Adjustable Radius Arms

[brooksy]

Personally I would steer clear of having adjustable arm on the bottom. The lower needs to be solid to eliminate weak points. I had thought while designing my RA's to have the upper adjustable with a threaded shank bushing or JJoint. This was to be done with the same layout I have designed (arms on Shortmans Winch Lux), but to eliminate having to run thicker plate for RA's have a welded in 1/2" wall tube section threaded to take either bush or JJoint. Easy to swap to allow for more flex or better high speed handling & adjustable castor all wrapped into one.
Obviously I couldn't as Mick didn't want another issue to get rego'd. But lucky me, I had 2 sets cut at the same time so possible to do on my 40.




brooksy

[TheBigBoy]

I had a reply made out before it all crashed.

The idea of this is to run two arms as a direct replacement for the factory arms and like I've said, its not to change the characteristics of the suspension but to make an easily adjustable radius arm so you can use the same arm for different applications. And with a simple swap of a hard mount for a rubber mount you can dial in extra flex.

The basic idea is to have a 'diff cradle' that bolts to the existing diff mounts with a third mounting point at the lower rear and then have a solid arm from the chassis to the upper rear diff mount made with say 50 x 25mm plate and then a lower link that is adjustable that runs from near the chassis mount to the third mounting point on the 'diff cradle. This would provide the adjustment and for the most part would be solid mounted unless you are trying to get extra flex then you could change out one of the solid mounting points on the adjustable link with rubber and if this is still not enough flex then you could do this for both sides. You could even go as far as changing the solid mounts at both ends of these adjustable links and get much more flex but you would obviously lose a lot of stability and would not be used for the road.

If the basic setup can be done properly then this would be a very good setup and would provide people with a whole lot of flexibility in its application.

Here is a very basic pic of what I'm thinking about. I'm not too good at modelling programs. So if someone wants to draw it up properly then feel free.

What your missing in your idea of them being like superflex arms though. Is the fact that the verticle bush's are only on 1 side. If it was the same both sides it would be all over the place. Whether its a cradle, bolt on bracket or welded brackets. Makes no difference. It's the single side normal radius arm that gives the superflex it's stability.

[80's_delirious]

I didn't say flipped arms are too much work. I think for the work involved, I'd be looking to maximise the gains made. Flipped alone has minimal gains.

With what Steve is talking about, you could configure bush placement within the orange/red range on your diagram, still gain flex, still gain clearance, still have road manners, still have flexible packaging, still have dial-able caster.

Flipped alone has much more than minimal gains... But cant change caster once set.

[80's_delirious]

Steve, the lower adjustable link in your sketch looks like a weak point. If you drop your rig on a rock into that link, It's gonna cop a beating, bending it will bugger up your adjustment.

[TheBigBoy]

It's only a can of worms to those that have not done it. Look at my results...

[uninformed]

if you have 2 radius arms, both with the same bush seperation, both with the same bush distance from axle centerline, the only difference: is one the bushes are pretty much front and back of housing, the other the bushes pretty much top and bottom of housing, how does this bush placement dramaticly change the handling characteristics from super flex, crap on road to super stiff great on road...

[TheBigBoy]

if you have 2 radius arms, both with the same bush seperation, both with the same bush distance from axle centerline, the only difference: is one the bushes are pretty much front and back of housing, the other the bushes pretty much top and bottom of housing, how does this bush placement dramaticly change the handling characteristics from super flex, crap on road to super stiff great on road...

Think about it... This pic should help. http://superiorengineering.com.au/index.php?pag_id=24" onclick="window.open(this.href);return false;

There is far less binding when above and below. So much so that handling suffers. When front and back of the housing and under articulation the arms front bushes are appossing angles and bind much earlier. Less travel but much better onroad due to the early point of binding.

[TheBigBoy]

From everything Ive learn by actually doing all of this including 5 link. You need some binding for on road predictable handling. Flipping the arms and changing a few things via trail and error has seen the best of both worlds. So if you think flipping does minimal. Youve never done it. Flipped with adjustable caster would be AWSOME...

[toughnut]

What your missing in your idea of them being like superflex arms though. Is the fact that the verticle bush's are only on 1 side. If it was the same both sides it would be all over the place. Whether its a cradle, bolt on bracket or welded brackets. Makes no difference. It's the single side normal radius arm that gives the superflex it's stability.

But if you have actually read my posts you would see that the adjustable link (whether on the top or the bottom) has solid mountings. I.E. it does not have any bushes where it connects. So it should not change the characteristics of the radius arm. BUT. If you change just one or both of those solid mountings for a rubber bush then you would start to change the characteristics dramatically. Having the third mounting point at the diff will not change anything if it is a solid mount as the radius arm will effectively be a solid item and only flex at the normal diff mounting points just like the factory arms.

Please read my posts correctly before you comment.

