3 Link front ends

[Steve 90]

Excelent, Im with you. Thankyou.

[will_warne]

Will,you are aware that on an X link setup that the hockey sticks attach behind the axle on the standard brackets in the usual manner ? The impact forces from wheels hitting bumps etc is transmitted into the chassis via the hockey sticks as it does in a standard setup. The X link centre pivot just resists the forces trying to roll the axle assembly backwards and forwards due to impact, accellerating and braking forces in much the same way that the 3rd link of a 3 link system does. Whilst the force acting on the centre pivot can be significant it is not ''concentrating all the force'' just all the torsional force that the vehicles tractive effort and braking system can generate.

Bill.

Bill - yes, I'm aware the rear mounting point is unaffected. You are right is is not 'all the force' - it should have read 'all the force that would be concentrated on the front part of the hockey stick mount or 3rd link in a 3 link system'. However, they are significant forces and you don't want the pivot either bending or parting company with the axle casing.

[Bush65]

Anyone is welcome to correct me if I'm wrong. The way I see it after previously experimenting with removing radius arm bolts etc is that for the holey bushes to do any good re increased articulation, the 2 holes in each bush would need to be more or less positioned vertically. Is this not the the same area of the bushing material where compression resistance is required to resist braking and axle tramp forces ? Seems to me that safe handling and true offroad performance is compromised for the sake of a bit of flex, particularly as flex is less important these days when many of the serious players have locking differentials.

Bill.

Stock landcruiser radius arm bushes are moulded with slots in them. And I have some patrol radius arm bushes with moulded slots.

IMHO the slots moulded in the Haultech bushes are oversize for mush use on road, and something like the landcruiser or patrol ones I mentioned are what I would like to see (except I have no need since I am fitting a Dobbin X-link in the rangie (not with rangie axle or radius arms though)).

BTW Glen Dobbin intended the 'X' (in X-link) to be interpreted as cross-link.

The problems fitting an X-link to a rover are not limited to the location of the panhard mount. Rover radius arms are too close to the axle housing to benefit from the X-link. I'm using landcruiser radius arms and a relocated panhard to overcome the problems.

[will_warne]

Stock landcruiser radius arm bushes are moulded with slots in them. And I have some patrol radius arm bushes with moulded slots.

IMHO the slots moulded in the Haultech bushes are oversize for mush use on road, and something like the landcruiser or patrol ones I mentioned are what I would like to see (except I have no need since I am fitting a Dobbin X-link in the rangie (not with rangie axle or radius arms though)).

BTW Glen Dobbin intended the 'X' (in X-link) to be interpreted as cross-link.

The problems fitting an X-link to a rover are not limited to the location of the panhard mount. Rover radius arms are too close to the axle housing to benefit from the X-link. I'm using landcruiser radius arms and a relocated panhard to overcome the problems.

I think the reason 'X' is used is a short hand for cross (I often do the same refering to chassis cross members).

The closeness of the arms to the axle casing is an issue however I might be changing the bracketry and layout a bit The main reason for staying with Rover is spares are easy and cheap to get hold of if they bend.

[Bowie69]

If Si made one, I guess it would be called the 'X-X'

Otherwise known as the emoticon for 'blotto'

[Warthog]

I've been working on an anti roll bar with disconnects - which is surprisingly hard on a LR. I have a pretty neat solution now which just needs building and testing. This should give you decent road handling even if you have extra flexible front and rear ends.

Si

Jeepers have a few different designs out there for the TJ's etc. Have always wondered how the front set-up could be adapted to LR? With a few measurements i thought there was a possiblity that such designs could work? But of no use if you are running Radius arms.

Couple of piccies i have pulled of the www

[simonr]

I like the free-wheeling hub idea - shame they are so expensive!

Si

[bill van snorkle]

I like the free-wheeling hub idea - shame they are so expensive!

Si

Simple easy to make 2 dog sliding clutch ?

Bill.

[bill van snorkle]

Stock landcruiser radius arm bushes are moulded with slots in them. And I have some patrol radius arm bushes with moulded slots.

IMHO the slots moulded in the Haultech bushes are oversize for mush use on road, and something like the landcruiser or patrol ones I mentioned are what I would like to see (except I have no need since I am fitting a Dobbin X-link in the rangie (not with rangie axle or radius arms though)).

BTW Glen Dobbin intended the 'X' (in X-link) to be interpreted as cross-link.

The problems fitting an X-link to a rover are not limited to the location of the panhard mount. Rover radius arms are too close to the axle housing to benefit from the X-link. I'm using landcruiser radius arms and a relocated panhard to overcome the problems.

