heim joints on wcm ultralite /xr7 and other 7s

[MHKflyer52]

Why not make a couple of spacers and a plate that would connect to the drag link and shock mount something like what I have shown in the attached jpeg. It would help reduce the load on the spacer and bolt at the hub face I do believe and still let you have adjust ability due to the bushing in the lower drag link mount.

 

 

Just an idea to solve the issue.

Hope this helps.

:driving:

[jimrankin]

Hi MHK,

I am building something like that but the flat metal brace needs to be horizontal, not vertical, as the lower control arm mainly only sees "side loads". I did a rough sketch just to see what, how much and of what thickness I need to purchase to complete it.

Being a bit old school (read computer retard) I do my drawings by hand so will do a better sketch just to post. The finished product is a while away as I have a couple of other projects in the works right now and no scheduled track days pressing me. Probably going to do the whole Teflon/shoulder bolt replacement now since I'll need a realignment anyway and have one side of the rear suspension all off already.

[jimrankin]

Excuse the bad drawing, done on a table top since I no longer have an actual drawing table, retired ;-). Didn't quite know how to show a fillet weld so the ,,,,,,,, is it.

Basically it's the two tubes joined by a flat steel plate with a horizontal brace at the widest, most stressed place to limit the chance it will bend there. Once I fit it up I'll add a "stop" of some kind to keep the flat plate at horizontal so it stays in line with the load.

I'm better at fabricating than at drawing (lets hope anyway) so I'll post a finished picture and some of the fab if I remember my camera.

[jimrankin]

see if this is understandable.

[powderbrake]

Th To gain the greatest benefit from the spacer, the portion of the upright in contact with the spacer should be faced square and the bolts torqued to max spec to maintain the spacer in contact during bending. This arrangement will essentially allow the spacer and bolt to act as a larger beam section.

 

I believe that machining the upright, and using a larger diameter spacer would be most effective.

 

jimrakin's design needs a cutout in the web as it passes over the boss of the upright. It currently shows a straight line, but I don't believe that will fit in place. When it is done, it only offers the additional bending strength of the flat steel plate at the cutout section. Better than nothing, but if used, I would make the plate as thick as possible, at least 1/4 or 3/8 thick.

 

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Another source for tie rods is http://www.colemanracing.com I replaced a couple of mine which had the rod ends "frozen" in place. Don't forget that neversieze when assembling rod ends.

Edited September 17, 2013 by powderbrake

[jimrankin]

The boss is only between 1/4" - 5/16" past the outer edge of the bolt hole, one of the reasons just using a tapered cone wasn't possible. With a 1/8" wall tube the "notch" will be only about 3/16" deep at that point. I was going to fab it "straight" and then die grind it to as close a fit as possible to maintain the max cross section. That was also why I decided to put the widest section of the brace, and the added vertical brace, at that point.

[powderbrake]

The boss is only between 1/4" - 5/16" past the outer edge of the bolt hole, one of the reasons just using a tapered cone wasn't possible. With a 1/8" wall tube the "notch" will be only about 3/16" deep at that point. I was going to fab it "straight" and then die grind it to as close a fit as possible to maintain the max cross section. That was also why I decided to put the widest section of the brace, and the added vertical brace, at that point.

 

That makes sense.

 

Maybe you could use heavier wall tubing, and not have to grind a notch.

[jimrankin]

I was using the 1/8" wall because that was about all the "flat" at the boss but going heavier will not really add much weight and will add more strength. I could probably shorten up the "floating" tube side a little bit also as the 5/8" bolt is captured by the two bosses so no stress problem there.

[powderbrake]

Since steel tubing is specified by OD and wall thickness, and you need clearance for a 5/8 (.625) bolt, here are some manufactured sizes.

 

OD Wall ID

 

3/4 .065 .620 ( a bit small)

 

13/16 .095 .623 ( a bit small)

 

7/8 .125 .625 ( might be too tight, but a drill through would clear it out)

7/8 .120 .635

 

15/16 .125 .688

15/16 .134 .670

15/16 .156 .626

 

1 .156 .688

1 .188 .625 ( same comment)

 

I would suggest going for the tight fit, and running a drill through if necessary, that way there is less slop in the system.

 

 

You may be limited in the OD that will fit because of the wall of the upright between the bosses.

Edited September 17, 2013 by powderbrake

[jimrankin]

I'm planning on making it down to one of two large metal supplier in the next day or so and will print this out. One keeps everything on computer and the other is cheaper but it's a "bring your own measuring devices" type place. I have a drill press and 5/8" drill bits so will go tight and ream it out.

[JohnK]

Late to the party, but...

Go to my page http://usa7s.com\vb\showthread.php?t=7421 ; then find the link just above the first pic ( and following "More pics at ..."). This'll take you to a page of text with links imbedded. At the end of the text look up a bit and you'll see a link starting with "t50..." and describing "single shear" - which is the problem here, and its solution in this situation. The link starting "t55_a..." shows a pic of the solution. Further up in the text is a top view at "t50..." Boot machinery.

[JohnK]

I'm planning on making it down to one of two large metal supplier in the next day or so and will print this out. One keeps everything on computer and the other is cheaper but it's a "bring your own measuring devices" type place. I have a drill press and 5/8" drill bits so will go tight and ream it out...

 

Recommend http://www.airpartsinc.com . they carry a wide range of Normalized (heat-treated) 4130 steel and their clients build aircraft. They give good service and are nice people.

