Front straight lower suspension arm failure - can it be prevented?

[Davezj]

well i have been doing some thinking and it has all been about safety which is not like me. I have come up with a possibility.

it will not stop the ball joint failure but engineered right it could stop the joint falling apart. I have been thinking we as club are so lucky that no one has been killed by this style of suspension failure yet, well not that i know of.

in basic terms you weld a nut/bolt to the top of the top wishbone and then bolt the top of a length (correct length) of box section steel to it.
fit a longer bolt to the lower suspension arm where the shock fork attach's and bolt the bottom of the box section length to it.

this should stop the joint breaking apart when the ball joint fails, potentially at high speed.

there will probably be a need for a bit of compliant bushing in the top and bottom fixing holes in the box section, so it does not stop the correct suspension movement. the length of the box section is the critical thing. it should not stop the suspension from moving up and down as the hub carrier fixes the distance from top wishbone to the lower arm anyway.

my theory might fall down if the box section sits on an angle rather than going straight up and down which would change the movement, i think. i will have to have a proper look at the suspension over the weekend to see if it will work or just create triangles effectively and lock the suspension in place and render the suspension useless.

please feel free to comment, especially if you have a "don't be stupid that will never work due to ........." comment.

i have been worrying about suspension failure as you can probably tell.

if you think the link between top wishbone and lower arm can not be solid then a cable of the correct breaking strain could be used instead but this would cost a lot more to impliment.

[The Vee]

I too have been trying to come up with alternatives including using USDM set up which unfortunately is a non starter on our cars as the turret is completely different on the inner wing.
With your idea I can see what you're trying to do and you may even stop the lower arm dropping a little. Unfortunately that's not the biggest issue. When then ball joint shears or pulls out the whole hub and wheel breaks free at the bottom and splays out. This would be unaffected by your mod.

[The Vee]

Another idea I had was if we could turn the lower arm upside down so the ball joint went in from the top. But again , probs with the ball and socket being reversed would require redesign of socket and not enough room between the cv joint and hub. Then redesign hub mounting point by lowering it, but costs, strength etc etc again prohibitive. And then all alignments would alter. For now I think just pulling it apart every year and checking is what, unfortunately we're left with.

[Davezj]

i was hoping that if you stop the bottom arm moving away from the ball of the joint, the ball would go really slack in the hole but it would not pull out of the hole because the box secsion would hold the top of the hub carrier the same distance from the lower arm. stopping it coming apart.
does this not work then?

but it would not help the senario when the actual threaded section of the ball joint shears off the ball bit.

[The Vee]

I can see that part of it but then your basically transferring the weight of the car to the upper arm for which it's not designed. Itwould have to carry weight to stop the ball dropping enough. Not also too sure what would then happen to the "dynamics" of the car, although there are one or two cars that are designed with the shock/spring sitting on the top arm.
Not in any way trying to dishearten you, in fact just the opposite - I would love to find a solution to this that wouldn't cost the earth. It is one of my biggest concerns with the car. Pity it never came to light when the cars were newer as Mitsi would probably have to have had modded it rather than the rather lame recall. It's by no means impossible to cure, just the costs and if it were taken up would there also be design and construction issues.

[Davezj]

Another idea I had was if we could turn the lower arm upside down so the ball joint went in from the top. But again , probs with the ball and socket being reversed would require redesign of socket and not enough room between the cv joint and hub. Then redesign hub mounting point by lowering it, but costs, strength etc etc again prohibitive. And then all alignments would alter. For now I think just pulling it apart every year and checking is what, unfortunately we're left with.

the trouble with inverting a ball joint is the ball gets forced in to the socket and creates extra resistance.

think of the way you undo a ball joint if it spins in the socket when it is the normal way up. you can put a jack under the ball end and apply a bit of pressure which increases the Resistance which in turn allows you to apply more turning force to the nut allowing you to under it.
So when you invert the ball joint are you going to be making the steering heavier, by how much i don't know.

but i get what you are saying, as i spoke to Paul (PSBarham) at donington, we spoke about this very thing.

[The Vee]

[QUOTE=Davezj]the trouble with inverting a ball joint is the ball gets forced in to the socket and creates extra resistance.
QUOTE]


Marginally, perhaps. But this effect is also happenining the other way with the weight of the car pulling the pin onto the shoulders of its socket.
When jacking that other way up one to undo the nut, the resistance is not the ball in the socket. It is pushing the taper fit pin back into it's hole and causing more resistance by the interference fit.

