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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.

Tag: Turkish cannon

Fort Nelson. The Ottoman Bombard revisited.

Just to refresh your memory, if you are a long term reader of johnsmachines.com, this is the model of the Ottoman Bombard which I made several years ago …

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…but it is not finished.  I could not find a picture or drawing of the touch hole anywhere.  Requests to the museum drew no response.

Plus, I had some questions about how the square holes were made.  These were designed for levers to be inserted so the cannon segments could be screwed together.  But were the round pegs cast with the barrel and breech, or were they somehow added later?

Also, I wanted to take a close look at the huge V threads to see if I could work out how they made them.

And frankly, I just wanted to touch it.

It is currently on display at The Fort Nelson Royal Armories Museum near Portsmouth UK.  And I visited it today.  I allowed an hour to inspect the bombard and have a quick look around the rest.  4 hours later I staggered out.  This museum is another fantastic place to visit.  I will do a more complete report in another post. For the moment I will deal with the bombard.

Firstly the touch hole.  Save these photos.  They do not appear anywhere else!

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Not much design finesse there!  The wide opening becomes narrower about 25mm in (just visible).

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Next, the bombard as it was today..and I touched it!

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It is 17′ (5.2m) long, weighs 16.8 tons (17000kg).  It was made in 1465 by Munir Ali, as a copy of the bombards made by Orban, a Christian (Hungarian? German?) for Mehmet 2, the conqueror, who took Constantinople in 1453 on 29 May, (today in Oz).  Orban’s biggest bombard, named Basilica reportedly was 27′ (8.2m) long!

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That’s my hand underneath the “pins”.  Actually levering braces, cast integrally with the breech and barrel.  You can see dents, probably made by the levers.  In doing this I realised that the “pins” are not cylindrical, they are half a cylinder (split lengthwise).  The half cylinders allowed clay or something similar to be placed around the mold, under the half cylinders, and for the gaps between the half cylinders to be filled with clay pieces, to be broken out after the cannon casting.

And the huge threads…

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Well, I am no closer to understanding how these were made.  They are rough and irregular.  I would guess that they were carved in wood, then a clay mold made from the wooden model and baked, then the clay shape used in the final casting, and broken out afterwards.  Any other ideas?

I really enjoyed this visit.  If I have any WordPress storage remaining I will post some photos of some of theother artillery pieces later.

When I finally run out of space, I am afraid that will be the end of my posts.  Thankyou all for following.  It has been great fun posting, and answering comments.

Just in case this is the last post, I have to post these pics of the WW1 British rail gun.  It is truly awesome.

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Cannon caliber 18″.  The Yamato (Japanese WW2 battleship) had 9 guns of this caliber.

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The breech OD  is at least 5′- 6′

 

Turkish Bombard – the barrel mouth

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Except for a name plate I have finshed the bombard.  The floral design at 12, 4 and 8 is not as clear as I wished, and the Arabic script at 2, 6 and 10 is even worse.  But it is cut in wood, and it is a first effort at such work, and it is not easily seen in a model only 106mm 4.2″ diameter, so I am reasonably satisfied.

Also, this was always a prototype, in wood, and I have not totally dismissed the idea of making it in cast iron or brass.  In metal I am sure that the detail work would be a lot finer.

Modelling A Turkish Bombard- The Pins

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There are 16 pins at each end of each section of the cannon.

These were certainly used as leverage points, for very strong men with large levers to rotate the 8-9  tonne segments against each other to engage and tighten the screw.

I cannot see how the pins would have been cast with the breech and barrel.  For my model I decided to make separate pins and fit them into the gap between the big rings, then insert a grub screw through both rings and the pin.  The holes are then filled.

I wonder if a similar method was used in 1464.  I would love to have a close look at the original cannon to figure this out.  From the photographs, I can see no evidence of later insertion of pins, but neither can I see how it would have been done any other way.

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Drilling the holes for the grub screws

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In order to continue with red gum, I made my own pins.  This is the setup.  The blank is held approximately centre in a 4 jaw….

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…and the pins are turned, centre drilled, drilled, cut to length,  and tapped M4.  64 altogether.

