ashg
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| posted on 20/3/10 at 05:08 PM |
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it will if the pressure changes which is a given. but we are talking about tension here. i think the best solution is that i get the broken part back
to rally design and they can let the manufacturer's engineers have a look at it under a microscope to see what happened.
6082 properties indicate that its stretch capability isnt as good as steel but should still be fine.
the ultimate tensile strength of 6083 aly is 310MPa where as an 1018cd steel is around the 485MPa mark.
looking at the sums in matlab its looking like the ali should be strong enough which is why my broken one needs to be looked at.
have never claimed to be a materials engineer but have a good interest and work in an area of industry that considers these things daily (do a search
on Linac and you will see what i mean).
i for one like an open debate but if it starts to get out of hand i will delete the whole thread. Pointing fingers is a useless exercise, rarely
achieves anything and just doesn't interest me. look at the politics of this country!! most of our MP's are uneducated fools that spend
all day finger pointing do we want to be like them? 
[Edited on 20/3/10 by ashg]
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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ghostrain
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| posted on 20/3/10 at 06:20 PM |
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Camber adjuster failure
ashg...you started your thread with words like catastrophically failure and lucky you and Chris are to be alive and are now surprised that many others
are very worried about this failure.
I suspect that the majority of 7 style kit cars built in the last 5 years are using this design of top wishbone/drag link. You surely cannot be
surprised of the reaction to your posting.
Given your knowledge of the materials industry and the design of your front suspension why do you think your adjuster failed?
I tell you that the guys at Rally Design were very worried about your failure,their engineers in conjunction with Darryn from GTS spent most of the
afternoon trying to simulate what caused this failure without any firm conclusions.I was given very open access to their test and conversations,they
hid nothing.
The good thing,so far,to come out of this discussion is that your failure appears a one off and also no harm to you.
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MikeRJ
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| posted on 20/3/10 at 07:57 PM |
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quote:
Originally posted by eddie99
Hang on a second, Fatigue doesn't affect materials which are under constant pressure does it?
Err...that's what I said (in the opposite sense).
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Toltec
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| posted on 20/3/10 at 09:07 PM |
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quote:
Originally posted by ghostrain
ashg...you started your thread with words like catastrophically failure and lucky you and Chris are to be alive and are now surprised that many others
are very worried about this failure.
I think he was feeling pretty bad that I was driving the car when it happened and it could have been very serious.
The failure of the component was catastrophic in the sense that its function was totally impaired not in the sense it caused a catastrophe. As to why
it happened? A defect in the material maybe? Someone has already mentioned the possibility that the anodising could make the chance of cracking
higher. It failed at the end of the ball joint thread not at the hex head.
We have just had a long chat and come up with an idea of how to use these adjusters in a way that prevent the possibility of this kind of failure.
Ash is going to draw up the modification and see if it still makes sense. I might suggest he runs it past RD/Darren to see what they think.
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ashg
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| posted on 20/3/10 at 09:23 PM |
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have been thinking about it and it could actually be the design of the haynes wishbone that caused it. the tube that the adjuster sits in is actually
angled upwards at 8 degrees from the wishbone, im wondering if this could have caused the problem as it would move the stress points on the
adjuster.
either way i have revised the design of my tube that the adjuster sits in. i have now put a recess inside the locknut end so even if the adjuster
failed a second time it couldn't pull out.
here are some pictures of my new design.
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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arriba
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| posted on 21/3/10 at 08:03 PM |
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Possible reason for failure
Having had a chance to read through this thread and consider all the submissions I think a possible cause of failure is as follows.
The transit drag link joint does not have a limitless range of travel,without site of the manufacturers drawings I estimate it is in the range of
plus/minus 20 deg.
Ashg has stated that the joint is installed on his roadster at 8 deg to the norm. If this is using up the range of movement on bump it is possible
that at extreme bump the joint is locking out. The upright would exert a moment effect on the drag link threaded stem,the extreme of the load being at
the inboard end of the thread,exactly where the failure occured. The effect of such a hammering would be greater if the adjuster where held only
loosely in the housing tube,our current potholed roads giving greater opportunities for this hammering action. I use the word hammering for clarity
because the upright could be considered the handle of the hammer and the drag link stem the head.
A simple check to verify this theory would be to remove the spring/shocker assembly and rotate the suspension unloaded,it should be obvious if the
suspension is exceeding it's normal range of rotation.
Such a lock out is not rare-I was previously involved in the supply of high quality 5/8 x 5/8 chrome moly rod ends to a well known race car builder.
The designer used the rod end directly in place of where the drag link joint is used. On the first the loaded rod end failed in the first corner,the
designer had underestimated the range of movement of the suspension and had exceeded the angle of misalignment of the rod end,we cured the problem by
using high angle rod ends.
