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Maybee they have welded on a new baracket to the diff (instead of bolt on plates or other bushes etc) to correct the angle.
 

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Discussion Starter · #3 · (Edited)
Could be, that would explain why the front of the arm looks so low but they dont look like standard arms to me. If it is some sort of custom arm you would think castor correction would have been built into the arm design.

I downloaded the pic and zoomed in, looks to me almost like an 80 series arm.
 

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80 series arms have been used a few times on Patrols. Have been told that They tend to flex a little better than the patrol arms because of the mounting system on the chassis and the bushes on the diff end are closer together which allows more flex.

Its hard to tell from that pic but looks like that is pretty likely.
 

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Discussion Starter · #5 ·
Ive started drawing up an arm that has similar mounting position at the diff to the 80 but with the bushes closer together and using bushes from the rear arms of a patrol. Hence my interest in this one.
The arms look to be mounted as low as the lowest point of the diff pumkin which is something i'll have to do to make them fit. Food for thought.
 

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80 series arms have been used a few times on Patrols. Have been told that They tend to flex a little better than the patrol arms because of the mounting system on the chassis and the bushes on the diff end are closer together which allows more flex.

Its hard to tell from that pic but looks like that is pretty likely.
my understanding:

95% to do with location of bushing location on radius arm. Patrol's are far apart and wrap around the axle.

The Toyota style rear bush connecting to the chassis does not improve articulation as much but rather improves ride quality. It absorbs alot more NVH and small bumps than the heavy duty pin style arrangement of the Patrol.
 

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Discussion Starter · #7 ·
my understanding:

95% to do with location of bushing location on radius arm. Patrol's are far apart and wrap around the axle.

The Toyota style rear bush connecting to the chassis does not improve articulation as much but rather improves ride quality. It absorbs alot more NVH and small bumps than the heavy duty pin style arrangement of the Patrol.
The 80 arms do have a noticeably less amount of space between the bushes at the diff.
 

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my understanding:

95% to do with location of bushing location on radius arm. Patrol's are far apart and wrap around the axle.

The Toyota style rear bush connecting to the chassis does not improve articulation as much but rather improves ride quality. It absorbs alot more NVH and small bumps than the heavy duty pin style arrangement of the Patrol.
The diff mounts on a patrol are 180 degrees appart where the landcruiser mounts are not as far apart. This makes the front end stiffer. Having a bush mounting at the chassis end also allows more movement. Both of these are engineered around with after market items like the flexi arms and also the 3rd's arms. The actual placement of bushes on the diff such as front and back or top and bottom make a difference on the stability of the front end rather than flex. Another example of placement of diff mounts are the landrover arms.
 

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Discussion Starter · #9 · (Edited)
The diff mounts on a patrol are 180 degrees appart where the landcruiser mounts are not as far apart. This makes the front end stiffer. Having a bush mounting at the chassis end also allows more movement. Both of these are engineered around with after market items like the flexi arms and also the 3rd's arms. The actual placement of bushes on the diff such as front and back or top and bottom make a difference on the stability of the front end rather than flex. Another example of placement of diff mounts are the landrover arms.
You wouldn't say a landrover arm has a lot more flex due to the placement of the bushes at the diff?
 

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You'd definately get more flex from the landrover arm. Look at the physical distance between the bushes on each arm. To give you an idea. This is an example that I've used before that has helped a few people better understand the limitations of the patrol front end.

Imagine the steering shaft on your car is the front axle housing and the steering wheel is where the radius arms, or in this case your hands, are mounted. The larger the steering wheel the easier it is to turn because your hands are further apart and can apply more torque to the steering. So if the Radius arm bushes are further apart they apply more torque to the axle housing.

Don't get me wrong. I'm not an engineer by any stretch of the imagination. But this is basic physics. Here is another practical experiment that you can do to try this out at home. Grab a broom stick that is skinny and grab something like a pipe off a vacuum cleaner. Now for each one, hold them out in front of you like an axle of a car and drop one arm and raise the other. You'll notice that one of your wrists will turn upwards and the other will turn downwards. Your axle does the same thing. Now do this again with each of them but try to keep your wrists dead straight. You'll notice that this is easier with the larger pipe from the vacuum cleaner. That is because of the diameter of the two objects. Just don't do this when the missus is home or she might think you're going to do some house work. :D

You'll also notice that while both the arms in your picture have the bushes spaced 180 degrees apart, they sit at different angles in relation to the axle. This alters the stability at different castor angles and because of the positioning of the nissan mounts, they have sacrificed some stability, ie the nissan shimmy. From my understanding this was a comprimse that was made to maximise ground clearance under the diff which as you can see from the OP's picture, it has the bush bush almost directly under the diff which means clearance has been compromised in that application.

All in all the main limiting factor of flex in the patrol front end is the torque on the axle housing that is created between the two radius arms trying to twist the axle housing in two different directions. Just like having a spanner on each end of it turning in opposite directions.

I hope this helps a little and I haven't confused people even more.
 

