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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: CNC turning

Trevithick Boiler End

The first part to be made for the Trevithick dredger engine is the domed end of the boiler.  It is formed from copper plate which is 3mm thick.  first a circle is marked out, then bandsawn from the copper plate.

I decided to make a wooden form.  Fortunately I have a CNC lathe (see earlier posts about the CNC conversion of a manual lathe), so drawing the profile and generating the G code using Ezilathe was, well, easy.

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CNC’ing the wooden form for the boiler end plate.  The roughing steps.  Carbide tip which has been sharpened to a cutting edge, suitable for wood.

This is the final roughing cut, and starting the finishing cut.

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CNC turning.  Light sanding required to remove the fur.  The wood is European oak.  Central hole for a locating pin.

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The oak form was attached to a red gum block which was held in a 6″ vise.  I have already commenced shaping the copper disk here.  The copper is cramped to the oak form after annealing, and gradually hammered to shape.  Tapped rather than hammering.

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My “forge” is a few fire bricks in a steel shell, and a roof of steel to help retain the heat.  The torch is fuelled with propane.  It was originally a weed flamer, used to burn serrated tussock.

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Red heat was achieved in 90 seconds.  This is 600 degrees centigrade.  copper melts at 1084c, so there is a good safe margin.  I quenched to cool, for speed.

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This welder’s clamp proved to be the most effective method of holding the copper disk to the form.  I fitted  copper and  brass heads to the tapping hammer to minimise the chance of “bruising” the copper.

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Progress

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About 10-12 heating-hammering cycles in 1.5 hours to get to this stage.

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Getting close.  I will finish it tomorrow.  Might wash up before cooking dinner.

Making Hubcaps

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I made 5 of these

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The 50mm diameter aluminium blank had a 12mm bolt inserted into a blind threaded hole.  The bolt was held in the lathe chuck.

The 2 short videos which follow show 1. the final rough cut 2. the finish cut.

The shape was drawn as a DXF file using CAD, the G code was generated using Ezilathe, and the lathe was controlled with Mach3.

 

 

Total CNC turning time was 16 minutes per hubcap, plus cutting the groove for the O-ring, then a quick polish with a cleaning pad.

Bombard Model. Turning the Breech

 

So if you watched the video, you can see that I have a problem with the big thread between the breech and the barrel, at least in the wooden prototype.  It might work better in brass or gunmetal.

The thread has a pitch of 6mm and a diameter of 60mm.   It is big.

My plan at this time, is to make a brass male threaded section, and glue or screw it into the breech.  Then to make a steel tap using the same G code, and cut a thread into the wood of the barrel.  (p.s.  note 30 Sep…  I continued to experiment with feeds, speeds, and cutter shapes in the wood.  The final result was OK so I did not make  metal threads.  That will have to wait until I do this project entirely in gunmetal or brass…  maybe never)

CARRONADE 1

It has been a while since I posted, but I have been busy.

Some of that has been in the workshop making a scale model carronade.

A carronade, in case you are wondering, was a muzzle loading cannon, made 1776-1852 in the Scottish town of Carron, by the Carron company.  And subsequently much copied elsewhere.

It is a cannon which is short, squat and ugly.

Weighs about 1/3 as much as an equivalent bore long gun, (see previous posts), requires only 3 men to operate (compared to 9-11 for a long gun), and can fire balls or other nasties at 3 times the rate as long guns.

2 carronades, 68 pounders,  were on the foredeck of Nelson’s “Victory”, and they caused huge damage  at Trafalgar.   Can you imagine loading a 68 pound cannon ball into the muzzle of a hot cannon?   Many actions proved the killing power of carronades, and the British Admiralty were so impressed that they replaced long guns with carronades on many of their ships.

The French, and Americans were less rapid to  access this new technology, although Napoleon, who was an artillery officer, was adamant that the French navy should have the carronades installed as quickly as possible.

