Technical Question concerning heim joints *x2couple pics*

Is your goal to downsize the hole in the bracket that's welded to the axle tube?

In any event, welding that stud to the axle will not be strong enough to support the weight of the car, unless it is very heavily gusseted. Then, I'm not sure the threaded part of the heim will be strong enough to prevent shearing.

 

I see what you are trying to do, but 7/16" Heim is way too small.....5/8" would be bare minimum and 3/4" would be best.
You have to consider the instant shock loads of the axle going over bumps or dropping into potholes or the like.
It would be a lot better if you could orient the Heim vertical so that loads are pushing/pulling on the shank, and not trying to bend it.

I know that in drag car fabrication with a ladder bar, no less than 3/4" and chromoly is ever considered because of the bending load.

 

^^^^x2

 

There is such a thing as a spherical bearing. Same as a heim minus the theaded stud. Comes in all styles you can get heims in I believe. SS, high strength and Teflon lined. I have some 1" bore ones in a OT tube frame I built. Using them in rectagular tube control arms for a 4 link.
Would require fabbing up a housing for it to press into that could be welded to the rearend.

 

Sorry , don't see any advantage , visually , structurally or functionally for incorporating the suspension bar mount & the spring shackle mount.
Why such long shackles ?

 

You mean like this



With the Heim End attached with 2 simple brackets.
And the other end supports the springs.

This part is available off the shelf

 

How is the rod end going to attach to the axle housing? Seems like a weak link in the system going from two heavy brackets to a stud.

 

@Kerrynzl first thank you for your replies !! I posted a pic, as you can see in this pic, the rear is held in by a true triangulated 4 link bar system. So any and all pressure under load will be absorbed by the 4 link.

The lower part of the shackle will not change, the shackle will only get narrower at the top in order to put the heim joint in double shear with the shackle being bolted directly to the heim, then the heim screwed into a nut welded into that axle bracket facing front to rear not side ways.

I have thought about shear right behind the heim pivot into the threads BUT I also understand that a race car with a 4 link does exactly that at every launch, it puts pressure against the heims in both compression (as the axle tries to wrap and tries forcing lower heims into the 4 link tube) and expansion (as axle tries to wrap and pull upper heims out of tubes) but also side shear as the axle tries to wrap and ends up lifting the entire front end when enough torque is applied.

In my case spring does nothing to control the rear-end movement but just hold the car up. Much like a coil over, it has no control over the movement of the housing (as far as fore, aft or side movement) I've also noticed that some coil overs come with sleeves for using a 7/16" bolt in their upper mount. So I thought if it's OK to use a 7/16" bolt thru the top of their coil overs it should be fine for my shackles. Because it operation they are doing the same thing. Also shackle length is just thrown on there for now, just to keep the frame off of the rear housing.

I'll get a drawing putting everything in perspective and post it later...

Here is a pic of my triangulated 4 link set up...

 

@lostone
I think I understand so I edited my previous post [have a look again]
That part [or similar] is a replacement for the "shackle" that supports the vehicle???

Is this what you are wanting

here is another example


The spring eye must be "double shear" mounted or the whole spring will torsional twist

 

Rod ends should not be used in bending situations. Try to use them in tension and compression.

 

I think I see the reason you want to do this. As the axle is located entirely by the 4 bars (as GM did on many cars) you would like to free the springs from side loads so they can perform the same function as coils would in a conventional setup. In that case, I'd be inclined to replace the shackles with links that have heims at both ends so the springs can move freely through their arc. You would need to make a fitting that bolts into the spring and supports a heim rigidly. In other words this fitting can't rotate in the spring's shackle bore. I like the height adjustment built into your spring hangars. As mentioned by others, when in doubt, use bigger heims.

 

Yeah, this would be a perfect fit if you ask me.
Use it to entirely replace the shackle and bolt the Heim/Spherical bearing right into your current axle housing mount location....just split the mount on the housing into two tabs with the Heim/Sph bearing between them.

 

Yep!!!
Cut the old brackets off, and weld 2 of these type brackets [each side] so the Heim joint ball is bolted through "double shear"
And bolt the leaf spring at the other end.

 

Kerry has it.

 

A beefier heim, say 3/4", and instead of the 'nut', as pictured, something like a drilled and tapped 1 1/2" or more round bar as the mounting, gusseted for good measure, should work fine. Those other joints shown would be my choice though.

Chris

 

A couple of thoughts on how to mount the Heim vertically to put the loads in tension/compression.
1) Mount the nut the Heim screws into vertically to the axle.
2) When you bend the shackle straps in, weld the nut between them, in essence making your own version of what Kerry showed.

 

@Kerrynzl you have what I got in mind, I'd like to find a smaller heim end though to keep plenty of space between shackles and frame.

