in front of the axle less than 1/2 inch. Probably about a quarter inchish+ so l guess 2 oz of weight behind is a bit too much? Uneducated question here... Isn't as long as the car balances in front of the rear axles (even if 1/16 of an inch) wouldn't it stay down on the track without tilting backwards? Thanks for the education.

 

[Ballistic Racing]

You're not worried so much about keeping the nose down as you are keeping it stable. The farther back the COM the less stable the car becomes.

 

[jjackrash]

I'm not an expert, but my personal experience is too much weight behind and you get "wig wag" and the car bounces back and forth the whole way down the track, unless you have a lot of DFW steer towards the middle.

 

[GravityX]

Tightening wheel gaps should help reduce the "wig wags". Too much rear wheel weight... lengthen the wheelbase, apparently not an option here. Otherwise, move some weight forward to help stabilize the car and adjust steer. Try to get a practice run if you can or find someone in your area with a track. Visit here to find other racers in your area. PM me if you want to be added to the map.

 

[jjackrash]

adjust steer.

I just reread, and I don't think he is allowed to adjust steer, as no bent axles are allowed, and four wheels must touch the track and be flat.

 

[Rebel Racer]

I just reread, and I don't think he is allowed to adjust steer, as no bent axles are allowed, and four wheels must touch the track and be flat.

Hi. Thank you for the responses. We have to use the slots. I think the spirit of the rules is to have it as close to standard items and use as possible. We worked on the car today and without wheels it seems to balance on a ruler right in front of the axle less than 1/2 inch. Probably about a quarter inchish+ so l guess 2 oz of weight behind is a bit too much? Uneducated question here... Isn't as long as the car balances in front of the rear axles (even if 1/16 of an inch) wouldn't it stay down on the track without tilting backwards? Thanks for the education.

Just a thought. Is it possible to cut your own slots so you can get your back axles a 5/8 of an inch from the back of the car? I'm sure this will help out a lot if you can do this. Also drilling holes in your slots to guide your axles could be an option. I'm no pro but from what I have learned on this site those are good options.

 

[DerbyDad4Hire]

You need to go with at most an once behind if you are running straight. You need to narrow the front on each side to insure the rear wheels can't hit the rail. You need to pray it runs without slapping the track. I personally would do a predrilled steer into it with cut slots.

 

[MrRoadWarrior]

I'd go with a COG 1" to 1.5" in front of the rear axle. Keep the weight centralized; read, then reread what DerbyDad just said; YouTube some good wheel and axel prep videos. And don't be afraid to scrap a few blocks of wood as you learn how do make a fast car. I went through 9 one year.

 

[jjackrash]

Only nine? Hehe. I'm pretty sure I have filled a big wood stove a few times over with my mistakes.

 

[Mojo Racing]

I've done that is less than a month.... so no worries there... at least pine is a renewable source... LOL

 

[CivilWarTalk]

You need to go with at most an once behind if you are running straight. You need to narrow the front on each side to insure the rear wheels can't hit the rail. You need to pray it runs without slapping the track. I personally would do a predrilled steer into it with cut slots.

This is the advice I've been searching for by golly for months! Thanks DD4H

I may have follow up questions tomorrow...

 

[Tri Running Faster]

Thanks everyone for the feedback and information. We raced this evening. We didn't move the wheels at all because it stated we couldn't and we needed to use the slots and keep the width at a minimum 1.75 inches between the wheels. At check in they weighted the cars (came in at 4.95 to their scale) and they measured the distance of the wheels along the length of the car. If we would have moved them it would have definitely been caught. They didn't measure between the wheels though so I guess we could have shorten the wheelbase up front, but didn't want to chance it so we stuck to the rules. We got the COM at about 7/8 of an inch and tried pre-drilling the slots for the axles. Ultimately we finished fourth which broken my tender hearted kid's heart as he thought he would win. 2 first and 2 seconds in 4 runs in a really competitive field. He had fun up to the awards part where he knew he won something and ended up just short.