CK5 - The Full-Size GM Off Road Community

OK Guys,

That last discussion thread was GREAT! I appreciate all the input so far. From my research and experiments, it's becoming clear that a "panhard bar" based solution is going to have some limitations. So I'd like to put that solution aside for a while and explore another design that could potentially solve the "axle shifting" issue....

Wishbone-based Lower Link(s) -

I think this is considered a "4-Link" technically speaking, but it may still have merit depending on how I/we can solve the binding issues.

My current thought is to take the last design of the links (the ones where they are offset from the axle 8" vertically and parallel to the ground) and add a lower wishbone to that design. Here's the NEW pic:

http://www.norcalbigdawgs.net/Gallery/albums/albun65/Wishbone_front_view.jpg


Now I've got a few more to share too.... (it's been a busy weekend)

http://www.norcalbigdawgs.net/Gallery/albums/albun65/Wishbone_front_angle.jpg

http://www.norcalbigdawgs.net/Gallery/albums/albun65/Wishbone_from_above.jpg

http://www.norcalbigdawgs.net/Gallery/albums/albun65/Wishbone_Side_view_2.jpg

http://www.norcalbigdawgs.net/Gallery/albums/albun65/Wishbone_Side_View.jpg



The setup shown here has about 129% anti-dive. The lower links are 46" long, and the uppers are 32". This setup has a LOT of uptravel (close to 12"!) though I'll be limiting that to probably 8".

The nice part about this setup (from what I've seen so far) is that the axle-shifting that happened with the previous panhard bar setup is very minimal....about 1" at full stuff! That's substantially better.

Other issues, like driveshaft and steering still need to be worked out....but since this is all "experimental" at this point, I'm not going to do much with those except take a look at whether they look do-able or not. So far, they look OK.

I've spent a lot more time in front of the PC, doing calcs and understanding the geometry....that's why there doesn't seem to be as much "progress" in the photos lately! /forums/images/graemlins/tongue.gif

[ QUOTE ]
At this point, I'm unclear whether the wishbone would be better with the convergence point under the tranny pan (roughly) or converging under the front axle??


[/ QUOTE ]

Greg,

From an analytical standpoint, you only have one choice here... that is to have the converged end of your wishbone at the tranny. Reason is... if you converge it under the axle, then this point defines your roll center for the front suspension and you don't want your CG that far above your roll center.. .or it's always gonna want to flop over! /forums/images/graemlins/blush.gif

From a practical viewpoint though.... I've seen a couple of rigs that have acutally made this setup work with the converged end at the axle. Walker Evans ran something like this on the front of his S-10 Comp buggy for a while, but then he went on to other things (like IFS.. /forums/images/graemlins/rolleyes.gif)... Probably the most successful rig I've seen run it is a little orange 1 seater buggy built by FourWheeler's here in Phoenix.

Still these examples of making it work have all been light buggies, and I think it would be tuffer on a fullsize to get away w/ it...

Marv

Gotcha!

From a purely "wild guess" I was thinking it needed to converge under the tranny....just needed to be reminded "WHY" again.... /forums/images/graemlins/thumb.gif

I'll be drawing some of this up on graph paper and applying a few calcs for roll center, instant center, etc. And let those numbers help to guide me towards the mounting points and angles I should be using... /forums/images/graemlins/deal.gif

One more quick question:

When solving this equation, is Theta expressed in "degrees" or some other unit of measure (radians?, etc)


http://www.norcalbigdawgs.net/Gallery/albums/album73/Anti_Dive_image.jpg




/forums/images/graemlins/ears.gif

Who Are You???
What did you do with my Buddy Greg??
Give him BACK!!!!!
hahhaaha
J/K /forums/images/graemlins/usaflag.gif /forums/images/graemlins/ignore.gif /forums/images/graemlins/ignore.gif

Greg sorry I have to ask but what are your design goals? Like street and offroad or trail only rig? I think that we are making the panhard rod out to be way to difficult. Look at all the front ends that use them like the Dodge truck, jeeps and Landcruisers I don't think it is that hard. /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif

x

[ QUOTE ]
go limit your 3 link susp travel to the 'possible' and see how bad your PHB shifts the axle.
it seems like you are looking at the extremes and panicing

[/ QUOTE ]


Not sure I'd use the word "panicking"....really the first discussion thread got me a pretty solid understanding of how the panhard bar works, and that (like all things) it has some weaknesses as well as strengths.

