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.

Riveting the Armstrong Cannon Chassis Model

I am waiting for delivery of the 5 l vacuum chamber so I can commence casting parts for my 1:10 Armstrong cannon.  So today, I spent some workshop time riveting the chassis of the 1:10 Armstrong 80lb muzzle loading rifled cannon model.

I am a total novice as far as solid riveting goes.  The following photos will prove that fact.

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I am holding a new Taiwanese riveting gun.  The girder into which I have just inserted almost 100 copper 2mm rivets is resting on the vice.  The anvil is clamped into the vice.  The snap (home made) is in the gun.

I have marked the surface of the girder with the anvil and snap.  Doesn’t look good, but I am hoping that it will be acceptable after painting.

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I painted the inside of one girder with layout paint just to see if the crappy riveting will be acceptable.  Still considering that question.

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A staged photo of rivet insertion.

And just to lighten this post, yesterday I had a visit from my grandchildren, 2/3 daughters, sons in law, and SWMBO at my workshop.

So I fired up the Fowler 3″ traction engine and gave the kids a demo of filling the boiler with water, lighting the furnace, a discussion about the nature of coal, and a ride.

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Despite the wintery weather, it was a very happy afternoon.   Audrey 4, Edward 4, Charlie 4, and John 7.   And John 70.  We have had an unusually wet autumn, hence the green grass.  No tigers seen.

 

Getting Ready for Casting

Setting up for casting molten metals into shapes for my model Armstrong cannon.  Still getting ready.

Today I made some moulds for dealing with any left over metal melt.  Not a big deal, but it does have to be done before the first melt.  No point realising that there is nowhere to put the left over aluminium or bronze during the pour.  It has to go somewhere.

So today I made some ingot moulds, in readiness.

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The ends of the moulds are sloped to allow easy ejection of solidified aluminium or bronze.

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4 ingot moulds.  Made from 40mm ID thick wall pipe, with long handles.  The diameter of my crucible is 48mm ID, so any ingots made should fit into my crucible later for remelting.

It seems a long time since I have done any welding, and the welding of these items was pretty ordinary.  But the joins seem water tight, so hopefully they will be OK.

Today I fired up the casting oven, to 850ºC, and the load was some ordinary food tins.  They are the correct diameter for investment moulds.  I wanted to see if the tins would cope with these temperatures. (after removing labels of course).

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3 ordinary food tins, at 850ºC.

It became apparent, that the tin joins were welded not soldered.  And the inside and outsides of the tins were covered with some sort of paint or plastic, because it flaked off.  But the metal cans remained intact.  Admittedly, when hot they were VERY soft, but when cooled they retained their shape, and were quite stiff.   I would be prepared to try these for single use moulding projects.

I have realised that my investment plaster mixing bowl is too big for the vacuum chamber which I had bought.  So I have ordered another vacuum chamber, and waiting for it to arrive before starting a mix.  I am using the delay to gather items like the ingot moulds above.

It will probably be another couple of weeks before I am ready to cast.   Meanwhile my 2mm rivets have arrived at last, so I will get back to the riveting.

TURKISH BOMBARD – a-post-script. And metal casting setup ready.

I made this 1:10 scale model of the Turkish Bombard which currently resides in the Royal Armories Museum, Portsmouth, in 2016.  I specify “currently” because I originally saw this cannon in 1979 at The Tower of London.  And long before that it was used in Turkey, guarding the Dardanelles.  Quite likely used in anger in 1805 against a British fleet, approximately 340 years after it was made for Sultan Mehmet “the conquerer”. 

And I re-visited the original in May 2019. It seems like half a lifetime ago. Mainly I visited the UK to see the Trevithick dredger engine in the London Science Museum, but the Turkish bombard was the second reason. I could not find a photograph of the touch-hole in the bombard anywhere. And my requests to the museum went unanswered.

The original bombard in the Royal Armories Museum, Portsmouth, UK.

So, here is my photograph of the touch hole, in case anyone else is inclined to make a model. I guarantee that this is the only photo of the touch hole which you will find, with my hand anyway.

