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. I read every comment and respond to most.

Assembly Modules

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.

As you can see, the bolt heads are same shape and size as the 2mm copper rivets. My intention was to paint the rivets and the bolts (after filling the hex holes) and then they would be virtually indistinguishable. However, that plan was blown out of the water by SWMBO. (read on).
The copper rivets and stainless bolts. Not kosher. But interesting?

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.

These are the main modules, 4 of them. The barrel assembly is stainless steel and it will not be painted. At the rear are the carriage and bottom part of the chassis, which have been primed. The main chassis beams containing the movement gears are unpainted. The carriage looks naked without its bling.

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.”

She wins.

Painting Covers a Multitude of Sins

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……

  1. Put a G cramp on the compressor hose to restrict the air flow
  2. Polish the ends of the snaps, and round the edges slightly
  3. 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.
  4. 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.

I quite like that colour. The blue splog is some marking paint. The etch primer refused to stick to the marking paint. Next time I will give the parts a wipe with acetone before painting.

And, with a bit of paint, the carriage doesn’t look half bad?

Even the crappy rivets do not stand out too badly.

Of course, some areas showed up as needing some filler…..

Some time and effort required in some areas to fill defects and divots before the next coat of paint.

I quite like that colour. Maybe with just a touch more blue in it.

And note: NO RUNS, NO BRUSH HAIRS.

Not One of my Skills…Riveting

The cannon carriage, partly disassembled, ready for final riveting.

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.

An eye bolt goes in the X hole.
Note the use of nuts on the rivets where access was difficult.
I give myself 5/10

I learned a few lessons as a result of this session of riveting.

  1. Riveting is a manual and knowledge based skill, which must be studied and practiced.
  2. 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.
  3. The tools must be perfectly designed for the job. The snaps must be the correct shape and size for the rivets.
  4. Rivets from different manufacturers differ in dimensions, even when supposedly the same.
  5. Soft components like aluminium can deform and break when riveted.
  6. 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.

Warts and All

A few more photos of the model Armstrong RML cannon. Close ups which are useful to me, because they show up defects in the finish which need attention before painting.

Makers mark (mine) to be added to the recoil tube cap. And rubber washer to the bumpers.
Screws and bolts to be replaced with rivets
Metal polishing required for the muzzle
Oil holes for the shaft bearings, and replace the wonky rivets
File and finish the trunnion cap keys
finishing and polishing the loader cradle.
ditto more finishing.
Attach the left side buffers. And make chassis wheel axles. Those M5 hex screws are wrong.
Distance hides a multitude of faults

Model Cannon. Final Photos before Teardown

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.

In the firing position.

After the teardown I will complete the insertion of rivets, replacing many of the 8BA screws with rivets.

After firing, with the barrel depressed to 17º, after swabbing to remove persisting embers, ready for the 20lb of gunpowder in a silk bag, with a wooden rod in the middle to prevent the bag from collapsing while being rammed. Then the 80lb projectile with “plate like” copper gas check (to engage with the rifling) is lifted onto the loading cradle and pushed into the barrel with a wooden ram rod. The projectile had a rope quoit around the pointy end to jam it into the firing position, and stop it from inadvertently falling out while the carriage is rolled down to the firing position.

The firing rate for these 80lb cannons, with a trained crew, was about 1 round every 1.5 minutes.

There should be an OH&S sign saying, “best not to stand here during firing”.
Wooden side planks for the gun crew, and a short shelf near the front to rest the projectiles before loading, yet to be made.

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.

Sights Set On Completion

Today the gunners’ platform at the rear of the chassis was completed and fitted. It has vertical handles at each side, presumably for the gunners to steady themselves, while aiming the cannon.

