I have been tearing out chunks of hair, and gnashing teeth because prints are failing due to loss of adhesion. And the problem has progressively worsened to the point that the failure rate is now 100%.
And I am thoroughly fed up with throwing bird’s nest conglomerations of PLA in the bin.
I have tried the following remedies…….
Varying the bed temperatures and extruder temperatures up and down. Various combinations and permutations.
Cleaning the bed after every print, with acetone and scraping.
Checking and rechecking the bed for level.
Replacing the extruder nozzle.
Changing the PLA to brand new stock.
Printing on a different part of the bed rather than the default centre.
Today, I searched the net for solutions, and I decided that I had tried all of them, EXCEPT, replacing the bed surface.
I have been using a 3M product, designed for 3D printing, designated 9080A. Today I RTFM. If you do not know what that stands for, try “Read the F’ing Manual”. So I RTFM’d.
It seems that 9080A is good only for 10 uses, then should be replaced. OK. Penny drop time. I have been using the printer for 18 months with the same 9080A sheet. Maybe 50 times?
Back to Amazon, order some more 9080A sheets. Meanwhile I will revert to the borosilicate glass sheet that was originally supplied with the printer.
Well, 99% finished. I still intend to make sights, a base, and bumper components. But it now looks finished. A few pics.
It has a few differences from the first one of these which I finished for last Xmas. It has side platforms, handles for positioning the carriage on the slide, minor design changes in the rear wheel brackets, minor changes in the elevation wheel, and probably a few more that I cannot remember.
The explosive projectiles would never have been placed on the side platform. The noses contained impact sensitive detonators, and I doubt that the gunners would have risked them falling off.
The positioning gears work well, as does the elevating mechanism/gears, the elevation lock, the clutch and brake.
Oh yes, some fasteners for the rear platform too… And engraving text on the recoil tube cap, and the muzzle mouth. OK, 98% done.
Now, I am getting on with my next project too. Yes I will eventually finish the Armstrong RML cannon. But I am getting impatient to be doing something different, so I have started on the bronze version of the Ottoman bombard.
This PLA 3D printed breech is 230mm long, plus thread, and 107mm max. diameter. Still deciding whether to refine the design and print another. For one thing, the threaded section is constant diameter, whereas the original had a tapered thread. Yet to 3D print the barrel. It is 280mm long. That is a lot of plastic to burn out prior to bronze pouring. Maybe I should use transparent PLA in case the black dye (whatever it is) damages my burn out oven, or my lungs.
For another thing I have been unable to get my CAD program to convert the Ancient Arabic Script into vectors. But, I have been able to get V-Carve Pro to recognise them/
That is a tracing from the photograph. A couple of hours of effort doing the tracing. Then scanned the tracing, and imported the scan into V Carve. That worked, and I hope to remove 0.5mm of the muzzle bronze, leaving the raised script and stylised designs. V Carve predicts that will take 5 hours on the CNC mill!! Watch this space.
Almost finished the model Armstrong 80pr RML, and just starting another project. I have mentioned it in previous posts…. a 1:10 scale model of the 17 ton Turkish bombard, which currently resides at the Royal Armories Museum, Fort Nelson, Portsmouth, UK.
The original was in 2 pieces, to make the casting process manageable, and presumably to make transporting the monster cannon more manageable. The museum states that another reason for the screw thread join of the 2 massive parts was to separate the halves for reloading, but I can find no substantiating references for that statement. And it does not make sense to my conception of what would have been involved in the reloading process.
At 1:10 scale the model will be over 500mm long, and will presumably weigh approximately 17kg (37.5lb). Each piece will weigh 8-9kg. I will make the model in 2 pieces, for authenticity, and to make the casting more manageable, and to make the 3D printing possible. My 3D printer has a maximum model size of 300x300x400mm.
I spent several days drawing up the breech and saving it as an stl file, for the slicer (Simplify 3D) to process. The slicer predicted that the print would take 51 hours, and consume 697g (1.5lb) of PLA. I used 0.2mm layers, with 8 top, 8 bottom, and 6 side layers, and 10% fill, and since there wee some 90º overhangs, I decided to add supports.
And guess what. The print took 51 hours, and consumed most of a 1kg roll of PLA.
I chose to operate the extruder a bit hotter than normal, at 225ºc, and heated the platen to 65ºc. I wanted to make sure that this print was water tight for the moulding process, and remained adherent to the platen for the duration of the print. I accepted that the detail of the print surface would be a little coarser than could be achieved at a finer layer thickness, but the benefit would be increased water tightness.
