Dismiss Notice
Welcome to
Pinewood Derby Online, a forum for questions and discussions about everyone's favorite gravity powered racers!
CLICK HERE to register as a member today for full access to the forum, it's fast, simple, and absolutely free!

Critique my son's build. Looking for last minute setup (weight distribution) tips

Discussion in 'General Pinewood Derby Discussion' started by DeoreDX, Feb 5, 2020.

  1. DeoreDX

    DeoreDX Hammering Axles

    Messages:
    6
    Likes Received:
    10
    Trophy Points:
    3
    Gender:
    Male
    My son is an AoL this year so I've been pretty hands off with his build. He's usually been more concerned with how the car looks more so than how it places though we did get 2nd place in the pack two years ago. Last year he lost in a tie breaker for the top 3 in the den and our den eventually went on to sweep the pack 1-2-3. This year he is determined to make as fast a car as possible to try to win it all. Rules are pretty loose. You have to use the axles and wheels from the kit. You have to use the block of wood in the kit. Overall dimensions and weight limits. No springs or mechanical assist devices. No bearings or bushings or washer. After that it's anything goes. We talked about what makes a good design, weight placement, aerodynamics, etc. We bought some TXchemist weights to give us the most flexibility from the weight placement. His design is a slight wedge that is almost flat. He was originally at 28+g on the FDW after adding all his weights. We decided to put his wedge on a diet. I routed the inside of the body out for him some (Not comfortable with him and the router) and removed around 8g of material for him. With two 3.7g weights on the rear drive side these are his numbers:

    DFW: 23.31g
    DSRW: 52.60g
    NDSRW: 64.24g
    Total: 140.15g (140.00 when weighted as a whole)
    Wheelbase 4.8"
    Rear wheel 5/8" from back of car.

    There was a .15g difference when weighting the car as a whole v. weighing each wheel individually. I only have one scale so I attribute this to the blocks I use to hold the car up under the wheels not being the exact thickness of each other compared to the scale. We have some small .5g and 1.7g weights we will use to get his car up to weight at weigh ins. Probably going to remove a little more material since he will be putting some vinyl under the car for aerodynamics. Shooting for 140g and let him bring it up to weight at checkin.

    [​IMG]

    There are 3 of the 19.6g (0.69 oz) bars behind the rear wheels for a total of 2.07oz and the three smaller 7g (.25oz) bars biased towards the DFW side in front of the axle.

    [​IMG]

    Our track is an aluminum track and the gaps between the sections are never 100% smooth and even. The car he placed 2nd two years ago with was slow off the line compared to others but never wobbled and would always pass everyone at the bottom of the track. That car that had 4" of steer but wasn't weighted as aggressively and the rear wheel was 7/8" from the end of the car with a 4.625" wheelbase but had fenders.

    [​IMG]

    Looking for feedback on his car as we make the last minute preparations for the race this weekend. Should we risk getting more aggressive with the weighting? We can always remove more material from the inside. We could stretch the wheelbase too if we think we need more stability. Unfortunately we will not be able to run the car on the track beforehand so we will have to just show up and run on race day. I asked him is he was planning on painting it and he said "Only if it will make it faster". Any feedback on if paints actually help any with wheel friction?
     
    KyleBCostco likes this.
  2. KyleBCostco

    KyleBCostco Rail Runner

    Messages:
    83
    Likes Received:
    18
    Trophy Points:
    8
    Gender:
    Male
    Put super glue around where hub of the wheel will hit the body. Sand smooth with super high grit.
     
  3. Charles Studer

    Charles Studer Council Champion Pro Racer

    Messages:
    269
    Likes Received:
    108
    Trophy Points:
    43
    Gender:
    Male
    Location:
    Colorado Springs
    Sand Smooth....very
     
  4. KyleBCostco

    KyleBCostco Rail Runner

    Messages:
    83
    Likes Received:
    18
    Trophy Points:
    8
    Gender:
    Male
    Very very
     
  5. Thinkin'Bout Racin

    Thinkin'Bout Racin National Contender

    Messages:
    523
    Likes Received:
    282
    Trophy Points:
    63
    Gender:
    Male
    If you still have time, I would cut out a weight reduction pocket in the nose just like you did in the main body. 23 grams is still plenty heavy on the DFW. My guess is that you could get that down to 18 grams or so by cutting a pocket? I might consider cutting your first pocket toward the rear further. Go as far as you can. If you epoxy your weight back in, you can gain back any strength that you might take out by cutting the pocket. Also, how thick is the top where you cut out the pocket? Add the weight back inside your first pocket. Keep it to the rear as much as possible. Based on what I am seeing, shoot for 10-14 grams difference on the rears.

    If your alignment is good and your wheels are decent, you can easily go to 16 grams or less on the DFW. Depending on the condition of the track and what your competition is, helps to determine how aggressive you want/need to go.

    Did you notch the FDW 1/16"? If not, I would strongly encourage this also. Make sure you get 4"-5" of steer in it over 4'. Make sure to bore prep!

    Good luck.

    Love the Porsche!
     
    Last edited: Feb 6, 2020
  6. Charles Studer

    Charles Studer Council Champion Pro Racer

    Messages:
    269
    Likes Received:
    108
    Trophy Points:
    43
    Gender:
    Male
    Location:
    Colorado Springs
    Good luck
     

Share This Page