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. n.b. There is a list of my first 800 posts in my post of 17 June 2021, titled "800 Posts"

Tag: cannon sights

November 23, 2024

CNC Mini Mill -7

A few subjects to update, including the mini mill build, the USS Constitution, the 110pr Armstrong gun model, and plans for another ship modelling machine.

The CNC Mini Mill. The mill itself is finished. I had to replace all of the linear bearings and 8mm hardened steel rods because the play was excessive. I knew that the first shipment of 8mm rods from AliExpress were undersized (7.97mm) and all had a detectable bend. AliE offered to refund if I returned them, but I decided to just try a different AliE supplier. The next lot of 6 x400 x8mm were again a bit undersized at 7.98mm, and were not bent, but still the play was excessive. Slow learner, I tried again with another order and called it quits when they came in at 7.99mm (new Mitutoyo micrometer). But there was still excessive play, so I wondered about the linear bearings. Stuart T came to the rescue with some leftovers from his build of the mini mill, and they solved the problem. No detectable play at all. So it was both the steel rods AND the bearings at fault. Anyway, all fixed. And now I have 20 dodgy spare linear bearings, and 12 dodgy steel rods. Stuart said to bin the lot. But I can’t quite do that, so into the workshop supplies for the time being.

Also, I have now copied Stuart’s design for the electronic controls, and set them up in a nice plastic box with a transparent lid. SO many exciting coloured lights that I want to be able to see them at a glance.

There is a power transformer under the alu shelf, and on top are 4 stepper motor modules (foreground), the CNC controller and breakout board, rear. Also a computer fan, power switch and fuse, E stop panic button, 25db connector for the pendant control, and Ethernet port to connect to the computer.

The only things missing are the bits to transport the electrons around the place. Will happen soon! Then have to decide just what this machine is going to be used for. Yeah yeah. Another tool looking for something to do.

Constitution has had a rest while I have working on the mini mill. But in the past week I have been busy making masts and fighting tops, and trying to decide on the order of glueing bits together. Bowsprit and 3 more vertical masts almost finished. But no stays yet in place. The instructions say to totally finish the hull and fittings before commencing the rigging. Oh, have I mentioned that I made a ropewalk for making the models fixed and running rigging, as well as the cables? I forget. Well, the fixed rigging gets installed first, and some of those big ropes are totally served (are totally covered with thin rope to increase their resistance to water ingress, and rotting, and increase longevity. Did you know that a ship of Constitution’s size had approx 50km of rope, and the average life of a rope of the era was only 5 years!

As well as serving the ship’s ropes, there is a process called seizing. Best to look at a picture…

Securing a rope end by doubling it back on itself, and binding the 2 parts together with smaller rope is called seizing.

I tried my hand at seizing, but was totally dissatisfied with the result.

Seizing on the 3 bowsprit stays. Pretty lumpy and crappy. Got to be a better method. Also my effort at micro painting. That stars and stripes is about 10x7mm. A bit sad considering that these hands used to do microsurgery.

So, a machine to do seizing and serving (and worming or snaking and parcelling, but more about those later), is in my plans. Another machine is being planned. CNC again. And the control box listed above will control the seizing/ serving machine. More about that in a future post.

Finally, and incredibly exciting, is that my post about modelling the sights on my 110pr Armstrong cannon in 2022 https://johnsmachines.com/2022/10/25/model-armstrong-110pr-sights/ has prompted a response from a UK reader who has recently purchased a tangent sight from an online auction, and he has identified it as coming from an 1867 Armstrong 110pr cannon. In researching the sight Daryl came across my modelling posts, and he has contacted me, forwarding some photographs. Just to remind you, this is what I modelled, from line drawings published in the 19th century…

Yes, the left hand tangent sight does cant slightly more than the right. As intended.

And here are some photographs taken by and reproduced here with permission by Daryl Pendlebury-Jones of his purchase…..

The rear tangent sight, approx 500mm long. Gunmetal. Daryl notes that the notched top (top left) slides nicely and freely. And the markings are still clear.
Lateral view, notched top at bottom right.

I might have to remake the sights on my model now that I have seen these pics.

4 Comments
July 3, 2021

Armstrong RML Cannon Sights

The sights were the final parts to be made for the model Armstrong RML.

There were reasons for delaying these items. They are tiny, easily dropped and lost, have tiny almost invisible details (to my eyes), and involve fine and very deep drilling into the barrel, on which many hours have previously been expended.

First I looked up every reference I could find about the full size originals. I could find no picture of the sights on the 80pr Armstrong, but I did find some diagrams of the sights on the Armstrong 64pr, on which the 80pr was based. Another problem was that there were rapid developments in sight technology, and I had to decide which period I would choose. The later periods (after 1880) had complexities which did not exist in 1860. In the end I just made decisions, knowing that they might not be exactly correct, but thinking that if further information surfaces I could make and install new sights.

This is the design I chose. The 64 pr had 3 pairs of sights, the 80 pr had only one pair, on the right hand side.

The next step was to drill some 2mm and 3mm holes into the barrel.

The drilling setup. The barrel was held firmly between brass strips. The breech end of the barrel might need a bit more finishing.

First I milled 3mm flats. The first milling bit, solid carbide, just snapped as it bit into the barrel from the side. A HSS bit was more long lived.

A complication was that the foresight was vertical, but the hindsight was sloped 2º inwards to adjust for slight lateral deviation of the projectile which results from the rifling.

Next, a 2mm hole was drilled right through the barrel, missing the bore, and exiting through the bronze bracket which supports the elevation quadrant gear. At 40mm deep that hole qualifies as deep drilling. Tension drilling.

I did not have a long series 2mm drill bit, so I silver soldered an extension, leaving 40mm of the 2mm bit exposed. No photos of the deep drilling. I had other things on which to concentrate. The drilling was actually uneventful.


Showing the drill sitting in the hole
Fabricating the sights involved silver soldering 0.5mm brass strip to 2mm stainless steel rod. This was the soldering setup. The the sights were shaped by belt sanding and filing.

And now for some sights of the sights on site.

I will polish the sights.
Apart from dusting the base, and some final polishing, the model Armstrong cannon is now completed.

8 Comments
November 23, 2020

Sights Set On Completion

Today the gunners’ platform at the rear of the chassis was completed and fitted. It has vertical handles at each side, presumably for the gunners to steady themselves, while aiming the cannon.

The platform, ready to be attached to the chassis. The wood here is Australian Jarrah. The handles are stainless steel, discoloured from silver soldering them to the side brackets. They will eventually be painted. ps. a day later I decided that the fasteners were too big, so I have replaced them with something more appropriate. Pics later.
The platform in position. This photo shows up my first efforts at riveting. Some of those rivets will be replaced when everything is disassembled prior to painting. Those brass nuts holding the wooden boards are too big and will be replaced also.

So, just 2 more parts to be made for this model cannon. Those are the sights.

The information which I have to base the sights on is a bit sketchy. But I do have photos showing these cylindrical holes in the Port Fairy cannons….

The sights are placed in the holes in the right hand trunnion shoulder, and in the breech.

After extensive searching I found several books which were published in the 19th century. This is the best diagram which I found of the rear sight. It is calibrated vertically up to 3600 yards, and there are lateral adjustments to take into account speed of movement of the enemy. The sight is angled at 2+º to the left to compensate for the rifling, which causes the projectile to deviate to the right. The front sight is located in a relatively shallow cylindrical hole. The front sight is a fairly simple point.
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