eddie99
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| posted on 24/3/10 at 08:20 AM |
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quote:
Originally posted by Paul TigerB6
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????
+1, and also delete this thread and continue conversation in old one!
http://www.elitemotorsporteng.co.uk/
Twitter: @Elitemotoreng
Facebook: http://www.facebook.com/pages/Elite-Motorsport-Engineering/153409081394323
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ReMan
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| posted on 24/3/10 at 10:03 AM |
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+2
Whatever the rights or wrongs of this it is important enough to keep it in one thread for reference
Fozzie?
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turbodisplay
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| posted on 24/3/10 at 11:00 AM |
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Firstly I`m not looking to affect anyones business, it is because of the dangers involved if it does fail that concerns me. Surely that is what
everyone should be thinking about?
One important point is anodising makes the ali more brittle.
And why would you say it is a servicable item, how many people would buy a tintop where the suspention parts has to be changed (appart from bushes and
ball joints).
RE: One failure in 1000, or 0.1%.
If tap water was poisonous for 0.1% of the time then it would be undrinkable for 86 seconds a day. How many people would accept that?
Darren
[Edited on 24/3/10 by turbodisplay]
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Liam
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| posted on 24/3/10 at 02:22 PM |
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Hmmm what's going on here? Original thread has gone, but this one is reporting 5+ pages which it doesn't actually seem to have??
Hopefully some sort of merger in progress rather than censorship, as this absolutely should not be swept under the carpet. EDIT: All fixed cheers
Chris!
The fact that 'only' 1 of these has failed (which could have easily resulted in a fatal crash) is really a completely separate issue to
whether or not the part is poorly engineered. Even if none had failed, any engineer worth his salt would have serious questions regarding the
material choice for that part, given its dimensions and the details of its application. The fact one has failed merely reinforces the point
made by many that that part in aluminium is simply not fit for purpose!
Thing is there are so many reasons that could be listed for not using aluminium for that part, yet practically none in favour (a possible small cost
saving in machining and saving, say, 20g or so is all I can think of!). So what baffles me is why on earth was ally specified in the first place?
Then we get these attempts to justify it saying it's a 'good' grade of ally, dubious static tensile tests which completely fail to
address the real reason for the failure - fatigue, and redesigns of the already perfectly fit for purpose wishbone to allow the weak unfit for purpose
adjusters to fail relatively safe. All this misses the point that the choice of material was just wrong in the first place, and the obvious solution
to all the many issues created by that choice is simply to make the thing out of steel, which it should have been in the first place!
Liam
[Edited on 24/3/10 by Liam]
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ChrisW
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| posted on 24/3/10 at 02:57 PM |
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We screwed up during the merge and managed to delete the original thread.
I am restoring from backup now.
I'm going to close this thread. Please DO NOT start another. Just be patient, the old one will appear again shortly.
Chris
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ChrisW
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| posted on 24/3/10 at 03:16 PM |
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Ok, now fixed. All discussion in the same place! 
Chris
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boggle
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| posted on 24/3/10 at 03:54 PM |
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materials are not my speciality, but 6082 is not a very soft alloy....it doesnt like being bent
just because you are a character, doesnt mean you have character....
for all your bespoke parts, ali welding, waterjet, laser, folding, turning, milling, composite work, spraying, anodising and cad drawing....
u2u me for details
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Neville Jones
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| posted on 24/3/10 at 05:55 PM |
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Now, I've just had a u2u from RD, basically telling me to pull my head in over certification.
But, a responsible company such as RD, must surely have had these items independantly tested and certificated, before putting them on the market.
Mustn't they???
Obviously not.
Publish the test certificates, if you have had these things independantly tested and certified!!!
No certification, then you pull your head in, and stop telling everyone how good your stuff is, when you don't even know yourselves!! Act
responsibly, and get any critical items independantly checked, to acknowledged standards.
Cheers,
Nev.
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arriba
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| posted on 24/3/10 at 09:59 PM |
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What part on a locost is independently tested?
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Toltec
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| posted on 24/3/10 at 11:29 PM |
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To make this quite clear again.
