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Mk indy front lower nearside wishbone
jerker84 - 15/5/19 at 08:56 AM

Hi, has anyone got a spare mk indy front lower nearside wishbone?

Mine decided to break so I need a replacement.

Cheers Pete

Bluemoon - 15/5/19 at 09:08 AM

quote:
Originally posted by jerker84
Hi, has anyone got a spare mk indy front lower nearside wishbone?

Mine decided to break so I need a replacement.

Cheers Pete


Still avalible from MK https://www.mksportscars.com/

G13BLocost - 15/5/19 at 09:18 AM

Just being nosey: where did it break? Any pictures?

pewe - 15/5/19 at 10:15 AM

quote:
Originally posted by G13BLocost
Just being nosey: where did it break? Any pictures?


I'd be interested to know that as well.
No1 adult son walked away from a potentially serious accident when the front lower wishbone on a Westfield snapped under braking at Combe a couple of years ago.
It looked as if the thin wall tubing used had rusted inside where they had welded a strengthener right where the ball-joint picks up.
I felt justified using thick wall tubing for the lower wishbones when I built the F27.
Cheers, Pewe10

jerker84 - 15/5/19 at 12:37 PM

Here you go. I will definitely be strengthened the new one before it goes on.




I was hoping someone had some knocking around to save me paying full price

Does anyone know if the Haynes roadster ones fit? They seem to be alot cheaper.

Cheers Pete

rusty nuts - 15/5/19 at 12:51 PM

Think it might be a good idea to check all the other wishbones, that failure is in the heat affected zone but it could have been caused by the bushes/crush tubes being too tight? The wishbones should be able to rotate around the crush tubes freely with no binding

pewe - 15/5/19 at 01:52 PM

That looks unbelievably weak to me.
Even the hairdressers has webs around the outsides to strengthen or am I missing something?

theconrodkid - 15/5/19 at 02:41 PM

that looks like the round tube has split where the erw tube was welded at the factory, if using erw, the join is suposed to be next to the actual bone so it wont come unwelded, someone else had a the same happen to his

Bluemoon - 15/5/19 at 04:25 PM

Should do a search it’s not the first time that’s happened. It seems to be due to steel crush tube rusting causing bush to seize. Poly bush should rotate freely on crush tube. If not it fatigues the eye near the welds HAZ leading to failure. In practice with only wishbone attached to chassis it should drop under own weight. Crush tube should be about 0.5mm longer than the poly bush once installed in wishbown eye.

With the steel crush tubes it’s a good idea to remove inspect and lubricant them maybe yearly to ensure they can’t seize. I would suspect the other bones might also be fatigued.. I am considering replacing the crush tube with stainless ones and adding a grease nipple..

Dan

spiyda - 15/5/19 at 11:19 PM

Soon get that welded up, and add some extra strength at the same time.
we can use the same bit of tube and wrap it round a bit of steel turned down as a former,
grind off the old weld and replace it with a new one
If I can weld driveshafts without them breaking, I should be able to weld a bit of tube together !
If there is space we can grind off the excess, wrap a bit of steel right round the tube and weld it to the oval secition
Getting the whole section hot is also important, to relieve heat stress.

Bluemoon - 16/5/19 at 10:08 AM

quote:
Originally posted by spiyda
Soon get that welded up, and add some extra strength at the same time.
we can use the same bit of tube and wrap it round a bit of steel turned down as a former,
grind off the old weld and replace it with a new one
If I can weld driveshafts without them breaking, I should be able to weld a bit of tube together !
If there is space we can grind off the excess, wrap a bit of steel right round the tube and weld it to the oval secition
Getting the whole section hot is also important, to relieve heat stress.


Not sure this is the correct approach. Why is it failing? Like the above when seen before this though to be due to seizing of bush/and or incorrectly fitted crush tube (to short). Fatigue cracking depends on the number of cycles, the other bones may also be affected how many stress cycles are left before they also fail...

If you beef it up but the bush is still seizing it will still fail as the bone is loaded in bending. The real solution is to ensure free movement of the suspension.


Dan

spiyda - 16/5/19 at 10:43 AM

quote:
Originally posted by Bluemoon
quote:
Originally posted by spiyda
Soon get that welded up, and add some extra strength at the same time.
we can use the same bit of tube and wrap it round a bit of steel turned down as a former,
grind off the old weld and replace it with a new one
If I can weld driveshafts without them breaking, I should be able to weld a bit of tube together !
If there is space we can grind off the excess, wrap a bit of steel right round the tube and weld it to the oval secition
Getting the whole section hot is also important, to relieve heat stress.


Not sure this is the correct approach. Why is it failing? Like the above when seen before this though to be due to seizing of bush/and or incorrectly fitted crush tube (to short). Fatigue cracking depends on the number of cycles, the other bones may also be affected how many stress cycles are left before they also fail...

If you beef it up but the bush is still seizing it will still fail as the bone is loaded in bending. The real solution is to ensure free movement of the suspension.


Dan


When the car arrived ( second hand) The rear suspension was dismantled and the bushes reamed to get a nice fit,
but the fronts fell under their own weight so were left alone
after repair we will ream the front bushes if necccesary

Bluemoon - 16/5/19 at 02:10 PM

quote:


When the car arrived ( second hand) The rear suspension was dismantled and the bushes reamed to get a nice fit,
but the fronts fell under their own weight so were left alone
after repair we will ream the front bushes if necccesary



Would be good to understand a little more.

What mileage has been done on the bones?

Do you have a photo of the bush/crush tube on the chassis?

How long ago were the front bushes checked and working well (the bone dropping on its own weight (i.e. without upright/wheel/shock etc)?

The bushes to rust up particularly if used in the wet, is this a contributing factor or not?

Where the bushes creaking or silent before the issue?



Regards

Dan

jerker84 - 5/6/19 at 12:49 PM

The car had done 6000+ miles and there was some rust, but nothing too worrying. There was no creaking from the front but there was some from the back before we rebuilt it.

In the end we rewelded the broken wishbone and strengthened both sides.

spiyda - 5/6/19 at 02:13 PM

Just to add to that,
the crush tubes were pitted but not too rusty,
they were reasonable free in the bushes, spushed out wth finger pressure..
when they went back they were lubricated with dielectric grease..

The welds however were not full penetation and the colour change visible under the paint
showed that they were not pre-heated and that the heat did not spread fron the weld into the tube.

The new welds showed a coulur change for at least 10mm from the weld line.