Removing bouncing

[JustSayin]

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.

 

[TRE]

More steer and tighter wheel gaps

 

[JustSayin]

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?

 

[TRE]

Thats a good start..if you are running stock axles you probably need more steer and tighter wheel gaps

 

[TRE]

How much steer is in the car

 

[JustSayin]

I'm running grooved axles with pro lite wheels

Over 4' about 1-2"

 

[TRE]

You have 2 inches in 4 feet

You need more steer

 

[JustSayin]

You have 2 inches in 4 feet

So 2" over 4 feet is good? Or should it be more?

 

[TRE]

You need 4 inches in 4 feet

 

[JustSayin]

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?

 

[TRE]

Yes canted rears matter...3/4 is fine

 

[Thinkin'Bout Racin]

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]

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?

 

[TRE]

The left rear should be about 65 right rear about 60 and front 15

 

[Racing358t]

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

 

[flockshot]

The left rear should be about 65 right rear about 60 and front 15

Is that with a right or left DFW?

 

[TRE]

That would be right steer wheel

 

[Racing358t]

Hey TRE, you giving away speed secrets with your weight distribution?

Scott

 

[TRE]

Hey TRE, you giving away speed secrets with your weight distribution?

Scott

no not really..even if you get close to that you are fast..

 

[Racing358t]

True that... I was just messing with ya.

Scott