Not a new idea by any means - but I can't see any reason it will not perform every bit as well as 3 link off road:

First hack off the end of one of your hockey sticks. Then make up some solid bushes for the other hockey stick:

Then mount remaining bit of hockey stick as normal:

and


Then try jacking up one side of the vehicle. Before this mod, the front would stop articulating with about 2" of extension left in the shocks (which are +2" with lowered turrets). Now, the shock is the only limiting factor. With the shock removed, the HiLift was the limiting factor.


Although this does not really show how it will articulate in the field, it does show that the front & rear are balanced up to that angle. There is 3" more shock travel on the back so it will go a bit further.

What is the reason for the solid (Nylon) bushes?
When you accelerate or brake, the axle tries to rotate. The only thing stopping it rotating is normally the four hockey stick bushes. Since I have removed the effect of two of them, the remaining two need to be stiffer to result in the same roll.

The single remaining bush in the modified arm is a medium polybush.

Why doesn't everyone do this? Because it adds asymetry to your steering. Cornering left, the castor angle is increased and cornering right, it is reduced. The steering appears to self center OK on the road (with a little extra toe-in). It does roll some if you try cornering fast though - but this would be true of 3 link as well.

I'll be at Slindon on Sunday to try it out in anger! I have high hopes. Think I might have to have a look at detachable anti-roll bars now to make it a bit more civilised to drive on the road at any speed.

Si

Si

Very Very interesting (in a sort of slightly frighening sort of way ) seems like your definately onto something here, I know front suspension thoughts have been rattling around in your mind for quite some time...

Look forward to report and pics

Nige

Well it's one simple way to stop the front bushes binding. Good luck with the field trials.

I'll certainly work
What plod/insurance/MOT would say is anybodies guess as its obvious a key part of your suspension is missing
You'll be needing an SVA

I'd be more tempted to try a "wristed arm"

Common in the Bronco world



the red thing is a pin to lock it out on the road.

Good luck on road!

Keep us posted...

i think he's gonna need it

interesting though

could you not put swivels where the bush is at the chassis end, same effect, less twist though i would assume

Then you may want this



but it's always a compromise,and there's a thread on the P44 BB in which Sam (Strangerover)
suggests not to use it on his own experience...

I never tried one so I can't really say.

I'm very interested in how this turns out Si.

I've been looking at ways to increse front droop, - currently on Gwyn Lewis/Llama 4x4 raised turrets with long dampers and worn metalastic bushes in narrow front arms. I had been considering void bushes/drilled polybushes but was concerned by the alarming wear rate and tendency to twist under torque.

Could probably (if i can find them) bring some narrow radius arms to Sodbury if that helps?


Lewis

can you post up the link ?

and why not use a locking one then ?

Nige

Hey Nige!

That's lockable (pin-n-able?),you get out of the truck > un-pin > wheel > get out again > pin

(uhm)

I may have saved the link in my favs,I'll search...!
In the meanwhile check the original page out:
hinged radius arm by Quinn D.
(you may already know it,it's a bit dated)

Simon,

I have thought about this one, and tried it by removing one bolt. The problem is under braking: you removed the antidive on one side. So this will result in some weird results while braking hard. I would certainly consider the solution for a trailered vehicle, but if it were to be used on the road, not so sure. The hinged version as shown does give you better results I think.

Daan

What I've built is a first step towards this:


I wanted to make sure the idea worked before embarking on a load more fabrication.

One of the issues with the pin-lockable one above is the centre of rotation of the axle being further away from the axle itself. Ideally it would be on the center line of the axle but the further away you go the more of a steerage component is added as it articulates. This just increases the asymetry and makes the steering feel even more 'funny'.

Si

Sam from Outer limits
Builder of MOGROVER
tried the wristed arm and binned it
http://www.outerlimits4x4.com/viewtopic.php?t=7718

Simon, have a word with Filthy Boy; he ran a hinged radius arm on his 90 for quite a while. In fact I think he stated with a bought in one then went on to make his own.

