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Yes Kev...........as to wether it is good to have a low or high roll axis on a crawler.....would you like to roll your vechicle while driving to the supermarket??? not me.......the closer the roll axis of the suspension to the plane at which the cg is the more stability there is.

[ 10-17-2001: Message edited by: Pig Pen ]
 
...What about switching the links? I really like how Desertoy has his set up, and was thinking that'd be the best way to go...

But if you were to put the "point" of the triangle at the bottom of the axle instead of the top, that should change the pivot point of the axle to one where the body won't move quite so far off of the center of the axle... And also, it should flex better, leverage-wise, I would think...

But I may be totally wrong. <IMG SRC="smilies/biggrin.gif" border="0">
 
Originally posted by ToyFamily:
<STRONG>Does anyone see anything wrong with this concept, I have been kicking it around for about a year.
</STRONG>
Ok. I'm bored. And probably wrong. But here. <IMG SRC="smilies/biggrin.gif" border="0">

I think it's a great idea. I do think that you need to either lengthen the upper arms or shorten the lower arms a little so that the line running between the upper and lower axle mounts remain parallel with itself when you compare any two points of vertical only travel. As it sits now, I think it will create some squat upon acceleration.

It looks like there won't be much reer-steer...

Also, the bends might create an increased possibility of breakage.
 
Well one problem I see is the 90 degree bend in the lower links. A straight tube is much stronger in tension and compression than a tube with bends. Having said that you could engineer your tube size to acount for those forces.
Dave-are you so sure? <IMG SRC="smilies/fj.gif" border="0"> I have been readin up a little this weekend. It seems that you don't want to go to high with the roll center either. It seems that roll axis height controls mostly how stable a vehicle "feels", and not the vehicles ability to resist rolling over. With a low roll axis the cg can exert a larger torque on the body giving it more sway in turns. But, with a high cg the forces on the tire contact patch creat a large verticle lifting force causing weight jacking. In essence it will cause the inside tire to lift without the body swaying as much. The question is, if you were designing a rock crawler, and not a sports car, which way would you go, high or low?
Of course I could be all wrong too.

Kev
 
Oh and one more thing, I would definately try to triangulate the lower links. It seems that with triangulated upper and lower links it is easier to get little rear steer with some anti-squat. With parrallel links it becomes more of a challenge. Correct me if I am wrong, there seems to be a balancing act between rear steer and anti-squat.

Kev
 
Originally posted by Ghetto Fab.:
<STRONG>Well one problem I see is the 90 degree bend in the lower links. A straight tube is much stronger in tension and compression than a tube with bends. Having said that you could engineer your tube size to acount for those forces.
Dave-are you so sure? <IMG SRC="smilies/fj.gif" border="0"> I have been readin up a little this weekend. It seems that you don't want to go to high with the roll center either. It seems that roll axis height controls mostly how stable a vehicle "feels", and not the vehicles ability to resist rolling over. With a low roll axis the cg can exert a larger torque on the body giving it more sway in turns. But, with a high cg the forces on the tire contact patch creat a large verticle lifting force causing weight jacking. In essence it will cause the inside tire to lift without the body swaying as much. The question is, if you were designing a rock crawler, and not a sports car, which way would you go, high or low?
Of course I could be all wrong too.

Kev</STRONG>

Yes Kev that a boy........the point I was trying to make was that having the sus. roll axis closer to the cg would be better than having it far away. Theoritcally if the cg and roll axis were in the same plane the vechice would have no body roll going around a corner (fast) and would indeed lift a tire causing some "jacking"...
<IMG SRC="smilies/smokin.gif" border="0">
 
Originally posted by ToyFamily:
[QB]Does anyone see anything wrong with this concept, I have been kicking it around for about a year.

Looks ok but i am with ghetto on this one.........no bends on the lower dude.....oh by the way I think I met you one time on the con. You asked to borrow some gear fluid, some thin about how you flat towed the 4runner up there and puked all the fluid out of the front diff vent????
 
you must be talking about my dad (we're under the same "tag") but what I was thinking is to not nessesarily make the bends at 90 but less drastic and have an upper tube with plating in between, making a fin like link, somewhat like the Raptor.

So the links (upper & lower) want to be moving closer as they head to the front of the truck, or be parrallel......? (for the rear susp)
 
Originally posted by ToyFamily:
<STRONG>you must be talking about my dad (we're under the same "tag") but what I was thinking is to not nessesarily make the bends at 90 but less drastic and have an upper tube with plating in between, making a fin like link, somewhat like the Raptor.