That is not to say I have abandoned it as a solution....I'd really like to explore the triangulated lower links with the same "skeptical eye" and see what weaknesses it has, and what strengths it offers....

Ultimately, the decision about which solution is best will come down to the one that has "weaknesses" that I can either live with, or plan-around. Or maybe it will simply be the one that lets me fit all the "other" stuff into the equation too (driveshaft, idler steering /forums/images/graemlins/thumb.gif, etc) The best suspension design in the world won't help me much if I can't connect any steering linkage.... /forums/images/graemlins/grin.gif

As for a "real" objective....how about a suspension that can do between 7" and 8" of bumptravel (up) and a similar amount down? That would put me in the 14" to 16" shock realm and would be a significant improvment over the roughly 5.5" of bumptravel I currently have.... not that this is the PRIMARY reason for the suspension change. As most of you already know, I am enjoying the challenge of it all....the planning, the calcs, the fabrication. This is the essence of the "Built Not Bought" philosophy to me. /forums/images/graemlins/thumb.gif



Besides.....I just KNOW that you guys want to see some photos of an articulated wishbone suspension to compare to the panhard bar stuff I've already done..... don't you?? /forums/images/graemlins/deal.gif

Theta is in what ever you want it to be...just make sure you have your calculator (or excel) in the right mode to make it what you want.

And how exactly would you steer this?

Triangulating the front can work OK but the packaging is weird and the steering is really weird. We put a panhard on my bro's buggy even given a wide open sheet of paper. Triangulating the front got caught between the roll center requirements, the front driveshaft on the high pinion axle, the belly clearance, etc. And this is not even considering steering since it's using hoses instead of linkage.

Put a panhard bar on it and be done. That's my call, it does work OK, I'm down to about 14" of travel now and the panhard works fine. It's a little funky to get it all in there but it works. Steering is where the triangulated front becomes a problem.

[ QUOTE ]
And how exactly would you steer this?

Triangulating the front can work OK but the packaging is weird and the steering is really weird. We put a panhard on my bro's buggy even given a wide open sheet of paper. Triangulating the front got caught between the roll center requirements, the front driveshaft on the high pinion axle, the belly clearance, etc. And this is not even considering steering since it's using hoses instead of linkage.

Put a panhard bar on it and be done. That's my call, it does work OK, I'm down to about 14" of travel now and the panhard works fine. It's a little funky to get it all in there but it works. Steering is where the triangulated front becomes a problem.

[/ QUOTE ]


Two words......Rope Steering!!


...just like the old wooden go-cart I built as a kid! /forums/images/graemlins/pimp.gif



In all seriousness, I didn't know if the rest of the stuff would "fit".....mj has me thinking about a really weird-sounding "front to back idler arm steering" setup, that seemed to move a lot of the stuff out of the way.

This image was posted up in the OTHER 3-link thread:

http://www.norcalbigdawgs.net/Gallery/albums/albun65/idler_arm_steering.jpg


Anyway, I'm not sure if that will solve the packaging of the steering setup. Maybe once I start actually laying in the wishbone on my "mock up" it will become obvious that I can't fit everything.... /forums/images/graemlins/thinking.gif

Greg, your steering drag link that runs from the idler to the axle needs to have it's pivot points in the same planes as the pivot points of the suspension link it is running parallel to. If not as your suspension cycles your steering wheel will be doing all kinds of fun stuff...

I think your best bet is going to be a regular crossover setup with a panhard bar running parallel and the same length as the drag link and mounted in the same plane vertically and horizontally as the drag link when steered straight ahead...

In case your intrested in the October 4 Wheel & Off-Road mag, page 96 "Tube Car K5" looks to have a front 3 link very similar to what you have mocked up.

Greg there was that same steering setup on one of the Avalanche rigs. It was on there website before the two companies spilt. Maybe you could Ask Clifton at Poison spyder about that setup.

