Today I poured 3 cylinders of brass to make 12 chess pieces. 8 pawns and 4 rooks. It was a total failure.
A model engineering friend had donated 3.3kg of brass, in the form of spent cartridges.
This is the first pour which I have done in 3-4 months. It was ambitious, requiring 3.25kg of investment powder, and 3 large cylinders. But these pieces will all be redone, with new 3D prints, and recasting. The failed pieces will be remelted.
I think that the main problem was that the investment mixture which I painted onto the prints was too thick, and did not penetrate all of the surface features. And the painting was not adequately thorough, leaving bare areas which predisposed to bubbles.
And the main bulk of the investment mixture was too thick. I did mix it a bit longer than usual because of the volume involved, and I did notice that it seemed more viscous than usual, and when vacuumed, the bubbles never really stopped coming.
The voids occurred mainly at the bottom of the cylinders, which indicates I think, a need for ventilation tubes. I had stopped using those for bronze pours, but maybe for brass they are necessary.
So, at this moment I feel that it was a wasted day. But I have learned some things, and have a plan for the next pours.
And I was very satisfied with the quality of the brass from the cartridges. Hopefully that will continue as a source.
Since New Year I have been slowly completing the model Armstrong 80Pr RML cannon which I am intending to keep for myself. The first example was given as a present to my daughter and son in law.
I expected that the 2nd example would be finished much more quickly than the first.
After all, most of the difficult design, casting, and machining decisions had been made first time round. And I had made extensive notes, diagrams, and photographs first time round.
However, there were a few obstacles to rapid completion…..
I had made some design changes. Always risky. Always time consuming.
I could not find some notes and photographs which I was sure I had carefully filed away.
I could not remember how I had made some tricky small shapes, and had to reinvent some methods. In some cases that triggered a memory of the first method, and I realised that I had reinvented the first method.
SWMBO had other ideas about the best method of using my time, and making model cannons did not enter her equations.
I made some brand new mistakes, which had to be rectified.
But, here I am, very close to final teardown, and then for final assembly and completion.
With respect to final painting, finishes etc. SWMBO has made a strong pitch for the same finishes as model 1. My inclination was to aim for authenticity, and paint most of the model. SWMBO wins, as usual. “It has to look interesting and beautiful, not boring black.”
So here are some pre-teardown photos.
Almost finished the kitchen for SWMBO, so I should be free to finish my Armstrong 80pr RML in the next few weeks.
Meanwhile the computer which runs my CNC lathe went “bang” when I last turned it on, and it is dead. It is close to 20 years old, and it lived in an environment full of dust, swarf, mice, damp, and the odd tiger snake. Originally ran on Windows XP (some of you remember that one?). So I will install another oldish laptop to run the lathe, and will change from the parallel port interface to a “Smooth Stepper”, thus joining the 21st century. (I do hope that Stuart, my expert friend, is reading this.)
Very few posts lately. SWMBO (SHE who must be obeyed) has me assembling and installing another kitchen. I have lost count, but I think that this must be the 7th or 8th. And the problem is that I showed some aptitude for the job with the first one, and have got better with each successive one.
It is not that kitchens are not important. I get that. It is just that I would prefer to spend my time making model cannons and casting chess pieces.
Next step, to paint the PLA models with investment medium, then fill the flasks with medium and let it set overnight.
Incidentally, I tried several methods of cleaning up the PLA.
Soaking in acetone – waste of time.
Sanding and filing- effective, but very time consuming.
Using a heat gun – caused the entire model to heat up, with resulting distortion.
Using a flame gun, propane torch – very hot, so extremely brief exposure, maybe 1 second. This was my best method. It melted the tiny zits, burned the loose strands and removed some, and made the rest easy to finger nail off. A bit tricky. You don’t end up with much hair on your hands.
The white pieces were printed several weeks ago, then the black pawns. But I had 2 failed runs when printing the black major pieces. The failures seemed to be caused by failed adhesion of the pieces to the platform. In each case, the runs were progressing nicely, but failed after about 20 hours, in the middle of the night, covering the 7/8th completed pieces with PLA spaghetti.
The settings were exactly the same as the white pieces, so why the sudden failures? Is the black PLA different in some way?
