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May 20, 2016

Mounting The Tub 

After a long winter of waiting, I was finally ready to re-mount the refurbed tub onto the refurbed frame a few weeks ago.  I was really looking forward to this event, partly because it would generate an additional parking space in the garage and give me more working room.

In preparation for the mating ceremony, I did a few last minute things.  I filled the gearbox and differential with  GL4 gear oil, then did a little precautionary trimming of the reinforcing brackets on the differential bridge.  I wasn't sure it was necessary, but didn't want to take the chance.

Then I did a final corrosion preventative treatment to the interior of the frame.  I had used a popular "Internal Frame Coating" as I finished the frame repair, but as far as I can tell, it is just an ordinarty zinc phosphate primer.  It's one of those products that is probably sold under a number of very application-specific names, but I think the only thing about it that makes it uniquely suited for the inside of frames is the extended spray nozzle that comes with it.  Beyond that, it is just a paint, and I don't have high confidence in its effectiveness on metal surfaces that can't be properly prepared for paint.  In my opinion, there are better treatments for confined interior spaces.

I use a product that appears to be a heavy wax thinned with a solvent and delivered from a spray can.  I've bought it under several names, but it all seems to be the same stuff.  It smells, looks, and feels the same as what Ziebart uses.  It clings to surfaces, then dries to a soft gummy film that never hardens.  I used the same nozzle that came with the Internal Frame Coating.

One thing that complicates the application of anything inside the frame members is the numerous internal stiffening baffles.  I used a feeler to find the baffles and mark them to make sure I didn't miss any areas.  In a couple of places, I drilled holes for access.

With the inside of the frame finished up, I turned to the outside.  I bought a body mounting kit form one of the big three suppliers.  I don't remember which supplier it was, but it was a huge disappointment.  I didn't end up using much of it.  One part that was OK was the rubber strips that get glued to the frame rails.

The main body mounts on either side of the cabin floor are a combination of metal plates and rubber pads.  My car was missing one of the trapezoidal metal plates, and I wanted to at least start with the same mounts at all four places, so I had to make a trapezoidal plate, using the existing one as a pattern.  I derusted and powder coated all the plates.

There was supposed to be four trapezoidal and four square rubber pads in the mounting kit, but it was short one of the square ones.  I was consdidering using one of the originals when I noticed that while the original pads have a reinforcing fabric embedded in them, the new ones were just rubber, with no reinforcement.  The fabric layer serves to prevent the rubber from distorting and extruding under pressure.  In the end, I decided to chuck all the bought pads and just make them from a sheet of 1/8 inch reinforced rubber sheet.  I was also irritated by the sloppy shape of the purchased trapezoidal pads.

I built up mounts by sandwiching the metal plates between rubber pads.

In sorting through the other parts in the mounting kit, I discovered that it didn't include any of the thin rubber washers needed for some of the mounting points, and that the thick ones in the kit also didn't have any reinforcement.  So I had to go back to my rubber sheet to make the thick washers, and ordered the thin ones (probably from a different supplier since they came made of reinforced material).

So then, it was show time!  Hooked up the skyhook, lifted the tub off the rotisserie and pulled it out of the way, and gently nudged the hanging tub over to the waiting frame.

Since I had braced the door openings of the tub before I removed it from the frame, and had been pretty careful to keep the front and rear of the tub located and supported on the rotisserie while I was doing all the repair on it, I hoped that I'd have minimal trouble with re-mounting the tub.  At most of the mounting points, the nominal compliment of spacers and rubber washers seemed to be about right to fill the gap between the frame and tub.  One confusion was with the holes that  accept the seat belt stalks near the central tunnel.  All the catalogs show rubber mounts there, but my car had thick steel spacers instead.  This was apparently a change made some time before '74 that the suppliers don't acknowledge in their parts listings.  (The larger spacer in the pic is an unrelated part that I thought at the time was a mounting shim.)

The next tense moment was removing the door opening braces.  I feared that all the welding on the tub had built up huge forces only restrained by those braces, and removing them would release the pent up energy by springing the tub into a twisted shell.  I measured each door opening so I'd know how much things moved.  Thankfully, removing the braces was a non-event.  Movement was minimal--well under an eighth of an inch on one side, and virtually zero on the other..

The next milestone was to temporarily mount the doors and fenders to see if the door gaps were out of whack.  It took some fiddling, but I was able to satisfy myself that I'll be able to get the door gaps to be OK.

In looking at the hardware provided in the "kit" to fasten the body, I discovered one more outrage.  The washer on the left in the pic below is an original item used under many of the tub fixing bolts.   It is thick to ensure it doesn't distort while spreading clamping force evenly to the sheet metal of the tub.  The washer on the right is what the "kit" supplied for the job.  With some mild cursing, I tossed the kit washers in my loose hardware bucket.  I was able to save about half of the original washers by derusting and replating, but had to buy the rest from an industrial supplier.

So, in spite of the worthless mounting kit, my tub is now provisionally mounted on the frame, I have some newfound space in the garage, and I'm really looking forward to a summer of bolting things onto the car.

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