6x6 steering ideas / open debate

Ok, here's the deal... I'm in the mood to do something either stupid or amazing(I won't know til the project it finished! ) so I've given myself about 1.5 years to build a 6x6 XJ. I'm wondering this: should I bother with all wheel steering and if so what would be the best way (with/against/proportional to the fronts, mechanical/electrical) to steer the back wheels. The assumtions are daily driver, show car, #3 and #4 trail exploration, 34" rubber. budget 10k-15k and I'm currently shopping for the 4dr donor body. any other info needed let me know. I'll post body sketchs prolly tuesday.

-rO

Good luck with this one!!! I mean this sincerly. I know it can be done I saw an issue of 4wheel and offroad a couple years ago that had a trail pic of a 6x6 CJ7 in it so anything is possible. As far as steering goes if your mainly going to use this for highway and show use with limited offroad use I would only have front wheel steering. Putting another axle under the XJ will not decrease the stock turning radius that much. From an engineering stand point if you want all wheel steering you will need to ad lenghth to the XJ (unless you plan on putting the third axle right in the middle of your jeep , that would be another nightmare) in order to keep your rear tires from hitting each other while turning (esspecially with 34's). You will also need to add either some sort of electric steering control or electric over hydraulic assist because trying to proportion front and rear steering from the steering wheel alone could eat up your 10-15k buget by itself. Plus rear steer is not really somthing you need to be using when doing 65mph down the highway.What I would suggest is to use a setup similar to that used on monster trucks with a switch to control rear steer this will also allow for self centering of the rear wheels when the switch is diengaged. Well I hope maybe this helps a little again good luck !

talk to USA6x6 they are the currently the experts on this stuff. And while you have them on the phone, ask them to send me a set of their DOT double beadlocks... for refering you... ok. thanks.

Roll-over said:

Ok, here's the deal... I'm in the mood to do something either stupid or amazing(I won't know til the project it finished! ) so I've given myself about 1.5 years to build a 6x6 XJ. I'm wondering this: should I bother with all wheel steering and if so what would be the best way (with/against/proportional to the fronts, mechanical/electrical) to steer the back wheels. The assumtions are daily driver, show car, #3 and #4 trail exploration, 34" rubber. budget 10k-15k and I'm currently shopping for the 4dr donor body. any other info needed let me know. I'll post body sketchs prolly tuesday.

-rO

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There is a 6x6 XJ in existance (or at least 3 axle one). It was featured in a movie, but I can't remember which (powerball?). MIght be worth it to look up info on that.

Ludakris said:

talk to USA6x6 they are the currently the experts on this stuff. And while you have them on the phone, ask them to send me a set of their DOT double beadlocks... for refering you... ok. thanks.

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haha, I've checked them out... well there goes half the budget, now all i need is a second axle.

Kejtar said:

There is a 6x6 XJ in existance (or at least 3 axle one). It was featured in a movie, but I can't remember which (powerball?). MIght be worth it to look up info on that.

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I've heard rumors of that one. If anyone knows anything about it plz share! It was mentioned in a thread at ifsja.org. The info there is that the rear axle is non-driven and just "hangs" from the back. Has anyone seen a project page for it?

speaking of axles... danas in tandom... output pinion off the back of the crown gear or gear/chain box off the input shaft?

something that kind of struck me... short of looking cool, what would be a good application for it? Most of wheeling I come across the 6x6 would have an interesting time. I did see some 6wd vehicles in forested muddy rutted european mountain regions and also in snowy/icy applications, but I think in rocks it'd have a hard time.
So with that in mind, look into what you want it to do and then gear your searches/mods towards it.

I live in San Antonio, TX so the local scene is mostly dry creak beds with the occasional photo-op boulder. for a weekend trip there is desert to the west, +1000' hills to the north, and coastal sand to the east. Most of the areas the jeep wheels don't take much skill/gear (it's bone stock at the moment.) The 3rd axle mod adds looks, cargo room, weight capacity, and rubber contact surface for goo surfing. Plus it's apparently something only hollywood would attempt.

I wouldent recommend Daniel, USA 6x6.

That 6X6 Tj he takes credit for I heard costs about $60K to make in about 3 months. It used the custom Portal 9in center axles, with all wheel steering.
I cant find the thread on pirate4x4... it was one of the largest threads Ive seen on there. October 2002 ish...

I cant find it..

The movie was 'Rollerball'. A quick search should turn up more info on the XJ.