[TheBigBoy]

I read it. I understood it a bit better with your picture. But even without a bush you will need a pivot point (bolt) and if that will wear steel on steel. Any play at all will affect driving characteristics. It's just advice. By all means give it a go.

[uninformed]

if you have 2 radius arms, both with the same bush seperation, both with the same bush distance from axle centerline, the only difference: is one the bushes are pretty much front and back of housing, the other the bushes pretty much top and bottom of housing, how does this bush placement dramaticly change the handling characteristics from super flex, crap on road to super stiff great on road...

Think about it... This pic should help. http://superiorengineering.com.au/index.php?pag_id=24" onclick="window.open(this.href);return false;

There is far less binding when above and below. So much so that handling suffers. When front and back of the housing and under articulation the arms front bushes are appossing angles and bind much earlier. Less travel but much better onroad due to the early point of binding.

im not seeing it yet??? Yes I see the superflex picture, but there bushes are closer together than the other example......what I picture on a stock rig, is that when the right RA goes up and the left RA goes down, the cupping effect of the axle ends of RA are twisting in opposite direction to each other.....Im still not seeing a difference if the bushes are vertical or horizontal, given same bush size, speration and relation to axle centerline???

help

[TheBigBoy]

And think real life affects aswell. There is far less binding with them vert. Also means alot of wondering and bumpsteer though. You want a happy medium between bind and flex. Hence the first pic orange, red etc.

Best thing you can do is build a full size moch up to scale with a housing and check it all for yourself.

[toughnut]

yeah. The greater the angle and the greater the distance between bushes the greater the binding will be. If you move the bushes closer together you will get less leverage and your axle will be able to twist easier hence better flex but less stablility. Moving the mounting points to a vertical plane rather than horizontal also has some affect on this as it changes the way the axle reacts in relation to the chassis mounting point. I.E. it changes the angle of the forces that the diff has on the radius arm.

However if the angle and distance between the two diff mounting points is the same as factory then you will only see the difference that the new angle of forces on the radius arm create but you won't see much difference in flex.

[TheBigBoy]

However if the angle and distance between the two diff mounting points is the same as factory then you will only see the difference that the new angle of forces on the radius arm create but you won't see much difference in flex.

Yes you will. Your not thinking real life rather than paper. There is a fixed point of the radius arm at the chassi that doesnt move. Youll find that with a factory arm and possition its the bush furtherest away from the chassi that binds the easiest and restricts travel. The inside bush never reaches its full potensial. How ever, virtical the bushes do reach their full potensial (both of them). You dont need much extra movement in the bush to see great flex gains.

With the superflex arm, the 1 side is vert with them closer together. But the upper is a smaller bush aswell. That smaller bush with the factory style arm on the driverside is what gives it its road handling abilities.

The best thing to do is a full scale moch up and test it. If happy, chuck it on your truck and then test it in every way, especially thoroughly for road mannerisms.

Arhh cant spell today.. Wheres my beer

[Guy]

I would have thought that bumpsteer etc would be more a function of geometry between the draglink and panhard as opposed to the RA's.

If the roll stiffness is not enough you need to add something to increase it .. IE a swaybar. There are manufacturers out there that are running 4 link + panhard front ended and radius armed front ends with the bushes vertical ( Current model F trucks ) with acceptable handling.

[TheBigBoy]

Even with the heaviest sway bar/air bags its not enough. Overkill and every other company who fabricated 5 links for landcruiser 80/105, calbah for nissan etc. Have all ditched it. There is no way to counter the forces involved. The other point that rang home was when Greg mentioned about feed back to the driver in a post long ago when superflex where being developed (100% on the money).

Your right about the bumpsteer with drag link/panhard in a normal set up. But the bush geometry change magnify's this affect and it loves to wonder with bumps and grooves in the road. Ive built a parallel 5 link, uneqaul 5 link, touched on the 3 link and A frame but didnt go through with it, custom bolt on radius arms as pictured (with adjustable top bush for caster. Larger size brackets allowed me to unscrew the heims out further and just re drill the holes in the brackets while maintaining correct caster - How I noticed better drivability and my results in the picture). Had superflex arms, then flipped stock control arms. Can only give my opinion on all of the above. If its not an everyday driver or for road use, any of them will do. The hardest part is finding the happy medium.

[TheBigBoy]

There are tonnes of problems with the f trucks and dodge etc. Death wobbles from factory and people spending big $$ to try and fix the problems. Alot of them are blaming the tierod ends on the drag link. But its the wobble itself thats flogged them out and not the cause of the problem.

http://www.youtube.com/watch?v=6LaMXupbfdA" onclick="window.open(this.href);return false;
http://www.youtube.com/watch?v=8EuQ6f8rgT4" onclick="window.open(this.href);return false;

[uninformed]

bump steer can also be a byproduct of the axle roll axis angle....IE if your RA are higher at chassis than at axle, like most lifted vehicles, then your axle roll axis is in oversteer. When you go over a bump with one wheel, it travels up, because the RA scribes an arc, pivoting from the chassis, it actually travels forward on the side that goes up. Now looking from above the wheel that has travel up is now further forward than the other side, this creates a steering axle.