The Turkish bombard touch hole
My 1:10 scale model of the bombard. I still have not added the touch hole.
The Arabic script around the muzzle. Not as good as in the original. But as good as I could manage in 2016.
and the large thread between the barrel segments


So, I made this model, in wood, as a practice run, intending to make a bronze model eventually.

The reason for this post script is that I had a question from a reader about a remark which I had made in 2016. And I could not find my original photographs. So I took some more, as you have seen.

And……… very excited to announce that I now have a foundry setup, and could possibly make a bronze example of the bombard. But first I intend to obtain some casting skills, by making parts for my 1:10 Armstrong cannon.

I replaced the analogue controller with a digital type in the potter’s oven which I had recently purchased, and today my wiring was checked by an expert before we ran a test run. (thanks Stuart!) All good, up to 750ºC, which is enough for preparing the investment molds.

Here is a shot of the oven, and the metal melting furnace.

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from the right, the melting furnace which should be adequate for 3kg of brass/bronze,  and the investment oven. The oven might also be useful for metal tempering. Note the Hebel bricks behind the oven.

Hopefully, the first attempt at a casting session in a couple of days.

 

Armstrong Cannon Wheel Assemblies -2

rear wheel and support

There are 3 major components of each wheel assembly, plus the wheel, axle, and king pin.

The wheels, axles and king pins are straight forward metal turning, but the other 3, the wheel bracket, the king pin post, and the chassis bracket, are castings in the original.

For my 1:10 model I am planning to cast the king pin column, and the wheel bracket.  But I will fabricate the chassis brackets.

There is one chassis bracket for each of the 4 chassis wheels, and they are all different.  Front different from rear, left and right hand versions.  And each one has angles of 90º, 30º, 20º, 6º, 2º so the machining was quite a mental exercise.  No major stuff ups though.

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Here is the main component of the left hand rear chassis bracket, being held in position.  It will be bolted on later, and have several flanges silver soldered to it.   Those M2 cap screws will be replaced by rivets eventually.

Meanwhile, having decided to cast the king pin casing, and the wheel bracket, I spent many pleasant hours (or was it days?), drawing them.  Then yesterday, I 3D printed an example of the king pin casings.

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2.5 hours to print PLA examples of rear (left) and front king pin casings.  I need to see the original cannon to check some details before committing to cast these in bronze.  The PLA parts will disappear during during the casting process.  (A pity.  They are quite attractive No?)  You can see why I chose not to machine them out of bar stock.   3 pin holes in the left hand print ? the result of not storing the PLA spool in a dehumidified container.

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So, it might not look like several days of computer and workshop time, but that is how long it has taken.

In Australia we have had some easing of Covid-19 restrictions, but not opening of museums or historic collections of cannons.  So I still cannot go to Warnambool (a 2.5 hour drive) to check details on their Armstrong 80 pounder rifled muzzle loader.  Flagstaff Hill Maritime Museum does not answer their phone.  Hmmm.  Maybe I could climb the fence and sneak in……    but maybe not.

Armstrong Cannon Chassis Wheel Assemblies

The steel chassis is virtually finished, although I am delaying inserting the final rivets which join the girders together, in case I need access to the individual girders for more machining or drilling.

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The 2 chassis’ are not identical.  Can you spot the differences?  And still waiting for more rivets to arrive.  The copper colour on the front one resulted from dipping it in well used sulphuric acid after some silver soldering.

 

Considering how to model these wheel assemblies…..

front wheel and mounts

The front wheel assemblies

rear wheel and support

The rear wheel assemblies

The rear wheels and supports are larger than the front ones.  But the top views are essentially the same.  The wheels themselves present no difficulties.  They will be turned from 50mm diameter steel rod.  And the axles will be all identical.

But, those supports are complex, and will need to be silver soldered parts, or possibly cast from 3D printed lost PLA bronze or brass.  Just drawing them was challenging.

This is a complex project, and the parts are complex.

Considering that the original cannon barrel was made in 1866, and the steel/iron chassis made approximately 20 years later (the original barrels were mounted in a wooden carriage),  the standard of the workmanship in the originals is simply superb.   Even at 1:10 scale, and using modern equipment including CNC machinery, I am struggling to match the standard of fitting steel pieces together so neatly.  I am in awe of the original engineers.

