Page Thirty – A Proper Place for Bums

 

We floorboarded back on Page Nineteen, but we ain’t finished.  With solid new floorboards, one needs a place for one’s bum.  (Arse Mounts sounded a bit randy, Oh, Behave!)

I kept the seat mounts, or at least, the pieces of them, during the excision.  So, the first thing was to “fix” at least one seat mount so that I could get the correct measurements, especially the spacing of the bolt holes.  To do this, I bolted each end of the manky old mount to the seat rails, which I bead blasted and painted.  Looking mint, ain’t they?  (Look up↑)  I cut a quick piece of sheet metal and spot welded it to the old stuff, and the jobs a good’un!

Manky but "fixed" original seat mount

Fabricating: I divided the fabrication job into two parts – forward and aft of the support that bisects the floorboard, essentially the foot area and the area behind the seats.  Aft Profile: With my large contour gauge, I mapped the contours of the aft area of the floorboard, transferred the contour to a piece of file folder and cut it out.  I fine-tuned the file folder profile to the angle of the aft of the support, half done.  Forward Profile: To get the forward profile, I held the aft portion in place with welding magnets and used the small contour gauge to map the contour of the forward of the support.  I transferred the profile to a piece of file folder, cut it out and taped it to the aft section.  After fine tuning the combined pieces to the contour of the floorboard, I used the chunk of manky old seat mount to get the angle of the interface between the adjuster and the mount as well as the total height of the mount.  A little guess work in that last bit.  (My guess was a bit off as I would find out later.)

Paper template with forward and aft profiles

Repeat the contour-file-folder-template routine for the other side – there’s a “tunnel side” (towards the drive shaft tunnel) and a “door side” (towards the door) of each seat mount, and because the floorboard contour changes from side to side, each side of each seat mount has a slightly different contour.  (Just for clarity, there are four seat mounts, two for each seat.)  If I don’t get each side’s contour correct, the seat mounts won’t be level to each other.  Not to mention the driver’s side being level with the passenger’s side.

I transferred the paper template to sheet metal and gave the bandsaw a workout.  (It destroyed one blade, dulled it to a fingernail.  It’s a lot of metal chewing!)  To fine tune the contours of each side, I clamped each in the bench vise, and assaulted it with the angle grinder.  The process includes many trips back to the floorboards to perfect the match.  That’s quick to write, but it takes hours.

Remember me worrying about getting the seat mount bolt holes in the correct places?  It matters when I make the center strip of the seat mount.  The original seat mounts used captured nuts to fasten the seats to the floor.  I needed to recreate them.  So, I cut a strip of file folder long enough to span from hole to hole and poked holes through to the original holes with a sharp punch.  The seats are held with ¼” bolts, but I cut slightly bigger holes so that I would have some wiggle room when I welded the nuts to the strip.

Original seat mount bolted to the seat adjuster to locate the holes

I cut the center strip on the bandsaw, marked the centerline of the strip, and used the file folder template to locate the hole positions.  Again, I drilled the holes larger than ¼” for the wiggle room I mentioned.  A quick comparison of the holes to the seat adjuster showed that I measure correctly.  I’m always surprised when I measure things correctly.

I centered up the nuts using an old bolt and two nuts (one to hold it flat against the center strip and one to be welded to the bottom of the strip) and set to MIGging the nuts in place.

Welding the Mounts:  I now have three pieces of the seat mount: the door side profile, the tunnel side profile, and the center strip (with nifty captured nuts), all of which must now be welded together. 

All the pieces ready for MIGging

Mid-MIGging - you'll note the nifty captured nuts

One down - this is the first one with thin metal. 
The burns show where the strengtheners are

I laid the parts flat on the welding table and butted them up to a large welding magnet.  With the front sections of each piece flat against the magnet, I marked the line where I needed to bend the center strip to match the bend at the aft end of the mount.  I clamped the center strip in the vise where I had marked the bend line and hammered in a bend.  Checked it to match the angle of the door and tunnel strips and adjusted as needed.

Clamping the center strip to the welding table, I matched up a side piece to the strip, checked and scrooted many times and MIGged on.  I MIGged in the second side and had a tunnel side seat mount for the passenger side.  Yea!  One down, three to go.

Passenger side mounts ready and bolted to the adjuster.  You can see the strengtheners in the upper mount (in the pic)

Repeat all of it – the contour mapping, the templated making and fine tuning, the bandsawing and grinding, the welding and I had two seat mounts for the passenger side.

Gluing Them to the Floor:  My main concern was keeping the seat mounts square with the seat adjuster.  If the mounts are the least bit crooked or uneven, the adjuster will bind, and the seat will be difficult or impossible to adjust.  My answer was to bolt the seat mounts to the adjuster and fit them to the floor as a unit.  With it bolted together, I took pains to locate the assembly to the floor.  I check the distance from the tunnel, and from the door sills as well as placing a speed square against the center beam to be sure it was all square.  Lots-o-scrooting!  Once I was satisfied, I ran a marker along each side of the mounts, marking the exact spot to weld each seat mount to the floor.

Passenger side welded to the floor

I even pulled a seat out of the shed and bolted it to the adjuster to be sure I had the spacing correct for the completed seats whenever that happens.

Next, and here’s where I screwed up, I removed the seat mounts from the adjuster and MIGged in each seat mount.  I should have done was spot welded the mounts down with the adjuster in place to be sure nothing moved during the welding.  Which is what I did on the driver’s side.

I added pieces to close off the front and rear of the seat mounts, nice and tidy.  I finished welding, ground down the welds and cleaned it all up with seam sealer.  A quick spray of primer, and DONE, methought.

I (tried) to bolt the adjuster to the newly affixed (passenger side) seat mounts but the holes were off by approximately a 1/16” as I feared.  I enlarged the holes on the adjuster, and it fixed the problem, but the passenger side will be slightly stiffer to adjust than the driver’s side.

Rinse and Repeat:  Now do it all over again for the driver’s side but try to do it better.  Four seat mounts!  Lots of sawing, grinding and welding!

Driver's door side mount test placement

Seat mounts welded in and finished with both adjuster restored and in place

Mistakes:  When I restore my next Sunbeam, I’ll crack on at fabricating seat mounts, but until then…

Mistake 1: Leave the seat adjuster bolted to the mounts to make the initial spot welds to the floorboards.  I did that on the driver’s side. 

Mistake 2:  Use 16-gauge sheet metal for all pieces.  I made one with 22-gauge – it’s the one with little spacers welded inside the mount to strengthen it.  Only one of the four uses the thinner metal, but you can't tell when everything is finished.

Mistake 3: Measure the height of the seat mounts more carefully.  You will notice that the original seat mount is about a half inch shorter than mine.  I noticed this after I had welded in the passenger side mounts, and with that, the die was cast.  I had to keep the same height on the driver’s side, or the seats would look dodgy when sitting side-by-side in the finished interior.  Fortunately, there is a lower hole where the seats pivot on the seat adjusters, so I should be able to compensate by using the lower hole.

Lower seat mounting holes will help compensate
for the seat mounts being too high

I’m sure there are other mistakes, but I’m only admitting to three.  Cheers!