Hello there,

We've been working on our off-road Mogster - running Mog 404 Portals on a bobtailed R-Rover- for the last few months in prep for our first major competition. Got everything all finalised yesterday and took her for a spin and lost the rear Trailing Arm.

Problem wasn’t’ with the trailing arms as much as with the rear ball joint. The ball joint ripped its steel mounting apart (4mil steel plate). The Trailing arm was damaged cause we were trying to get her out of the ‘hills’ without the ball joint being connected. Am trying to get the pics.

Issue is that the torque twists the axle far more than standard. This combined with its articulation meant that the ball joint ripped out. What we need is some way to prevent this twist without limiting our suspension travel too much. Any re-inforcement I can figure will restrict the rear axle’s ability to articulate.

Any thoughts?

Car needs to be good to go in a weeks time so we don't have much time for serious mods ... all advice much appreciated.

Many thanks

A Picture of the issue would prob help a lot ?

Nige

Sorry Nige - Won't get to see te car till this weekend now due to work but have asked the boys if they can get some pics ... Last I hear is that they've put the arm on again with reinforced welding and it held for a quick test but we are worried that any serious tension will cause a break again.

Will post some pics as soon as I can.

Where did it break on and which bit ?

Nige

Ok. Have got some more feedback on the problem.

Problem wasn’t’ with the trailing arms as much as with the rear ball joint. The ball joint ripped its steel mounting apart (4mil steel plate). The Trailing arm was damaged cause we were trying to get her out of the ‘hills’ without the ball joint being connected. Am trying to get the pics.

Issue is that the torque twists the axle far more than standard. This combined with its articulation meant that the ball joint ripped out. What we need is some way to prevent this twist without limiting our suspension travel too much. Any re-inforcement I can figure will restrict the rear axle’s ability to articulate.

Any thoughts?

I'm new to this but one thing I have gathered is that the ball joint on the A frame has a limited amount of articulation. It sounds like you have gone beyond that point so something had to give.

If this were the failure mode then something like this replacement joint may help
http://www.x-eng.co.uk/X-Ball.asp

Steve

You need to take out the springs, and its easier if the wheels are off, and cycle the suspension through all possible movement.
This should tell you if the ball-joint is binding, or if the problem is with the weld.

4mm is a bit skinny, the axle case is really thick, so the welding will need to be top-notch.

4mm ?? for an A frame mount?


eek

8mm minimum for a portal truck, and a whole heap of horsepower to nail it together, the peeling is a product of torque - not the A frame ball joint,

I'm glad I wasnt the only one thinking that! I think even on a standard rangie its thicker than 4mm!
Jon

If time is tight you don't have time to re-think it before an event.

If you can, cut off the crappy brackets you have and weld in something with some beef, or brace the crap out of what you already have. Then, do what Andy suggests - cycle the suspension and see where it binds. At that point (or just before!) you'll need to put bump stops / limit straps to prevent it happening.

Then when you have more time, you can give it all a re-think with better materials and cycle the suspension properly to design the mount.

Good luck, Al.

Thanks Guys!

We've gone up a few notches and got a 15mm Mounting that we are going to Mig Weld on. Hopefully that should hold up. Is there any point in getting a more flaxible ball joint as well like the one suggested - http://www.x-eng.co.uk/X-Ball.asp ?

Cheers!

Vertical separation?
If you have the bottom mounts at bottom of axle and ball joint at the same vetical separation as original, you have approximately doubled the forces. You need to double the vertical separation to retain equal loads.

T

although Tobias is perfectly correct our experience has been that if you use rover rear suspension geometry then the separation isnt a prob even with portals, pay particular attention to the weld, you need high horsepower to sort this - its not in the realms of 160A mig rigs, you simply wont get the penetration and heat you need

If you are using extended travel shocks/springs etc the std joint will bind , causing the peeling off. As Moglite said cycle the susp. with no springs ,just shocks and wheels off, and as Jez says 8mm+ box mount for the ball joint 'pin'. The Xjoint thingy would be worthwhile, and as Al says checkstrap it if theres no time to do the mods.
Have you done a disc conv.?

Cheers

Steveb

HIJACK!

Whats your ideas in front?
Just yesterday finished converting from original radius arms to three link with third link as upper, on left side between frame rail and engine sump.
Vertical separation at axle on 235mm, just under 10".
Vertical separation at frame 0.
Length of upper link about 50mm shirter than lower, which are the radius arms, less the rear bolts.
Axle mount of upper is 20-30mm from panhard bar when at rest, so I was a bit worried of contact during braking, but some severe road tests yesterday show no dents in paintwork of panhard.

Locking up all four on tarmac and hearing the squealing, without carnage, is reassuring

Hope to reduce wheel hop on climbs due to axle wrap through this work, as I had to rotate to reduce UJ angles anyway.

Tobias

If you are running shocks which have less than 14" of travel - a standard ball joint will give sufficient offset to cope - with one big 'if'.

If when the axle has drooped to 50% of its maximum, the taper is still pretty much central within the travel of the joint - i.e. the axle has not rotated to much, then it will have enough travel to cope with full articulation. The taper needs to be perpendicular looking from the side to the flat mounting face of the joint.

Rubbish drawing:
Click to view attachment

This is what mostly causes the ball joint mounting to be torn off.

The solution is simple. Weld it back on using heavier plate. Adjust the lengths of the radius arms such that the joint is in the centre of it's travel with the body jacked up to 50% of it's max height.

If your arms are not adjustable, pack the chassis mount with washers.

Si

sorry but my brains fried at the moment Tobias

did you run it on the 4/3 link calulator? I'd be really interested to see what numbers you hit - ping me a pm? although I might be a little hard to get hold of for a couple of weeks

tak sor!


Si - its more practical with axle swaps to trim the BJ from the outset, tacking and cycling, tacking and cycling, its boring and its grunt work but it pays off big time.

To reduce OT clutter in this thread I have started my own thread on my front three link.
http://forums.lr4x4.com/index.php?showtopic=27102

T