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.

Category: Other stuff

SNORING

Stay with me.  This is about a machine.

For years, maybe decades, SWMBO has been complaining about my snoring, and demanding action.  From her description of the events in our bed, I was experiencing apnoeas (stopping breathing altogether) which lasted up to 20 -30 seconds each time. Sometimes SWMBO wondered if I would actually start breathing again.  Sometimes, she admitted, she wanted to hold a pillow over my head to quieten the snoring.

I have tried nose drops, plastic gadjets to widen my nostrils, elastic straps to support my lower jaw.  I even paid my dentist to make a prosthesis to stop my lower jaw from sagging backwards.  That prosthesis was expensive, and worked a bit.  But it became totally useless after I had some unrelated dental work which changed the fit.

I had heard about CPAP machines being used to treat snoring.  From my work as an obstetrician, I knew about these machines being used to help premature babies with their breathing.  CPAP is an acronym for Continuous Positive Airway Pressure.  It reduces the amount of effort required for each breath of the baby, and has saved many babies’ lives.    At some stage someone found out that CPAP is effective treatment for snoring.

Normally, to obtain a CPAP machine, one has to have sleep studies by spending a night in hospital hooked up to monitors, and be assessed by a medical specialist.

From my wife’s description I had no doubt about my diagnosis, and I decided to self diagnose and treat my condition.   “A lawyer who represents himself has a fool for a client”  also applies to doctors who treat themselves.  And normally I agree with that description.  But in this case I did not relish the thought of a night in hospital, which I was sure, would be pointless because it would be sleepless.

So I discussed my situation with my GP.  And I was pleasantly surprised when he said go ahead with my plan to buy a CPAP machine from overseas, and give it a try.

The CPAP machine cost me $AUD600.  If I had bought it locally it would have cost $AUD 1500-1600.  It arrived about 6 weeks after the order onEbay.  I had no idea what size face mask was required, so I ordered the “medium” size.  Turned out it was  a nose mask, and medium seemed to fit nicely.  The machine itself seemed well made.  All of the plastic bits fitted well.  The electronic screen was clear and lit up quickly on power up.  There was a CD for installation of the software on a Windows computer.  It installed and opened, but would not function.  An enquiry to the seller revealed that the computer time-date setting needed to be in YYYY-MM-DD format, and it all worked well after that.  The program asked for age, height, weight etc.  I was a bit insulted when my BMI of 27 was described as “FAT”.

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The CPAP machine and nose mask.   The tubing is much longer than shown.  The perspex tank contains water to humidify the inspired air.

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The CPAP machine

 

I could find no instructions, so I left the machine on the default settings.  Some weeks later I found an instruction booklet in a side pocket of the storage case, but it did not offer any information about settings.  I guess that normally there would be a doctor doing the settings, based on tests.   Fortunately I have a friend who is using a CPAP machine for sleep apnoea, and the default settings of my machine were very close to the ones which were prescribed for him, so I continued with the default settings.

First night.   I was warned by my friend that it takes about a month to become used to the CPAP, so I was not too perterbed by the mask and tubing waking me up every time I moved.  My wife had the best night’s sleep which she has had in years, because I did not snore AT ALL.  The machine makes a low whirring noise, which is barely noticeable.  Being forced to nose breath, because the positive pressure almost totally stops mouth inspiration, is a very odd sensation, but I was very aware that the 10cm of water pressure was profoundly affecting my breathing.  I was totally unable to deliberately snore while awake, and when asleep I was not snoring at all even when flat on my back.

First week.  I fiddled a bit with the pressures, but the default 10cm water pressure (0.14psi) seemed best.  I used the air humidifier.  The air is filtered.  Several times I woke and ripped the mask off, but after a month of use, that happens rarely.

First month.  I got the software working eventually, and I was delighted to see that I have had no snoring events or apnoea events at all.  My duration of sleep has gradually increased from an hour or two each night, to 5-6 hours per night.    My wife is absolutely rapt.   Her only complaint is that I sometimes remove the CPAP in the morning, then go back to sleep for another hour or two, during which time I revert to snoring.