Thanks for the tip.....I will try a little "sleuthing" to see if I can find any pics.

Anyone familiar with PBB feel like looking over there? /forums/images/graemlins/thumb.gif

I take it your in the pbb band? /forums/images/graemlins/rotfl.gif

I have gotten all my knowledge on this stuff from there and thats reading maybe 5% of the posts on the subject over there... I've got a thread going right now over there on my rear 4 link design and I don't know what I would do without all the help from them.

Heres the latest:

http://www.industrialoffroad.com/gallery/albums/album06/pcc_susp5.jpg

Jason,

I can still "lurk" over on PBB, it's just that I spend so little time there that I don't even know which forums are the most useful (for tech).... mostly it looks like a lot of "flipoffs" and "fag comments"....

Anyway, that suspension diagram is GREAT! I followed the link back to your site, and grabbed the other ones there too (the early designs perhaps? /forums/images/graemlins/wink.gif) Being able to compare the link positions you chose, and the effects that those choices have on the IC, roll centers, and anti-dive are going to be a great learning tool for me.

BTW -> What are you using to draw those? Is it some multi-thousand dollar software I'll never own, or maybe something a little more "wallet-friendly"???? /forums/images/graemlins/grin.gif

Thast autocad 2004, runs in the neighborhood of 3,728.39

Here is the entire thread:

http://www.pirate4x4.com/forum/showthread.php?s=&threadid=173230

The General 4x4 Discussion forum is by far the best for general tech like this, it's pretty much the only one I hang out in other than the chevy forum but it's not heavily traveled.

Everyone always complains about pbb and how harsh everyone is but if you make a nice post and don't ask stuff like how much stronger did the chrome plating make my diff cover you'll be ok /forums/images/graemlins/rotfl.gif

Interesting you mention Zach's tubecar K5, it's a pretty well executed rig overall. The front suspension would be a good one to study, it works well. I've had a ride in it and it handles pretty well at high speed (60+ sideways in a sandwash felt good) and he has it tuned to the gnat's ass for climbing steep slickrock.
Your front to back idler steering isn't a bad idea, the best setups I've seen like this run the steeringbox under the seat and either use a "V" drive box to redirect the shaft, or in Randy Ellis's "toy" jeep he basically ujointed the shaft around the corner.
Watch tire clearance to your idler, my link arms run under the frame and get hit HARD by the tire. This is with a 42 on 5" backspace. You'll also need to pay close attention to the idler angles and lengths to make it all happy, and I can tell you that multiple draglinks like that can introduce a good bit more play and it had to have added a good bit of weight on my truck and will on yours too.

Once again, I'd encourage a relatively simple panhard bar using the crossover steering you already have. RED's conversion on Juan's K5 would be a good example to look at also.

A few days perusing the PBB would be well spent, there's plenty of good tech and creative thinking there, you just have to sift it a bit. I guarantee all this has been covered there at some point in time.

TTT - New pics and commentary are now in the opening post. /forums/images/graemlins/thumb.gif

Are you going to articulate that new mockup today? I'm getting eager to see your results. I suppose your going to mock up the wishbone as two sepperate links mounted on either side of the tranny pan as a last test? I ask because having a single mount for two beams makes you twice as likely to be stranded if that one joint breaks, having two and breaking one means you still get back to camp.

[ QUOTE ]
Are you going to articulate that new mockup today? I'm getting eager to see your results. I suppose your going to mock up the wishbone as two sepperate links mounted on either side of the tranny pan as a last test? I ask because having a single mount for two beams makes you twice as likely to be stranded if that one joint breaks, having two and breaking one means you still get back to camp.

[/ QUOTE ]

But Mike....I did articulate it. /forums/images/graemlins/smile.gif

......are you saying you want to SEE the pics???


I'm trying to build suspense here. /forums/images/graemlins/deal.gif

Hahah - tou·ché /forums/images/graemlins/thumb.gif

That is the idea I have been working with all along, but I have the upper links directly under the frame rails so they won't hit the rails when you twist it up good. My questions are: Is it gonna work with the driveshaft? How about the oil pan getting in the way? Is the exhaust gonna be in the way? As far as binding, take a look at Steve Frisbies rear wishbone and look at the swivel he put in that one. I think that would solve the binding. I took a pic at Indy last year, I will see if I can find it and post it for you.

