Rear 4 Link

[dilmah]

As most of you know my SAS conversion is almost done. While I intend to enjoy it for a while before taking it off the road again I am going to start planning a 4 link conversion in the rear.

The purpose of this post is to get some ideas on how to do it, I have some rough ideas but want to get some more ideas from other people. It will be a single triangularion of the upper links and straight lower links. Link brackets will come from either Ruff stuff or Ballistic Fabrication in the states. For now I will be using the C200 axle as it is already locked and I dont feel like spending another $1500 on a locker

I intend to use either remote res fox coilovers or fox smoothbore if I put coil springs in it. Getting it engineered is out of the question because of the SAS conversion.

Will initially be used for weekend work, then eventually winch comps and a class 8 offroad race truck once the cage goes in and I can save up enough $$$ for the safety gear.

 

[dilmah]

This is a trail rig in America, It has a 3 link rear with a Panhard rod. The coilover towers are notched into the chassis rails. Im pretty sure it uses a wider axle so I may find something like this hard to do with the narrow C200. Any thoughts???

 

[dilmah]

Or I could do something like twisty has done on a FJ40. I dont have a problem with cutting the tub up but I want to keep some of chassis rails behind the axle

 

[bods]

Was going to suggest that. .. inside the chassis rails, that way if you bin the tub and build a tray instead you can build it around that...

 

[dilmah]

Could also put coils in the rear and make up some sort of integrated framework and shock tower. Could also weld on patrol coil towers from a wreck and run coils that way

 

[bods]

Yeah, depends if you want coil overs or not I guess... could probably make your own coil towers fairly easily anyway...

 

[joshy]

have a look at some of the pics in my build. I had the lowers triangulated aswell but its possible to fit everything inside the chassis rails without modding the rails. Like above I originally had the coilovers coming up into the tub. Was deffinetly my favourite set up and should have left it like that. the biggest issue is the fuel tank, if you don't mind moving it into the tray or behind the diff or a custom one to fit between the links.

 

[Navmania]

The problem with triangulated top bars is if you jump the car and don't have a strap from the chassis to the top of the diff you will just bend the arm and brackets because as they drop they spread apart through the radius. I had a setup I designed for my patrol and had it load tested to over 10 ton side load and it held up. You run arms in the standard position as upper arms in a patrol them you create the "v" in that set of arms. The way I did it I had the arms close at the top off the diff and then they spread to the chassis points or just short and you mount the bushes horizontal so they can flex. The point to remember though are the "v" to the centre of the diff allowing room for movement but the bushes have to all be the same hight on the diff housing. So draw an imaginary line through the mounting bolts for the top arms and make sure that the "v" point bushes are at the same hight or it will bind. The other thing is you need to use a Johny joint in each arm at the chassis ends and the diff ends if the "v" bars. Other wise if you use a rubber bush it will flog it out. I did this system in my patrol to get rid of the penhard rod and to stop the bump steer caused by it being on such an angle from the lift. I still have the prototype of the system and can take some pics to give you an idea if you need them to explain it better. It worked perfect and the patrol drove unreal with this setup in. I have never seen it done since either. It took me two years to get it built tested and sorted. I even had my own joints made but you can buy them from the states now.

Cheers. Brad.

 

[dilmah]

Yeah fuel tank won't be an issue. I plan to custom make a 120 - 150L tank out of 316 stainless and sit it behind the diff or behind the cab. If I decide to do Ironman i will need this quantity of fuel. I won't need the flex of a rock crawler hence the reason for keeping the chassis rails. Will have a look Joshy, only issue is your build thread is so long it takes ages to find anything

 

[dilmah]

Brad I'm running 1 1/4 Heim joints, they are already sitting in my shed so it shouldn't be an issue. If you don't mind posting some pics that would be great

Thanks, Dylan

 

[Navmania]

No worries I'll take some tomorrow. Rubber joints just don't work due to the side loads so your joints should be perfect.

 

[dilmah]

Hey Joshy, had a look at your build thread. What size pipe did you use for your rear shock towers? Would NB32 heavy wall be sufficient?

 

[Navmania]

This is the setup. It was the test sample I made so I only have one side due to the other being destroyed in the test but you should get the idea.
This bolts into the top brackets on a patrol



If you mirror image the arms you get the full idea



This is the chassis end.



These are the joints I had made. Adjustable and stainless ball



Arm mount has a rubber patrol bush.

This worked like a dream and the best it ever drove. The final product looked a lot better. This was just the test dummy I still have. The advantage is the suspension will perform 100% in all directions and not bind in any way. With no penhard rod bump steer.
Hope it helps Cheers.

 

[dilmah]

Ahh I see what you have done, you have triangulated the arms and used the diagonal arm to brace the lateral movements a panhard would normally stop. Interesting design, havnt seen anything like it. How long were the links?

 

[Navmania]

I'll measure them up and get back to you.

 

[joshy]

if you use the right material your not going to bend the uppers in the v configuration. Look at all the KOH/TT running that set up in the rear with a lot more HP.

Theres a 4link calculator on pirate4x4 if you want to play with anti squat and dive numbers. Separation and angle of the arms is important for handling and durability.

Ah all my stuff is out of DOM tubing, it would have been either 1 1/2 OD or 1 3/4 OD. Either would be fine with the appropriate bracing.

 

[Navmania]

I don't see how it can't stress and eventually break something if you raise and lower the arms a fair distance in the "v" configuration, the centres spread apart. All the "v" configurations I have seen have a strap going to the centre of the diff to stop this.
Not questioning you by any means Joshy. You have done a lot more modding than I have. The only reason I went the way I did with that setup was to get it engineered. I had a engineer and the RTA willing to certify that setup due to the amount of testing and proof I had that it was strong enough and made the patrol more drivable with a big lift in. A lot has changed since that was designed and built. It been over 10 years.

 

[dilmah]

Yeah thanks guys. Going to put some more thought into it before I rush out and buy $500 coilovers

 

[dilmah]

Found this on outers a while ago. Really like this design but I think the bracing is overkill for the intended weight. Carnt decide whether I should get some shock hoops bent up similar to the front then brace inbetween or run parallel bars like the one above then brace between them. I dont have a pipe bender or notcher yet so I will either buy one or get someone to do the bends for me.

 

[Navmania]

Hay Dilmah. The measurements for the arm on that setup are 495mm for the main arms and 295mm for the "v" arms. That's centre to centre of the bush. And that is also based on the top arms being a bit longer to roll the diff for tail shaft alignment. The arms can be any length but the shorter they are the stronger they are I think.
Cheers.