bsevans
Focus on the Journey
Try a 200 pound skid plate. Mine is only 85/90 pounds, but it is a start.
How to lower roll centre? (1 Viewer)
- Thread starter OpTimuS
- Start date
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Try a 200 pound skid plate. Mine is only 85/90 pounds, but it is a start.
It has been so long since he wheeled it, he probably can't find it
It has been so long since he wheeled it, he probably can't find it
It has been almost a year since I wheeled my 40
I'll dig up some old pics.
are you planning on 4 linking all 3 of your axles? are all 3 going to be drive axles? maybe your rear axles can share the same link points if you turn the links around on the middle axle? i'd like to see someone run that through the 4link calculator.... and i can see why your not going with coil over shocks, would be like 3k just in shocks....it all seems enormously complicated 
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How about some hydraulics? You could just tilt the body over to the side or lock the suspension in place so it won't lean on a side hill.
ntsqd
technerd
I dunno, my friend Cam made it work fairly well.
yeah, cause the hydraulics over airbag independant suspension setup in that rig and the chain driven diffs (Ferd 9" IIRC) are pure simplicity
When did he put the sunshade on it?
ntsqd
technerd
It's had it almost from the beginning. Basically a well fitting tarp.
Let me tell you, when it's like that, it is a bloody looong ways down to climb out from the back seat over the spare tire.
Yes, a 9", but also HMMV redux boxes. The next gen is far simpler and lighter. Hope it gets built.
Let me tell you, when it's like that, it is a bloody looong ways down to climb out from the back seat over the spare tire.
Yes, a 9", but also HMMV redux boxes. The next gen is far simpler and lighter. Hope it gets built.
- Thread starter
- #32
It has been almost a year since I wheeled my 40
I'll dig up some old pics.
looking forward to it thanx dude.
are you planning on 4 linking all 3 of your axles? are all 3 going to be drive axles? maybe your rear axles can share the same link points if you turn the links around on the middle axle? i'd like to see someone run that through the 4link calculator.... and i can see why your not going with coil over shocks, would be like 3k just in shocks....it all seems enormously complicated
o.k....... I only have designs (and when I mean designs I mean pictures drawn on the concrete with chalk whilst drinking copious amounts of amber gold) for 2 rear 4-links, identical in construction, 34"ish lowers, and 42"ish uppers, single triangulated, lowers parrellel to chassis due to the 3 driveshafts I need to make my 6-wheel-drive setup work.
I have not considered reversing my links on the mid-diff, I could hazard a guess though and say that it would be pointless because isn't there a reason people do shackle reversal's on L/C's?
You are right I would be looking at about $4.5k in AUD for shocks alone, where I have an idea on how to have statically mounted load sharing air-shocks. Basically the rears will be setup (in pairs, so 2 per diff like normal) to take 65% of the weight on both diff's, and the front air-shocks will be paired (so 4 shocks for the 1 diff) but I am going to join the shcrader valve on the pair's of front shocks to equalise the charge pressure and therefore create a 4.0" airshock.
yeah yeah i know before you guys say it this is ALL IN THEORY. well I am just gonna give it ago, can't hurt right.
How about some hydraulics? You could just tilt the body over to the side or lock the suspension in place so it won't lean on a side hill.
some guys over here in Oz do that but, I am trying to keep my budget low here, hydraulics are expensive (as I know from dealing with my hydraulic steering order)
not to be contradictory...... but yes you are correct, however.
There is one setup I have seen and it appeals to me. It is basically a coil-over shock, but the end of the cylinder/ram is not sealed it is connected to a free-floating hydraulic system, so with an open DCV (open centre 3-2 I believe) the fluid in the shock offers a form of dampening as the spring (wrapped around the cylinder/ram) operates in a traditional coil-over setup. When you want to charge the cylinder and gain height (or put more weight onto a wheel with insufficient drive) all that is required is to operate the DCV in a normal manner.
