Flipped Radius arms

[v840]

I think we're saying the same thing.

[80's_delirious]

gotcha

[lukethedork]

Yea, I think I was getting kinda confused with AS and the effect that a steep front control arm will have when you try to push up an obstacle.
I some how thought that the two would be connected. But it appears not.

Luke.

[1MadEngineer]

i know i don't explain stuff real well, i tend to skip over a few design elements (oops), when i talk AS, i am also relating this to attack angles and resultant forces. (luckily RA dont suffer from much wheel recession).

To explain properly, having a RA down low OR up top has no influence on how it will 'hit' obstacles. A radius arm effectively is a fixed link - off the diff, it can be any shape BUT the distance and position of the 'mount' or pivot point is the deciding factor. The RA could be any shape and mounted to the diff in any position, but it will still swing in the same arc and from the same point...... EG a panhard has a bend in it! but the resultant force is in a straight line between the 2 mounting points, it has nothing to do with the shape, same goes for a RA. It is fixed at the diff and pivots at the chassis, nothing changes. So apart from clearance i don't see too many benefits. And honestly i don't consider the arms to be a huge loss of clearance, hey nissan guys don't seem to complain, and some cruiser guys think puttin a pissweak GU front end in is the bomb. IMO the 80 front end is pretty freakin awesome.

thanks for the feedback though, i had to think for a change as well

[v840]

Nissan guys don't complain because it's an accepted fact that the GQ front end is sheeit.

Again, I don't think he was saying anything other than "I really enjoy the increased clearance and the favourable angle that my arms now hit objects on".

I agree that flipping the arms will not have any appreciable effect on either anti squat or roll axis but the increased clearance and, in MUD80D's case the reduced angle of the links are advantageous. It's pretty much the entire premise behind running portal hubs, besides the gearing that is.

Also in your example with the panhard rod, I have a question. My understanding is that the resultant forces are indeed between the two mounting points on the axle and frame so it is therefore a good idea to run as straight a line as possible between those two points, ie a straight link. I'm sure you know a lot more about this that I do but running a panhard, in say a z-link shape, would be quite a decrease in the links ability to resist those forces wouldn't it?

[Struth]

So are we missing the fact that if the RA is on top of the diff, the RA is presented on a flatter plane. Because of this when travelling forward and hitting an obstacle that requires the diff to move up there will be less forces placed on the RA chassis pivot and in fact all the bushes of the RA.

This is because the diff is not scribing the same arc dicatated by an RA that is mounted below the diff, whereby the diff needs to actually move forward at the same time as raising because of the more obtuse (acute angle really but larger) angle of the RA.

The affect I am talking about is the RAs arc actually increasing the wheelbase of the vehicle by moving the front axles forward at a time when all the drive in the vehicle is against the front axle (or the obstacle) and the last thing the vehicle needs is RA arc forces trying to push the whole of the vehicle, beside the front diff, back away from the obstacle, at the very least this will tend to make RA bushes wear a lot quicker.

Does that make sense?

Or am I missing something


EDIT: yep I am missing the fact that despite the positionj of the RA on the axle a straight line always exists between the RAs chassis mount and the axle centre.

Now if we move the chassis mount of the RA up and down we will start to alter forces experienced by RA bushes

[1MadEngineer]

EDIT: yep I am missing the fact that despite the positionj of the RA on the axle a straight line always exists between the RAs chassis mount and the axle centre.

Now if we move the chassis mount of the RA up and down we will start to alter forces experienced by RA bushes

yep thats what i meant. the induced force is dependant on the position it contacts the tire and the relationship to the pivot point on the chassis. (taking into account the axle centerline as the '3rd' point in the force triangle).
as you can see the size shape and position on the 'link' whatever it may be has little effect on the 'change' in chassis dynamics.

the 'swung' arc is always going to be the same IF the mounting position is the same on the chassis end. FWIW extending an arm ~10-15mm is going to do F### all to the overall dynamics. A well designed drop arm has an amount if distance correction already added to them.

