51 replies to this topic

[purrlx]

Heath if you are going to run the triangle set up with the ball joint check the rear of a landrover defender 95-05 they run that arm set up with a ball joint.

[purrlx]

Hope this helps

 NTC1773-MC.jpg   34.51K   4 downloads

[Sven]

I like what turbo76lx is doing with a Nissan R32 Skyline. Even for just the rear end.

http://www.gmh-toran...h/?fromsearch=1

I mean, if your going to be welding new mounts in anyway......

[76lxhatch]

The torque arm has to be as long as possible otherwise it behaves more like a single ladder bar, this is an issue with a short vehicle like a Torana plus there's still not a great deal of room for it if you want to retain good ground clearance. Its also a bit more un-sprung weight, although that's probably a minor thing. I went to great lengths to convert to a two piece driveshaft (although mine has a CV centre uni) to solve driveline angle problems, if it were me I'd be keeping it.

The concept of the curved bars over the top of the diff is basically what I meant with the 3 link, it just gains that bit of extra length in the top arm which helps reduce angle changes throughout travel, without too much intrusion into the floor pan. As long as the top arm is at least the same as the factory ones in length (or hopefully a little longer) you're not going backwards and the gain in articulation is well worth it, not to mention vast improvement in roll centre height by using a panhard rod or preferably a watts link with it. Its my understanding that the torsional load on the top arm(s) isn't huge, the bottom arms do most of the location work and the diff isn't big enough round to have a long lever length for applying torque in this manner.

Not sure I see enough gain for the cutting and effort involved to make new triangulated top arms with the centre ball joint, you gain a fair amount of articulation by using rod ends in the standard position top arms. Also the standard suspension is never going to have huge amounts of travel so binding is less of an issue than it seems.

[Bigfella237]

So what advantage is there in having a ball joint on top of the diff over a Heim joint?

 

Both would max-out at about the same angle of articulation I'd reckon, but the ball would be heavier and more complex to mount, strength-wise I think I'd prefer the Heim joint.

 

The other point is, if a Heim joint disintegrates it remains located by it's design (ie. it still has the bolt through the outer ring), if a ball joint comes apart the upper arm is completely detached and the diff starts doing cartwheels under the car.

 

Lower trailing arms mostly take compression load (in the forward direction) when accelerating, whereas the upper arm(s) are being pulled backward by the torque, think of a car wheel-standing when you drop the clutch, it's those poor old upper arms that are lifting all that weight into the air, so don't labour under the misapprehension that they're just there to locate the diff.

[Bigfella237]

Another thing I was thinking about is the problem with fitting coilovers, in that even the shortest ones either need to be mounted well below the axle centre (reducing ground clearance) or have the top mount recessed up through the floor pan. Some people fit them at an angle but that would have to reduce the effectiveness of the shock absorber somewhat?

 

But seeing as this thread is about radical rear suspension, why not take a page from the Formula 1 book and use pushrods and pivots to locate the coilovers elsewhere, they could be mounted transversely above the diff or even rearward into the boot area?

 

This would also make for easier adjustability to ride height (with adjustable length rods) and changes to spring rates (by changing the fulcrum distance on the pivots) without having to swap coil springs. The mounting points would take no more load than they would if the coilover was bolted to them and this setup also reduces unsprung weight and allows you to have the mounting point on the diff as far out toward the wheel as possible.

Edited by Bigfella237, 18 July 2015 - 11:59 AM.

[TerrA LX]

Lower trailing arms mostly take compression load (in the forward direction) when accelerating, whereas the upper arm(s) are being pulled backward by the torque, think of a car wheel-standing when you drop the clutch, it's those poor old upper arms that are lifting all that weight into the air, so don't labour under the misapprehension that they're just there to locate the diff.

 

 

Yeah, its the lower that bends like a banana in the first and second gen Commodore 4 links at the drags.

[Rockoz]

For radical how about IRS?

[Sven]

For radical how about IRS?

Should have mentioned in my previous post, turbo76lx was putting in an IRS Nissan Skyline R32 rear end as part of his build.

[Bigfella237]

What are everyone's thoughts on trailing arm length? Obviously the longer the arm, the less of an arc the diff will travel through (reducing rear steer), but what about upper arm lengths compared to lower arms?

 

Logic says that both upper and lower should be the same length if possible to maintain parallelogram geometry, otherwise they will induce added pinion angle through the range of movement.

 

IIRC Ron Sutton advocates having all arms equal length, but I've read elsewhere people say the uppers should be some percentage of the lowers, like say 70%?

[Heath]

For radical how about IRS?

 

Fair suggestion, and I realise you're not the only one who's made it. I have a few friends who want me to do that and I'm aware of the two box Toranas with it, but the only IRS that I'm aware of that I'd really consider would be like an S14 subframe and even that's too wide for the big staggered dish I want, and a collection of pressed steel arms doesn't really seem period appropriate for the car I'm building.

 

Yes, I'm aware that they can be cut and shut to be skinnier, and I could make tubular arms and so on - nothing is impossible. But there's also a detraction from a legality perspective - it isn't an easily reversible modification and it's the kind of thing you could plausibly be picked up on.

[Redzone]

Here's the Gemini rear end with torque tube.

[Heath]

That is pretty darn short.

[308 Sunbird]

Had to be said Jeff, beat me to it.

[Redzone]

Well it is kinda like a mini torana after all! Lol

[ozyozyozy]

I have set up a 3 link in mine, upper arm goes into the floor were the back seat would have been.
Have an adjustable watts linkage, adjustable centre mounted to body.
Brace the back of my diff. Pretty straight forward really. Made a huge difference to the car.
I have removed it due to wrong spring rates and I don't want to half ass, want to fit quality MCA's or DMS coilover shocks.

[Heath]

Do you have any photos? The more the merrier

[EunUCh]

Is the car going to be used on a track or just "driven" from time to time ?

 

Although off on a bit of a tangent in parallel to another thread!....how much rear steer did they have when the angles of the triangulated four bar system are plugged into CAD or some other program that can calculate such things ?...

 

Going on the brokodoor panhard setup it seems that the driver so i'm told can only notice it when pedaling it reasonably hard in certain corners ?

No doubt there are better systems around that can eliminate some of it but Brock seemed to manage ok in one of them !...unfortunately he never got to race the UC ...which probably would have had a completely different "feel" than the others that he did win races with ?

 

Like oldjohnno said , do some simple measurements to find out how much the live axle moves for and aft in both directions of travel..leave out tire distortion which may or may not affect the the outcome.

 

To experience rear steer and to some extent "torque rear steer"...get on a 750 shaft drive le mans and get it to "snake" at certain road speeds under power in certain cornering conditions...even the chain driven bikes do the same thing ?

 

 

[Heath]

I'll track it a bit but it's a road car. Regardless, it's an engineering exercise.

[ozyozyozy]

Sorry hard for me to post pics on here.
Car is a track/targa car,
Yes you do notice a difference with 3 link, has near zero rear torque steer, a big thing at targa when negotiate high speed bumpy bends can really feel the rear move around it doesn't spit you out just feels bit uneasy.
The 3 link eliminates that, also allows the rear to squat under power, more weight transfer to rear, more traction.