Lotus Elan

Ride height baby elan

PostPost by: miked » Wed Jan 03, 2007 12:33 pm

Guys what is the opinion about the setting of this. I understand that the actual height could cause quite a debate but I am more interested in terms of the driver weight being in the car when doing it.

I have looked on some forums and peope set up with no driver just fuel etc.
Then on others they fuel up and put the driver weight in and then set the ride height with the driver weight. Also they do corner weight after this.

This is for a road car that does odd track days. I have not set this properly yet just did the approx bit with the ruler. When I get in the car I do weigh it down and upset the ride height with the current rough setting. Dont like it not being level. I do ride with a passenger in sometime sand this does help level. Have TTR fast road springs all around.
I would be more happy (i think) to be ride height set with just me as this is when it counts and would more likely to be going a bit quicker. Sorry if i am confused but would like to learn about this.

Any thoughts appreciated. Put it in racing as I thought it was best place. One day :P

Mike
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PostPost by: steveww » Wed Jan 03, 2007 4:31 pm

Doing it properly involves measuring the corner weights, i.e. scales under each wheel. These are expensive at about ?1000 for a set :shock:

Understandably I decided not to go with this method. The drawings in the Lotus manuals show the suspension arms level at normal ride height. I use this as my guide and a spirit level. As my S4 has adjustable spring platforms all round I usually drop from the normal settings for a track day.So far I have just used -20mm all round. Not sure my driving is good enough to notice though :oops:

Watch out for speed bumps!
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PostPost by: gav » Wed Jan 03, 2007 6:14 pm

Mike

In the good old days before computerised set up floors and the like, we used 4 sets of bathroom scales for single seater set up - one under each wheel.

Admittedly it wasn't perfect but it would go a long way in sorting out suspension set up.

I don't know whether you can get scales with an adequate range for the Elan but it is probably worth doing some homework.

Just a thought.

Have fun.

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PostPost by: miked » Wed Jan 03, 2007 9:11 pm

Thanks for replies so far.

Re: scales I have scoured quite a few sites about doing this over the last 2 days and also the type of scales etc. There are devices (home made) with sketches and dimensions etc for making a 3 to 1 ratio device (with a bathroom scale) so that one can be put under each wheel. There was advice about not doing this and just using one of the 3 to 1 devices and keep moving it around. Using blocks of same hieght at the other three corners while you do it. This advice was due to difference in device tolerance and scales etc. The drawing of the device had a conduit pivot for the wheel platform and one for the scale platform to help reduce any side loading. I was going to make one of these and then I looked back a posting I did before and Nick had posted about using 8 low cost scales with some short planks across so you sit each wheel in the midle and the scales share the weight. With this method you can actually roll the car on the planks a little (after jacking for adjustments) to ride out any side stress. You can also calibrate a little by putting a known weight on all 8 scale before you start and attempt to obatin the best reading. I read up on the left weight, rear weight and cross weight business and figure that whilst this is not as accurate as the ?1000 stuff it will get me a lot nearer than now. As I understand I can do little about left weight nor rear. They are factors of design (and car loading) but can set to 50% cross weight so that I dont not have diagonal loading on any two wheels. To my way of thinking if they do this on Go karts it must be well worthhwile. Also considering a 2 seater is alway going to have a C of G to the driver side anyway.

The scales are still ?3.99. Got some funny looks buying 8 but who cares. Will hopefully have ago this weekend.

Thanks Mike


From Nicks post;

Bathroom Scales and Corner Weights

I've used bathroom scales for corner weighting on my Elan and 7 and they work fine. I bought 8 x 120 kg (19 stone) scales from Homebase at ?3.99 each. I cut 4 wooden strips to lay across the top of each pair of scales and just add the two readings to get weights for each corner.
Results are repeatable within about 4kg.

I've checked the results on a weighbridge and on electronic scales and all results have been within a few kg of each other (721kg / 1586lb for my S3FHC).

I used 8 scales as these are very cheap (all 8 cost less than a single higher capacity scale) and using 2 per wheel gives a larger platform, allowing the car to be rolled backwards and forwards to aid settling.

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PostPost by: gav » Wed Jan 03, 2007 10:05 pm

Mike

A man after my own heart.

Great research - thanks for the info.

I too will raid homebase - I needed a bit of a prod to get me going on the set up so much appreciated.

All the best
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PostPost by: denicholls2 » Thu Jan 04, 2007 3:39 pm

When setting up your suspension, I doubt you can do much better than the advice of Carrol Smith. His multi-book "To Win" series will teach you more about suspension geometry, common blunders, metallurgy, and general physics than you ever thought you needed to know, in a down-to-earth racing mechanic's language. He also favored approachs like the 8-scale method (lest you fear that big-budget racing clouded his perspective.)

