Stiffer Anti Rollbar

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Stiffer Anti Rollbar

Postby Monty » Mon 25.08.2008, 11:13

I have no clue on this subject but from what i`ve read (thanks to Brains links) that this is another good step to take to reduce roll on trackdays. So i`m thinking off starting with the rear 1st but need some off the advice from our more experienced members :-D

Here`s some quotes and links from another thread

F1 LOTUS wrote:I reckon a set of well designed adjustable roll bars with give you the best bang for your buck without compromising everyday ride quality. With the talent LEC has available it's no too difficult to imagine a really neat installation at a reasonable cost



F1 LOTUS wrote:
Nige wrote:Well, we could ask Lotus again (got to be worth a try) or someone (who is looking for the Rolly eyes smiley) could buy a set of standard springs to define the start point.

But I'm liking the idea of stiffer anti roll bars, do we know anyone who could :wink: . I'm very willing to work with this as I have a real interest in developing the car in a way that Ithink Lotus might have done if it had stayed in production (complete hypothetical bo**ocks but you know what I mean).


I could suggest someone but I don't think Kuching would be amused, so I'll say nothing :)

In the meantime there are some calculators here to play with
Try the wheel frequency calculator
http://www.racingaspirations.com/index.php






F1 LOTUS wrote:More food for thought coutesy of Autospeed: -
http://autospeed.com/cms/A_2746/article.html
http://autospeed.com/cms/A_2359/article.html
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Re: Stiffer Anti Rollbar

Postby Monty » Mon 25.08.2008, 11:18

Ok, i`ve got a spare rear anti rollbar and going off the above links it make be a case off just having it re-made in a thicker bar but do we also need to stiffen the drop links? :?
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Re: Stiffer Anti Rollbar

Postby Nige » Mon 25.08.2008, 17:17

We must be thinking alike Monty as I was looking at a rear anti-roll bar on e bay last night wuith the thought of getting it as a pattern.

I think a simple stiffer bar will be simple enough to have made, my preference is for something adjustable but we have to start somewhere and the more adjustability the more there is to get wrong :roll: . The drop links may well benefit from some beefing up as a stiffer roll bar is going to put more force through them.
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Re: Stiffer Anti Rollbar

Postby F1 LOTUS » Mon 25.08.2008, 20:13

You'll probably need an adjustable bar for development purposes, also it will make the car more adaptable for road and track use. The design should be simple - what could go wrong :roll:
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Re: Stiffer Anti Rollbar

Postby Doug » Mon 25.08.2008, 20:47

F1 LOTUS wrote:what could go wrong :roll:


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Re: Stiffer Anti Rollbar

Postby Monty » Mon 25.08.2008, 21:42

Nige wrote:We must be thinking alike Monty as I was looking at a rear anti-roll bar on e bay last night wuith the thought of getting it as a pattern.

I think a simple stiffer bar will be simple enough to have made, my preference is for something adjustable but we have to start somewhere and the more adjustability the more there is to get wrong :roll: . The drop links may well benefit from some beefing up as a stiffer roll bar is going to put more force through them.


I have no knowledge on this subject only some off what i`ve read in the above links, but i agree lets keep this simple. What i can`t understand is how will going to i thicker diameter bar make a difference when the antiroll bar is attached to ball joints on the rear wishbones? wouldn`t there be the same amount off movement :?

At the moment i`ve got other things upgrades to pay for so i`m in no rush at the moment, but if you decided to have one made up let me know and i`ll try and get my spare antiroll bar to you.
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Re: Stiffer Anti Rollbar

Postby Doug » Mon 25.08.2008, 22:02

Monty, the ARB works thru torsion of the bar; thus a bar of greater diameter has greater torsional strength to resist the movement.

it will definitely change the rear handling, and I'll agree that you'll have to play with it and see. Furthermore, you'd probably do best to discuss the idea with some seasoned drivers and Lotus types. Hack have the Lotus factory driver drive your car around and see what they think of the handling -- it's stuff like that that will teach you the most. There are books on the subject too . . ..
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Re: Stiffer Anti Rollbar