The British equipped some of their ships almost exclusively with carronades, and at close quarters they were devastating and they won some notable victories.

Unfortunately, although they were devastating at close quarters, they did not have the accuracy or range of long guns beyond about 500 meters.

So in the war between the Brits and the Yanks in 1812, the Americans found that all they had to do to win at sea and on the Great Lakes, was for their frigates to remain beyond the carronade range, and shoot their long guns, with many victories, and great frustration of the Brits, who were not used to losing naval battles.

Carronades were commonly installed on merchant ships, privateers, pirate ships, and small naval vessels, due to their relatively light weight, and small gun crew. But the Royal Navy stopped using them from 1852, when breech loaders were the latest new technology being installed wherever possible.

I decided to make another 1:10 scale model cannon.  A 32 pounder carronade, the same scale as the previously blogged 24 pounder long gun, to put them side by side for comparison.

It is almost finished.  I will post some photos soon.  Look forward to squat and ugly.

 

 

Cannon trunnion shoulders, flash pan and trunnion brackets.

Another couple of long and very enjoyable workshop days, making various bits for the 1779 24 pounder model naval cannon.

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The trunnion shoulders were bored to a close fit on the trunnions, then the barrel curve was machined on the vertical mill.

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Using a boring head to make the barrel curve.

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Testing the barrel curve.  A good fit.

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The trunnion shoulders were glued into position with Loctite.

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The trunnion bands were difficult and fiddly.  The 3 components of each were joined with silver solder, then several hours was spent with tiny  files to achieve the shape pictured.

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The square cap trunnion bolts are yet to be made.

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Milling the powder pan enclosure with a 2.3mm end mill.

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The powder pan, sculptured from bar stock.  The base gets milled away.

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The powder pan is glued into place with Loctite.

As you can see, this cannon project is almost completed.  A few more hours to make some bolts and fittings.  I am considering adding some ropes and pulley blocks.

Turning a cannon barrel

Today the exterior surface of the model 1779 naval cannon barrel was turned.

The piece of brass material weighed 5.1kg, was 300mm long and 50.8mm diameter.

I had used Loctite to glue a spigott in the bore, to provide a center and a driving diameter which the small CNC lathe would accept.

Although the lathe was nominally 300m between centres, the toolpost would move only about 200mm.  So the turning had to be accomplished by turning the cannon mouth end first, and then reversing the workpiece to turn the breech end.

The CNC lathe, owned by Bob Julian,  is about 30 years old, and it came out of a school.  In the course of this  job, it seemed to progressively free up, making us suspect that this is possibly the first time it has ever been seriously used.

The lathe electronics had been replaced by Stuart Tankard to use Mach3.  The G codes were generated by Stuart’s program “Ezilathe”, which is available as a free download on “CNC Zone”.   It is an excellent CNC lathe program, and I thoroughly recommend it.

I will eventually post some videos of the turning progress, but my Oz internet connection is so slow, that for the moment I will post photos only.

I started by turning a piece of rubbishy pine as a test.

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That’s me, watching carefully.  Later we installed the swarf cover.

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The metal turning lathe does not miss a beat chomping through wood.  These are the roughing cuts.  F300mm/min, S800/min.

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The Mach3 picture of progress.

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The finished distal half of the cannon barrel in pine.  If I stuff up the brass version at least I can have a wooden barrel. 

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Roughing the barrel in brass.  1mm cuts, feed 100mm/min.  It took almost 50 minutes for this section, and about 15 minutes for the breech section.

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The barrel mouth.  No gouging resulting from the 22 degree HSS cutter.

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Finish was quite good.  Will require minimal polishing with ScotchBrite.

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The workpiece was reversed in the lathe, the Z zero carefully set, the X unchanged, and the breech end turned.

The starting weight was 5.1kg.  The end weight, including the spigott was 2.9kg.  So at least 2kg of brass swarf, most of which I swept up and saved for possible future use.

Next to machine the trunions and some silver soldering.

 

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