madteg
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| posted on 15/10/13 at 08:37 PM |
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Corner weight measurements
NSF 300 LBS SQ INCH OSF 300 LBS SQ INCH
NSR 350 LBS SQ INCH OSR 390 LBS SQ INCH
These are the measurement i have got with a hydraulic corner weight scale, had full tank and my weight in drivers side.
This is the best i can get it, think its because i ham sitting near to the OSR wheel. What do you think.
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mark chandler
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| posted on 15/10/13 at 09:02 PM |
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You need a little more twiddling to get perfect, 1/2 tank of fuel and the diagonals when added should all be equal.
It's very close
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adithorp
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| posted on 15/10/13 at 10:18 PM |
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A lot of reading between the lines here but...
Sounds like you're trying to get the 2 front equal and the 2 rears equal. You never will without actually moving ballast around. The total for
any side or end cannot be altered. That means if you reduce your o/s/r rear to atch the n/s/r then your o/s/f will increase.
Instead you want to set so the total for opposite corners are equal. So n/s/f + o/s/r = o/s/f + n/s/r
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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britishtrident
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| posted on 16/10/13 at 07:04 AM |
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The corner weights have to be set in the cars normally laden state ie with the driver onboard.
There are two alternative methodologies used for working out the ideal settings either: setting the fronts to carry equal weights or setting
each wheel to carrry its' theoretical share of the weight in effect this is equal diagonal weights.
If you set the car to somewhere between the two settings you won't be far out.
Best way to get an idea what is happening is to use a spreadsheet. Enter the weight of each corner, work out the total weight, total left
weight, total right weight, total weight on front wheels, total weight on rear wheels .
From this you can work out front/rear and left/right weight distribution.
From this you can work out the the theoretical load for each wheel
For example Theoretical Load for Left Front = (total left * total front) / total weight
((300+350)*(300+300))/1340 =291
[Edited on 16/10/13 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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bill132hotrod
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| posted on 16/10/13 at 10:10 AM |
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Corner weights
Interesting this I was always led to believe it was always about cross weight, even distribution of weight to each corner !!!??
So if you we're starting from scratch what would one be looking to achieve ??
PERSEVERANCE is the word of the week. Stick with it the results are SWEET.
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mark chandler
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| posted on 16/10/13 at 11:00 AM |
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Just think of it like a 4 leg table, if one leg is slightly short it will rock as only 2 diagonal legs carry the load so you are just twiddling until
the diagonals each carry the same load.
You do of course have to ensure that the table is sitting flat and level as you can achieve even weights across the car with it tilted.
So from scratch, cut a couple of blocks of wood to make measuring ride height easy, one at 4" for the front, the other 4.5" for the rear,
on flat level ground twiddle the springs until the car sits correctly, once you have this start adjusting the spring seats to balance.
It's amazing how much weight will shift about, sitting forward can move it all around so have someone of your weight sitting in the driving seat
as if driving.
For a BEC you may be able to get away with bathroom scales, that's all I used just zero'd when loaded with 100kg.
Regards Mark
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CNHSS1
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| posted on 16/10/13 at 11:03 AM |
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also worth mentioning the corner weighting should be done with any anti roll bars fitted, disconnected. Once completed, then reconnect the ARBs d
adjust the droplinks so theres no preload to your cornerweighted setup (often means one link on each ARB longer than the other).
another side effect that some people find odd is that when the drivers not sat in a lightish car, its sits cock eyed statically! This is normal and
not wrong ;-)
"Racing is life, everything else, before or after, is just waiting"---Steve McQueen
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adithorp
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| posted on 16/10/13 at 11:25 AM |
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I have to agree with Mark rather than BT on this one.
I've tried mine in all three set ups BT mentions and only with the op' corners equal does the car feel right. With the front equal (and to
a lesser amount when in between the 2 methods) the balance alters when going from drive to braking (it rocks across the high load axis?). The effect
mid corner is quite odd and different in different directions. Great handling on one lock but a sudden switch from over to under-steer and vice-versa
(rather than a steady predictable progresion) on the other lock.
"Wedge" is the deliberate setting of unequal corner-weights to give better handling in one direction; Mainly used on oval racing in the
'states.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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britishtrident
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| posted on 16/10/13 at 11:40 AM |
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quote:
Originally posted by bill132hotrod
Interesting this I was always led to believe it was always about cross weight, even distribution of weight to each corner !!!??
So if you we're starting from scratch what would one be looking to achieve ??
Some people like the front set to equal weights because it reduces the tendency for one front wheel to lock prematurely, but on a rwd it has
unwanted effects traction and rear braking.
A lot of my "yoof" was spent building and racing Imps and Davrians which had a very asymmetric left/right weight bia, getting the
front left tyre to do its' share of the braking took a fair bit of fiddling.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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GeoffT
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| posted on 16/10/13 at 01:47 PM |
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I've always set up for equal diagonals, I tend to picture it as the 4 legged table analogy already mentioned and it seems to give reliable
results, certainly for road use.
There's also an argument that driver in or out makes no difference using this method. If you imagine a 100kg driver sat in a seven, the weight
would distribute something like this:-
-----------FRONT----------
NSF 10kgs OSF 20kgs
NSR 30kgs OSR 40kgs
-----------REAR--------------
........so the extra load on each diagonal is 50kgs, thus preserving the status quo, and I suppose theoretically this should hold for any weight
placed anywhere in the vehicle. I hasten to add that I've never checked this out for real, but it seems to make sense to my feeble little
brain.....
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adithorp
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| posted on 16/10/13 at 03:39 PM |
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quote:
Originally posted by GeoffT
I've always set up for equal diagonals, I tend to picture it as the 4 legged table analogy already mentioned and it seems to give reliable
results, certainly for road use.
There's also an argument that driver in or out makes no difference using this method. If you imagine a 100kg driver sat in a seven, the weight
would distribute something like this:-
-----------FRONT----------
NSF 10kgs OSF 20kgs
NSR 30kgs OSR 40kgs
-----------REAR--------------
........so the extra load on each diagonal is 50kgs, thus preserving the status quo, and I suppose theoretically this should hold for any weight
placed anywhere in the vehicle. I hasten to add that I've never checked this out for real, but it seems to make sense to my feeble little
brain.....
Your specific example does work but I think you'd find thats not the way it would actually distribute. If you were right, then you could corner
weight the car as a rolling chassis (without engine, box, body work or anyting else) and it'd still be correct when fully assembled...
PS I've tried it with and without driver/passenger to see how much it altered... and it did, quite a bit.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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GeoffT
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| posted on 16/10/13 at 05:23 PM |
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quote:
Your specific example does work but I think you'd find thats not the way it would actually distribute. If you were right, then you could corner
weight the car as a rolling chassis (without engine, box, body work or anyting else) and it'd still be correct when fully assembled...
PS I've tried it with and without driver/passenger to see how much it altered... and it did, quite a bit.
.....Ok, useful to see it tested in a real setup. I suppose like many a good sounding theory - it doesn't work in real life.
That seems to show that added weight doesn't necessarily distribute equally across the diagonals, no particular reason why it should I
suppose....
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britishtrident
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| posted on 17/10/13 at 12:16 PM |
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Too much spring pre-load can have a big effect on unladen corner weights, I have seen few Seven style cars that sit on 3 wheels without the driver
onboard.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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