I like to read in bed for an hour or more before I drop off to sleep.  I cannot wear my reading glasses with the CPAP in place.  So I read until I become sleepy, then pull on the mask and turn on the CPAP.  Usually I am asleep within minutes, which is a big improvement on pre-CPAP.

Either that, or I listen to podcasts with earplugs.  But the CPAP tubing and earplug cables do tend to get a bit tangled, so I usually read.  It helps to pin the CPAP tube to the pillow, with a lot of slack to allow for turning in bed.

So, after a month I have noticed that I never nap during the day, compared with most days pre-CPAP.  My tinnitus (ringing in the ears) is much less pronounced now.  I do not feel sleepy when driving.  I would like to say that my energy levels have improved, but that does not seem different.  I am hoping that my borderline high blood pressure will have settled, when next checked.

Overall, this has been a major improvement in my life. IFLT.  (technology, not Trump).

 

 

Steam Trains

Two of my grandchildren are identical twins.  Here is a recent photo of one of them.  Not much point showing a photo of the other one.  He is identical.

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Not sure which one this is.  They really are identical.  He is planning to join a circus.

Anyway, I had made a wooden train set for my other grandchildren, and my other daughter, the mother of the twins, suggested that the twins should have one also.   I decided to CNC most of the parts, and it was not much more time to make two compared to one, so here they are.

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The design, slightly modified,  is from a book by Jim Makowicki “Making Heirloom Toys”.  The trains are ready for painting by SWMBO.   She is planning to use wood dyes, and finishing with a clear laquer.

The materials are whatever I could find in my workshop, so there is an eclectic mixture of Australian hardwoods, plywood, and pine.   The panels were all CNC milled, and the chimneys and domes were CNC turned.

It has been a fun project.  I will post a photo when they are coloured.

Traction Engine Disappointment

I had inspected a 20 year old traction engine, 3″ scale so about 1.5m long, never been fired, just run on compressed air, and appeared to be in excellent condition.

The seller did not have a price, so after discussing with SWMBO who was surprisingly supportive of my passion, I rang the seller with an offer.  I did not really know what it was worth, but I made what I thought was a reasonable offer.

The seller immediately accepted the offer.

Had I offered too much?

Oh well.  I would press ahead.  I made an arrangement to pay and pick up the engine 4 days later.  I needed some time to get the cash and there was an unavoidable baby sitting day in between.

So 4 days later I hitched up the trailer and set off.  Just as I was driving out the gate, the phone rang once, then a message came through.

The seller had woken up with a bad feeling, and decided to not sell after all.  Asked for a return call.

I was feeling very disappointed and a bit cross, so I did not ring him, but acknowledged the call with a message.

Had I offered too little, and the seller had second thoughts?

Did he really intend to sell in the first place?

A susbsequent email from me has not been answered.

I did consider consulting a lawyer about breach of verbal contract, but there was nothing in writing.  So I am moving on.  Just pissed off.

Now I am looking for another traction engine, preferably requiring completion or repairs.

Heat in the workshop. Heaven!

Today I fired up the pipe heater which I have welded up over the past few days.

Fantastic!!

I was so keen to get warm on this 10 degree celcius day, that I deferred water proofing the flue.

And of course it rained!

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I forgot to bring some newspaper or kindling, so I used a propane torch to get the wood burning.

Within 5 minutes the temperature of the burner was over 200c, and in an hour it was 350 degrees celcius/ 660 fahrenheit.  Heaven.

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The shape of the furnace accepts wood up to 1400mm long.   The handle at the bottom is the ash tray.  The hefty looking handle above is for the furnace door.   The bit of RHS on the floor is so I can open the door when it is hot.

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This is the external sheath of the flue.  The strip of corrugated iron is to separate the hot internal flue from the cooler external layer.

And then it rained!   And I had not installed the waterproofing fitting to the roof.   So water poured down onto the heater, and filled my workshop with steam.!!

Despite today being only 10 deg celcius, I happily machined away until 6pm.  2 hours later than I usually stop due to the cold.

Then I had to go home to cook dinner.   SWMBO was getting hungry.

