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So what is this "Bounce Back" thing anyway?

Discussion in 'General Pinewood Derby Discussion' started by Carl ODay, Jul 20, 2020.

  1. Carl ODay

    Carl ODay Pinewood Ninja

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    I have been reading through these forums for a while and have seen references to the "bounce back" method as it relates to a tuning board. In the posts that reference the method, all there is is a reference... Would it be possible to get a full explanation of what the bounce back method is and how it benefits the cars we are building?
     
  2. OneSpartan

    OneSpartan Pinewood Ninja

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    It is a measure of how far the car bounces back when it hits the foam at the end of a tuning board. For those that do not have tracks, you can use it to approximate the speed of a car by how far a car can bounce back. The amount of bounce back is obviously impacted by a number of factors - how long your tuning board is, angle of board, density of foam, angle at which the car hits it, shape of the front of the car, etc. Everyone's set up will be different but I knew if a car bounced back > 25 inches on my tuning board, it was reasonably fast.
     
  3. Roadrunner

    Roadrunner Pinewood Ninja

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    I imagine you would have a guide between the wheels, to keep it running straight?
     
  4. OneSpartan

    OneSpartan Pinewood Ninja

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    I do not. Others may do it that way. My guess is you would not want to run the guide all the way to the foam as it could rub on the guide in unintended ways when it bounces back.
     
  5. Roadrunner

    Roadrunner Pinewood Ninja

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    Can’t argue with your success. I’m just thinking of ways to get consistent results. I keep the angle of my tuning board small. The cars roll very slowly down the board. ( yeah, they do that on the racetrack too. But that’s a different conversation ). I’d never get a 25” rebound at the speed I check the drift. Maybe I’m rolling to slowly...
     
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  6. Mojo Racing

    Mojo Racing National Contender Pro Racer

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    Bounce back is an okay indicator if the car is going to run fast. Sometimes you will see it dragging down the board or what have you.

    What it does not do, though, is show if you car doglegs, wiggles, or rubs the transition...

    If a tuning board is all you have, that is what you use, but if you have access to a track, run it
     
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  7. OneSpartan

    OneSpartan Pinewood Ninja

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    The angle on mine is admittedly too much, but I never wanted to change it because I had it fairly dialed-in to a speed correlation. It is a piece of mirror propped on one end with a 4 ft level. I think the important piece is to have a consistent, repeatable setup and you'll get a feel for how a fast car rolls and also, how it sounds.
     
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  8. Roadrunner

    Roadrunner Pinewood Ninja

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    Well, this is the most I’ve seen about bounce back. I hope we answered ops’ question. But every time I talk to you guys, I end up thinking that I really need a test track. In addition to my tuning board. That’s probably the way to go...
     
  9. Mojo Racing

    Mojo Racing National Contender Pro Racer

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    Not everybody has a track... There are some fast racers who do not own a track. If you don't have one, do everything you can to your car with your tuning board and pay attention to your race times...

    But... if you want to spend hours (and hours and hours and hours) working on your tuning, to wring every thousandth of a second out of your car, you definitely need a track. There is so much more that you can learn about your car, seeing it as it happens. The cameras will not show you everything that your car is doing to scrub the speed you have left in your car.
     
  10. Roadrunner

    Roadrunner Pinewood Ninja

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    Mojo said: But... if you want to spend hours (and hours and hours and hours) working on your tuning...

    Yeah. That sounds like me.
     
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  11. Jimmy & his 2 Kids

    Jimmy & his 2 Kids National Contender

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    I also learned from another pro the ability to tune rears to an extent on the board. No track here either. after setting your steer... little tweaks of the rear axles all the way around. If there is enough natural bend in the axle that is never truly straight you might be able to work it enough to see an increase on how far it bounces back. Both my cars are tuning board warriors. Its tedious though. Gain isn't very much but I have gained almost .75" before though usually .25-.5". But it is a similar concept as tuning the rears for that last speed on a track. (oh and be careful... this can affect steer. double check it after your done fussing over the rears)
    so in short... I wanna track... need a track... want a track... need a track. track track track track. :eek::D
     
  12. Mojo Racing

    Mojo Racing National Contender Pro Racer

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    It happens! LOL
     
  13. DerbyDad4Hire

    DerbyDad4Hire Administrator Staff Member 25+ Pro Race Wins! National Champion

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    Never heard of it.
     
  14. Ballistic Racing

    Ballistic Racing Workshop Leader #1 Ranked in the USA Pro Race Winner Pro Racer

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    Yep! What Mojo said. I’ve tried it once & wasn’t too impressed, too inconsistent for me. Take notes on EVERYTHING you do, send in & watch the slow mo’s. Keep repeating, you’ll get faster.
     
  15. Carl ODay

    Carl ODay Pinewood Ninja

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    Thank you all for the input - it is much appreciated.
     
  16. Reecedad

    Reecedad League Racer

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    I think my opinion on this has changed recently.
    I noticed recently that when my cars returned home from a race, they always bounced better on my board. So evidently the amount of oil will have effect on the bounce. I also noticed that by changing the steer and hitting the foam in a different location can change the bounce. But most important, before my car goes down the track I always start on my tuning board. I’ll adjust my steer and then tune the rear axles until my car bounces the furthest. At that point I’ll take the car to my track and tune the rear axles again. The axles have always changed location to reach my best times.
    If you don’t have a track to test on then obviously do as much as you can on the tuning board but if you have access to a track- use it.
     
  17. Racing358t

    Racing358t Rail Runner Pro Race Winner Pro Racer

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    It's like any other tool. It is just to help a person do a job but there are not absolutes in it. I have had cars bounce back really good and others not quite as good. My MA isn't the best bouncing car but is respectable on the track and has even won a few races. My basx and SS bounce better yet are way slower. But generally all my cars bounce within a couple inches of each other except for the Fat wheel bearing car (it bounces way better than the oil cars). So to me I use it as a tool. If I put together a car and it bounces 6" less than normal then something is probably wrong.

    Scott
     

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