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Front suspension geometry...lets get in depth...
- Thread starter Willis
- Start date
Willis
NAXJA Forum User
- Location
- Hoquiam, WA
Beezil said:willis, screw the 4-link.
just build one of these instead:
I just can't find the parts. ORGS, and URF don't carry them. Guess I need to open up the Grainger Catalog.
- Location
- Indiana-Missouri
the only thing wrong with this set-up, is you won't be allowed to run any trail that woody is on.
he hates magnet kids.
he hates magnet kids.
- Location
- Bakersfield, CA
Hey, Woody likes anything that uses magnets.....he'd dig it!
Back to the subject matter. Steve, what are your thoughts on wanting a triangulated upper link/links so you get rid if the track bar? I realize it's something different, but I just don't see anything negative about a front track bar, and there are definitely some things that are positive especially if you'll drive it fast off road and on the street.
Forgive me for bringing this up, but some people do mods purely for the fun and cool factor, rather than because they'll actually work better. Cracks me up sometimes when pics are posted and a bunch of people go oooh and aaahh, but the only thing I want to see is what it does in real life, on the road and on the trail. I appreciate new ideas and good fabrication, and some of us really enjoy the fabrication part of it, but in the end it should be to improve performance or we're just fooling ourselves.
Back to the subject matter. Steve, what are your thoughts on wanting a triangulated upper link/links so you get rid if the track bar? I realize it's something different, but I just don't see anything negative about a front track bar, and there are definitely some things that are positive especially if you'll drive it fast off road and on the street.
Forgive me for bringing this up, but some people do mods purely for the fun and cool factor, rather than because they'll actually work better. Cracks me up sometimes when pics are posted and a bunch of people go oooh and aaahh, but the only thing I want to see is what it does in real life, on the road and on the trail. I appreciate new ideas and good fabrication, and some of us really enjoy the fabrication part of it, but in the end it should be to improve performance or we're just fooling ourselves.
- Location
- Foresthill, CA
URF is only interested in mods that work well on-road, as Richard is always quick to point out.
I dig track bars, I think they are the only way to keep a drag link and not have some funny handling characteristics at high speed (commonly referred to as "bump steer"). If you're going fully hydro steer, I'm all for triangulation of links to lose the track bar, but otherwise, they are the best way to go for a rig driven in different kinds of conditions.
The best solution other than leaf springs, that is.
CRASH
I dig track bars, I think they are the only way to keep a drag link and not have some funny handling characteristics at high speed (commonly referred to as "bump steer"). If you're going fully hydro steer, I'm all for triangulation of links to lose the track bar, but otherwise, they are the best way to go for a rig driven in different kinds of conditions.
The best solution other than leaf springs, that is.
CRASH
- Location
- Indiana-Missouri
go watts linkage or go home
Willis
NAXJA Forum User
- Location
- Hoquiam, WA
Goatman said:
My goal with this thread was not necessarily to cover one or another front suspension design, but to learn some of the geometry that effects the characteristics of any front suspension, to aid in making a good decision on what type I desire.
That said, I have seen long arms (radius arms) at work, and was not overly impressed with the unloading. I have not learned yet how to calculate the AD% for radius arms (Ford, Rover, Clayton's), but I'd imagine it must be pretty high. For that reason, I chose to investigate alternatives.
3 mid arms like your's intrigue me (or any asymmetrical system for that matter). The issue I see with this design, is that when drawn from the side with 2 arms (left side), you can calculate an AD%, and make that a respectable number. When drawn from the side with only one lower arm (right side), you can not calculate AD% because of the missing link (I don't know if the AD% would be infinite or not). What does this have to do with handling? Well, the way I see it, the AD% for the front, as a whole, will be what the AD is on the left. However, when in a hard braking situation with high traction, that left anti-dive is going to keep the left side of the frame rail from diving. The right side does not have any upward force from the upper control arm, and will dive more than the left. When the right dives more, it may reduce the angle of the lower control arm. By doing so, may push the right side of the front axle forward inducing a leftward brake pull which may be exactly what you want to avoid in a panic situation. Of course, this is my postulation on what could happen. Have you experienced this yet?