(and by the way.  Neil M, who very kindly loaned me the rivet gun which died, has loaned me a replacement gun.  The replacement gun is a bit bigger, and more fierce.  It requires more care in not overdoing the hammering, and bending the steel parts or producing “two-bobs” in the work piece.  “Two-bobs” will be understood only by older Aussies?  They are unintended dents in the workpiece produced by hammering.)

Riveting for Real

The strength and resistance to twisting and other movements of the Armstrong cannon is in the chassis.  Specifically the design and strength of the longitudinal girders, AND the box section structure at the front of the chassis.

The box section has been a challenge in the 1:10 model.  Actually, it has been a bit of a nightmare.

It has taken me 3 full day sessions to work out how to construct this assembly, to make the parts, to join them together, then a lot of filing to make the assembly fit the girders.

And, of course, the parts are riveted together, and I am a total novice at riveting.

So this is the result.  Not totally finished and assembled, but getting there.

Again, I left my camera at the workshop.  These are photos which I took with my phone.

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The box section is an assembly of parts.  The ends were silver soldered.  The panels which show are steel, and will all eventually be riveted to the end sections.  At this time, some joins are still just bolted and nutted.

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This is the front of the chassis.  The rivets look OK yes?

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And the inside rivets were the first ones to be inserted.  Mostly worked OK.  They are copper, will eventually be painted the same colour as the girders.

And after the riveting, I have spent almost a full day of gentle and progressive filing to make the box section fit the girders.  It all fitted beforehand.  But after riveting, nothing fitted.  All of that hammering clearly changed some of the dimensions.  But, despite all of my pessimism, it all eventually fitted.

Now, I have another chassis to make.

Do I repeat the method, or maybe try something more efficient.  Like making a solid block of brass or steel, shape the exterior to dimensions, then hollow the interior?  Still pondering that one.

Part of the equation is that the riveting gun died.  Not sure what happened.  Maybe a blown O-ring?   The final few rivets in the above pictures were hammered.  My hammering is definitely not as neat as the rivet gun.   I do have a rivet gun on order, but they are estimating an arrival date of the END OF JUNE!   I cannot wait until then.  And the faulty gun is not mine so I feel diffident about pulling it apart and maybe repairing it, maybe really screwing it up.

The last time that I cursed the virus I lost 25% of my readers, so I will just think it.

 

Book Review. “Mortal Wounds”. Not for the faint hearted.

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MORTAL WOUNDS

THE HUMAN SKELETON AS EVIDENCE FOR CONFLICT IN THE PAST

By Martin Smith

Hardcover.  £25 RRP.  Pen-and -Sword. UK.

 

This book was not a relaxing read.

The author, Dr Martin Smith, is a Biological Anthropologist with particular interests in prehistoric populations.  He examines human remains, taking a forensic approach, to try to determine whether violence was the cause of death.  Since ancient remains rarely consist of more than skeletons, soft tissue injuries are not evident.  So, the violent causes of death where bones were not injured are not assessable, and the incidence of violent deaths is certainly underestimated.

Crushed skulls, decapitations, cut wounds in bone, shattered bones, remains of weapons such as arrow heads and or spear heads inside skeletal remains are all assessed as violent deaths.  Evidence of bone healing is also taken into account.

The book is divided into eras, from the deep past, the Mesolithic, the Neolithic, the bronze age, the Romans, Medieval England, the high Middle Ages-Renaissance.  It does not deal in detail with the twentieth century.

Although the descriptions are often shocking, some fascinating conclusions are reached.  Human history, it appears, has always been violent.  At least 10% of all deaths in the “stone age” were violent, usually as evidenced by skull fractures, and contradicting the traditional “peaceful primitives” view of the era.  The incidence of violent deaths is highest in the lowest, worst nourished classes, in all societies.  Wounds resulting from black powder firearms were often more severe than from modern guns.  (to mention just a few examples.)

There are many illustrations, line drawings and maps in the 290 pages.  The text is a pleasure to read, although, I confess, I had to take it in small doses.

Another really fascinating read from Pen and Sword.

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A Transom on a cannon. And a lost hearing aid.