The massive 18mm stem on the transit drag link is unlikely to fail but if lock out is occuring then it is inevitable that the metal to metal contact
will cause some failure in the system
Rally Design
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ashg
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| posted on 21/3/10 at 08:19 PM |
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it could be possible but the 8degree angle is to improve the range of motion. the 8degree is there to make sure the ball joint is central.
its a shame that chris gibbs has been banned from here as he was involved in the suspension design. im sure he could add some interesting points to
the conversation.
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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arriba
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| posted on 21/3/10 at 08:56 PM |
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possible reason for failure
I have a lot of respect for Chris Gibbs,I am sure he has calcualated the range of movement,but the range of movement on droop is not so critical,in a
vertical mode it only has to support the unsprung weight of the vehicle,it is the bump that is the critical range and load.
Having said that it is likely that it is a combination of factors that led to this failure but with one primary catalyst.
I noticed that you intend to manufacture new steel adjusters with 1 mm additional diameter,how were you intending to machine out the wishbone tubes to
accept the larger diameter. You would need a gap bed lathe to mount the welded wishbones or alternatively an adjustable reamer,which is rare and
expensive,they would be difficult to hold in a pillar drill,would seem a difficult retrospective task.
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arriba
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| posted on 22/3/10 at 02:08 PM |
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I think this problem has been discussed enough for everyone to understand the result of the failure, but as yet no definate cause.
Please find photos of the crude test that we employed to try to achieve max static radial load into the adjuster. We only used a pipe wrench for that
was the longest lever we had available.
You can see in the second photo no obvious damage to the adjuster despite the high tension load we exerted.
I must be honest and say that I am surprised that this aggressive load did not tear off the nut head of the adjuster.
The nature of ashg's failure suggests flex in the adjuster, but such flex cannot occur if the adjuster is a good fit in the wishbone tube. It
is possible that view of the other adjuster on the other side of the vehicle may reveal more. For if it is set up similarly that also must be showing
signs of failure.
See my previous postings for suggestions of other reasons or complimentary reasons for ashg's failure.
Rally Design
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ashg
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| posted on 22/3/10 at 07:19 PM |
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fortunatly for me i have a gap bed lathe so its not a big issue to over bore the wishbones. i agree with you that its not easy to destroy one. im
considering fitting a new set of ali adjusters first to see if i can replicate the problem again. obviously i keeping a better eye on the
adjusters.
i do really appreciate that you are concerned about the failure, if i didnt work all week i would drive down and show you the parts.
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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Toltec
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| posted on 22/3/10 at 08:09 PM |
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Just a thought-
Ash, when you tightened the adjuster did you rotate the lock nut or the adjuster? Off hand I would assume the adjuster as turning the lock nut would
alter the setting.
If so would the friction between the threads be high enough to cause a significant torsional force on the adjuster at the end of the ball joint
threads just where it broke?
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craig1410
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| posted on 22/3/10 at 09:08 PM |
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quote:
Originally posted by Toltec
Just a thought-
Ash, when you tightened the adjuster did you rotate the lock nut or the adjuster? Off hand I would assume the adjuster as turning the lock nut would
alter the setting.
If so would the friction between the threads be high enough to cause a significant torsional force on the adjuster at the end of the ball joint
threads just where it broke?
I would hope that he tightened the locknut because the aluminium head of the adjuster is certainly not designed to rotate within the steel wishbone
sleeve under load as this would tend to cut into the adjuster.
I don't have camber adjusters on my car but I would expect the process would be something like this:
1. Note the current camber angle and desired angle
2. Slacken the locknut
3. Adjust the adjuster by whatever number of flats or turns you have learnt from experience will yield the required change.
4. Tighten up the locknut again.
5. Check the result and fine tune if necessary.
Also, I would think that the difference in camber angle between having the locknut spun up by hand and fully torqued would be well under 0.5 degrees
so not difficult to deal with.
[Edited on 22/3/2010 by craig1410]
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Toltec
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| posted on 22/3/10 at 09:41 PM |
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quote:
Originally posted by craig1410
quote:
Originally posted by Toltec
Off hand
I would hope that he tightened the locknut
It is the lock nut after all, being less off hand there is no reason why there would be less movement tightening the adjuster so you are quite right.
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Neville Jones
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| posted on 23/3/10 at 07:23 PM |
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Whatever the cause of this failure is, the fact that the thin ali tube is loaded in tension, and operates cyclically, is extremely poor design and
materials spec.
Like the poorly designed wishbones, which seem to have disappeared, these ali 'adjusters' need to go away, and be replaced with something
more substantial, and sensible.
