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Old 04-20-2004, 07:25 AM   #1
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Default The lesser of three evils?

Ok, so just for conversations sake, let's say that a guy gets a new car, (me perhaps?! ), and he's trying to get the unsprung weight of the chassis as close to perfect as possible....but in order to do this he has to place weight on a corner of the car with very little/zero room to work with or move things around, so he has to mount the dead weight higher than would be ideal.

So my question to all you chassis tuners out there is this: assuming that you need to do one or the other, would you rather:

1.) Have a car that has a nicely balanced static weight with a higher center of gravity.

2.) A car that isn't perfectly balanced, but has the lowest COG possible.

3.) -OR- would you leave the dead weight off completely to save weight and try and balance the chassis via sprung weight suspension tweaking?

And oh yeah, I'd like to not make this a conversation about how to balance any one specific car, it's more of a general physics/car dynamics question.
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Old 04-20-2004, 09:15 AM   #2
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IMO, never add weight unless you are under legal limits. Weight is the number one enemy. Especially when you have other items on the car to use as ballast i.e. esc, batteries, receiver, etc. If your dealing with a car with a good chassis, using the suspension to dial out tweak should be sufficient. As far as balance is concerned, depending on the type of drivetrain and car, a 50/50 weight distribution/balance may not always be the best way to go. Your situation is exactly why race teams in every form of racing around the world try to get their cars as light as possible. So the weight they have to add to be legal can be used as ballast to get the proper balance.
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Old 04-20-2004, 09:25 AM   #3
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Quote:
Originally posted by Fuzzy
IMO, never add weight unless you are under legal limits. Weight is the number one enemy. Especially when you have other items on the car to use as ballast i.e. esc, batteries, receiver, etc. If your dealing with a car with a good chassis, using the suspension to dial out tweak should be sufficient. As far as balance is concerned, depending on the type of drivetrain and car, a 50/50 weight distribution/balance may not always be the best way to go. Your situation is exactly why race teams in every form of racing around the world try to get their cars as light as possible. So the weight they have to add to be legal can be used as ballast to get the proper balance.
but on the flip side of that, some people say they like the way a little extra weight makes the car feel. they say it slows transitions of the car and makes for smoother drive.

I personally agree with you, weight is weight, and any extra weight on the car should be avoided.
So I'm guessing you're saying you'd go with 3? (Perhaps I should have set this up as a poll...)
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Old 04-20-2004, 11:21 AM   #4
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My choice would be #3. But I would then start looking for ways to remove weight anywhere I could. If you don't mind me asking, what car are you driving?
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Old 04-20-2004, 12:26 PM   #5
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# 3 is what we deal with normally tweek the car via weight transfer with springs.
pluss we all prefer low cg's
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Old 04-20-2004, 01:35 PM   #6
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Why do you think graphite came about? Not only to add strenght but to lighten the overall weight of the car. Take the current craze>>>touring car. Just about everyone is going away with the stock "tub" chassis(TC3) to graphite. Move battery placement closer to the center ...etc. Same thing with off-road(RC10) from aluminum to graphite too. Not to mention oval & 1/12th cars....it's the exclusive domaine of graphite. As Fuzzy said, you can add weights where it is needed if needed. It is better to add than to look for place/things to remove weight. Just my 2cents.
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Old 04-20-2004, 01:44 PM   #7
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Quote:
Originally posted by Fuzzy
My choice would be #3. But I would then start looking for ways to remove weight anywhere I could. If you don't mind me asking, what car are you driving?
hmmm... not sure if I should tell you what car I'm talking about.... haha! Well, I suppose I might as well let the cat out of the bag. It's a Pro4, and I'm looking to add a little weight to the right front as it's my lightest. And yes, I've checked for chassis tweak and it's straight and true. My ultimate goal here is to get the chassis's static weight as close to 25% on all corners without having to crank on alot of spring preload.

Since there isn't much room up there for lead weights I was going to move my reciever to the top of my servo to move the weight to that corner, (It's currently behind the servo on the chassis), but in doing that I'm raising my CG.

So you see now why I asked the question...given one or the other, which would you choose, higher CG or slightly off balance?

And as it stands right now, with the body, I'm .5oz over the roar max, which is 53oz (I believe...right? )
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Old 04-20-2004, 02:48 PM   #8
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Quote:
Originally posted by cartmen34

So you see now why I asked the question...given one or the other, which would you choose, higher CG or slightly off balance?
And as it stands right now, with the body, I'm .5oz over the roar max, which is 53oz (I believe...right? )
I would do some testing with the receiver's position and see which way the car handles better. That's better than guessing. As for your other question, at the ROAR On-road Carpet Nats, the minimum weight for Touring was 51oz.
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Old 04-20-2004, 05:24 PM   #9
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Quote:
Originally posted by jeepnyy
Why do you think graphite came about?
For pencils?
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Old 04-20-2004, 05:38 PM   #10
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Quote:
I would do some testing with the receiver's position and see which way the car handles better. That's better than guessing. As for your other question, at the ROAR On-road Carpet Nats, the minimum weight for Touring was 51oz.
Hey, some of us race outside on rubber tires too, you should try it. The weight for a TC with rubber tires is 53 oz.
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Old 04-20-2004, 05:53 PM   #11
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put a transponder mount off of your steering servo and put the transponder in the car then weigh it.
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Old 04-20-2004, 06:02 PM   #12
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Quote:
Originally posted by Masterfaster
put a transponder mount off of your steering servo and put the transponder in the car then weigh it.
Well that may not always balance a car, and that would sometimes add too much weight when you only 1-3 grams. But now things are shifted to the ends of the chassis changing the moment of intieria (sp?).
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Old 04-20-2004, 06:15 PM   #13
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add weight to balance the chassis if your track does NOT have alot of traction.

lower center of gravity if your track HAS lots of traction.

if your racing stock, drop the weight. If your racing mod, balance your car (its going faster, more weight = more tire contact patch = more traction)

always balance the tweak of your suspension as this creates an equal contact patch between the left side and right side tires and the racing surface, which is of upmost importance in roadcoarse racing.

Is it possible to melt solder in any unused crevice on your chassis?

try putting lead tape (tire balancing stuff) on the bottom of the chassis.
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Old 04-20-2004, 06:22 PM   #14
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Do you ever think its possible to balence rims? Like full size automobiles? But the weight added/taken off would be so unnoticable, just a thought.
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Old 04-20-2004, 06:30 PM   #15
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Default Re: The lesser of three evils?

Quote:
Originally posted by cartmen34
Ok, so just for conversations sake, let's say that a guy gets a new car, (me perhaps?! ), and he's trying to get the unsprung weight of the chassis as close to perfect as possible....but in order to do this he has to place weight on a corner of the car with very little/zero room to work with or move things around, so he has to mount the dead weight higher than would be ideal.
Cartmen, your question may be flawed from the start. If you intend to place weight are various locations on the chassis, or move electronics around the chassis, you are not affecting the unsprung weight, you are affecting the sprung weight. The difference between the two depends on if the weight is supported by the springs or not. Since the chassis and all components mounted on it are supported by the springs, it's the sprung weight. Unsprung weight are items that include the tires, steering blocks/hubs, and part of the suspension arms up to the bottom of the shocks.
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