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Old 16 Aug 2008, 01:31   #1
215maloo
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Corner weights without scales

Hi,

Looking for info on corner weighting a car without access to scales. I understand their is a method that involves balacing one end of the car on a pivot point and then levelling it ???

Any information on this method would be appreciated. I'm also interesting in what its limitations are (apart from being a little less accurate than scales).

thanks

Last edited by 215maloo; 16 Aug 2008 at 01:32. Reason: typo
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Old 16 Aug 2008, 11:07   #2
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Think it might be esiear to spend the $1800 for scales and do the corner balance properly.
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Old 18 Aug 2008, 14:17   #3
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That seems like it would work if you can find measuring spots on each side of the chassis that are totally equal, then find the exact centerline of the other end. Your chassis would have to be perfect as small deviations can make big differences. I use a set of $300 modified ruggles style scales that work pretty darn well, although they are a little harder to level accurately. This dude makes them.

http://motors.shop.ebay.com/merchant/sprintracerman
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Old 18 Aug 2008, 17:31   #4
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If I have really understood your question, you really want to know the corner weights. As far as I am aware, this is only possible to measure with some sort of scales, professional or not.
What you suggest is finding the CG height, but this is only (really) usefull if you know the corner weights.
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Old 18 Aug 2008, 20:27   #5
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Mumford Beam

There was an article a few years ago in Racecar Engineering (Might have been Race-Tec) about the Mumford Beam. I have used this exclusively for cornerweighting ever since.

All the ideas about using bathroom scales just arent worth bothering with. There isnt the accuracy or repeatability on them, even if you use 2 on a corner.

The mumford beam is just a see saw that you place the wheels of one axle on so that the pivot is halfway between the 2 wheels. I made mine in 2 hours from 2 lengths of scaffold tube (for my lightweight car I could have used much lighter tube) welded about 4" apart with a bit of angle iron for the pivot. This can if necessary be taken to the race/test day strapped to the trailer.

To use, you place the beam under the front wheels, with the rear wheels on a level piece of floor (you only need 2 level patches - use ply or old copies of Race Tec to level the patches if necessary). Pick a horizontal surface on the chassis, and adjust the rear spring platforms so that that surface is truly horizontal (use a spirit level). Then place the level on the mumford beam, and adjust the front spring platforms until that too is level.

Now, when the car sits on a flat surface it will be level, and there will be equal weight on the front wheels. If the car has even left/right weights, there will also by definition be equal weights on the rear wheels and equal diagonals. Even if your car has uneven side-side weights, you still ahve equal front weights, which is arguably as good as equal diagonals as braking is where corner weights have most effect. At worst, it is better than guessing or using even spring platform positions, and your settings are 100% repeatable which ensures consistency.

Enjoy.

G
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Old 19 Aug 2008, 16:45   #6
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thanks for sharing

a great, simple concept that makes perfect sense for finding left to right balance ...
have you tried the technique for front to rear balance?
only caveat: an oval track car often needs to be imperfectly balanced to get the most from the tires
wonder how it might be applied in that arena?





Quote:
Originally Posted by GordonG
There was an article a few years ago in Racecar Engineering (Might have been Race-Tec) about the Mumford Beam. I have used this exclusively for cornerweighting ever since.

All the ideas about using bathroom scales just arent worth bothering with. There isnt the accuracy or repeatability on them, even if you use 2 on a corner.

The mumford beam is just a see saw that you place the wheels of one axle on so that the pivot is halfway between the 2 wheels. I made mine in 2 hours from 2 lengths of scaffold tube (for my lightweight car I could have used much lighter tube) welded about 4" apart with a bit of angle iron for the pivot. This can if necessary be taken to the race/test day strapped to the trailer.

To use, you place the beam under the front wheels, with the rear wheels on a level piece of floor (you only need 2 level patches - use ply or old copies of Race Tec to level the patches if necessary). Pick a horizontal surface on the chassis, and adjust the rear spring platforms so that that surface is truly horizontal (use a spirit level). Then place the level on the mumford beam, and adjust the front spring platforms until that too is level.

Now, when the car sits on a flat surface it will be level, and there will be equal weight on the front wheels. If the car has even left/right weights, there will also by definition be equal weights on the rear wheels and equal diagonals. Even if your car has uneven side-side weights, you still ahve equal front weights, which is arguably as good as equal diagonals as braking is where corner weights have most effect. At worst, it is better than guessing or using even spring platform positions, and your settings are 100% repeatable which ensures consistency.

Enjoy.

G
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Old 20 Aug 2008, 21:22   #7
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I like the sound of the mumford beam...I usually use a corner weight gauge and a sheet of paper under the two front wheels to measure the diagonal weights. I make sure the for wheels are level firstly across all four pads in which the wheels rest on. I take a measurement when I can just pull the paper free. I find you have to bounce the gauge to get acceptable readings in lbs.

It would be good to use the mumford beam to compare results.
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Old 22 Aug 2008, 12:50   #8
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If its a light "ish" car you can use bathroom scales (if you know how) and will work just as well as some of the corner weight ones that are sold .

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Old 23 Aug 2008, 16:34   #9
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Quote:
Originally Posted by Speedy1
a great, simple concept that makes perfect sense for finding left to right balance ...
have you tried the technique for front to rear balance?
only caveat: an oval track car often needs to be imperfectly balanced to get the most from the tires
wonder how it might be applied in that arena?
Speedy,

You do mean Left Front to Right Rear and Right Front to Left Rear?

Corner balance is just that. LF + RR = RF + LR
That is with the driver in the drivers set and tank of fuel

Just going left to right or front to back, is not enough and will still up set the car though corners.
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Old 24 Aug 2008, 21:33   #10
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my understanding

My understanding of Gordon G's Mumford beam description:
by using spring pre-load it is possible to create an equilibrium between the left and right side of the vehicle, it does not find equilibrium front to rear ... no doubt a useful tool on a track where all turns are equal
if a race circuit has a preponderance of turns in one direction it will often be an advantage to (un) balance the vehicle to gain a performance advantage for the amount of time that will be spent in that direction
examples would be Nascar, WoO, or Indycar oval racing
their rule books limit the weight percentages front to rear as well as side to side for safe handling reasons
the simple pivot beam used as described by Gordon G will not define weight percentage on the axles or on the contact patch




Quote:
Originally Posted by AU N EGL
Speedy,

You do mean Left Front to Right Rear and Right Front to Left Rear?

Corner balance is just that. LF + RR = RF + LR
That is with the driver in the drivers set and tank of fuel

Just going left to right or front to back, is not enough and will still up set the car though corners.
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Old 27 Aug 2008, 01:31   #11
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http://www.demon-tweeks.co.uk/produc...T&pcode=P/PPP2
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Old 28 Aug 2008, 10:08   #12
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you cant transfer weight aroudnd the car, from left to right or front to rear, just by playing with spring perches, whcih is all you are doing when setting corner weights whether using scales or mumford beam.

The mumford beam simply allows you to get equal weight on the 2 front tyres. The corresponding weight distribution across the rear tyres will be whatever it takes to support the CoG of the car. IF the car CoG happens ot be on the centreline then you will have equal rear weights also, and happily equal diagonals (which is what most people aim for with scales). So this works perfectly for your typical central driving position single seater.

If your CoG is to one side, the rear tyres will take all this weight differential if the fronts have equal weight. However, I've found this is still a good approximation even with a 2 seat car, and importantly it allows you to be consistent.

G
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