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Design of a panhard rod/bar


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MogLite has a semi-trangulated 4-link front suspension.

I've used standard Land Rover bushes for cost/service/ease of build.

Alas when steered stationary on firm hard ground, the body moves quite a bit before the axle starts steering. Just like a Landie with knackered panhard rod bushes.

I don't know if this is going to be a real big problem, or just something to refine/improve upon.

A panhard bar fixes this I believe. Harder poly-bushes might help too, but lets assume panhard for this thread.

I've got the standard LR panhard bar mounts on the Disco 4-bolt steering box. So I guess I'll start with a LR Panhard bar to give me the fixings for that end at least.

I'll have to weld mountings to the axle for the other end.

Should I use a LR bush at that end, or would a rose-joint or similar be a better bet ?

Does it need to be adjustable ?

I'm assuming I'll set the lengths/mounts so the bar is horizontal at ride height - is there a better option ?

Lastly - how strong does it need to be ? I've got a whole bunch of blue-band gas pipe, ~25mm OD 2.6mm wall. Would this do it ?

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Andy, only suggestions but I would go for;

Landy bushed for commonality

bushed both ends - rose joint is irrelevant with porky axles

solid bar

no need for adjustable unless you are planning on fitting a scrapiron sag lift kit? :lol:

as horizontal as practical

As strong as you can get :)

make a Jig - so you can make a few more as and when needed :)

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Nick (RogueVogue) used a Steering link from a Bedford lorry for the panhard rod on the back of the rogue vogue. I think there should be some pictures of the setup somwhere on this forum, but it certainly looks up to the job.

Not sure of bushes or any of the details really, but it might be worth an ask, or at lesat a search for the pictures...

Mark

found it: Pictures of Nick's rear setup

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Andy, if you've already partly-triangulated the suspension you have (IIRC you've got bars in the shape of an A-frame, but bushed) then this will ask the rear axle to travel vertically. A panhard rod will want the axle to describe a circle around one (driver's side?) chassis rail, so the two will fight each other and either destroy the bushes in short order or become excessively stiff. In fact, without any compliance in the bushes at all the centre of the axle would travel vertically, the passenger-side panhard mount would move in a circle around the chassis mount and overall you'd get a roll component as the whole thing moved vertically.

This might not amount to much if you've got flexy bushes and the panhard rod is nearly horizontal but they'll certainly be fighting each other in situations like this (credit to Rogue):

Bures017Medium.jpg

Hard to say how significant this'll be without trying it but it's not the most elegant solution.

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Andy,

I would look at the bushes before you look at anything else.

Just adding a panard rod to you system will result in zero axle travel.

Looking at your setup on your website i suspect the problem lies with the chassis end if you upper triangulated links you are going to have to do a refab and use the same bushes at the chassis as the axle.

You can get very good lateral axle location on triangulated 4 link,

When i built one i managed to get the lateral chassis to axle movement down to 4mm, the standard rangy i measured at the time had 6mm of movement.

And i was using much bigger bushes (i.e. more flex) so you sould be able to get yours down to practically nothing.

Although if you stiffen the upper triangulated links up you may well find that under steering loads the triangulated links will stay still and the lower links will respectively compress and extend on their bushes allowing the axle to "walk".

Stick with it :) working right 4 link is very good.

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For what it's worth, Andy's problem stems form packing issues with 404 portals (with their rather large pinions) plus a four-link; plus prop-shafts; plus steering links - there really isn't much room to play with stuff (ask me how I know...)

Andy, I'd confidently state that the small diameter stuff in my garage just isn't up to the task... Listen to Jez and go with solid bar.

5 links are by definition overconstrained. Don't worry too much about that, just get it going with a panhard - you can always add a disconnect for extreme articulation stuff. Overconstrained does not mean "zero azle travel" - you can still get decent performance from a 5-link. But I agree with DD's suggestion - look at the flexi-rubber carp in your system first.

Whether or not you can get "good lateral axle location" on a tri-4-link is immaterial if you have no choice on where to put the link mounts... :(

Try to make the panhard as long as possible, and as close to horizontal as poss under normal load conditions.

Al.

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5 links are by definition overconstrained. Don't worry too much about that, just get it going with a panhard - you can always add a disconnect for extreme articulation stuff. Overconstrained does not mean "zero azle travel" - you can still get decent performance from a 5-link.

Andy is already running a lot if triangulation on his top arms, if he were to add a panard rod it would have to be totally flat so as to be in the centre of it's arc, but even then you only get droop, i have already tried this route and i got practically no roll at all.

A true 5 link runs the upper and lower arms as close to parallel as possible, at this you can get very good movement with very positive location.

As for packaging the mogs, it's all down to how hard you try :).

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You did say triangulated 4 link''front suspension''? Had you previously thought about the possible bump steer implications of the conflicting geometry between the steering draglink and the suspension links? The effect is theoretically significant, although on a 3 link plus Watts link hybrid I once built it was manageable as long as the driver allowed the steering wheel to move a little on bumps.

Bill.

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I had hoped to get MogLite out of the garage at the weekend, so I could see where the problem is, and how bad it is.

Alas I ran out of energy/time.

I really don't want a panhard. It seems it will knacker my suspension travel, which I don't want to do.

I'll experiment with some different bushes, chassis end of the inner links is favourite for some poly style bushes at the moment.

Bumpsteer - nah haven't thought about that. Its gonna be a trailer queen ;)

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I had hoped to get MogLite out of the garage at the weekend, so I could see where the problem is, and how bad it is.

Alas I ran out of energy/time.

I really don't want a panhard. It seems it will knacker my suspension travel, which I don't want to do.

I'll experiment with some different bushes, chassis end of the inner links is favourite for some poly style bushes at the moment.

Bumpsteer - nah haven't thought about that. Its gonna be a trailer queen ;)

Hi Andy,

The trouble with using rubber bushes on each end of the four links is that it will be impossible to eliminate the symptoms you describe, as even if you only have a little movement fore and aft, it is magnified by there being 8 bushes. It is the 'fore and aft' give within the bushes which is contributing most to the problem. You would improve it if you were to fit rod eye bearings or similar, even with half of the bushes replaced would see an improvement. Polybushes may be the cheapest 'quick fix'

The other issue as pointed out by Bill is that a 4 link is best suited to full hydro steering. If you keep the stock power steering with drag link, you will get bump steer which may be sudden and very unwanted even at low speed. It may cause the steering wheel to be wrenched out of your hand in an 'extreme moment'.

If you want to keep with cheap bushings, and keep the conventional power steering with a drag link. You would be better off with a 3 link and a panhard rod in my opinion.

Regards,

Diff

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