[jim martin]

thanks guys i just had to make sure I'm not missing something .glad to know I'm on the correct path .
thanks for the ideas relating to flex , never considered that .
you have given me a fantastic idea that i will incorporate into the inner heim joint bracket .
what i will do is instead of having one 3/4" hole for the bolt to pass through I will make it a small 3/4" vertical slot that will allow for slight camber adjustment as required due to flex .

mike , did you by chance measure your camber before the vehicle was taken off the stands and after it was on ground and under its own weight ?
would be interested in the camber change due to flex if you experienced any

 

[Mike Lawless]

Yep. I put in a little over one degree at ride height. Sitting on the ground with full weight on it, it's just a little over zero. Maybe .2 or .3 degree.

If I have it sitting lower, say 3/4" from where I set it up, then it goes to .2 or.3 degree negative. Still in the ball park.

If you do the slotted hole, make sure you can tighten the livin' sh!t out of the bolt so it don't slip. You'll still have forward force applied there when you drop the clutch

 

[AaronP]

very good info here ..... Thanks for the write up and a great job on the fab work always nice to see someone doing it in the garage

Aaron

 

[Billyisgr8]

Jim check out how this rear trailing arm was mounted up with the adjustable inner mounts.

Kevin

[img= width=600 height=450]http://i211.photobucket.com/albums/bb3/gavinsimba/3-17c.jpg[/img]

 

[jim martin]

in between drywallers and movers i snuck outside for 15 min for a look before i pulled the test arm and start Assembly of the final arm.

when i was laying in my test tubes for a final placement check , something jumped out at me .
why do i need to bring a short section of pipe out connected to the heim joint at the same angle as the stock IRS arm ?
why not eliminate the short piece of tubing at the stock IRS angle and bring it into a straight line with the tubing .??
as well i could have 1 tube directly insert into the heim joint and the top tube notch into that tube , easier.
looks like a way simpler setup .
sorry Mike used your picture for demo .
you can see in the main image the yellow tube is now in a straight line with the heim joint [ red and black],this eliminates the short section of tubing

the top illustration kind of shows what i was thinking how 1 of the 2 diagonal tubes would have the heim joint directly in line with it and the other tube just notches into it .

now I'm no way a chassis fab expert or a suspension geometry expert so if anyone has any input on my idea ,please let me know your thoughts

 

[Fiatdude]

That was the way my arms were set up -- but I wish that I had squared the ends -- the reason for that is I would of widened the brackets and put in shims on both sides -- that way, if necessary, I would of been able to move the arms in and out a little -- just a little more adjustability

 

[Jerry Spearn]

looking at Mike original picuter and then looking at your what I see is, Mike and move the trailing arm forward or rearward in the chassis square in relation to the centerline. By changing it to look like your arm moving the arm for or aft square with the centerline would require a LOT mor work.

 

[jim martin]

i see your points on moving for/aft .
taking that info i did a little testing on paperwork to see what happens to the inner pivot point .
what happens is the diagonal arm when moved straight back moves toward the inner side of the bracket .
what i would then need to do is wind the heim joint out to get the bolt position back .but more important
is to have the bracket wide enough that will allow for shims /washers to be moved from the inner to the outer side to compensate .

 

[Mike Lawless]

Build your diagonal arm straight like you suggest, then move the completed arm throughout it's travel and watch what happens at the rod end. Now on my photo, draw a straight line from one rod end pivot center to the other. That is the reason for the "stub" that the diagonal is attached to. Even then, it's still a compromise when the stock torsion housing is used to locate the pivot points. But for three inches of suspension travel, it's not too bad.

It's a really good thing that you are asking the questions, because there's more than one way to "skin a cat." Maybe you can come up with something no one has thought of before

I didn't make it the way I did by accident. What I ended up with is pretty far removed from my initial design I had on paper. Keep going Jim. I'm very interested in what you come up with. If it's better than mine, I'll steal your design fair and square and re-do my own arms!

 

[jim martin]

Build your diagonal arm straight like you suggest, then move the completed arm throughout it's travel and watch what happens at the rod end.

-- good idea ,might as well modify the test arm 1 more time . will take some photos and measurements of both setups as well as camber and toe-in changes from both setups and see what happens .
should be interesting .

Now on my photo, draw a straight line from one rod end pivot center to the other. That is the reason for the "stub" that the diagonal is attached to. Even then, it's still a compromise when the stock torsion housing is used to locate the pivot points. But for three inches of suspension travel, it's not too bad.

care to elaborate a bit on that Mike ? i played with your photo again and i must be missing something obvious

and Mike ,thanks for your input !!