John,are the slots in the Toy/Nissan bushings vertically displaced ? I believe the bushings on Toy/Nissan hockey sticks are spaced significantly further apart than on LR's. So on a standard setup, for a given degree of articulation the bushings need to distort more and need to be larger in diameter,and indeed they are. The hockey sticks probably also need to be mounted further away from the axle housing than on a LR. Forgetting about dynamic behavior, simply removing the left hand front hockey stick bolt on a LR significantly improves axle articulation, so I would disagree that LR's hockey sticks are too close to benefit from the cross link. I would in fact hazard a guess that tyre clearance to the right hand side spring/shock tower would become the limiting factor to articulation before axle housing to hockey stick clearance would. Possibly Dobbin Eng is more concerned about effective link separation distance to control torque reaction rather than hockeystick to axle housing clearance?

Has Dobbin engineering, whom incidently I have a lot of respect for, actually tried to do a crosslink to a LR ? Or did they dismiss the idea based on a quick visual? The only reservations I personally have about a properly executed cross link is that there appear to be a few extra snag points to get hung up on rocks etc, and in photos at least,depending on how much the axle is articulating, the crosslink appears to reduce ground clearance under the axle tubes.Are there any advantages you are aware of compared to a One link ? One other question, do you believe highly compliantbushings are still required once the crosslink has been installed ? or could the hockey sticks be sleeved down to accept a more rigid bushing to possibly improve handling ?

Your thoughts ?

Bill.

Edit. sorry more questions. Because the Crosslink is basically made from flat section steel plate I assume it is torsionally flexible, as going by the offset shape of it in photos some of the forces acting upon it would be torsion in nature. If so,is it made from spring steel ? If not, are there any concerns about fatigue cracking ? If it is made from spring steel do you think the springiness could contribute to magnifying axle tramp under brakes or in marginal traction conditions ?

[dirtydiesel]

John,are the slots in the Toy/Nissan bushings vertically displaced ? I believe the bushings on Toy/Nissan hockey sticks are spaced significantly further apart than on LR's. So on a standard setup, for a given degree of articulation the bushings need to distort more and need to be larger in diameter,and indeed they are. The hockey sticks probably also need to be mounted further away from the axle housing than on a LR.

My experiance with toy's and g's which both have much greater separation than rover is that they have more flex. i've put this down to the bushes being further from the axle centerline thus needing to deflect less for a given amount of flex.

70 and 80 series front radius arms are mounted further from the case than a rover though, allthough 70 series rear are mounted quite close to the tubes but still offer good flex.

One thing i have noticed is that 70 series rear and Gwagon rears both angle the radius arms in toward the center of the vehicle, IE; the centers on the radius arms are wider at the axle than the chassis.

[bill van snorkle]

My experiance with toy's and g's which both have much greater separation than rover is that they have more flex. i've put this down to the bushes being further from the axle centerline thus needing to deflect less for a given amount of flex.

I'll have to rummage through my daughters school stuff and see if I can find a compass and protractor to check if that is correct. My admittedly sometimes dyslexic brain sees it the other way round.

Of course as you move the left and right chassis mounts of the hockey sticks closer and closer together you need less deflection at the axle bushings. If you bend the hockey sticks inwards at the chassis end and mount them close together side by side on a suitable crossmember you will get lots of flex even with quite hard non compliant bushings at the axle end.In effect by doing this you have almost created a ''One Link'' which doesn't require any flexible bushings at the axle mounts. Imagine that, you can drive all day every day over the twistyest terrain possible without ever having to replace a suspension bush, save the panhard ones.

Bill.

[will_warne]

Bill, I think there are two reasons Dobbin may not have looked at doing a X-link: the fact that you have to change the Panhard rod arrangement and the small market in Aus is my thoughts on that.

I'd agree with you on the issues surrounding ground clearance and linkage design. Its something I'm going to try and address.

[bill van snorkle]

Bill, I think there are two reasons Dobbin may not have looked at doing a X-link: the fact that you have to change the Panhard rod arrangement and the small market in Aus is my thoughts on that.

Just look at how successful Maxidrive Engineering became.With basically sound, rust free Range Rover Classics and series one Disco V8's selling for peanuts there is a large enough enthusiast market for Rover products alone to keep a firm the size of Dobbins afloat.With one or two exceptions what I have found is that most specialist 4wd firms over here are operated by people that (possibly for valid reasons) absolutely abhore LandRovers and run a mile when one pulls into their forecourts.,

Bill.

[RangeyRover]

Bill,

I am seriously looking at this for my RRC. I have access to a good guy in Derby UK for the welding (Frank Worthington if anyone else wants serious welding in the area)

Moving the panhard doesn't seem too tough. What thickness plate do you think the cross link needs to be made from? Dobbins looks like 10 or 12mm which seems huge.

