I originally examined the Armstrong 80pd RML cannons at Port Fairy a year ago. Then spent 2020 making a 1:10 scale model. Now, I am completing a second model. Here is a photo of the current status of the 2nd model. And no. There will not be a third.
But this post is about my recent 2021 holiday in Port Fairy.
I spent some hours checking and getting more measurements……….
My son in law brought his drone to Port Fairy. It is a Mavic 2 Pro with a Hasselbad camera. I was sooo jealous.
And here is his footage of Battery Point. If you look carefully you can see me, my daughter, and Steve controlling the drone. This was a day after the photos above were taken, and my grand daughter was not in the video. Click on the arrow to see the 2″ video.
My current project is finishing the second Armstrong 80pd RML model cannon. I expect that will keep me occupied for a couple of months. But I probably wont post the steps, because it will be very similar to the posts from last year.
Yesterday, my GSMEE friend Swen Pettig asked if he could use my ring roller. The following video is a 7 minute rambling chat while he was finishing the job.
I made the ring roller quite a few years ago. It is slow, but quite controllable, and does a nice job. The 1/2 hp motor is geared down, 1:40. I have rolled steel up to 100mm wide and 10mm thick.
As you will see, Swen is making a scale model approx 1:4, of the first internal combustion car by Karl Benz.
Here, he is rolling the wheel rims from 10×10 mild steel square section rod 1.5m lengths. He made 2 front and 2 rear wheels. (needed only one front…. the car is a 3 wheeler).
Sorry about the absent chain guard. Just an oversight. I warned Swen about the possibility of inadvertent circumcision.
10 members of my family had a brief vacation in South West Victoria after Christmas. It was a nice holiday, but with three 5 year olds and an 8 year old, it was noisy.
I took the opportunity to revisit the Armstrong RML’s at Port Fairy and Warrnambool. And to visit the one at Portland for the first time.
Every time I see these cannons I learn something new about them. And I got to talk to a local historian at Port Fairy. Colonial Victoria purchased 25 or 26 of these muzzle loading rifled cannons in 1866. 10 of them are still in existence. I have now seen 5 of them. I believe that there are further barrels at Fort Queenscliff, Point Nepean, and possibly Cerberus which I have not yet seen.
“80pr” indicates that the cannons fired projectiles weighing 80 pounds. On all of these cannons the case of the elevating gears is stamped thus….
I am not sure what M2 GAR. stands for. Could it be an abbreviation of Mr WG Armstrong (later Lord Armstrong), the designer of these guns? (note 27 Jan 21. I spoke at length with Australian cannon expert Peter Webster. He said that GAR stands for “Garrison”. Not sure why, but maybe to distinguish it from naval guns.) R.M.L. will stand for “Rifled Muzzle Loader”. 80 PR will be 80 pound projectile. 6 FT PAR had me puzzled, but when I saw that the guns were designed to sit behind a 6 foot parapet I am pretty sure that will be the solution. And in a smaller font below, WD with a vertical arrow will indicate that the part has been approved by the War Department.
The Portland 80pr RML
From a distance, it looks good. The shapes in the carriage and chassis stand out with the white paint, and the assembly looks reasonably complete, except for absent winding handles and sights. Closer inspection however is disappointing. The cannon was restored in 1985 and the parts which were replaced such as the biggest gear, the elevation quadrant scale and trunnion caps, and elevation gear are significantly different from the originals on the Port Fairy and Warrnambool cannons. They appear to have been cut from mild steel in a fanciful representation of the original designs. Arc welding has been extensively used to join components. It is OK as a tourist attraction, but useless for historic study.
And instead of pointing over Portland Bay, it points at the large grain silo.
PORT FAIRY CANNONS REVISITED
Overdue for restoration works, the carriage wheels are largely crumbling into rust, and the girders have large rusted missing sections. The barrel of number 22 is elevated to a high angle which would never have been used, but is useful for firing blank charges for the entertainment of tourists, and which I enjoyed 12 months ago. Number 17 barrel rests on its parapet, at such a low angle that it too would never have used. The total lack of restoration does allow one aspect of the barrels to be visible, and that is the coil construction of the barrel segments.
I measured the widths of the strips, and found that those on the narrowest part of the barrel (the chase, near the muzzle) were the narrowest at 36mm, and those of the biggest barrel diameter, the breech, were 50mm wide.
I was also able to work out the structure of the girders on the Armstrong RML, and the reason for all of those rivets. The top and bottom pieces are T section iron, and the sides are 3/8″ (9.5mm) plate iron. There are small pieces of iron to fill the gaps at the ends, and where intermediate rivets are used in the middle sections. Using a percussion technique, taught to all medical students for diagnosing pneumonia, I could work out the locations of all of the small middle pieces.
WARRNAMBOOL ARMSTRONG RML’s
These have been expertly restored, and are the most complete examples which I have seen. They were painted entirely black which makes photographs more difficult to interpret.
Whales are commonly seen in the bay. Unfortunately none on this day.
Next post will include some interesting historical photos, and other restored cannons which were recently installed at Port Fairy.
Christmas 2020 seemed to hold particular significance. Our children, their families, grandchildren all congregated and had a superb vegetarian meal with food preparation shared. Vegetarian, because a majority of our extended family are now vegetarian. One is a vegan, and some of us are inching our way towards that aim. Even the omnivores are mostly reducing their meat intake.
We enjoyed some lovely Australian wines, with Pavarotti in the background.
This was the first time that the whole family has been together for 9 months.
The grandchildren had been forbidden to get up for presents before 6am. And my son in law set their clock back an hour! So it was a leisurely start to the day. 7am.
We usually do a Kris Kringle for adult presents, but this year, we just decided to have no restrictions.
I had wondered (and to be honest, been slightly anxious) how the model Armstrong RML cannon would be received by my son in law (front) and youngest daughter (right front). Neither of them have any interest in weaponry or military history. My son in law grew up in Port Fairy where the original full size cannons are slowly rusting away. And my daughter took part in 2 casting sessions to see what casting was about. But neither had any idea that the model cannon was for them, and apart from the aluminium casting, neither had seen the cannon gradually being made.
Their reaction exceeded my most hopeful expectations. Both became teary, as did I.
The following video was made by my daughter. The daggy paper hats are part of our celebration. Totally unscripted. And I have had a few by this stage of the day.
I bought this 100 year old French vase for SWMBO for Xmas. I had no idea what its value was, but just loved the decorations, colours and shiny surface. It is quite small, and would hold only one flower if used as a specimen vase.
It had no base. Was open at both ends. And had been slightly damaged from being top heavy and falling over for the previous owner on several occasions.
The damage had been professionally repaired. As you can see from the photos, the vase is quite exquisite.
The antique dealer, with whom I have dealt on many occasions, has had a tough few years. Antiques of all types had really become unfashionable. I asked how things had been in 2020, and was very surprised to hear… “Business is booming. Never been busier. Despite viewing by appointment only for most of 2020.” Which I was very happy to hear, because Moorabool Antiques, in Ryrie St Geelong, is one shop that I always enjoy browsing, and chatting to the very knowledgable staff.
Since the vase had no base, he said that it was much cheaper than if complete. It was still quite costly, but I am pretty sure that SWMBO will like it.
And……I am pretty sure that a half competent machinist could make a base for it. Paul, the Moorabool Antiques proprietor was interested. I showed him a photo of my model Armstrong cannon, and he became VERY interested. We discussed designs and materials for the base, and methods of attachment. It would have to be water tight if it will be used as a specimen vase. The attachment method would have to not affect the existing structure or decorations. I mentioned Super Glue. Paul suggested Silicone. So Silicone it will be.
I searched Google Images for similar vases, and discovered at least a dozen designs by the same artist, Alexandre Marty. It is Limoges enamel over silver foil on copper. And as you can see from the photo of the similar example with a base, the missing base was probably gilded brass or copper or bronze.
I searched my workshop for bronze/brass/copper of sufficient size, and found some copper, LG2 bronze, aluminium bronze and brass. After looking up the properties of the materials which I had to hand, I chose the aluminium bronze. As the name suggests, al-br is mainly copper, with aluminium being the second constituent. It is particularly resistant to corrosion so is commonly used in marine applications, such as propellors.
Can you see the gold coloured rebate? That colour developed when the workpiece became hot during machining. That gold colour is a property of al-br, and is often used by jewellers. I slowed the feed-rate to avoid further heating, and got the contrast from the other bronze coloured surfaces. It will be interesting to see what happens to the colours with time. Although the vase base diameter has increased only by 10mm, it is much heavier, and should resist toppling.
So, the first model Armstrong 80lb RML is finished. Final photographs following. I admit that some artistic license has been taken, as directed by SWMBO, and some scale details have been modified slightly in order that it is finished in time for Xmas.
Yesterday I fished out the components of the other model cannon, the “A” version, which I am making for myself, and which will be used in model engineering exhibitions. I predict that it will take another 2-3 months to complete. I am intending that it will be more rigorously an authentic scale model, and probably less pretty and decorative than the version pictured below. But it will look interesting alongside the 24lb long gun of the Nelson era, the 32lb carronade, and the huge Ottoman 1465 bombard, all to 1:10 scale.
Here are the final photographs of the “artistic” B version.
When I make the sights for my “A” model, I will also make some for this one.
There is a name plate which was lasered by my colleague Stuart Tankard but that reveals a bit too much information to show here. Suffice to say, it names the cannon, a few basics specs, maker’s name, and year. It will be fastened to the wooden base. It also states “NEVER FIRED IN ANGER”.
Thankyou to all of my readers, many who have supplied useful advice and welcome encouragement. Particular thanks to Stuart Tankard for his lasering expertise and machine, and other technical advice. And thanks to SWMBO, who has warmed to this project as it approached completion, despite having absolutely no interest in weapons of destruction. She does have a good eye for form and colour. And mostly for putting up with my foul moods when things went wrong.
Now. It will be interesting to see if the recipients of this model actually like it.
I have machined a wooden base and I will fasten the central column of the cannon chassis to the base. The reason is that people cannot resist swivelling the cannon around on its column and the the wheels tend to mark/scratch polished surfaces. Better to mark a wooden base than a polished mantelpiece. But how to finish the surface of the base? Any polish/paint will quickly develop marks from the wheels. I have decided against making steel railway lines for this model.
I have used an Australian hardwood (mountain ash, a very hard dense wood, reclaimed from a demolished building). I am thinking that I will just oil it. The colour of the wood will darken with age, but will never be as dark as the table, which I made decades ago from Australian Iron Wood. (note, not iron bark. Iron wood. The hardest, densest wood I have ever used. And yes, I have worked with lignum vitae, and Australian red gum. The marks in the surface of the table are only in the polish. The wood is almost impossible to scratch. My kids used to dance on this table 30 years ago.)
The burn mark on the end of the base is from the belt sander. I will remove it with hand sanding before oiling.
The machined finger grips on the ends were made on my vertical mill with a steel moulding cutter intended for metal machining. It worked well.
I discussed the finish which I wanted to achieve with my resident finishes expert. SWMBO. I wanted a slightly darker, low sheen finish, which would not get scraped off with the cannon wheels.
She recommended this stuff. It is a stained, penetrating oil. Smells very chemically.
It is actually a surface repairer, rather than an overall finish but I did what I was told.
OK. That looks good. The surface will be easy to touch up if required.
1:10 Model Armstrong rifled muzzle loading 80lb cannon WILL be ready for Xmas.
Apart from minor touch-ups, the model and painting is completed.
I will take some careful photos before it goes to its final home, but here are a few snaps to show how it appears with some paint and lacquer.
So, was SWMBO correct about not painting the chassis? I like the look of this finish scheme, but now have to decide what to do in that regard with the “A” model, which was put aside while I finished this one.
p.s. I weighed the model, because I was curious. The full size original barrel weighed 81.5cwt/4.1 tons plus the carriage/chassis, about 5 tons/5080kg total. The 1:10 scale model should weigh 0.1 x 0.1 x 0.1 or 1/1000th of that which would be 5kg/11lbs. It actually weighs a tad under 10kg/22lbs which is almost exactly double the predicted. It is a bit of a lump to carry around and I do NOT know where the extra weight came from. Or maybe my mathematical assumptions are incorrect.
(note added 1 March 2021. See the post added 1 March 2021. The total weight of the gun barrel, carriage, and slide – which I have been calling the chassis, was close to 10 tons! So my assumption that the model should weigh 1/1000th of the original was very close to correct!)
The accuracy of cannons was dramatically improved in the 19th century with several developments.
The bore was machined rather than just cast, as result of the invention by Wilkinson of a powered boring machine. Incidentally, this process was also adopted by Trevithick in making steam engine cylinders, significantly improving the efficiency of steam engines.
The adoption of sights, calibrated for distance, and movement of the target, instead of just eye balling along the barrel.
Changing from round iron balls to cylindrical projectiles, with a pointy front and slightly rounded rear.
Rifling the barrel bore, causing the projectile to rotate.
Standardising the weight and granularity of the blackpowder, making shots more repeatable.
Increasing the power of gunpowder by increasing the size of the “corns” which sped up the rate of combustion. This permitted flatter, more accurate trajectories.
Improvements and calibration of degrees of barrel angulation.
Increased research and knowledge of the science of ballistics.
Increased training and professionalisation of gun crews.
The Armstrong 80lb rifled muzzle loader had a projectile which weighed, you guessed it, 80lb (36kg). A bit later cannons were categorised by the weight of the barrel. e.g., the 80lb Armstrong would have been named a 4 ton cannon. The gunpowder was standardised at 20lb per firing. The gunpowder filled silk bag, then the 80lb projectile were manually lifted onto the loader cradle, then ram rodded into position. Later, bigger cannons, needed a small crane to do the lifting, but in 1866, the 25 Armstrong 80lb cannons which were made specially for Victoria and South Australia, and were the most advanced cannons made at that time, required strong gunners to do the lifting and ramming.
My model Armstrong cannon is basically a display, rather than a working (firing) model. So, for the display, I have made some projectiles, and fake gunpowder bags. I was fortunate to find some old diagrams of both.
As you can see, for an 80lb RML cannon, the projectile is 15″ / 380mm long, and just under 6.3″ diameter. The barrel bore is 6.3″ diameter, and to cope with heat expansion the projectile must have some “windage” (a gap) to avoid jamming. The 1866 projectile has a pointy end, and a rounded rear, which is relatively aerodynamic, and similar to the form used in many modern guns.
Attached to the rear of the projectile is a (dark shaded) copper disk, which expands into the rifling grooves after firing, and further reduces the windage, and causes the projectile to rotate. The copper disk separates from the projectile after they leave the barrel, and it falls to earth. The best examples of the copper “gas checks” have been retrieved from the sea, in front of shore batteries where these cannons were located.
Before gas checks were introduced, the projectiles had copper studs attached to their exterior. The studs fitted into the rifling grooves. The studs were effective at causing the projectile to spin, but they caused rapid wear of the cannon barrel, excessive drag and lower muzzle velocity of the projectile, and were slower to load. The 25 Victorian Armstrong 80lb RML cannons were designed so that studded projectiles could NOT be used. (n.b. note added 7 Jan 2021… that last sentence is incorrect. The 80lb RML’s would have used studded projectiles until mid 1880’s, and then changed to gas check projectiles. instructions were issued then that studded projectiles should not be used.)
The following drawing shows a silk bag, containing the gunpowder. It also shows the central wooden rod which prevented the bag from bursting during ramming. This powder charge is for a 10″ RML, so it is bigger and heavier than the one for the Armstrong 6.3″ RML, but the design is essentially the same.
After loading and aiming, the gunner would perforate the silk bag with a long spike, then insert a quill or later a copper tube, full of fine gunpowder which extended through the vent from the touch hole to the perforated silk bag. Royal Gun Factory experiments showed that the best firings occurred if the silk bag was perforated about half way along the cylindrical bag, so the vent and touch hole were located at that point.
The method of igniting the gunpowder will be described in a future post.
Today is the 40th successive day that Victoria has had NO new covid cases. It seems worth the prolongued horrendous lockdowns experienced earlier this year. Full marks to our public health officials, health workers in hospitals, and politicians. (yes, even the politicians. They had a steep learning curve, and made mistakes, but I believe that they tried very hard to make correct decisions.)
The result is that we had our first face to face GSMEE meeting since January. And with Christmas just a couple of weeks away, it was our annual Xmas BBQ. I hasten to add that the vegetarians in our group were well catered, as well as the omnivores.
There were 5 entries in the club competition for making a small engine, and it was convincingly won by Neil McMeekin. Neil’s engine was beautifully finished and it ran smoothly without any mechanical noises. Frank Mullins 2 entries both ran well, and he was awarded the second prize.
The “models on the table” included my still not finished scale model Armstrong cannon. It is now painted, and clear lacquered.
In the foreground is Stuart Tankard’s model of an Otto D2 gas engine, originally made in 1895. As usual with Stuart’s work it is perfection in motion. Not quite finished, but when it is, I will post a more detailed description and photos.
To the right of that is a bronze cannon cypher off an Ottoman cannon which was captured in Mesopotamia in WW1. The wooden mounting plaque is from a British Spitfire propellor. Owned by Laurie Braybrook, at 95 our most senior member, and raconteur extraordinaire. Laurie fought in WW2 in the Pacific islands, and he has many wonderful stories.
Behind Stuart’s Otto is a Bolton 7 horizontal mill engine, made by Neil Ellis. Again, not quite finished, but it is displaying an incredibly high standard of machining and finish. This is Neil’s FIRST model engine. Again, I will feature it in a future post with more details. Neil comes from a boatbuilding occupation, so he is no stranger to precision and machining, but this level of model engineering in a metal working beginner is amazing.
Then my cannon, which is probably suffering from some overexposure in this blog, so I will add just one more photo, since it has now been painted and laquered.
At the rear are Swen Pettig’s “Minnie” 1″ traction engine which is looking great, and his therapeutic Grasshopper Beam engine. I say “therapeutic”, because the Grasshopper is Swen’s escape from working on the Minnie. His size 13 hands have been a serious handicap to assembling the Minnie, and I gather that there has been much stress and frustration. (But he is talking about making a triple expansion engine like mine, so he is clearly a glutton for punishment. The barring slots in the flywheel of the grasshopper are an interesting feature, and I hope to get post from talking to Swen about those.
I think that everyone was excited and delighted to be face to face again, and looking forward to normal GSMEE meetings in 2021. Zooming has been a good “stop gap” but I think we are all ready to resume normality. Hopefully with no further lock downs.
First, I have decided to NOT rivet the final joins of the chassis. Instead I am using dome head stainless steel bolts and nuts. The main reason is that the other end of the rivets are in impossibly small (for me) cavities and spaces, and I could predict that the final riveting result would be horrible. Even using threaded rivets would be incredibly difficult. This decision does cause me to reflect on the 1866 cannon builders who managed such perfect results with red hot rivets in confined spaces, and again, to be awed.
To divert, back to the painting.
Question. When painting a model, is it best to assemble the whole model then paint, or to completely disassemble every part, paint the parts then reassemble?
1. Disassemble and paint the parts then reassemble. This results in complete paint coverage of all parts. It results in clean separation of different coloured parts. Mistakes involve limited areas and are easier to correct. However, the thickness of the paint can alter carefully machined tolerances. And surfaces can be painted which were intended to be unpainted.
2. Assemble the entire model, then paint. This can make some recesses, corners and hidden areas difficult to access. But the appearance of the entire model can be assessed as the painting progresses, and major mistakes in colour choice can be corrected. The painting process does not alter dimensions or fitting together of components. But paint edges and joins can be difficult to keep neat and straight, particularly in my inexpert hands.
3. (Obviously what I chose to do). Partial assembly, into modules, then paint the modules separately. This has the advantages of both 1 and 2. The modules can be stacked together to periodically assess the results. The modules are smaller than the complete model, and easier to handle. Difficult decisions regarding colour, or whether to paint at all, can be deferred until the easier parts are painted, and some idea of appearance ascertained progressively.
So that is what I am doing. I have painted the bottom part of the chassis, and the carriage. Etch primer at this time, but already firming up ideas about final colour. And my colour and design expert advisor (SWMBO) has had some input into this decision.
At this stage, I asked for advice from SWMBO. She has suggested that the primed modules should be painted satin black, which should contrast nicely with the brass/bronze components. Avoiding gloss will minimise the finishing defects. Some filling of defects will be required in any case. The black colour will be tested on the carriage, and if it looks OK, the chassis subframe will receive the same colour.
SWMBO’s most interesting suggestion is to NOT paint the main chassis beams at all! Well, a clear lacquer will be required to prevent rust.
But. What about disguising the copper rivets/stainless bolts?
SWMBO: “they look interesting. Leave them.”
Me: “but, but, but, they do not look authentic.”
SWMBO: “This has to look like a work of art, otherwise it will be just a boring dust gatherer.”
After my crap riveting of the carriage, I could have ripped them all out and started again. Or, I could slap on a coat of paint, and take another look.
Well, that’s what I did.
Well, actually, before that I telephoned my riveting expert about my rivet problems, and he gave me some further advice……
Put a G cramp on the compressor hose to restrict the air flow
Polish the ends of the snaps, and round the edges slightly
Check that the shape of the snaps mirrors the shape of the rivet heads. It didn’t. I had thought that the dome rivets had hemispherical heads, but on closer inspection, they were flatter than a hemisphere. So I made some new snaps, and took great care to make sure that the rivet heads fitted more precisely into them.