[ QUOTE ]
That is the idea I have been working with all along, but I have the upper links directly under the frame rails so they won't hit the rails when you twist it up good. My questions are: Is it gonna work with the driveshaft? How about the oil pan getting in the way? Is the exhaust gonna be in the way? As far as binding, take a look at Steve Frisbies rear wishbone and look at the swivel he put in that one. I think that would solve the binding. I took a pic at Indy last year, I will see if I can find it and post it for you.

[/ QUOTE ]


Upper links under the framerails - Might work if you put the link right where the frame transitions from flat to the curve up towards the engine. Longer links would end up slapping the frame on compression...Putting the upper links inboard of the framerails (but mounting towards the outer edge of the axletubes) is also "slap-city" /forums/images/graemlins/grin.gif on the frame. I did a lot of early layouts with that problem before settling on having those upper links completely out-board.

Driveshaft - So far it's looking OK. The front shaft is REALLY long due to the doubler and long tranny (4L80E) especially since on the 1st Gen the TH350/NP205 combo that came standard was pretty compact as a setup. The guys that are used to NP241s and NP208s don't face the same length penalties going to a doubler. I may end up with a 2-piece front driveshaft as a last resort....

Oilpan / Trans - Oil pan will probably be OK. The "V" is giving good engine clearance currently. The transmission might normally be an interference point on this design, but mine is mounted about 5" higher than normal to get the "flat bellypan" I want. /forums/images/graemlins/cool.gif That means there's more room for the rear bracketry and room to pivot before things hit.

Exhaust - Will be tough, but not impossible. I've given up on a true "dual" setup. I will collect the exhaust onto the driver's side (driveshaft on PS makes things too tight) and run a large singe exhaust. Should be better for low end torque anyway....



/forums/images/graemlins/thumb.gif

Pics of new setup......articulated! /forums/images/graemlins/thumb.gif

http://www.norcalbigdawgs.net/Gallery/albums/albun65/3_link_articulated.jpg

http://www.norcalbigdawgs.net/Gallery/albums/albun65/3_Link_Any_Axle_Steer.jpg

http://www.norcalbigdawgs.net/Gallery/albums/albun65/3_Link_both_sides_drooped.jpg

http://www.norcalbigdawgs.net/Gallery/albums/albun65/3_link_drooped_3qtr_view.jpg



A few observations:

- Top view shows almost NO axle steer, especially when compared to the previous panhard bar setup.

- Axle shift is minimal. I can see roughly 1"...maybe 2" of shift at the ludicrous angles I photographed at. However, I am also at the point where my "pretend" rod ends are allowing for enough "slop" that accuracy within +/- 2" is probably the best I can estimate anyway.

- I like this setup so far. There are still variations that I'm interested to try, and I have to spend more time REALLY understanding the packaging of the steering system, shocks, exhaust, and front driveshaft.....before I get TOO excited about anything.

Anyway, just thought I'd share for those who are still interested in this thread. /forums/images/graemlins/thinking.gif

Whats the angle between the lower links? For locating I would like at least 40* there...

[ QUOTE ]
Whats the angle between the lower links? For locating I would like at least 40* there...

[/ QUOTE ]

I'm not sure on the lower angles....I haven't done a calc on that yet.

The seperation is roughly 36" and the length is ~46". I still have some room left if I need to stretch a dimension one way or another. What makes 40* so magical? I'm assuming it helps keep the loading of the links reasonable, while providing a strong "locating" effect for the axle.....?


FUN STUFF, eh? /forums/images/graemlins/cool.gif /forums/images/graemlins/thumb.gif

Ok I see your objective but you have some serious missing componets.

You have to have the pumpkin and drive line in there for mock up. As I see this set up all your passengerside mounting point are in the way of the pig and driveshaft. The rear I can see this set up work working but not the front with the diff offset. The diff is going to define your available mounting points.