I dunno, my friend Cam made it work fairly well.
How much does that demon weigh?
ntsqd
technerd
I know that he weighed it after it's first Comp., but I'm struggling to come up with the number. It was far less than most of us guessed. Say in the 4700-5500 lbs range.
The basic problem in trying to use a coil-over as described above (as a hydro ram) is piston area. Has anyone actually done it successfully?
I'd be surprised if they did. Since the piston allows fluid flow through it (unlike a hydraulic ram), the greatest effective piston area for the hydro system to push against is the area of the shaft. Not a lot of area - well under one square inch for even the biggest shock shaft, so not a lot of force in spite of such a system's high pressure.
Have you found a copy of ExcelCAD 3.0 to play with for laying out the linkage? Beats cutting a bunch of expensive metal.
The basic problem in trying to use a coil-over as described above (as a hydro ram) is piston area. Has anyone actually done it successfully?
I'd be surprised if they did. Since the piston allows fluid flow through it (unlike a hydraulic ram), the greatest effective piston area for the hydro system to push against is the area of the shaft. Not a lot of area - well under one square inch for even the biggest shock shaft, so not a lot of force in spite of such a system's high pressure.
Have you found a copy of ExcelCAD 3.0 to play with for laying out the linkage? Beats cutting a bunch of expensive metal.
- Thread starter
- #34
I have been using 4-bar linkage caluculator v3.0 (yeah yeah I know what my signature says.... but really with a 6x6 this is using the if i can get it to fit calculator.......)
I have the following setup @ 6" to bump stop, static height, 38x 11 boggers, 36" Cog, I have no idea what my weights are so I used 5K lbs for over all and 800lbs for front and 700lbs for rear diff, and 106" WB
Middle diff:
upper length: 33 1/8"
lower length: 40 5/8"
AS :125%
roll centre height: 26 1/3"
10* roll oversteer
I have the following setup @ 6" to bump stop, static height, 38x 11 boggers, 36" Cog, I have no idea what my weights are so I used 5K lbs for over all and 800lbs for front and 700lbs for rear diff, and 150" WB
Rear diff:
upper length: 33 1/8"
lower length: 40 5/8"
AS: 177%
roll centre height: 26"
10* roll oversteer
I have no idea how this will perform, but I am going to give it a shot as it seems to be the best setup I could draw on the ground under my chassis ensuring every thing works, and I can fit all shafts and my links dont interfere with each other.
I have the following setup @ 6" to bump stop, static height, 38x 11 boggers, 36" Cog, I have no idea what my weights are so I used 5K lbs for over all and 800lbs for front and 700lbs for rear diff, and 106" WB
Middle diff:
upper length: 33 1/8"
lower length: 40 5/8"
AS :125%
roll centre height: 26 1/3"
10* roll oversteer
I have the following setup @ 6" to bump stop, static height, 38x 11 boggers, 36" Cog, I have no idea what my weights are so I used 5K lbs for over all and 800lbs for front and 700lbs for rear diff, and 150" WB
Rear diff:
upper length: 33 1/8"
lower length: 40 5/8"
AS: 177%
roll centre height: 26"
10* roll oversteer
I have no idea how this will perform, but I am going to give it a shot as it seems to be the best setup I could draw on the ground under my chassis ensuring every thing works, and I can fit all shafts and my links dont interfere with each other.
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Like I said, it has been done. Heck, it was done like 4 years ago
They have been removed for a plusher ride. Welderboy likes to go fast in the rocks..here is a link to the build thread
WB's shop and "Bone Scraper" (AKA-Cadillac Poop-daville) - Pirate4x4.Com Bulletin Board
Optimus, are you planing on running this thing flat out?? If not, 6" of up travel is probably not needed..
Questions, 44" between the rear tires??
Why is your AS so different between the two axles?
Try to get your roll center up if you can, and get that roll over steer angle trimmed down as well.
Wanna link the spreadsheet or at least take a screen capture of the design?
