interesting response from QT

[white90]

I will admit that the lower unsprung weight will benefit handling. It is how much that gets me. If a front axle assembly weighs 300kg (for arguments sake) and you lose 3kg, you have lost 1%. Sod all difference.

So if the handling or roadholding isnt much better, why fit them? Castor correction is the only other reason i can think of, but you can correct castor with modded standard ones from GL, or with eccentric bushes in standard arms.

I still dont get them. Is it just because people like the look of them?

I don't and didn't like the look of them but the alternatives were even worse.

[BogMonster]

It seems that this thread has served a very important purpose in getting people to check there arms and has hopefully helped to prevent a nasty accident or two.

If it prevents just one accident it has been very valuable IMHO.

[custom-conversions]

Lovely aren't they. IF i won the lottery i'd have a 90 with the full EQUPE set up on there!

Like i said the others seem a poor copy.

They certainly look well made. In fact the fit & finish of all their products looks very good but like you mentioned you need to win the lottery first.

Its interesting to see that they aren't drilled around the axle bushes, QT's obviously tried to save a little more weight on their early arms.

[bobtail84]

I've spent a couple of cold hours under the RR with my mate KK who donated his spare 6deg QT's to the cause so I can go to work on Monday.

This is the O/S

This is the N/S note the small crack. It's on both side's.

Just for the record I fitted the QT radius arm for the caster correction not for bling or any such nonsense. The 6deg that I fitted today are the later type with no holes between the bushes and I will be looking to replace them IF I can find something better.

Jeff.

[white90]

Glad you and others will check these arms.

I will check mine very carefully and luckily have some standard ones to be fitted(awtg collection)

[Holyzeus]

Only checked one side but the crack is similar to Jeff's

[white90]

Well not wanting to appear to be leading a witch hunt,

Once I get a reply from QT I will report back on what is said

then gather members details of those with affected items and advise QT.

[66gaza]

I would be interested to know if anyone has had trouble with the newer ones without the holes inbetween the bushes, as I have a set of these in the

garage awaiting fitting and will now wait for conclusive news that they have fixed the problem.

Gaza

[ciderman]

I would be interested to know if anyone has had trouble with the newer ones without the holes inbetween the bushes, as I have a set of these in the

garage awaiting fitting and will now wait for conclusive news that they have fixed the problem.

Gaza

No trouble with the later ones cracking , I have a set and have bent them about abit , But thats not suprising if you have seen my driving

[Hybrid_From_Hell]

^^^

Yes I have and thats a fair comment

Seriously tho

These arms take huge abuse.

There is the fact they loacte the axle front to rear.

then they also have pressure top to bottom, but

the real forces come into effect on a cross axle twist off road

Christ knows (or Bishbosh ) the forces involved but

I did the trick of removing a bolt from one arm off road to see

just how much articulation I got - er its huge, ...just as Simon R said , but do it

then get undfer the truck and see just how far the hole is now out of alignment

you would be stunned.

That means that with all 4x bolts in there the arm in taking that and their can be fatigue via constant loads on off and

twisting force and why the LR arms are as HD and cast lumps as they are, they move from narrow bushes / arms

to bigger / wider arms and bigger wider bushes as they found the bushes in the narrow ones wore fast

so why would you take such a massively stressed unit and repace with some like the QT arms is beyond me

Jeff - thank gawd you DIDN'T do that long high speed high rpm Datalog for me - give that computer that had its battery die

a kiss and a cuddle.

If I had a set of these I think I'd be using a taxi to go to work, that more than 1 member / post that has a problem, and this could easily

be a killer / accident waiting happen. as to if QT replaces that up to them, have a think about how worried you are about these if you have them

and sort yourself out accordingly. Take control of your own circumstances and don't repkly on others / QT for your saftey, make your own calls.

For the record I use std arms, and with quite heavily modded suspension also gave up with polybushes for similar reasons, when sqezzed big time they split

and self destructed now back to std bushes too

Nige

[forkrentfitter]

just read this start to finish,please don,t hang me but were these ultra light arms not originally designed for ccv trialers and comp safari trucks,which tend to weigh in all up at about 1700kg,s? just as an observation all the trucks shown seem to be challenge type trucks,i guess going something like 2500kg plus,running minimum 33" tyres,not 205 type such as racers run? i know qt have a duty of care because they are selling them,but perhaps mr marsh will say they were not designed for this type of use?.i have no connection with qt,i hate scrap iron with avengance,just taking a subjective view of this thread. hat,coat,run.

[ciderman]

I bought mine from Qt at sodbury a couple of years ago , I asked the young sales chap on the stall what were the designed for , The answer was well the 3 degree ones are for land rovers with a 2" lift , the 6 degree ones are designed with a 4" + lift in mind .

With that sort of lift in mind I guess a Comp racer wouldnt fit the bill .

[streaky]

Well not wanting to appear to be leading a witch hunt,

Once I get a reply from QT I will report back on what is said

then gather members details of those with affected items and advise QT.

