heim joints on wcm ultralite /xr7 and other 7s

[jimrankin]

I finished fabrication and welding my braces but having second thoughts now that I see what you have done. will be lighter and really about as strong by upping the metal thickness a bit. Love this forum for the inventive and generous people on it.

[m wirth]

I had thought about a heavier guage metal, this is 1/8, but wanted to keep the"add lightness" moto, and all of the stress is comming laterally against a 2 1/2 cross section. I'm glad this may have helped some, nothing like brain storming and paradigms to get a problem solved.

[jlumba81]

Could just add a rib or two to stiffen it.

[jimrankin]

I liked the look of M.Wirths solution, sound idea so kind of left the original parts I had made shelved while I kept the wife happy for a couple of weeks cruising. [As soon as I get rid of the 15-20 lbs I gained I'll be able to actually bend over to work on the car ;-)].

Meanwhile I picked up some 2" X 3/16" flat stock and a couple more 5/8" nut/bolt/washers to get moving on the MW inspired part.

Sad to say that once I made the long plate, the oversized 2 5/8" lower spacer, a short "mid spacer" ( I was running the plate "outside" the upper heim joint with the short spacer at the mid bolt so it ran straight down to the inside of the lower heim) and the mid bolt it all combined weighed several ounce more than the rather crude parts I already had. They flat plates do look nicer, however I'm not sure that they are any stronger.

What I ended up with isn't pretty but it weighs in at 1 pound 1 oz. and should add a lot of strength. I will fix the angle of the "flat" brace at 0/180 degrees to the center of the suspension deflection. That deflection is relatively minor so it shouldn't be a problem.

One advantage to the MW part is that it is immune to suspension travel moving the maximum support off line.

I'll probably dig out the die grinder, clean these up a bit and paint them but here is the rough start. I'll probably do a better blueprint with the changes from the original so someone with some actual metal working tools and experience can turn out a lighter and better looking set.

[MHKflyer52]

Hi Jim,

 

Question. What will keep the flat plate from rotating to the horizontal when installed.

If you send me the dimensions of the tubes and the plates I will model them for you and run them through SimulationXpress in SolidWorks for you so you can see where the stress's will be on the part. (see attached photo [displacment under load of 1000lbf at the mengenta arrows material AISI 4340 Steel, normalized 0.125" THK])

If you want to lighten the part assy you could always drill out some of the material in the flat plate.

 

:driving:

Edited October 30, 2013 by MHKflyer52

[jimrankin]

I'm going to drill and tap a 1/4" hole in the flat plate on the "captured by the casting" side. I'll determine the exact spot when I do my fit up before paint and final assembly but it should come close to resting on the casting edges and keep the plate in the line I want. There is also the fact that the whole assembly is going to be torqued pretty tight with the 5/8" bolt so probably wouldn't move anyway.

Max stress is right at the fulcrum point (where the bolt leaves the casting, point of both previous breaks). I actually didn't need to make the "notch" as deep as it is as the casting is fairly narrow where the bolt passes through. Will address that when I do a final drawing. Drilling holes is a good idea, just need to keep the maximum amount of metal where the stress is greatest.

I used 3/16" wall tube at the "extension" side but with the brace probably could have stayed with 1/8". 1/16" tube is all that would fit on the "captured' side but that seems to be strong enough.

Fighting a cold but going to get out to the garage as soon as the sun warms things up a bit and see if I can motivate myself into getting the parts done today.

I'll get some dimensions as soon as I finish so you can let me know if you think it will work. Got to be better than the original un-braced bolt set up.

[MHKflyer52]

OK. It will work.

:driving:

[jimrankin]

Finished up all the fab and painted the parts yesterday so it was my plan to put it all together this weekend.

I had noticed that I had several different types of shock/suspension mounting "U" brackets on the car plus the new ones I just welded up so knew I was going to need several different lengths on the shoulder bolts. I completely disassembled the cars front suspension this AM, back was already apart, so I could mike the different parts. I have three different thickness's on the section of the existing brackets the bolt clamps through and one bracket with an add to the range because my headlight mounts to it also.

Not a problem except... I had been planning on picking up all of the shoulder bolts/nuts/washers at my local Fastenal store. Forget that, looks like time for an on line order as they didn't have most of it in stock and what they did have only sold in bags of 50. They didn't even have an anti-seize compound, had to go to my local hardware for that so at least I can install all the new heims into the existing suspension tubes etc and just wait on a UPS delivery next week for final assembly.