Just before the adjuster pulled out of the wishbone I had done a a full left to full right lock right hand u-turn without the wheel falling off. It
was only when I reversed with almost full right lock that the wheel pulled free. I tried to see if I could slip the broken adjuster back into the
wishbone by pulling the top of the wheel out far enough. I did this with the wheel pointing forwards and while I could get the wheel far enough out
to place the end of the ball joint thread and adjuster at the end of the wishbone tube the angle between the tube and adjuster would not permit the
parts to slide back together. The head of the adjuster was not on the road where I had turned around or reversed, I spent some time looking for it,
so it had definitely gone before I started to reverse and it came free.
I do not have a car to test this on, however I would surmise that it would be quite difficult to pull the adjuster out over quite a range of wheel
positions. It may even be that reversing with plenty of lock is needed.
The other point to note is that the car has barely done 50 miles so it is not a long term fatigue issue in the sense that cars that have had these
for some time may start to see failures. We do not yet know why this adjuster failed so quickly when other owners have no doubt done thousands of
miles on them.
Perhaps RD needs to see the failed one and even consider checking some with a few miles on for cracks. Now I wonder who might have a X-Ray machine
handy, Ash?
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boggle
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| posted on 25/3/10 at 09:54 AM |
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if the parts are sold for motorsport use only then i dont think they need to be certified...
is there any smal print that says not for road use???
its a great get out clause for people...
just because you are a character, doesnt mean you have character....
for all your bespoke parts, ali welding, waterjet, laser, folding, turning, milling, composite work, spraying, anodising and cad drawing....
u2u me for details
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Neville Jones
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| posted on 25/3/10 at 10:12 AM |
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quote:
Originally posted by arriba
What part on a locost is independently tested?
Now you are getting pedantic. Still doesn't exonnerate you from responsibility.
You're selling parts as 'Fit for Purpose', when, quite obviously, they seem not. You have had no testing done to assure yourselves
or the public, that the parts in question are safe, or 'Fit for Purpose'.
If I was minded to buy some of the parts in question, fit them to a car in the prescribed manner, then have them fail with frightening results, then
send those legal people who advertise on TV after you, well, you'd be bankrupt. Far worse if I were a yank. I am in a position to do it, do you
want to take the risk?
There's a big difference between Joe Bloggs making parts for his car in ignorance, and a reputable company selling parts as Fit for Purpose.
Do yourselves a favour, and the car world, by getting these parts independantly checked by an SAE accredited Chartered Engineer in the least, and
fully tested at best.
Cheers,
Nev.
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arriba
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 posted on 25/3/10 at 12:14 PM |
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Location Matthew Town
Neville Jones....I am intrigued you list your location as Matthew Town...is that the same Matthew Town,listed as the capital of Great Inagua
island,Bahamas?....Wikipedia says that the population of approx 1,000 people on the island largely live in Matthew Town and are employed mainly by the
Morton Salt Company. Must make you something of a celebrity driving a locost around that tiny island?
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Neville Jones
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| posted on 25/3/10 at 02:34 PM |
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On the contrary, a locost gets lost among the pimped up new cars the locals drive. None of them work, so how they get the money is beyond me. They all
seem to have a connection with the local airport, which has the busiest runway between 2.00am and 5.00 am of any in the world, and none of the
incoming or outgoing planes seem to be able to fly higher than about 200ft. Very odd. 
Morton Salt are good payers, as are the Govt over here. Extremely good fishing, and the biggest crays you'll find anywhere. 
And the mosqitoes trained Douglas Bader, are bigger than spitfires, and drown out any plane engine! I've had to have the remains of a few of
their bites removed surgically, true!.
Cheers,
Nev.
[Edited on 25/3/10 by Neville Jones]
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prawnabie
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| posted on 25/3/10 at 06:37 PM |
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Neville always crops up when there is a bullet to fire - well either him or his alter ego syd bridge.
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sebastiaan
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| posted on 30/1/12 at 06:53 PM |
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And another one: Link to WSCC forum
Be careful with these, guys...
