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.

Tag: Armstrong RML cannon

Trunnion Mounts -2

It took a whole day making and fitting  the top caps of the trunnion mounts from brass.

P1074265

A 76 x 76mm piece of brass was milled to 10mm thickness.  The trunnion straps will finish at 9.5mm , giving me a 0.5mm machining allowance.

P1074269

The 4 straps were cut out using a new 4mm endmill.  Rounded internal corners were milled square, and the bottom tabs were milled to 2mm thickness.

P1074270

2mm wide slots were milled into the brackets, and ends of the slots were filed square.  None of my rifling files were small enough, so I ground one to size, leaving the faces and one edge  intact.

P1074276

Trunnion mount almost finished.  Pins in the tags to come, and they will pull the strap down tight with a cam action.  The half circle line on the bottom bearing is a painting border to delineate the bottom bracket from the bronze bearing surface which will not be painted.  If you inspect the full size trunnion in the previous post you will see what I mean.

P1074274

P1074273

Now I can take some measurements of the model, and start the barrel elevating gear.  There are 4 gears to be cut, including  bevel gears, handle, shafts, gear case, and some complex mounts.

A Chuck in a Chuck

Sometimes, the chuck in your lathe is too big.

I needed to machine some of the aluminium castings which I had made for the cannon chassis.  They were too high by 1-2mm.  But, the flanges were delicate and thin walled, and although the ends were flat and roughly parallel, they were not actually parallel.  I wanted to use my most rigid and precise lathe, which is the Colchester Master 2500.  But the bore on the chuck was greater than the diameter of the part which I was turning.

So this is the setup.  A chuck in a chuck.

PANA4083

The Colchester 3 jaw is 200mm diameter, and it neatly holds a 80mm chuck off my Boxford TCL125 CNC lathe, which holds the part.  It is a centre column from the scale model Armstrong gun which I am currently assembling/making.   It is a bit irregular, with thin 2mm flanges and fins.  I really did not want to damage it, but it needed 1-2mm trimmed from its height.

So, I held the part in the 80mm 3 jaw, centre drilled it, and supported it in the 3 jaw and the tailstock.  It worked well.  No disasters.

PANA4086

I machined the three castings which I had made.  And reversed them to machine the bases.   The setup worked well.   I need only 2 of these, and could use any of them.  The machining did reveal some porosity of the castings, but overall I am quite pleased with the end result.

p.s.  You might notice some advertisements in my posts from now on.  Unfortunately I am at my storage limit on my current WordPress plan, despite deleting virtually all embedded videos, and placing the main ones on YouTube.  I am facing the prospect of either deleting old posts, or increasing my WordPress payment plan to a business plan, which is substantially more expensive.  I have decided to see if monetising the site will cover the cost of upgrading to a business plan.  I do hope that the ads will not be too intrusive.  Let me know what you think.

Armstrong Cannon Chassis Wheels

The assembly of my Armstrong cannon is progressing more slowly than I anticipated.  No excuses.  Just lots of holes to drill in precise positions, parts to turn and mill.  And my workshop sessions have become shorter in the winter cold.   Not that I mind the cold.  I just light my workshop wood fire to remove the chill.

Today I have been making the wheels for the chassis.

 

PANA4079

Not a great photo. It shows a front wheel, 33mm diameter, turned from stainless steel. No axle yet.

PANA4080

And a rear wheel, 50mm diameter.   Yet to have the track groove turned into the periphery.

PANA4077

I thought that the wheels would be easy to make.  Just a bit of basic turning to size and form turning for the track groove and decorative relief on the faces.  But as usual, I used whatever material I had on hand in the size.  In this case stainless steel.  It looks great when turned, but does work harden quickly, causing tooling problems.  Parting off, through 50mm of hardened stainless steel is not much fun.  In the end I used the band saw for parting, then tidied up the ends on the lathe.

 

My Daughter Has Caught the MetalCasting Bug

For some reason which I do not really understand, my youngest daughter has become interested in my metal casting activities.

First she watched me do a molten aluminium pour.

Then she rang me a day or two later and asked if she could have a go.  She really wanted to do it in brass or bronze, but as a relative beginner myself, and with only one episode of molten brass, and that one did not go so well, I demurred, and said that her first effort would have to be in aluminium.

So I prepared 3 flasks, printing the plastic parts, and gluing them into a wax tree, then slowly heating the flasks in the potters oven, up to 750ºc over 8 hours.  Then lowered the oven temperature to the pouring temp of 710ºc.  And preparing the aluminium melt at 710ºc.

When Eleanor arrived, we had a couple of practice runs with flasks full of sand, so she could get used to the weights and handling the tongs, and the various movements while wearing the protective gear.

Then the pour.   This is Eleanor’s video of the event.

 

I admit to some substantial reservations about this exercise, but Eleanor listens carefully, asks intelligent penetrating questions, and follows instructions precisely.   Full marks.

And, a very successful pour!

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.

IMG_8625

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.

IMG_8627

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

IMG_8628

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.

 

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.

PANA3767

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

PANA3769

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

PANA3770

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”.