So I asked my colleagues at the GSMEE. (Geelong Society of Model and Experimental Engineers), some of whom are experienced 3d printers. It was suggested that perhaps I had turned on the cooling fan too soon, after layer 1. So I changed the setting so the fan did not come on until after the platform and one layer of the pieces had been completed. And the result was excellent! See the photo.T
Of course the colour of the PLA is irrelevant. The PLA will be melted, vapourised and burned out after the molds are made. But I could not resist the opportunity for a photograph.
Next, to make the wax and PLA trees, and make the molds.
Still thinking about what metals to choose, and how to colour them. The pieces could be used just as they are, but I really want to feel the weight of real metal pieces.
And although I claim that the 3d printing is complete, the assumption is that there will be no casting failures. I could well be printing more pieces.
I have been bush camping for a few days on the Murray River. About 550km from home. Ki Bend, Hattah-Murray National Park. I might write about it in a later post.
On the way home I visited a shed at Murtoa, a small, pretty town in the wheat belt of the Wimmera. It is called the “Stick Shed”. Sometimes called the “Wimmera Cathedral”.
The exterior is large, but drab and rather boring. Rusting corrugated iron roof with some repaired sections.
It IS large. 270m (870′) long, 60m (196′) wide and 20m (65′) high.
Australia is a grain exporting nation. During WW2, shipping exports were dangerous, and limited. For obvious reasons there were no exports to Japan. And we had some bumper harvests. Anticipating a large harvest in 1941, 26 of these huge storage facilities were built. This one at Murtoa was the first, and is the only one remaining. It covers 4 acres. The largest facility covered 10 acres. The Murtoa facility has not been used since 1989 and it was falling into serious disrepair. The owners wanted it demolished, but activists lobbied to have it preserved and in 2014 it was placed on the National Heritage Registry. Substantial repairs have been undertaken.
The interior is awesome.
There are 560 mountain ash tree trunks up to 20m long, supporting the roof. Many have been repaired with concrete bases, steel supports, bolts and trusses. Some have been replaced with steel posts, because suitable tree trunks are difficult to source. Lighting is through skylights and some wall windows. The floor is 4″ thick concrete.
Wheat was piled high, up to 92,500 tonnes, right up to the top of the roof. The roof angle was determined by the “natural angle of repose” of the piled wheat. Delivered by truck or train. The wheat was elevated by conveyors, powered by a steam engine. Initially the facility was vermin proof. Workers could walk on the surface of the wheat, despite sinking up to 500mm and vermin sprays and ventilation prevented infestation.
Some old photos were on display.
The construction was completed in 4 months. The facility was full within 6 months.
If you have the opportunity to see this amazing building, just go.
Each piece takes 2.5 – 4 hours to print at the high resolution which I require to produce a good finish. The printed pieces will be attached to a tree, then encased in jeweller’s casting medium inside a steel cylinder. When set, the cylinder is heated to 200-300ºc to melt and vaporise the PLA, producing a cavity in the casting medium, into which the molten metal will be poured. The mould is baked for about 6 hours to thoroughly dry and harden it before the metal is poured into it.
There are 16 pieces in each army of a chess set. So 64 hours of printing for each colour. Plus failures. So far, in about 5 days of printing, I have produced the whites. That has taken almost 1kg of PLA, one roll. PLA is not expensive. I paid about $AUD22 per roll, including postage. Lately prices have risen to around $AUD30 per roll.
I have been teaching my 5 year old grandsons to play chess. It started with checkers, but the little buggers are already beating me at that! So I have upped the ante and introduced chess.
Then I thought that a chess set might make a nice present. So I explored THINGIVERSE and found these Egyptian styled pieces. Free download. And I have been printing them. I intend to cast them in bronze and aluminium.
The detail and quality of these Thingiverse STL’s is superb!
In December I experienced several days of feeling unbalanced, staggery. A bit like being tipsy, but no alcohol involved. It passed after 4 days, but I attended my GP in the New Year for a checkup, and mentioned the experience. He arranged the MRI (magnetic resonance imaging) of my brain. 2 weeks later I was wheeled into the MRI magnet, and after 30 minutes of mechanical clanking and banging, it was over. No big deal. I was sure that it would all be normal.
