any improvement to front-end travel if i were to replace my rubber bushing mounts on the radius arms to some big-azz HEIM joints?

a 3-link just really isn't in the cards despite my wishes, although i'd like to learn how to go about designing one for me-self.

i'd post a pic of the 'ol range but guess i'm not allowed to??


cheers w/ :beer: :beer: 's

isaac / searover


p.s. Jeff - u out there buddy? how ya liking the sunshine state?

no

mmmm, what he said.

You see for the front to articulate the front radius arm bushes need to be flexible and soft. A heim joint is very solid and it would lock the front end solid. Flex the front end and get underneith your rig and see what happens to the radius arm bushes.

If you want to design a 3 link then first have a look at the stock setup and understand how it works and why it limits travel and also why using heim joints would be even worse. Then have a look at the hinged arm setup and undestand why it frees up the front flex and what problems the hinge creates.

Once you work all this out then you will be well on your way to being able to look at desiging a three link and all the complexities and compromises involved. Cause it aint easy and it definately aint rocket science. Esp is you want to drive the thing on the road and have it behave itself.

Sam

Heim joints in place of the front bushing would lead to no flex up front, and I predict that a single day of hard core off-road stuff would tear the mounts off the axles. There just wouldn't be any give in the system and all of the stress would be concentrated at the mounts. I have seen one of our people try something similar in the rear. With this set-up, the axle acts like an ATV axle. Moves up and down but does not articulate. He tore the mounts off toward the end of the test run on Tobasco Twister. He had on-board welding, so he was able to limp home.

The stock front set-up is strong. Several years ago I did a finite element analysis of the arms and found that they had a safety factor of over 4 in a 1-g stop with all of the weight on the front axle. Recently, Sam did some back of the envolope calculations and found the same thing.

Rich

ahh - i was mistaken in thinking that the heim joint would allow more vertical travel of the arm than the bush

i understand that when articulating on a radius arm configuration, the radius arm is enduring enormous stress just aft of the axle, which is why the modified arms are often referred to as "wrists".

I thought that freeing up the frame-side joint might allow for just a tad more articulation, but from what you guys are saying here it's bound up enough on the stock arms to not make a difference really.

i think it was one of you on this bb that passed on a tip to use front shocks for a land cruiser application - i'll probably go that route and forget about it.

at any rate, I need to sharpen up my driving skill before spending a whole bunch of money on my rig anyways. i was just looking for some simple and (relatively) inexpensive things to do for this summer's exploits. maybe next year i can look at a 3-link configuration more.


cheers,

isaac

You didn't say if you have longer springs or not. RS9014's are a direct replacement and are 3-4" longer than stock depending on whose measurements you believe.

By using brackets or a discoII shock tower, u can use just about any shock you want.

jk:grinpimp:

issac,

Good idea. Don't get too carried away on 3 link vs. stock until you get deeper into the sport. Lockers make way more difference than anything else you can do to your rig. (Of course you should cover it with rock protection first if you care about the body). I have run 8.5" shocks on all 4 corners since I bought the rig, and can do the same obsticles as those with more $ in their suspension. Sometimes it is a little harder, sometimes it is a little easier.

However, if you don't have lockers, suspension travel makes a big difference - up to a point.

Rich

I have done what you are asking about for pure curiosity.Lenghtened the arms 12" and heim jointed at the rear frame mount which was re-located 12" to the rear.The articulation gained was negligible. That really made me understand the true nature of the problem.

You won't get more flex unless you make the arms a lot longer and move them back like Ben Tanner did on his D-90. Of course, his stock radius mount was torn off in an unfortunate impact.

Don't spend the money/time on this unless you are really driven to.

Also, modified arms are called "wristed" because they are hinged just aft of the axle to move up and down like a wrist. I have one of these on my D-90 and absolutely love it. With Old Man Emu shocks and springs, simply unpinning the arm and allowing it to hinge put 11 more inches on my travel up a 20 degree ramp. Worked out to something like a 15% increase in travel. I'm still awaiting some ramp time to test its effect with the new RoverTym suspension.

They are relatively cheap, very easy to install, and do provide a nice comprosmise between articulation and road manners. Unless you need the insane flex of a 3-link up front, I don't know why anyone wouldn't want a hinged arm, save for the fact that they cost money (or parts/time if you build your own).

--Matt

My Rangie Has had the Radius arms replaced with two custom Arms per side that mount higher than the standard Radius arms with Adjustable bushings to allow for Caster Adjustment.
The setup works very well.

I'll post some pics soon.