 

[Brian Sanders]

care to elaborate a bit on that Mike ? i played with your photo again and i must be missing something obvious

and Mike ,thanks for your input !!

My guess is the heim joint is going to bind OR come close to binding on the heim bracket? Mike?

 

[Mike Lawless]

Correct Brian!
Even with the way they are now, the rod end housing don't stray straight in line. It rotates and comes close to touching even the way it is.

 

[jim martin]

thanks will watch for good joint alignment .
looks like the 1st big problem is my shock position .with the diagnal arm with the stub arm it allows for a steeper angle
and clears the shock which is tucked in close to the hub and spring plate .will still finnish the test arm and see what
options it leaves for shock position.will get a photo up this weekend

 

[jim martin]

boy that was a long weekend , house Reno's come first .thank god there done .
back to work in the shop .
as discussed had decided to put a spin on the control arm ,using a new design as discussed .
well it worked out better than i thought and was pleased with the arrangement .and after looking at it a bit i decided i would also move the control arm mounting to the other side of the spring plate and gain even more room for the shock .shock position will be fine in the end .
Mike was correct and watching the heim joint move is very important as as the arm travels up it rotates sideways and can actually allow the inner ball to spin into the outer heim race .a bit of preplanning and there will always be full contact within the heim joint .
couple of notes as i have done allot of testing and come up with a few points relating to the inner diagonal arm pivot point .
- raising it up or down slightly will change the camber .
- moving it closer to the spring plate increases the camber change and toe in through the range of travel and farther away from the spring plate decreases the camber change and toe in through the range of travel .
- moving it above or below the torsion tube keeps the same camber change through the travel range but either pushes the hub out or pulls it in relating to the same arc of when the pivot point was in the centre of the tube .

these shots will give you a rough idea how it fits .
[img= width=600 height=450]http://www.dialedinperformance.com/images/busbox/PICT0473.jpg[/img]
[img= width=600 height=450]http://www.dialedinperformance.com/images/busbox/PICT0475.jpg[/img]
i was 100% sold on this setup until i realised pulling the bolt out is going to be a problem
so looks like i may have to scrap or partially scrap this arm and use a combo of this arm and a short stub at the end at more of a angle as originally designed
[img= width=600 height=450]http://www.dialedinperformance.com/images/busbox/PICT0477.jpg[/img]

 

[shag55]

This is some good info as I want to do this on my Ghia though I would like the arms as long as possible but stay outside the pan. As I plan to raise the trans 1" and framehorns 2- 3" I will have to deal with it a little diff. I don't know if coil overs or torsions will be on my list as of yet.

 

[jim martin]

i,ve just started cutting out the bearing plate material and have actually made yet another change that should make the overall assemble , stronger , lighter and just plain simpler .it also allows for tons more shock room and allows for even easier adjustments .will get images up when i fit the first bearing bracket assemble together

 

[shag55]

What shock length are you going for and where will you start spring wise? 350-450# if I go coil over I will use the QA-1s promostar just need the length they have a 11", 12.5", and 14" probably the 12 or 14 will be better 3-4" total travle and more spring options. These are valved for the front of a v8 so should be close. I will opt for the doule valve adjusters.

 

[Mike Lawless]

When you're building your own stuff, you can pretty much use whatever shock fits in the space.

I ended up with my lower shock mount much higher than stock so that I could bring it as far outboard as I could go and keep it out of the way of the CV joint. I just couldn't make it work with the shock in the semi stock location without making compromises on the trailing arm design. I thought it would become too flexy or too heavy if I worked around the shock. I was able to make 'em stiffer AND lighter by working the shock mount around the arm instead. Also if the lower shock mount is too far inboard, you'd need stiffer springs to deal with the leverage factor. Which brings in another factor. If the spring needs to be much more that 500 lbs, springs are only easily available in shorter lengths, like 7".

 

[DLX-Fe]

I havent look back at this thread but what about custom length irs axles? where, who and how much?

thanks
Doug

 

[Mike Lawless]

I got mine through Mark Williams. I also understand there are others out there who make a custom length IRS axle. Rancho could probably provide axles through one of their suppliers. I have heard that Sway Away makes 'em and a place called KarTek in so cal somewhere. The beauty is that you are not limited to either 3" per side or 5" per side.

Mine were fairly pricey at $800. But it's something I'll never have to worry about.