3 Link front ends

[bill van snorkle]

thanks Bill, i'd love to see your libary, let alone understand half of it

with regards to the crosswind stability: wind hits side of vehicle, trys to push it, tyres have grip so body gets pushed, which results in compression on the left side as the right is raised. this compression of the suspension makes the arms travel up becoming more level, which pushes the axles away from there location.opposite is happening on the right, axle goes into down travel and gets closer(shortens the wheel base) so although the body has leaned to the left the car wants to steer to the right.

is this correct?

so as an example would you think that an arm 50% longer would be dangerous with regards to antisquat?

dont worry i wont hold you to it

Serg

Unfortunately Serg the library such as it was, and located in my old caravan was destroyed and eaten by mice and rats a few years ago.

Your understanding of the crosswind stability principal is bang on.

I don't beleive 50% longer arms would not make the vehicle dangerous re antisquat. Many vehicles including some road cars don't have any antisquat geometry whatsoever built into their suspension and they seem to do ok. I just think it is a useful commodity to have particularly on a SWB to reduce the chances of rear wheel lock up during heavy braking. Also when I originally converted from front leaf springs (no anti squat) to hockey sticks the improvement in front end traction on steep climbs was immediately apparent.(Antisquat geometry give squat when the front axle is pulling.) I later changed to 3 link but the antisquat geometry is not that much different to the hockeysticks.

Bill.

[Bush65]

Serg,

I think you meant anti-dive not anti-squat.

Since we are discussing front geometry and longer radius arms, and simplifying the situation, you can judge the ant-dive (anti-squat if reversing) behaviour from the angle that the radius arms make to the horizontal - steeper angle will increase the anti's. Under brakes, the force in the arms will try to lift the chassis, countering (to a degree) the increased downward load on the front springs due to inertia of the vehicle mass at the vertical centre of gravity.

With the same suspension lift, longer arms will be flatter. But most of us have lifted suspension anyway.

Lessened anti-dive is not dangerous, IMHO it's mainly a feeling (for occupants) that is at issue.

[uninformed]

Unfortunately Serg the library such as it was, and located in my old caravan was destroyed and eaten by mice and rats a few years ago.

Your understanding of the crosswind stability principal is bang on.

I don't beleive 50% longer arms would not make the vehicle dangerous re antisquat. Many vehicles including some road cars don't have any antisquat geometry whatsoever built into their suspension and they seem to do ok. I just think it is a useful commodity to have particularly on a SWB to reduce the chances of rear wheel lock up during heavy braking. Also when I originally converted from front leaf springs (no anti squat) to hockey sticks the improvement in front end traction on steep climbs was immediately apparent.(Antisquat geometry give squat when the front axle is pulling.) I later changed to 3 link but the antisquat geometry is not that much different to the hockeysticks.

Bill.

im think more along the lines of a 110defender so swb wont play in too much. sounds like anything with a 3inch spring lift or something running MD portals would benefit from longer arms.

the reason i think its a good option is: uses all stock bushes, no axle moddifications.

also are people rasing the panhard rod mount on the axle on lifted vehicles, to bring it back to level, im thinking you'd also need to bring the front steering link parallel with the panhard....

Serg

[russ1]

I know this is abit OT but looking at a few peoples builds on here are mounting the front hockeysticks upside down with the mounts on top of the axle,

What benefit is this?

[uninformed]

Serg,

I think you meant anti-dive not anti-squat.

Since we are discussing front geometry and longer radius arms, and simplifying the situation, you can judge the ant-dive (anti-squat if reversing) behaviour from the angle that the radius arms make to the horizontal - steeper angle will increase the anti's. Under brakes, the force in the arms will try to lift the chassis, countering (to a degree) the increased downward load on the front springs due to inertia of the vehicle mass at the vertical centre of gravity.

With the same suspension lift, longer arms will be flatter. But most of us have lifted suspension anyway.

Lessened anti-dive is not dangerous, IMHO it's mainly a feeling (for occupants) that is at issue.

