johnsmachines

I decided (well, to be truthful, SWMBO decided) that I needed to fix the gates which divided our front and back yards.  They were about 80 years old, and I had rebuilt them soon after we moved in 40 years ago.  About a decade ago I installed tensioning wires on a turnbuckle to counteract the sagging, but wear and tear and lack of maintenance painting had resulted in the main joints rotting, and so I decided not to fix them again, but to replace them.

They are actually falling apart.

I have been progressively getting all of the iron railings around the house stripped, dipped in molten zinc, and powder coat painted.  For some reason the molten zinc dip is termed “galvanizing” here.

So the new gates would be made with steel SHS (square hollow section) frames, and aluminium slats.  I would happily have just copied the old wooden frame design, but SWMBO, who is an architect, decided that would not be “right” in steel, and that the steel frame would have to be the same shape as the surrounding brickwork, which is a sort of Tudor arch.  Why we have Tudor arches in Oz is a mystery.  Except that back in the 20th century, there was a “British to the boot straps” cultural cringe, and lots of the aspirational class houses tried to look as British as possible.  Paradoxically, although I am a confirmed  republican, I quite like the “mock Tudor” design.  And the house remains cool even in stinking hot weather…. but I diverge.

There has been some ground movement over the years, with the result that the arch is no longer symmetrical, so each gate is different.  So I used thin MDF to trace the arch shape for each gate.

With the MDF pattern, I attempted to roll the arch shape in the 50×50 SHS (2″ x 2″), but that was a failure.  The SHS did eventually eventually develop a curve, but at the cost of so much lateral distortion, bulging at the sides, that it looked terrible.

So I used a technique that I had used years ago when I made classical guitars, that is to make multiple cuts in the material leaving a thin intact edge, and then making the bends.  Each gate required 13  cuts.

The steel SHS, roughly bent after making the multiple cuts.

Then a wire bowstring and turnbuckle were used to hold the shape, while tack welding.  The turnbuckle was adjusted after each cut was welded, to get the curve as close as possible to the line on the MDF.  Earth clamp at bottom, turnbuckle at top.

The curve is not absolutely smooth, but it satisfied SWMBO.  Lucky that her eyesight is not so sharp these days.

After welding the frames, the the frames and hinges were G clamped into position.  I used the original blacksmithed hinges.  The hinges were welded, and the frames were finish welded.  My eyesight is not too good either, and my welding shows it.

The aluminium slats were drilled, temporarily screwed on, and shaped.  The catches and bolts were temporarily attached, then the whole lot was disassembled. 

The steel was hot zinc dipped, then after some finishing with a file, the steel and aluminium parts were powder coated.

The whole process took about 2 weeks.

Almost finished.  SWMBO is satisfied.  Phew.

Now back to the cannon.