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

[Davezj]

i am of the opinion that if you can protect against both then that would be better.

how about a very simple wire rope ring that can be fixed in place by spliting the ball joint off the hub carrier put the ring onto the hub carrier behind where the nut for the ball joint goes then re fit lower arm to hub carrier and slide the ring back over the end of the lower arm.

the ring wil now be round the hub carrier and lower arm and dropped into place behind the nut.
but then there is the movement issue again.

[lancerevo3]

gona put a hub and arm on a bench and see if anything jumps out at me,or better still if each person does it and see what comes up ?have to be a solution without breaking the bank

[The Vee]

Have rethought that one that I put up earlier. Couple of ideas - will post later tonight as I'm currently at work.

[lancerevo3]

right ,how about a longer bolt that fixes bottom of shock to arm,then attaching a bracket that would sit either side of the arm.from there both sides would meet at a single point resulting in a triangle shape.then a loop/ring attached to top .
now if a braided wire as said earlier was fixed to one side of hub and ran along back of hub where ball joint thread goes through and also through loop/ring of triangle bracket and attached to other side of hub.
NOTE:braided wire could be exchanged for round bar or similar to follow shape of ball joint mounting point.
SORRY IF LONG WINDED JUST TRYING TO DESCRIBE AS BEST I CAN.

[Davezj]

well i have been out today and bought some wire rope and fixing.

i am surprised how low the Safe Working Load is on wire rope. 6mm wire rope 300KG, which does not sound much.
however the breaking load of the same wire rope is about 2 tons.
i do not know how to calculate what the shock load of the ball joint failing, it would have to be some kind of combination of spring rate, and corner weight of the car.

i will try and get some kind of length measurement wire rope will need to be to ensure steering movement is not compromised.

oh i just had a thought, it a ding, light bulb moment.
you can measure the force of a failure if you undo the ball joint nut and move than likely the joint will not split with the use of a ball joint splitter. so if a force gauge is put under the ball joint end when the joint is split from the hub then you will have your answer.
but the cars weight will have to be on the joint as well so the car can not be jacked up while doing this.the gauge would have to be just below the normal resting point of the bottom of the ball joint and to access this the wheel would have to be off. so the gauge would have to on to of some kind of axle stand that can take the weight of the simulated failure.

well the is how i see it anyway. please comment.

oh and if you have any kind of idea as to what could be used as the gauge then that would be good as well. some kind of weighing device with a peek hold on it.

[The Vee]

Don't forget the energy that also has to be stopped should the pin break. Not got round to posting my modified version but will try and get it done later.

[scott.mohekey]

I think that with the wire method, the weakest point will be where the wire is joined/clamped to the fixings.

[Davezj]

if the pin breaks or the ball comes out of the socket, will that not relesae the same amount of energy as the ball joint splitting with the tool. it is just a different method of releasing the energy. I think.

[Davezj]

I think that with the wire method, the weakest point will be where the wire is joined/clamped to the fixings.

yes i agree with that, however there is a methed of joining wire rope into a complet circule without and fixings and the method is as strong as if not stronger than the wire rope on its own. and the wire rope does not actually have to be fixed to anything. unfortuneately it is a time consuming and potentially more expensive mothed. see pic below. you can splice the wire rope together like normal rope.

but how tight the radius can be i don't know, but with this methed the more you pull on it the tight the joint gets.

[The Vee]

if the pin breaks or the ball comes out of the socket, will that not relesae the same amount of energy as the ball joint splitting with the tool. it is just a different method of releasing the energy. I think.

Think of it as holding a hammer in the normal way and have the head on a bench on pushing down on the handle. Then raise the hammer head by just say an inch and then push down with the same force. I Know which one I wouldn't want my finger under! Think it's kinetic energy but it's a long time since I did that

[Davezj]

i am not so sure your analogy is right. but i am stumped as to the measuring device. apart from some very expensive industrial kit i can't think of anything that would do the job.
we could use some kind of corner weight device from a specialist garage but i am not sure they would have a max hold feature on them, plus we need to do this quite cheaply.
does anyone know what the corner weights are on a VR4?

[Davezj]

Think of it as holding a hammer in the normal way and have the head on a bench on pushing down on the handle. Then raise the hammer head by just say an inch and then push down with the same force. I Know which one I wouldn't want my finger under! Think it's kinetic energy but it's a long time since I did that

i have just reread my description of the measuremnet setup and i did not make clear the there would be a gap between the bottom of the ball joint and the measuring gauge. description can be a confusing thing, i have one picture in my mind that i am describing and when you read that description it paints a different picture. I should have done a drawing.
i did not mean,
if a force gauge is put under the ball joint end so it is touching the under side of the ball joint. when the joint is split from the hub then you will have your answer.

So yes i get you hammer analogy now, and agree with you thinking.

[Louis]

(Coming from a rigging background), it is possible to get 4mm diameter wire with a 1ton swl. wires can have crimped loop ends. I have had safety cables made up, when flying/hanging, lighting,PA equipment on trussing.
Some thing similar to F1 cars which would stop the wheel leaving the car, only in our case something that would stop the hub assembly moving out from the car. Poss a steel wire anchored where the straight lower arms inner bush is, and onto the hub?

[lancerevo3]

would the force be greater if you were cornering hard and fast when it pops
as opposed to splitting it yourself?

[fluffnik]

Fortunately so far most have failed at very low speed and the simpler version would probably suffice for these.

Low speed and lots of lock seem to be the common feature of all the failures I've read of. I'm not sure keeping the arm and upright attached but not located would help that much.

Some version of the wire loop idea would be helpful in the typical low speed maneuvering situation though.

It's quite possible that the loadings that cause failure only occur with more lock than you'd ever use at speed, Alpine passes notwithstanding...

[Davezj]

yes the failure point do seem to be low speed manoeuvring which has been lucky up to now.

i had another ding, light on moment last night just before i went to sleep.

it is too difficult to explain properly in words but the basic idea is to have 2 curved metal plate with interlocking lips on them that don't touch in general manoeuvring but if the joint fails then they will lock together and stop separation.

i will draw it up later today but i will have to do a 3d cad model of it and create a 2d drawing from that but i am not sure how to get the drawing into a format everyone can see without downloading some viewing software. the Right Hemisphere 3d model software i mentioned above will not work for stuff i model up at how because i don't have the RH file creation software at home only at work but there is a JT file formate that can be exported and there is free software to download to view the 3d model in that.
i don't have a PDF creator at home either so i can't print to PDF for the 2D drawing, unless so one can point me in the right direction of a freebie PDF creator.

[The Vee]

While I think I know what you mean about the plates, the computer speak uh oh! Still havn't drawn up my modified one but will get round to it, Seen another issue unfortunately in how to fit it withoit having a larger gap at the bottom. All will be revealed when I do my drawing.

[The Vee]

OK here's a drawing of later ideas. If your metal plates with lips / hooks on it is what I think it might be then sounds good - Drawing please even if it's just a few lines like mine!!

/ Damn pc. There's supposed to be 2 diagrams - lost one

[The Vee]

Here it Is!

[The Vee]

Or this? Maybe similar to what you're thinking?