Hi John,

i just saw your reply. yes i ment anti-dive and thats what i reffered to in my first reply. Bill referred to anti-squat so i went with it... i didnt know any better and to me its all the same. vehicle wants to sqaut down on the chassis. but im guessing there is more difference than that.

also whats it called when the chassis mount to contact patch is steep and you are travelling forward, hit a bump and the axle wants to climb back under the vehicle? because this will be helped when the arms are longer.

Serg

[bill van snorkle]

John (Bush 65) is right. I've been inadvertently referring to antidive as antisquat.Not sure why I have started doing that

Bill.

[bill van snorkle]

I know this is abit OT but looking at a few peoples builds on here are mounting the front hockeysticks upside down with the mounts on top of the axle,

What benefit is this?

I think it's just done to optimise ground clearance.

Bill.

[Bush65]

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 ?

On nissan/toyota radius arms I have seen, the bushes have not been installed with holes/slots in a uniform orientation - my guess is they may not have been the original bushes and the fitter knew no better. BTW, the chassis end rear radius arm bushes and trailing arm bushes are also slotted on 105 series cruisers.

Yes the bushes are considerably larger in diameter to allow increased flex.

As I understand, they did not try to fit an X-link to a rover, but did look carefully at it.

Later examples of the X-link I have noticed, have changes to improve clearance.

Compliant bushes are still needed to allow the radius arm to twist relative to the axle housing. Depending on the arrangement at the chassis there could be benefits to handling by using different bushings with less flex.

The torsion does not seem to be an issue - the plate thickness is great enough.

I don't know what material is used. I know of one that was made from Bissalloy 80.

I can't see much benefit from using high strength or spring steel, unless you were concerned with the weight. And if that was a great concern, there are probably better suspension options.

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?

Dobbin use 20mm thick plate.

The 1st X-links were simply flat plate. Some later X-links have been pressed (non-flat).

[Bush65]

im think more along the lines of a 110defender so swb wont play in too much. sounds like anything with a 3inch spring lift or something running MD portals would benefit from longer arms.

the reason i think its a good option is: uses all stock bushes, no axle moddifications.

also are people rasing the panhard rod mount on the axle on lifted vehicles, to bring it back to level, im thinking you'd also need to bring the front steering link parallel with the panhard....

Serg

Raising the panhard to more horizontal will help with roll steer, but that is not a big advantage since the driver can correct front roll steer by turning the wheels (I'm not considering high speed issues here).

An advantage of raising the panhard is that it will raise the roll centre.

The big disadvantage may be clearance to the chassis on full bump travel (but I haven't been playing with rover axles/steering arrangement for some time so my memory may be off).

The other problem you could have with longer radius arms is clearance to the body mounts on maximum up travel - may need to lower the chassis mounts.

[Bush65]

I know this is abit OT but looking at a few peoples builds on here are mounting the front hockeysticks upside down with the mounts on top of the axle,

What benefit is this?

As Bill said, it increases clearance. But the spring perches on a rover introduce a degree of difficulty. I would like to see how they mount the front coils.

[Bush65]

Hi John,

i just saw your reply. yes i ment anti-dive and thats what i reffered to in my first reply. Bill referred to anti-squat so i went with it... i didnt know any better and to me its all the same. vehicle wants to sqaut down on the chassis. but im guessing there is more difference than that.

also whats it called when the chassis mount to contact patch is steep and you are travelling forward, hit a bump and the axle wants to climb back under the vehicle? because this will be helped when the arms are longer.

Serg

Anti-squat and anti-dive are just different terms to distinguish between 2 different situations (one accelerating and the other decelerating).

At the rear, squat (during acceleration) is an issue, while at the front, dive (during deceleration) is an issue. Both these affects are due to weight transfer when accelerating/decelerating. Suspension geometry can be designed to counteract (anti-) the squat/dive by creating forces that assist the springs.

I'm not sure that there is a correct term for the jacking affect you described. The kinematics are the same as anti-squat/dive.

It is a problem with steep link angles. You may have noticed the better set-up nissans with big suspension lifts 6" etc. use drop boxes to lower the chassis end of the radius arms - for castor correction and this jacking affect.

[uninformed]

Anti-squat and anti-dive are just different terms to distinguish between 2 different situations (one accelerating and the other decelerating).