I will say this tho and please do not take it the wrong way... You tend to over complicate things. You are jumping into the water with both feet before you even know how deep the water is or even if it has sharks with freaking lasers attatched to their heads in it.
Why a 6x6?
ntsqd
technerd
Oh well. I don't go there. I'm guessing that he had to make the valving extremely stiff for it to work at all. No wonder it was removed. May as well build a low-rider with hydraulics.
- Thread starter
- #37
Like I said, it has been done. Heck, it was done like 4 years ago
here is a link to the build thread
WB's shop and "Bone S****er" (AKA-Cadillac Poop-daville) - Pirate4x4.Com Bulletin Board
Optimus, are you planing on running this thing flat out?? If not, 6" of up travel is probably not needed..
Questions, 44" between the rear tires??
Why is your AS so different between the two axles?
Try to get your roll center up if you can, and get that roll over steer angle trimmed down as well.
Wanna link the spreadsheet or at least take a screen capture of the design?
Why a 6x6?
Thanks for the thread link, sweet ride, even more interesting read.
and no I am not even considering hydraulics. Anyway why would 6" be not needed? I was actually thinking of 8" but that was not enough droop, and probably over compensating. I do still have to drive at 40mph down corrugations. I also will be doing some mud racing, not so much for competition just more of a testing ground for the gear I build.o.k. yes 44" between the rear diff centres. (and a 4" difference between the wheel mounting faces on them just to provide more grip, but more on that later.......) I feel that space gives me room to shorten my WB, but not lengthen anymore than that because to keep things simple and clean it provides ample room, and if I want I could still move up from a 38 bogger to a 42 TSL if I wish down the track, and if my drivetrain will hold up to the abuse, just remember I am using all L/C 91/2" drivetrain here.
better to have more than enough room than a lack of space. I really hate clutter.My AS is purely that different due to the 100%AS line difference when keeping identical link geometry of a 106" WB and a 150" WB. This is why initially I started this link because I had no idea what ROT (rule of thumb) I had to keep in mind when building this and Fransesco highlighted my worst fear when he threw his thread up on the site. See having such a long wheelbase with ample up and down travel is ideal for mud (at least the territory I drive) and going up or coming down hills. But the roll-centre height always worried me. now I realise that there are some things I can do to my truck to make it more stable on side slopes. I still feel however my best bet is to now stick with the geometry I have and try to lower my truck, and my CoG as much as possible. AND When building keep in mind some of the ideas for raising my roll centre and trying to keep my AS down.
oh and I have completely no idea how to link the spreadsheet to this page sorry. But if you can tell me how I could do a screen capture.
yes I know, and I like laser-beam sharks. (well not really I just get bored and think up more stuff how I can modify my car
). Pretty much if I have the resources and it's doable, I am keen to do-it. Y B normal? And yes I know that sounds dumb, but I do have limited resources, no HP D60 here with HV bead-locks.
Finally to address the issue of 6x6......
well I like the idea of 3 lockers instead of 2...... Well the rear diff will be welded, the middle diff will have a detriot/aussie-type locker and the front diff will have an ARB. I also have 3 diff (1 spare so this idea came about after drinking to heavily), Also with my TOY axles I am kinda limited in weight/dia/width of tyres so I am running 3 different offset diff's, the front will be stock 60 width lets call it 61WMS" the middle diff will be an 80 series diff with 2" spacers, ltes call that 69WMS" and the rear diff will be a 60 series with 2" spacers lets call that 65WMS". When worked out (not calcu-malated) if used with a 11" tread width I effectively have 19" of tread width on the deck, always good for finding grip in mud, and I can't see it being bad on a dry, dusty dirt hill.