 

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After a fruitless 3-4 hours searching for my lost hearing aid, I decided to make a bit of progress on the Armstrong cannon chassis.  At least I got the workshop floor swept clean for the first time since last winter.  The tigers should be hibernating in this cold weather.

In the above photo you can see that the rear cross member, which I have named the “transom”, is now bolted into place, with 14 M2 bolts and nuts.  Later these will be replaced with solid rivets.   I reckon that I had about a 70% success rate of inserting the tiny M2 nuts.  The other 30% are somewhere on my workshop floor… probably keeping the hearing aid company, wherever it is.

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When those connections were made, ensuring that the upper girder surfaces were parallel, I filed the angle brackets flush with the girder surfaces.  To ensure that the file did not scratch the girders, I rested the end of the file on a sheet of paper.

The next job is to make the front joining piece of the chassis.  It is a box construction, so will be more complicated, but should make the chassis  quite rigid.

It is a bummer having only one hearing aid.  About $2000 to replace the lost one.  I would have preferred to spend that sort of money on a tool.   Or a good drone.  But SWMBO is adamant.” get that hearing aid replaced!! ” (at least that is what I think that she said.)

 

Lost hearing aid.

Sorry, no photos with this one.  As I was leaving my workshop I realised that I was missing one of my hearing aids.  It was dusk, raining, and I spent almost an hour searching for it, but no luck.  Then I forgot to bring my camera.  So no photos.  Big cleanup of the workshop in daylight tomorrow.

A half day in the workshop today.  Finished silver soldering the chassis angle brackets, then fitted them, and secured them to the girders with bolts.  In order to make sure that the brackets are correctly located for the drilling, I glued them with Super Glue initially.

The first half of the day was spent on the computer, working on Queen Victoria’s Royal cypher which is on the top surface of the cannon barrel.

emblem

The “VR is for Victoria Regina”.  “Honi Soit Qui Mal Y Pense” is the motto of the Order of the Garter.  It translates from the French as “Shamed be (the person) who thinks evil of it”.

It appears to have been machined into the barrel.  On my model it will be about 12.5 x 20mm.  My friend Stuart has a fibre laser which was used to permanently mark guidelines into 2 steel grinder rests (featured in earlier posts), and I am hoping that it will work similarly to put the cypher onto my model Armstrong cannon barrel.  Another option would be to V carve the emblem, using V Carve Pro.  Whichever method is used, I needed a bitmap file of the emblem.  I found several with a Google Images search, but they were very low resolution.  I should have made a rubbing of the cypher when I was at the originals at Port Fairy.

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236×277 but I have spent some time with a drawing program (Corel Draw) tidying up the image, then converting it to vectors, suitable for V Carving.  The laser can interpret a bitmap file.

The curve of the barrel must be negotiated during the lasering or V carving.  Still considering options for that.

So, when the Covid restrictions are lifted, that will be one of the first visits.  To Stuart and his laser.   A practice run on some scrap pipe first.

Armstrong RML. A Little More Progress!

Only a half day in the workshop today.  Wednesday is my Model Engineering Society weekly “Zoom” meeting, and I would not miss that for quids.

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But, I did get into my workshop after that.  And this is what I made….

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I am trying to make a bracket to join the side girders of the Armstrong RML cannon to what I will name the “transom”.  The transom is the lump of steel joining the side girders at the back of the chassis.

“No big deal” you say?  Well, that bracket has angles of 90º, 4º, 6º,  and some indeterminate ones.   And must sit flat with 2 pieces.  And is a single piece of steel.

First I tried to bend a piece of 2mm steel.

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Even though the bender is rated only for 1mm, it managed 2mm thick plate.

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Plus some hammering in the vice…

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…but machining all of those angles and distances was just too difficult….   This steel effort was just not up to scratch.   Look at the gap under the bracket.  Yuck!

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I cut out some brass pieces, and used a vertical belt sander (the Radius Master), to get them to fit snugly…..

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then cut some separate pieces to complete the brackets and secure the transom…..

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checking the fit of the right angle piece…

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then silver soldered the pieces together.  The bits of steel are to keep the brass pieces in position during the soldering.

