First pinewood derby experience!! And now a few questions...

General discussions for car and semi-truck racers.
DerbyDad325
Apprentice
Apprentice
Posts: 17
Joined: Wed Feb 28, 2018 3:32 pm
Location: Sweetwater, TX

Re: First pinewood derby experience!! And now a few questions...

Post by DerbyDad325 » Fri Mar 02, 2018 11:55 am

Vitamin K wrote:
Fri Mar 02, 2018 10:53 am

I like the Pro-Axle guide for putting axles into slots. I use a sacrificial axle to open up the slot (with the guide attached) before I attach my real axle with the wheel.

One thing to make sure of first is that the slot is deep enough. I've found a few blocks with shallow slots. I have found that a blade from a jigsaw (held with the hand) is the perfect thickness to fit into the slot and deepen it a bit.
I'm looking at getting one of those Pro-Axle guides next year. I borrowed one from a scoutmaster on the practice day while trying to adjust the black car so it wasn't fishtailing so bad (weight really close to the axle). Since we must always use the nail slot, I can now see how they are useful to keep the nail from trying to pop out.

I actually did use another nail to try to open up the hole first. Although next time I'm going to do it before we make any cuts on the car block.
This year I did it after the car paint was finished, and I guess the car wasn't 100% cured and the clear coat smeared big time which moved the front number graphic on the blue car. I tried to smear it all back flat again and it felt like trying to spread putty. Next time I guess I need to let the clear coat dry more than over night.



User avatar
Vitamin K
Pine Head Legend
Pine Head Legend
Posts: 1099
Joined: Sat Apr 20, 2013 7:26 pm
Location: Spotsylvania, VA
Contact:

Re: First pinewood derby experience!! And now a few questions...

Post by Vitamin K » Fri Mar 02, 2018 11:59 am

Sounds like you've done your due diligence with prep on the cars.

Since you're running bent rear axles, there's a lot of speed to be either lost or gained depending on how well you've eliminated any potential toe-in or toe-out in the rear. Have you done any testing for that?



DerbyDad325
Apprentice
Apprentice
Posts: 17
Joined: Wed Feb 28, 2018 3:32 pm
Location: Sweetwater, TX

Re: First pinewood derby experience!! And now a few questions...

Post by DerbyDad325 » Fri Mar 02, 2018 12:17 pm

Speedster wrote:
Fri Mar 02, 2018 11:10 am
If you counted 4 sections then it was a 42' Best track.
That is good to know. I'll try to make sure of the number of sections next time.
Speedster wrote:
Fri Mar 02, 2018 11:10 am
I have a 35' Best track as does our Pack and District. The cars run 29'10". The best time at our District race is 2.4XX. More common time is 2.5XX.
I never realized how much fun making and racing these cars could be! I can see how having your own track would be a blast! I've never seen my son so excited about an event as he was winning all his heats for this race. I was just glad to see him cheering for the scouts next to him when his car wasn't running. I figure after we race a bit more and competition picks up more, then maybe I can convince him we can work more on making a unique looking car rather than a car only for speed.

Wow I can't imagine a 2.4xx and 2.5xx time!!! What more do they change to get to those times? Is that with stock full-width tread wheels?
Or are they using those razer thin speed wheels?

I'll have to see if it is allowed next year, but thought about using a fixture with a razer blade to turn the outside of the wheels to get them true to the axle bore (essentially to make sure the wheel is a perfect circle around the axle). Possibly help with speed if the wheel is perfectly balanced.
Speedster wrote:
Fri Mar 02, 2018 11:10 am
Strangely enough, Our Pack's 4 lane Best track has a Champ timer and the District's 4 lane Best track has a MicroWizard timer but the times recorded are very close. The District folks have quit this year and on March 10th the District will be using our Pack's track. The District actually uses 2 tracks. Our Pack track will race all the cars first. The 8 Fastest cars then move to a 4 lane, 40' Freedom track and race 8 more times. It's actually very exciting. The car that wins on the shorter Best track does not always win on the longer track - but he usually does.
Is there a menu in the software where they select the track length? I looked at some videos on the Grand Prix software (sorta looks like what they used) but didn't see any mention of track length selection in their online videos.
I would be curious just ask them what they have it set for next time



DerbyDad325
Apprentice
Apprentice
Posts: 17
Joined: Wed Feb 28, 2018 3:32 pm
Location: Sweetwater, TX

Re: First pinewood derby experience!! And now a few questions...

Post by DerbyDad325 » Fri Mar 02, 2018 12:24 pm

Vitamin K wrote:
Fri Mar 02, 2018 11:59 am
Sounds like you've done your due diligence with prep on the cars.

Since you're running bent rear axles, there's a lot of speed to be either lost or gained depending on how well you've eliminated any potential toe-in or toe-out in the rear. Have you done any testing for that?
We were running bent rear (2.5) and bent forward (1.5).
I mainly just rolled the car down a board with a center tape line to get the slight steer I wanted.
I did notice on the black car when i rolled it back, it was as if the car was making a sharp turn to the right (passenger side) using a front left (driver side) dominate wheel touching with the front right (passenger side) wheel lifted.