Tony.

Back in the Team Saluki Defender days we bought three pairs of arms from QT's. They all had the holes drilled and two pairs soon developed cracks.....they were replaced FOC by another two sets ...again with holes drilled.

There was no mention of them being pre-production models...Dave know's us very well and he's also very much aware of what the arms are going to be subjected to.

I've had a set of drilled ones on the Disco for five years now...they take a hell of a pounding and show no signs of cracks etc.

I'm sure he'll reply after the holidays....a good company always does.

S.

[forkrentfitter]

I bought mine from Qt at sodbury a couple of years ago , I asked the young sales chap on the stall what were the designed for , The answer was well the 3 degree ones are for land rovers with a 2" lift , the 6 degree ones are designed with a 4" + lift in mind .

With that sort of lift in mind I guess a Comp racer wouldnt fit the bill .

i stand corrected,your comment makes sense.

[bishbosh]

Thank you Nigel, but religion is not my thing . I like my facts to be slightly more calculable

All these failures in my opinion from the photos posted are initiated by fatigue. Off road stresses are a minor concern. The repetitive cycles of loading experienced during normal motoring will have caused the majority of the damage. Then a large knock (perhaps off road) is all that is needed for failure to occur.

Comparing a welded detail to the cast detail of the original LR arms you are always going to struggle to compete on fatigue life.

Outright strength is probably fine, in fact, Jase's comment that his arms havee bent under abuse but show no signs of cracking supports the theory as his truck doesn do many road miles so the fatigue cycles are greatly reduced.

Oooh I need a lie down, too much brain work for a Sunday morning!

[B reg 90]

I will admit that the lower unsprung weight will benefit handling. It is how much that gets me. If a front axle assembly weighs 300kg (for arguments sake) and you lose 3kg, you have lost 1%. Sod all difference.

So if the handling or roadholding isnt much better, why fit them? Castor correction is the only other reason i can think of, but you can correct castor with modded standard ones from GL, or with eccentric bushes in standard arms.

I still dont get them. Is it just because people like the look of them?

The reason for the wieght saving is the ebd result - Daan's truck is only ~1700KG with roll cage and winch if I remember right. That was 280Kg lighter than mine before I stripped it. That 280Kg is enough to make the difference between sinking in a bog and driving up a hill or not. It makes a massive differance when you compare a lardy motor with a light one side by side - both had the same tires and 200/300tdi's.

I once nievely asked Daan where he made the most weight saving - the answer was every where as shown with the radius arms. When you look at the effort involved it is imense - but he is right - it is worth it if you have the time to invest.

It also reduces the strain on your axles.........

Adrian

[HoggyN]

Has anyone got a CAD model of the fabricated arms?

[Dave W]

As far as the weight saving aspect is concerned it's not a great weight saving in itself but when you remove a similar amount of weight from all the components in the vehicle it can soon add up to a substantial saving. The important bit is to make sure you don't weaken the structure in the process obviously.

Have now carefully inspected my Britpart arms, no sign of any problems, they aren't drilled under the axle (couldn't remember f they were or not) and the drilled area stops about 4 inches short of the first axle bush.

[Turbocharger]

It shouldn't be hard to make your own CAD model - two flats for the top and bottom of the arm, a flat with some holes in it for the web, two tubes for the bushes at the axle ends and some curved flat + profiled web for the area between the two bushes.

The issue with making a model and running it through FE is the same as Dave Marsh has had when he's done his own stress analysis - either by computer, on paper or in his head (and I may be doing him an injustive by assuming it's the latter). The issue is that we don't know the loading case and material properties accurately enough. The model will only tell you what we already suspect - that the fatigue life of the material between the two bushes isn't enough for the work these vehicles see.

I'm not certain that Mr Bish is 100% on the nail, since my feeling is that cyclic road loads won't be as significant as cross-axling, for the reasons that HFH gives above. Offroad, as one wheel lifts and another sags slightly the stress on the bushes is massive. On the road, the load that dominates these arms is bending as the hockey stick stops the axle from rotating under braking or acceleration forces. OK, the failure is fatigue and that means a lot of cycles at low stress but my gut feeling is that the offroad condition (fewer cycles but at much greater stress) is more significant than on-road loading.

[HoggyN]

The issue with making a model and running it through FE is the same as Dave Marsh has had when he's done his own stress analysis - either by computer, on paper or in his head (and I may be doing him an injustive by assuming it's the latter). The issue is that we don't know the loading case and material properties accurately enough. The model will only tell you what we already suspect - that the fatigue life of the material between the two bushes isn't enough for the work these vehicles see.

Agreed, but it may indicate where next weak point down the line is. Removing the holes might just move the failure point to somewhere else.

