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Terra Firma fabricated radius arms. Any concerns ?


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Excuse my ignorance of British offroad equipment MFG's, but I recall a few years ago that Scorpion brand fabricated radius arms, among other of their products were heavily criticized on this forum due to welding and material failures. There are a few blokes over here now fitting Terra Firma castor corrected fabricated radius arms and I was wondering if any LR4x4 Forumites have any experience ,good or otherwise with them ?

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qt-ultralight-radius-arms-150-p.jpg

terrafirma-tf528-caster-corrected-front-

They look very similar to the QT ones (which were reported to fail) but have a wrap welded round the bush. The bush looks very thin to me, were the qt ones used to break. Also, the section area from the second bush to the bottom of the arm looks very minimal to me, but at least they didn't cut holes in this area like the qt. To answer your question, I have no experience with these, but I wouldn't use them myself.

Daan

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I wanted to 'like' your post Daan, but i'm informed that I have reached my quota blah blah. I have not ever been able to 'like' a post since the 'like' facility was introduced.

I could be wrong Bill but I have a feeling that the 'like' button only works for supporters, I don't know the reasoning behind this.
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yeah, you have to be a supporter in order to like. by the looks of it the terrafirma arms seem to be designed with function in mind more than the QT ones. which to me seem to have been designed to look pretty, and the DE obviously had a fetish for speed holes. because its a proven fact that each speed hole produces an extra 2BHP

now for the sad bit.

17 holes per arm on the QT arms, plus the laser cut logo which adds 5 extra BHP, a total of 90BHP increase over standard. where the terrafirma arms only have 6 holes each, equating to a more respectable 30BHP increase.

maybe the extra 60BHP is also a contributing factor in their failiure....

i would still like to see a tiny bit more beef around the bush holes though on the terrafirma ones!

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No experience of the QT versions but I looked at the TF ones alongside the some Britpart versions in a shop a few years ago.

The Britpart versions were slightly heavier, the welding looked better and there was more metal around the bushes in comparison to the TF ones so I bought the Britpart versions and saved £20.

Despite fewer holes and the associated BHP losses, they are available in yellow which will double your 0-60 times when used in conjunction with a K&N sticker and some fuzzy dice.

To throw a curveball, Gwyn Lewis used to crank your standard radius arms by 3 or 6 degrees for about £60 but I lack the engineering knowledge to make any judgement on the strength/durability of those items.

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in fairness to the qt ones a lot of them were used in off road racers doing silly speeds on tough surfaces , and from memory were they not replacing them free of charge if there was an issue and once the problem was brought to their attention they changed the design

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A bit of googling showed a few of scorpion, and QT. to be fair to terrafirma; I have not seen one of theirs broken yet, so there might be hope it is stronger. We dont know material thicknesses and strengths, so it is hard to predict from the picture.

I have tried to like you bill, but try as i might, my pc froze at that thought. Dont take it personal, mate...
Daan
edit: I just manage to 'like' your post!
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  • 2 weeks later...

The big problem with TF is the quality

As a product becomes more popular, so manufacturing is shifting to cheaper and cheaper suppliers

The shocks are a good example with trade prices being in the sub tenner range for the big movers. The Receiver hitches have gone the same way and are now officially utter rubbish

Pod used to buy the Scorpion (now Extreme 4x4) radius arms, then plasma cut a couple of 6mm silhouette plates out to hot glue to the sides - it worked very well

I would talk to Gwyn

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Having looked at these and run FEA (Stress Analysis) on models of both the original forged and after market fabricated arms, you see what a terrific piece of engineering the original arms are! The standard arms have a fairly small safety factor as it is for the worst conditions (which I considered to be the tyres hitting a step at 20mph and the vehicle decelerating over 10cm with the compression of the tyres - just as a guess).

None of the fabricated arms will survive this and I am concerned they will also suffer from fatigue failures long term.

They may well last well with normal usage - but it's what happens in a crash or similar incident that concerns me the most. The vehicle will be difficult enough to control in the few seconds after even without the arms folding up / snapping.

In short, I wouldn't touch any of them with a barge pole!

Si

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I have had 3 sets of QT front radius arms and they are junk, all bent, useless, don't ask why I went back for more.

Saying that I have also bent 3 (to date) standard radius arms (which are in my humble opinion by far the strongest) but in all fairness to LR have not bent a front mounting point,

I have however bent 2 different Disco chassis's at the rear mounting point for the trailing arms.

Point being, something in the chain will have to bend at some point, depends what you want or expect of them.

But if you fancy a playday or green lane day with inferior aftermarket arms fitted don't forget you have got them and they are not bombproof, or in some cases as strong as the standard ones.

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I have QT 6' correction arms on my 110, from the above posts they seem to be the later type with no laser profiling between the two axle bush holes, They were fitted before I bought the vehicle and tyey're still going strong five years later.

After carrying out an engine conversion I now have an extra 350KG sat over the front axle so I will be looking to upgrade to 'Beefier' arms.

On the market there seems to be three types of arms that take my fancy, Gwyn Lewis std. corrected arms, Adrenaline 4x4 and W.K.D. Off Road arms which are solid and are going to be bent no time soon.

http://www.ebay.co.uk/itm/LAND-ROVER-FRONT-HD-RADIUS-ARMS-CASTOR-CORRECTED-CORRECTION-HOCKEY-STICKS-/181477577370?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2a40e8129a

post-47238-0-60083600-1406698405_thumb.jpg

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Point being, something in the chain will have to bend at some point, depends what you want or expect of them.

Defiantly this ^ I did run the old scrap iron arms and they worked fine for years on my green lane disco and then comp truck but as speed on my comp truck got faster I found they bent far to easily. I now run the Terrafirma arms and found then to be much stronger but every thing has a limit.... here is the result of clipping a tree at 30mph....

post-1650-0-57296900-1406715438_thumb.jpg

snapped the caplier, broke the front swivel, bent the radius arm, cracked and pushed the center backwards on the chassis mount.

post-1650-0-24181800-1406716421_thumb.jpg post-1650-0-14811200-1406716443_thumb.jpg

Personally I do think these arms are strong enough for my intended use abuse.

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Hi the only concern I would have is the loss of strength at the bend due to the annealing (heating), cold bend is no good as the bottom side will stretch and prob crack. Check with a decent heat treat shop first before before annealing the arms. Regards. Ian Ashcroft

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