The whole set new is usually on sale for about the same price as the 8 scales, and I doubt you will regret the investment. :D
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PostPost by: miked » Fri Jan 05, 2007 10:02 am

Some of the posting in the other forums did refer to his books that you mention. I intend to obatain.

Re: The scales. Found them a bit cheaper in B & Q when browsing last night.

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PostPost by: rgh0 » Fri Jan 05, 2007 10:30 am

You only really need a couple of bathroom scales to easily do one corner at a time by making up a lever system that enables you to lift one of the wheels fractionally off the ground at a time while the car just sits on a level floor.

The lever can be designed to pick up the wheel either under the centre of the hub or under the top of the wheel rim.

While not 100% accurate compared to 4 computerised scales it is near enough for us home mechanics and amateur racers

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PostPost by: miked » Fri Jan 05, 2007 3:04 pm

Rohan,

Could you please elaborate a little. I understand about the lever thing as I have seen those lever type corner weight devices with the gauge but not quite sure about use with the scales. Are you using the stand on the two scales for a reading
:?

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PostPost by: rgh0 » Fri Jan 05, 2007 11:38 pm

Mike

Take the 2 scales and put a study plank of wood accross them. Place another suitable block of wood on the plank midway between the 2 scales whose top is about equal to the centre of the hub. A rounded top on this block of wood helps the lifting beam to pivot freely

Place this arrangement close to the wheel and take a steel or wooden beam, rest it across the block and under the hub spinner and read the starting weight registered on the scales before you begin lifting. Press down on the free end of the beam and lift up the wheel until it is fractionally off the ground and read the weights measured on the scales.

To get the corner weight you need to subtract the weight of the lifting components as read on the scales before you started lifting and adjust for the force induced on the scales by you pushing down on the free end of the beam.

i.e If the ratio of lengths of the beam from pivot point to your push down point and from pivot point to the hub spinner was 10:1 then your push down force is 1/10 of the corner weight and the scales read 11/10th of the corner weight after you subtract the initial weight of the lifting components.

The slight movement of the wheel as you lift it upsets the corner weight measurement a little. This works OK especially on a car like an Elan with relatively soft suspension but not so well on a car with rock hard suspension.

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PostPost by: miked » Tue Jan 09, 2007 1:33 pm

Rohan thanks for detailed info'. I understand.

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PostPost by: miked » Mon Feb 19, 2007 9:55 pm

UPDATE!

Corner weights with 8 bathroom scale - done it! As described. Need to read back to see what was being planned!

My floor was not flat (big time) so had to pack up the scales to get a full level on all 8 with the planks.

Need lots of patients. I added 4 small (adjustable) platforms to roll the car off the scale planks to allow for jacking and landing. I put some plastic and alloy sheet on these platforms to allow the car to be pushed down after platform adjustments. Worked a treat. Drop the car and nudge with the bum and the wheels slide out to their correct position.

I have 50% cross weight and the correct ride height with my weight in the driver position (including feet weight). I set the ride height just a bit lower than standard at the front and left it standard at the rear.

Took it out for a run to Buxton yesterday and it is great. Have not been out properly since I did the rear track. Such a better car. Worth doing.

I will post some photos of the set up with the car on if anyone is interested. I learned quite a lot by doing this. It is quite alarming when you jack a corner (spring platform) and the diagonal opposite reacts so much. Jack rear left and right nose goes down.

All kit was budget, scales, wood unitstrut and roof bolts.

Repeatability with the scales was good. ie quite close total and front/rear weights. Only problem is being careful as you go past the full weight of the scale if you dwell when rolling from centre. I think the cheap ones seem better for this as they did not seem to mind going around the clock.

One thing is for sure, it is much closer that it was before even if there is some slight error.

Mike :D
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PostPost by: john.p.clegg » Tue Feb 20, 2007 6:42 am

MIke

You have 50% cross weight but what is the front/rear,what fuel load,where do you abide...(Buxton?)

John....
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PostPost by: miked » Wed Feb 21, 2007 6:46 pm

John,

I am near Warrington. I had half a tank full in the car. My weight of 90KG

Front weight 417 48.4%
Rear weight 444 51.6%
Left 405 47%
Right 456 53%


Total 861

Cross 49.94. To get closer would have meant part of a KG and with the accuracy of the scales would probably have not been worth it.


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PostPost by: john.p.clegg » Fri Feb 23, 2007 7:13 am

And last but not least ,by how much have you had to adjust the platforms to acheive this,and which corners?

Thanks
John :wink:
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