I looked at doing this fairly seriously and, although it is a very simple bolt on mod, there seemed to be some major handling issues. The problem seemed to be axle rap on the hinged side when climbing, or decending, steep hills: not the time you want an unpredictable vehicle. I think you're solid bushes should help, as should pushing the centre of rotation further towards the axle, however I still think there may be some scarey handling issues.

See, that's the trouble. Lots of people have an opinion about this idea (mostly that it's rubbish) but there are very few who have tried it themselves.



The handling of most off-roaders is 'interesting' to start with! The 'Axle rap' (is that a made up expression?) should only directly affect castor angle. As it rotates, admittedly you will get a small steerage component but I doubt that will be noticable.

I did wonder about the roll of the axle trying to rotate the standard hockey stick which in turn will translate into forcing body roll. This might cause a problem if you are on the brink of tipping over - but then so might the torque roll caused by your prop shafts both turning the same way on a car without this?


Apart from the extreme body roll - it doesn't feel that different on the road. We'll see if I die on the way to Slindon though!

Si

Last year i snapped a radius arm between the bushes....

But did not realise and continued to drive the vehicle on road and offroad for about a week, cos i diddn't have time to check what was wrong.......

Offroad awesome..

The vehicle stayed level and felt very positive.

On road it would dive under braking and felt very........errrrrrr Dodgy..

I have also driven a professional built hinging arm and also vehicles with three link.......

Result...Well, fine offorad but and on road if you are preppared to except that the handling is not going to be as good as standard.

The ultimate front suspension...?? I really don't know, but i do know that it needs more of us pushing the boubndarys and trying to find it..

Crack on Simon Looking good

Jim

Haha, its sort of made up; it should read wrap. The spelling thing again

Yes, your setup should help the handling given that the pivot is as close to the centre of the axle as possible. A little while ago I did some drawings for a setup which would've gone further but would have been very difficult to make. The basic idea was that a smooth collar would be welded to the axle tube in place of one of the radius arm mounts. The radius arm mount would be a 2 peice cylinder that would fit over the colar and bolt together. This would move the pivot to the centre of the axle tube. PITA to make but it could work.

My latest idea is to do something along the lines of the Dobsons X-link. Its a really, really nice idea that would allow you to use standard radius arms and chassis mounts although the axle casing needs a fair bit of work. I'm not even going to try and explain it because its quite difficult to but, if you look at a picture, you soon see how it works. Because its a system that can be totally locked out it gives the best of both worlds: good (well for an even vehicle) on road handling and superb articulation when you remove a pin.

Oh, and Jim's right. This is an area not many people have looked at and I think there are some interesting possibilities.

Not saying your idea is rubbish, cause it does work for more articulation. Keep it coming!

The bodyroll issue under acceleration can be affected in a positive way, in that if you fit the standard radius arm to the left, it will counteract against bodyroll caused by the props. This depends on the diffratios, in my case with 4.75 diffs, the torque from te props is much less than it would be with 3.54 diffs and On my vehicle, I hardly notice influence due to this. The bodyroll under braking is harder to fix.

How much suspension travel are you running? In my case, I run 10 inch shocks and on full stuff, the axles actually do hit the stops, So I am not concerned about more travel.

I fitted radius arms to the rear as well, and although my suspension travel is not anywhere near as much as some people out there, the fact that it is well balanced, it has been very effective off road and on the road.

Daan

Daan, you are quite right. The hinged arm should be on the right (drivers) side. The lean generated by prop shaft torque combined with axle roll is quite pronounced.

I've done a bit of road testing today - 30 miles worth - and once you learn how it behaves, it's not too bad.

I have come to an unusual conclusion though. I think what it needs is roll-damping. After all, you rarely if ever need the articulation to happen fast. On the road, it tends to be sudden changes which cause problems as you cannot react fast enough.

Something like this to start with:

I'll mount it across the hinge so the damper moves as the hinge flexes.

It's just a regular ram filled with ATF with rate adjusters on either end - so you can control the compression & rebound separately. Made as a steering damper for the electric bar stool. May turn out not to be strong enough - but will prove the concept.

I mighe even be able to adjust it so the hinged arm exactly cancels torque roll (as per Daan's post).

I think the combination of these might make it a lot more civilised.