Semi trucks have differentials that have an input yoke and then a selector mechanism that goes to the axle behind it . i can see a few verry difficult problems to work on. First, powering the rear most axle. A semi axle and components just would be too big, something would have to be custom designed and built. And it would be :spin3: to not have a fully functional vehichle.
Then you run into the problem of axle mounting. Leaves won't work unless you had one set mount outboad of the frame rails and one mount in board. A four link and coil overs or coils would work for the front. But I don't see a way to locate the rear axle unless you ran a four link going the opposite direction, then there is the postential for the tires to hit each other under compresstion. Also the driveshaft connedting the axles would have to be an impressive piece of engineering because it would have such a huge range of movement and it would be so short.

You got me thinking way to hard about this. Now I have to go to my Mechanical Engineering lab. :lecture:

cw, lost much sleep on that one! I started with the idea of upside down leafs but that would cause the rear to stear away from an off balanced load. so now I am looking at 4link from the middle axle to the chassis and 4link from the rear to the middle with dual coil-overs at each axle end. as for the drive shaft play I am thinking about placing the 4links to the rear axle in an "XX" configuration to assist in maintaining the u-joint allignment in full flex.

does that seem do-able?

-rO

Zebaru said:

The movie was 'Rollerball'. A quick search should turn up more info on the XJ.

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Did some poking around, since this piqued my interest - somehow, it had never sunk in with me that it was an XJ. From http://www.rollerball.com/league_cars.html , you may want to try to track down Gino Lucci; he apparently oversaw the build of the vehicles.

Just thinking about it from a layman's point of view, though, if you can't do steering on each axle you'll likely need to run each axle open - remember that you'll be dragging 50% more contact area around corners and on lane changes. There are passive steering methods that can be used to provide a couple of degrees of motion; IIRC, a lot of military-spec Tatra trucks used it on their multiaxle designs. Might be worth investigating them as well (and the Tatra 603, which just plain rules but has nothing to do with what we're discussing here).

In fact, based on what USA6x6 charges for their conversions, I'm wondering if it might not be cheaper to temporarily export the car to the Czech Republic, have Tatra undertake the work, and bring it back in.

haha with what usa6x6 changes, I could ship it to houston and let NASA do the work! Nope, I'm happily stuck with the design and basic fabrication, all though there is a machine shop locally that gives me good deals on the turning and milling work. Besides, this way I get the bragging rights afterwards.

yeah, the m-715 project... i can't wait to see that one hit the road!

Search Gamma Goat (tried to post a link, didn´t work) Drove one for about 5 years. Kind of a novel approach but it worked. The trailer only flex´s up and down, it´s locked to the chassis left and right. Some of the engineering might help you out, if you can find some drawings.
Saw a 6 wheel drive CJ-8 on a site somewhere, I´ll see if I can´t find it again and post it. Might have been Green valley jeeps or Alta Vista, only know for sure it was a west coast site.

I looked at doing this 20 years ago with a Toyota pickup I had at the time. The way I thought would be the most simplist at the time was using the same setup as road graders. Even thought of getting the whole rear setup off one of the small graders I had seen about. Their rear is setup with one diff and axle housing but at the hub ends they have a beam that runs forward and aft that transfers the drive to a hub at each end. It is be chain driven and that it would swival at the centre where it attaches to the axle housing. This would allow pivot indepentantly at each side. This setup could just run everything else stock with no other driveline mods.
Found this below on graders:
Beyond the fact that most (but not all) graders have 6 tires there are a lot of subtle differences. In most instances, for example the rear wheels will be powered from a single drive axle by roller chains running in an oil bath 'chain box' which also serves as the walking beam.
Did a lot of searching and found this for you.


This is off one of the full size ones but you get the idea. You might be able to end modify a Dana 60 say with the chain box beams made from RHS steel tube?

I thought about the graider rear for a while the problem is when I worked construction years ago we had a blade toss it right side chain on the road at about 45 mph between sites. $14,000 damage to the machine. Imo that design doesn't like speed much. I could use a fiber belt to drive it, but then the torque might be an issue. I'll prolly use a pair of FSJ front axles for the rear that way I can add rear steering if budget allows and the diff is offset so i can gear a bypass drive from the center over to the pinion shaft in the diff. the tricky part will be the suspension linkage between the center and rear axles... i need extreme vertical and radial flex with almost no lateral flex, plus i need to manage shaft expansion and joint alignment. that's where I'm hoping to get a little engineering help. I'll post drawings this weekend and picks as i get into the build.

thanks all and if anyone wants to lend some time on the linkage design let me know.
-rO

USe a "Deuce and a Hlaf" Drive Train. I think their more commonly referred to as M49. You can get the vehicle off ebay and then you can figure out how to turn it. It has an output shaft on the back of the Front-Rear Pumpkin. I know thats confusing.