[FridgeFreezer]

I'm not certain that Mr Bish is 100% on the nail, since my feeling is that cyclic road loads won't be as significant as cross-axling,

I'd tend to disagree there - part of the function of the arms is similar to the anti-wrap I've got on the 109 (in fact I seriously considered using hockey sticks in the design at one point), and when you think about the forces on the arm during normal driving they're pretty big;

-When accelerating or braking, that arm has to resist the turning moment of the axle trying to spin the other way - imagine the forces on a grippy road if you stand on the brakes, that arm is the only thing really deciding whether your wheels stop turning or your axle goes round and round adding big tyres into the equation greatly increases the leverage.

-When hitting a bump at 70mph it's got ~250kg+ of axle/wheel/tyre yanking it up and down repeatedly

-It's also being pushed backwards or yanked forwards again by braking & acceleration / bumps in the road

Comparatively, when driven at lower speeds off-road it's having a far easier time of it, the major loading will be on a climb when the axle will want to wrap (on the 109 it was always the front axle what started to hop about on a climb) but it's not seeing the repeated high-speed jolts and sharp shocks that Bish is describing.

[smo]

Agreed, but it may indicate where next weak point down the line is. Removing the holes might just move the failure point to somewhere else.

Without doubt but to model it we would also have to add the welds as they are when fabricated as they form an integral part of the arm and would change the results significantly. I'd hapily model and run FEA on them but i dont know the material spec for them, also the bushes used would change the loading results depending on the hardness.

[Daan]

The reason for the wieght saving is the ebd result - Daan's truck is only ~1700KG with roll cage and winch if I remember right. That was 280Kg lighter than mine before I stripped it. That 280Kg is enough to make the difference between sinking in a bog and driving up a hill or not. It makes a massive differance when you compare a lardy motor with a light one side by side - both had the same tires and 200/300tdi's.

I once nievely asked Daan where he made the most weight saving - the answer was every where as shown with the radius arms. When you look at the effort involved it is imense - but he is right - it is worth it if you have the time to invest.

It also reduces the strain on your axles.........

Adrian

As far as the weight saving aspect is concerned it's not a great weight saving in itself but when you remove a similar amount of weight from all the components in the vehicle it can soon add up to a substantial saving. The important bit is to make sure you don't weaken the structure in the process obviously.

Have now carefully inspected my Britpart arms, no sign of any problems, they aren't drilled under the axle (couldn't remember f they were or not) and the drilled area stops about 4 inches short of the first axle bush.

Yes, the issue of weightsaving is that it has to be done on the entire car, as mentioned by Adrian. So, in my case, 3 kg is not a lot but you have to do this kind of effort everywhere, and than it has a result. Iirc, the QT arms were about 4kg saving each, so 8 kg total. Worth having if they were reliable which they are not unfortunately. Q for Dave White, do you know the weightsaving on the Britpart arms?

With regards to the strength, I am pretty sure braking is the big one here; think about 70% of braking force at the front axle, with some 35" tyres trying to lock up on a tarmac road, and its pretty lethal.

Daan

[Yostumpy]

One obvious thing that has NOT been mentioned! If you have these fitted to a road vehicle, and you have NOT ticked the 'any modifications' box on your insurance ,and then your out and about, it snaps, and you kill others in an accident, I would think you'd be more than likely to end up inside, for driving an unsafe vehicle. Ring any bells of late!!!!!!!!!. So you inform the insurance co. tommorrow and pay the premium, or you dont and pay the consequencies! Sounds very melodramatic, but these are obviously a disaster waiting to happen. Imagine a comp safari, it snaps, drops, digs in the ground, polevaults the vehicle and occupants into a tree, 15ft in the air! All I can say is if you have a component on your vehicle, that has a history of defects, ur MAD

[Turbocharger]

-When accelerating or braking, that arm has to resist the turning moment of the axle trying to spin the other way - imagine the forces on a grippy road if you stand on the brakes, that arm is the only thing really deciding whether your wheels stop turning or your axle goes round and round adding big tyres into the equation greatly increases the leverage.

-When hitting a bump at 70mph it's got ~250kg+ of axle/wheel/tyre yanking it up and down repeatedly

-It's also being pushed backwards or yanked forwards again by braking & acceleration / bumps in the road

I'm with you on that, but my thought train is thus:

In braking/accelerating, the axle's trying to rotate and the hockey stick resists that with both bushes - they share roughly half the work and they both try to deflect the long straight part of the stick (the 'handle' of the hockey stick') into a curve. This wouldn't heavily load the area between the bushes where we've seen the failures.

In cross axling you're trying to rip one or other mount off the axle, and this fully compresses the bushes vertically in opposite directions. This puts a curve in the handle of the stick in the same way as braking (well, one in each direction), but there's a big bending load in the curved part of the stick too.

I'm quite willing to promote intelligent discussion like this though - I've never dealt with Mr Marsh but if he plays his cards right, a solution might present itself on here for free from some free consultancy group thinking. Until he suggests his chosen way forward it's a little premature for any of us to start pointing the finger.