[80's_delirious]

May not be entirely relevant to Steve's ideas, but this looks like a good compromise between flex and handling, all tucked up high.
For adjustment, the top section could be done with tube and rod ends.






From shortmans members thread, Brooksy's work.

[brooksy]

Yep that's it, I have another set of arms cut that I was contemplating on doing as I mentioned earlier. Weld in 1/2" wall tube where upper bush placement is & run a threaded JJoint.


brooksy

[TheBigBoy]

Still, adjusting caster wouldn't be as you might think. After you have changed your coils and shocks/maybe even bumpstops depending on the event. You'd have to remove both chassi bolts holding the arms in. Unwind the top bush and count the turns after you've previously dialed in the caster for both heights. Sounds all too hard.

[brooksy]

Not when competing its not. There are a LOT worse things to be doing in the pits believe me !!!


brooksy

[MikeH]

Looking at 80's delirious's pics....
cut the top leg off.
Plate either side near where it is cut to provide tabs. (plate it all the way forward from the cut-off part to strengthen the lower section which will be under a lot of stress.
tube link to the diff with left and right threaded heims.

....or am I missing the point?

here's my problem... the chassis gets in the way.
I'm all about drivability and travel for this car, dont care about flex. low COG for high speed cornering. drivetrain has been pushed back and so has the cab. I need to keep the chassis complete when viewed from the side.

[Guy]

There are tonnes of problems with the f trucks and dodge etc. Death wobbles from factory and people spending big $$ to try and fix the problems. Alot of them are blaming the tierod ends on the drag link. But its the wobble itself thats flogged them out and not the cause of the problem.

http://www.youtube.com/watch?v=6LaMXupbfdA" onclick="window.open(this.href);return false;
http://www.youtube.com/watch?v=8EuQ6f8rgT4" onclick="window.open(this.href);return false;

GU's with Radius arms do it as well. I have seen it on Suzuki Sierra's with leaf springs as well ( look up suzuki death wobble or GU death wobble ) .. it is a fault of geometry overall, not link type.

[80's_delirious]

Looking at 80's delirious's pics....
cut the top leg off.
Plate either side near where it is cut to provide tabs. (plate it all the way forward from the cut-off part to strengthen the lower section which will be under a lot of stress.
tube link to the diff with left and right threaded heims.

....or am I missing the point?

here's my problem... the chassis gets in the way.
I'm all about drivability and travel for this car, dont care about flex. low COG for high speed cornering. drivetrain has been pushed back and so has the cab. I need to keep the chassis complete when viewed from the side.

I wish I could take credit for Brooksy's awesome work

Can you move radius arms inward and mount inside of the chassis rails. Having radius arms spaced closer together will reduce roll resistance, improve flex and reduce binding

[MikeH]

On second thoughts its not so bad looking at this angle. they can swing up beside the chassis, I need to do a full size mockup and swing it around.

I wonder how I'd go making an extension bar for a standard arm. Should be strong enough for some basic testing.

You haven't experienced death wobbles until your radius arm falls off the diff at 120kph. Scared the crap out of me and was lucky to get it to stop.

[TheBigBoy]

Looking at 80's delirious's pics....
cut the top leg off.
Plate either side near where it is cut to provide tabs. (plate it all the way forward from the cut-off part to strengthen the lower section which will be under a lot of stress.
tube link to the diff with left and right threaded heims.

....or am I missing the point?

here's my problem... the chassis gets in the way.
I'm all about drivability and travel for this car, dont care about flex. low COG for high speed cornering. drivetrain has been pushed back and so has the cab. I need to keep the chassis complete when viewed from the side.

I wish I could take credit for Brooksy's awesome work

Can you move radius arms inward and mount inside of the chassis rails. Having radius arms spaced closer together will reduce roll resistance, improve flex and reduce binding

We've been through that. It wont give you the outcome you think it will. Getting longer arms would make more of a difference (300mm). It works the same as moving your radius arm bushes closer together (on each arm), but with no ill affects. If you are going to invert the bushes closer together, it makes more of a difference to do it at the diff end.

[MikeH]

what' the limit on how much longer is too long disregarding unsprung weight, ramp-over and tailshaft plunge? the centre of the wheelbase?

[TheBigBoy]

Im pretty sure its the bisalloy itself. In regards to strength of the arm itself. An engineer will tell you.

[80's_delirious]

what' the limit on how much longer is too long disregarding unsprung weight, ramp-over and tailshaft plunge? the centre of the wheelbase?

Have a look at rockcrawler31's members thread, he used custom arms 300mm over stock 80series length with great results.