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Libra anti-roll bar specs 
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Joined: Mon Aug 18, 2014 6:07 pm
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Post Libra anti-roll bar specs
I’m beginning to feel the need for anti-roll, on the front at the very least. Searching back through posts 19mm diameter appears to be the consensus but what material spec and is that solid or seamless tube (wall thickness etc)?

One option is making my own, but failing that, who is still making them?


Thu May 16, 2019 9:45 pm
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Post Re: Libra anti-roll bar specs
I can certainly recommend the home made version - see my posts in another thread on ARB's

I used 7/8" dia (22.22mm) 2mm wall thickness cold drawn seamless tube for the front and 3/4" (19mm) 2mm wall thickness CDS for the rear.

Come along to Llandow on Saturday for a ride to see how they feel.


Thu May 16, 2019 10:44 pm
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Looking like a GTM

Joined: Mon Aug 18, 2014 6:07 pm
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Location: Devon
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Post Re: Libra anti-roll bar specs
Was that the post that involved spanners as blades? I’m thinking of a solution that involves me exercising the lathe to a similar effect as I too don’t want to pull the front apart to fit a bent tube.

Sadly I’m working on Saturday, sampling the delights of Yeovil no less. I am sort of based in Taunton a lot these days so would welcome the opportunity to have another look over your car.


Thu May 16, 2019 11:11 pm
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Post Re: Libra anti-roll bar specs
Rich wrote:
Was that the post that involved spanners as blades? I’m thinking of a solution that involves me exercising the lathe to a similar effect as I too don’t want to pull the front apart to fit a bent tube.

Sadly I’m working on Saturday, sampling the delights of Yeovil no less. I am sort of based in Taunton a lot these days so would welcome the opportunity to have another look over your car.


Spanner - Yes that's me!!

The Kitnet SW area summer evening pub meets will be arranged soon and at least one will be south from the Bristol area so could maybe meet up at one of those - I'll let you know dates. As you know the Yeovil area, do you ever go to the Haynes Museum breakfast meets? Was thinking of turning up at one of those this summer too.


Fri May 17, 2019 7:51 pm
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Looking like a GTM

Joined: Mon Aug 18, 2014 6:07 pm
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Location: Devon
GTM: Libra
Post Re: Libra anti-roll bar specs
sanzomat wrote:

Spanner - Yes that's me!!

The Kitnet SW area summer evening pub meets will be arranged soon and at least one will be south from the Bristol area so could maybe meet up at one of those - I'll let you know dates. As you know the Yeovil area, do you ever go to the Haynes Museum breakfast meets? Was thinking of turning up at one of those this summer too.


Would definitely be interested, I’ve been trying to get to a Breakfast meet for ages, I think I will need to book leave as I am almost always working or just coming off nights on the first Sunday of the month.


Sat May 18, 2019 9:15 pm
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Looking like a GTM

Joined: Mon Aug 18, 2014 6:07 pm
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Location: Devon
GTM: Libra
Post Re: Libra anti-roll bar specs
Just a thought, would 19mm with a 3mm wall at the front and 19mm with a 2mm wall at the rear provide a similar balance to using the larger diameter at the front with 2mm wall thickness?


Mon May 20, 2019 9:09 pm
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Post Re: Libra anti-roll bar specs
I can't claim expertise here but my understanding is the formula for polar moment of inertia (which equates to resistance to torsion) uses the fourth power of the radius. As such the metal that is furthest from the centre has a much bigger impact on the torsional stiffness than that in middle. This is why a solid bar of the same diameter isn't much stiffer in pure torsion than a hollow tube. When using a bent tube the bit in the middle becomes more important as it helps to stop the "tube" from crushing. If it is a straight torsion tube I think the wall thickness is very much secondary to the diameter as long as it won't crush. That is partly why I infilled mine with solid metal for the last 50mm, to resist the crushing forces where the spanners connect. Also makes for an easy weld as you can plug weld through the tube.

For expert advice I would really recommend a conversation with Dave Gallop at Track Developments. Luckily for me he is a member of my local area kit car club so I get to pick his brains for no more than the cost of a pint!


Tue May 21, 2019 1:40 pm
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Looking like a GTM

Joined: Mon Aug 18, 2014 6:07 pm
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Post Re: Libra anti-roll bar specs
I understood some of that! Thank you for the reply, making solid for the ends makes sense, and as you say, is easy enough.


Wed May 22, 2019 10:25 am
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Post Re: Libra anti-roll bar specs
You can buy a threaded insert to weld into std tube dia. for this purpose from McGill motorsports in Scotland
Ian


Wed May 22, 2019 3:56 pm
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