[lancerevo3]

what about some form of clamp that goes around the bottom of the arm and comes up around to both sides of the ball joint [like a fork type ball joint splitter].so when it pops it cant fully come out.but at the same time sitting between hub carrier and ball not clamping it if you get me?

[Davezj]

I can see that part of it but then your basically transferring the weight of the car to the upper arm for which it's not designed. Itwould have to carry weight to stop the ball dropping enough. Not also too sure what would then happen to the "dynamics" of the car, although there are one or two cars that are designed with the shock/spring sitting on the top arm.
Not in any way trying to dishearten you, in fact just the opposite - I would love to find a solution to this that wouldn't cost the earth. It is one of my biggest concerns with the car. Pity it never came to light when the cars were newer as Mitsi would probably have to have modded it rather than the rather lame recall. It's by no means impossible to cure, just the costs and if it were taken up would there also be design and construction issues.

i get what you are saying with this, but isn't that how it is configured already through the hub carrier.

normal configuration:-
the bottom arm is being pushed down always by the spring. the force from the spring is being transfered to the hub carrier via the ball joint, then the hub and out to the wheel forcing it downwards.

in failure with the link box section:-
the spring pushes down the force pulls the link box section down which presses down on the hub carrier, then the hub and out through the wheel.

yes i see the difference now. but hopefully the lower arm will not move by any more than a few milimeters, so the ball doesn't come out of the socket. the upper arm does not normally take any load of the spring at all. It just keeps the top of the hub carrier in the correct place.

[The Vee]

Certainly I see what you're trying to do with the box section idea. Another factor you'd need to consider is the mounting point on the upper arm. The arc drawn by the two arms will be different as they move up and down according to where you fix it.
Is there not some way of fabricating some sort of "catch" system locally to the joint where it attaches to the hub? I did cime up with an idea for this involving a bracket and pin should it drop but it appeared a little cunbersome and not easy to allow for when the steering turned.
Maybe just get the USDM inner wings (or a USDM galant complete)
Your thread does give me renewed interest in this, must be able to sort something!

[scott.mohekey]

What about a length of thick braided wire going between the two parts? I.e. a small plate bolted onto the hub carrier with the ball joint's bolt, and somewhere on the arm?

[Davezj]

my thought for this was started by remebering the staps that are used by monster trucks to stop the shocks from over extending. you might have seen them.
Maybe we could fit a strap under the ball joint a bolt it into the hub carrier some how.

Edit:- simplar idea.

[scott.mohekey]

Ok, a loop of thick braided wire, attached at the ball joint bolt?

[Davezj]

what about some form of clamp that goes around the bottom of the arm and comes up around to both sides of the ball joint [like a fork type ball joint splitter].so when it pops it cant fully come out.but at the same time sitting between hub carrier and ball not clamping it if you get me?

not ignoring you, i had considered this but i couldn't see how it could done at a resonable price, but then how much is life worth.

yes you could put some sort of catch fork/clip under the hub carrier to ball joint connection and round the bottom of the ball joint itself. which would stop the ball as it came out of the socket.

but i don't know how, yet!

i will think about it toworrow and try and get something posted up.

[lancerevo3]

much better idea with the wire instead of fitting suspension to suspension .

[Davezj]

Ok, a loop of thick braided wire, attached at the ball joint bolt?

i see where you are going with this,

a piece of wire rope with and eyelet/loop on each end, one loop goes on ball joint thread, loop wire round the bottom of the lower arm and then second loop goes on to the thread.

looks like it will work but you are not going to be able to make the loop very tight around the lower arm due to the need to put second loop on to the thread as well. if there is just enough wire length to loop the second eyelet on then when it is pushed down the thread to the shaft bit it will start to sag under the bottom of the ball joint.

but it is a good idea and i will work on it.

[scott.mohekey]

Close, but I think it would be better to have a steel washer with a tab under the ball joint bolt, with the wire loop attached to the tab in some way.

[Davezj]

Close, but I think it would be better to have a steel washer with a tab under the ball joint bolt, with the wire loop attached to the tab in some way.

sorry, but i am not getting your description.

[The Vee]

what about some form of clamp that goes around the bottom of the arm and comes up around to both sides of the ball joint [like a fork type ball joint splitter].so when it pops it cant fully come out.but at the same time sitting between hub carrier and ball not clamping it if you get me?

Sorry mate, missed this. Think that is a similar type thing I was thinking with tha catch idea I was on about. Could loop round and locate under the nut of the pin itself. Only thing is it would have to allow the hub to turn (steering) hence the location pin.
Got some old arms here, maybe time for another look

[scott.mohekey]

Excuse my art skills.. but something like this. It doesn't need to be tight, just loose enough to allow all play.