Trunnion Mounts -1
by John
On the Armstrong 80 lb RML model cannon, the trunnions are secured to the carriage with steel brackets riveted to the carriage sides, and the trunnions rotate in a bronze bearing.
The original trunnion on the Port Fairy cannon
These are the component parts.
The RSS ready for cutting out the brackets. And my working drawing, with alterations.
First the 2mm rivet holes were drilled, then the outlines were CNC milled. The steel is 2mm thick.
Tidied the parts with a file and belt sander.
The brackets sitting on a photo of the original Warrnambool cannon.
The bronze bearing involved some basic lathe work.
Then the components were silver soldered together. Delicate work. I did not want the solder running into some areas, and the join needed to retain a degree of precision.
After cooling, sulphuric acid soak, and washing, the top half of the bearing was milled off.
Some filing to make it fit the carriage, then rivet holes drilled with a Dremel while the bracket was clamped in position.
Bolted in position temporarily. Tomorrow I will make the top half of the bracket. The gap between the bracket and the carriage caused by the metal folding will eventually be filled, and invisible. A millimeter or so will be removed from the width of the bracket and bearing.
I had a bit of milling excitement while cutting out the steel components. I was using a 6.35mm 4 flute carbide cutter, and when I started the program the machine plunged into the shape at extremely high speed. When I checked, the feed speed was 60 times higher than I had specified. Somehow, the units had changed from mm/minute, to mm/SECOND. Amazingly, the cut was close to perfect with no damage to the workpiece. But, alas, it wrecked the carbide cutter.
I had recently upgraded the CNC software (Vectric V-Carve Pro) from version 10 to 10.5. Maybe some of my settings in the program had been changed in the upgrade? I never use mm/second. That is a woodworking CNC router unit.
johnsmachines 
mm/sec gets very exciting when you don’t notice the change. That has happened to me a few times, most annoying. These days I always do a quick dry run at a safe Z position.
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Sensible. I should develop the habit.
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Have been caught out a number of times, Lucky the big red button was handy.. One of the things I have been caught out with is bouncing a key when entering an input for a quick manual job, scary what an extra digit can do to the command.
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Yep. Done that too.
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