Postby bobbrown » Tue 26.08.2008, 14:49

A stiffer rear anti roll bar should improve trackday handling but how much you increase it by is going to be a bit of a guess.
I do not know, with out measuring what the thickness of the current rear anti roll bar is but you will be limited to some extent by the material that is available in terms of diameter.
I have done some work with anti roll bars in the past but they did not have the drop link arrangement that the Elan has.
Too small doesn't utilise its full potencial and there will be excessive body roll. On the other hand, too large sway bar and its effect of reducing wheel independance can prematurely overcome tyre grip. This is with an extremely large sway bar, where were it is best keep on the lower side of this limit for road cars using road tyres. Extensive testing will determine both the size of total sway bar roll resistance an its front and rear split.
A simple solution as a test may be to get a bar bent which should be easy and then clamp it to the existing bar much as the front anti roll bar on a Vauxhall Nova clamps to the front tie bar.
You wll need 4 clamps but it does have the advantage of being removable for normal road use.
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Re: Stiffer Anti Rollbar

Postby Freelander » Tue 26.08.2008, 15:26

As most of us are probably rolling around on 18 year old rubber bushes. Any improvement to ARB or stiffer suspension would need to be complemented by modern polyurethane bushes.
IIRC the Esprit has benefitted from Lotus support in the development of modern bushing technology - but for a larger potential client base - do we have enough 'leverage' to get equal support for a comprehensive review of the M100 to develop a modern suspension setup?
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Re: Stiffer Anti Rollbar

Postby bobbrown » Tue 26.08.2008, 16:37

Freelander wrote:As most of us are probably rolling around on 18 year old rubber bushes. Any improvement to ARB or stiffer suspension would need to be complemented by modern polyurethane bushes.
IIRC the Esprit has benefitted from Lotus support in the development of modern bushing technology - but for a larger potential client base - do we have enough 'leverage' to get equal support for a comprehensive review of the M100 to develop a modern suspension setup?


I doubt if Lotus are likey to be interested in doing any thing to the suspension on the Elan, as most owners are quite content to drive the cars on the road.
As for polyurethane bushes if they are so good why do the major motor manufacturers stick to rubber?
Racing suspension tends not have compliant bushes, they are fitted with "rose" joints and are usually fully adjustable.
I suspect that there it is unlikley that anyone would want to go to the expence of either changing all the bushing to poly or re-engineering the suspension to rod ends and rose joints.
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Re: Stiffer Anti Rollbar

Postby Nige » Wed 27.08.2008, 09:18

Efforts have been made in the past to have poly bushes made for the Elan not of which have come to fruition largely due to the initial outlay and the limited market for the product.
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Re: Stiffer Anti Rollbar

Postby Monty » Wed 27.08.2008, 14:43

Guys, can we Plz stick to the anti rollbar as thats the reason i started a new thread :roll:

What Will the Anti-rollbar be made off? standard mild steel? :?

bobbrown wrote:A stiffer rear anti roll bar should improve trackday handling but how much you increase it by is going to be a bit of a guess.
I do not know, with out measuring what the thickness of the current rear anti roll bar is but you will be limited to some extent by the material that is available in terms of diameter.
I have done some work with anti roll bars in the past but they did not have the drop link arrangement that the Elan has.
Too small doesn't utilise its full potencial and there will be excessive body roll. On the other hand, too large sway bar and its effect of reducing wheel independance can prematurely overcome tyre grip. This is with an extremely large sway bar, where were it is best keep on the lower side of this limit for road cars using road tyres. Extensive testing will determine both the size of total sway bar roll resistance an its front and rear split.
A simple solution as a test may be to get a bar bent which should be easy and then clamp it to the existing bar much as the front anti roll bar on a Vauxhall Nova clamps to the front tie bar.
You wll need 4 clamps but it does have the advantage of being removable for normal road use.


Bob,

If clamping a 2nd bar what happens at the balljoint end? does this just get left short? :?
Were can we get these clamps from? or can you make them up?
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Re: Stiffer Anti Rollbar

Postby bobbrown » Wed 27.08.2008, 16:50

Monty wrote:Guys, can we Plz stick to the anti rollbar as thats the reason i started a new thread :roll:

If clamping a 2nd bar what happens at the balljoint end? does this just get left short? :?
Were can we get these clamps from? or can you make them up?


The roll bar is left short or the ball joint
Mild steel is of no use what so ever it has to be spring steel the same sort of stuff the original bar is made of.
Yes I can make up some brackets but will need the dimensions.
The additional bar should be easy to make up as it is only two bends in a straight bar so cost should be minimal.

