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IMR-Merlin's Avatar
 
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Quote:
Originally Posted by 911st View Post
Patrick,

Good to hear you could feel the effect. That is the most valid point of reference for doing the mod I have heard.

If it felt "much better" this might also be an argument that the front is sensitive to weight and where is it placed. If so all I am saying is put it the best place available. If one is carrying a spare tire and dose not have A/C the battery box with a lighter battery is fine.

I am not saying it is not an improvement. I am saying I do not think the polar moment is a very valid rationalization for the mod and that further forward, to the right and lower in the chassis would be even better.

And! That on the list of things that can be done to make a car (or driver) faster, this would be pretty low on my list after things like great tires, a book on driving, a strut brace, tire temp probe, or even deferred maintenance.

As for improvement, I suspect the real gains are from reducing the weight of the car about 20-30 lbs with a lighter battery and improving the the front wheel side to side wheel imbalance about 20%.


Using the propeller (lets say wheel) example is a simple and good way to explain what polar momentum is. However it dose not match the magnitude of what we are considering.

What we are doing is more like like taking a 20" 20lb wheel and moving a gram or two inward about 1/2". Not measurably going to effect the wheel via polar momentum.

However, move a little weight around on the wheel to get it better balanced and you have made an important improvement. Or lighten the wheel and we will be able to accelerate it faster.
I don't think Pat said anything about feel, maybe I misread his post, but I just looked again.

I'm interested to find out where you get your theories from.

Old 10-05-2010, 07:25 PM
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Did we ever discuss the old Craig930 corner balance thread? It is very interesting reading regarding weight distribution. "Search for Corner balanced by the numbers" in the tech forum.
Basically, I found that I could get a much better corner balance and weight distribution by moving the battery. I agree it would be optimized to get it lower, but that is hard to do. I have also found that the best thing about a good corner balance is the braking bias (L-R) in the front gets pretty equal. I hate having the car pull one way or the other under hard braking, such as going down the hill at Watkins Glen. This effect is barely noticeable on the street.
Pat
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Old 10-05-2010, 07:29 PM
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* CORNER balanced - numbers from this...and the weight
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Old 10-05-2010, 07:38 PM
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Quote:
Originally Posted by patkeefe View Post
Did we ever discuss the old Craig930 corner balance thread? It is very interesting reading regarding weight distribution. "Search for Corner balanced by the numbers" in the tech forum.
Basically, I found that I could get a much better corner balance and weight distribution by moving the battery. I agree it would be optimized to get it lower, but that is hard to do. I have also found that the best thing about a good corner balance is the braking bias (L-R) in the front gets pretty equal. I hate having the car pull one way or the other under hard braking, such as going down the hill at Watkins Glen. This effect is barely noticeable on the street.
Pat
Did you run the "boot" at the Glen? When I was with Skip Barber we ran the full road course, but when I worked with Busch North, we didn't run the boot. I loved the Glen, but there was no place to stay around there in the 90's.
Old 10-05-2010, 07:43 PM
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Pat,

I actually set it up my car with equal front corner weights for better track braking. As you know, in most cases a limited slip is required if doing this.

However, I wonder if balancing the front wheels come close to the effectiveness to actually moving the weight to balance the car.

Using my car as an example. My front weights were close to 593lbs each side.

I still had 170 lbs more on the drivers side that a good percentage of was going to be shifted to the left front wheel under threshold braking.

Guess what front wheel usually broke traction first?


If one can improve polar moment cool. It may just be my opinion but I think our rear tire to weight ratio is a much bigger restraint to going faster.
Old 10-05-2010, 08:11 PM
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Pat, Thanks for the link. It looks like there is some good stuff there that might be along the way I am now thinking and I will read it.
Old 10-05-2010, 08:20 PM
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911st,

The basic set up of any car goes like this. Get the weight as low and closest to center as possible first, of course shedding weight along the way. We used to have a saying in the shop.... "grams add up to ounces, ounces add up to pounds" Not only can you use this analogy for shedding weight, but also for moving weight.

Once you get all the weight where it belongs (and added for certain minimum weights for certain classes of racing), then you can go to the scales to corner balance the car. Then it's off to the track to test your set up for handling and adjust accordingly with spring rates, ride heights, swap bars etc....
Old 10-05-2010, 08:26 PM
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Merlin,

I accept my ignorance as bliss but thanks for the effort.

Regards,


Old 10-05-2010, 09:58 PM
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