Over engineering is ok, but thats going to be really heavy.

Dobbins seems to have changed from a bent plate to a flat one with extensions to reach the radius arms bushes. There also seems to be a larger gap than the axle bracket had. That also means that the central swivel is now quite long. do you think that's a problem?

Will,

How far have you got down the road with this?

[will_warne]

Bill,

I am seriously looking at this for my RRC. I have access to a good guy in Derby UK for the welding (Frank Worthington if anyone else wants serious welding in the area)

Moving the panhard doesn't seem too tough. What thickness plate do you think the cross link needs to be made from? Dobbins looks like 10 or 12mm which seems huge.

Over engineering is ok, but thats going to be really heavy.

Dobbins seems to have changed from a bent plate to a flat one with extensions to reach the radius arms bushes. There also seems to be a larger gap than the axle bracket had. That also means that the central swivel is now quite long. do you think that's a problem?

Will,

How far have you got down the road with this?

Bill - good point. I guess it may be the panhard rod issue.

Rangey - I've got as far as some sketches and some basic mock ups on the bench after taking some measurements. I've mostly been trying to sort the rear suspension first. Initially I was looking to do something fairly simple and similar to the Dobbins setup but with a relocated panhard rod. That looked like it would work pretty well. However, I'm now planning something a little less conventional in an effort to improve ground clearance. Its all on paper at the moment and I've no idea how it'll work when I try and throw things together.

What really intrigues me about the Dobbin setup is the use of plate for the cross link. I assume this is because of packaging (ie to fit between the axle casing and not fowl with the steering) as tube or box would be a more elegant solution.

[bill van snorkle]

Bill,

I am seriously looking at this for my RRC. I have access to a good guy in Derby UK for the welding (Frank Worthington if anyone else wants serious welding in the area)

Moving the panhard doesn't seem too tough. What thickness plate do you think the cross link needs to be made from? Dobbins looks like 10 or 12mm which seems huge.

Over engineering is ok, but thats going to be really heavy.

Dobbins seems to have changed from a bent plate to a flat one with extensions to reach the radius arms bushes. There also seems to be a larger gap than the axle bracket had. That also means that the central swivel is now quite long. do you think that's a problem?

Will,

How far have you got down the road with this?

I haven't actually seen an X link in the flesh, so my opinions are only based on what I can glean from photos on the web.I could also be accused of splitting hairs, but IMO that is what offroad vehicle engineering is about. A few mm of ground clearance or a degree or two of approach/departure/ rampover angle can make all the difference, and a modification to acheive a certain aim should not compromise the vehicles abilities in other areas.

The potential problems I see with the X link is that the beam is subject to undamped torsional flexing and rebound forces imposed by drive and braking loadings,that in addition to the undamped flexing and rebound forces of the hockey stick bushings may magnify traction robbing axle tramp. The location of LR front dampers directly on top of the axle does nothing to control axle tramp either, so relocating these may be required when fitting an X link. If the X link is indeed subject to flexing then the metal probably needs to be substantial enough to minimise fatigue cracking.

If Dobbins have moved the centre pivot further forward then this would effectively increase the link separation distance for improved tramp control, but then my other concern would be that the axles ''approach'' angle in relation to the front of the tyres,or for want of a better term, the horizontal ground clearance of the axle housing is compromised. I built a Watts Linkage for the front of my old ''One Link'' equipped 6x6, and although the equaliser didn't protrude any further forward than the centre pivot of an X link, and the lower part of the equaliser was no lower than that part of the axle tube the front end would occasionally get hung up on the linkage in situations where a panhard rod would have cleared. Reversing off a rock or stump that ends up between the X link beam and the axle housing could be interesting too.

The way I see it ,for better or worse most of the important suspension geometry of hockey stick and ''One Link'' arrangements are similar,but the one link controls axle tramp better and doesn't compromise ground clearance etc.There is probably no more fabrication work involved in making the one link wishbone than replicating an X link, and the LR axle housing including panhard rod mount doesn't need to be modified at all.

Bill.

[dirtydiesel]

The location of LR front dampers directly on top of the axle does nothing to control axle tramp either, so relocating these may be required when fitting an X link.

How much effect would relocating the damper have do you think?

Interesting that toy's, patrols and G's all have theirs mounted about 6" behind axle centerline, all with pin bottom shocker as well, It's almost like there's some kind of universal advantage to this setup that landrovers engineers wern't party to.

[bill van snorkle]

How much effect would relocating the damper have do you think?