Maybe they need a load and use warning, just like the ali uprights which fail.
Cheers,
Nev.
Rally Design,
Have these items been checked, and approved, and signed off by a Chartered Engineer? Please show a copy of the relevant Certificates of Approval.
He'd (The engineer)better have very good liability insurance.
Also, Have the ali uprights yet been properly tested, checked, and signed off by a Chartered Engineer? Again, please show the relevant documents. And
sorry, a certificate for heat treatment doesn't constitute a certificate of fitness for use.
You people will lose everything you own, if you keep selling this stuff, knowing it's going on the road. It's all very good saying
it's not for road use, but if you know it's going on the road anyway, you have a duty of care to ensure the items are safe, and tested
properly.
[Edited on 23/3/10 by Neville Jones]
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snapper
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| posted on 23/3/10 at 09:28 PM |
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Camber adjuster failier on Haynes Roadster warning
Don't know if this has been posted but it looks scary to me.
Haynes thread
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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daniel mason
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| posted on 23/3/10 at 09:30 PM |
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it has!
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Paul TigerB6
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| posted on 23/3/10 at 09:30 PM |
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sure has - few pages for you to catch up on
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Paul TigerB6
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| posted on 23/3/10 at 09:46 PM |
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Just had a read right through myself. ONE failure out of 1000+ pairs sold and it amazes me how many people are ready to start screaming for a
product withdrawal / recall / bad design causing failure etc!! Ridiculous really!!
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DRC INDY 7
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| posted on 23/3/10 at 09:47 PM |
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This thread needs to be deleted there is one running allready
https://www.facebook.com/groups/462610273778799/
Puddle Dodgers Club
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twybrow
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| posted on 23/3/10 at 10:35 PM |
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On the first pic shown - what are all the circumferential scouring marks on the tube? That suggests to me it was spinning in the wishbone at some
point - either when in use, or during installation. Anyone else care to comment?
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mistergrumpy
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| posted on 24/3/10 at 12:53 AM |
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quote:
it amazes me how many people are ready to start screaming for a product withdrawal / recall / bad design causing failure etc!! Ridiculous really!!
+1.
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turbodisplay
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| posted on 24/3/10 at 07:42 AM |
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Not really, if it is made out of ali, which it looks like but no one person actually confirmed, it probally will fail again.
Ali will fatigue, as the millage goes up it will happen again.
My brake brackets were made out of steel, as I want to err on the side of caution, even though the calipers themselves are ali.
The difference is that ap racing will have stress tested and specified the correct grade of ali.
Darren
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Staple balls
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| posted on 24/3/10 at 07:55 AM |
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quote:
Originally posted by turbodisplay
Not really, if it is made out of ali, which it looks like but no one person actually confirmed, it probally will fail again.
The difference is that ap racing will have stress tested and specified the correct grade of ali.
I thought it was confirmed repeatedly that it was aluminium, and that it was HE30 6082.
Course, it'd be a shame to let facts get in the way of a good bit of drama 
[Edited on 24/3/10 by Staple balls]
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iank
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| posted on 24/3/10 at 08:01 AM |
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quote:
Originally posted by turbodisplay
Not really, if it is made out of ali, which it looks like but no one person actually confirmed, it probally will fail again.
Ali will fatigue, as the millage goes up it will happen again.
My brake brackets were made out of steel, as I want to err on the side of caution, even though the calipers themselves are ali.
The difference is that ap racing will have stress tested and specified the correct grade of ali.
Darren
+1
The concern is that they will all fail at some point in the future due to the properties of aluminium and/or the design.
So that's 999 more cars having their wheels fall off at some unknown point in the future. How many deaths could that cause? Might even attract
the attention of the red-top press to 'those lethal homemade cars' at which point politicians start trying to ban our hobby.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Paul TigerB6
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| posted on 24/3/10 at 08:16 AM |
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quote:
Originally posted by turbodisplay
Not really, if it is made out of ali, which it looks like but no one person actually confirmed, it probally will fail again.
Ali will fatigue, as the millage goes up it will happen again.
But as said there are various grades of ali so you cant just make a sweeping generalisation as soon as ali is mentioned. If that was the case then
there's thousands of planes all made out of ali that are all going to fail at some point. Thing is though they all have a certain life and to me
these camber adjusters probably should be treated the same - as a service item that you replace after x,000 miles.
I just think its a shame that rather than contact Rally Design who may well have considered the failure as something they wish to delve into and pay
for structural analysis on the failed part, that its been decided to try and destroy the reputation of this part and potentially damage their
business!!! This is a one off failure as far as anyone knows - if someone is so concerned about preventing failure again then why havent they spoken
to Rally Design????
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