Personnaly I would stick with a proven design. Top control arms near center of the of axle to take care of the clearence issues on driveline and track. Outer control arms a couple inches below the axle centerline. If you spread the top control arms some it will help with the crazy stear issues you will get. Other option is a torq arm dead center and a track bar with outboard control arms.

Other option is take a page from ford (yes I said the f word) Radius arms a little inboard and above the axle center line and make them long and if you triangulate on the axle and curve the arm for tire clearence when the wheel is turned so you can move to lower mount out towards the hub and again a track bar. You might even get away with nothing below the tube just a small tower that will handle the axle torque.

Try to keep the track bar in close to the same plane as the drag link. Yes the axle will offset some as the axle drops BUT with the drag link close to parrallel to the track arm your not going to have any weird steering issues. It will steer just fine but the axle will not center on the frame if the axle is crossed up. Remember this will be low speed so it's not going to be noticable from a drivers stand point. It's not bombing at high speed where track issues are going to caus you problems.

[ QUOTE ]
http://www.norcalbigdawgs.net/Gallery/albums/albun65/3_link_drooped_3qtr_view.jpg


[/ QUOTE ]

Greg,

Unless you are going full hydro steer, I think the "V" link is not adequate to sustain the lateral forces that you'll put on it... Especially at those 20*-ish angles (just guessing... /forums/images/graemlins/ignore.gif).

.... but WTF do I know /forums/images/graemlins/grin.gif.

Marv

[ QUOTE ]


.... but WTF do I know /forums/images/graemlins/grin.gif.

Marv

[/ QUOTE ]



From everything I've read, I'd say a LOT..... /forums/images/graemlins/thumb.gif (.....and probably a lot more than you let on.)



Grimmy, Marv and everyone else:

This is exactly the discussion I want to keep having. I don't have a LOT of money tied up in this "mock up" so changes are easy and don't hurt my feelings. The pumkpin is a BIG variable that I have not been paying attention to much...maybe I need to create some sort of "mock pumpkin" to use up that space so that interferences will be more obvious???



/forums/images/graemlins/thumb.gif

Find the centerline of the diff Build a pyramid out of some scrap to represent the diff. Try and get the pinion where it would be stock so you can watch those angles as well.

In an ideal world the the pinion angle (to the drive shaft) would stay at near zero (with a CV) as the suspension cycles. That aint going to happend but what you dont want to happen is the angle to get so far out of whack that it causes you other issues. Also you need to concider if your going to run a long spline or a standard spline drive shaft. If your going to run a standard spline then your control arm lenghts are going to play a big part in keeping the slip joint from over extending and Bottoming out. In a perfect world they it would only need about an inch of travel but that aint going to happen. THe closer the piviot points on the control arms ar to the centerline of the CV the less slip joint is needed.

I would also mock a knuckle on there. Just a straight peice of pipe at the caster angle you want to run. Idealy if you planning to use a bone stock axle you want to set those demisions the same. Idealy you would cut and turn the knuckles once you get the pinion where you want it but you talking a lot of extra work to do that.

Reguardless you need to concider both pinion and castor angles as your mocking up.

You also need to figure out where your base ride hight will be and work from that as a starting point. If this is going to be a street going vehicle your caster and pinion need to be right for what it will be doing on the street first.

Hmm, looks a lot like our rear link setup, which works really well. But doesn't steer and has a centered diff.
I'd look to mock up a complete housing with a knuckle on it so you can put a tire on and steer it. Actually that's what we do, and it works well. So many of your critical dimensions are hard to represent on a model that you might as well use a housing.
For example, I think your tires have a good chance of hitting that upper link. Not a for sure thing since they're pretty high but maybe. You also need to mount a shock and spring somewhere, if you're going to use coilovers, you're pretty much out of space unless you mount them on the upper link arm.
The lateral locating linkage needs to be really beefy, it's hard to get ideal angles because of the width of the d60 axle so the parts are going to have to be really stiff and strong to keep the front located side to side. Luckily with this setup your steering forces are going to be front to rear so you're not going to be shoving the axle sideways with the steering box, but just the vehicle weight will put a lot of stress on it.