At the rear, squat (during acceleration) is an issue, while at the front, dive (during deceleration) is an issue. Both these affects are due to weight transfer when accelerating/decelerating. Suspension geometry can be designed to counteract (anti-) the squat/dive by creating forces that assist the springs.

I'm not sure that there is a correct term for the jacking affect you described. The kinematics are the same as anti-squat/dive.

It is a problem with steep link angles. You may have noticed the better set-up nissans with big suspension lifts 6" etc. use drop boxes to lower the chassis end of the radius arms - for castor correction and this jacking affect.

i would have thought that the body mounts could be cut and strengthend to do there job and maintain clearence. drop boxes would have to hang down and become a issue for clearence

well it sounds like that longer radius arms with a bit of thought could be a good option for lifted vehicles. even if only 2 inch lift. maybe not the out right flex of a 3 link but for a road going vehicle i think they might work.

Serg

[redneck]

hi

I have been thinking about what suspension set would work on the front of my disco for a while now and was convinced that a triangulated 4 link would be the asnswer.

But after a little bit of lateral thinking about the restriction of the bushes on the standard front axle, I thought what about fitting the axle bushes in line with the hockeystick and fitting a transverse bush at the rear end of the h/s. This would require fabrication of a new h/s and some fab work on the axle, but a bolt on bracket to the chasis (avoiding the sva etc). It wouldn`t change any of the standard geometry and the bushes would work in the direction designed for with little or no restrictions.

Can you think of any problems with this design??????

[Bush65]

hi

I have been thinking about what suspension set would work on the front of my disco for a while now and was convinced that a triangulated 4 link would be the asnswer.

But after a little bit of lateral thinking about the restriction of the bushes on the standard front axle, I thought what about fitting the axle bushes in line with the hockeystick and fitting a transverse bush at the rear end of the h/s. This would require fabrication of a new h/s and some fab work on the axle, but a bolt on bracket to the chasis (avoiding the sva etc). It wouldn`t change any of the standard geometry and the bushes would work in the direction designed for with little or no restrictions.

Can you think of any problems with this design??????

Front triangulated 4 link is not suitable for a vehicle driven on road due to bump/roll steer.

Regarding the later part of your post regarding the chassis bush for the radius arm - this type of radius arm is common, e.g. disco II and similar era rangies, and all coil sprung toyota landcruisers.

The disco II radius arms are longer than those on disco I, but if I understood what you were proposing, the radius arms would be shorter, which is a small disadvantage.

Changing the chassis bush is not going to net you much improvement in articulation if the radius arm is shorter.

[plasticbadger]

Front triangulated 4 link is not suitable for a vehicle driven on road due to bump/roll steer.

Holy thread resurection!

The problem with the triangulated 4 link is that you don't get axle side-to-side movement with up travel, like you do with a panhard rod. Therefore you get bump steer from the angle change in the drag link with up travel. The triangulated 4 link would be great with full hydro steering though.

The easiest way to get big articulation while keeping standard steering is with a 3 link (IMHO). I've found that you get much more balanced front/rear articulation making the truck more stable. The on-road handling of my creations is not great, but that's more about lift than geometry, you don't get any more bump steer than the standard setup with my geometry. Here's my Disco and Rangie on a 3 link:

And i'll be building another 3 link shortly...

[Tomcat Nev]

On the subject of longer 'Hockey sticks'

I know its not the same as extreme off roading but i lengthened by radius arms so that they met in the middle of the chassis, i also fitted them to the rear. The arms used 110 double metal type bushes and the chassis end used Disco II type bushes. The extensions were made from solid bar drilled and tapped to screw onto the radius arm. The only time any thing bent was when i hit a tree at speed!

The amount of travel afforded was increased over the stock set up but limited by the damper length - 12". My biggest gain was the reduction of axle steer whilst flexing at speed. It also gave really good stability and although the rear panhard was longer the front and rear acted in harmony which allowed me a greater confidence to push it. The feeling on the road was very good and forgiving. The car now lives in Greece and has won the championship where it races so i must have done something right!