The platform, ready to be attached to the chassis. The wood here is Australian Jarrah. The handles are stainless steel, discoloured from silver soldering them to the side brackets. They will eventually be painted. ps. a day later I decided that the fasteners were too big, so I have replaced them with something more appropriate. Pics later.
The platform in position. This photo shows up my first efforts at riveting. Some of those rivets will be replaced when everything is disassembled prior to painting. Those brass nuts holding the wooden boards are too big and will be replaced also.

So, just 2 more parts to be made for this model cannon. Those are the sights.

The information which I have to base the sights on is a bit sketchy. But I do have photos showing these cylindrical holes in the Port Fairy cannons….

The sights are placed in the holes in the right hand trunnion shoulder, and in the breech.

After extensive searching I found several books which were published in the 19th century. This is the best diagram which I found of the rear sight. It is calibrated vertically up to 3600 yards, and there are lateral adjustments to take into account speed of movement of the enemy. The sight is angled at 2+º to the left to compensate for the rifling, which causes the projectile to deviate to the right. The front sight is located in a relatively shallow cylindrical hole. The front sight is a fairly simple point.

Gunners Platform

Not a great photo of the platform at the rear of the Armstrong 80lb RML at Portland Victoria. But, this is what I started modelling today.
This is the Port Fairy cannon, which is missing the woodwork, but shows the brackets.
These are the brackets which I fabricated for the 1:10 model. I did make some small design changes to make the model. I think that my changes are an improvement on the original, using existing fasteners. The wooden planks and vertical handles are yet to be added.

The central angle brackets are machined from some RSS.

75x25x2mm RSS
Sawed and machined to size. The bent steel is true to the original Port Fairy cannon.

You might also notice that the eye bolts have been added.

Fitting the Loader.

The bracket is now bolted to the chassis. The arm is stainless steel, and the top bracket is silver soldered to the arm. The loader cradle is bolted to the top bracket, the angle being determined with a neat fitting rod inside the bore. The rod looks interesting, no? I will turn up a projectile to sit there.

Then I fitted the bracket which restrains the movements of the elevation gear lock-release…

This is the “locked” position. The handle drops into a recess. The bracket looks a little rough in this magnified view. A bit more filing and sanding required. A simple curved piece encloses the handle. I will make and fit that tomorrow.

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.

Pruning Trees. And how to remove investment plaster from castings.

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…

there is still investment in the grooves and crevices.

Then most of the unwanted bronze branches were machined and sanded off…

still the investment powder clings on….
then the investment powder all disappeared!

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…..

I wonder if holding the angle grinder in a vise, and holding the trigger with a spring clip, will void the warranty?

33.9/34 Not Bad.

It was a bit too warm for casting bronze today. 33ºc/91.4f. But I went ahead. It was sweaty.

I had installed a new thermocouple in the potters oven and it performed flawlessly. Fumes from burning out the PLA and wax from the mold had caused the older thermocouple to behave erratically, but the new stainless steel type was unaffected.

And, as I displayed yesterday, I had made a very ambitious tree with 32 parts to be cast, and a second tree with 2 largish parts.

No vents. No vacuuming of the melt. Just a straight pour.

A few minutes after the pour, the bronze is still at a beautiful fluorescent red heat.
The cast 2 trees. NO bubbles (I painted the PLA trees with a slurry of investment before the investment pour). All parts look perfect, except for a tiny area of moth eaten edge on one of the parts in the top tree. Too small to show up, and quite repairable.
The other side. Not much surface oxidation (phosphor copper used).

So, a very successful pour. Some careful hand sawing required to cut off the parts.

A Record for Number of Casting Parts?

This casting tree has 30 parts. That is a record for me. Admittedly, most of the parts are quite small.

There are 20 eye bolts, 2 cannon loader brackets, 2 cannon loader cradles, and 2 ends of loader arms. Oh, and 3 bevel gear locking lever handle guides. And one extra eye bolt to make 30.

It will be interesting to see how many of these parts are useable.

Note, that the tree has a bifurcation. The parts are so small that I decided to split the flow of molten bronze into 2 trunks.

