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Advanced Fabrication and Engineering For when your build is going off the charts. Wildly modified vehicles and straight up buggies welcome.

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  #1  
Old September 12th, 2009, 18:18
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Lower shock mounting options

I am running a radius arm suspension. When you go to full flex, the shock, that is mounted by a bolt parallel to the axle, is really bound up. As the axle tilts, the shock bushing is crushed. The bushing can literally limit the droop due to this angle.

I am going to make my problem worse because I am going to allow more flex due to a wristed radius arm and a 12" shock. I have been brainstorming to find a simple answer. I can only think of two. I could use a BPE and allow the BPE to rotate in it's mounting hole on the radius arm, or I could angle the shock mounting bolt back at a 45 degree angle. This angle would split the deformation cause by the downward angle on the arm with the twisting action on the arm.

Anybody got any other bright ideas?
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  #2  
Old September 12th, 2009, 19:18
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Re: Lower shock mounting options

how about a shock with a hiem ?
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  #3  
Old September 12th, 2009, 19:49
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Re: Lower shock mounting options

could get some ideas from here
http://www.naxja.org/forum/showthrea...ighlight=shock
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  #4  
Old September 12th, 2009, 20:45
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Re: Lower shock mounting options

OK, shocks with heims would be ideal, but I imagine they are spendy.

Anybody got any links for shocks with heims?
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  #5  
Old September 12th, 2009, 21:11
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Re: Lower shock mounting options

http://www.eshocks.com/bil_ORsb.asp?...=All&SubChar=Q
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  #6  
Old September 12th, 2009, 21:12
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Re: Lower shock mounting options

7100s and similar are all heimed shocks. They are $120+ shocks, which might be more then you want to spend.



Why not rotate the mount 90* and have it mount similar to how the stock shocks mount?
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  #7  
Old September 12th, 2009, 21:45
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Re: Lower shock mounting options

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Originally Posted by Ryan93 View Post
Beat me to it. Thanks!
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  #8  
Old September 13th, 2009, 09:17
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Re: Lower shock mounting options

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Originally Posted by Starboard M View Post
Why not rotate the mount 90* and have it mount similar to how the stock shocks mount?
As the axle articulates, there isn't enough play in the bushing if it is mounted that way. I could actually see the shock rod flex.

I'm not in the position to spend $185 a shock plus shipping.
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  #9  
Old September 13th, 2009, 10:56
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Re: Lower shock mounting options

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Originally Posted by old_man View Post
As the axle articulates, there isn't enough play in the bushing if it is mounted that way. I could actually see the shock rod flex.

I'm not in the position to spend $185 a shock plus shipping.
What's the top mount like? Just stock stem style? Maybe if you had one bolt perpendicular and one parallel to the axle it wouldn't bind. You wouldn't need expensive shocks to try it, but you may have to buy a pair of eye-to-eye shocks.
Billy
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  #10  
Old September 13th, 2009, 11:47
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Re: Lower shock mounting options

Remember I am running a wristed arm. The axle rotates with droop. Sketch out the geometry. An eye on the bottom is what is causing the limits. The axle droop would ideally have the eye parallel with the axle, but the flex would ideally have the eye perpendicular with the axle.

The mounting point does not simply go up and down in a vertical straight line. The mounting point swings through an arc for the flex with the center of the arc the mounting of the track bar and a different arc at 90 degrees for the droop, centered on the frame attachment of the radius arm. Parallel mounting compensates 100% for the drop and zero for the flex, while perpendicular mounting compensates 100% for flex and 0% percent for droop. Mounting them at 45 degrees would compensate at least somewhat for both.

After looking at it, I may try and fab a bracket that mounts to the short axle side of the wristed arm to help compensate since if drivers is stuffed and the passenger side down, the short side will stay more horizontal putting less bind on the shock eye. But I guess then I will have the opposite problem. The binding will happen at full stuff.

For the moment I am just going to fab it up parallel to the axle and on top of the arm and keep my 10" shocks. I have another radius arm that I will play with setting the attachement at a different angle and lower on the arm for the 12" shocks. Another issue is that if I lower the shock mount on one side, the modified side, I also have to move the shock down on the unmodified side to match.

After being in the business for 35+ years, I guess I should remember that engineering is finding the best set of trade offs.
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  #11  
Old September 14th, 2009, 09:51
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Re: Lower shock mounting options

The fore/aft movement caused by the arc of the arm travel should be less (Esp with long arms) than the side to side movement/arc caused by the axle articulation.

I think the ideal setup is a double-eyed shock with the the top eye parallel to the axle tube and the bottom eye perpendicular to the axle tube.
I do like the creativity of where you're going with the 45 degree idea though...

(disclaimer: This is all based solely on what i have observed on the trail about the behavior of a link suspension. I'd love to see some actual calculations, but it's Monday and I can't muster the motivation to do this myself.)
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Old September 14th, 2009, 09:52
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Re: Lower shock mounting options

Tom, it sounds like you've already figured every possibility. The only thing I see to do is figure which is the least deflection, horizontal or perpendicular to the axle tube, and then mount the shock that way. Don't overtighten the shock nut against the bushing so it can move without binding and go for it. Mounting the shock on the side of the control arm mount is a good option, mine on the XJ are that way.

I had to mount my shocks a little more outward, since the shock shaft would hit the frame when fully flexed out on the droop side, and would bend the shaft slightly, but I never had a shock shaft bend just from maxing out the bushing deflection.

Don't over think it..........it's been done before.
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Old September 14th, 2009, 09:55
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Re: Lower shock mounting options

BTW, the top mount has nothing to do with how much the bottom mount deflects. How the top is mounted makes no difference to the bottom at all. The top is always held in the same position on the frame regardless of the type or orientation of the mount.
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  #14  
Old September 14th, 2009, 12:17
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Re: Lower shock mounting options

Quote:
Originally Posted by David Taylor View Post
how about a shock with a hiem ?
Read my mind...
Quote:
Originally Posted by old_man View Post
OK, shocks with heims would be ideal, but I imagine they are spendy.
I'd consider fabbing some up, or at least building some adapters that'll make it possible. It seems to me that adapting the stem end of a stock front shock would be almost trivial, get some small heim joints, chop the stems on the shocks down, tap holes into the ends of a short chunk of bar stock and install it. I'm not exactly sure how I'd deal with the bushing+pin end... need to think some more.

EDIT: got it, maybe... connect the ball end of the heim joint to the shock's bushing end via a bolt and some spacers, connect the thread end of the heim joint to the axle.
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Last edited by kastein; September 14th, 2009 at 12:22.
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Old September 15th, 2009, 13:36
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Re: Lower shock mounting options

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Originally Posted by kastein View Post
Read my mind...


I'd consider fabbing some up, or at least building some adapters that'll make it possible. It seems to me that adapting the stem end of a stock front shock would be almost trivial, get some small heim joints, chop the stems on the shocks down, tap holes into the ends of a short chunk of bar stock and install it. I'm not exactly sure how I'd deal with the bushing+pin end... need to think some more.

EDIT: got it, maybe... connect the ball end of the heim joint to the shock's bushing end via a bolt and some spacers, connect the thread end of the heim joint to the axle.


Disneyland stuff......sorry.

By the time you go through all of that, and buy the heims and whatever other taps and parts you need, you can buy the 7100's or whatever else with the heim ends.
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