Greg,

http://bbs.off-road.com/photobb/data/576/21_025-med.jpg

I had mentioned in an earlier post that having the "V" converge at the bottom of the axle was a no-no... But alas, here's another example of someone running just that.... this time on the rear.

Not sure how it works... /forums/images/graemlins/confused.gif

Marv

[ QUOTE ]


In all seriousness, I didn't know if the rest of the stuff would "fit".....mj has me thinking about a really weird-sounding "front to back idler arm steering" setup, that seemed to move a lot of the stuff out of the way.

This image was posted up in the OTHER 3-link thread:

http://www.norcalbigdawgs.net/Gallery/albums/albun65/idler_arm_steering.jpg


Anyway, I'm not sure if that will solve the packaging of the steering setup. Maybe once I start actually laying in the wishbone on my "mock up" it will become obvious that I can't fit everything.... /forums/images/graemlins/thinking.gif

[/ QUOTE ]

Greg

something for you to look at on the front steering. there is an f700 at my farm doing some logging, and it has the front to back arm like you were saying. might want to check one of those out.

also just kill a basketball and slide it on the pipe for your mock pumpkin.

nathan
69k5

[ QUOTE ]
[ QUOTE ]


In all seriousness, I didn't know if the rest of the stuff would "fit".....mj has me thinking about a really weird-sounding "front to back idler arm steering" setup, that seemed to move a lot of the stuff out of the way.

This image was posted up in the OTHER 3-link thread:

http://www.norcalbigdawgs.net/Gallery/albums/albun65/idler_arm_steering.jpg


Anyway, I'm not sure if that will solve the packaging of the steering setup. Maybe once I start actually laying in the wishbone on my "mock up" it will become obvious that I can't fit everything.... /forums/images/graemlins/thinking.gif

[/ QUOTE ]

Greg

something for you to look at on the front steering. there is an f700 at my farm doing some logging, and it has the front to back arm like you were saying. might want to check one of those out.

also just kill a basketball and slide it on the pipe for your mock pumpkin.

nathan
69k5

[/ QUOTE ]

Interesting concept. I think that's simular to hof FJ40's are. FJ Crowd convers to cross over.
I think there is also a issue of that may be in the way of the tire full left lock.

With a link suspension not much is in the way of cross over except maybe a drag link. That's really doing things the hardway to run it down the frame. I think that unless you run a really long arm it may suffer some of the same bind up issue ths stock set up has. .

If I read those lengths right he has 46* included btwn the 'A' link tubes. Due to buckling, even triangles get flimsy if the lengths get too large. The cure is to triangulate within the whole 'A' part to reduce the effective length of each tube. Easiest structure is to run a tube from each intersection to the middle of the opposite tube. That divides all of the tube lengths in half. That middle interesection will be a might busy though. Some variation on the theme is called for.

The link that does the lateral location determines the height of the roll center (RC). The further away from the CoG the RC is, the more body lean/roll the vehicle will have. Makes sidehills more interesting that way. /forums/images/graemlins/eek.gif I'd want the RC as high as is reasonably practical which means moving the lat. location duty to the upper links.

For a pitman swinging front to back in a verticle plane check out the 4wd 3/4t IH trucks. If memory serves they use a Saginaw box mounted to a bracket so that they swing this way. The box itself won't care, other than bleeding out the air you could mount one upside down if you wanted. The FJ crowd convert to GM boxes & cross-over b/c their stock system is like the old MB Heep system, two draglinks and a bellcrank. A design intended to have lots of lost motion in it, and it gains more with age.
The front to rear swing in a vert. plane of the pitman arm isn't all that odd. Nearly every truck over 2 tons and OTR's use this design. Bumpsteer will creep in with this design when the draglink isn't parallel to, and the same length as the locating link nearest to the steering arm on the upright. It is possible to make a steering linkage that is not parallel and the same length, but that gets into where the Instant Center is and how it moves as the suspension cycles, and then geometrically designing where the ideal pivot points for the draglink are. A lot of ratios there, it's identical to designing out bumpsteer in a short/long A-arm suspension.