Somewhat to my surprise, the MRI was reported that I had experienced a small bleed in my brain, a stroke, a cerebrovascular accident. A disease of old age. (70). No residual effects this time. But might happen again. It seemed that I might get the answer to THE BIG QUESTION sooner than previously anticipated.
Must get that model cannon finished!
But there is more to this story….
I am not a radiologist. Not even a registered doctor since retirement. But I could not see a bleed on the pictures. Oh well. You have to trust the experts. And gynaecologists are not renowned for their expertise in neurological radiology.
Then, as recommended by my GP, I consulted a specialist neurologist, and had a very thorough neurological assessment. He could find nothing abnormal. An interesting part of the assessment was a cognitive test, apparently the same one that Donald Trump took, after which he announced that he was a genius. Apparently I passed. It was laughably simple.
Most interestingly the neurologist could not see the bleed on the films. So then the films were examined by another specialist radiologist, and he/she could NOT see the bleed.
So, either the diagnosis was debatable, or non existent. The original symptoms were too vague to be diagnostic.
It just demonstrates the old adage. If in doubt, get another opinion.
Apparently the MRI set most of the nucleii in my brain spinning. See the following YouTube video. Sabine Hossenfelder is a German physicist and a brilliant teacher. Worth checking out her other YouTube videos.
Since then I have had no recurrence of the original symptoms.
The manual/handbook is undated, but it was printed for the Warrnambool Battery, and lists the iron carriage and slide, so that dates it after 1875. Before that the slides were wooden.
The following is my precis of the interesting specifications. A full copy of the Handbook is available on request
The weights given are: barrel 80cwt, carriage 41cwt, slide 74 1/4 cwt. So, the total weight of the cannon = 195.25cwt = 9.92tonnes (9.76 UK tons). That is the only document which I have discovered which specifies the overall weight, it is interesting to me because it explains why my model weighs close to 10kg. 10kg is close to 1/1000th of the full size weight, which is what is predicted from the model 1 in 10 scale!
Other specifications include: calibre 6.3″; total length 9’6″; 3 rifling grooves with a twist of 1 in 35 calibres, vertical vent 6″ from end of bore.
The sights are located only on the right side, and the tangent site is angled at 2º to the left. (to compensate for the projectile deviation resulting from rifling).
The hydraulic buffer piston had 4 drilled holes. The diameter of the holes was determined by test firing. The cylinder was filled with SOAPY WATER, (not Rangoon oil, which other cannons used).
The slide is of iron, except for the top ‘T’s which are steel.
The brake band permits the carriage to run back, and tightens automatically after recoil to retain it. A hand brake lever controls running up. (? should be running down?).
Barrel elevations: 5º down, 30º elevation, 19º down for loading. (Oops. I had set 17º as the loading angle. Hope that is not a hanging offence)
Charges: Full 20lbs; reduced 16lbs 12lbs, saluting 8lbs.
Projectiles: Studless. With gas checks. (which is further evidence that the manual is post 1875). 80-86lbs,
Fuzes: Percussion or timed (15 seconds).
Penetration of wrought iron plates: At range 0 – 8.5″; range 1500yds – 6.75″; 3000yds -5″; 4500 yds 4.25″.
The manual then lists the procedures for the gun crews. I will summarise those in the next post.
with grateful thanks to Marten Syme, historian, for sending me a copy of the handbook.
The elevating gear is a quadrant gear, and it is centered on the trunnion centre. This is how I set it up on the model Armstrong RML 80 pounder. There are probably other better ways of achieving the result, but this is how I did it .
This is the second 80pd Armstrong RML model which I am finishing, this time for myself. It should be straight forward, having done it all before, but it is like a new adventure. Ah the joys of memory loss. Everything is new.
Actually, the full title of the book is “Treatise On the Construction and Manufacture of Ordnance in the British Service prepared in the Royal Gun Factory” by John Fletcher Owen. Originally published in 1878.
The book is available in electronic form, free of charge, at Google Books. It may be read electronically, or downloaded to your own computer. Owen, J. F. (2018). Treatise on the Construction and Manufacture of Ordnance in the British Service Prepared in the Royal Gun Factory. United States: Creative Media Partners, LLC.