:beer: :flipoff2:

if you hiem the rear joints and lengthen the arms there are signficant gains in front flex, but it is all relative. The front of a land rover doesn't really flex all that well in stock configuration (using radius arms) but it can be made to flex decently with longer arms and hiems. I know there are several people on this board that seem to think that lengthened arms don't work but my truck will flex within about 2 inches on a 25 degree ramp of what a truck with a hinged front arm and lengthed hiemed rear joints will. Now granted a three link would probably be able to run about 6-8 inches further up the ramp and maybe even a little further but the on road stability that I still have is completely different than the feeling of a three link on road. Once again you reach the decision of how much off roading you do and how much sacrafice are you willing to make to have your truck perform better offroad. Yes the hiem at the axle end will not work at all but at the frame end with a lenthened arm and also adding a different bottom axle mount I have seen significant gains. But it is a lot of work although surprisingly not much money. Good luck in whatever you try.
-Ben

The MAIN issue about flex using a radius arm design is that as one side of the axle moves down and the other up, the axle centerline "twists" during this movement. If you have the axle pinned via a radius arm design (top and bottom, or fore and aft) at centerline, the axle cannot move as it swings (and *twists*) as it travels in its arc. Basically one side gets shorter as the other gets longer....Hence, rotating the axle along it's centerline. That's why companies like Rubicon Express have a radius arm design that has an Acme threaded upper tube (canted towards the center of the axle/pumpkin) on thier radius arms...This works very well btw.

Longer arms in therory would be better because the swing of the arc is less over a given distance (longer radius)...However the limits of the flex of the bushings will ALWAYS be the limiting factor. Again, that's why a heim joint top and bottom, or side to side of the axle centerline, will ALWAY'S BIND at some point while the axle moves up or down.
This is why some guy's mount thier radius arms on a tube OVER the main tube on the axle such that the axle can "twist" during articulation...These guy's get mucho' flex while still maintaining the benifits, and simplicity, of a radius arm design. It's just a PITA to do right! (Read: *I* haven't figured out a good way to do it yet!)....O'yea, and this would only work with a straight tubed axle of course (D20,30,44,60,70 etc),

--D

makes me want to draft up a free body diagram for the axle ;) (sometimes, freshman physics does come back to haunt you . . . )

first two serious questions before a little brainstorming . . .

a) has anyone measured the min/max free travel of a stock sprung rangie w/o the shock or swaybar attached? and is the correct measurement from hub-center to highest point of the bottom fender lip?

b) what has to be modified to fit the DII shock tower to my '91 RR?

around western washington here i can max out the stock suspension fairly easily, but i will say this: it is very stable, and suprisingly balanced front-to-rear.

also on the hinged arms, it looks like you always end up with a little more travel on the hinged side than the other? what has been your guys' experience? early bronco guys around here luv 'em (or at least the two i've talked to directly)

it seems that ideally you would modify the arm knuckle at the axle tube attachment point. If you could fab an adaptor that would allow a tube-mounted guide to rotate max 20 degrees in either direction and about 2-3 degrees of rotational deflection perpendicular to the guide you could reuse the stock arms without modification, and just move the rear mount back the dimension of the adaptor. kind of like a semi-fixed 6" diameter heim joint, if that makes any sense.

anyways - long travel rancho 5000 - here i come!

may the beers be with you,

isaac

Sounds like complicated way to do a hinged radius arm. Have a look on the d-90 site and have a look at the report on the hinged arm. Its very simple to do if you want to go that way.

Heres the link:

hinged arm tech - d-90 scource (http://www.d-90.com/prod/hinge.html)

I believe with the right front radius arm bushes (the guy here has almost got the mold for them made and should start production soon (maybe) ) the stock setup should be able to use the full travel of a 10in travel shock.

If you got a stock setup and you arnt maxing out your shocks then there is a lot that you can do before you need to start cutting and welding.

Set your front suspension up so that it can use about 9 - 10in travel at the shocks and once you get this then start looking at hinged arms/ three links etc. Have I look at how much front travel you got now. If its a stock late model disco or rangie I would guess that they would only use about 5in travel (this is a guess)

Ten inches is a lot of front travel and it would be enough for most rigs.

Remember suspension travel is not the be all and end all of suspension design. It is all about compromises and the biggest compromise with lots of travel is that your rig wants to fall over in off camber situations (not to mention on road behaviour) If you have 14in front travel believe me your rig will want to fall over real bad compared to how it is now.

Sam

Issac,

I too have a rig that I must use as transportation, not just a trail rig. However, we do allot of overland camping and such, not just day runs. That being said, I went after the best I could afford/justify and spend time on. I too don't like the way that a 3 link feels on the highway, 65 mph curves in the rockies can do that to you... Anyway, as Strange Rover put it, 10 inches should do just about anyone to start with. (ask my w... oh never mind). The DiscoII shock towers are a direct bolt in. But, they cost an awfull lot just to change your shock length. You can get new mounts from AA MFG for $2.00 each, or you can bolt in a rs9014/rs5014 for $0.00 your choice. rs9234's seem to be a good choice with adapters.

Also to Strange Rovers point, bushings have allot to do with the amount of flex in a stock set-up. If you go aftermarket, go as soft as you can. This alone will give you more flex, yet probably improve your on road feel, as your stockers are probably wearing by now.

Don't forget that 10" travel at the springs corresponds to roughly 16" out at the tires under artuculation. This is a lot of travel for a front axle.

Rich