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: Rifled breech loaders

May 6, 2022

Rifling the Model Armstrong 110pr Cannon.

For reasons which I will not detail here, I am spending more time at home, and much less in my workshop. Work on the Armstrong 110 pr breech loader is progressing, slowly. However, the rifling is complete.

I detailed the rifling setup in a previous model build, but in case you missed it……

The barrel is held in a jig which is clamped to the CNC mill quill. The mill spindle is turned off, for obvious reasons.

The cutter protrudes from a 16mm shaft. The brass bush increases the diameter to 18mm to fit neatly into the bore. I should have remade the entire shaft with 18mm bright steel, but I thought that this modification would work with a lot less trouble. It did. Sort of. The cutter was 3mm wide, and I ground the actual tip to 0.9mm width.

The cutter is mounted to the CNC rotary table with an ER40 collet. The depth of cut is determined by the screw at right, and the maximum depth of cut set with the 2 locked nuts. The mirror is for inspecting the cuts which finished underneath and at rear.

The setup took several sessions to complete. I had previously drilled and D bit finished the bore, and drilled and cut a large thread to accept the breech screw. Then I turned the exterior of the barrel so it would fit the jig. It will be turned to its final shape in a future session.

I could not find actual specs for the twist, so I randomly decided on 90º. The cut started in the powder chamber and finished just beyond the muzzle. The rifling in the original started distal to the projectile chamber, but I had to ignore that due to limitations of my setup in accessing the adjusting screw. The powder chamber and projectile chamber were slightly bigger than the bore in the original, so I might be able to machine away the unwanted rifling in those areas in my model.

30 rifling grooves in the model. The original had 76. But in an 18mm bore the 30 cuts are only 0.9mm wide, and that was as fine as I was prepared to grind the cutter. The cuts are about 0.25mm deep, which is to scale. I will polish the bore later.

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February 13, 2020

Naval Gunnery. A Book Review.

Naval Gunnery.  A Description.  by Captain H. Garbett.  R.N.  360 pages.

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Was originally published in 1897, and is a book which has been considered by academicians and scholars as being of great significance and value to literature.  As such, it has been reproduced by Alpha Editions in an inexpensive, facsimile, paper back edition.

I came across an article about rifled muzzle loading cannons which referenced the book, and led me to purchase it from the Book Depository for $AUD20.

It, the book, is fascinating.  1897 English, is beautiful to read, non ambiguous, and unusually, does not provoke the grammar Nazi in me.

And the book has answered my questions about cannon construction.  Not completely, mind you.  I still do not know how they managed blind rifling.  But most of the first 78 pages are about muzzle loaders, particularly Armstrong muzzle loaders.  With diagrams.

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One question which was answered was about the “recoil tube” located below the barrel of the Port Fairy 80 lb RML’s.  I wondered whether it was like a gas shock absorber.  The book explains that these long cylinders had a piston, and were filled with “Rangoon Oil”, (look it up.  It is in Wikipedia), and they were indeed designed to moderate the rate of recoil of the cannon.

Another fact about rifled cannons…   the rifling causes the projectile to emerge from the cannon slightly to the left or the right of the cannon axis, depending on whether the rifling is clockwise or anti-clockwise.

The book has chapters on breech loaders, naval mountings, quick firing guns, magazines, shell rooms, loading arrangements, sights, powder, cordite, projectiles fuzes, battleship development (up to 1897), battleship organisation and manning.

360 pages, 12 plates (black and white), 113 text illustrations.

If you have an interest in pre-dreadnought naval guns, this book is highly recommended.

 

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