Interesting that toy's, patrols and G's all have theirs mounted about 6" behind axle centerline, all with pin bottom shocker as well, It's almost like there's some kind of universal advantage to this setup that landrovers engineers wern't party to.

The further away from the axle centre the more leverage the damper has to control the tendency of the axle housing to rotate in the opposite direction to the wheels (torque reaction) However bump and rebound forces may tend to roll the housing more which may cause bump steer or some other feel of imprecise steering. This may have been Rover engineers main concern. Or maybe they didn't think about it at all.

Also the closer to the chassis pivot bushings of the hockey sticks that the dampers are mounted, the greater the vertical wheel travel for a given stroke damper.

Bill.

[will_warne]

Bill - I'd agree wit you about the cross link in the Dobbins design. As I've not seen one either and have only passable knowledge of Jap axle setups I assume the linkage design is dictated by ensuring steering clearance, and as you say, approch angle.

One thought I had was running the hockey stick over the axle rather than under it.

[Daan]

The further away from the axle centre the more leverage the damper has to control the tendency of the axle housing to rotate in the opposite direction to the wheels (torque reaction) However bump and rebound forces may tend to roll the housing more which may cause bump steer or some other feel of imprecise steering. This may have been Rover engineers main concern. Or maybe they didn't think about it at all.

Also the closer to the chassis pivot bushings of the hockey sticks that the dampers are mounted, the greater the vertical wheel travel for a given stroke damper.

Bill.

If I had a choice to locate the dampers, I would say that on top of the axle, like landrover did is best. The axle tramp may be a reason not to, but the forces on the bushes trying to counteract the damper forces are pretty big. To put it in perspective, in a dynamic situation, driving fast over potholes, the peak forces on the damper are much greater than on the springs. Landrover understood this on the first rangerovers, where the rear dampers were asymetrical, one pointing forward, one pointing backwards to counter act the forces.

I went for the shocks on top of the axle on every corner, and I like the setup very much.

daan

[bill van snorkle]

If I had a choice to locate the dampers, I would say that on top of the axle, like landrover did is best. The axle tramp may be a reason not to, but the forces on the bushes trying to counteract the damper forces are pretty big. To put it in perspective, in a dynamic situation, driving fast over potholes, the peak forces on the damper are much greater than on the springs. Landrover understood this on the first rangerovers, where the rear dampers were asymetrical, one pointing forward, one pointing backwards to counter act the forces.

I went for the shocks on top of the axle on every corner, and I like the setup very much.

daan

Thanks Daan,I understand your point.I could have worded it better, but I tried to give the other side of the damper mounting theory when I wrote "However bump and rebound forces may tend to roll the axle more which may cause bump steer or some other feel of imprecise steering''

However,air suspended RRC's have their damper mounted well forward of the axle centreline.These have identical hockey stick bushings to coilers.Anyone know if the rough terrain handling or steering feel of these vehicles is in anyway inferior to the coiler versions ?

Bill.

[dirtydiesel]

One thought I had was running the hockey stick over the axle rather than under it.

I've done this on a trialler and found that combined with greater bush separation it gave increased articulation as well as improved ground clearance.

[simonr]

I've had a thought! The X-Link is a pretty good solution - with some obvious technical difficulties. Bill mentioned using a watts linkage - and it occurs to me that if you made the cross link out of two flat plates with a gap inbetween, you could share the cross link pivot with the watts link pivot for the toggle. The watts linkage arms (connecting to the chassis on either side) can then partially live inside the the gap between the plates. That means the watts link does not need to be any further forward than the X link. The fact that the X link has no top and bottom makes little difference to the strength as there should be very little longitudinal strain.

In fact, the cross link could bulge out around the diff pan on one side and that side be boxed in top and bottom to cope with the additional torsional load. the upper watts link goes on that side and the lower link can pass between the open plates on the other (straight) side. That way, neither the watts nor X link needs to project much further forward than the existing panhard rod.

This has a sort of elegance in my mind giving symetry and clearance.

Si

[will_warne]

Very interesting idea Si. I thought about combining the pivot point in a conventional manner however I hadn't thought about combining both together. That would work really nicely on a back axle.

[bill van snorkle]

Very interesting idea Si. I thought about combining the pivot point in a conventional manner however I hadn't thought about combining both together. That would work really nicely on a back axle.

Will.Unless you were playing with a series 2 Disco why would you feel the need to over complicate the rear end by replacing the excellant A frame plus two lowers with hockey sticks and an X link ?

Simon. although I have built two vehicles with Watts link front ends, and the bump steer issue was nowhere near as serious as some think, these and upper wishbone 3 link style front ends are probably really more suited to full hydro steering.

Bill.