But, I joined the 2 trunks at the other end, just in case.

Pour tomorrow.

Then I decided to add another mould cylinder. I am making some more cannon chassis wheel brackets, in bronze, after improving the design.

GSMEE meeting tomorrow. But, I will be casting bronze. I might have a few minutes to join in the meeting.

Testing Designs with 3D Printing

Some parts on my model Armstrong cannon could not be made until measurements were checked on the assembled model.

The projectile loader was one such group of parts.

The 80lb projectile obviously sits on the cradle. The carriage is at the top end of the chassis, with the barrel angled down by 17º. The arm with the cradle swings around and meets up fairly precisely with the muzzle of the barrel. I am not sure if the projectile is placed on the cradle before or after it swings around. (does anyone know?)

I had these photos, and a few measurements of the loader assembly from the Port Fairy cannons, so I drew them up in 3D.

The components of the loader are fairly simple, and can be machined rather than cast. But I printed the components in PLA so I could test the design before I started to cut metal.

3 components. The bracket bolts to the chassis, the curved arm, and the cradle.

But, when I positioned the PLA assembly on the cannon, it was clearly incorrect. It did not line up with the muzzle of the barrel.

The only way that I could make the cradle line up with the barrel was to lift the arm out of its bracket by 13mm! I am glad that I did not waste time and material making a metal version to these dimensions! Not sure how this error crept in. But I will redraw the arm with an extra 13mm height.

I have not yet decided whether to machine the parts or cast them in bronze. Both processes are a lot of fun. I will reprint the curved arm in either case.

Watch this space!

Brake for a 5 ton Cannon

Well, actually, it is a 1:10 scale model of a 5 ton cannon. The model weighs around 5-10kg at a guess.

The brake is to control the descent of the barrel/ carriage down the 4º slope of the 5 meter long chassis.

On the original, the brake was a steel band on a steel drum which was attached to the big gear.

The drum is approx 600mm/2′ diameter.

This is how it appears on the scale model..

From the other direction. The stainless steel band winds around the drum, and is attached to a small lever which is operated through the shaft by a much larger lever on the outside of the chassis.

I was a bit apprehensive about this job. The lever is very close to 2 gears. the steel belt has to be properly tensioned, because the degree of movement of the control lever is quite restricted. And the width of the band has to be slightly less than the 5mm groove on the drum.

But, I found these…..

Stainless steel cable/plumbing ties. 4.75mm width, and in various lengths. And quite inexpensive.
The cable ties are sharp and springy. Feeding them into position was tricky. But after bending them around the pins on the shaft I was reasonably confident about silver soldering them with a loop at each end. The soldering was straight forward. Stainless steel silver solders well.
The handle is almost 1 meter long. 96mm brass on the model. It will be pinned to the shaft.
I will adjust the shaft length in the next workshop session.

So, for once, my apprehension was not warranted. The job was fiddly, but no major mistakes!

Typists Correction Fluid

WTF! I thought that this site was about model engineering, metal working etc.

Well. I just need to say that typists correction fluid is an essential tool in my workshop.

Not for typing, I hasten to add. But for silver soldering….

Today I needed to silver solder an extra 1mm thick disk to a tiny part, which already had 2 silver soldered joins. I had spent an entire workshop session designing and making the part, and I did not want it to fall apart when I added an extra component. Which I admit, was an afterthought.

And the central hole in the extra disk HAD to line up precisely with the threaded hole in the previously made part.

I had been advised by another GSMEE member that a metal surface painted with typists correction fluid WILL NOT accept silver solder. I have tried this method once before and it works. This is another demonstration.

In front of the correction fluid is the part, with the extra 1mm disk, silver soldered with the 2mm screw holding the parts together. And after soldering, the screw came out. It was not soldered into the assembly because it was coated with the correction fluid.
So annoying. WordPress used to enable rotating images. Not now. So these are the components to be silver soldered. Fluxed. And parts which I do NOT want soldered are coated in the correction fluid.
The work rests on brass blocks to function as heat sinks, to protect the existing soldered joins. This shot shows the workpiece after soldering. Has the correction fluid worked? Well, you have already seen the evidence. Amazingly, it does work.