Another Diversion from The Triple

My model engineering club (GSMEE) has an annual competition build.  This year it is a small horizontal reversing steam engine.

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So I have taken another break from the triple to build the HME.  I have redrawn the plans to make my model 40% bigger, and also to accept metric fasteners.

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The HME blanks for the base, the cylinder block, the flywheel pillar and the flywheel.  The only stainless steel I had in my junkbox, er storage facility, had a  big hole in the middle, so I filled that with brass.

All was going well, and I spent almost a day making the piston head guide. Then finished off by making the guide rod and block.   I decided to take another thou off the guide block, and set the lathe going.

And heard an ominous bang.

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I had forgotten to remove the piston head guide from the from the piston before I restarted the lathe.  Destruction.  The lump at the bottom is another piece of brass, ready to be turned into another head guide.  I had run out of suitably sized brass, so I silver soldered a length of rod to some square section.  A day later and the new piston head guide is now made.  

At least I know from this (and other crashes), that the second part is always made much faster than the first.

And on a different subject, I recently bought on Fleabay a self centering 4 jaw chuck.

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It does not replace the independent jaw 4 jaw chuck for accurate work, but will be useful for turning small square stock.  Also, I plan to make a backing plate for it to fit into the tailstock, so it will hold taps.

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.

Chariot Racing

Another little job for my CNC lathe.

A fellow club member asked me to turn some hub caps for his car restoration.  And the shape was a bit unusual.

This is the first effort at complying with his request.

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It is aluminium, and will be held in position with an O-ring in the groove.

If I had put a knife edge on it he could have justified new car number plates…..

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Metalworking for a cabinet maker

Our model engineering club has been locked out of our club rooms because MOULD has been detected in the building.   Apparently a lengthy process to reduce the mould to acceptable levels.  (note to self…. make sure that the inspectors never set foot in our house).

So our meetings have been held in various locations, including a sports centre and a basketball building.   I feel quite virtuous when I enter these buildings, but for some reason I do not feel any fitter when I exit.

A recent day meeting was held at my farm workshop.  Not my farm anymore, just the buildings.

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Not that one….   the other one.

And one of our more senior members requested a display of CNC machining, from design to product.

So, I drew up a finial which was required to complete a bookcase which I had built 30 years ago.  Then imported the DXF drawing file into “Ezilathe”.

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Showing Stuart Tankard, the author of Ezilathe, scrutinizing my drawing ….  and offering excellent suggestions for improvement using Ezilathe.

Then used Ezilathe to generate the G codes…..

Then to the CNC lathe…..

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CNC turning the finial in 51mm brass rod.  1600rpm, 100mm/min.  Controlled by Mach 3 Turn.  I removed the tailstock shortly after this photo was taken, to permit completion of the ball.

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Some GSMEE members watching the CNC turning.  I spent 3 days clearing up the workshop so the 16 members could fit in.   Amazing how much space was revealed in the workshop.   This is the Taiwanese lathe which I converted to CNC.  See old posts for details of the conversion.

I watched anxiously as the part was gradually revealed.  Admittedly, I had had a test run in wood to check the parameters, but this was the first run in metal.

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The finial.  The bar stock was parted later.

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Bookcase finally finished, after 30 years.

If you are interested in CNC lathe work, you should take a look at “Ezilathe”.  It is superb.

If you are on Facebook, (of course you are if you are reading this), you might like to take a look at the GSMEE Facebook site.

 

Swap Meet Bargains

Yesterday I travelled to Ballarat, (Victoria, Australia) to a swap meet which was held on 22 acres at the airfield.

Most of the stuff in the thousands of sites, was junk from shed and farm cleanouts.  However, despite rapidly walking up and down the rows, I did not quite cover all of the sites.  My Apple watch indicated that I had walked 18km (11.2 miles) and much of that was carrying a backpack full of bought items, so it was no wonder that my ankles were aching at the end of it.

I was really only interested in the few sites which had tools from factory closures.  But my eye was drawn to the very old Caterpillar crawler tractor, a 2 tonner, not too derelict except for a broken exhaust manifold and some rusted growsers.  $AUD9500, so I kept on walking.   Lots of elderly, old and antique cars, motor bikes, and vehicular bits and pieces.