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Neville Jones
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| posted on 31/1/12 at 05:17 PM |
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All proved true in good time.
Now wait for the RD ali uprights to start breaking. May be a year or so.......maybe not.
If not made from the proper metal, and propely post treated, the crystallisation will creep up, then bang. I've seen it in other places with
similar material and loads.
Cheers,
Nev.
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paulf
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| posted on 31/1/12 at 10:00 PM |
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That is very poor design, the only way I would use an alloy part in that situation would be if the thread of the suspension joint came right through
the full length , even then the shoulder for the hex adjuster could be a weak point.The wall thickness only looks to be about 3mm minus the thread
depth and even steel would be marginal to use in that layout.
Paul
quote:
Originally posted by sebastiaan
And another one: Link to WSCC forum
Be careful with these, guys...
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flak monkey
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| posted on 1/2/12 at 09:02 PM |
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The ali adjusters work out to have a roughly 1.5 tonne minimum UTS dependant on the alloy they are being made from, could be as high as 2.5 tonne.
Pretty low especially if you crank the lock nut up too hard. Infact you could break them pretty easily just by tightening the nut up with a decent
sized spanner.
Mild steel ones work out at 5.1 tonnes UTS and no fatigue to worry about.
CSA of the adjuster is 117mm^2 (based on 21.75 OD and 18 ID) so equivalent to a 12.2mm solid bar. 430MPa UTS for mild steel.
[Edited on 2/2/12 by flak monkey]
Sera
http://www.motosera.com
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flak monkey
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| posted on 8/2/12 at 09:18 PM |
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Done some more maths one this one. Ok you have to make some assumptions, but it should put some numbers on it.
Assume a loaded and wet weight of 700kg for seven type cars.
The peak tensile load in the adjuster in normal use is during cornering, on the outside tyres. If you assume 70% weight transfer to the outside
wheels, and a 50:50 weight distribution, which I would suggest is fairly typical then the load at the contact patch of the front tyre would be in the
region of 245kg.
On slicks the coefficient of friction could be as high as 1.2, a typical road tyre would normally be a maximum of 0.8 however.
Commonly used g load profiles for road cars is 5-4-3 for durability, so allowing for impact loading beyond normal usage. 5g bump, 4g braking, 3g
lateral. Track cars commonly use 3-2-1 load profiles.
So the horizontal load at the contact patch is in the region of 882kg with this worst case load profile (245kg x 3g x 1.2)
This load acts as a lever on the wheel, essentially applying a torque which is compressing the bottom wishbone and putting the top one under tensile
load. This load has to be carried by the adjuster. I can't see any other situation which applies a significant tensile load to the adjuster.
This is a really rough sketch showing the general layout.
Rolling radius of a typical tyre combo for a seven type car is 225mm. Applying the force at the contact patch, would generate the resultant motion
indicated by the arrows x and y, which would result in a tensile force being applied to the adjuster.
The other vertical line is the upright, the leverage from the wheel is applied at a distance away from the pivot centre of the ball joints (~60mm)
which would be the stub axle in reality. It's a worse case to assume the top and bottom ball joints are only 100mm from the axle centre, I know
this distance is greater, but increasing it would decrease the load on the adjuster anyway. Also ignored is the vertical load on the wheel/tyre, which
would also reduce the force on the adjuster, by providing a moment in the opposite direction, although its much smaller. Again trying to make this a
worse case situation, so this load is being ignored.
So there's some simple leverage going on, some number crunching and the load at the adjuster would be in the region of 2050kg with the load case
above. Increase the distance from the axle to the top balljoint and the load decreases.
That's with a 3g lateral load profile, which you might see in a kerb strike situation, but not under normal driving conditions.
With a steel adjuster that gives you a 2.5x safety factor, including the 3g load profile. Aluminium is more marginal depending on specific alloy and
heat treatment.
Feel free to agree, disagree, or otherwise.
My mild steel adjusters saw 3 kerb strikes in my time of owning the car, and 8000miles. No problems.