But, I really prefer to read books with the feel of paper, turning real pages, leaving bookmarks, making annotations. So, I ordered a hard back copy of the book from Booktopia. It came yesterday. Cost was a bit less than $AUD50.
I received an email that my order was “being printed” and that it would be sent within 2 weeks. It did arrive about 2 weeks later, and I was surprised to see that it had been printed in Australia! The binding is neat, and the feel is substantial. 510 pages.
Having looked at the electronic version I knew that the book is full of detailed information about the design, manufacture, construction, testing, and use of British artillery of the 1870’s era. Readers of this blog will understand my interest in the subject. There are many, many diagrams, plans, tables. A real cornucopia of information for the cannon modeller, or gun nut.
Now, understand my disappointment when I opened the book at random, to read …. anything. And I blinked and squinted, and tried to make out the words…..
THE TEXT FONT IS TOO SMALL!
With my glasses on, in a good light, I can just make out the words, but it is a struggle, not pleasant at all. And, the margins are huge! 30mm on the right! In the photo you can see the original page edges. They could have made the printed page and font size substantially larger. The reproduction result is a bit fuzzy, not sharp, which compounds the problem.
Compare the electronic version with a page from the reproduced book.
Look at the dimensions in the printed version. Not at all clear. The small size, and degradation due to the reproduction process makes this book less useful.
The 143 year old book is a real treasure trove, and the information and diagrams etc may be freely reproduced without fear of copyright infringement. The reproduced paper version from Booktopia is disappointing. With a little more care it could have been wonderful. As it is I would give it a 5/10. I have sent feedback to Booktopia.
Some random pages follow, just to show more examples of the contents.
So, love the original book, disappointed with the Booktopia reproduction version. End of whinge.
The Royal Gun Factory. Originally established by Henry VIII as an artillery testing range, became the Royal Gun Factory in 1671, and became the largest cannon producing factory in the world by the time of WW1. It is located next to the Thames, in the London suburb of Woolwich, 8 miles from the centre of London, but originally it was a separate village. At its peak, in WW1 it covered 1300 acres and employed 80,000 workers. It closed in 1967.
Mainly I wanted to show you some interesting images from the era of black powder cannons.
(provided you have access to a VERY large factory, and a very skilled workforce.)
This 450 page book is available for free download at Google Books. It is so interesting, and useful to this model cannon maker that I have ordered a hard-back copy to be printed and sent to me. Not overly expensive at just under $AUD50 inc postage.
Everything that you could ever want to know about making cannons in 1879. And more.
For example, I have read descriptions of the Armstrong method of making cannons with iron bars, by forming red hot spiral coils, then pressure welding the coils into a solid mass. Then using a massive press to join the sections together. But how were the trunnions formed?
I have had this round column mill-drill for quite a few years. The head and the table are both able to be raised and lowered with a rack and pinion operated with a handle. It is a heavy unit, and raising the head or table by hand has always been a struggle, so much so lately that I have been planning to motorise the movements.
There are a few YouTube videos on the subject, but none for my particular setup. And both the head, and the table with its XY table and milling vice, are very heavy. I decided to really gear down the mechanism so the motor could be compact and not overloaded. So that meant another worm and gear in the train. I ordered a 1:40 worm and gear, but meanwhile a friend offered me one from his junk box, which I happily accepted. (thanks Stuart.)
A powerful, reversible, compact motor at a reasonable price, and not requiring complex wiring, is not readily available. But, then I thought, how about trying a reversible electric drill, with speed control? I have a Metabo 750w drill, and I decided to try that. If it worked I could buy another one on Ebay for about $AUD250. As it turned out, it is so easy to attach and detach the drill, that I will probably not need to buy another one. (note added March 11. I bought a second hand Metabo drill on Ebay for $30! It is very second hand, and battered, but has forward and reverse, 2 speed gearbox, and variable speed regulated by trigger pressure. 600 watts. Works like a charm!)
The next decision was whether to attach the motor to the head or the table. My original plan was to attach it to the head, but on testing the power required to turn the handles manually, it was obvious that the table was easier to move, so I have positioned the head at its maximum height, and will probably never need to move it again. The new mechanism was installed on the table.
The following video summarises the assembly of the components, and a brief demo. Click on the arrow to view it (10 minutes duration), or go to YouTube to see it full screen. It was shot on my iphone held vertically.