I am still drawing up the barrel. Well, actually, it is fully drawn up, but I am refining the drawing of the Arabic script which is embossed on the muzzle. It is quite difficult to convert the squiggles and patterns to vectors, which can be used to produce the STL file for the 3D printer.
So, firstly the cheap epoxy repair/filler. I paid $AUD9.95 for 100g on Ebay.
I had dropped a tool onto my cheap compressor, and snapped off the muck metal outlet fitting. I tried cutting off the broken bit, re-tapping it, and blocking off the broken bit, but the muck metal part kept on crumbling away.
So, I filled the broken fitting with the Chinese epoxy.
It took many hours to set hard, and I left it for 24 hours before firing up the compressor. I stood well back, out of the firing line, and powered up at 100 psi. All good. So I left it for a few hours, still all good. So then I did some riveting on my model cannon….
The Chinese epoxy metal repair-filler is inexpensive and works well. Just a pity that it comes from a country whose government ignores international laws, and is territorially aggressive (Tibet, Taiwan, Tajikistan, South China Sea). And has probably lied about the origins of the Covid pandemic.
Camping on the bank of the Murray River was just sublime. Good weather, beautiful surroundings, quiet and solitude, wildlife, brilliant night skies and endless blue day skies, exploring the Hattah Kulkyne National Park and Sunset Kulkyne National Park. Swimming, campfire cooking, good wine and good company.
But all good things come to an end, and wet weather was on the way, so we packed up, and set off home. First step was to negotiate the awful entrance track. 20-30 minutes of vehicular destruction and bone shaking. Off track driving is strictly forbidden to protect the easily damaged vegetation, but boy was it tempting.
We took a longer route home, involving an overnight stay in the western Victorian town of Horsham. That was so we could be at the opening time of the Stick Shed at Murtoa. See my post “Now, This is a shed” March 20 2021. And the route was chosen to see as many wheat silos as possible. North Western Victoria varies from desert to dry country, and the dry country is mostly used to grow wheat. Tall concrete silos dot the towns and countryside, and many of them have been painted.
The paintings typically take 2-3 months to complete. Cost was not disclosed, but the increased tourism has more than justified the cost. We did wonder if upkeep of the paintings had been factored in.
Returning to model cannon next post. Riveting stuff!
During our 5 days camping on the bank of the Murray River our movements through the 48,000H hectare Hattah Kulkyne National Park were restricted for 2 days because feral goats were being culled by helicopter shooters. Movements along the River Track were permitted, and we never saw or heard the helicopter. On one of those days we drove to Hattah (population 28), then into Sunset Country – Murray Sunset National Park. We drove west, then south to The Pink Lakes, then via Underbool and Ouyen back to our camp on the river. It was a full day trip mostly along rough sandy tracks, and rough dirt tracks. It would be possible in a 2WD, and was easy in the 4WD Landcruisers. It is desert, with no fresh water, except for some tank water at a couple of camping grounds. The lakes on the map are all shallow salt pans. Any water in these is very shallow, and unusable.
Des had never driven a 4WD before, but he quickly gained confidence in the Landcruiser’s predictable handling over the rough sandy tracks, and eventually I had to slow him down. The sand was deep sometimes, but never quite requiring tyre pressure reductions. We saw no other people or vehicles in the park and the camping grounds were empty. We did see some kangaroos and emus on the east side, nearest the river, but no wild life or birds deeper in the desert park.
When our youngest daughter was old enough to be slightly responsible, our family frequently went bush camping on the banks of the Murray River, where it flows through desert country.
No facilities. Just river banks for the tents, the river to swim and fish and yabbie, cooking on campfires. We took a chemical toilet which was located behind a canvas screen. We took drinking water in 20 litre containers. In summer, occasional days were very hot, up to 44ºc. Too hot to be outdoors or in tents. We would drive about an hour and a half to Mildura to shop in air-conditioned centres, or see a movie. But mostly the weather was warm and lovely. Rain was occasional, and could be very heavy.
Often, our family group (2 or 3 families) was the only occupant of the river bank. Sometimes there would be another family group, but privacy was respected, and tents were positioned as far apart as possible. There were friendly nods when passing on the 4WD tracks, or the beach. Yes, there was a beach. At Ki bend, there was a sandy beach about one kilometer long, and 50 to 100m wide, depending on the river height.
A 4WD vehicle was desirable due to the rough access tracks, and essential after rain. The river flood plain was fine clay, and incredibly slippery when wet. Recovering bogged vehicles was a common occurrence. After a few trips I progressed to a Landcruiser with a Warn winch, compressor, snatch straps, tow straps.
The river banks were populated with River Red Gums which extended for a kilometer or 2 away from the river. The red gum dead timber made for long lasting and hot camp fires, ideal for cooking, and evening socialising. The kids quickly learned fire common sense. My youngest became obsessed with fire, and would feed sticks, and watch the fire for long periods. She is still fascinated by fire. (that is the daughter who spent a day with me melting and pouring aluminium to make cannon parts.)
The nights were dark and clear, and we always were blown away by the brilliant night skies. Sometimes I would set up a telescope, or use binoculars, to talk to the kids about stars and constellations, and the moon. We could see the International Space Station quite clearly with the telescope.
The wildlife was wonderful. Large groups of kangaroos and emus. We counted 2000 roos one day! Goannas, and an occasional snake. Wild goats and pigs were visible on the opposite river banks where there was no road access. A half hour drive away there was a ranger station at Hattah, and we would always introduce ourselves to the ranger, and chat about the park.
And the birds! They would start up at dawn, and the squawking was deafening. Sleep was impossible when they commenced. Thousands and thousands of white cockatoos, hawks, eagles, parrots, budgerigars. They would fly off in groups, and return at dusk. Large birds would skim the water and occasionally plunge for fish.
Some days we would cook, eat, swim, play bocce or cricket on the sand, read and read and talk and talk. The kids mostly entertained themselves. The water was shallow and gradual off the sandbank. But we always watched them closely. The Murray is notorious for drownings. There are many submerged dead trees, and the river is constantly flowing.
Other days we would drive through the park to spot animals. And we would have day trips into the Sunset Country. That is true desert. The only water is in salt pans. The trees are low and scrubby. There are many sand hills. Some cattle farms struggle to exist on the margins. There are some operational and some abandoned mines for mica and bentonite. And abandoned iron machinery lasts for decades in the dry environment. We always take 2 vehicles, 4WD’s, in case of breakdown, or irretrievable bogging. And containers of water and food. 4WD is essential in some places due to loose deep sand, where the going is slow, careful, and heavy.
These were wonderful family holidays. When my daughters grew into adults and left home to make their own lives, the Hattah trips stopped, but they often reminisced about camping at Hattah. Lately they have been talking about taking their own children, my grandchildren, camping on the banks of the Murray at Hattah.
Then recently, my brother in law and his wife asked me if I wanted to join them on a nostalgic trip back to Hattah. I immediately agreed, and invited another friend to join us. My wife used to love the camping trips, but her arthritis limits her mobility, and sleeping on the ground is not an option for her. Even an offer to hire an off road camper was not acceptable. So I asked a friend who had never been bush camping, and had never done any off road driving. I was somewhat surprised when he immediately agreed. We are all into our 70’s. My vehicle is still an 80 series Landcruiser, 27 years old. But it is in good mechanical condition. Bull bar, Warn winch, heavy duty springs, compressor, dual batteries, driving lights, and I still have lots of recovery gear. I also still have a “minute” tent, small fridge, cooking gear, etc etc. It was all stored away in case such an occasion would arise. I also packed my anti snoring CPP device, medications, a first aid kit. And I bought a modern innovation, a solar blanket, for recharging the vehicle batteries, to keep the fridge, and my snoring device working. The fridge was for beer, meltables and vegetables. I am now vegetarian, so keeping meat chilled was not an issue.
I also purchased a pair of hand held small walkie-talkies, for communication between the two vehicles. We would be well out of mobile telephone range a lot of the time. In the old days we had vehicle mounted 2 way radios, but mice had got into mine and it was kaput. I was pleasantly surprised how inexpensive the solar blanket and walkie talkies were.
Spent a day gathering gear, and doing some repairs to vehicle and tent. Another half day packing the Landcruiser.
Then we were driving towards Hattah. Met the other vehicle at Gisborne. Crossed the Great Dividing Range, then the flat dry plains of north western Victoria. About 6 hours of highway driving, with a stop for lunch, then past the olive groves, and almond orchards of the irrigation country as we neared the Murray River. Finally we passed Manangatang and Annuello, then onto the dirt track for the final kilometers in the Hattah Kulkine National Park to the Ki Bend.
That track is always rough and bone shaking. But, with almost no use in 2020, and no maintenance, it was horrendous. I have driven the Palm Valley track, the Birdsville track, and other parts of central Australia, in the 1980’s and 90’s, and driven some rough tracks in the Otways before they were all closed, but for vehicle and human bone shaking, this was the worst that I had ever encountered. Deep corrugations which were impossible to avoid. And no speed change was of any help. After about 20-30 minutes of being shaken to bits we arrived at the Ki Bend. The river looked SO inviting. The sand bank was exposed. The river was about medium height. It looked as wonderful as I remembered. And, there was no-one else anywhere to be seen. No other camps. No vehicles. No boats. Deserted.
However there was a problem.
The camping sites were basically areas cleared of bushes and grasses, and not directly underneath river red gum trees, which are notorious for suddenly and randomly shedding huge heavy branches, killing or maiming anyone silly enough to be underneath. But, the sites were choked with tree saplings up to 3 meters high. We guessed that they had grown in 2020, in the absence of campers.
We could have removed the saplings, just enough to put up our small tents, but somehow, it did not seem the right thing to do. The other option was to camp on the sand bar. And that is what we eventually did. Small biting insects on the sand bar did not prove to be a problem. We were well away from potential dropping red gum branches. We could drive our vehicles on the firm sand near the river bank. And there was plenty of dry dead wood for the fire. We figured that if the river did start rising due to water release further upstream, we would have time to pack up and move to higher ground.
So, we put up our tents, including the toilet tent, dug a pit in the firm sand for the fire, gathered some wood and lit the fire, unfolded our chairs, and had some beer. By this time, dusk was approaching, the birds started squawking and settling into the trees, turning them white.
This list is more for my own amusement than expecting much reader interest. It is a list of the materials which I have used in making the model Armstrong RML’s.
Mild steel (most of the structural components, barrel 2)
Stainless steel (barrel 1, wheels, and metric fasteners)
Tool steel (rifling cutters)
Bronze – LG2 (ingots for casting many small components, bar stock for machining small components where possible)
Brass (some small components)
Copper (rivets, gas checks)
Aluminium (ingots for casting wheel brackets, bar stock for CNC jigs)
Jarrah (floor board offcuts for platforms)
gas struts (adapted for use as the recoil mechanism)*
And the processes…this was prompted by a question from my daughter.
Photography (still, video, drone)
Linear and angular measurement of the original cannons
3D printing (new skill for this project)
CAD design 2D and 3D
Discussions via web site, email, telephone, face to face with historians, cannon enthusiasts, black powder enthusiasts, model engineers, mechanical engineers, computer experts, CAD experts, museum curators
Conventional machining with mill, lathe, drill press, hand tools
CNC machining with mill, lathe, rotary table (new skill for this project), using Mach3, Vectric V-Carve Pro.
Gear design and cutting (using Gearotic software-new skill)
Casting aluminium, bronze (new skill for this project)
Having mild steel and tool steel parts laser cut professionally
Designing engraving of symbols, alpha numerics, lines, labels etc. and completion of these with a fibre laser by Stuart T.
Purchasing parts from suppliers during Covid restrictions, mostly by telephone and online
Making tools, particularly a tool to cut rifling grooves. Quite proud of that one.
Metal filling (JB Weld), gluing (Loctite, Super Glue), finishing, polishing, painting, lacquering.
Keeping detailed records in notebooks, photographs, videos.
Completing this blog, answering correspondents. This has been a very rewarding aspect for me. I have had lots of advice, all of which was appreciated, and some which was used and acknowledged. When I aired doubts about difficult or dubious decisions I particularly valued the feedback and encouragement from my readers.
I have made many mistakes. Some required making new components. Some required honing skills (like riveting). Some were camouflaged. Some were just accepted and ignored and eventually forgotten.
The models were a significant cost. The biggest item was the metal casting equipment, which I can use on future projects, and probably sell one day, so I will exclude that from calculations. Same goes for the 3D printer. I did not keep actuarial records of costs. I used several bags of metal casting investment medium at $110/bag. Bronze and aluminium ingots were also several hundred $$ but I have quite a bit left over. BA fasteners were ~$200. Metric fasteners were inexpensive, from China. Laser cutting was cheap $~60. Most of the metals for machining were from my workshop stock, so not included. I have spent about 15 months making the 2 model cannons. The power bills for my workshop are about $250 per 3 months, so that cost component is significant.
The biggest cost was the time taken. I roughly estimate 25 hours per week (conservatively, could be much higher), over 60 weeks. Say 1500 hours for the 2 model cannons. (not including finishing number 2. Probably another 50-100 hours). So, maybe 800 hours per cannon, not including research time, trips to Port Fairy/Warnambool/Portland/Queenscliff, etc).
Hmmm. Maybe I should not have done that rough cost estimate.
Not sure if I will publish this one.
*Using gas struts was a controversial decision. The commercially available gas strut was 0.5mm bigger diameter than specified (18mm instead of 17.5mm), exactly the correct length after a bit of machining, although the piston rod required lengthening by 30mm, the right colour, and too stiff so I released the compressed gas. Some of my model engineering colleagues were a bit sniffy about it, but it fitted the bill closely enough for my liking so I used it. No regrets. I also buy fasteners where possible. I rarely make nuts and bolts although I often modify commercial ones. I use metric fasteners where possible, although there are a lot of BA8’s and some BA 10’s in the cannons. I broke x3 BA8 taps but all were able to be removed.
A few year years ago I made a model triple expansion steam engine with plans and castings supplied by EJ Winter P/L of Sydney. The details of the build were detailed on this blog. I found it to be a difficult build, but eventually got it running on steam, as shown in the following video…
Today I rang Ben deGabriel, the owner of EJ Winter P/L, the supplier of the plans and castings of the engine, to order some 10BA nuts and screws for my model Armstrong RML cannon. It is always a pleasure to chat with Ben. He is so passionate about model engineering, and a very knowledgable and reliable supplier. The chat turned to the triple, and he told me that he had found references on the original model engine plans, to SS Kuttabul, the engine of which was the basis for the model engine.
After the outbreak of WW2, the Kuttabul was requisitioned by the Royal Australian Navy, and was moored at Garden Island in Sydney Harbour, and used as accomodation for naval personnel pending transfer to their ships.
Three Ko-hyotkei class Japanese midget submarines entered Sydney Harbour 31 May 1942, with the intention of sinking Allied warships. M-24 fired 2 torpedoes at USS Chicago, a heavy cruiser, but both missed. One torpedo ran aground harmlessly, but the other hit the breakwater against which HMAS Kuttabul, and a Dutch submarine were moored. An alternative conclusion is that shells from the USS Chicago which were mistakenly aimed at the Dutch submarine, hit the Kuttabul. In either case, the Kuttabul broke in two and sank, killing 21 sailors, and wounding another 10.
The engine of the SS and HMAS Kuttabul, was a 113hp triple expansion steam engine.
This history, whatever the exact cause of the sinking, makes me particularly glad that I modelled this particular steam engine.
If I find more information about the Kuttabul or her engines I will add to this post.
When the cannon was fired the recoil pushed the carriage up the 4º slope of the chassis. However, to reload the muzzle loading cannon, the carriage had to be completely at the top of the slope. I know this, from making the model. There is only one position of the carriage on the chassis where the loading arm will properly engage with the muzzle of the barrel.
So, if the recoil did not push the carriage up to exactly the correct position, it had to be wound up to correct position by 2 of the gun crew, operating a handle or wheel on each side of the chassis.
On the first model which I made of the cannon, I copied the wheels which were present on the original cannons at Warrnambool.
Of the seven 80pr Armstrong cannons which I have been able to examine, the Warrnambool pair are the only ones with existing winding back wheels or handles. So that is what I made for the first model which I made, and what I had planned and made for the 2nd model.
But, I was always a bit dubious about the large, and rather unwieldy wheels. Would the original Armstrong designers have specified such wheels? Then one of my readers independently questioned the wheels, so I delved more deeply.
The 80pr cannon is essentially a copy of the 64 pr Armstrong cannons, the main difference being in the construction of the barrel. The 80pr barrels used the new method of winding white hot strips of iron around a mandrel, which made them able to accept larger charges of gunpowder, and heavier projectiles.
I could not find any plans or diagrams of the 80pr cannons, but I did find these drawings of the 64 pr’s on a very similar iron chassis….
So, I have made handles for my 2nd model…..
Then, the instruction manual for the 80pr, which I saw for the first time a month or so ago, specifies that after winding back, the HANDLES are laid under the chassis. Not the WHEELS, but the HANDLES.
So, I rest my case. Crank handles it is, unless some other convincing evidence comes to hand.
P.S. Casting the Chess Men. I am still feeling a bit despondent about that last failure. I have some ideas about better techniques, but I am not moved to try again. At least at present. For one thing, the failed pieces are really quite heavy, and I wonder whether even if successfully made, they would feel good to use. So I am moving back to finish the cannon, and will wait see if there is some inspiration to redo the chess men. Also, I am still fixing the CNC lathe with the dead computer. Have changed the interface to a smooth stepper, and laptop, but there are still some issues. Stuart T installed the smooth stepper, and reconfigured Mach 3, but the smooth stepper would not work. So Stuart used another identical smooth stepper board, and that works. Stuart is still trying to figure out whether I bought a dud smooth stepper board.
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.