This handle locks the elevation gears into position after the cannon barrel elevation has been set. Several more hours were required to file a central tapered ridge into the added material, and a corresponding groove where it rests. It all worked out OK.

Typists Correction Fluid. I hope that it never disappears from OfficeWorks.

Thanks again Frank Marrian GSMEE, and jimmymouse, for this great tip.

And Some More Bling on the Cannon

Attached the recoil tube yesterday. But I cheated. It is a gas strut.

The recoil tube from the front. On the original Armstrong RML’s it was filled with thick “Rangoon Oil”.

But, it is SO close to the dimensions that I required, that I decided.. what the hell. It is 18mm diameter (17.5mm required), and 200mm long (198mm required).

I degassed the strut by drilling a 1mm hole, and the gas came out under considerable pressure. I had to do that, because the strut was too strong for the cannon. Even degassed, the strut has enough shock absorbing action to be useful and realistic. I made some brass brackets and a cap, for visual consistency.

Today I made the lever which locks the elevation gears.

Not much to show for an entire day in the workshop, but it did involve a lot of planning, a bit of CNC cutting, and silver soldering. Still some small details to add.
The Port Fairy original. Some bits are missing.

Happily Using Technology

Yep. To make my models I use a computer for drawing, making lists, ordering fasteners and materials and tools on Ebay and from suppliers, driving CNC 3D printer, driving CNC machining tools. And laser marking parts. I also do a lot of traditional machining, hand filing and sanding.

This is 2mm thick brass sheet. I asked Stuart T, who has a 30w fibre laser, to mark the elevation scale protractor for my Armstrong 1:10 RML cannon. Not sure of the outcome, I supplied some blanks (LHS), and cut out parts (RHS), and a CAD drawing of the part and the text.

The cannon barrel will elevate to 30º, and depress to 5º for firing, although in practice deviations from a degree or two from 0º were rare. Plus there is an extra mark for 17º depression, which was the reloading angle. The numbers which the laser marked are only 0.6mm high. Hard to see with the naked eye. But in scale.

Lasering the tiny marks and numbers took 2 seconds per pass. That is, 2 seconds to make all of the marks and all of the numbers. After some experimenting, we settled on 50 passes. Which was still less than 2 minutes per part.

Click on the following frame to see the video…

How fantastic is that????

So quick, precise and clear. Yep. I am quite happy to employ any new technology which is available to me.

Then today I made the fittings to secure the recoil tube, and drilled and tapped the 8BA fasteners.

The carriage, chassis and bling is really coming together. Just a few more bits to make and install, then the final riveting and painting. Ready, I hope, for Xmas.

The recoil tube is a commercially available gas strut. It was so close to my 1:10 scale dimensions that I decided to cheat, and use it.

I drilled a 1mm hole in the gas tube to release the gas and oil, turned and re-threaded the front end of the piston rod to 6mm, and made the brass supports and end cap. I released the gas because it was too stiff for the model. Even without the compressed gas the strut has some “shock absorbing” activity, and I am quite happy with the decision.

More Small Cannon Parts

I suspect that this post will not be of much interest.

But the parts represent 2 whole days in the workshop, so I am writing these notes for my own diarising more than your entertainment.

The chassis of the model Armstrong RML cannon has a cross bar, which is bolted to the longitudinal bar, and is attached to the side girders with some small, shaped clamps.

On the original Port Fairy cannon. There is a 4º difference between the girders and the central bar.

The crossbar is under the big gear. Still some shaping required to improve the appearance. When I have finished the gaps will disappear. The difference between the original and the model cross bar relates to pragmatics of shaping miniatures. Compromises inevitable. And if you noticed, the fasteners on the left are BA8, and 2mm cap screws on the right. I need to buy more BA8’s.

The cross bar doesn’t look much, but it has 4 bends and a twist. The space was too tight for me to measure the angles, so I bent the cold bar by estimating the degrees by eye. Same with the twist, except that the twist had to be confined to the section not attached to the girder or the central longitudinal bar. So I heated that to red heat with oxypropane. The twist was 4º. But I eye balled that too.

8BA bolts x6 in a hex pattern join the cross bar to the longitudinal bar.

The clamps required some planning. I considered machining them from solid bar, but work-holding was going to be problematic.

So I silver soldered 2 strips together, cut off the pieces, then sanded, filed, and manually bent the angles.

The silver soldered join overlaps by only 2mm, but it survived some aggressive bending. 100mm long. The parts were sawn off, then further sanding, filing, and hole drilling. Workshop dirty fingers with swollen arthritic joints.

p.s. Another day later, more of the same…

This is the underside of the model Armstrong cannon carriage. I have bolted on the 4 cast bronze fittings which hold the carriage onto the chassis. Later those fittings will have wooden/steel disks sandwiched and bolted onto them to become bumpers at the extremes of travel of the carriage on the chassis. All of the cap screws will be replaced later by hex head BA bolts.
this is a view of the underside of the chassis, with the carriage secured above. An unusual view.

I would prefer to use 2mm metric bolts rather than 8BA, which is a similar diameter and pitch, but unfortunately I have been unable to find a supplier of 2mm bolts with hex heads. BA bolts are several times more expensive per piece than metric, and it adds up when using hundreds per cannon.

How to fix a Mac Laptop with a Toothbrush and Metho. and another Cannon Bit.

After a session on the model cannon yesterday, I sat down at home with a glass of red and my laptop.

I was awakened by a phone call, but my bum was wet, and the laptop screen was black. And the laptop keyboard, and presumably my bum, was red with spilt wine.

Dealt quickly with the call. Dried myself off. Wiped the keyboard dry, but it was stained red.

Turned the Macbook on.

DUMB!!! Turn it OFF you idiot!!! I didn’t find that out until later.

Screen remained black. Charge cable light not registering.

Turned the laptop onto its edge and some wine dribbled out.

Still would not turn on. (See previous “DUMB” comment .)

Opened up another computer. Looked up “MacBook Pro Wine Spill” on YouTube. Lots of videos. Obviously I am not the only person to kill a laptop with red wine. Quickly viewed a couple of them.

“TURN OFF THE POWER”. “DO NOT TURN ON THE POWER”. Ok. Didn’t know that. Oh Dear.

“Use a 1.2mm Penta Lobe screwdriver and remove the back as soon as possible. The longer the delay, the worse the problems due to corrosion”

I have a few sets of tiny screwdrivers. None of them had a penta-lobe.

Rang around my computer savvy acquaintances, but none there either.

WHY DO COMPUTER DESIGNERS SPECIFY SUCH WEIRD SCREWDRIVERS?

Oh, I get it. They don’t want end users to fix their own computers. In a pandemic there is not much help from repairers either.

So, next morning I visited JayCar, and bought another set of tiny screwdrivers. They had a few sets with “penta-lobe” screwdrivers. This was the most comprehensive set. $AUD50. Really nicely made, bits held in multi layer case with magnets. Feels quality.

Very happy with this purchase.

Removed the 10 tiny screws under a magnifying light.

This is the laptop innards after I had wiped off most of the red wine.

Didn’t photograph the clean up steps. I was feeling very pessimistic about a successful outcome. Wiped off the red wine. But there was a sticky, syrupy, residue. A great glob of it under the big T shaped label, and a lot more around the vent holes on the right. I guess that the wine got access through those vent holes, and the keyboard.

One YT video showed a repairer scrubbing the electronics with alcohol and a toothbrush.