I don't have any pre-paid track days scheduled so no big deal, just wanted to get it done and go for a ride!!

[jimrankin]

This should (I sure hope) prevent any future problems.

I purchased longer grade #8 bolts so that the new heims will sit on the unthreaded part of the bolts instead of the threaded portion. Actually had to add one round of threads to get the bolt to pinch up tight. Welded on the new brackets so hope that end is nice and tight when it goes together with the new shoulder bolts.

The new brace installs as shown here. I set the suspension at mid travel and then lined up the web of the brace to the angle of the rear lower link to keep it in the line of maximum force. Drilled and tapped a hole through the web that aligned with the two casting edges so the brace will stay aligned. It shouldn't move even without the pin as the whole thing is going to be torqued pretty tight.

The "notch" is actually deeper than required, I measured from the thicker tube instead of the thinner one. Forgot to "measure twice, cut once" ;-).

[JohnK]

Looks great and it completes the rear part of the upright very nicely. Well done! But on top of that, think about: when anyone looks at the bits that make up the workings of current cars, especially sports cars, it's clear that you'd need not only a $5K CAD package to draw any of them but a Finite Element Analysis package to tell you where to make it thick or thin, not to mention an engineer or two to give you the loads that are going to be fed into the part, and of course an NC 6-axis mill to turn it out ... all of which is way beyond the means of anyone whose name isn't Boeing or General Electric - or even McLaren or Mosler. What you've done is the kind of stuff that's in the realm of possibility for an enthusiast with his head on straight and a desire to have his car work like he wants it to. And what that's doing is recreating the good old days when you could make something in your back yard with your own two hands and some affordable tools that fixes something properly. And I happen to also think that that's great fun!

[jimrankin]

Your right, working on these cars is part of the fun. If they weren't so damm much fun to drive I'd say it was an equal part.

My tooling/garage is more set up for woodworking so my metal working items are pretty limited. There are some members on this forum who do have access to some (seams to me at least) sophisticated computer programs and a couple with some really nice metal working tools.

I really regret not having had a chance to learn how to run some of those tools. When I had mentioned this before a friend of mine told me that a lot of good but obsolete(anything that isn't controlled by a computer program) equipment is available cheap. Wish I had looked into it sooner, this dog is a bit old to learn very many new tricks ;-).

The 7 is a perfect car for people who want to be able to do their own work with available tools and equipment, and for us guys who are still "stuck in the 60's" when "special tool" meant a micrometer or a torque wrench and "electronics" meant a timing light and a dwell meter. LOL.

Love these cars, all makes, and this forum.

[MHKflyer52]

John K is correct and I agree it is fun to work on any hand crafted car and not have to take it to a repair facility to keep it running like the new cars of today require.

Nice job of fibbing the stiffening brackets for you 7.

 

PS: SolidWorks Professional about 7K

SolidWorks Simulation about 3K

College education to put the above into practice priceless

[jimrankin]

I'd be pulling it out! LOL.

I seemed to have forgotten my own and others statements about these cars all being slightly different. I duplicate the heim joint order posted on this blog earlier after counting what I needed and it seemingly being correct. Installed them all except the following;

Both my upper outer heims are 5/8" instead of the more common 1/2" used on all the other front heims.

My steering is metric, not SAE, so the two 1/2" X 1/2" heims for that don't work either. The existing ball type end has a longer shaft so will need a longer tube to fit the replacement heim.

I'm still waiting for all my shoulder bolts to arrive (slow vendor, coming next Monday) so will go ahead and order the additional 5/8" heim/shoulder bolts sets and also the metric heims, two longer suspension tubes and appropriate shoulder bolts for them.

Just an aside. About half of my existing heims did show some wear (only a couple were noticeably loose, most still within useable range)and I had replaced one that was really worn already. I think a lot, probably most, of the rattles were from the poor fit of the heims on the threaded bolts. It would probably be wise for anyone on a budget to replace all of the threaded bolts with shoulder bolts before spending the money on upgrading the heims. That would be a really easy, and cheap, starting point. Squeaks are still going to be there but I found that regular application of dry Teflon or MollyBlue chain oil helped a lot. Doing the shoulder bolt fix might also help the wear rate on the existing heims as some of the 'slam" might get reduced.

Have to work on my boat and start a couple of wood Christmas present projects so the car is going to get covered and play second fiddle for a couple of weeks but will get back to it when I have everything to complete it in hand. At least it ain't summer. ;-).

in hand

[Mondo]

threaded bolts vs shouldered bolts? pics?

