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holy crap thats an pretty old FM kit on there. Might be an antique one day

Looks good.

OK - I am really going to try to get the rear suspension sorted and built. I have seen several set ups where there is a straight tube that holds the heim, and on the other side there is a bolt head. Does anyone know if that set up allows for adjustment without turning the heim, and where to get the bits?

Thanks!
Randy

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774

Like this:

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774

They aren't that difficult to make if you aren't able to find a set for sale. I made a set for my car using 3/4" grade 5 bolts. It was as easy as cutting off the threads and drilling and tapping the remaining part. The worst part was aligning the bolt in the drill press so the hole was true with the rest of the bolt.

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-Andrew
Build Log
Youtube

So you need a bolt that has an OD that fits exactly inside the ID of the control arm, and the heim side threads into the bolt center that you drilled and tapped? Does the bolt that you cut reach all the way to the end of the control arm "carrier" for the bolt? What does the lock nut on the heim lock down on?

Thanks! I am trying to wrap my head around the way it works, as it seems better than using the weldable bungs for the heim so I can adjust the heim without turning it (therefore not needing to remove it from the chassis mount).

Randy

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774

Pretty much, yes. The sizing of the bolt may differ depending on the rod-end size used. The 3/4" bolt drilled and tapped to a 1/2-20 thread happened to have slightly more axial strength in the drilled area than the rod-end it was attached to; I'll throw out the caution that if the rod-end's axial strength exceeds the axial strength of the drilled bolt and the rod-end is loaded to its limit, the bolt may fail at the end of the drilled hole and cause the suspension to come apart.

Also, keep in mind you will be inducing bending into the rod-end's shank so it is probably a good idea to at least step up to a stronger alloy rod-end. You'll probably also want to make the tube the bolt slides into thicker than the normal 0.063".


I made mine approximately 1/8" shorter than the tube at the end of the arm. Anywhere between 1/16 and 1/8" should be fine. You just don't want the jam nut on the rod-end to clamp on to your custom bolt since that won't prevent the entire assembly from sliding or rotating within the arm.


On mine, it clamps down on the tube at the end of the arm (the head of the bolt is at the other end). You'll want to use a washer that is at least 1/16" thick with the same OD as the arm's tube to prevent the nut from pulling into the tube when its tightened.

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-Andrew
Build Log
Youtube

Thanks! It seems that the weldable bung ends would be stronger and easier, except that to adjust the suspension, you have to remove the heim from the chassis mount (much bigger pain). Does that sound accurate?

I appreciate the help.

Randy

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774

Np Randy. You spotted a problem on my car long before I did.

That sounds about accurate. The only real downside is you only have adjustment accuracy to 1/2 of a turn of the rod-end. For a 1/2-20 rod-end, that works out to be around 0.025" increments.

I'd imagine that would be accurate enough but you might want to see what sort of camber change that would cause.

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-Andrew
Build Log
Youtube

Thanks Andrew! I think I am going to stick to the bungs and check the camber from there. If it makes too gross an adjustment, I could always modify the arm itself to accept shims similar to the Elise. I am really itching to go on the seven, but I've been too busy working on other folks' MINIs!

I am going to go back to your build log and check out what you've done. I know from memory I love your build!

Randy

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774

I've got a full heim setup on my build. I knew the limitations of the 1/2 turn increment but thought I'd work that issue out later as a lot of builds are like that. So you got me thinking. I layed it out in cad and found that, assuming an 8" separation of upper and lower BJ's or inner locating joints, 1/2 turn makes 0.18degree change in Camber. I can imagine .025 compression with a rubber bushing joint so it can't cause that much of a problem. I can live with .025" resolution.

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

Thanks for doing the math. If I were that precise in my driving, I would worry about that camber. I doubt you could even see that in tire temps.

I located the mounts tonight. I am going to be making the rear out of PVC first, then ordering the tubing.

I don't feel comfortable making accurate cuts for the suspension tubing on the chop saw - what have you guys done to make the cuts perfect?

Thanks,
Randy

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774

NIce to see you back after it Randy.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

It seems that there are generally two methods to making very exact cuts on metal tubing.

1. Cold Saw. (If you can afford a cold saw I will be wicked jealous)
2. Gravity Bandsaw. (Good ones will nail your cuts, bad ones will need a little grinder/sanding disk cleanup)

Having said that I know a girl who built a bike with tube miter templates a hack saw and hand files. How much time do you have?

Thanks! I am still very budget and time limited, but it is driving me crazy seeing the project stagnate! I plan on buying the bungs this week. Hopefully I can get the rear suspension done in a couple of weeks, then start on the front. Getting it to roll would be a big boost!

On the cuts, I have a friend that may have a cold saw. He does fabrication work for me when the work I need is beyond my tool set or capability. I will check on that after I get the tube sizes all set with PVC.

Randy

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774

I have bought the weldable bungs for the rear arms, and now I am just waiting for the chromoly to get here. I have the rear mounts in place on the chassis. Hopefully, once this step is out of the way, I can start making faster progress again...

Randy

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774