AMT top arms - strength

[mattcave]

Originally Posted by mininut

Out of the 100's of AMT frames made and sold across the world, has anyone in this community that WE know had a problem with their road AMT frame?? No... I didn't think so. :roll:

People are always too eager to slate a good product, especially competitors in the hope that they can take some business.

M.

Couldn't agree more. I think we've done a pretty good job of getting to the raw facts on this one which is what this community is all about really. Sharing facts, and dispelling myths.

ONE purchaser has had problems with ONE frame when used in somewhat non-standard circumstances. And AMT are up-front about it and have apparently been helpful in trying to fix the problem for that one guy. The fact that Andy has been responsive to the problem rather than saying "you must have mis-used it, it's not my problem" says a lot about his general attitude to his customers.

[mininut]

Originally Posted by mick

if Andy has sold at least a hundred frames that’s a grand each mmmm ,,,,fu me Andy got any jobs going ?

I believe Jeff Watson is the man making the money, his frames are £1500+ a pop and he'll build a car for close to 10k. Surprised he doesn't walk round with gold medallions and biatchs.

One thing that Andy does is take pride in his work, unlike a lot of people out there that'll sell you any old rusty apple that's just been chopped up and welded together.

M.

[PaulC]

Originally Posted by mininut

People are always too eager to slate a good product

M.

Pot.......Kettle........Black

[mininut]

Originally Posted by mintec

Pot.......Kettle........Black

what are you saying then? :roll:

[DaveCoxon]

Originally Posted by Andy@AMT

In the 8 years of making this frame we have never had any one ring up and say i have broke the top arm. and we have sold over 100. will some one show me one?

Originally Posted by Andy@AMT

Graham from Manchester, his arms had indeed bent at the rear but we have never this issue with anybody elsees race frame

The second time his arms bent (or rather the rose joint as you point out ) it had been trailed to Avon Park after the new arms were fitted. Three runs up the strip, with the heavy braking at the end (in order to get down the first return lane) and his joints were banana shaped. The new arms you made were an increased diameter aswell I recall - not just longer. Basic sense suggests this moved the 'failure' point to the next weakest component - ie the rod end. He now runs the highest quality aurora rod end, and the problem has not re-surfaced.

As you say though, he had clearly not set the frame up properly, as he never needed to mod the arm; so this could have had an effect.


*edited as i had worded something that could have been mis-interpreted very badly*

[ChadH]

Either way, one failure in over 100. That's less than one percent, and from what I've read, it looks like excellent customer service/after sales support was given too.

I think it's time this post was put to bed!

[mininut]

Originally Posted by ChadH

I think it's time this post was put to bed!

ZZZZZZZzzzzzzzzzzzzz......

There is obviously a lot of rumour going on here and I want to get the facts out as I know them. The bent top arm that everyone is talking about was on my car. It did not break, it bent safely, just putting the tracking and camber out. This happened at Avon Park in 2002. The car has an AMT race frame installed with coil over shocks.

I purchased the AMT race on the understanding that is was not tested for road use. I do use it on the road but in fact I've probably put 1000 miles on it in the last 3 years.

There is mention that the arms were set-up much longer than they were designed for. This is not true. In 2002 the suspension was setup as per AMT specification. After the bent arm incident I added 10.25inch brakes and shortened the King Pin offset to reduce the torque steer. To do this I used a top arm set-up 10mm longer than the AMT (standard) spec. I will go into more detail in a minute but I made these modifications after the bent arm happened.

I am a qualified mechanical engineer in the Automotive industry. I have access to FEA and also metallurgy measuring tools so I used them to understand why it bent and redesign the top arm. This is going to be boring apple for most of you but here are my findings:

There is a lot of stress on the arm because of the bottom location for the coil over. This puts a constant stress on the part that becomes greater under braking, cornering, pot holes and rumble strips etc. Now Andy told me that he had one failure on a hill climb car during development so a stronger steel was used for the 1/2inch thick rod and the problem was solved. I did a hardness check where the part was welded (the same place it bent) and the hardness, because of the heat, was down - probably similar to the original low grade steel. Although the strength has gone the advantage is it will bend instead of break.

I then built an FEA model of the suspension of the standard race frame suspension and applied standard Rover suspension loads to the model. These are the worst case design loads used for production cars. The stress was too high, but that's fine. It's not designed for the road and these are worst case scenarios.

I have limited knowledge of racing loads but I also began to look at the braking loads with slick tyres fitted. Nearly all the car weight can be on the front wheels. Braking alone with the grippy slicks takes the suspension to the limit of their safety margin so hard braking and hitting the rumble strip made me feel uncomfortable about driving the car. Is the FEA accurate? It's the best thing I had to work with, plus a bent arm sat on my bench.

I can't say by fact that the arm bent on the drag strip but I checked the car over before trailering it down to Avon Park that day and did not notice the bent arm, but it could have been. I believe that the arm bent at the end of the 1/4mile braking at 100mph. I do tend to brake hard at the end of the quarter. There are even pot holes coming round the return bend.

I want to get something else straight also. I contact Andy@AMT after the incident and after lengthy discussion he agreed to help solve the problem with me. He did not have to do so because I had used the frame on the road, so thanks to Andy for fabricating the stronger parts to my design. Yes they are longer to take my set-up for reduced torque steer and larger brakes. I also made sure that the location of the shock mount was cantilevered as little as possible and I used different spacers to do this.

