jcrouse

Here's the situation. The car in question is a pretty basic FTC3. I build a tweak station. It utulizes two pedistals and two Sunbeam scales. First I balance the front end of the car on a beam and put the scale under it and put the rear end on the pedistals (like a tweak board). Then I rotate the car 180 degrees putting the rear end on the scale and the front end on the pedistals. The fron and rear of the car area almost identical weights. I then do the same side to side and the weights are almost identical. This tells me that the overall front to rear and left to right distribution is good. Then I put a scale under EACH front tire and support the rear with the pedistals. Now the left front is carrying much more weight that the right front. When I rotate the car 180 degrees, support the front on the pedistals and each rear tire with a scale the right rear weighs much more than the left rear. To make up numbers its like the left front carries 3 pounds and the right front 1 pound and the right rear carries 3 pounds and the left rear 1 pound. I'm not sure how to even things out. If I mess around with the spring collars it will change my ride height which is already set where I want it. What should I be doing in this situation. Oh yeah, I've milled .250 off the center support and slid my batteries towards the drive shaft and I keep them in the front position. The car seems to push excessively in corners when under power. I know to much weight it transferring to the rear and that I probably need to go with heavier springs. I just thought I'd try to get the weight distributed evenly first. I hope all this makes sense.

Thanks,
John

ritchie

to add weight or lose weight from the right front you adjust the shock collar on the left rear. this is done for all corners. the ride height is the last thing to adjust by adjusting all four corner the same amount by say (just to pick a number) 1/4 at a time, this can be done, as i have done it. it will take what seems like forever
so be ready for that, just so you know, making the car equal on all four corners may not cure your pushing problem

RC Paperboy

Are you sure everything is perfectly level? It sounds like your board is slightly warped, or maybe your scales are not level, so when you turn the car to rest the long end on it, the problem is more obvious.

Sydewynder

It seems like your first test you are putting a beam across the 2 scales the weighing one end or one side.

On your second test, you're putting the wheels ie. left and right rear on the individual scales.

Your first test can give you a false sense that your car is balanced front to back and left to right because you are adding up the weights

Example of false balance:

Front left (FL)= 300 grams
Front right (FR)= 500 grams
Rear left (RL)= 500 grams
Rear right (RR)= 300 grams

so,

(FL) + (FR) = 300g +500g = 800g
(RL) + (RR) = 500g + 300g = 800g

Car is to balanced front to back.

(FL) + (RL) = 300g + 500g = 800g
(RL) + (RR) = 500g + 300g = 800g

Hmmm the car appears to be balanced left to right as well

In you second test when you put individual tires on individual scales (no beam connecting the scales), you noticed big weight differences.

I would go with the second test readings and try to move things like electronics around to balance things out. You have already started with moving the batteries. If moving things around can't get you to where you want, you need to add weights to the light corners to help even things out. Lead weights, coins, hot glue blobs will work.
BTW I would be more concerned with getting the left to right balance correct than the front to back. The side to side will dictate whether your car turns evenly left to right and whether or not it pulls to one side when you pull and let go of the throttle.
Pushing under power should really be fixed with suspension adjustments and not overloading the frontend with weights.

If the corner weights are even and the shocks are build correctly (same length) very little spring collar adjustment should be needed to get the tweak even. A small change in ride height is OK.

jcrouse

Wynder....you misunderstood slightly but got the point. In the first test I had a beam lying across one scale. However, your math example is spot on. That's what I was saying but I used 1 pound and 3 pounds as my numbers. I did play with spring collars a little and got it slightly closer.

John Stranahan

iTrader: (27)

John- your car is just out of tweak. First measure your Pedestals with a dial caliper and make sure that they are the same height. With the front of the car on the scales move the collar on the heavy wheel up a little and on the light wheel down a little untill the scales read evenly (At the back move the collar on the corner opposite the heavy wheel up and the other back wheel down a little). Now flip the car arond. If the scales do not read evenly within a few tenths of an ounce the weight in the car needs to be moved a little. If the front and back of the car weight the same, i would move weight back in the car to get about 2 ounces more in the back. This will eliminate some push.