driver's side lower control arm bracket

Finished lining things up, rechecked the axle position, and welded on the inboard side of the lower control arm bracket last night:

Driver side Lower control arm layout

I started on the lower control arm bracket for the drivers side today.  It took a while but when everything was right, the DS was in EXACTLY the same spot as the PS no matter what you measure.  People make fun of american car manufacturing quality, but it is really good on newer cars.  I am not used to things lining up this perfectly on older cars.

Notice the bolt head to steel edge distance on the two brackets below.  It just worked out that way since I started with the same size steel angle, the frame rail height was exactly the same, and the control arm angles are exactly the same, and the axle is perfectly level, and its mounts are exactly the same height...

upper control arm and mount

Had a huge day on Sunday:
First tacked on the control arm tube.  I made this fixture to make sure the tube got put on straight.

 Tacked the bracket into place:

Ready to be welded up.

Seem to get the best welds when it matters most.  Glad for the good luck.

To shim the clevis with some clearance, I made this .025 thick washer on the lathe:

 Welded up the other side of the clevis:

Like above, here is the first quarter of weld on the control arm:

All in place and tacked together:

Control arm done:

Everything back in the car.  Passenger side is complete now and ready for paint.

upper control arm clevis

The upper control arms will utilize a clevis on the differential end.  I will use 4130 1.25 X.120 tube which will terminate with tube adapter and rod end at the car side.

I started with the clevis that I made from 2.5 x .125 square tube.

Score and cut

I used the score and bend method I described a while back here:

Clamp it shut and tack it:

The inside width of the clevis was a little too small so I cut the sides free from the top and spread them open with a little rig I made from some trash:

Now spread wide

I then bolted it onto the differential (with a washer this time!) to straighten the ears out and set the width:

I tacked the ears in place then removed and welded up solid.  My friend Bill gave me a couple tig welding tips the other day which helped me.  These welds are looking better:

hammer massage

Went to put the bracket in and the control arm wouldn't go in.  Normally when I make a clevis, I stick a washer in the stackup to leave a little space.  I forgot to do that this time, and when all that welding pulled things in it was a little too narrow.  The bracket is really stiff, and took an enormous force to spread even a little.  I was planning for hammers and press, or cut pry and reweld.  I didn't really like any of these options.

I figured I would try and use the tig torch to bend the bracket.  I ran an autogenous weld across the bracket.  Below you can see where I ran the torch across next to my previous weld.  Although running a large gap would have had a higher heat input, I decided to keep the gap small so that the weld wouldn't look gnarly.

This opened the clevis .020 inch and allowed the arm to install with a few gentle hammer whacks.

Installed!

 

PS Lower control arm bracket

First of many brackets to come for the rear suspension:


Bolt on the bracket piece to the control arm and jack into place:

 Zap.  This was the root pass.

Welded the inside too: 

After the second pass:

Bracket back in, transfer punch the hole onto the other side:

Drill hole through and bevel.  Bolt in place:

Tack in place then, remove bracket assembly again and weld up fully.

I closed up the back.  Even though this is a two force member, in roll the bushings will get torqued so I wanted to make sure the bushing moved, not the steel.  Also, thought it might help avoid a possible resonance issue.

roll bind

Roll bind happens when we don't have enough degrees of freedom for the solid rear axle to roll.  In fact the factory mustang suspension would roll bind.  Each mustang pivot is a bolt through a bushing which does not allow twisting or lateral movement on the control arms.

Ford got around roll bind two ways that I can see:
1) Very large bushings which have relatively low stiffness to resist pivoting on any axis allowing for lateral flexing
2) Open section control arms which have low twisting stiffness.  In fact a friend of mine told me the other day that a while back people began replacing the "flimsy" control arms on mustangs with tubular ones, which resulted in ripping the mounts out of the body.

I have to make the upper control arms for my car and will make them tubular.  I suspected that using rod ends instead of bushings would prevent the roll bind issues.  My friend suspected that a triangulated 4 bar will still roll bind.  I made up a little model out of a broken kid toy and some welding wire:

I found that if I tried to translate the "axle" laterally on of the wires would slacken, indicating that the control arms would resist this motion.  They allowed bump, and they seem to allow roll as long as I rotate the axle on its long axis a little to keep the wires tight.  Within the limits that I can tell with this crude test, I think I will be alright using rod ends and closed tubes.