[mick110]

I've marveled at all the ingenuity/inventiveness of all the postings{it's what make Britain Great!]....but ,simple soul I am ...what is the bottom line? what do you want [via these complex Heath Robinson ...dangerous?/illegal? mods] to achieve?....foward motion over undulating terrain...ans.= axle lockers...safe/proven/legal

[plasticbadger]

I've marveled at all the ingenuity/inventiveness of all the postings{it's what make Britain Great!]....but ,simple soul I am ...what is the bottom line? what do you want [via these complex Heath Robinson ...dangerous?/illegal? mods] to achieve?....foward motion over undulating terrain...ans.= axle lockers...safe/proven/legal

A bit of an extreme question, as I can't really understand why anything discussed here is complex/heath robinson/dangerous/illegal if it's built properly, engineered correctly and done in accordance with the law. My mods are none of the things you state and my next 3 link be going through an SVA in addition to the MOTs that my current set up has. What specifically would be complex/heath robinson/dangerous/illegal on my cars pictured?

However, the reason I did what I did was when I fitted Landcruiser axles to my Discovery, to get lockers and tough axles without spending huge money, I found that there was a clash between the steering and where the hockey sticks would be. That got me thinking and the 3 link answered the packaging issue while also giving me improved articulation. The end result has been to dramatically improve off road performance without comprimissing on road performance, in fact my setup has significant anti-dive which can be an advantage to controlling the car under hard braking.

Lockers do give you forward motion, true, but the standard Landrover suspension setup gives very limited front articulation and excellent rear articulation - result the car rolls as the front end goes over the obsticle and then the rear axle follows the terrain. By improving the front end articulation both axles follow the terrain and the body stays more upright. End result the drive over rough terrain becomes more balanced and feels smoother, allowing you position the car more accurately and ultimately safer.

[mick110]

A bit of an extreme question, as I can't really understand why anything discussed here is complex/heath robinson/dangerous/illegal if it's built properly, engineered correctly and done in accordance with the law. My mods are none of the things you state and my next 3 link be going through an SVA in addition to the MOTs that my current set up has. What specifically would be complex/heath robinson/dangerous/illegal on my cars pictured?

However, the reason I did what I did was when I fitted Landcruiser axles to my Discovery, to get lockers and tough axles without spending huge money, I found that there was a clash between the steering and where the hockey sticks would be. That got me thinking and the 3 link answered the packaging issue while also giving me improved articulation. The end result has been to dramatically improve off road performance without comprimissing on road performance, in fact my setup has significant anti-dive which can be an advantage to controlling the car under hard braking.

Lockers do give you forward motion, true, but the standard Landrover suspension setup gives very limited front articulation and excellent rear articulation - result the car rolls as the front end goes over the obsticle and then the rear axle follows the terrain. By improving the front end articulation both axles follow the terrain and the body stays more upright. End result the drive over rough terrain becomes more balanced and feels smoother, allowing you position the car more accurately and ultimately safer.

I don't doubt the integrety of your particular job....but all these postings may encourage the less able but keen/brave bodgers to experiment I'm all for experimentation/inventiveness for strictly off road driveing but believe the road hsndling could be compromised , as they say ...."if it's such a good idea manufacturers would have been there long ago"

[bishbosh]

I don't doubt the integrety of your particular job....but all these postings may encourage the less able but keen/brave bodgers to experiment

That is what Darwin is for

if it's such a good idea manufacturers would have been there long ago"

Not true. Manufacturers have to build cars that handle well on road in the first instance, off roading comes second. Three link builders are optimising off road performance at the expense of on road handling. I don't think anyone would say a three link front end corners on rails.......

[Bush65]

... This would require fabrication of a new h/s and some fab work on the axle, but a bolt on bracket to the chasis (avoiding the sva etc). ...

For those interested, here are some pics that illustrate some similar thinking.

The orange chassis mount is a bolt on for a Nissan Patrol, which normally mount the radius arm in the same way as Land Rover (in fact Nissan radius arms and bushes will fit straight into a L.R.). The aluminium bushes (above the horizontal plate) replace the stock rubber bushes in the normal radius arm mount.

In the other pic, the black chassis mount is welded on. It is very common here to lift Nissan Patrols (and Toyota Landcruisers) 6" or more, and similar 'drop boxes' are usually used for the radius arms to correct the geometry.