Adjustable Radius Arms

[toughnut]

So here is one for the engineers on here.

I haven't drawn this up so bear with me while I try and explain. What I'm thinking is building a 3 peice radius arm that allows you to adjust the castor.

So my basic idea is to have a small cradle piece on the diff. Just like the section of a normal radius arm that cradles the diff with an extra mounting point like the flex arm cradle from superior. Then have a non-adjustable link from the chassis mounting point to the upper bush and then an adjustable link from just near the chassis mounting point to a point at the lower rear of the diff cradle.

I know that clearance for the tie rod would be needed to take into account and strength would be another one. The lower link would not need bushes. It could be a solid mount so you would effectively get the same characteristics as a normal radius arm but you could adjust castor.

What do you guys think?

[want33s]

You mean like this?

[rockcrawler31]

Wouldn't it be simpler to eliminate a link by making it two piece? Single arm going to front axle mount under axle (or over if you want clearance) and an adjustable link to the rear most? Alternatively why don't you consider a clockable splined offset bush in a one piece arm? Make a ring that the bush presses into as per normal with a coarse spline on the outside, then corresponding broached ring that is welded into the arm. Just pull the arm, clock the splined ring (and with it the offset bush).

By using 80 series front bush separation values, only a couple of mm of bush offset would give a fair bit of castor adjustment when flipped upside down.

Or you could just multi link with adjustable arms

[rockcrawler31]

You mean like this?

I was going to suggest that, but it's wayyyyyy to simple for Steve. He likes to over complicate things

[brooksy]

So something similar to an adjustable Y link on Jeeps but opposite adjustable arm.
Biggest issue would be getting a fine enough adjustment. A cam solid bush at the point where lower arm meets upper would be a solution ??



brooksy

[brooksy]

Lol, I was a bit slow to post


brooksy

[SWBMQCraig]

Would it perhaps be easier to make one (or both) diff mounts adjustable a bit (maybe bolt on with shims) then you could use off the shelf arms and still have a few degrees of adjustment for your castor? how much adjustment do you want?

[80's_delirious]

You mean like this?

I was going to suggest that, but it's wayyyyyy to simple for Steve. He likes to over complicate things

Steve should search on Ih8mud.com then.

A member in the USA made 80series radius arms with over-sized adjustable front radius arm bush inserts. Definitely over thought and over complicated.

[uninformed]

if you need to adjust castor due to lift etc, and your doing it at the axle housing, what is happening to the pinion angle? How about adjust the castor at the swivel......

[toughnut]

if you need to adjust castor due to lift etc, and your doing it at the axle housing, what is happening to the pinion angle? How about adjust the castor at the swivel......

That can easily be done by machining off the swivels and then re-welding them. But the picture above is pretty much with I was thinking and I'm wondering why it isn't done much more than it is now. It obvioulsy works. That way you could change the geometry of your suspension and have the ideal castor each time without having to swap them for other arms each time. That way you could compete in different events and raise or lower your truck to suit the comp or stage.

As for pinion angle. Well it is only a few degrees. Not really an issue for the changes that I'm thinking of.

That pic up there explains what I was thinking really well.

[TheBigBoy]

if you need to adjust castor due to lift etc, and your doing it at the axle housing, what is happening to the pinion angle? How about adjust the castor at the swivel......

Na, lifting your suspension with radius arms takes the pinion out of parallel angles to output shaft. Correcting caster back to +3 degrees at housing corrects this angle back to parrallel and stock.

Cutting and turning your swivel keeps the pinion out of parrallel and will vibrate and cause premature wear of uni's.

[uninformed]

more than one way to skin a cat..... what if your pinion wasnt parrallel from factory and they ran the propshaft out of phase. Also what if you had alxe flanges that allowed to bolt the swivel ball onto the hosuing....you could slot those holes and have castor adjustment there.

The picture of the 2 arm radius is very common in the USA.

[SIM79]

Why isn't that setup pictured above popular over here?

[80's_delirious]

Why isn't that setup pictured above popular over here?

Where the adjusting link joins to the main link is a weak point, I've seen pics if the lower arm bent at the point of connection.

Maybe a fabricated arm or some long gussets would solve that?

[TheBigBoy]

Plus they drive like crap. Very swirly at highway speeds. It's basically the old bolt on 5 link in the y configuration.

[uninformed]

do they drive like crap becasuse they are only double mounted on one side.....how would a toy or nissan drive if you removed on of the bolts from one RA at axle end??? may be ok with double mount on both sides....yes it wont have the flex of the 3 bush set up, but will have the adjustability of castor. And yes where that little arm mounts on the main long arm would be quite the stress area.

[TheBigBoy]

They handle like crap because the bush's are verticle. You need it either side to control axle wrap under braking. Anyone who has removed the bolt on 1 side wll tell you is bloody dangerous on road. Huge dives into corners and even under straight braking that side dives down also, but bloody smooth and hardly felt the sqaure gutter... . Off road it doesnt matter as much if you slow and controlled. The bottom line to 3/4/5/ link etc is the more verticle the shorter the distance between the bush's - the worse it handles. You need the correct seperation and some binding for it to handle well onroad. As most people are finding 45 degrees it starts to come good and still retain good flex. The more angle the better onroad. Thats why I spent ages playing with RA set ups and trial and error until I dialed it all in.