Be more careful to keep the snaps perpendicular to the surface.
I did replace the worst rivets, and I was much happier with the results.
Then some paint. But first I gave the carriage a thorough wash in detergent to remove any trace of machining oil.
Then, using a pressurised can of etch primer, used my spray booth (a cardboard carton open at one side) to give it a coat.
And, with a bit of paint, the carriage doesn’t look half bad?
Of course, some areas showed up as needing some filler…..
I quite like that colour. Maybe with just a touch more blue in it.
I am no expert at riveting, but I have had some good advice from an expert. He has had years of experience in the aircraft industry. Prior to this cannon project I would have inserted fewer than a dozen rivets. You cannot beat experience. And knowledge.
As you look at these photos, and grimace, bear my inexperience in mind. Actually, my results improved as the day wore on.
I learned a few lessons as a result of this session of riveting.
Riveting is a manual and knowledge based skill, which must be studied and practiced.
Items which are riveted change their dimensions. Components which fitted perfectly when machined and bolted together develop gaps and warps after riveting. Not surprising, considering the hammering of relatively unsupported pieces.
The tools must be perfectly designed for the job. The snaps must be the correct shape and size for the rivets.
Rivets from different manufacturers differ in dimensions, even when supposedly the same.
Soft components like aluminium can deform and break when riveted.
Retired gynaecologists should not rivet. Stick to nuts and bolts.
I am hoping that the bruises and cracks and deformations which I have caused with the riveting will be camouflaged by the paint job.
Surprisingly, the carriage still sits flat on a surface plate. And the barrel sits squarely in the trunnions.
I have commenced the teardown of the model Armstrong cannon. But first I took some photographs, just in case the paint job is not the best. To explain, I do not have a great history of good paint jobs. SWMBO bans me from painting around the house (that is NOT a loss, believe me) because of runs, brush hairs in the paint, paint applied too thickly etc etc.
So here are the photos….taken with my iphone. Just to reiterate, this model cannon cannot be fired. It has no touch hole/vent.
After the teardown I will complete the insertion of rivets, replacing many of the 8BA screws with rivets.
The firing rate for these 80lb cannons, with a trained crew, was about 1 round every 1.5 minutes.
So, wish me happy painting. Still haven’t finally decided on colours. But probably black for the interiors, silver for wheel assemblies, wheels barrel gears and brass components unpainted. Maybe a light grey-blue for the exterior of the carriage and the chassis.
Then I fitted the bracket which restrains the movements of the elevation gear lock-release…
So those are the last major parts to be fitted to the cannon. Oops. I forgot. I need to make the aiming sights, and bore the holes in the barrel to hold them. None of the cannons which I have inspected have exisiting sights, presumably stolen-souvenired, but some 19th century publications have good diagrams which I will be able use to make scaled versions.
I will add a rear wooden platform, and the eye bolts.
Then a complete teardown, painting some parts, polishing others.
The investment plaster is is what the mold is made from when parts are cast in bronze and aluminium.
It is incredibly fine dust until mixed with water, and these need to be in precisely measured weights.
The mixture is poured into the casting cylinder in which the parts are attached to a wax or PLA “tree”. (see yesterday’s post for a photo of a tree).
After casting, much of the investment plaster is blown out of the cylinder when the still hot cylinder and its contents are plunged into cold water. The steam which forms acts like a steam cleaner.
But the parts are still covered with a tenacious layer of investment plaster. More can be scraped off with a screwdriver, wire brush, pressure hose etc. etc. but there remains a lot of plaster in the nooks and crannies, joins and holes.
And it is a fair pain to get it all out.
Yesterday’s castings looked like this after I had sawed the 34 pieces off the trees.
and after more sawing and use of a thin disk abrasive wheel…
Then most of the unwanted bronze branches were machined and sanded off…
It happened serendipitously. I placed the parts in a gemstone tumbler with sharp stainless steel shot, to take off the sharp edges. And hallelujah! The remnants of the investment powder were also removed. The curved arms in the photo are stainless steel and brass, bent around a mandrel. I have not yet decided which to use.
In future I will use the gemstone tumbler at an earlier stage, to get rid of the investment as soon as possible.
And here is another stage of the pruning of the trees…..