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Old 09-20-2016, 02:56 PM   #21
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This is totally rad. Thanks for posting your work!
A few questions from a suspension noob...:
1. How accurate does the angle of the fixed bolt need to be in relation to the clevis pin? I guess it would all come down to how much adjustment you can make?
2. I have no idea what the range of motion on a heim is. If you were to make the ball joint holder piece a little wider would it enable you to use the 1/2" units? (No idea what the constraints are on that size)
2b. After you informed us that this is common practice, I noticed that other versions of these have bends here and there to account for articulation. Do you think a bend would hinder the strength enough to where using the 3/8" heim is a better option?
3. Any plans to attack the rear upper arms?

Again, awesome work!
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Old 09-20-2016, 03:20 PM   #22
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1. Not very, the adjustable links allow you make up for any slight variations. Honestly you'll find more variance in the upper control arm mounts on the sub frame which is one of the reasons I built these. I've measured 4 subframes biw and the variance can be near a 1/4" in the spread from side to side.

2. Heims generally have a little over 30 deg articulation, making the ball joint knuckle wider would help this, but not enough to eliminate the need for high misalignment adapters. If you're concerned with strength then I would look at using 5/8" heims and a half inch bolt with the marginal spacers.

2b. Bent arms wouldn't allow you to make adjustment, not enough room to the shock to swing a curved tube.

3. Rears are next on my to-do list

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Old 09-21-2016, 03:37 PM   #23
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Quote:
Originally Posted by Bronson M View Post
Exactly, the threaded portion of the heim won't take it. This is the failure mode.

Edit to add link: https://www.formulastudent.de/academ...-of-fs-design/
I would think it would depend on the diameter of the shank. There's gotta be a shank diameter for any load where it doesn't matter that it's threaded.

The "Rod Ends in Bending" pic shows the rod end being used in a geometry where it's more likely to exceed the heim's range of motion than it is to bend the shank (although exceeding the range of motion would put an additional load on the shank).
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Old 09-22-2016, 10:03 PM   #24
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Quote:
Originally Posted by huesmann View Post
I would think it would depend on the diameter of the shank. There's gotta be a shank diameter for any load where it doesn't matter that it's threaded.

The "Rod Ends in Bending" pic shows the rod end being used in a geometry where it's more likely to exceed the heim's range of motion than it is to bend the shank (although exceeding the range of motion would put an additional load on the shank).
I agree there is a diameter of threaded rod that will be ok, I can tell you it's much larger than 3/4". Trying to make reducing bushings for a 1 1/4" or larger heim just gets to be silly though.

While exceeding the range of motion is a sure way to snap a heim I can assure you the author of that article is talking about a bending moment on the heim, it's bad, it breaks stuff. Formula SAE is a competition amoung engineering schools and the gent on that link is one of the judges.....he says don't do it........I didn't listen and we snapped a 3/4" heim on a 400 lb. vehicle trying to use it on the outer end of the lower a-arm and snapped several 5/8" heims on the inner side. Don't do what I did.

Update: Been driving this to work for the past 2 weeks and I've logged ~1000 miles so far. This includes some knarly road work area's with 2" verticle cuts in the pavement where they were getting ready to lay new asphault to the old. No sign of failure.

Last edited by Bronson M; 09-22-2016 at 10:42 PM.
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Old 09-23-2016, 11:30 AM   #25
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Shrug. My old Mustang's rear trailing LCAs have threaded heims on one end (poly on the other). Although I don't personally have any vertical loads on the arm, they're designed to have one for the rear spring (I happen to have coilovers which relocate the spring load). They're 1.5"x0.120" tubing with 3/4" rod ends.
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Old 10-27-2016, 07:25 PM   #26
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Did you ever weigh these?
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Old 10-27-2016, 07:38 PM   #27
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I did not, upper arms don't weight much so weight savings was never the intent of this project. I would imagine any weight difference would be in ounces not pounds.
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