The cannon construction techniques which were pioneered by William Armstrong in the 1860’s led to more powerful and more accurate weapons. The 6.3″/160mm bore cannons which were shown in yesterday’s post, (and modelled by me,) were rapidly followed by larger cannons. The larger cannons were required to counter the iron clad steam ships which were replacing wooden warships. The colony of Victoria purchased 9″ muzzle loading black powder cannons for the defence of Melbourne, and yesterday I visited Williamstown to see 4 of them.
The 9″ rifled bore cannons fired projectiles weighing 300lbs! Cannons of this size were described according to the bore diameter, in preference to the weight of the projectile.
A fort was constructed at Williamstown (Fort Gelibrand), and 2 of the cannons are located inside a military establishment, unfortunately not accessible to the public.
I was sure that I had seen some photographs of similar guns at Williamstown which were accessible so I asked some locals, and was directed to the foreshore.
These 9″ guns are rifled (6 grooves), made in 1867, and muzzle loading blackpowder. They are very similar to the 10″ guns which were mounted on the monitor HMVS Cerberus, but these are garrison mounts whereas the Cerberus guns were rotating naval mounts.
There were only 25 Armstrong 80pd rifled muzzle loaders made, all in 1866. A special order by the Victorian colonial government to the Royal Gun Factory at Woolwich, England. Until today, I had seen and photographed 5 of them. 2 at Warrnambool, 1 at Portland, and 2 at Port Fairy. I believe that there are only 10 still in existence. Today I saw 2 more. These are in the Hopetoun Gardens, in Elsternwick, Melbourne. They are on wooden slides, and have wooden carriages. The wooden components have been repaired, extensively filled, and re-painted. Some parts are missing, including the quoins (the triangular elevating wedges).
The barrel exteriors are in good condition. The muzzles are blocked, so I could not see the bores.
I like to think that I have very few vices outside the workshop, where there are quite a few.
But, one of the vices in which I indulge occasionally, is a good Cuban. And I make a point of indulging no more than 3 per week.
And, actually, that does add to the number of vices in my workshop, because that is where most of the Cubans (and Bolivians, and other central Americans) meet their destiny.
SWMBO does not encourage cigar smoking in the house for some reason, but I quite like the stale cigar smell in the workshop. Come to think of it, maybe that’s what is keeping the tigers outside.
To cut to the story, my son in law, James, gave me the Humidor pictured above, for Christmas. A great gift, which I greatly appreciated. Mind you, I have a sneaking suspicion that he might have had an ulterior motive, because James too enjoys an odd cigar, and he likes his cigars to be at the perfect humidity of 75% when he visits the workshop, “for a chat” or whatever.
The humidor box is very nicely made, with a Spanish Cedar internal lining. Made in Indonesia. It shuts perfectly tightly and just the size for about 50 coronas. And it has a hygrometer to measure the humidity.
But…… it comes with instructions to calibrate the hygrometer. WTF! If I buy a Mitutoyo gauge, I assume that the calibration is correct. What is this “calibration”. And then there were the instructions for calibration….
place a tablespoon of salt in a plastic dish, and add JUST ENOUGH water to make it damp.
Place the dish, and the hygrometer in a zip lock sealed bag and let them stand for 6 hours.
After that time the hygrometer should read 75%
Well that all sounded Mickey Mouse to me, so I asked my fellow model engineers at our second last meeting.
As usual, in our group of 15-20 participants, one person clearly knew ALL ABOUT humidity measurements, because he had worked in the munitions experimentation industry.
Next meeting, he brought the following hygrometers……
But! Do you know which method the explosives experts used?
The salt dissolved in water method!
Apparently that method is accurate to less than +/- 0.5 %.
So that is what I did. And after the hours of waiting, when the humidor hygrometer should have read 75% it actually read 65%.
There was a screwdriver slot at the back, which enabled me to adjust the calibration on the hygrometer.
Apparently the explosives scientists carried a kit which contained a selection of the above salts, and they used them to calculate the humidity of the air before conducting their experiments.
NOT MANY MODEL CANNON POSTS LATELY!
But I have been working on finishing Armstrong RML number 2.
Not much to show but I have been working on the gears, brake, and chassis……