cabrio anti roll bar mount

[dogoncrazy]

While investigating an unusual noise from front nearside of my Cabrio I found that the mounting for the anti roll bar on the chassis rail to be poorly welded. The mounting is moving fractionally and emitting a loud 'click' under braking or if you move car in reverse.
This is my second incident with poor welding by Marlin, the first being an engine mounting that started to split open along a welded seam. That was also on nearside so wondering if there is a theme here! Looks like my plans for New Years Day at Stoney Stratford are scuppered.
Fellow owners, you may wish to check the integrity of yours!
Merry Christmas everyone.

[greyV8pete]

Re: cabrio anti roll bar mount

That's a bit worrying. Any chance of a photo to clarify the exact location? I guess you mean the weld join between the rectangular plate and the main chassis rail?

[dogoncrazy]

Re: cabrio anti roll bar mount

Correct on the rectangular plate/ chassis rail. Will try to post photo when camera is up and running.

[peterboat]

Re: cabrio anti roll bar mount

Well earlier this year my hunter had a very bad crash on the offside, it all but ripped the suspension off the anti roll bar mount was bent down by at least 1 cm, and the anti roll bar was badly distorted, nothing was reusable on that side. When i was checking things over after heating the mount up and straightening it I noted no damage to any welds but the two mounts wernt in line clearly a design error.
The issue i think is maybe a new guy was doing the welding on dogoncrazy's car, fingers crossed that it isnt all of them.

[dogoncrazy]

Re: cabrio anti roll bar mount

Hopefully photos here.

[peterboat]

Re: cabrio anti roll bar mount

It looks like the steel has rotted rather than a poor weld from the pictures

[dogoncrazy]

Re: cabrio anti roll bar mount

If you look at the fracture [what you can see of it] the metal still appears to be quite bright suggesting that it hasn't been exposed to the elements for any length of time. This doesn't look to me like the steel having rotted away, more a case of poor weld penetration which was the cause of the previous engine mount failure.
Further investigation today [What else do you do at Christmas!] led to potentially another factor in the equation. The anti roll bar was reluctant to revolve in the poly mount which I felt to be incorrect. I wonder if this accelerated the problem as torsional stresses would then be transferred to the mounting and in turn to the attachment to the chassis.
What do you boffins think?
The offside does not seem to have the same problem thankfully.

[Mike]

Re: cabrio anti roll bar mount

It looks like the steel has rotted rather than a poor weld from the pictures

On the basis that the mounting block was welded to a solid chassis member, I would suggest this is due to "burn through" - too much heat - rather than poor penetration.

If it was the latter would there not be chassis material left showing when the weld failed?

[dogoncrazy]

Re: cabrio anti roll bar mount

Thanks Mike, that kind of makes sense I think.
I'm hoping that David Billings [Doug and Liz's son] can help as he's done my previous welding. I admit I know b------- al about welding, I leave that to people who do.
Hope you had a Good Christmas

[greyV8pete]

Re: cabrio anti roll bar mount

If the fracture is bright and intecrystalline I would be thinking of stress corrosion along the edge of the heat affected zone. Maybe incorrect filler wire too???

[dogoncrazy]

Re: cabrio anti roll bar mount

Repairs now completed. Many thanks to David Billings who added reinforcement plates both sides. It would appear that by chopping out the centre of the anti roll bar by marlin to clear the BMW's sump has produced undue torsional stresses on the mountings that would not exist in normal configuration.
All that now required is to repaint and look forward to more Marlin motoring .
Top Man David!!!

[dcunn]

Re: cabrio anti roll bar mount

Good news - C U soon then

[Mike]

Re: cabrio anti roll bar mount

Repairs now completed. Many thanks to David Billings who added reinforcement plates both sides. It would appear that by chopping out the centre of the anti roll bar by marlin to clear the BMW's sump has produced undue torsional stresses on the mountings that would not exist in normal configuration.
All that now required is to repaint and look forward to more Marlin motoring .
Top Man David!!!

Hi Alan

Happy New Year

Glad to hear you have solved your ARB chassis mounting problem.

It sounds like Marlin did the same to my original ARB - chopped the middle out of it: I refused to fit it!




There are different shaped ARBs, as well as variations in diameter: I found one from a P100 Sierra pick up cleared my sump - you can see below the centre crank section is quit different from a more standard ARB - and it was the smallest diameter which gives a softer ride.
Is your sump at the front, or back of your engine? If it is at the front you could change it for a rear sump and then fit the P100 style ARB.
I have one you could try out if you are interested?




All the best for 2017

Mike

[greyV8pete]

Re: cabrio anti roll bar mount

Repairs now completed. Many thanks to David Billings who added reinforcement plates both sides. It would appear that by chopping out the centre of the anti roll bar by marlin to clear the BMW's sump has produced undue torsional stresses on the mountings that would not exist in normal configuration.
All that now required is to repaint and look forward to more Marlin motoring .
Top Man David!!!

So would fitting compression struts not similarly load the mounting plates more than the original ARB set up? Just a thought. Peter.

[dogoncrazy]

Re: cabrio anti roll bar mount

Looking at the kit from Burton Power I would say not. I'm thinking that as the mounting bracket is angled and the tension strut has the ability to pivot at a point just aft of the TCA as well as the rose joint then all should be OK . However I'm not a suspension engineer so my take on it may not hold water!