I had a bent rose joint on the top arm in 2003. You can put this down to the longer arms for argument. I purchased some quality joints for that location and have not had a problem since.

If you have a road frame I think the suspension shock mount is different so I don't think there should be any problem with them. As Andy says it's the offset of the shocker mount that causes the problem on the race frame. If you plan to use it on the road buy a road frame. When all said and done I am happy with the workmanship of the AMT frame. The only weak point in design is the top arm ON THE RACE FRAME which is now sorted for me.

[mininut]

Something I found that RichSpec left of the old forum, just thought folk might find it interesting to see...


M.

[FatKev]

C'mon!

As the guy, who's car has been the topic of this thread, has said - it BENT safely!!!!!!!!!

How many of you VTEC boys with the al'mighty Watsons (scrapy Metro jobby with a fair amount of work done to it) subframes have had stuff fail?

I recall certain brackets snapping quite often.... not just bending... snapping, sheering, breaking!

I also like to re-itterate my previosu point - hammer these cars about and thrash em about all the time, stuff will break. No matter how well engineered something is, something is bound to break.... we all know this. Who cares a computer program said "this wont break..." it will at some point for some reason.

Also curious how often Rob Hall (Geoff Watson for that matter) has had failures during his tarmac rally events. Also wander the length of intervals between general strip down and rebuilds (of frame and so on, not just engine). If he can run the same car without taking it apart between events, I'll be gobsmacked and bow down to him

Just my general rant for today.

Now, as someone previously said, lets put this thread to rest.... getting fed up of some of the "jokes" getting flung about. Not so funny if the jokes were about your worksmanship\livelihood, now would it. :roll:

a rather disgruntled Kevin

[FatKev]

Do the whole quote and reply thing all you want. I'm just pointing out that no matter what frame you look at, they all have good and bad points, despite what certain people preach on here.

Erm isn't thos thread about the top arm? I dunno about you, but its not exactly the subframe as such, is it? Mind you guess it depends what you think the frame is. I'm talking about subframe kits as a whole.

Also I'm not going to re-read you last post. Just think if it was someone, even just in a funny way, was "joking" about your livlihood.

How can you do tarmac rallying and not have bits break? I don't mean in each event! Also don't tell me Geoff or Rob dont have to replace\repair various bits after enough wear and tear - all things engineered can and will break

I'm not backing AMT for any reason at all - I just think some of you guys are too eager (especially Mininut at times) to go nah nah :P my\his subframe is better cos this broke on subframe so and so. Instead of being peachs to one another, lets try and better the 16v community.

Note - this whole post (rant) isnt aimed at DarrenW. Also like to appologize for my harsh and inconsiderate tone in recent posts. Was just very annoyed. Sorry!

Kevin

[mininut]

Someone, please just lock the post now!! Or is there a specific pound of flesh that DW is after? :roll:

M.

[mini-GSI]

too much hear'say and conjucture is what was clouding the topic, the facts that are important have been stated and I think everyone has said their peice. if anyone has a problem (specific) maybe its worth posting it seperately or pm's. i think this thread should just be left 'as is'.....

my 2pence worth

[mininut]

Originally Posted by Richspec

if theres any bit i would beef up on the AMT frames its the plate that the tie bar mounts through, mine is bent, i suspect its flexing under pressure,

The reason I put the post from the old forum back in 2001 was to demonstrate that Rich’s frame was at one point setup correctly and he did reap the benefits of that then.

Consequently he’s done some tinkering with it and possibly introduced more stress to components with incorrect alignment.

Originally Posted by Richspec

Was talking with the other horlicksbrian AMT customer…Anyway he was telling me he'd had problems with the tracking wandering on his mini. He had taken it to some garage to find out what was going on. They said the frame had a weak point :roll: where the bottom arm etc mounts. His solution to this alleged problem has been to fit a bar right across the bottom of the frame as extra bracing….. I know I've had this problem before, but now my suspension's all over the shop, doesn't even measure the same side to side anymore so I can't say for definate mines not knackered somewhere.

So, we are let to believe that the guy in the garage that recommended the extra bracing was a structural engineer!!! :roll:

Originally Posted by Ian

On the rally car we inserted an upright to sandwich the bottom rose joint, other than that no other alts, it does run a sump guard which strengthens it up a bit.

Rallying as said before is not what the frame was designed for.


DW, All the points you have raised HAVE been addressed in previous posts. So please, can we just leave it now. I certainly won't be replying to any further posts.

M.

[Richspec]

Hi guys, been away all week so a quick catchup.

The other horlicksbrian AMT owner, he just added that brace cos a garage said the frame was moving, no proof before or after as to what was happening so its a total non event story wise, sorry!

I'll stand by that old post that maz found, it was a crackin day
however nothing has been altered apart from spring rates, the tracking was found to be altering all the time in later yrs, it was frustrating i could never get the handling to stay how i wanted, however the rear anti-roll bar was possibly the biggest plus for track use, can't comment on a diff as its still on the kitchen table waiting to go in :roll:

Big thanks to Andy for coming on and explaining what was what and to Graham for putting his side forward too, I'll have another read through when not soo knackered and see if there's anything i missed.

Rich