[1MadEngineer]

I agree that flipping the arms will not have any appreciable effect on either anti squat or roll axis but the increased clearance and, in MUD80D's case the reduced angle of the links are advantageous. It's pretty much the entire premise behind running portal hubs, besides the gearing that is.

i hear ya - you are preaching to the converted, we have shaved the guts out of every diff we run in our comp trucks, we even run the new trailgear rock assault housing in the rear, as the clearance on the diff tubes is an added bonus. We also cut and rotate knucles to kick the pinion nose up, which helps in shaving the housing even more, as the flange area is higher up

Also in your example with the panhard rod, I have a question. My understanding is that the resultant forces are indeed between the two mounting points on the axle and frame so it is therefore a good idea to run as straight a line as possible between those two points, ie a straight link. I'm sure you know a lot more about this that I do but running a panhard, in say a z-link shape, would be quite a decrease in the links ability to resist those forces wouldn't it?

very true - example only!! the idea is that if you have to run a link/RA to miss something then make sure it can handle induced loads. When i designed the nissan RA i did my fair share of FEA analysis to make sure they were right (unlike other manufacturers )

[bj on roids]

before i done the arm flip i was bending the arm with an 7.5"lift the arm sat at about the 45 deg angle so when you hit a log or rock in comp or winching instead of the diff moving up it wanted to go back because of the angle of the arms using my cruiser in comps i was bending the arms each event and was a pain in the ass so now putting the arms on top of the diff they become level as if they were back to standard and since the arms have been on top NO arms have been bent last year i competed in the toperi challenge and powering up a hill and hit a large rock if the arms were on the bottom i would have bent them good but now there on the top no problems even thow i hit this rock thet hard running 38.5"tires and broke my Longfield axel (not the CV) from the tire hitting a 3 foot step but with my arms on top i had to raise the panhard rod any way to suit my high steer.

Yeah another good point I missed, raising the mounting point relative to the link and chassis will create a flatter link resulting in more controlled suspension, and reduce the inevitable pig rootin bunny hoppin that is common on lifted cars with stock suspension.

[bj on roids]

before i done the arm flip i was bending the arm with an 7.5"lift the arm sat at about the 45 deg angle so when you hit a log or rock in comp or winching instead of the diff moving up it wanted to go back because of the angle of the arms using my cruiser in comps i was bending the arms each event and was a pain in the ass so now putting the arms on top of the diff they become level as if they were back to standard and since the arms have been on top NO arms have been bent last year i competed in the toperi challenge and powering up a hill and hit a large rock if the arms were on the bottom i would have bent them good but now there on the top no problems even thow i hit this rock thet hard running 38.5"tires and broke my Longfield axel (not the CV) from the tire hitting a 3 foot step but with my arms on top i had to raise the panhard rod any way to suit my high steer.

sorry, but i don't get this? I do understand the bending bit, big lifts induce more of a bending force into the resultant which causes the arm to bend/twist in the wristed area (common problem in any radius arm coupled with a big lift). the bit i don't get is the anti-squat change???? it can't change, if all the mounting/pivot points are still in the same spot! In a RadArm setup AS is a function of contact patch - diff axle CL - mounting point on chassis. The only way to change AS on a radius arm (same tire dia) is to change the pivot point position on the chassis!!! changing the mounting on the diff will make no difference at all. EG: use the 3-link calculator on pirate and have a play. The only thing you will find is that it adjusts the RollAxis somewhat but that is more to do with articulation and handling.
as for the arms bending, once you go for a GOOD after market radius arm then thst should fix the problem.

Sorry for all the Q's but i am trying to learn more about cruisers and what is needed to make them better, and also peoples perceptions of what is the best way to go....

By putting the arms on top you do change the mounting points!

[bj on roids]

Nissan guys don't complain because it's an accepted fact that the GQ front end is sheeit.

Again, I don't think he was saying anything other than "I really enjoy the increased clearance and the favourable angle that my arms now hit objects on".

I agree that flipping the arms will not have any appreciable effect on either anti squat or roll axis but the increased clearance and, in MUD80D's case the reduced angle of the links are advantageous. It's pretty much the entire premise behind running portal hubs, besides the gearing that is.

I beleive it would affect anti-squat.

[lukethedork]

Nissan guys don't complain because it's an accepted fact that the GQ front end is sheeit.

Again, I don't think he was saying anything other than "I really enjoy the increased clearance and the favourable angle that my arms now hit objects on".

