a "cheap" 3 link?

[boss]

i have thought about putting a rear a-frame onto the front of my disco for a while now, I'm just not sure it will work.i am not sure weather the second bolts on the radius arms are for strength or for controle....or a mish mash of both i dont want to start this sort of thing until i know it will be as Strong as the original radius arms.
i have seen people putting the front radius arms onto the rear so i assume that you could put the rear on the front. would this be possible?

[andyb]

i have seen people putting the front radius arms onto the rear so i assume that you could put the rear on the front. would this be possible?

This is often done my comp safari racers for a number of reasons.

1) Commonality of parts....all the radius arms are the same :)
2) The std rear geometry has a roll centre that is higher than the front, doing the 'front on the rear' setup (if done right) makes the front and rear roll centres at the same high giving a horizontal roll axis and this give greater stability at speed thru corners.
3) The rear ball joint and/or mounting can break when given a lot of punishment at speed. When this happens the axle 'flops' forwards and breaks the break pipes/rear prop UJ/shock and/or shock mountings as well.

Your basic idea is sound, but reason 3 above is why all 3-link systems on LRs have been built around very strong gearbox crossmembers (usually custom made for the job) to which the centre link is mounted.

Depending upon how you mount the A-frame you may run into problem also. With the links converging at the axle end I think you will have problems finding room for the mounts at either side of the chassis without conflicting with the exhaust for instance. The other way around and you have all the forces converging at the gearbox crossmember....is previous paragraph :)

You also need to think about vertical separation of the links. For instance 'normal' 3-link systems have the outer links mounted high on the axle casing and the centre link lower than the diff. The upper and lower links should also stay as parallel as possible when viewed from the side. This will minimise diff pinion angle changes when the suspension cycles from droop to compression.

Apologies for all the 'you just swallowed a book' type theory, but it is (I'm afraid) a more complex than you may think. By all means bit it a go, we may well all learn something  :D

[Range Rover Blues]

Not a asmart idea TBH, putting the front end on the rear works, see Disco II, but putting the rear on the front :doh:

Firstly the engine is in the way

Secondly you will get horrendous bunp steer, the panhard rod and front drag link are designed to swing by the same amount as the suspension rises and falls, within limits this works and the steering reacts against the panhard rod, remove it and you will have horrible horrible steering.

All current 3 link front ends retain the panhard rod.

Another issue you will have to deal with is the imense torque generated during braking and acceleration.  The original VELAR had the radius arm mounts at the back higher up on the axle and it caused problems so they were lowered.  The rad arm mounts and the centre ball joint are maybe 6 inches apart, so whatever braking effort the tyres generate is multiplied many times as the loading on the ball joint.  On the front radius arms this will generate a small amount of anti-dive in standard trim.


What you need to do is move the bushes upwards on the front axle and add a 3 link below the axle.  If you want to do it "on the cheap" then use stock rad arms cut just beyond the first bush

[boss]

ah cheers guys, this is why i ask before i act.

[andyb]

Nothing wrong as such with the general geometry of what you propose; take a look at the MitsiMog in this month TOR and look at the front a-frame/uniball setup on that. A hell of a lot more custom built that what you proposed initially, but basically the same layout.