Si

will this pinned arm arangement work aswell as a 3-link? would you leave the nearside arm alone or still cut one bolt lug off??

would be a great cheap mod.

I can see the roll damping working; its more common on track racing.
I also remember you having quite soft springs. It might be a case of going slightly stiffer, which you can afford with this setup and is mazbe needed for side slopes. But Double shocks could be more effective, If you have not done so already.

Keep us posted!

Daan

As Will said I ran a hinged arm. First a bought one and then redesigned and fabricated to improve a number of things.

For mucking around on playdays, driving down flat boulder filled rivers and, most importantly, parking on big ramps at shows, it is a bolt on way to get loads more front end articulation. I have some great pics to illustrate this and liked it for some time.

The unpinned handling on road you can just get used to but tight windy mountain roads on the Cevenol were interesting!

The real problem, and why I gave up with it, is when you get the front end up a big step and try to accelerate to bring up the rear (ie unweighted front end) it torque steers like mad to the unhinged side. Scary when climbing steps with a big drop / cliff on 1 side! Same whatever you put the hinge.

So there you go, the opinion of a man who did it. Not too bad if you stay on the flat.

FB

PS When redesigning the arm we did a FEA of the standard arm. It is a great piece of design. The fabricated I beam from plate type is nowhere near as good strength wide. We machined from solid billet steel of some stupidly expensive and strong type.

hows about a ram to act as a lockout? put a line lock in for launching and leave it open for twist......... or a flow control valve to act as a damper (that would slow the systems reaction time)

just random ramblings.. I need more coffee

Brilliant - real world feedback

Thanks.

All the rams and hydraulic locks won't remove the torque steer.

FB

was wondering if a ram could be used as a lazy way to lock the system up therefore returning it to a stock setup - clevis and ram in a digger boom stylee, like I said more coffee required

Good to get experienced feedback on the setup though - cheers

That's pretty much what I had in mind with the ram I've got.

It wont remove torque steer off road, but a damper will slow it down, hopefully to the point you can react to it. Likewise with the torque lean generated.

Locking the ram would return the geometry to near standard - so you could have it normally locked with a 'super articulation' button on the top of your gearstick to give you the articulation if you need it?

Another idea, I think closer to what Jez suggested is having a locking sleeve which slides along the radius arm and captures a plate on either side of the axle mount to lock it off. The sleeve can be moved using a handbrake cable connected to another lever in the cab.

Tell you what, with the hydraulic ram to lock it in one position, if you wanted to lean the vehicle one way or another, you stick it in drive or reverse with the brakes on then lock the ram. it will then hold that lean. Might be useful for moving your punch card a couple of inches closer to the punch!

So many possibilities!

Si

I think the ram with flow control would give you what you want Si - wack the damping up for "driveable but twisty" and lock it for "normal use" or leave it open for "twist like hell"??

I like it!

But what about an air operated ram instead of hydraulic?
Less hassle for those who have OBA?

Just a thought...

air is compressible - it wouldnt so much lock out - more sort of just bouncy it out

the hydro circuit would need any kind of pump, just a closed circuit with flow control element to it

Whoups!

My coat,thanks...

You could use an air solenoid to lock it with a sliding pin etc

Just a thought


Lewis

seems complicated because it can be!

can't see scrapiron pinching that one........yet!

whats wrong with mounting a 3 link with the middle link coming off the top of the diff an on to a bracket off the right hand chassis rail.

this would follow the prop and theres loads of room.

Am i missing something?

There isn't loads of room!

On a 4 cylinder the oil filter is right above the diff, and on a v8 the down pipe would be in the way.

Unless that is you run stupid amouns of lift that is.

Ok mine a v8.change the gearbox xmember and mount it there to the right? no manifold to worry about.

cyl engine,what about a remote oil filter set up.

What he says, total PITA. I've looked at it and I might be able to make it work but the exhaust would be 'interesting' and would give me issues with the intake pipework. Even then it'd be chronically tight so I'm doing something differant.

Well, Just back from Slindon.

Had a brilliant day driving around with Graham (Rocker) in the tipping rain!