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That is the angle bracket being held to the transom by my rather dirty fingers.  But, it is all nice and tight, and will do the job. Rivet holes yet to be drilled.   Soldered joint? I hear you ask?  “As strong as the parent metal” I answer.   One made.   A bit of filing required.  And 3 more to go.  They will be painted the same colour as the girders eventually, so who will know that they are not steel.  Just you.  don’t tell, or else….

 

Armstrong RML Model cannon. Assembly -1

Not much happens in each workshop session.  I am still a bit unsure whether I should only post when some significant progress has occurred, or whether the minute daily progress is enough.  Whichever occurs depends on my mood.  At the moment I am posting daily progress.  If it is just too trivial and boring, well, hang in there.  No doubt there will be big significant gaps in the future.

Today I thought about how I would assemble the chassis for the Armstrong cannon.  And I decided to do some woodworking.

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So, I machined a block of wood, exactly the size to separate the chassis girders.

Wood has an advantage over aluminium or steel.  Apart from being cheap, it is slightly compressible.   Here, I have accurately machined a block of wood, and by adjusting the tension in the G-cramps, I can adjust the distance between the girders to exactly what I want.   And using the granite setup block to keep the upper girder surfaces exactly parallel.

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Getting those girder surfaces exactly parallel, on a granite setup block.

 

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Then I marked out one of the end pieces, filed out the girder flange recesses, and fitted it into place.

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The end piece will eventually be riveted into place, using an angle bracket.  The dented girder corner top right, occurred when I dropped the girder onto the workshop floor!  Or maybe it was a Russian shell hit.

So, not much to show for a 6 hour workshop session, but actually, some decisions made.  And more small steps.

And a BIG discovery!  Another  Internet search has shown some more of this exact cannon at Warnambool, Victoria.  And from the few photos on the net, those Warnambool cannons are more complete than the ones which I measured at Port Fairy!

Ah.  Fuck this virus.  I want to go to Warnambool.

 

 

Small Steps. Armstrong Cannon.

6 hours in the workshop today.  I am constantly surprised at how little progress appears per session.  Also surprised at how quickly the time passes.

I had left the external dimensions of the cannon chassis girders rectangular, to facilitate holding the items, while doing as many machining processes as possible with the rectangular shape.  But today I bit the bullet, and made the final girder shape.

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There is a 4º angle at each end, and a 6º slope along the bottom of each girder.  Also, the top flange is 11.5mm wide, and the bottom flange is 14mm wide.

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Setting up for the bottom 6º angle.  The 4º ends had been machined before this.

The 4 girders are all looking good.  Next to start making end pieces and brackets.  I am still waiting for rivets to arrive, so the assembly will be bolted together initially.

Book Review. The Trafalgar Chronicle – 4

THE TRAFALGAR CHRONICLE

New Series 4

Edited by Peter Hore

Softcover.  £20 RRP.  Seaforth Publishing.

 

“Dedicated to Naval History in the Nelson Era”, the fourth volume in this series contains 21 essays, richly illustrated, and clearly reflecting the fact that the authors are enthusiastic, knowledgeable and articulate about their subjects.

 

This is a book to be read from cover to cover.  It has classy feel, the illustrations and maps are excellent, the topics interesting and eclectic within the period.

 

I particularly enjoyed the chapters “The Decaturs”,  “Nelson Was an Irishman”, “Russians on the Tagus”, “Captain John Perkins” (the first black officer in the Royal Navy) and “The Carronade”.  The last because this reviewer has a particular interest in carronades.  If I might take the liberty of showing a personal item….

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Photo 1  Model carronade made by the reviewer 2015

The essay by Anthony Bruce is the best description of the history of carronades which I have read.  Particularly the descriptions of naval actions where carronades made a significant contribution.

 

I eagerly look forward to further volumes in this series.

 

91 x 4 drilled holes. Yes, counting.

Today I drilled the girders of the chassis under the Armstrong cannon.  Each girder has 91 rivet holes.  Later I will need to drill more for the gear shafts, and for the center pivot bar.

The holes are 2mm diameter.

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The mill drill setup. Re- indicating the vices again took me about 45″.

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Firstly all of the holes were center drilled, then drilled through.  The rivet confirmed a nice sliding fit.