4 mid arms with track-bar. This option really has not been explored (Kinda by Tomkin, but not really what I'd want), and would probably net a fairly good suspension. I would love to try something new, but will be using family tools and workspace to do any serious work that needs to be done. Some things can be done in my single car garage, but I just don't have the room or tools for design after design like some people **coughBeezilcough**. Someday though. The problem I see with this type suspension, is the fact that it creates a twisting bind upon full flex where all 4 mounts are fighting each other.I am thinking Rock Ready, no compliance arms that break the front axle bridge. This idea is still on the back burner, I may explore it some more. Rubber joints on the axle end would be a must.
And finally, the track-bar-less parabola, wishbone, 4 link, whatever the design, still functions similar. I plan on running the inverted T steering setup, hydro is not an option at this time. I know I will here all kinds of "what about bump-steer" comments. The thing I see, is the fact that the suspension moves similar to a leaf sprung vehicle. CJs did not have track-bars, but YJs did. I plan on running hi steer, with a dropped pitman arm on a HD saginaw 4 bolt box (not the weak XJ box). The flatter the drag link, the less likelihood for bump-steer. What I like about this type suspension is, equal, and good AD numbers from side to side, excellent, bind-free flex, and the cool factor doesn't hurt either.
Steve
- Location
- Bakersfield, CA
Willis said:
I didn't answer earlier because I wanted a little seat time before I did. We had this discussion once before about there being different anti-dive amounts on each side. This is theory, and I don't think it bears out in reality. My rig goes perfectly straight under braking, even hard braking. I had some pulling to the right when braking initially after putting in this suspension, but it's been gone for quite some time, and had something to do with alignment, a weak track bar mount, or something, but it's long gone. I didn't remember any pulling for a long time, but just to make sure I went out and drove it around tonight. I can hit the brakes hard or soft without holding the wheel and it stays straight. The front end does not dip more to one side, but as far as I can tell dips evenly. BTW, my upper arm is on the right side and attaches to the axle on the same mount as the track bar does.
Initially, I built a four link on this axle. My original concept was the three link, but I put a mount on the drivers side just to try it. It didn't work. Like you said, it needs rubber somewhere, and I had johnny joints on both ends of the lower links and JJ's on the axle end and heims on the frame ends of the upper links. Trying to cycle the suspension with no springs or shocks hooked up wouldn't happen. A floor jack on one side of the axle would just start to lift the vehicle rather than raise the axle any more. In the real world, with tires on and on the trail, it probably would have flexed, but only by extreme presure on the JJ's and something would eventually have to give. So, I never ran it with both upper arms.
A mid arm four link would work well, even without rubber bushings, but the lower and upper arms would need to be close to equal length and parallel. When the upper and lower arms are equal length and parallel there is no castor change as the suspension cycles, so even when articulating there would be no binding in the bushings. Work on that a little.......
Or just go three link........very simple. The only issue is that it has to be strong, but clearance is much easier to deal with.
Willis said:
Here I can give you some real world experience. I have the 3 link like Goats but I put my upper on the correct side, the driver's side (Goat
) .There isn't anything different here than when it had four arms in it's driving and braking charateristics. I can lock up my 35" tires on dry pavment and not have a bit of pull. (other than the normal sliding from being locked up) Turning either right or left is exactly the same. No more or less dive or under or over steer. This Jeep handles better than any other XJ I've ever built! I drive 3 different XJs and MJs (2 four link and one 3 link) and can't tell a difference between the setups on the street, but off road the three link just articulates over obsticals much better!
My upper arm is made the same as a lower arm using 2.5" JJ with 9/16" cross bolts. Both mounts, axle and frame have been redone accordingly. So alot of extra strength has been built into my upper arm setup.
mark
Willis
NAXJA Forum User
- Location
- Hoquiam, WA
Thanks guys for the real world experience. That is definitely an option. For some reason I thought Goat's was on the drivers side as well.
