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Old 07-10-2006, 12:11 AM   #1
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Default Chassis Balance

I've always been under the impression that it's important to keep a chassis balanced from side to side, and front to rear. It's one of the first things Martin Crisp mentions in his XXX Main book. The problem is, I have to add a ton of weight to my car to get it balanced, making it considerably overweight. Is this normal?

I have a Corally RDX with a Novak GTB and 4300 motor, and I'm using an updated motor bulkhead which moves some of the motor weight closer to the centerline of the car. Even with all that, I have to add 50+ grams to the right side to get the chassis to balance. And that's without running fans or heatsinks or anything fancy on the car.

So, what should I do? Is it okay to pile the weight on there to get the car even on both sides, or should I just let it be a bit off and tune the car around it? At some point, adding more weight will hurt more than it helps, right?

Last edited by syndr0me; 07-10-2006 at 12:09 PM.
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Old 07-10-2006, 03:36 AM   #2
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That's a question I always wanted to ask... not sure how to formulate it... but what is the limit? How to keep the low center of gravity when adding weights? Is it OK to make other holes on the chassis to grab the weights with countersunk screws? Or keep using double side tape?

Thanks a lot,
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Old 07-10-2006, 04:12 AM   #3
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I have staring at my RDX for the last hour trying to figure out the lipo balancing issue as well when this bit of help came to me. I am running the futaba 9550 servo and have it mounted with the servo ears/tabs on the outside or motor side of the servo mounts. This may not work with a standard profile servo, but there is room to mount the servo farther towards the center line of the car, further reducing the amount of balast needed. I haven't mounted my servo like that before but I imagine all you would have to do would be flip the ball stud on your servo horn to the other side. Just sharing a thought witcha'.
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Old 07-10-2006, 09:39 AM   #4
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This is why the FK'04 will be the easiest chassis to set-up, imo.
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Old 07-10-2006, 11:02 AM   #5
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your not alone bro. i got a yokomo and i have a 3800 on the battery side .i measured the battery and ,my electronics it seem that my bettery is like almost a 100g more than may electronics..the battry is somewhere in 300g and my electronics is somewhere at 200g , and i measure it using a string and also i drill a hole on the bottom chassis to fit my huddy balancing tool. and both measurement shows that the battery side is heavy so i add like more or less 70g on the electronic side.. its damn crazy
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Old 07-10-2006, 09:11 PM   #6
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The GTB controller and the longer heavier motor tend to cause side to side balance problems. This is what I think.

It's better for a touring car to have good side to side balance even if it has to weight a couple ounces more. There will be less unwanted torque steer (car goes to one side when you apply throttle) that is especially a problem if the track has low traction. It will also steer more the same turning left and right.

On my Losi JRXS, I was able to mount the heavy GTB controller on the side opposite the heavy end of the motor. This eliminated the need for ballast.

The rear of the car can weigh a couple ounces more than the front on the scales for best handling. Some of the weight will transfer forward on corner entry giving you more even tire loading front to back.

I think it is better to run some of the electronics on the top deck if this helps reduce the amount of side to side ballast needed, especially in the lower powered classes. The center of gravity won't change much at all due to the heavy motor and battery.

I have run the GTB controller on the left side, on the left side on the edge (fan aiming left instead of up), on the top deck, and finally on the right side. Handling was very similar, all with equal side to side balance.

Last edited by John Stranahan; 07-11-2006 at 04:05 PM. Reason: added last phrase all with equal side to side balance.
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Old 07-11-2006, 07:23 AM   #7
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Alright guys, In my opinion it doesn't make sense to add weight to the chassis if the chassis is already overweight. As long at the car is tweeked out prior to being put on the track you should have a balanced feeling car on the track. I run the RDX and run no weight for balancing. My car performs just fine without the extra balancing weight added. This is just my opinion take if for what it's worth.

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Old 07-11-2006, 08:53 AM   #8
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Default Don't balance it.

Quote:
Originally Posted by syndr0me
I've always been under the impression that it's important to keep a chassis balanced from side to side, and front to rear. It's one of the first things Martin Crisp mentions in his XXX Main book. The problem is, I have to add a ton of weight to my car to get it balanced, making it considerably overweight. Is this normal?

I have a Corally RDX with a Novak GTB and 4300 motor, and I'm using an updated motor bulkhead which moves some of the motor weight closer to the centerline of the car. Even with all that, I have to add 50+ grams to the right side to get the chassis to balance. And that's without running fans or heatsinks or anything fancy on the car.

So, what should I do? Is it okay to pile the weight on there to get the car even on both sides, or should I just let it be a bit off and tune the car around it? At some point, adding more weight will hurt more than it helps, right?
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Old 07-11-2006, 08:53 AM   #9
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i would never, ever, add weight to a car that not under the legal limit. like jim just mentioned, you can compensate for a small weight imbalance by loading the front wheels similarly.

even if a car handled differently left to right, you will be faster if you learn to drive it that way, rather than drive a heavier car around. it's not that difficult to adjust to. infact, 75% of the time i pick up someone else's car to drive, it's got more steering one way than the other. most don't even realize it.

you can use tweak as a band aid to alot of stuff. if my car lines up on the tweak board but feels tweaked on the track, i'll often add preload to the outside front, until i can diagnose the real problem. the car usually drives fine like this.

say no to extra weight. especially in stock and 19t where power is scarce.
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Old 07-11-2006, 08:55 AM   #10
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Default yup

Quote:
Originally Posted by Jim Herrmann
Alright guys, In my opinion it doesn't make sense to add weight to the chassis if the chassis is already overweight. As long at the car is tweeked out prior to being put on the track you should have a balanced feeling car on the track. I run the RDX and run no weight for balancing. My car performs just fine without the extra balancing weight added. This is just my opinion take if for what it's worth.

Jim
what he said!!!!
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Old 07-11-2006, 10:51 AM   #11
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Wow, very interesting responses, thanks guys. I'll pull the weights off and retweak the chassis and see how things feel.
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Old 07-11-2006, 10:59 AM   #12
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just realize that sometimes the car gets the lap times, won't always feel as good as one that doesn't.
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Old 07-11-2006, 11:22 AM   #13
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Also, adding weight to balance a car without a 4 scale system might even make the car worse. If you dont add the weight to the correct end of the car, you could mess up the corner weights (wedge) even more and will have a hard time tweking out the car.
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Old 07-11-2006, 12:56 PM   #14
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Yep - what he said. That's why I use 4 scales. Even though my car is about .5oz heavy on the left side, adding weight to balance it didn't seem to do anything for me. I took the weight off and tweak it so there is zero cross-weight and it's fine.
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