I am talking to Eiback at present regards to springs and nodoubt the roll bars will come into this conversation.

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Re: Stiffer Anti Rollbar

Postby RayD » Wed 27.08.2008, 19:25

This picture may be helpful...
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Re: Stiffer Anti Rollbar

Postby Monty » Wed 27.08.2008, 19:43

Ray, thanks for the diagrame :smt023

Bob,
Will my local engineer place do Spring steel?

What about using my spare anti-rollbar, cut off the ends for the ball joints and the parts for the droplinks?
But if I/we decided to replace the stock one all together to go with a thicker diameter then we may need this one for to have sample to be made :?


Nige, did you buy that anti-rollbar of ebay?
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Re: Stiffer Anti Rollbar

Postby Monty » Wed 27.08.2008, 20:34

Here`s a pic off my anti rollbar, just had a measure with the digital calipers and it`s around the 14.5mm diameter
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Re: Stiffer Anti Rollbar

Postby bobbrown » Wed 27.08.2008, 23:05

My idea was to fit the bar for track days and remove it for road use IF that is what is required.
That assumes that a bigger roll bar is the way to go .
It only requires 8 bolts so it should not be too much of a hassle
If a bigger roll bar is the answer then this is the lowest cost option to find out, as making up a roll bar that is bigger or smaller as the case may be is a bit of hit and miss and expensive.
As you not only have the ends to worry about but also the drop link brackets.
It is often the case in the rally world (rather than race) is that more roll bar is required on gravel that on tarmac and it often the case that the roll bar is removed for tarmac stages.
I have a feeling that this may be an issue of shocks and springs rather than roll bars but my conversation with Eibach should make this a little clearer

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Re: Stiffer Anti Rollbar

Postby Don.Hasi » Thu 28.08.2008, 23:48

If you want to reduce the body roll on trackdays, wouldn´t it be better to make the front arb stiffer or do I have translated sth wrong? :smt017

I think, there are 3 dimensions concerning the arb: The material&thickness of the arb, its bushes, and the material/construction of the drop links (and of course... if you change only one thing of the handling... others will be waiting [suspensionbushes&Co] :wink: )

I have changed on my vx only the rubber from the arb with some teflonbushes and the handling has been immediately increased... more direct, more precisize. perhaps a simple way to improve the handling?

To improve the suspension with new springs, damper, arb, bushes, geometry... is a science for itsself...a great project!

Anyway, if you do some mods to it, I am interested too :)

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Re: Stiffer Anti Rollbar

Postby bobbrown » Fri 29.08.2008, 00:24

There are a lot of things that effect handling,
ride height (CG) springs, shocks, arb. caster, camber, bump steer, king pin angle, tyres etc etc.
It can be difficult to know where one should start, but I have a feeling the springs are the first point and that has to include the shocks and ARB as these are all directly related + if you lower the car then the caster and camber have to be readjusted as you have moved the suspension geometry.
The trick is to document all changes as you then know where to go back to if you get it wrong.
A stiffer rear ARB will stop body roll and the car may cock a rear wheel on corners, not so much of a problem on a FWD cars take a look at BTCC cars the differance between say a Honda and a BMW.
BUT I am not saying it is the solution in this case it may be it may not but is is certainly one of the cheapest places to start.

I can remember back to the 4 link system on the rear of the trusty Escort if you set this up correctly it would pull the cat down under power and hence more grip. get it wrong and it lifted the car less grip the geometry had to be just right.
Also With regards to the Escort although RWD a good race car had no ARB or a very soft one and the rally version did.
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Re: Stiffer Anti Rollbar

Postby Nige » Fri 29.08.2008, 12:45

Don.Hasi wrote:If you want to reduce the body roll on trackdays, wouldn´t it be better to make the front arb stiffer or do I have translated sth wrong? :smt017


As I understand it stiffening the rear anti roll bar on a FWD vehicle reduces body roll at that end and the effect on the handling is less understeer, conversely stiffening the front will reduce body roll at the front but will increase understeer. So it comes down to a question of handling balance and preference.

Body roll is not necessarily bad, it only becomes bad when it exceeds the ability of the suspension to keep the contact patch of the tyre firmly planted on the tarmac. When wheel lift or less than ideal whell contact is reached reducing body roll simply pushes the point that this occurs further out.
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