johnsmachines

machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment. I read every comment and respond to most.

Tag: Model Armstrong RML

Gunners Platform

Not a great photo of the platform at the rear of the Armstrong 80lb RML at Portland Victoria. But, this is what I started modelling today.
This is the Port Fairy cannon, which is missing the woodwork, but shows the brackets.
These are the brackets which I fabricated for the 1:10 model. I did make some small design changes to make the model. I think that my changes are an improvement on the original, using existing fasteners. The wooden planks and vertical handles are yet to be added.

The central angle brackets are machined from some RSS.

75x25x2mm RSS
Sawed and machined to size. The bent steel is true to the original Port Fairy cannon.

You might also notice that the eye bolts have been added.

Armstrong RML Elevation Protractor

2 days in the workshop, and not much to show…. just one photo.

Yes, the trolley wheel axles need to be shortened. Next time the carriage is disassembled. The recoil tube is just sitting there, for effect.

The curved brass bar is a protractor for measuring degrees of elevation of the barrel. I used High School trigonometry to work out the distance from the pivot point at the centre of the trunnion, to the pivot centre at the fitting under the barrel.

Then cut out the shape from 2mm brass with the CNC mill. That was the easy bit. Although it did takes 3 goes to get the radius of the curve correct.

Today, although feeling depressed after the Cats loss last night, I made the cross bar with the rectangular cutout, then spent a couple of hours bolting it into place. It all works smoothly. The rectangular cutout is 2.2mm wide and 7mm long. I chain drilled with a 2mm carbide milling bit, then milled the slot sides, then filed the corners square. It is stainless steel. Slow work.

I have not worked out how to engrave the protractor marks, which are at 0.25º intervals for elevation, and whole degrees for depression. I could ask Stuart T to engrave it for me. The design and actual lasering would be straight forward, and I am sure that Stuart would help if requested. The problem would be to align the part on the laser machine, so that the engraving occurred exactly at the correct location. Actually, as I type this, I think that I have the solution. Watch this space.

I need to make a pointer next, and to determine the 0º position. The carriage sits on the chassis which is at a 4º slope. Not rocket science, or brain surgery. Just need to get it right!