One link suspension setup without a panhard rod

[bill van snorkle]

Dan, very O/T,

can i ask what make that stainless toolchest is?

p.s. very nice indeed, i do agree however, the use of a hydraulic ram could make any future "copies" of this work well, as rams are designed to work in dirty gritty environments and has the motions needed along with replacables.

with the added benefit of the use of such ram as a helper in the bump situations, allowing softer springs for increased flexibility for ground contact.

You were doing well Mikey, until the last paragraph !Lol. I fail to see how a ram in that application, even a hydraulically powered ram would have any affect on the springing medium. I was only suggesting the ram (unpowered) as a convenient ready made sliding coupling,

[Bowie69]

You were doing well Mikey, until the last paragraph !Lol. I fail to see how a ram in that application, even a hydraulically powered ram would have any affect on the springing medium. I was only suggesting the ram (unpowered) as a convenient ready made sliding coupling,

You could... part fill with hydraulic oil (for a seal) and gas charge it to a pressure you saw fit, bit like the RRC self-leveller, although of course it wouldn't self-level! or do I have this wrong

Trying to work out the forces through the other axle links -could be huge as it tries to prevent axle rotation.

[dirtydiesel]

Dan, very O/T,

can i ask what make that stainless toolchest is?

p.s. very nice indeed, i do agree however, the use of a hydraulic ram could make any future "copies" of this work well, as rams are designed to work in dirty gritty environments and has the motions needed along with replacables. with the added benefit of the use of such ram as a helper in the bump situations, allowing softer springs for increased flexibility for ground contact.

The toolbox is off ebay, £750ish, reasonably well made about the same as a 5 year old mac box. looks a lot more battered now as it fell over the other day.

I still dont think there is any need to seal the sliding function, but i think you may be onto something with some kind of spung setup.

You were doing well Mikey, until the last paragraph !Lol. I fail to see how a ram in that application, even a hydraulically powered ram would have any affect on the springing medium. I was only suggesting the ram (unpowered) as a convenient ready made sliding coupling,

On the contrary Bill, I think his idea has legs.

Having "bump" sprung much harder than "roll" could be very beneficial.

I had considered a compression spring on the end of the sliding bar, or even between the 1 link and the A frame, this coupled with some really soft springs on my coilovers could make the rear end really work.

[simonr]

I'm inclined to agree with Bill on this one! The rate of change of displacement on the slide increases as the axle droops. Thus as the springs compress, the force required on the slide to push the axle down increases exponentially with the compression of the suspension. However the force delivered by a spring only increases linearly - so it's effect will actually reduce as a proportion of the suspension springs as the suspension compresses, not increase as you would hope - and need for anti-bump.

The way to visualise it is, imagine you have two bars pivoted at one end. The relative lengths of the bars doesn't matter. Arrange the two bars so they are parallel (overlapping). Push one bar and pull the other. The closer the bars are to being parallel, the harder tou need to push to make the pivot end move. When they are parallel, no amount of force will move the pivot.

Si

[Bowie69]

Is an air spring less linear than a steel spring?

[muddy]

You want an accumulator off a front linkage to give suspension with oil in the ram. I have a few if you want to try one.

Will.

[Bowie69]

Now we've done it, Dan will have it all cut off and re-made by this evening... coil overs fitted with cantilevers and a Rover Metro hydrolastic suspension unit fitted in there somehow.

[discomikey]

I'm inclined to agree with Bill on this one! The rate of change of displacement on the slide increases as the axle droops. Thus as the springs compress, the force required on the slide to push the axle down increases exponentially with the compression of the suspension. However the force delivered by a spring only increases linearly - so it's effect will actually reduce as a proportion of the suspension springs as the suspension compresses, not increase as you would hope - and need for anti-bump.

The way to visualise it is, imagine you have two bars pivoted at one end. The relative lengths of the bars doesn't matter. Arrange the two bars so they are parallel (overlapping). Push one bar and pull the other. The closer the bars are to being parallel, the harder tou need to push to make the pivot end move. When they are parallel, no amount of force will move the pivot.

Si

i see what youre saying, i never thought of that untill bill mentioned it.

however the spring type there isnt the problem, it would be the positioning and mechanical advantages that make this idea less viable. wether a hydraulic ram or a coilover strut, it would still experience what you are saying, food for thought though is LR actually did very simislar to this on the 110's and RRC's with that load thingy on the back axle,

The pressures you could put into such an air/hydraulic system would mean it could still overcome the mechanical advantage and still be viable IMHO

[Bowie69]

I saw once, someone had replaced the self-leveller on an RRC chassis with a coil spring, to allow them to run very soft springs at the axle, and get loads of articulation.

[bill van snorkle]

I saw once, someone had replaced the self-leveller on an RRC chassis with a coil spring, to allow them to run very soft springs at the axle, and get loads of articulation.

It has been done quite often. I did that on a hybrid I built for my employer about 11 years ago. Because of the mounting angle of the load leveller relative to the axle, a much stronger spring was required than I originally thought necessary. I ended up with twin opposite wound springs with a combined rate of 400lbs inch.

