Opinions on my build plan please

[CastleCrasher]

Can I get an opinion on my plan for my son's derby car please. We have a thin wafer style body with cut outs in the center. I have the body at the left front wheel cut 1/16" narrower than the rear, so we can 3 wheel with the left front being the dominant wheel to ride the rail, and hopefully keep the left rear from rubbing the rail. Going to use a tungsten canopy on top and cubes on the underside to set COG about 3/4" in front of rear, extended almost max wheelbase. Want to drill canted holes, but don't know what angles are best. Our pack track is an old 32' wood, the guy does his best to set up good and maintain it. District race is mix of wood and aluminum. Graphite for pack race. District rules allow oil but we must apply graphite to at least one wheel after inspection, so I assume to oil the rolling 3 and graphite on the raised left front. A big question I have is what angles to drill the axle holes. I'm thinking 2.5-3 degree camber for all 3 rolling axles? But then I recently learned people are doing toe also so that gets me mixed up more when searching for the answer. Last year we had a guy drill it and I don't know what he set it to. Ran straight axles and did good. So please, opinions on the overall plan and axle angles. This is my 2nd year of getting technical like this so if you guys could explain anything clearly. I'm still learning the lingo and different methods. We've got some tough competition in the pack, one guy is family of basically an industry legend and our district is tougher yet.

 

[Prozach2]

You can use oil, but you must add graphite to one wheel?? That's the strangest rule I've ever heard.

 

[CastleCrasher]

So the top part is the official rule set, and the bottom is like a supplemental FAQ document that further explains some things. My interpretation of the bottom part is that oil is allowed. Last year after the final inspection station, he said to apply graphite to at least one wheel then turn it into impound.

 

[Brian Stanley]

I think I would be careful here, you may show up and they add graphite to all wheels. Seems like a really strange rule though.

 

[CastleCrasher]

They let us put it on last year. I plan on bringing a set of graphite wheels and axles just in case.

 

[Prozach2]

I think I would be careful here, you may show up and they add graphite to all wheels. Seems like a really strange rule though.

They let us put it on last year. I plan on bringing a set of graphite wheels and axles just in case.

A rule or interpretation that bizarre seems suspicious. The day of the race, I bet a parent in the loop will have guessed the correct interpretation of the rule.

 

[Thinkin'Bout Racin]

They let us put it on last year. I plan on bringing a set of graphite wheels and axles just in case.

That sounds like a really good plan! Too much ambiguity in the rules and application to be sure what is going to happen.

 

[Prozach2]

I think I may be responsible for sending this thread off topic a little. My bad.

I’m not really qualified to give advice on your build. I’ve won a couple pack races, so I’ll give it a shot. You more experienced guys correct me if I’m wrong.

I’m not a fan of the tungsten canopy on top of the car. If you have the ability to make a weight pockets for cubes behind the rear axle, you might as well put cubes in front of the rear axle as well.

I use the silver bullet extreme to drill my holes. 3 degrees in the back, 0 degrees in the front, and raise one wheel.

Use a bent axle in the front to adjust steer. Lots of advice on this site on how to do that.

if you can, get your axles and wheels from DD4H.

don’t underestimate the importance of wheel gaps.

Make sure you do every step with your son. Have a great time, and take advantage of all of the bonding and learning opportunities. I always tell my boys, I’d rather people leave the race talking about how great my kids are than how great their car was.

 

[Thinkin'Bout Racin]

I think I may be responsible for sending this thread off topic a little. My bad.

Make sure you do every step with your son. Have a great time, and take advantage of all of the bonding and learning opportunities. I always tell my boys, I’d rather people leave the race talking about how great my kids are than how great their car was.

I am not a pro, so take that into consideration while reading my suggestions. (However, I did stay at a Holiday Inn Express last week )

Prozach2 - yes this thread headed down a path other than what was originally intended. However, it brought to light a very real possibility that a pearson that was thinking of running oil might end up with sludge on race day. It was a good conversation to have.

Also, I wanted to highlight your last paragraph. That is a very good philosophy! Work with, teach, encourage, and spend time with your kids! It will pay dividends both for the derby and later in life.


Castle - what Prozach2 has given you is solid information. Use it as a bases to start from. You will get various ideas and thoughts from others that can/will be a bit different. That is because there is no one perfect answer/build.