[toughnut]

I would definitely have them on both sides and my idea was to have the adjustable link extend from right up near the chassis mount to minimise stress and it would also minimise stress transfer to the rigid member. Also all the linkages would be solid mounts apart from the original rubber bushes. So it should drive very similar to normal radius arms and if you wanted a little more flex then you could replace one of the adjustable link mounts with another rubber bush. This could be done easily with a bush end to screw into the adjustable link rather than the solid mount.

The main reason I am thinking about this is to give me adjustability rather than extra flex. But the extra flex can be built in if desired. I really am surprised this hasn't been done more. I can't wait until my next break to give this a go.

[TheBigBoy]

First of all. What truck are you doing this too?

Your wanting to run a upper and lower link from the same chassi mount, most for caster adjustability. Why don't you just make those arms parallel and build a 5 link. It will be correct cast no matter what the lift?

[80's_delirious]

You've got me thinking Steve it looks like it could have great potential with some thought.


You could improve clearance, improve flex, have adjustability, have flexibility in terms of packaging it all, build in bush spacing similar to superflex arms for best of handling and flex characteristics.

[TheBigBoy]

You've got me thinking Steve it looks like it could have great potential with some thought.


You could improve clearance, improve flex, have adjustability, have flexibility in terms of packaging it all, build in bush spacing similar to superflex arms for best of handling and flex characteristics.

If your talking about your 80. You know what would be better! Flipped arms with adjustable front bush mounts (via 2 big bolts, 1 either side of the front bush). I designed already when I was doing mine. But it's really not practical. That's the best handling out of all of them. With added flex.

[toughnut]

But by doing the flipped arms you have a lot of fab work to do to the diff. Same same for the 5 link set up. I'm talking about something you can bolt on and give you great adjustability and as Dave said, the flexibility for packaging. With a bit of though I think this could be a very good alternative that will cater for a number of different applications. It is something that is very simple in application and the design would be relitively simple as well. It would be 3 pieces. A diff cradle and then 2 links. One adjustable link that mounts to the solid link and the diff cradle which is what would give you the adjustability and flexibility that I'm looking for.

This is something I am going to explore more. I am fully aware of the alternatives but I would like to explore this more and see if it can be made to work and to either prove or disprove my theory. As far as strength goes I think it would be just as strong and stable as any current aftermarket arms. The beauty of this is that you would have castor adjustment and flex style arms all in the same package and you can swap between full stability or having the extra flex with just a couple of tools and a few minutes.

[uninformed]

if we are refering to the picture in this thread, I dont think it maters as much that the bushes are vertical, but rather #1 there are only 3 bushes at axle end, all up, and #2 the bush spacing on the double arm AND their distance from the axle centerline.....You sort of answered that with your removing the bolt comment on handling

[toughnut]

if we are refering to the picture in this thread, I dont think it maters as much that the bushes are vertical, but rather #1 there are only 3 bushes at axle end, all up, and #2 the bush spacing on the double arm AND their distance from the axle centerline.....You sort of answered that with your removing the bolt comment on handling

This would be aleviated if you had a solid mount on the adjustable arm. The picture in my head is basically that arm flipped and much stronger. That picture is not the final picture I have but it is a very basic indication of what I am trying to describe.

If you had a solid mount on the adjustable arm then that would effectively be as if there was no mount and the only flex you would get would be from the 2 original bushes on the diff mounting. It should give you the same characteristics that you'd get from a normal radius arm.

[80's_delirious]

My 80's long gone :-( I'm beating up a 105series now

I agree with Steve, for the amount of fab work involved for flip arm, the std arms can be improved on, with little extra fab.

I would look at longer arms too, and triangulating the arms too.

As for bush spacing and handling, the lower front bush could be positioned behind the axle tube to maximise clearance, and the front bush positioned above and forward of the axle tube centre line to give some horizontal separation to control axle wrap, part way between flipped arms and superflex arms.
If there is room, I see no reason not to have the smaller link on both sides so you have four points of connection on the diff housing for better control of axle wrap under braking etc

[toughnut]

yeah. The idea is to run two of these arms to replace both arms and not have to do any fab to the vehicle at all. Its just an idea that I want to have a go at making and see what happens. Hopefully I can come up with something a little different that works and not just wrap my front axle under my truck. haha

[TheBigBoy]

My 80's long gone :-( I'm beating up a 105series now

I agree with Steve, for the amount of fab work involved for flip arm, the std arms can be improved on, with little extra fab.

I would look at longer arms too, and triangulating the arms too.

As for bush spacing and handling, the lower front bush could be positioned behind the axle tube to maximise clearance, and the front bush positioned above and forward of the axle tube centre line to give some horizontal separation to control axle wrap, part way between flipped arms and superflex arms.
If there is room, I see no reason not to have the smaller link on both sides so you have four points of connection on the diff housing for better control of axle wrap under braking etc

I dont get it. You say flipped is too much work. Then talk about longer arms and triangulated? = housing welding, chassi mount relocation etc etc.

I know what your trying to get at toughnut. And alot of people have also tried it, but there is a reason why not many do it (if its a road use truck).

Y link (both sides not that that dumb first picture ) .


Some what attempt at uneqaul 5 link (nowhere near enough seperation to handle axle wrap)


Cross between 5 link and radius arm (like the old wizard performance bolt in 5 link)


Radius arm with threaded bung/heim to adjust caster. And laser cut bolt on brackets


This is basically the decissions you have to make.

Red is stock. Blue is max flex but handles terribly. Orange is where you start to regain road manners.

[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.

[toughnut]

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.

[TheBigBoy]

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.