If it is going to be street driven then the castor curve is the most important. I like to see castor gain in either direction from ride height, but I usually am planning on airborne adventures too. For a pure crawler you don't want castor gain in droop because that will make for ugly front pinion UJ angles. (Drof Radius arms look pretty good about here.) Once you have the castor curve you want, then see how much driveshaft plunge you have. Lastly determine the pinion angle.

[ QUOTE ]
Greg,

http://bbs.off-road.com/photobb/data/576/21_025-med.jpg

I had mentioned in an earlier post that having the "V" converge at the bottom of the axle was a no-no... But alas, here's another example of someone running just that.... this time on the rear.

Not sure how it works... /forums/images/graemlins/confused.gif

Marv

[/ QUOTE ]

Does not look like it is working to his advantage. /forums/images/graemlins/rotfl.gif

[ QUOTE ]
If I read those lengths right he has 46* included btwn the 'A' link tubes. Due to buckling, even triangles get flimsy if the lengths get too large. The cure is to triangulate within the whole 'A' part to reduce the effective length of each tube. Easiest structure is to run a tube from each intersection to the middle of the opposite tube. That divides all of the tube lengths in half. That middle interesection will be a might busy though. Some variation on the theme is called for.

[/ QUOTE ]


Thom, just to clarify....the lengths of the two lower wishbone links are the 46" number, the seperation of those links (where they connect to the axeltube) is currently at 32", though there's room to move them to 36" (or more) if needed.


[ QUOTE ]

The link that does the lateral location determines the height of the roll center (RC). The further away from the CoG the RC is, the more body lean/roll the vehicle will have. Makes sidehills more interesting that way. /forums/images/graemlins/eek.gif I'd want the RC as high as is reasonably practical which means moving the lat. location duty to the upper links.

[/ QUOTE ]

I haven't actually gotten far enough into all the calcs to do a roll center calculation. I'm currently creating an Excel spreadsheet that can now do IC, Anti-Dive and some other nice stuff....currently it's only drawing a side-view of the suspension. I believe that calculating roll centers requires data from an "upper view" as well??


[ QUOTE ]




If it is going to be street driven then the castor curve is the most important. I like to see castor gain in either direction from ride height, but I usually am planning on airborne adventures too. For a pure crawler you don't want castor gain in droop because that will make for ugly front pinion UJ angles. (Drof Radius arms look pretty good about here.) Once you have the castor curve you want, then see how much driveshaft plunge you have. Lastly determine the pinion angle.


[/ QUOTE ]

Interesting, I hadn't been warned about caster change by anyone yet.....I will try to keep that in mind also. /forums/images/graemlins/thumb.gif

On the 'A' sides angle:
hypotenose = 46"
y = 16 (current)
y = 18 (possible)

arcsine (16/46) = 20.4*, so 40.8* included (current)
arcsine (18/46) = 23.0*, so 46.0* included (possible)

The wider the base is for a given height, the more stable it will be. That's casual to the most obvious observer. Tall column failure (Buckling) is a danger if the tubes get too long.

Calc'ing Roll Center needs an End view. I think you knew that, brain fade ?

The deal with castor is that some aids in straight line stability. Too much makes for difficult turning. So having castor gain in droop means for a dez racer that the truck is going to be wanting to go straight on landings. As the suspension compress' this goes away until ride height is reached. If it's a really hard hit, then going past ride height starts increasing straight line stability again.

In a Crawler application if you gain castor in droop that points the pinion shaft down. Increasing the UJ operating angle is not a good plan in this app.
The F-100/EB Radius Arm design really has an advantage here. Aside from being simple, it gains castor in bump and looses it in droop. So you get a decent compromise btwn stability at speed and not killing the pinion UJ in droop. You can get this sort of castor curve from a 3 or 4 link design, but youll need to play with it a bit to get there.

One other way to gain straightline stability is to employ the much villian-ified Haltenberger steering linkage. It causes toe-in in droop, which also aids in stability. Haltenberger linkage is the 'Y' linkage that all of the '76-'77 Early Bronco crawler owners are trying to get rid of. It's also found on all TTB equiped Fords, late Heep Wranglers, and TJ's.