[Edited on 8/2/12 by flak monkey]
Sera
http://www.motosera.com
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Neville Jones
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| posted on 9/2/12 at 12:08 PM |
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David, your numbers look about right on quick perusal. Just shows what really is going on. Impact loads could be a factor or two higher.
Unfortunately, most on here aren't engineers and schooled to do the numbers. Not the least of whom are the shopkeepers, and apparently one or
two who call themselves ex or present 'F1 engineers'. Got to ask why the 'ex' though?
Cheers,
Nev.
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Hellfire
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| posted on 9/2/12 at 12:50 PM |
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All you need to do now David, is start your production run of mild steel adjusters, price them competitively and I reckon you could make a few quid
out of them.
Not sure if the math is correct and to be honest, I CBA to check it either but the fact that you've considered the loadings and applied some
numbers to it, gives me more confidence in your mild steel adjusters than the aluminium ones we have fitted at the moment.
Just two questions.......
How would you protect mild steel adjusters from corrosion & how much are you charging for a pair?
Phil
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flak monkey
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| posted on 9/2/12 at 12:54 PM |
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quote:
Originally posted by Neville Jones
David, your numbers look about right on quick perusal. Just shows what really is going on. Impact loads could be a factor or two higher.
Unfortunately, most on here aren't engineers and schooled to do the numbers. Not the least of whom are the shopkeepers, and apparently one or
two who call themselves ex or present 'F1 engineers'. Got to ask why the 'ex' though?
Cheers,
Nev.
Thanks Nev. I really appreciate your input on this.
With respect to the aluminium adjusters. I know people have quoted HE30 material spec for these, but no one has said what the heat treament spec is,
if any. To give you an idea these are the UTS figures for HE30 in various states and the UTS of the adjusters in each material:
HE30 T4 - 205MPa - 2444kg (47% mild steel)
HE30 T5 - 270MPa - 3220kg (62% mild steel)
HE30 T6 - 310MPa - 3697kg (70% mild steel)
But that certainly doesn't take into account any fatigue cycles on the adjuster, and you can see from my previous calculations those high loads
are going to eventually fatigue the adjuster and cause it to break. I can do some theortical fatigue cycle calculations, but its not going to be that
accurate. The thin section just doesn't lend itself to manufacture from most grades of aluminium, even those with similar UTS figures to
steel.
I have tried to make my calcs a worst case to see how much leeway there is until the UTS of a steel adjuster is reached. Based on the calculations and
my road testing with my own car I wouldn't use them made of anything other than steel.
The other significant tensile load on the adjuster is provided by the lock nut. This could easily be in the region of an additional 500-600kg with a
correctly torqued locknut (~15-20lbft). Overtightening it would see this figure increase significantly.
Sera
http://www.motosera.com
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flak monkey
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| posted on 9/2/12 at 01:00 PM |
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quote:
Originally posted by Hellfire
All you need to do now David, is start your production run of mild steel adjusters, price them competitively and I reckon you could make a few quid
out of them.
Not sure if the math is correct and to be honest, I CBA to check it either but the fact that you've considered the loadings and applied some
numbers to it, gives me more confidence in your mild steel adjusters than the aluminium ones we have fitted at the moment.
Just two questions.......
How would you protect mild steel adjusters from corrosion & how much are you charging for a pair?
Phil
Phil,
I fitted mine to the car bare steel, just with a light coat of oil and they never really got that rusty to be honest. But you could just give them a
coat of paint at the hex end to protect them.
I have recently made a few sets and revised the design again, leaving the hex end closed off and the threaded hole drilled to a depth of 50mm. This
still allows the full range of adjustment on the joint, but makes the adjuster solid at the point where you have the stress raiser of the hex meeting
the wishbone tube. This won't afftect the UTS of the adjuster, but its another minor design flaw (in my opinion) adressed.
Sera
http://www.motosera.com
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Neville Jones
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| posted on 9/2/12 at 04:41 PM |
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I've been making these out of EN16, a few lengths of imperial hex I inherited from a local aircraft parts maker. Also been making steering
extensions and other bits out of it. Easily machined as well. I'll be needing some more soon, so have to track some more down.
Cheers,
Nev.
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