[JohnK]

Hi Loren,

Where did you source the "U" shaped brackets the Heims bolt through? Instead of cutting off the old one and re-welding it to the new bolt I'd prefer just welding on a new one. See attached photo[ATTACH]5454[/ATTACH]

Also, do you have the name of the fabricator/supplier for the aluminum threaded control arm tubes?

 

Can't tell from the photo, but it looks like the welding was done on the shaft of the bolt, since I can't see the head of the bolt. All of mine were done on the periphery of the head - which gives a much broader footprint for the weld on the clevis. Additionally, I can't see that there's any penetration on the clevis. The welder should have melted metal on both parts and the failure would have torn metal from the clevis.

 

Speedway.

Weld-on shock mount with spacer. Part number 917-21000 $5.99.

Suspension links (control arms) part number 910-34158-(length in whole inches)-ALU. 6061-T6 aluminum $9-12 depending on length.

[jimrankin]

I actually read your whole post with great interest when you first put it on line. Almost thought you would have been better off starting with the outer body panels and a bare pile of material than a whole kit with the number of mods you ended up doing.

Extremely good fab work, especially the steering and the inboard rear brakes.

To answer a couple of questions;

The brackets were welded to the bolt heads and there were no indications that they were ever over stressed. In the photo I posted it may look like the weld was a fillet around the bolt shaft but it actually was what remained after I cut the bracket from the remains of the bolt with a carborundum saw. I didn't want to damage the bracket so left a bit of the bolt head on it then ground off the remaining weld slowly till the head popped off.

While your solution to the shear of the long bolt is impressive, deals with more than a single plane of stress and works well with your inboard brake and anti-roll bar add it's a bit more complicated than I'm planning on dealing with at the moment.

After I replaced the first failed bolt I did quite a bit of thinking about just what made it shear so easily. I jacked the car up till the rear tires were off the ground and slowly let it down (dropped it a couple of times hard too) and watched the suspension travel several times. It appeared that all of the stress on that particular bolt were at 0 &180 degrees to the control arms long axis as it swung through its limited arc. Fore, aft and rotational forces from braking and acceleration were all controlled by other links. Vertical loads by the shock and spring. Since I hadn't heard of the problem being a common failure I put it down to repetitive stress and just planned on replacing both bolts every year or two. Didn't get that long till the next failure so now going to do the "quickie" brace in my drawing as a hopefully permanent solution.

I will still have a limited shift to "off angle" of a few degrees as the suspension travels from compressed to extended but I will set it at 0/180 for normal ride height and think it will remain close enough that it takes up the stress the bolt alone can't handle when using the long spacer.

[JohnK]

Hi Jim,

Glad you found my original post interesting and thank you for the compliments. Original plan was to buy a "distressed" Superformance S1, make it 'right' and then experiment with the suspension. The Ultralite made too much sense re its basic features (engine I would have no reason to fiddle with, IRS, LSD, and it looked OK - however ....) Everything I've tackled has been out of necessity (several were no-brainers), but everything was done after careful study, consulting what's considered 'good practice', and my conclusions and intent corroborated by my Mechanical Engineer friend, - but I will accept that I used each fix as an opportunity to spend time learning about what constitutes a good design, and to develop new skills. (I mean, I'm a Biologist by training and my accomplishments have to do with experimental surgery and analysing nervous system function!)

 

A thought or two re your bolt breaking: With Loren's experience that he's never seen this - and he has many instances where the rear suspension worked under very high loads, and your observations that the suspension link in question and the rest of the linkages look as though they act as intended (and the link in question is loaded in compression and tension only, in its travel), there might be something else taking place. A while back there were a couple of posts re an inboard suspension link being pulled out of the chassis (broke the tube on either side of the clevis), and I thought about the shock/a-arm going solid at the limit of the suspension's travel as a culprit. Re the rear, I saw that as I aligned the suspension trying to get all 4 wheels to the corners of the car, it wasn't hard to move the upright inward enough that the driveshaft plunge was too much and the D/S would impede the movement of the suspension. At the time my immediate worry was about ruining the CV joints and/or diff bearings, but such would also load the suspension in ways that were likely self-destructive. Also, as I got Koni to make me a set of shocks and had some heavy-duty software to inform my spring and Silasto choices, I made sure that the shock handled all at-limit suspension travel, avoiding any 'going solid' conditions. Hope this helps inform your thinking about the failure.

[rnr]

A previous owner put very large shocks on my car and the left rear spring did originally touch the drive shaft at high load right handers. We were running the track in a new configuration and I attributed the resulting high speed jerk to a bad bump and only realised the problem when I got home. The point of this being that you will see wear marks on the driveshaft if there is interference and from experience I can say that minor rubbing did not cause the specific failure Jim had.

[Mondo]

I was the one who's in-board shock set-up tore a mount when hitting a raised manhole cover (don't know how I didn't see it). The main problem was the shock springs were set way too low and like John said the shock bottomed,became solid, and the mount was the weak link in the system and tore from the frame.

 

I went back to the standard set up because the geometry of the inboard set up was not optimal as some things were in the way. It ended up created a twisting of one of the suspension parts. Not really surprising when your one of the "alpha" testers. Would of been cool though.

[m wirth]

I figured that even if it has only happened to one of our flock I would be next, so I layed under there for a while and came up with this solution for me. It gives support where it is needed and was quite simple to make. Hope this wil help someone else.

[WestTexasS2K]

Another good solution. The metal looks a little thin? Maybe 3/16 would be a bit stronger.

[rss]

that's nice, mike. simple and easy to fabricate. thanks for posting.

i haven't seen suspension limiting straps on an ultralite before. do you go airborne a lot?