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Have done a fair bit of study on this stuff over the years. There has been quite a bit of variations of the beam arm system over the years starting from the Range Rover concept, which was really the first sucessful production system of note. After the design patent ran its course,this design was adopted by nissan except for the attachment positions RR being a lot closer together hence a little better flex at the expense of body roll stability. A lot of things come into play with this simple and strong system. Obviously the nissan design engineers had to compromise flex among other things to get cornering stability at lower speeds hence wider arm placement and stiffer chassis attachment for on road stability, this they did a good job with. Early F100's Vee coupling beam system by comparsion was a complete failure in the flex department but had great on road manners.
The other bits that play apart here are instant centres which are at infinity which isn't good for stability stiffness also roll axis angles are quite high hence when a lift kit is added you loose much of the vehicles inherent on road manners. Also my point here is toyota engineer's address many of these issues hence their design and placements on the diff and chassis what they ended up with is a roll centre height being well below the vehicles centre of gravity giving very nice on road manners and built in stability without loosing as much flex as nissan did with their design. Maybe the nissan engineers knew we Australians would lift our trucks and do silly things with their good compromise maths so they designed their front end with this in mind who knows, nice they did this for us eh. Had you owned a RR you would understand what i mean when you raise the height of one.
From the photo it does look like a toyota system why you would do this to gain very little is beyond me i am sure there are better or at least equal nissan type arms off the shelf for a hell of a lot less work. You would think for the trouble to do that they would just do a 3 link system to which you can design in better flex with nice on road manners.
Just to note this type of beam system doesn't address anti squat in any way which is what we need for offroad 4x4 work. Imagine what our humble patrol would be like with the squat traction the rear end has. This is one of the biggest compromise's our design engineers did sadly due to most patrols will and do only see very little offroad 4x4 incounters.
 

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Discussion Starter · #12 ·
Another way. Take the bushes out of the arms, place 2 pins at the same centers as where the bolts would be for each. Move each arm up and down until the pins stop the movement, mark where the arm stops in each direction at chassis end for each. You have the difference the position, size and flexibility of bushes at the diff can make. Looks to me thats part of the method used in the superflex arms, see below.
 

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Discussion Starter · #13 ·
Have done a fair bit of study on this stuff over the years. There has been quite a bit of variations of the beam arm system over the years starting from the Range Rover concept, which was really the first sucessful production system of note. After the design patent ran its course,this design was adopted by nissan except for the attachment positions RR being a lot closer together hence a little better flex at the expense of body roll stability. A lot of things come into play with this simple and strong system. Obviously the nissan design engineers had to compromise flex among other things to get cornering stability at lower speeds hence wider arm placement and stiffer chassis attachment for on road stability, this they did a good job with. Early F100's Vee coupling beam system by comparsion was a complete failure in the flex department but had great on road manners.
The other bits that play apart here are instant centres which are at infinity which isn't good for stability stiffness also roll axis angles are quite high hence when a lift kit is added you loose much of the vehicles inherent on road manners. Also my point here is toyota engineer's address many of these issues hence their design and placements on the diff and chassis what they ended up with is a roll centre height being well below the vehicles centre of gravity giving very nice on road manners and built in stability without loosing as much flex as nissan did with their design. Maybe the nissan engineers knew we Australians would lift our trucks and do silly things with their good compromise maths so they designed their front end with this in mind who knows, nice they did this for us eh. Had you owned a RR you would understand what i mean when you raise the height of one.
From the photo it does look like a toyota system why you would do this to gain very little is beyond me i am sure there are better or at least equal nissan type arms off the shelf for a hell of a lot less work. You would think for the trouble to do that they would just do a 3 link system to which you can design in better flex with nice on road manners.
Just to note this type of beam system doesn't address anti squat in any way which is what we need for offroad 4x4 work. Imagine what our humble patrol would be like with the squat traction the rear end has. This is one of the biggest compromise's our design engineers did sadly due to most patrols will and do only see very little offroad 4x4 incounters.
3 link + panhard in a patrol with on road manners?? Most people have said its not strong enough nor stable enough. I like this idea but have always been put off from what others have said.
 

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Nice try Grm but the front end is designed for breaking force which can under emergency conditions exert forces 10 times the weight of the vehicle hence such compronises are made for positioning also geometry takes a part here like caster and under brake stability this need to be 3 deg or better under heavy braking. Just to point out a few of the engineering maths need here.
 

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3 link + panhard in a patrol with on road manners?? Most people have said its not strong enough nor stable enough. I like this idea but have always been put off from what others have said.
Its all in the maths mate really it can be done and done well just look at or get a drive of a yank offroad racer. You wouldn't think these guys would do 100+mph in a rig if it didn't have nice manners. Not the IFS ones the beam axle units.
 

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Discussion Starter · #16 ·
Nice try Grm but the front end is designed for breaking force which can under emergency conditions exert forces 10 times the weight of the vehicle hence such compronises are made for positioning also geometry takes a part here like caster and under brake stability this need to be 3 deg or better under heavy braking. Just to point out a few of the engineering maths need here.
Sorry which part was a nice try? I thought you were suggesting a 3 link + panhard. Obviously you meant a radius arm + panhard 3 link.
 

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Discussion Starter · #17 ·
Its all in the maths mate really it can be done and done well just look at or get a drive of a yank offroad racer. You wouldn't think these guys would do 100+mph in a rig if it didn't have nice manners. Not the IFS ones the beam axle units.
The arms in those things are very long aren't they? Making all the difference?
 

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No not really its more to do with how all the maths bit come together for a racer it needs height as well so compromices come into play. i will post up a xcel sheet for you so you can see how it all fits.
 

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You can see some of the maths required but this will work on a patrol leaf spring chassis which has a bit more rail seperation for better numbers. These values are close to ideal for nice onroad manners at speed and flex to what ever shocks you can fit. also anti squat is about right for a front end daily drive.
 
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