Also The reason low-range gears are employed in LR on 4by's is to increase torque. Lot's of grip and torque equals momentum (aka drag cars), but too much torque and not enough traction equals wheelspin (aka 4wd sitting on side of hill going nowhere) By employing 6 wheels with (for example) 1000Nm of torque you have 166Nm per tyre whereas with 4 wheels you have 250Nm per wheel..... less torque on more ground (area*) equals momentum. Also that same torque calculation can be used to provide some form of relief for my drivetrain. (even though I am trying to build a G/box adaptor for a final drive ratio of 200:1+
Also with the mud we drive in around here I can't see 6 lots of tyre footprint being a bad thing after-all we do let tyre pressures down to increase footprint.
Finally you said early on in your thread that i should try to get that roll over steer angle trimmed down as well, but I am going out on a limb here and I am going to say this which will be complicated and could probably most-likely not work:
If my middle diff rotates with the pass wheel down the pass wheel will slighlty roll forwards (and begin to fold).
If my rear diff rotates with the drivers wheel down the drivers wheel will slighlty roll forwards (and begin to fold).
If this roatation becomes too extreme the forces will try and bind up the truck and eventually the links will fail or mounting tabs will bend. But I have designed this over steer in. I have done it for this reason:
If the diff is 'oversteering' (one wheel folding ubder) on a normal 4x4 the truck becomes unstable and the diff will try to drive under the chassis and lift the body (generally in my observations in the opposite direcion to the 'folding/oversteering' wheel).
O.k. now you are thinking I am a complete psych and I need my meds. but:
If the chassis is lifting away from the folding wheel (pass) to the driver side but the driver side also has a folding wheel then my crazy-outside-of-the-square-I-have-no-experience-in-this-type-of-6x6-construction-before-ideology dictates that the forces will cancel each other out and actually load up my suspension therefore loading the wheel and creating drive.
Only time (and doctors visits) will tell.
Anyway....... very very off-track.
Optimus, i have to admire your enthusiasm, self confidence, and your outside the box thinking- BUT i think that before you dive into this that you need to stop and think and realize that probably just about everything imaginable has been built and tried in the offroad world, the things that work and work well are what you see out there in high end rigs and in competition.....if 6x6 worked well in rockcrawling you can bet that people would be building comp buggies that way, similarly in mud racing, desert racing etc.....you should search on the internet long and hard and find people who have built similar rigs to what your thinking about and try to get ahold of them and find out if they were happy with how they performed and then go from there. i also think that most professional rock buggy fabricators would cringe at the idea of trying to build what your suggesting....in fact i think a mechanical engineer with years of buggy building experience would probably just burn a hole in his head with a plasma cutter after he got about half way into it lol!
edit- i'm definitely NOT saying that you shouldn't do it or that you can't, just that you should make sure that it is a good idea and worth the extra effort and money and time not wheeling that it will require....if you feel that it's worth it and that your up to the challenge then go for it....and post up a comprehensive build thread!
edit- i'm definitely NOT saying that you shouldn't do it or that you can't, just that you should make sure that it is a good idea and worth the extra effort and money and time not wheeling that it will require....if you feel that it's worth it and that your up to the challenge then go for it....and post up a comprehensive build thread!
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ntsqd
technerd
Lots of folks told Cam that his Chainlink wouldn't work either. It works very well except for one Achilles Heel that nearly every Comp course has at least one of. His next gen design address' that though the sad trend in comps toward speed over finesse probably makes it a non-contender. Down there at TdS it is nearly unstoppable. And you should see how much reach his cherry picker has when the upright & boom are mounted to the spare tire carrier!
My point is that if you think it will work and building it doesn't break you or get you divorced, then I say try it!
This is coming from 1/2 of an ME, the other 1/2 is a MfgE.
My point is that if you think it will work and building it doesn't break you or get you divorced, then I say try it!
This is coming from 1/2 of an ME, the other 1/2 is a MfgE.
That is truly ugly, .....if it were the only chick on a deserted island I'd swim out to sea to drown
yeah, cause the hydraulics over airbag independant suspension setup in that rig and the chain driven diffs (Ferd 9" IIRC) are pure simplicity
When did he put the sunshade on it?