So the links (upper & lower) want to be moving closer as they head to the front of the truck, or be parrallel......? (for the rear susp)</STRONG>
ok yea it must have been you dad, nice guy by the way. Anyways, triangulate the uppers toward the center of the diff. Try and triagulate the lowers towards the t-case. Now imagine a top view of this set up. Make two points , one where the uppers converge and one where the lowers converge. Now if the lowers had hardly trigulated at all don't make that second point. Now in the side view mark the point where the uppers converge at and the lowers. connect the dots(lalala). The angle of that plance in the side view is the roll axis of the suspension. If the Lowers are barly triaglulated the draw the roll axis parallel to the lower links in the side view from the point where the uppers converge.

This is hard to say in words but thats my best shot , a picture is worth a thousand words in this situtation.

Dave
 
to be different, and gain clearance? Just to tinker. Way back I was told that the lowers had to be mounted belowthe centerline of the housing, so I came up with that, and hadn't seen anyone else try it so I thought it would either fail miserably or be a new fad.
 
Originally posted by ToyFamily:
<STRONG>to be different, and gain clearance? Just to tinker. Way back I was told that the lowers had to be mounted belowthe centerline of the housing, so I came up with that, and hadn't seen anyone else try it so I thought it would either fail miserably or be a new fad.</STRONG>
not true about the lowers needing to be below the centerline, look at the pics of lances cruiser. that thing is sick, and hes got all the links on top, only problem i could see is more leverage/stress on the weld holding the bracket to the housing, but apparently it can work with good welds
 
Originally posted by ToyFamily:
<STRONG>that's what I got???
<IMG width=439 height=369 SRC="http://www.pirate4x4.com/ubb/uploads/sketch.jpg">

now is there any way to describe CG?

[ 10-18-2001: Message edited by: ToyFamily ]</STRONG>
Peliminary drawing looks ok. However, the lowers don't need to be that triangulated I say this because you might have interfearance issues with the frame on that yota. Suggestions: Mount lowers on top of housing and put the uppers up higher (taller truss or however you plan to make it.
 
Is there any way we can archive this thread so that people can refer to it in the future? I'd think that it would be a great resource for anyone looking to build their own link suspension. After looking at those pictures and reading what was said I think I'm going to change my design to incorporate some of those ideas. One question though, if the lowers dont need to be triangulated as much, what would be the ideal amount of triangulation (<--- is that even a word? <IMG SRC="smilies/biggrin.gif" border="0"> )
 
Originally posted by ToyFamily:
<STRONG>Does anyone see anything wrong with this concept, I have been kicking it around for about a year.

<IMG width=489 height=526 SRC="http://www.pirate4x4.com/ubb/uploads/linksktch.jpg"></STRONG>
That design is goign to tilt your pinion WAY down as it droops.

J. J.
 
Originally posted by Pig Pen:
<STRONG>ok yea it must have been you dad, nice guy by the way. Anyways, triangulate the uppers toward the center of the diff. Try and triagulate the lowers towards the t-case. Now imagine a top view of this set up. Make two points , one where the uppers converge and one where the lowers converge. Now if the lowers had hardly trigulated at all don't make that second point. Now in the side view mark the point where the uppers converge at and the lowers. connect the dots(lalala). The angle of that plance in the side view is the roll axis of the suspension. If the Lowers are barly triaglulated the draw the roll axis parallel to the lower links in the side view from the point where the uppers converge.

This is hard to say in words but thats my best shot , a picture is worth a thousand words in this situtation.

Dave</STRONG>
The following is all referenced from a side view of the links....

When looking at that drawing from the side, what correlation is there between the converging angles of the upper and lower links? In other words, say the mounting points on the axel for the upper and lower links are 10 vertical inches apart from each other, should the mounting points be the same distance apart where they're connected to the frame? It seems to me that they should be converging, but how/what does that change by moving them (upper and lower links) from being parallel to each other to a converging angle at the frame by the x-fer case and how do you determine what angle would be ideal? Does that make sense?
 
Are there any problems with fabbing up a front suspension setup like the rear of deserttoy's rig?



I want to do this type of setup front and rear so my suspension is balanced but I don't know if all the stresses related to steering and braking on the front axle will cause problems. Can anyone tell me if this type of setup is a good choice for a front application?
 
It will work fine just use good stuff and make sure you have clearance around the driveshaft when articulating and the tires at full turn. My center links miss my crankshaft pulley by about 1/2" at full compression, and they miss my starter by about the same at max articulation
(R wh. up/ L wh. dn) : )
 
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