[Bowie69]

That makes sense, I don't know how they got in with it, but IIRC it was just a stock RRC spring, so doubt, from what you are saying, it would have been stiff enough.

[simonr]

LR actually did very simislar to this on the 110's and RRC's with that load thingy on the back axle,

That's true, but it was for load leveling rather than anti-bump.

Also, because of the mounting points, even when the A frame was horizontal, and the axle on the bump stops, the Boge unit was still angled such that it could deliver a useful downward force.

The setup shown here is different and once you reach a point where the top & bottom links are parallel, no amount of force is going to push the axle down.

The pressures you could put into such an air/hydraulic system would mean it could still overcome the mechanical advantage and still be viable IMHO

You are quite correct that you can deliver high forces - the trouble is, the forces are very high (tending towards infinite as the links approach parallel) and making the rest of the setup strong enough to withstand them may be unfeasible.

Si

[bill van snorkle]

Are those pillow block bearing housings cast iron or steel ? I appreciate that it is not subject to shearing forces unless the sliding shaft jambs due to the surface getting a burr or dent from a rock getting thrown up, but what if that cavity,visible below the bearing in this pic, gets filled with corse gravel ? Would that not inhibit the bearings ability to swivel inside the housing causing it to break if it were cast iron. The reason for asking is that I have broken the odd cast iron pillow block in different applications, and never did get around to enquiring if they were available in steel.

[simonr]

You get Cast Iron, Cast Steel & Forged Steel - in order of toughness (and cost).

Si

[discomikey]

they are available in a pressed steel form

[dirtydiesel]

That one is cast iron Bill, the cavity is open ended and quite small so nothing of a meaningfull size could get wedged in it.

I have looked into a forged stainless one, but if this setup proves effective i'll skip the stainless one to a plan B which will be a custom machined housing with phosphor bronze inserts.

the other thing to consider it that the all up weight of our trialler is 845kg so it probably wouldn't have the weight to break papermache suspension components!!

[bill van snorkle]

Dan,does the bearing give a higher roll centre than the previous panhard rod arrangement ?

" The problem behind the idea is that any suspension system based around a panhard rod can "lock up" in certain circumstances as one wheel is forced to travel in an arc around the other wheel instead of an arc around the roll centre."

The above quote brought back memories from a decade or so ago when building a hybrid RR/LR with 3 link front end and 13.5'' wide 38'' diameter tyres whilst remaining legal with reference to maximum wheel track width increase. The panhard rod gave me some headaches as the increased articulation afforded by the 3 link would cause the right hand side tyre to stuff into the coil spring bucket and upper shock mount, while the left hand tyre had plenty of clearance when stuffed. The illegal solution would have been to fit wheels with greater offset, but then the truck would have failed engineering approval for registration. The solution I ended up with was to replace the panhard rod with a Watts Linkage, which surprisingly didn't transform the truck into an uncontrollable monster due to bump steer from the conflicting geometry between the Watts and the steering draglink.

i'll have to see if I can get another drive of that truck one day, just to refresh my memory on how it handles.

The above does suggest on a RR/Def at least, that the roll centre is not actually the lateral centre of the chassis ?

[dirtydiesel]

Dan,does the bearing give a higher roll centre than the previous panhard rod arrangement ?

It's about 3" higher than before Bill.

As to the panhard rod puzzle.... more experimentation needed!

[dirtydiesel]

Due to clearance on the chassis, i could make use of my short 8" the bilsteins i had without any kind of cantilever.

I weighed the car with my scales the rear is 370kg with 242kg of that being sprung weight, i put this into the foa spring calculator

http://www.f-o-a.com/calculator.html

This gave me a 105lb/in, or 220lb/in and 200lb/in dual springs. i went with dual rate as i could mess with the poundage easier if i needed.

The springs seem pretty perfect.

[bill van snorkle]

Looking good Dan. I don't suppose you run tyre chains on a trailer, so clearance between the side wall of the tyre and the chassis isn't an issue?

[dirtydiesel]

No Bill, studs and chains are prohibited. I might end up hacking the back of the chassis around yet to get a bit more travel and let me run the old wheels that have more backspacing.

the next mods are more likely to be grafting a tdi injection pump onto the ford engine, then hydrosteer, then a re-fab on the front end

[Jamie_grieve]

Looks nicely balanced, how much droop / bump at static ride height? interesting to see how much frame flex there is too for such a light vehicle.

[bill van snorkle]

No Bill, studs and chains are prohibited. I might end up hacking the back of the chassis around yet to get a bit more travel and let me run the old wheels that have more backspacing.

Could you lift the slide bearing on the diff a little higher, so that the tyres articulate up through a wider arc for a little extra clearance?

[dirtydiesel]

Looks nicely balanced, how much droop / bump at static ride height? interesting to see how much frame flex there is too for such a light vehicle.

I haven't really settled on a ride height yet, but the balance is out, i have lots of bump travel in the rear and not a lot up front,

There is no frame flex at all, its a box chassis with a multipoint cage tied into it.

[Bowie69]

How much does it weigh in all?

Is that REALLY a jimny?