So it would slightly drift right when rolling forward but make a hard right (passenger) turn when backing up.
when I spun the front left (driver) dominate wheel nail so the bend was down instead of up the bottom of the front wheel leaned in instead of out (rail ride) and then the care would roll backwards straight instead of turn. That was how I left the black car.

I didn't read much on how to check toe in or out, so that is something I would really like to learn more on.
Any advise how to, or where I can read about it?



DerbyDad325
Apprentice
Apprentice
Posts: 17
Joined: Wed Feb 28, 2018 3:32 pm
Location: Sweetwater, TX

Re: First pinewood derby experience!! And now a few questions...

Post by DerbyDad325 » Fri Mar 02, 2018 12:43 pm

Vitamin K wrote:
Fri Mar 02, 2018 8:34 am
If you break 3 seconds on stock wheels and axles, that's dang good.

That said, remember that track times vary widely, even for tracks of the same length and same brand. Heck, the "speed" of a track can change just by setting it up in a different location.

Don't get too hung up comparing times from other tracks.
Well, the scoutmaster has told me that the record on this track was 200mph by a girl scout, so I'm really hoping to help the boy scouts win back the track record. So the track is the same one. He told me he has seen 2.4 runs before (not sure if on this track though), but I'm wondering if maybe they ran the track shorter 1 year???

I'm just trying to figure out with all the changes we made, is it really possible to go from 2.94 to 2.45 just by something we are missing?
Maybe fine tuning more toe-in toe-out??? Or 3 aftermarket perfect tires?

Not sure what we are missing..?

Hense, I was wondering if maybe they could have the software setting wrong? I just don't like to assume that a scoutmaster would not set it right since the person running it looked VERY good at it. I just can't figure it out since not even the scoutmaster cars were that fast. In fact, one of them said they might buy an axle bending tool next year, but many of the cars for the older kids I saw had canted rear wheels. But like I said, no other kids got under 3.0000 so it just doesn't make sense to me. If the track record was 200mph, wouldn't it be more typical to have some 175mph runs on races the following years?

I could post a video, but not sure if that tells you much on the track length watching from the side.



User avatar
Vitamin K
Pine Head Legend
Pine Head Legend
Posts: 1099
Joined: Sat Apr 20, 2013 7:26 pm
Location: Spotsylvania, VA
Contact:

Re: First pinewood derby experience!! And now a few questions...

Post by Vitamin K » Fri Mar 02, 2018 1:32 pm

DerbyDad325 wrote:
Fri Mar 02, 2018 12:24 pm
Vitamin K wrote:
Fri Mar 02, 2018 11:59 am

Since you're running bent rear axles, there's a lot of speed to be either lost or gained depending on how well you've eliminated any potential toe-in or toe-out in the rear. Have you done any testing for that?
I didn't read much on how to check toe in or out, so that is something I would really like to learn more on.
Any advise how to, or where I can read about it?
There are a few approaches.

The most basic way is to roll the car forward and backwards and watch the way the wheels migrate on the axles. Ideally, both wheels will move out towards the axle heads, both in forward and in reverse. If the wheel moves in towards the body of the car instead of out to the axle head, that indicates toe-in or toe-out that needs to be adjusted by gently rotating the axle.

The next method is the "Lightninboy Method" which involves exotic tools like a section of shelf, a thumbtack and a speed square. You're looking for the same thing as the first test, but it takes the DFW out of the equation, and the square keeps the car moving straight forward or backwards.

Finally, there is Stan Pope's bias weight system, which uses a set of clip-on weights and a tuning board to bias the weight of the car towards one back wheel or the other, in order to see if either wheel is exerting undesired steer on the car's back end.



Speedster
Pine Head Legend
Pine Head Legend
Posts: 1540
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: First pinewood derby experience!! And now a few questions...

Post by Speedster » Fri Mar 02, 2018 3:15 pm

It doesn't matter whether you have Positive cant or Negative cant on the dfw, you still are rail riding if you have narrowed the body of the car 1/16" behind the Dfw and set the wheel with toe-in. Positive is preferred because of amount of friction and a possible mis-alignment in the track sections. Hopefully, with Positive cant the wheel will ride over it without damage.

Winning cars at our District races are usually shaped like a Hershey bar. As much wood as possible is removed which allows you to place more weight where you need it. Picture this: You're racing your Center of Mass (where the car balances). The higher up the hill you can get the COM the faster the car will go. Back wheel alignment is critical. You do not want the back wheels trying to steer the car.

I highly recommend you get Troy Thorne's book," Build a Winning Pinewood Derby Car." You can order it from Fox Chapel Publishing. There are no pictures of Big, Bulky cars in the book. It's all about speed. The book will put you on the right track after reading it a few times and then you can start fine tuning things. I invite you to view the pictures of cars at the Mid America race. It's what your son wants that is important. If he wants to win the District race then he needs to build a car that has a chance to win. He needs to do each and every operation as perfectly as he can and know how to do it. Yes, the answers are here on Derbytalk but Troy Thorne will give you a quick head start. Lot's of pictures in that book too. You can read it with your son. I think he will enjoy it.
Best
Bill



DerbyDad325
Apprentice
Apprentice
Posts: 17
Joined: Wed Feb 28, 2018 3:32 pm
Location: Sweetwater, TX

Re: First pinewood derby experience!! And now a few questions...

