Bildon Motorsport rear sway bar for mk2...

I've been looking at adding a rear anti roll bar, or sway bar as the yanks call them for a while now, but being on a student budget, or now i'm graduated an unemployed budget, i've not been able to afford anything.

Now i've just come across this :http://www.bildon.com/catalog/DetailsList.cfm?ID=RSBA23&Nav=10&SubNav=none and i feel that with a trip to my local friendly ironmongers i could pick up the materials to make this for next to nothing.

So the reason i put the thread up is to ask whether you guys think this is a completely solid bar (it looks to be about an inch in diameter) or hollow with the ends capped off?

Also what's the thoughts on this type of set up as opposed to the more commonly found U-shaped bars that quite often seem to be hollow..?

 

i'd assume it would be hollow, as it would be pretty hefty otherwise!
I'd be interested in how well it works as like you say, it could be fabricated pretty easily!

 

Well i've emailed them for futher information on the specs of it, so will post up what i find out when/if i recieve it.

If it is solid bar, then it'll weigh a fair bit...

 

The end looks closed, so unless capped...

It will weigh a bit, but 50%/60% of a fully U-shaped rear solid ARB (Eibach, Neuspeed etc).

 

Have you managed to get anywhere with this?

Does anyone own the real thing? If so, is it worth it?

 

Nope not received a reply yet.

But i can get hold of some 1" diameter heavy walled tube from my local iron mongers on the cheap, so was thinking about giving it a go with that...

If i don't find it adds much stiffness to the rear, then i'll look at making a solid one.

I'll update if i get anywhere with it, but may be a while as i've got a leaking brake caliper to sort first .

 

Good luck.
I've never been a fan of tranfering twist in the beam of an axle to the welds holding it on, but, erm good luck.

 

Hi, there are a lot of opinions on rear beam mods, would be kind enough to explain what experience brings you to yours?

 

Yeah i have no doubt a weld on it's own could fracture when subjected to that sort of twisting force, but the construction of the Bildon rear sway bar doesn't only rely on the weld for strength. The torsional forces are transferred from the rear beam through the bolts (subjecting them to shear forces), which in turn transfer the force to the tubes that are inserted through the main torsion bar, which transfer the force via compression forces onto the wall of the torsion bar (causing it to twist).

The weld is there mainly to keep the torsion bar in the middle of the bolt tubes, thus keeping the bar closer in line with the axis of twist of the beam. It also serves to keep the shear forces at each end of the bolt tube equal.

The factory torsion bar of a mk2 rear beam is only welded in, and i have yet to hear of one of them fracturing.

Please elaborate on your previous comment in relation to the torsion bar in question.

 

You want to get someone to mill a hole in the bar so that the threaded sections are a press fit, this means minimal loading on the welds.

I would say go with some T45 hollow tube as most of the torsional stiffness in a bar comes from the material furthest from the centre, you could go up a little in diamater.

But what are you trying to achieve... look at ways to add grip to the front rather than loose it at the rear?

 

Yeah a milled hole would be ideal.

Well currently my car is fairly neutral, but will tend to understeer if pushed. I'd like to try and reduce this tendency, but without it biting me in the ass essentially. i.e not too much lift off oversteer!

 

you need to look at the rake of the car, front spring rates and castor angles then

 

I spent 2 years welding up about 300 beam axles a day.

 

From that link
"The Rear Sway bars are designed to increase the torsional rigidity of the stock axle on VWs."
Increase torsional rigidity, not absorb it.

because that stress is absorbed by the beam twisting.
It is not a factor on a normal arb as that stress is transfered to the arms of the axle.
With the factory fitted ARB it is welded into the arms not the beam. I would put money on it being for this reason.

 

What does that even mean? Absorb torsional rigidity? The bolt in torsion bar serves to resist the twist of the rear beam, by adding another member that by nature is designed to resist twisting forces. To an extent, again by nature of the material there will be a little absorption of this twisting force, but like a spring, the torsion bar is constantly resisting this and will want to return to it's unloaded position.

The factory torsion bar does exactly what i just described above, the fact it's welded into the arms and not the beam is entirely irrelevant, as it is still having a twisting force exerted on it, which is transmitted via a welded joint, which i believe was the main grievance you had with the Bildon item in the first place.

Did many of the axles you weld up fail then?

 

Hi Nordoff, just checking that you weren't a weekend warrior.

Hi golf nuts, you seem to have given this plenty of thought. Have you considered overlaying the main C-section of another beam onto your existing beam?
By this I mean to cut as much as you can from a donor beam and weld it to yours?

 

Well he certainly had some grievance with this thread, for whatever reason, who knows

Yeah i've given it a fair bit of thought, and i'm sure there are better solutions out there in terms of anti roll, but i was looking for a solution that i could fabricate in my garage for very little outlay and not lose out on if i don't like the outcome.

 

Brrr, play nice people.

Torsion bars...

Made by VW, H&H (old Mk1 roll bar kit makers), USA tuners, one-off requests down the local fabricators, all the way to home bodgers with some seamed conduit (which cracks in time).

Yes, you can make one, don't use conduit. The spec of steel I've seen used before on a home brew was EN16 (T)

 

H&H: