sonic
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| posted on 6/10/05 at 08:19 PM |
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Setting corner weights on an MK
Hi All
When setting corner weights up what should you be aiming for?
As close to equal on each corner?
Or more weight biased toward the front/rear?
Should they be set with the driver in the car?
The best way to adjust the indevidual corners,is it purely by raising or lowering the coils?
Managed to borrow some scales from work so i might have a go at setting it up
Advice would be good
Cheers
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mookaloid
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| posted on 6/10/05 at 09:10 PM |
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let me know when you find out mate - I would like to know too!
Cheers
Mark
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locoboy
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| posted on 7/10/05 at 06:30 AM |
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From reading through a kit car suspension book it seems imperative to have a level even surface to begin with - in the book they are talking about
level to within 1mm or less over an area the size of the car!
The corner weights should be set to be equal all round to provide the optimum centre of gravity, it wold be pointless to do this without the driver in
it since i'm certain your aim would be to make it 'drive' better and not sit more level on the driveway 
The book takes things to the extreme like thinking about corener weights when mounting the engine and fuel tank etc etc, but with a pre built chassis
this is not practical withought cutting and shutting.
So to make the best of a completed car you would need to make sure the lower chassis rails are level and the surface the car sits on is level too,
then tweek the spring collars to achieve as best as possible all round ride height and close to matching corner weights. - hard to do all from the
drivers seat ............a mate of similar size and weight would be an advantage or someone to go round and do the donkey work while you sit in the
seat and instruct
 
ATB
Locoboy
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progers
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| posted on 7/10/05 at 07:46 AM |
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Hi Mr Loco,
Depending on what engine you have in the MK its unlikely that you can achieve even weights all round. This is particularly true in a BEC with its
lighter engine up front. When you corner weight try to do the following (as learned from watching a professional race engineer set mine up). Note you
should be in the car when the set-up is being done or find a sack of potatoes clsoe to your weight!
1) Make sure all the scales are level (i.e. on a horizontal plane)
2) Put car on the scales, and set the front and rear ride heights - for the MK you want the rear to be 15-20mm higher at the rear (it improves turn-in
and front end grip tremendously and helps counterract the floaty steering at high speed). Measure at the front and rear of the floorpan
2) Once ride height is set and you are on the scales try and get an even balance on the same axle i.e. even the weight across the rear and across the
front. If its a BEC with a 80kg passenger (total around 530kg) you'll see something like :-
Right rear - 160
Left rear - 145
Right front - 120
Left front - 105
Using the case above, you will want to reduce the right rear and increase the left front, this can be done by slight raising the right rear of the car
using the adjustable spring base. Raising the platform will lower the weight on that corner and increase the weight on the corner diagonally
opposite.
It is a bit of a suck it and see until you get it roughly right. If you can get the axles within 10Kgs of each other you have done well. It certainly
makes the car handle much more sweetly. Note that the addition of a passenger will upset everything though!
Hope that helps
Paul
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mookaloid
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| posted on 7/10/05 at 01:55 PM |
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Good stuff Paul.
Thanks on behalf of many MK owners.
Cheers
Mark
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sonic
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| posted on 7/10/05 at 06:17 PM |
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Thanks for that!
My biggest problem now is finding a base as level as required to put the scales on.
i may now somebody with a fresh layed warehouse floor so that may be the way to go.
Thanks again
Mick
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mad-butcher
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| posted on 7/10/05 at 07:29 PM |
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theres a topic at bottom of page 7 could be top o page 8 by now called indy setup advice by alistair667 i spent about 2hrs doing the bump steer very
interesting results in the measurements while doing it
tony
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Howlor
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| posted on 14/10/05 at 01:11 PM |
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Surely though a correctly set up car should have balanced spring rates at each corner. If you simply try to balance the corner weights by winding in
the spring platforms that is a severe compromise for the suspension performance. By having inbalanced compression of each spring the starting load is
greater on the spring with greater initial compression therefore in theory if you hit a uniform bump across a full axle means that each wheel reacts
completely differently.
Am I correct?
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G.Man
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| posted on 14/10/05 at 02:50 PM |
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Adjusting preload does not affect spring rates...
the preload balances the corner weights and ensures each spring has the correct load on it and is the correct way to set corner weights...
Then there is droop which affects weight transfer... ack I'll stop there...
I hate to use this link as it is mainly about model cars, but its the best resource I have found in the past that deals with all the car dynamics...
model cars are identical in terms of the effects of geometry changes..
http://users.pandora.be/elvo/
[Edited on 14/10/05 by G.Man]
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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Mix
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| posted on 14/10/05 at 03:25 PM |
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No need to find a level base
All you need to assure is that the car is level when it is weighed.
It's a more prolonged process but you can weigh it with one set of scales and three jacks, (or three sets of blocks for that matter)
Mick
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G.Man
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| posted on 14/10/05 at 03:28 PM |
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quote:
Originally posted by Mix
No need to find a level base
All you need to assure is that the car is level when it is weighed.
It's a more prolonged process but you can weigh it with one set of scales and three jacks, (or three sets of blocks for that matter)
Mick
Mick, Are you entirely sure about unlevel ground?
Surely if the scales were in a dip that wheel will show as lighter than the others?
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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Mix
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| posted on 14/10/05 at 03:37 PM |
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Yes I'm sure
The car must be level, not the scales
That's the way we weigh aircraft 
Mick
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Mix
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| posted on 14/10/05 at 03:49 PM |
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Ooops!!
I can see where confusion may creep in
'The car must be level',
ie the bottom of the tyres must be level, the actual attitude of the chassis is not relevant when weighing, (though extremely relevant in relation to
handling)
Mick
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G.Man
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| posted on 14/10/05 at 04:07 PM |
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I may be wrong here (and if I am thats one hell of a lot of race cars I have setup wrong in the past) but to get the car level you have to shim each
wheel, which effectvely levels the floor...
Additionally, it may not be desirable to have a level car.. many cars will want a nose down attitude on them to ensure they turn better... Aircraft
dont have to maintain good grip on the ground, so they have to be balanced around a CofG as opposed to 4 contact points...
The way I always set my cars ride heights is to jack the chassis at the rear and block it so the rear chassis is parallel to the ground (it fakes the
rear end being perfect left to right) and then set the front corner weights to give the correct chassis to floor ride height...
I then do the same at the rear (block the front etc)...
Then I ballast the drivers seat to the weight of the driver and then set the corner weights individually getting them as close left to right as I
can...
If I am ballasting I will also ballast the car front to rear to get the desired weight distribution of the driver relative to the stiffness of the
springs they prefer...
I think you will find if the floor is not level (or you have not levelled the floor) then when you set the corner weights you will "tweak"
the chassis...
EDIT: ah you clarified while I was typing
[Edited on 14/10/05 by G.Man]
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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Rorty
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| posted on 15/10/05 at 02:34 AM |
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A level floor is ideal but not necessary. If using scales, then as long as the wheel pads are all level then that's all that's necessary.
Lino tiles make good leveling shims.
If you've no use for the actual weight figures, the car can be set up with a balance beam which only requires one axle (or one pair of wheel
pads) to be level.
Preload is then adjusted until the scales (or beam) are even. If, by winding up one of the spring seats, a spring nears going solid, it may be
necessary to opt for a heavier spring at that point. The car would need to be fairly badly designed/set up for that to happen though.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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