Oh well, here goes. So that it what I did, using methylated spirits. It felt risky, but the congealed mess did seem to clean off. Then I patted the cleaned areas dry.

Next question. Do I remove more components, to hunt for more areas of spill?

No. I think that I will try it first, just in case my cleanup so far has worked.

So I reassembled the bits which I had removed. Plugged in the power supply. … and the little power supply plug light came on! Hope!

Turned on the computer. Took a while to boot up. But boot up it did. Wonderful.

Next step. Make a complete backup of all of those files which I thought that I had lost.

Next step. Brag about my success on johnsmachines.com using the aforesaid MacBook Pro.

Meanwhile back to the scale model Armstrong cannon. The next photo shows yesterday’s result. Can’t see any change? Look carefully under the protractor. See that tiny bit?

That little piece represents several hours of cutting, silver soldering, filing, and fixing to the cross bar with TINY 10BA screws and nuts. Later it will have a mark to line up with the protractor marks.

So, life seems good again. And more Covid restrictions are being lifted tonight. Yippee. But still cannot see my Melbourne family for another 2 weeks.

BTW. I found some more videos to delete. So I have some more space for posts. But sad about the videos .

Armstrong RML Elevation Protractor

2 days in the workshop, and not much to show…. just one photo.

Yes, the trolley wheel axles need to be shortened. Next time the carriage is disassembled. The recoil tube is just sitting there, for effect.

The curved brass bar is a protractor for measuring degrees of elevation of the barrel. I used High School trigonometry to work out the distance from the pivot point at the centre of the trunnion, to the pivot centre at the fitting under the barrel.

Then cut out the shape from 2mm brass with the CNC mill. That was the easy bit. Although it did takes 3 goes to get the radius of the curve correct.

Today, although feeling depressed after the Cats loss last night, I made the cross bar with the rectangular cutout, then spent a couple of hours bolting it into place. It all works smoothly. The rectangular cutout is 2.2mm wide and 7mm long. I chain drilled with a 2mm carbide milling bit, then milled the slot sides, then filed the corners square. It is stainless steel. Slow work.

I have not worked out how to engrave the protractor marks, which are at 0.25º intervals for elevation, and whole degrees for depression. I could ask Stuart T to engrave it for me. The design and actual lasering would be straight forward, and I am sure that Stuart would help if requested. The problem would be to align the part on the laser machine, so that the engraving occurred exactly at the correct location. Actually, as I type this, I think that I have the solution. Watch this space.

I need to make a pointer next, and to determine the 0º position. The carriage sits on the chassis which is at a 4º slope. Not rocket science, or brain surgery. Just need to get it right!

Next Project?

I made a 1:10 model of this Ottoman bombard a few years ago. This one was made in 1465, and is thought to be a copy of the bombards which brought down the walls of Constantinople in 1453. This one resides in the Royal Armories Museum at Portsmouth, UK, and I photographed and measured it in 2019. It has a bore of over 600mm, and fired stone balls of over 350kg.

Last used in anger against the Brits in 1807, where it and others like it, were instrumental in preventing a British fleet from invading Istanbul (renamed from Constantinople). How many weapons have an active life of ~350 years?

…and the model turned out well. 550mm long, but, it is made of wood.

So I am contemplating making a model at the same 1:10 scale, like the original, in BRONZE. It will have the same shape and size, but will look like and feel like BRONZE.

I still have my original measurements and drawings of the model. So my plan is to print the cannon parts in PLA, taking into account my extra information from the 2019 visit, then to cast it in BRONZE.

I had planned to stop this blog after finishing the Armstrong RML, but maybe , if there is enough interest, I will keep it going for the next project. You will need to let me know if this project will be of interest. Because lately, comments and likes are few, and numbers have been discouraging. And the renewal date for WordPress is approaching. I get it that people prefer videos, but that is not my style. If this written plus photographs style is not wanted then I will not persist.