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364 holes, through 5mm of steel done with one center drill, and one 2mm drill.  That is pretty impressive IMO.  More than 1.8 meters of steel with 2 drill bits.  And using my olive oil and kerosene lubricant-coolant.   And the bits still seem to be sharp.

Each girder took about 28″ to drill the 91 holes.   CNC of course.  It has been a while since I said it….. “I love CNC”.

 

Armstrong RML Cannon Model. Making angle iron pieces.

There are quite  a few pieces of angle iron in the Armstrong cannon.  In the original they measure 95x95mm, and are about 15-16mm thick.  Also, there is a definite radius between the 90º faces.  At my 1:10 scale, the material becomes 9.5mm x 9.5mm, and about 1.5mm thick.

front compartment detail

 

After considering various options, which included using extruded aluminium, and bending some sheet mild steel, I decided on the following solution….

I bought some offcuts of RHS (rectangular section)  with 1.5mm steel thickness, and used a bandsaw and milling machine to produce the required dimensions in steel.

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This is a piece of 50 x 25mm rectangular section steel which has been bandsawn in half, then the corners cut off to produce 10x10mm angle of the correct thickness.  Sawn pieces on the right, ready to be tidied up on the mill.  The bandsaw really takes only a 5/8″ wide blade, but that is a 1″ wide blade which I made up with a silver soldered join, and it works fine!   Note the improvised wooden fence.

 

Armstrong RML Model Cannon Parts

Firstly, on the subject of metalworking lubricants, I have previously mentioned my homemade mixture of kerosene and olive oil.   And here is my favourite lubricant…..posing with the not quite finished cannon chassis girders…..

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For this model cannon I need quite a few sheet metal parts.  At 1:10 scale the final metal thickness is 2mm and 2.5mm.  Having had a good experience with laser cutting the HSS cutters for the rifling tool, I decided to send an electronic file to the laser cutting firm, and see how the parts turned out.  I decided to not include the rivet holes, thinking that the final positions might not be completely predictable.  If all goes well I will probably include all of the holes in future orders.

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I ordered enough parts for 2 cannons, and some spares for the inevitable stuff ups.  (or should it be stuffs up?).  If I do not use the spares I might offer them for sale later, along with my plans.

The accuracy and quality of the cuts seems excellent.  All of the parts will require final fitting and drilling for rivets, shafts, etc.   I was pleasantly surprised at the modest cost of these 30 parts.

 

So next I can start assembling the chassis.  Lots of riveting.  About 500 rivets per cannon. Another skill to be acquired.  Fortunately for me, one of my model engineering club colleagues used to work in aircraft manufacturing, and he has spent a session teaching me the ins and outs of installing solid rivets.  And loaned me a riveting gun suitable for the 2mm rivets which I have chosen.  Thanks Neil!

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The gun is about 40 years old but it works well.  The snaps are all imperial, so I made one, and modified one to fit the metric 2mm size.

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The blank snap in the ER collet is an unhardened punch blank.  Here being drilled with a carbide ball nose end mill.  Not exactly the right size, but with some fiddling I got it very close.  Since I am intending to use copper rivets I will not harden the snap.

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My initial riveting practice run in aluminium was a bit unimpressive…..

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….but I did improve.  These are almost up to scratch.   In aluminium.

And finally for this post, I drilled some holes in the muzzle of the barrel.  Do you know why they are there?

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A staged photo, using the 3D printed barrel, to show the drilling setup.

 

Armstrong RML Chassis Girders

 

chassis R rear obl

 

Having made the decision to try to mill the girders from solid steel bar, I bought some 50x16mm bar and cut it into 400mm lengths.

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Then milled it to 46.4 x 14mm, then used carbide end mills to form the girder profile.  This process produced a large amount of hot, sharp chips, and took 2 full day sessions in the workshop.  Each evening I spent about 30 minutes pulling bits of swarf from the soles of my boots with pliers.

And I discovered the limits of my milling machine.  The 5hp spindle motor never hesitated.  Nor did the axis AC servos.  I did manage to chip the cutting edges of  a 12mm carbide end mill when it dropped onto the milling table.  And I blunted another one.  Not sure how that happened.  Maybe hit a hard bit in the steel.   No, the limit of the machine was the ability of holding the end mills in the ER40 collet chuck.  If I pushed the depth of cut or the feed rate too hard, the cutter would start to move in the chuck.  I managed to ruin one work piece in discovering that fact.