I sketched the 4 mid arms. You are right about the caster change on articulation/compression/droop. I drew them at 24" each. The lower just below the framerail, but with 7" separation at the axle end, equal length arms, being parallel, that puts the uppers above and behind the existing upper arm mount (read, inside the cab where your left foot rests while driving). Now, I don't have a problem cutting and modifying the floor, but it seems like more work than it may be worth. Also, when the upper and lower arms do not form an imaginary intersection, I don't see how to calculate AD. It looks though, that it may end up performing much like long arms, where they will unload when climbing. Sure, a limit strap would help, but then I might as well go with long arms.
I'll really look close to the 3 arm thing. Just out of curiosity, how long are your upper and lower arms (both Mark and Richard)?
Steve
I sketched the 4 mid arms. You are right about the caster change on articulation/compression/droop. I drew them at 24" each. The lower just below the framerail, but with 7" separation at the axle end, equal length arms, being parallel, that puts the uppers above and behind the existing upper arm mount (read, inside the cab where your left foot rests while driving). Now, I don't have a problem cutting and modifying the floor, but it seems like more work than it may be worth. Also, when the upper and lower arms do not form an imaginary intersection, I don't see how to calculate AD. It looks though, that it may end up performing much like long arms, where they will unload when climbing. Sure, a limit strap would help, but then I might as well go with long arms.
I'll really look close to the 3 arm thing. Just out of curiosity, how long are your upper and lower arms (both Mark and Richard)?
Steve
- Location
- Bakersfield, CA
Willis said:
Nope, my UCA is on the RIGHT side.
My lowers are 19.5" and my upper is 16.5".
- Location
- Indiana-Missouri
Goatman, why right side?
someone pointed out to me the drastic pinion angle that would result with the drivers side at full droop with running only a pass side upper. I didn't think it was a big deal when I was in the building process until I forklift tested it....
I've run single uppers on both sides, never had a problem, but I was just interested in front driveshaft u-joint life and ran the upper on the drivers side for the remainder of that set-ups life.
what's your excuse?
someone pointed out to me the drastic pinion angle that would result with the drivers side at full droop with running only a pass side upper. I didn't think it was a big deal when I was in the building process until I forklift tested it....
I've run single uppers on both sides, never had a problem, but I was just interested in front driveshaft u-joint life and ran the upper on the drivers side for the remainder of that set-ups life.
what's your excuse?
Willis
NAXJA Forum User
- Location
- Hoquiam, WA
Goatman said:
I thought your arms were longer, at least in the 20s (for the lowers). I was clearly
. Mark runs 'J' arms right? I'll have to play with the designs a bit, but a mid arm 3 link with 'J' lowers should work pretty good. I have a bit of time before I actually tear into my suspension (lots of time to change my mind again, and again, and....). I still think Beezil's design is a good one that we all know works, and I'm still leaning that way. Thanks all!
Steve
- Location
- Bakersfield, CA
Beezil said:
Never even considered it. I've had the thing twisted up to the max many times while crawling underneath checking clearances and measureing stuff, and I've never noticed any excess pinion angle in that situation. One reason may be that when I shortened the housing I set the pinion angle to point straight at the t-case with 5* of castor, plus it's high pinion.
it is risen
ha! ressurection...this is a good one, why'd y'all have to go and scare off the engineers?
people are always saying search this and search that so i did...
a lot of the pics here have since expired...so...
what the heck is a j-link suspension?
how well does tomken's long arm setup work and does it retain the upper arms? how would that work
how well would you guess the full traction setup perfornms in regard to these concerns? i don't think it was out at the time this was written.
btw before anyone rips on me for pulling this one out...it was written about a month before i got my xj, i missed out, sounds like it was a good time
thanks,
mike
ha! ressurection...this is a good one, why'd y'all have to go and scare off the engineers?
people are always saying search this and search that so i did...
a lot of the pics here have since expired...so...
what the heck is a j-link suspension?
how well does tomken's long arm setup work and does it retain the upper arms? how would that work
how well would you guess the full traction setup perfornms in regard to these concerns? i don't think it was out at the time this was written.
btw before anyone rips on me for pulling this one out...it was written about a month before i got my xj, i missed out, sounds like it was a good time
thanks,
mike