The missing link suspension performed fantasticly. OK, it leans a bit when you drive, brake or engine brake - but it's not much worse than it was before. I tend to drive technical bits very slowly anyway.

I did most of the day with all the diffs (including the centre) unlocked - and didn't notice. I reckon it has improved the cross-axle capability by about 50%. Theres one bit I failed to drive before, in the dry, which is a serious cross axle up a big steep step. Although I had to use the middle & front lockers - it just gobbled it up!

I think a ram with a remote adjustable needle valve to damp the roll a bit off road and act as an anti-roll device on the road by closing the valve completly - will be an absolute winner!

There are not many mods I've done which in one hit have made such a big difference. Possibly a rear locker - but that's the only one I can think of!

Big smiley!

Si

Sounds like a positive result Si!

Have you considered beefing up the single bolt you now have on that side? Maybe upping the grade and thickening the axle mounts?

To be honest, I don't know the size of the bolt or the thickness of the existing plates, but going from 2 bolts to one (and consequently no redundancy) might be an issue?

Watching this one closely as it is almost a fit for the day type of mod as it stands!

Did you fit the standard arm to the left to counter act the drive torque? Did it make a difference?

Daan

I'll be waiting for my royalty cheque for the varidamp idea...

glad to hear the testing looks promising Si

Daan,

Not swapped sides yet. I think that will make a difference - it will matter less whether I brake or accelerate on left or right hand bends!

The original bolts are about M16 (or some imperial size that's about the same). I reckon there should be less shear force on the single bolt than ther is on it in the original configuration as it is not trying to restrain the axle from rotating.

On a 45 degree side slope, my back of an envelope force resolving calculation gives about two ton shear on the original bolts. The compressive/tensile force on the ram will be about 3 ton for the ram I have.

Cornering hard, the forces could well be higher though.

I think an M16 bolt is probably sufficient - but tell me if I'm way off!

Si

I think youre ok with a single m16 bolt in this application. After all, the three links available dont change this dimension either. What I would suggest is to fit longer bolts in this setup; I remember that the bolts on my axle had the threaded portion in the axle bracket. I replaced these with one size longer, so the shank sits in the bracket and the threaded portion starts just outside the bracket.

Daan

Si,

M!6 Grade 8.8 will eat three tonnes in shear, especially as it is in double shear. The weak point will be the mounting brackets on the axle - how thick are they?

You can get a good gauge of the shear capacity from the Steel Designer's Manual link I sent you a while back.

Should be good with the hydraulics. Well done Simon.

We too


Si,
did you bring the camera along?

Si, i have been running a very similar set up to what you have drawn in the background for over a year

the idea came about for more steering lock as much as articulation when trialing.

this was the mockup but has lasted all the awdc challenges, the argyll, inter club and trialing inbetween so well strong enough and sound on the road







i have had to u bolt the springs on to the chassis and axle to stop the springs from keep dislocating

this problem will be solved now as i am putting coilovers on and the same setup on the back, front on a normal truck

i will start mods on the truck after the last awdc challenge at slindon ready for next year

just starting to make the jig for new A frames

Saley,

That looks good! I was just doodling - another application for my trailing arm joint! Nice to see someone actually doing it though!

Bish,
The plates on either side of the axle mountings, at the moment are 6mm thick and have a minimum width of 40mm.

The forces action on them are entirely in the direction of max strength/rigidity. I think it looks about right - although, having said that, the Safari-guard 3 link uses 8 or 10mm thick plates so I may be wrong!

I'll try it!

My plan, longer term for the ram is to get a double ended ram made so it has the same swept volume on either side of the piston with a single flow control valve in the middle of a pipe connecting the ports.

I'll remote the knob on the valve into the cab using a speedo cable or similar. That means the hydraulics are quite self contained and you don't have to run any high pressure tube anywhere.

The rain seems to have stopped - so I can get on & fit the ram!

Si

Steerforth Si

they do a quick turnaround on custom rams

Thanks Jez,

I've used them before! Fairly local (Aldershot). Good for buying the components if you want to make your own rams too.

Si

No worries Si,


Saley - how long do you find the bushes last with your setup? looks cool - sort of torsion tube meets landrover