[rss]

Bruce I sent you a response on the PM the other day. Maybe you didn't get it. I like to use these bolts (http://www.fastenal.com/web/products/details/26352?searchMode=productSearch&rfqXref=&rfqKeyword=&rfqId=&rfqLineId= on the joints. The original bolts have a slight bit of movement because the threaded section of the bolt is slightly smaller than 1/2 and this will allow some wiggle in the joints. These bolts have a machined 1/2 shoulder and makes the joints tight. You will need to use a flat washer with a nylock nut to tighten the joint down. I do not recommend using any type of fastner that will sandwich the bracket to pinch the joint. This can cause some binding and adds no strength to the connection. The brackets are made to have the head thru the bolt as originally done. If you just add the teflon rod ends with the the shoulder bolt it makes a very tight suspension pick up.

 

Be sure to check each bracket some of the brackets have a welded in spacer which can vary in thickness depending on the brand. So when you get the shoulder bolt the length can vary 1/4 inch between bracket brands.

 

 

mondo,

westtexas made this post early in this thread. i used the fastenal shoulder bolts and they worked great. getting the right length is critical. the length of the machined shoulder needs to equal the thickness of the spherical bearing in the rod end plus the thickness of the spacer in the bracket.

when i replaced all the heims on my car, most had a little play, a few were completely shot. i'll bet half of the slop was from the fully threaded bolts rather than the actual heim joints.

[Mondo]

This is one of the longer threads here... Got it, thanks.

[jimrankin]

Finally got around to cleaning up from doing some wood butchering in the garage and got the car put back together with all new Teflon heims and shoulder bolts. Turns out my car has a metric steering rack so didn't do the steering rod ends as I didn't have any metric heims or suspension tubes available, do that later when I find a source.

Couple of things to note that were not brought up before:

I used a set of standard calipers to measure the heim joint location at each end of the suspension rod instead of trammel points or a large caliper. See the photo, worked well and was easy to duplicate each replacement heims location.

My carriers had originally used an upper tapered shaft ball joint when in the donor car. That is why my upper heims were 5/8" rather than what seems to be the standard 1/2". Since it was metric the threaded bolts I replaced were tight, the shoulder bolts required my using a 5/8" ream to get them in.

I had to replace both the upper (shorted) and the lower (longer) 5'8" bolts as the heims were landing on the threaded portion of both. I welded on new brackets and extended the threads to just where the heim finalized so it sits on an unthreaded area. Should have ordered aircraft bolts for this as there are still a few thousands clearance with stock grade 8 bolt shafts. See photo of the shorter "tops".

The brace has a large area to mate with the rear carrier and a wing to transfer the stress to the captured portion of the bolt as it passes through the carrier. I aligned the wing with the center line of the axis of stress. The old tube (black) the brace replaced is in the last photo

[GunshipDriver]

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.

 

I really like this solution. I was giving some thought to doing similar with a slightly larger piece of 6061 Aluminum. I was thinking a large rectangular piece of about 3/8" thickness... just need to ensure the hole get drilled at the correct angle for the bottom one.

 

That said, the more I stare at the imaginary upper and lower a-arms and they way the vehicle is set up... I understand why the rear part of the lower a-arm needs to be mounted lower on the hub vice the open hole immediately below the rear part of the upper a-arm as you want them to be roughly parallel to allow the suspension to cycle freely up and down as triangulating it vertically would be bad.

 

On that note... I don't see what would be so bad with adjusting how it triangulates in the "horizontal" plane. Why not just remove the long spacer, use a shorter 5/8" bolt, and attach the rear part of the lower a-arm there. Sure it might slighly affect how the toe or other alignment facets may change during the cycling of the suspension, however, I don't see it being quite so negative that the benefits do not outweigh the cost.

 

Could someone please set me straight or enlighten me as required.

[GunshipDriver]

Looking at the distance between mounting points. The back part of the rear upper and lower control arms are 7" apart vertically. This is about the same the way they are currently mounted to the hub (hence the long extension on the 5/8" through bolt). To connect the back lower control arm closer to the hub (removing the aluminum spacer) would create a vertical separation distance of about 6.5"... That said, the rear suspension would then lose some of its negative camber while the tire/wheel cycles up through the full range of travel. Also, I haven't tried doing this yet but I am not sure if the control arm can span/reach that distance in its stock configuration and will limit its range of adjustments....