Tesla suspension failure causes, and durability testing?
Tesla suspension failure causes, and durability testing?
(OP)
Though there is a lot of FUD surrounding the company, there is also a lot of anecdotal evidence Teslas experience a high rate of suspension failure without a prior causal impact. Reported failures range from ball joint studs, to control arms, to spindles.
There are also stories of owners signing NDAs following these failures. Teslas also have a much higher fatalities per mile driven than other high-end luxury cars (though most of this could be due to owners using autopilot where they shouldn't).
Hypothesized causes for this include:
1) The use of extruded aluminum for some suspension links, with the links being loaded orthogonal to the extrusion axis.
2) Two-piece ball joints with a stud that seems to be (friction?) welded onto the ball. I'd never seen this before.
3) Hydrogen bubbles in cast aluminum parts.
4) The high mass of the cars (the base Model S weighs 4,647 lbs, with the heaviest X weighing 5,531.
For pictures of various links, head over to ebay.
What I'm wondering is:
A) Do these explanations make sense?
B) If I bought some links off ebay (Tesla does not sell new parts to the public), is there some place I could send them to have them put through some sort of standard automotive testing regimen? I'm guessing this would be tension-compression testing?
C) How often do these parts fail on other cars? My motorsport experience makes me believe these sorts of failures are extremely rare.
Thanks for any help.
Disclosure: I'm short Tesla's stock.
There are also stories of owners signing NDAs following these failures. Teslas also have a much higher fatalities per mile driven than other high-end luxury cars (though most of this could be due to owners using autopilot where they shouldn't).
Hypothesized causes for this include:
1) The use of extruded aluminum for some suspension links, with the links being loaded orthogonal to the extrusion axis.
2) Two-piece ball joints with a stud that seems to be (friction?) welded onto the ball. I'd never seen this before.
3) Hydrogen bubbles in cast aluminum parts.
4) The high mass of the cars (the base Model S weighs 4,647 lbs, with the heaviest X weighing 5,531.
For pictures of various links, head over to ebay.
What I'm wondering is:
A) Do these explanations make sense?
B) If I bought some links off ebay (Tesla does not sell new parts to the public), is there some place I could send them to have them put through some sort of standard automotive testing regimen? I'm guessing this would be tension-compression testing?
C) How often do these parts fail on other cars? My motorsport experience makes me believe these sorts of failures are extremely rare.
Thanks for any help.
Disclosure: I'm short Tesla's stock.
RE: Tesla suspension failure causes, and durability testing?
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Tesla suspension failure causes, and durability testing?
Tesla's suspension design involves lots of joints. Maybe it's better for ride and handling but it does add more failure points.
(B) I would think that the only type of test that would be informative would be a destructive test ... but there's a reason production parts don't get 100% destructive testing
(C) not often but it is not unheard of. Honda cars from the double wishbone era frequently had ball joint failures but almost always after high mileage and many years (I know someone that this happened to). One of the side effects of multilink suspension designs is that the weight of the car passes through at least one of those ball joints. That's not the case with MacPherson (which normally has a ball bearing inside the strut mount with only compressive load on it) Rear suspensions on road cars should not be using ball joints.
RE: Tesla suspension failure causes, and durability testing?
ps: It is highly variable but my control arms, cut and drilled are costing around US$25 per pound. I just send my dxf files to a shop that trucks them out to me next day. (I also have a sculpture garden full of my mistakes!)
RE: Tesla suspension failure causes, and durability testing?
http://corvettestory.com/1963_SAE-paper.php?page=1...
Honda'c choice to do so probably had something to do with packaging a driveshaft in there. Although it looks like there is plenty of clearance to the wheel to keep the balljoint CL where it is, and make the balljoint in compression, and thus more fail-safe.
http://repairguide.autozone.com/znetrgs/repair_gui...
Yes, my daughter's Honda's ball joint separated shortly after a state inspection. Fortunately at very low speed and just a few miles from home.
RE: Tesla suspension failure causes, and durability testing?
Who is telling the truth?
RE: Tesla suspension failure causes, and durability testing?
Brian, those complaints are made by non-owners (likely short sellers). I wouldn't call them fake, but they should be taken with a grain of salt. However there are spats of evidence of failures from Tesla owners, which often seem to quickly be taken down (lending support to the NDA anecdotes). I don't know the truth, which is why I was hoping testing might shed some light on this.
RE: Tesla suspension failure causes, and durability testing?
I am very confident that Tesla did not decide to redesign the ball joint when they needed to buy some. They're not making ball joints in house, they're buying them from a specialist like everyone else does.
Also notice that the linked photo of a failed ball joint stud shows a failure outside the weld. Also notice that whoever commented that 'they know welding and it shouldn't be blue' is wrong, that part looks exactly how I would expect a round friction welded part to look.
With that said- I'm not saying Tesla's suspension components are faulty, and I'm not saying they are not faulty. All this post is meant to convey is that the techniques used to manufacture there parts are not abnormal.
Parts made using industry standard techniques can still fail if they are badly designed, or manufacturing quality is low. One or both of those might be at play here.
RE: Tesla suspension failure causes, and durability testing?
Tesla does a lot of things its own way, with extremely mixed results (they often come first in studies of customer satisfaction, but dead last in reliability). I would not be surprised if they're the only using ball joints like these on passenger cars. They're also very vertically integrated relative to other manufacturers. Though I would be surprised if they were making a part as commoditized as a ball joint in-house, I would not be surprised if they asked a supplier to make them ball joints unlike any others on the market.
RE: Tesla suspension failure causes, and durability testing?
I cannot speak for how the specifications and manufacturing methods for those ball joints were arrived at, how design loads were established, what sort of validation testing was done on them, etc.
RE: Tesla suspension failure causes, and durability testing?
Here's a NYT article of a guy hitting a pothole in his Model S, and having the wheel come off. In order to get it covered under warranty he had to sign an NDA: https://www.nytimes.com/2016/06/11/business/tesla-...
Seems like the only way to arrive at a satisfactory conclusion here would be to study the failures, which I don't have the ability to do. Thanks everyone for the help.