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The M4 x 25mm grubscrew is screwed into the pin.  The wood join is super glued.  Also, I am attempting to patch the worst of the thread tearouts.

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Using a battery screwdriver to insert the grub screws.  The pins protrude above the ring surface for a reason..

 

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Sanding the pins flush with the rings.  Check the photo of the original 1464 model.  There is also some wood filler in other splits.  Not surprising after holding up a house for 70 years.

The holes are now filled with wood filler, and will be sanded flush.  They should be invisible after painting.

Next the painting, the stands, and some cannon balls.  How to reproduce that aged copper colour…

 

Bombard Model-3 turning the barrel

Another session or two, and this project is complete.

Now how do I make a cannon ball 62-63 mm diameter?  In wood will be ok?  Does not have to be granite.  I could make a mould and cast it in aluminium or lead, but stone would be authentic…..   thinking.

ps.  Re cannon balls.  I will cast them, in cement!   Now, how to make a mould.

Bombard Model -2. Big Thread

The breech and the barrel are joined with a very large thread.  On my 1:10 scale model it is 60mm diameter, and has a pitch of 6 mm.  These dimensions are measured off Internet photos of the original bombard, so they might not be faithfully accurate to the original bombard.  If anyone has accurate plans of the bombard I would be very interested to hear from them.

I experimented with various spindle speeds, feed rates, depth of cut, and finally decided that red gum wood is not the ideal material to be cutting a thread with sharp points.  However, at 200rpm, and taking 50 cuts to reach the full depth, and using a very sharp tool, the end result was OK.  I will fill the tearouts.

In order to make a functional join in the wooden cannon, I truncated the apex of the thread.  In the gunmetal version I will attempt a more faithful to the original, sharp look.

For some reason, the wood held together better during the internal thread cutting than the external.

 

The male thread was cut on my newly CNC converted lathe,  between centres, but the fixed steady on that lathe was just too small to hold the barrel, so the internal thread was cut on my bigger Chinese lathe.

Next I will bore the barrel to 63mm, then turn the exterior of the barrel.

 

Lathe Conversion to CNC -2 and Wall Smashers

After removing most of the lathe gear which will not be required after the CNC conversion, the lathe is looking a bit naked.

The carriage apron, the lead screw, the back gears, the drive rod and control rods have all been removed.  Also the cross slide screw and handle.  The cross slide itself is temporarily removed, but available for measuring for fitting a ball screw.

I have now made accurate measurements and drawings of the lathe bed and carriage, in order to choose ball screws and nuts for the lead screw and cross slide.

The lead ball screw is easy.  There is plenty of room and machined surfaces for attachment.  I see no particular problems there.  Just time, careful machining and expense.  Chinese or Euro-American?  As usual, there is a big price difference and maybe not such a big quality difference as previously.   Looking at 25 or 32mm diameter, with 550-600mm of thread.

The cross slide ball screw is another matter.  The current cross slide square thread screw is 14mm diameter, and I would like to use a ball screw about the same size.  The problem is that a ball screw nut is considerably bulkier than the existing square thread nut, so some machining of the cross slide will be required to make space.  The cross slide dimensions are already fairly tight, to maximise the swing over the carriage.  I do not want to weaken the cross slide too much.  So it is all a bit tricky.  Time to consider options. And to get another opinion.

No lathe pics, so here are some of Turkish wall smashers.

 

Turkish cannon

This one was given to Queen Victoria by the Turkish sultan.  It was made about a decade after the fall of Constantinople.  It was cast in 2 halves.  There is a giant thread connecting the halves.  I imagine that the strange square holes are to allow levers to be inserted for the screwing by many strong men.  No double entendre  intended.

 

Turkish wall smasher

 

 

Turkish cannon and ball

This one could have been used to make the breach in the wall at the fall of Constantinople 1453.  That stone ball is 600mm diameter.  With no trunnions or other supporting mechanism the barrel was probably dug into the ground for support.  That would allow repeated shots at exactly the same point in the walls.  8-11 shots per day.  It was made for the invading Turks by Orban, a christian who had previously offered his services to the defending Byzantines.  The Byzantines whose empire by this time had been reduced to a tiny fraction plus the city itself, could not afford his services.  The rest is history.

 

 

 

 

 

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