@Happydaze that is what I'm wanting to figure out is how big does the heim joint really need to be? At this point I'm figuring a static weight of 3000 pounds (car weight) and since no load of rear end positioning due to the fact the 4 link will be holding the rear end in place and taking all loads, how big is big enough? Without being over kill and to keep it small.

@X-cpe 1) I have looked at exactly that, putting the heim joint straight up and down but it looks like with the way everything is set up I could put the nut at a 45 degree angle and not have to re-engineer a bunch of stuff.
2) that was my first plan and may still go with it but I liked the idea of the shackle being 2 piece and being the shear of the heim joint.

A couple home drawings to make sure everyone sees my idea, and again THANK YOU ALL !for your replies and help. Sometimes it helps just to bounce thoughts around .. wife isn't much good for this kind of stuff!

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I'm no expert on much of anything, so I'm just asking, Won't the two weld nuts be hold 1/2 the car weight up?
Seems like not enough support.

 

Good question @Joe H , I often question things like this but then I think of all the abuse leaf springs go thru, rail road tracks, pot holes, curbs, not to mention Mopar hemi race cars back in the 60's then I think the back of the leaf spring is held in place by a 7/16" bolt.

I am amazed sometimes when working on cars and find such simple bolt sizes doing so much. That's part of my problem sometimes is trying to find the difference between more than adequate and what's over kill ! That's why I ask questions here lol !!

 

I would do what I had to to not be putting a bending load on the rod end threaded shank... Maybe look at re-fabbing the axle bracket to hold a welded in bearing housing, then pop a spherical bearing in it.

 

Here is an old thread that I think has some useful information:
https://www.jalopyjournal.com/forum/threads/quarter-elliptic-rear-suspension.143466/

@krylon32 posted on the thread and may have some ideas.

 

When it comes to vehicle design one always should consider dynamic/cyclical loading. The “G” forces or acceleration forces can be a magnitude or more than any static load depending on vehicle speed and terrain. In the case of this arrangement, the heim joint will be subjected to both dynamic forces and cyclical loading. No real way for you to accurately calculate that, so go with what others have done which have stood the test of time.

 

You could fabricate something like this. It uses 3/4" Uniball and 1/2" bolt. The tower is machined from 1" thick CR steel. Shown with a 1/4" thick formed gusset

 

Well said and very important points to consider.

 

@tomcat11 I like that very much !! That's definitely something i will be checking into !!

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It doesn't matter if the Shackle OR the Bracket is double shear, it is still the same width.
Heim Joints are strong under tension or compression but quite weak with lateral [or bending] loads.
This is why they fail at the front on ladder bars but don't with 4 link.

So you want the threaded shank of the heim to be directional to the loads
If you want to run this style of Shackle [below] then weld a vertical threaded tube and bracket to the axle so the heim joint is pulling directionally to the load


This ^^^ is just a variation of the bracket/shackle I posted previously [which is a Mustang S197 upper link]

A 5/8" heim would be plenty strong enough under tension ,I used this size on the Inner Lower arm on a MacStrut suspension in my Lotus Cortina Race car
And my brother uses 5/8" heims on the front tension struts in his Boss Mustang race car

 

Thank you @Kerrynzl I think I will do exactly that, especially after pricing the uniball.

I don't see a problem doing that and using heim joints. I agree, I have seen them break on ladder bars before, infact I've fixed a few that have done that. One was a 3700 lbs street car that ran 8.80's in the 1/4 mile, it was impressive as it was done on the street. It got enough bite to pull front tires off of the ground then it gave. Took me a couple days to get it back together...

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My old Corvette race car had 5/8" Heim joints for the Tie-Rods [needed for Bump Steer Correction]
I didn't even think about this at 176mph, fast approaching a hairpin bend.

It also put out 659 Ft/lbs of torque and had a 5-Link Heim Joint rear suspension.
with a 2.2:1 first Gear, a 3.08:1 rear and 26.5" wheels = 1011 lbs thrust against each forward link.

 

In the top picture , if you're expecting the threaded shank of the hemi to support ' side load" , they won't , they'll bend / break at the first opportunity .IMO

 

@2OLD2FAST

There shouldn't be any side load to speak of, the spring does nothing but support the weight. The triagulated 4 link does all the work.

The heim swivels back and forth on its pivot so that will follow the the leaf spring/shackle fore and aft, in fact the heim will do a full 360° rotation in its joint where as the movement of the shackle will probably be less than 20° thru its total movement.

The heim will also swivel 60° in side movement and I don't see the tires from side to side ever reaching 60° difference between them, if they do I have a serious problem.

If I were expecting the heim to locate the housing AND support to weight of the vehicle I could see concern then.

In fact I could use a piece of chain from the housing to the spring instead of a shackle and accomplish the exact same thing.

So I guess I'm not understanding where the side load your talking about is coming from on the vehicle.

Now understand I don't mean any of this in a negative way, I am truly interested in your thoughts !

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