I will add that while the tungsten canopy will ultimately not be as fast as using all cubes placed in weight pockets cut underneath, with a little creativity and proper wheel weight placement along with a good alignment can produce a relatively fast car.

Alignment is critical ....let me say that again, alignment is critical!!! Yes it is that important.

There are a lot of very small things that will make a difference when all added together. But in my humble opinion, there are three main areas that should be focused on first.

1) Alignment - do whatever you can to get this as near perfect as you can.

2) Wheels and axles - if you can and want to, buy vendor cut wheels and use aftermarket axles. If your rules prohibit this, then pick thru as many wheels as needed to get a good set. Likewise, a true BSA axle can be made to run fast with some work. No matter which route you go ...do a good wheel and axle prep! Yes, it makes a difference.

3) Weight - weight your car properly. Learn how to balance it out and the reasons for doing this. Use the potential energy in your 5 ounces to your advantage. The gold standard (as of now) is to put about 2 ounces of weight behind the rear axle as a starting point. Build and weight your car according to what is needed by the rest of your build.

Read and read some more, there is a ton to be learned here. Almost all of your questions can be answered by reading. If you read, you will find that you learn a ton more than by just asking a question and then doing whatever the answer was. By understanding the concepts, you can teach your kids the reasons behind what you are doing while building a car. It takes more time, but the kids will notice that the extra effort pays dividends. They will also be learning valuable life lessons.

Remember to enjoy the time spent with your kids and be sure to have some fun while you are doing this! Good Luck!

 

[CastleCrasher]

Thanks for the feedback. No worries, I didn't think it got way off topic, all is relevant.

We got last place the first year, which really turned my son off of the derby. But I was able to get it through to him that it's partially because he didn't put much work into it, though I constantly made effort to. Last year we did a lot more work, had a good car that was also to his satisfaction. BUT, we, and our entire pack got beat by the only girl lol, she built the whole t(original)herself minus using the saw on the block. Week before the race, I saw her wheels and axles... Zero work, no weights. So I offered to fix it up, had a guy drill axle holes. She won. It was an awesome surprise for everyone except my son. Again I was able to get it through to him that she built her whole car, she deserved it for that effort. So he's more on board now with knowing that he has to work for it to win. So I've been doing the research and sifting it to him. The hard part is knowing the right bits of info to use where and when.

I'm curious, why rear cant only and FDW straight hole with bent nail? What is the effect of the FDW canted with straight axle? I have seen several sources saying rear cant/front straight and bent. I also just realized this year that we can run grooved axles, so that should help us too.

 

[Eric]

I also just realized this year that we can run grooved axles, so that should help us too.

I’m pretty sure we race in the same District as you. Every time I have asked about different lube besides graphite the answer I get is it needs to be a dry lube. Last year I asked about using Krytox since our Scout Store sells it, they said no once again. They usually make you lube one axle in the inspection line, but nothing in the rules that they can’t make you lube more than one if they see a need to.
As for the grooved axle, unless I missed a rule change for this year grooved axles are against the rules. They will not even allow a tuning groove in the head of the axle. All of this is coming from the Race Chairman.
I would hate to see anyone show up to the District race just to fail the inspection over a rule interpretation.

 

[CastleCrasher]

Small world if you are in the same district! I haven't spoken to any officials at all. I'm going purely off of what I read on the rule and FAQ documents. I just reread both documents before this reply, and I don't see anything specifically about grooves; and you can see above what it says about lubricant. Disclosure: I am looking at the 2019 documents, but as of a few days ago, I didn't see a 2020 version on the website yet but will check again. But your response reinforces why I have a plan B. Hope I don't sound rude, not my intention if I did sound rude.

 

[Eric]

http://www.wdboyce.org/document/2020-wotamalo-pinewood-derby-rules/196555

Here ate the 2020 rules, let me know if it does not open for you. I can get you the email of the Race Chairman if you would like it. He is pretty good about answering questions on rules. We have had success at the District race running DD4H graphite that he sells.

 

[CastleCrasher]

Thank you, link works. And yes that's our district too. I read the document and don't notice any changes, still nothing about grooves and lube. I'll print it and compare side by side tonight.