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4 Link Materials... Your opinion wanted

I also emailed Watson and here is what he said:

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we're using 1.75 x .375 wall DOM tube for our lower links, threaded direct for a 1 x 1.25 heim on each end. The uppers can vary, thinner tube will work but if we have a possibility of contact we use something thicker. 1.5 x .188 would be fine, even .120 wall would work but it's nice to have it a little thicker for dent resistance. I would strongly recommend using at least .250 wall tube for the lower links, thinner tube would hold the suspension forces but will NOT take the rock strikes that link arms get.
Heim size depends a lot on how the suspension is designed, we use the big ones because of the way the lower links are raised above the axle tube, this increases the stress on the link quite a bit, and we know people are going to bounce on the link arms and it's good to have a strong end. Uppers we use a 3/4 x 7/8 joint because the stress on them is a bit lower and they seldom if ever get touched.
We don't have everything worked out but we're hoping to have our kit priced around $3K, including at least a pair of King dual rate coilovers. We're using triple rates but it's not a requirement. I would guess that you'd have another $500 in installing the kit and the upper shock mount (if we don't have one available yet), the idea with a kit is that it's cheap to install of course. It sounds like starting with our parts would get you a little farther along with the same money.
We have a couple features that would be different, our pricing will be set up around heim jointed HD tube links, the coilover setup puts the shocks farther back in the chassis which leaves a bit more cargo room or room for a back seat, if you care. We're also incorporating multiple mounting points for the suspension so you can tune it in a for what you want to do. It's not set up for maximum wheel travel, you pretty much end up with a 1:1 ratio of shock to wheel travel, so a 16" shock would get you 16" of vertical wheel travel. Having more travel is always good but leveraging the shocks to get more changes the link arrangement quite a bit and it's hard to get more wheel travel than that and keep the ground clearance and rock resistance we have built in.
This is about all I can think of to throw down now, take a look at the pics of my rear suspension in the custom rigs section on our page and my bro's buggy in the "our travels" section under 21 road pics and you'll see what we're doing with this rear suspension.


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Acme (Power Screw) threads are designed to convert rotary motion of a nut to an axial force - Jacking.... Though links are assumed to be 2 force members, they withstand an alternating load - a frequent reversal of compression/tension. Any thread that doesn't bind has slop. That slop will only get worse as it wears/fatigues in this application. /forums/images/graemlins/shame.gif Then the worst thing will happen when you land on a rock... This threaded joint subjected to bending is loading it in the worst way....

Teraflex did this exact thing for TJ's in the 90's..... Their links were known for "clunking"....

Marv

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I agree totally, and no bad attitude detected. /forums/images/graemlins/laugh.gif That's what I meant about the wear/slop comment I threw out earlier, and it's the same concern I've got, which is what lead me to wishing there were some kind of strong rotary joint that could withstand alternating tension and compression.

Also, if the link is relatively rigid, and the screw joint is placed at the top near the bushing (essentially screw in the bushing like a rod end) then the impact should not be very close and bending forces should be survivable, especially when we’re talking a 1” high grade stud. Also, these forces would then be similar to all the rod ends running with a loose jamb nut.

The main thing that makes me consider this further is that Brook has been thoroughly beating on his setup in a very punishing environment with no problems or failures (wear, bending or otherwise) that I'm aware of, even though he has bent those big heavy links. /forums/images/graemlins/dunno.gif For the savings and investment at risk, I’m seriously considering it for a first try at rear links.
 
Wow! I now know more about threads and such than I ever ever thought I would. Phew my brain is now all smashed full. I think I need to lay down or somethin.

Good luck to y'all in the future.

Allan

Oh yea Russ I'm still millin on our discussion yesterday. I think I'm almost ready to have an idea. /forums/images/graemlins/histerical.gif
 
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Acme (Power Screw) threads are designed to convert rotary motion of a nut to an axial force - Jacking.... Though links are assumed to be 2 force members, they withstand an alternating load - a frequent reversal of compression/tension. Any thread that doesn't bind has slop. That slop will only get worse as it wears/fatigues in this application. /forums/images/graemlins/shame.gif Then the worst thing will happen when you land on a rock... This threaded joint subjected to bending is loading it in the worst way....

Teraflex did this exact thing for TJ's in the 90's..... Their links were known for "clunking"....

Marv

[/ QUOTE ]
I agree totally, and no bad attitude detected. /forums/images/graemlins/laugh.gif That's what I meant about the wear/slop comment I threw out earlier, and it's the same concern I've got, which is what lead me to wishing there were some kind of strong rotary joint that could withstand alternating tension and compression.

Also, if the link is relatively rigid, and the screw joint is placed at the top near the bushing (essentially screw in the bushing like a rod end) then the impact should not be very close and bending forces should be survivable, especially when we’re talking a 1” high grade stud. Also, these forces would then be similar to all the rod ends running with a loose jamb nut.

The main thing that makes me consider this further is that Brook has been thoroughly beating on his setup in a very punishing environment with no problems or failures (wear, bending or otherwise) that I'm aware of, even though he has bent those big heavy links. /forums/images/graemlins/dunno.gif For the savings and investment at risk, I’m seriously considering it for a first try at rear links.

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And I forgot to add to my first post that I think some form of Anti-Backlash mechanism is a good idea too. Occured to me after I'd shut down for the evening. A spring loaded type wouldn't solve anything, you''ll need on of the screw-adjuster types.
Try mcmaster-carr for the Acme parts. Not the least spendy, but they have it. May also be worth seeing what mscdirect.com has on their page.
 
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Teraflex did this exact thing for TJ's in the 90's..... Their links were known for "clunking"....
Marv

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Uh yeah. I have one of their suspensions on my daily driver TJ. Knocking/Clunking is an understatement. Major PITA to keep everything greased and tight too. Keeping something greased would be a major concern for me when designing something made from all thread.

As far as links, if you are really concerned with bending them, go to a fabricated design made from moly that has been heat treated. Spendy, but as tough as it gets IMO.
 
Just talked to QA1 today and they have a -16 size end (1x1 1/4") in their X series and retail should be about $70.00 with 76K ultimate load. Throw in a moderate misalignment bushing set and I think you could run them with a poly bushing in the front and have a somewhat reasonably priced link.

Another problem with the tera type arms is that you only take up the rotational forces, not the side to side motion of the link. TJ's have problems breaking mounts off the axle with this type of link and hard use. We're not talking about building jeeps here but the point is the same, you'll be putting that side load stress into the mounts.

Also Tera's modular ends would have enough angular travel to take up all the axle rotation at one end.
 

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