The following photos show most of the stuff which I bought, and some prices (except for the ones which SWMBO must never discover).

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A Japanese woodworker’s chisel.  9 mm wide.  Razer sharp, oak handle.  I buy one of these at each Ballarat swap meet from the same seller, a lovely Japanese woodworker who lives and works in Victoria.  These chisels are a pleasure to use.  $AUD25

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This was a bargain.  A set of good quality English BA open ender spanners, probably unused, for $AUD8

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I dont know what this is called, but it has an INT40 taper, and bolts to the workbench or mill for inserting and removing cutters from the toolholholder, and avoiding the cutter dropping down and being damaged.  Is it a tool setter?  Anyway, $AUD40

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Used but sharp, quality brands.  Carbide ball nose end mill, countersink bit, T slot cutter, and 1/4″ BSP spiral tap. $AUD30

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A new, interesting woodworking cutter, carbide, with left and right hand spirals to avoid surface furring.  $AUD10

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3 Mitutoyo telescoping gauges.  $AUD10

I mulled over a Mitutoyo 1000mm vernier caliper in perfect condition for $AUD300, but decided that it was a wanted rather than needed item, and walked on.

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A box of 12 brand new quality Wiltshire triangular files. $AUD12

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2 very nice Moore and Wright thread gauges, which have BA and Acme threads as well as metric and Imperial angles.  $AUD6

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A box of metric counterbores.  Not cheap, but good price considering the German quality, and condition.  $AUD55

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Small die holder, Sidchrome 10mm spanner, tiny Dowidatadjuster and new box of inserts.  All useful.  About $AUD45

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Chesterman vernier height gauge.  Unusual triangular column. Beautiful condition, complete range of accessories, in a lined box.  Metric and Imperial.  Price not to be dislosed to SWMBO.

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These are brass wick type oilers which I will give to the local Vintage Machinery Society.  No markings.

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My brother was a navigator in the Australian Air Force many years ago, before the age of satellite navigation.  He would sight the stars using a sextant something like this to calculate the plane’s position, while standing in a glass dome in the roof of the aircraft.  (I think that I got that description approximately correct).   He once told me that he would like to have a sextant again, so when I spotted this at the swap meet, and the price was OK, I decided to get it for him.  Maybe it will make up for all of those forgotten birthdays.  So little brother, leave some room in your suitcase when you next visit.  I will leave the clean up and renovation to you.

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Elliott Bros London.

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It looks fairly complete and intact.  Of course I have no idea how it works.

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.

Turkish Bombard. The Barrel Script

Well, I bought a pair of NSK bearings for the Z axis of my CNC mill, and removed the old ones and inserted the new ones.  Cost $AUD 200.  Plus 2 or 3 half  days of  dirty heavy work.    And the problem persisted!!@!@

OK.  Time to get an expert opinion.  Here comes the cavalry.  Thank goodness for my expert friend Stuart T.

Very puzzling.  Even for Stuart.  There was some unwanted movement in the Z axis (about 2mm), despite being apparently properly installed.  Not a problem with the ballscrew or ballnut.  Even Stuart was puzzled.

“have you got any left over bits and pieces?  Is it all installed the way it was before?”

To cut the story short, we installed a thicker washer below the locknuts, and it seemed the problem was fixed.  Or was it?

Today I did another test run of the bombard mouth Arabic script.  Worked fine.  OK.  Time to finish the bombard.

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Here is the finished result, ready for painting.  I have used a 20 degree engraving carbide bit with a 0.2mm flat end.  There is some loss of fine detail but it is I think, adequate.  When it is painted, the filling putty above the pin screws (the white circles) will be invisible.  The engraving took a total of about 60 minutes, at 500mm/minute, 15,000 rpm.

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The setup.   A large angle plate clamped to the table.  The work clamped to the angle plate.

The translation of the Arabic script is “Help O God the Sultan Mehmet Khan son of Murad. The work of Munir Ali in the month of Rejeb. In the year 868.”

Turkish Bombard. The Arabic Script.

