Ratchet Gear.

by John

This was a feature of the model Armstrong RML cannon that I was not looking forward to. (to which I was not looking forward. Plogies to W Churchill. Something about split infinitives).

It is small, cannot be CNC’d with my degree of knowledge, and requires a lot of stuffing around. Which means filing. Or in my case, use of a Dremel.

This is the result after 5-6 attempts. It will have to do.

It is 11mm diameter, and 9mm long. Small and fiddly. And tucked under the cannon carriage out of site. As I said, it will have to do. 2 of them have taken several half days in the
workshop. A bit of a tumble in the gemstone tumbler should pretty it up. (?should up it pretty?). The ratchet on the right slides on a spline. The gear spins freely until it engages with the ratchet.

Occasionally I have a good idea, try it out, and after it works, I think “I should have taken some photos of that for the blog”.

Today I had one of those moments.

This was the result….

This morning, at the GSMEE Zoom meeting, I asked my fellow members where I could obtain some rivets which I could NUT into position. The reason being that some rivets in my cannon chassis are located in impossibly small cavities. And the dome end of the rivets are visible. Apparently “rivet-bolts” are available, but I could not find a supplier by searching my usual suppliers. One GSMEE member had some spares in BA8, but I suspected that I would need more than his small supply. And I was concerned that the dome head size might not match my copper rivets already installed.

Then I had a brainwave! Why not put a thread on my existing copper rivets! So that is what I tried. And it worked!

The biggest issue is not damaging the copper rivet head while holding it and running a threading die down the shaft. The copper is very soft.

The rivets in the photo above have a shaft diameter of 2mm. And the head is easily damaged.

These are Japanese pliers, designed with longitudinal, and transverse grooves. Very useful. Beautifully made. And not cheap. But they do grip. The rivet at the bottom of the top photo is evidence of the gripping power.

So I tried this…..

A bit of electrician’s tape stuck to the jaws, resulted in minimal damage to the rivet head. See the top rivet in the photo.

And a 2mm threading tool was required…

M2 x 0.4 threading tool.

Holding the rivet like this does leave a 4mm non threaded length of rivet shaft, but it can be packed with washers, or something else. It works!

So that was my brilliant idea for today. HEY IT WORKS!