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!

Removing bouncing

Discussion in 'General Pinewood Derby Discussion' started by JustSayin, Oct 30, 2019.

  1. JustSayin

    JustSayin Hammering Axles

    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    USA
    What do you recommend to help with a car that bounces back and forth? I made it a rail rider with a wheel raised. The balance point is about 5/8 in front of rear axle. All axles are straight except for the one in front angled toward the center rail. We have a fast car, however, it can be much faster if I can eliminate the slamming.

    Could it be possible that the car is not balanced (left to right)? I make sure the weights are centered. With lifting the front wheel, do I need to counter balance that? I'm out of answers. This has been my nemesis. Thanks all.
     
  2. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    More steer and tighter wheel gaps
     
    Charles Studer and 5KidsRacing like this.
  3. JustSayin

    JustSayin Hammering Axles

    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    USA
    Now I've been reading some of the threads about weight on the DFW. Should I weigh all 3 wheels? Does the DFW need to be at about 15 grams? Would that help with the wiggle?
     
  4. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    Thats a good start..if you are running stock axles you probably need more steer and tighter wheel gaps
     
  5. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    How much steer is in the car
     
  6. JustSayin

    JustSayin Hammering Axles

    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    USA
    I'm running grooved axles with pro lite wheels

    Over 4' about 1-2"
     
  7. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    You have 2 inches in 4 feet

    You need more steer
     
    Charles Studer likes this.
  8. JustSayin

    JustSayin Hammering Axles

    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    USA
    So 2" over 4 feet is good? Or should it be more?
     
  9. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    You need 4 inches in 4 feet
     
  10. JustSayin

    JustSayin Hammering Axles

    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    USA
    Thanks. Do you suggest going 3/4" in front of rear axle or a little closer. And does drilling the rear axles holes at an angle, with the jig I have matter as much?
     
  11. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    Yes canted rears matter...3/4 is fine
     
    JustSayin likes this.
  12. Thinkin'Bout Racin

    Thinkin'Bout Racin League Racer

    Messages:
    459
    Likes Received:
    210
    Trophy Points:
    43
    Gender:
    Male
    I agree with TRE, more steer to start with. 4" may be enough, but if this is running on a rough track with scouts, you may need more. 6" of steer will cost you a few thousands of a second over 4" of steer. HOWEVER, each time the rears touch/bang the center rail it costs you about a hundredth of a second.

    I always recommend starting with a bit too much steer and then sneaking it back. Each car is a bit different. I have some that only want about an inch 1 over 4' and then some that like over 8" in 4'. I have all of my scouts start at 4-5" over 4 feet.

    And yes, canting the rears is important also. You might, I say MIGHT be able to go slightly less than 3/4". But NOT until you get the car stable!!!! Moving the weight back will make the car harder to tune, likely it will be less stable. Once you get it running straight and solid, then think about moving weight.
     
    JustSayin likes this.
  13. JustSayin

    JustSayin Hammering Axles

    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Location:
    USA
    So I just picked up 4 mini scales to weigh each wheel separately and these were the readings I got.

    Left rear - 72.87 grams
    Right rear - 48.22 grams
    DFW (right) - 21.19 grams

    Am I to assume that this could be a large factor that would contribute to the wiggle I get when the car runs?

    Should the rears be equal? Or are they off because of the DFW?
     
  14. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    The left rear should be about 65 right rear about 60 and front 15
     
  15. Racing358t

    Racing358t Pinewood Ninja

    Messages:
    50
    Likes Received:
    33
    Trophy Points:
    18
    Gender:
    Male
    Location:
    Illinois
    All good advice so far.

    Try tuning (turning) your rear axles. No axle is straight. A misaligned rear either via a bad drill or bent axles (in the wrong spot) will cause on to wiggle also.

    Could also look for better wheels. Spin the wheels on a 090-093 pin gauge so as to look and feel for runout or vibrations. If you have the pinewood derby tool to check runout of the wheels that is even better than the visual check. Wheels with vibration, laterel runout or lots of circumferential runout can contribute to wiggles.

    Scott
     
    Reecedad, Jimmy & his 2 Kids and TRE like this.
  16. flockshot

    flockshot Rail Runner

    Messages:
    75
    Likes Received:
    21
    Trophy Points:
    8
    Gender:
    Male
    Location:
    Michigan U.S.A.
    Is that with a right or left DFW?
     
  17. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    That would be right steer wheel
     
    flockshot likes this.
  18. Racing358t

    Racing358t Pinewood Ninja

    Messages:
    50
    Likes Received:
    33
    Trophy Points:
    18
    Gender:
    Male
    Location:
    Illinois
    Hey TRE, you giving away speed secrets with your weight distribution? :)

    Scott
     
    Charles Studer likes this.
  19. TRE

    TRE PWD Royalty Pro Racer Pro Race Winner

    Messages:
    1,426
    Likes Received:
    322
    Trophy Points:
    83
    no not really..even if you get close to that you are fast..
     
    Racing358t likes this.
  20. Racing358t

    Racing358t Pinewood Ninja

    Messages:
    50
    Likes Received:
    33
    Trophy Points:
    18
    Gender:
    Male
    Location:
    Illinois
    True that... I was just messing with ya.

    Scott
     
    TRE likes this.

Share This Page