I agree that flipping the arms will not have any appreciable effect on either anti squat or roll axis but the increased clearance and, in MUD80D's case the reduced angle of the links are advantageous. It's pretty much the entire premise behind running portal hubs, besides the gearing that is.

I beleive it would affect anti-squat.

HAHA, go back to the first page... Your saying exactly what I was saying.
Go to the 4 link calculator and make a radius arm suspension similar to the land cruisers, and you will see that what 1madengineer is saying is indeed correct.

[Struth]

So can we agree on the advantages of flipped RAs?

1 Better clearance
2 ?
3?
4?

[dow50r]

2. keep your toyota all toyota

[MUD80D]

2. keep your toyota all toyota

now your talking

[Struth]

2. keep your toyota all toyota

now your talking

Good point, I know pootrol diffs are tough but my 60s diffs look pretty bloody hard to bust too

[65Mog]

It's not my 80, but here are a few more pictures. This was done a long time ago now, years before anyone was making castor corrected arms. I still think this is the better option, it might say it doesn't work on the computer screen, but in the real world having seen first hand the improvement this makes both on and off road I still say this is the better option.

[80's_delirious]

A few more pictures. This was done a long time ago now, years before anyone was making castor corrected arms. I still think this is the better option, it might say it doesn't work on the computer screen, but in the real world having seen first hand the improvement this makes both on and off road I'd say this is the better option.

some tidy looking work there who did the high steer?

[65Mog]

John MacDonald (J Mac Diff & Gear)

[tozook]

It's not my 80, but here are a few more pictures. This was done a long time ago now, years before anyone was making castor corrected arms. I still think this is the better option, it might say it doesn't work on the computer screen, but in the real world having seen first hand the improvement this makes both on and off road I still say this is the better option.

is this 80 series the red single cab?

[bj on roids]

So can we agree on the advantages of flipped RAs?

1 Better clearance
2 ?
3?
4?

Additional leverage on the arms would give a tiny bit more flex.


If you are doing the flipped arm, then as 1madengineer said, the shaved housing is also good.

[Struth]

So can we agree on the advantages of flipped RAs?

1 Better clearance
2 ?
3?
4?

Additional leverage on the arms would give a tiny bit more flex.


If you are doing the flipped arm, then as 1madengineer said, the shaved housing is also good.

Yes I will be shaving both housings, this thread has convinced me that flipping the arms is a good idea, more so for clearence than anything else.

Cheers

[Struth]

It's not my 80, but here are a few more pictures. This was done a long time ago now, years before anyone was making castor corrected arms. I still think this is the better option, it might say it doesn't work on the computer screen, but in the real world having seen first hand the improvement this makes both on and off road I still say this is the better option.

What would you say is the improvement in the real world?

Cheers

[pinkfloyddsotm]

forgive my ignorance but whats a "shaved housing "?

[Struth]

forgive my ignorance but whats a "shaved housing "?

Its where you cut the bottom of the diff housing off flat and reweld a flat plate on to seal it again.

It removes excess diff pumpkin and increases clearence at the diff. Not great gains in clearence but every little bit helps.

Cheers

[crankycruiser]

2: u can get more castor, as the steering arms dont hit the RA's..

[g35me]

It's not my 80, but here are a few more pictures. This was done a long time ago now, years before anyone was making castor corrected arms. I still think this is the better option, it might say it doesn't work on the computer screen, but in the real world having seen first hand the improvement this makes both on and off road I still say this is the better option.

Finally some decent photos of this mod. Some awesome work there.

[g35me]

A few more pictures. This was done a long time ago now, years before anyone was making castor corrected arms. I still think this is the better option, it might say it doesn't work on the computer screen, but in the real world having seen first hand the improvement this makes both on and off road I'd say this is the better option.

some tidy looking work there who did the high steer?

Hey Cranky isnt this the same hi steer that you have? and did I read a while ago that Jmac wont sell it unless they install it themselves?

[crankycruiser]

yer mate.. i have a j mac one as well.. the arm on mine is slightly higher but basically the same.. last time i talked to John, he wasnt selling them unless he actually installed them.. but thats not to say that things havent changed...

[g35me]

yer mate.. i have a j mac one as well.. the arm on mine is slightly higher but basically the same.. last time i talked to John, he wasnt selling them unless he actually installed them.. but thats not to say that things havent changed...

It looks like a 10min install, did he give you any reason?