A little unfinished business on my model bombard is the Arabic script and floral decoration around the barrel mouth.

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XIX.164 / 19-00164 Detail of muzzle of a great bronze gun. Turkish, dated 1464 Royal Armouries Museum, Leeds LS10 1LT Transparency tr-1185 Imacon Flextight Precision II

This is what I have managed so far….

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It is a practice run in scrap wood.

Some of the detail has disappeared because I used a milling cutter with an end width of 0.5mm.  Next time I will add another step using a cutter with a sharp point, and a lot more of the fine detail will appear.

That pattern took a total of 80 minutes to CNC mill, with the feed rate set at 500 mm/min.

Unfortunately my CNC mill developed a problem with the Z axis, probably due to a worn out end bearing.  I am hoping that it is not the ball screw nut.  Now in the process of removing the bearing. A heavy, awkward, dirty job.

When the mill is working again I will mill the actual bombard model and post some pics.

Computer graphics is not my strong point.  To get the CNC mill to cut that pattern I did the following..

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  1. Enlarged the photo, outlined the tracery and the script, then traced the outline onto tracing paper.  That 550 year old pattern is worn and hard to define in many places.  Quite a bit of guess work.  Lucky that almost no-one can read ancient Arabic script these days.
  2. Scanned the tracing and loaded the scan into Corel Draw
  3. Used Corel Draw to smooth the curves, and make 3 copies in an array of the floral design
  4. Converted the drawing to bitmap file (bmp)
  5. Used V Carve Pro to convert the bmp file to vectors
  6. Used V Carve Pro to generate the CNC G codes
  7. CNC milled the scrap wood at 16000rpm, using a 3.2mm carbide cutter

After the triple

I am back onto the triple expansion steam engine, after putting it aside for most of 2016.  I am guessing that it is about 75% completed.  I have been struggling with this project due to poor plans, no instructions and some lack of skill and knowledge.

When I was well into the project, a colleague pointed out that detailed instructions existed in some articles published in 1985 (Model Engineer, Bertinat).  I obtained the articles, and subsequent progress has been greatly assisted, but unfortunately some errors had already crept into my work, and these have not been easily or completely rectified.

So now I am back into it.  And I would hope to have it finished and working by the end of the year.  Watch for pictures when there is something to show.

I am already thinking about what will follow the triple.  Maybe a Harrison 1 clock? (of “Longitude” fame.)  Looking for some plans.

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Or maybe some more artillery?  How about a working  model  trebuchet?  Now that does have some appeal.  There are some plans on the Net, but they look over simplistic.  I am thinking of a more historically accurate model.  The following picture is from an old French encyclopaedia.  But I might have to abandon my preferred scale of 1:10 because the original was about 12 meters long.  But on the other hand……

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It does have some interesting features.  The ratcheted windlass, the travelling pulley, the trigger mechanism (“pulling the pin”), and the projectile release mechanism (trying to avoid the projectile going up vertically).

 

Model Ottoman Bombard – Painting

I would have preferred that the title of this blog was “Finishing the Ottoman Bombard”, but I am still waiting for the vectors of the barrel mouth decorations and Arabic (?) writing, and the touch hole.

But I have at least painted the bombard, and the pictures follow.  You will notice that I have not attempted to reproduce the bronze or copper colours of the orginal in Fort Nelson.  Partly because I doubted my ability to make painting such variegated patterns realistic, and partly because the cannon would not have looked like that in its heyday of 1464.  It would probably have been either black, like most SBML cannons (smooth bore muzzle loading), or possibly gaudy golds and reds and blues like other medieval items.  So I painted it black.  I like it.  If I get evidence that it should be more colourful I can change it later.

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First coat – Primer.  Hmmm… interesting colour.

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Next coat – matt black brushed on, to fill the hairline wood cracks.  Incidentally, the (dirty) parquetry floor is also made from the red gum house stumps from which the cannon is made.

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final two coats –  matt black, from a spray can. 

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So there it is, finished except for the barrel mouth engraving, and the touch hole.  Now what to do with it…   SWMBO says it might be useful as an umbrella stand.