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There is virtually no distortion resulting from the milling.  The apparent bend in the photo is photographic distortion.

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The Vertex milling vices are within 0.02mm for height.  I picked up the second vice cheaply on Ebay a couple of years ago, with this exact purpose in mind. (milling longish workpieces)

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3 made.  One to go.  Plus the bottom 6º shape and the 4º ends.   Each 4.5mm deep pocket takes about 25 minutes, at 300mm/min feed rate, 1.5mm depth of cut, 2700 rpm.

I should be able to finish the girder shapes tomorrow.

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These milling marks are visible but very not finger tip palpable.  Any suggestions for a good method of improving the finish?

Then to mark out the rivet positions, and insert about 100 rivets into each girder.  In the model these will mostly be decorative.  In the original they held the components of the girder together.  Luckily for me, a fellow member of our model engineering society is a very experienced riveter, having worked in aircraft manufacturing, and he has offered to spend a session teaching me some basics.  In the original cannons, the rivets are superbly neat, regular, and obsessively carefully laid out.  I will try to do likewise.

Armstrong RML. The Chassis -1

 

I will start by making the main girders.  At 1:10 scale they will be 400mm long, 11mm wide and 46mm deep.  Some fabrication will be required.

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Many rivets required.  I will need to improve my riveting skills.  One issue to be decided. Do I use copper (easy) or steel rivets (authentic)?.  Whichever, they will be eventually painted the same colour as the girders.

 

chassis R rear obl

And another decision.  Your opinions invited.  2 methods for fabricating the girders.

TIG weld the flanges top and bottom (right).  Or, (left) join 2 pieces of angle iron, then TIG weld the bottom flange.  I don’t like the top groove to be filled.  I do not really want to paint the surface that the carriage wheels roll along.

It is a very long time since I did any TIGging, so maybe some practice runs first…

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And another option comes to mind….   just to machine the shapes out of solid bar.  I think that I will try TIG first.

Later….   just remembered.  I don’t have any TIG gas.  Easter.  Bum.  OK.  Back to square one.  Maybe I will try to mill the shape from bar…..

Model Armstrong Cannon. Machining the trunnions-3.

On my “reject” barrel the silver soldering was problematic, and one trunnion was subsequently glued into place with Loctite 620.  This proved to be so effective, clean, and controllable that I used the Loctite for the main barrel.  The following video shows the Loctited trunnions being machined, and showing no signs of being dislodged.

It also shows a possibly dodgy but successful method of rounding the ends of the trunnions.

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The finished trunnions and shoulders.  Resting on a 3D printed platform which is quite handy.

Click on the arrow to see the 5″ video.

Armstrong RML Cannon Trunnions – 2

Silver soldering the trunnions into the barrel and the squared blocks did not go well.

For a start, I did not know the composition of the steel of the barrel.  The trunnions were/are silver steel, and the blocks were mild steel.  So it is possible that I did not use the best flux.

And the barrel is quite hefty, so I knew that it would require a lot of heat to get it to temperature, and to keep it at soldering temperature.  So I used a large oxy-propane torch, and heated it to dull red heat.

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The steel pieces fluxed and wired together, ready for heating

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It was a cool day, but the heat output from the red hot barrel was ferocious.

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Soldered, but one side was not good, and a hammer blow dislodged it.  Damn.

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The good side, partially machined.

I dithered about how to deal with the faulty side.  I was not enthusiastic about re-soldering it, expecting that the good side would fall apart.

So I cleaned up the pieces, and used high strength, high temperature, Loctite 620, to join the pieces.  The machining will test the strength of the joins, so I will give it the full 24 hours before testing it.  This is the “reject” barrel.

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Still pondering how to join the trunnions of the “good” barrel (front).  I will discuss it with my colleagues tomorrow when we have a Model Engineering Society meeting on “Zoom” video link.  The 3D printed barrel at back is a handy “how it should look” example.

 

 

 

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