Post by DerbyDad325 » Fri Mar 02, 2018 3:45 pm

Vitamin K wrote:
Fri Mar 02, 2018 1:32 pm
The most basic way is to roll the car forward and backwards and watch the way the wheels migrate on the axles. Ideally, both wheels will move out towards the axle heads, both in forward and in reverse. If the wheel moves in towards the body of the car instead of out to the axle head, that indicates toe-in or toe-out that needs to be adjusted by gently rotating the axle.
This is basically what I did rolling it back and forth, and both times the wheels would move towards the nail head so I thought that was ok.
Vitamin K wrote:
Fri Mar 02, 2018 1:32 pm
The next method is the "Lightninboy Method" which involves exotic tools like a section of shelf, a thumbtack and a speed square. You're looking for the same thing as the first test, but it takes the DFW out of the equation, and the square keeps the car moving straight forward or backwards.
I saw a post somewhere about this using the thumbtack to lift the front end so no front wheels needed.
I thought about doing this method, but since method 1 passed (wheels moving towards nail heads) and the lack of more time, I skipped this.
Vitamin K wrote:
Fri Mar 02, 2018 1:32 pm
Finally, there is Stan Pope's bias weight system, which uses a set of clip-on weights and a tuning board to bias the weight of the car towards one back wheel or the other, in order to see if either wheel is exerting undesired steer on the car's back end.
That method I have never heard of. Would probably need to see a tutorial to see exactly to what degree they are adding weight. Sounds pretty in-depth.



User avatar
Vitamin K
Pine Head Legend
Pine Head Legend
Posts: 1099
Joined: Sat Apr 20, 2013 7:26 pm
Location: Spotsylvania, VA
Contact:

Re: First pinewood derby experience!! And now a few questions...

Post by Vitamin K » Fri Mar 02, 2018 5:08 pm

If you're getting migration to the axle head both forward and back, you're probably pretty good.



DerbyDad325
Apprentice
Apprentice
Posts: 17
Joined: Wed Feb 28, 2018 3:32 pm
Location: Sweetwater, TX

Re: First pinewood derby experience!! And now a few questions...

Post by DerbyDad325 » Fri Mar 02, 2018 5:47 pm

Speedster wrote:
Fri Mar 02, 2018 3:15 pm
I highly recommend you get Troy Thorne's book," Build a Winning Pinewood Derby Car." You can order it from Fox Chapel Publishing. There are no pictures of Big, Bulky cars in the book. It's all about speed. The book will put you on the right track after reading it a few times and then you can start fine tuning things. I invite you to view the pictures of cars at the Mid America race. It's what your son wants that is important. If he wants to win the District race then he needs to build a car that has a chance to win. He needs to do each and every operation as perfectly as he can and know how to do it. Yes, the answers are here on Derbytalk but Troy Thorne will give you a quick head start. Lot's of pictures in that book too. You can read it with your son. I think he will enjoy it.
Best
Bill
Thanks! I'll look into that book. I can certainly learn more about rear wheel alignment.
This year my son wanted an Indy car. I wasn't sure how I would weight it, but it turned out I was able to squeeze in a very heavy low profile 1 1/8" tungsten disk right in front of the rear axle to give it the rearward COG it needed. I actually ended up drilling it by hand very carefully (after the whole car shape was already finished) while holding the car in the other hand. I had actually planned on just putting weight in the back but realized after its shape was final, that the disk could actually fit.

If not for that, I think he wouldn't have had a chance. I wasn't sure how the car would fair against the pack, but luckily it turned out well outpacing them all. After seeing how much faster mine was than his... I think he will have an idea now of what he will need to make if speed is his main concern.
I was really hoping to see some cars faster than him, just to weigh his reactions to losing a race. But with no district race this year for our pack, we will just have to see how it turns out next year. It is too bad they don't have pinewood derby races somewhere monthly! They sure are fun!

I built my car for pure speed and it was very thin in the body (below the axle slots) with the humps over the axle slots to prevent the body from cracking. I am not sure if I'll do the same design next year, but it was beating other cars by car lengths at times, so time will tell.

Thanks Bill for the quick replies and for the reading material recommendation!
This is certainly a great place for advice, with a great group of commenting members!



DerbyDad325
Apprentice
Apprentice
Posts: 17
Joined: Wed Feb 28, 2018 3:32 pm
Location: Sweetwater, TX

Re: First pinewood derby experience!! And now a few questions...

Post by DerbyDad325 » Fri Mar 02, 2018 5:49 pm

Vitamin K wrote:
Fri Mar 02, 2018 5:08 pm
If you're getting migration to the axle head both forward and back, you're probably pretty good.
That is what I was hoping for. Thanks for confirming that :thumbup:



Post Reply