Superior Engineering's Superfles Radius Arms

[Adrianjvr]

Anybody running a superflex radius arm? My next mod for Daisy will to manufacture such an arm. Standard arm so only the left side will be changed, therefore no caster correction. Anybody else interested? Maybe we can get a couple manufactured. I will start measuring up over the weekend.

[Russ Kellermann]

I would be interested of course. However, i fear that it won't be possible to run with just the plate, as the shape and length of superiors arms are of different dimensions to that of standard arms. Either that or drop boxes could be used perhaps to negate the use of caster correction bushes and set the connecting point of arm to axle back to stock, in addition to using the plate on the left.

[Gerrit Loubser]

I think what Adrian is saying is that he will manufacture an arm for the one side that works on the Superflex principal, but which has standard geometry (therefore no caster correction).

[Adrianjvr]

Gerrit, thats exactly what I was trying to say.

[Adrianjvr]

Refer to the attached image. Only the left hand radius arm will be manufactured.

[Peter Connan]

Adrian I have been seriously thinking about making myself a set of superflex arms, but because I need some castor correction I was going to use two arms, but with a large-centered polyurethane bush in the bottom of one of the arms.

Unfortunately it will be a while before I can actually afford to do this, so if you could send me your measurements I would be very gratefull. If you want me to do some drawings or FEA I will be most willing.

[Gerrit Loubser]

Why not fit the additional bush in both arms and keep the load paths symmetrical? With one stiff and one less stiff arm, the lion's share of the torque reaction (braking, acceleration) will be borne by one arm only.

[ricster]

Adrian.... I'm a bit blonde regarding this... please tell us more about this mod... what it does, advantages...etc.... is this basically a modified panhard arm if your suspension is raised?

[Gerrit Loubser]

It is a modified leading arm. Your front axle is located by two leading arms, which support traction and braking loads and torques and then the Panhard rod that locates the axle laterally and supports the sideways loads from cornering or running on a sideslope.

The problem with the Patrol's standard front axle suspension location system is that it has quite high roll stiffness and this roll stiffness increases non-linearly, the more the axle rolls relative to the chassis. The reason behind this is that the axle is attached to these leading arms by two rubber bushes on each arm. The only way that the axle can roll relative to the chassis is by deforming those rubber bushes; if they were steel bushes, axle roll would be impossible. As the bushes are deflected more and more, the bushes become stiffer and stiffer as the rubber has less and less space to deform into.

High roll stiffness limits front end flex (have a look at your Patrol when flexed out and you will see most of the flex is contributed by the rear axle, because the front is much stiffer), so if it is possible to reduce this roll stiffness, the front end flex increases and hence the vehicle's overall flex will be better. The Superflex arm achieves this by adding an additonal rubber bush into the equation. With the additional bush, there is more rubber to deform and hence the roll stiffness is lower.

This problem is not unique to the Patrol, but is shared by other vehicles that use radius arms to locate the axles. The Land Cruiser 80, 105, 76, 78 and 79 and the Land Rover Defender as well as the Disco 1 use the same system to locate their front axles. The Generation 2 Pajero uses radius arms to locate its rear axle, with the result that rear axle flex is quite limited on that vehicle (this means that overall flex for the Pajero Generation 2 is worse than on its competitors like the 90 Series Prado or Isuzu Trooper that use multi-link rear suspensions). On the Mercedes Gelaendewagen radius arms are used to locate both the front and rear axles and these vehicles are also not known for their flex-ability (they probably need their dual axle diff locks a lot more than a Patrol needs such a setup). I think the Disco Series II also uses radius arms to locate both its axles, but I am not certain.

[Adrianjvr]

The distance between the rubber bushes on the patrol is 240mm whereas this distance is 165mm on the range rover and 186mm on the land cruiser. Clearly this greater separation is why flex at the front of patrols is not as good as either the range rover or land cruiser. Basically the superflex arm moves the two bushes on the passenger side closer together (100mm) which reduces the stiffness of the front suspension. You will also notice from the picture that the standard bushes are essentially parallel with the ground whereas the superflex bushes are almost vertical, I think this helps apply more leverage on the bushes which assists the flexing. There are still only two rubber bushes on the superflex arm, the front connection is essentiall pinned and does not offer any movement. The arms should be relatively easy to have laser cut from 32mm 300WA plate. Because both bushes on the superflex arm are still equally radially spaced on the axle there will be differential traction or braking forces introduced into the axle.

Peter you are welcome to any drawings or measurements. The castor correction can be done relatively simply on the superflex arm by changing the location of the middle bush, maybe you would consider castor correction bushes on the right radius arm then you only need to fabricate the one arm. I'll give you a shout if I need any assistance on the drawing side. Hopefully I can convince one of the draffies at work to assist.

Anybody have a loose radius arm lying around that will assist with measurements?