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The breech.  25mm diameter explosion chamber.  1:10 scale

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The barrel, 63mm bore.

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Assembled.  The model is 520mm long.

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It does need some decoration

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Ottoman Bombard Photo to Vector

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This is the low res photo from Fort Nelson.  High res photo on its way.

In the meantime, I have contracted with a US firm to convert the picture to vectors.  More $US.  ($US50 to be exact).

I am not sure that this is going to work.  But I will report to you.

I do wonder what that the Arabic/Turkish writing means.  Does anyone know?  I am pretty sure  that it is not complimentary to Christians/Westerners/Non Muslims.  Maybe it is just an instruction not to look before the touch hole is touched.  Or “do not stand here”.

PS.  Note added 17 Oct 2016.    The translation is   “Help O God the Sultan Mehmet Khan son of Murad.  The work of Munir Ali in the month of Rejeb.  In the year 868.”

868 = 1464 ce.

 

TURKISH BOMBARD- HELP!

Does anyone have a decent photograph of the writing on the muzzle?

I have repeatedly hunted through every picture which I can find on the net, but they are either taken at an angle, or too poor quality to be useable.

Does anyone have a photograph which I could beg buy or borrow?

I also need a photo of the touch hole.

I have contacted the Fort Nelson Armoury Museum, but not too surprisingly there was no response.

Is there someone in the Portsmouth UK area who could pop in and take some pics for me?

POSTSCRIPT:  October 5.   I have had 2 excellent and positive responses to my appeal.

First, reader Richard sent me a connection to a Turkish Dr/Professor, who has made a 1:25 model of the bombard using 3D printing.  (at least that is how I think he has done it.  My Turkish is non existent).  I am following this lead.

Secondly I have had a response from Fort Nelson Armoury, with a good photo of the barrel mouth, and a high res photo on the way, after payment of a significant, but not unreasonable fee.  Isn’t the Internet wonderful!!

 

TURKISH BOMBARD – the real thing

I have found this video to be particularly useful in my modelling of the Ottoman bombard. The subject of this video is the gun that the Turkish sultan gifted to Queen Victoria when the Brits and the Turks were allies.  It might be one of the guns which fired on the British fleet in 1807, when it (the gun) was 343 years old!

Notice the colour.  It is aged bronze.  I am thinking about how to reproduce that colour on my model.

 

Length of the assembled gun 5.2m (17′)

Bore 635mm

Breech weight 8942kg

Barrel weight 8128kg

Average weight of shot 307kg

the model is at a scale of 1:10.  photos soon.  being painted.

 

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…

 

Modelling a Turkish Bombard -4 Decoration

The decoration around the barrel is formed by a repeating pattern, which when milled, very cleverly forms 2 identical patterns.  One is excavated and one is the original barrel surface.  You will see what I mean if you look at the pictures in the earlier blog, and the video below.

It took me an evening of experimenting on the computer to work out the system and draw it.

bombard-pattern3

Then I measured the diameters of the 2 gun components, calculated the circumference, (OK it is not rocket science.   3.142 times diameter), then working out the number of identical shapes which would fit around the 2 different diameters, at the same size and spacing.   Amazingly, it took 18 shapes to fit almost exactly around the barrel, and 16 of identical size almost exactly around the breech.  the angular spacing was 20 degrees and 22.5 degrees.

Then the shape was imported into V-Carve Pro, and G codes were generated.

My CNC mill does not have a 4th axis, so I used a dividing head to move the workpiece at the precise angles.  See the setup in the video.  That meant that the pattern was engraved into 16 and 18 flat surfaces, rather than a continuous cylinder as on the original.

It worked very well.  There were minor compromises due to the shapes being milled with a fine end mill but when you look at the pics I hope that you will agree that it is effective.

I calculated that the milling had to be at a maximum depth of 2mm in order to cope with the curvature, but if I do it again,  I would reduce the depth by 25%.

The first part of the video is a shot of CNC drilling.  Then the CNC routing of the repeating patterns.  Each angular setting of the pattern took 4 minutes to complete.  136 minutes altogether.  In reality, it took a whole day, most of which was spent doing the setups.

 

 

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.