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.

It got worse

After yesterday’s post my readers were very supportive and nice. Made the post worthwhile. Thanks readers!

So today, I machined off the bent shaft, silver soldered on a new bigger one, and re-machined the damaged brake drum. It looked resurrectable.

Silver soldering a new, bigger (13mm dia) shaft. Note the damged teeth, filled with silver, and the brake drum, hammered roughly into shape, and filled with silver.
and then machined the shaft to 12mm, perpendicular to the gear face.
And then milled new gear teeth….
and it looked really beautiful. Ahhhh!

BUT!. There was a line in the gear cutting program which I had checked, but not noticed. It said Y0. 3 lines earlier the program said G0. If you program CNC you might make the connection. With 3 lines difference, I did not spot the problem. But this was the result….

Fuck, Fuck, Fuck.

The CNC mill did what it was told to do. Really buggered about 3 days effort. NOT impressed with Mach 3 Wizards for gear cutting.

I will look at it again tomorrow, to see if it is fixable, again. Excuse my French.

Learning from MISTAKES

It is said that you learn from your mistakes.

Actually, I think that you TRY to learn from your mistakes.  It makes you feel a bit less stupid when you make mistakes.  Or, at least, it puts a bit of worth into having made a mistake.

At the rate of my mistakes in recent days, I should be turning into an Einstein.  Somehow, I doubt that is happening.  I think that I will stick with my motto of avoiding making the same mistake more than 3 times in a row.

Yesterday, I was cutting gear teeth into the big gears which I had cast a few days earlier.  Due to the mistake of not allowing for shrinkage of the castings, the wheels were almost 1mm smaller diameter than planned. (#1.). That meant that the wheels would have 55 teeth, rather than the planned 56 teeth.  Not a big problem, just an annoyance.

Also, I had not cast a shaft in the gears, or any method of holding the castings for teeth cutting, (#2) so I had to drill a central bore, insert an 8mm shaft, and solder it in position.  I should have used steel for the shaft, but for some reason I chose brass. (#3.)

Then, I could not find my module 1 gear cutters.  The  cutters, I knew, because I had seen them recently, were in a small cardboard box.  I went to where they were usually stored, and they were not there.  OK.  I must have put them somewhere else.  Then spent 2-3 hours searching every shelf, drawer, bag, box, floor, machine…. you get the picture.  And could not find them.  So I searched my vehicle, the other shed, and could not find them.   Had I loaned them to someone else?  Surely I would remember that?  So I went and had a cup of coffee.   Hmm.  What next?  OK, start searching again, going over previously searched spots in case I had missed them.  So, first to the cupboard where they were usually stored.

And there they were.  Exactly where they should have been.  Well bugger me!  (#4).  There was a small upside to this long and frustrating search.  I had found a few other tools which I had not seen for quite a long time.

So then I commenced the gear cutting.  55 teeth into the bronze wheel.  The setting up of the CNC rotary table on the mill, attaching the cutter to the arbor, cutting teeth marks onto the circumference to check my calculation of the number of degrees per tooth (360/55 = 6.545454º….).  All going well.   Each tooth required a cut 2.66mm deep.  But I was a bit concerned about that 8mm brass shaft.  Would it bend under the pressure of the tooth cutting?

So, I cut the teeth in 2 stages.   1.5mm deep for the first cut, 2.66mm for the second.  The first cuts went well.  Looking good.  After a complete circuit, the partly cut teeth were all even, and gleaming.  So, onto the full depth of 2.66.

DISASTER!  (#4.). When I attached the cutter, I had carefully placed it on the arbor so that the securing nut would tighten, rather than loosen with the cutting process.  But I had got it wrong.  Totally wrong, and it loosened!   BAANG.  I hit the big red button.  The mill spindle stopped, but the now loose cutter was still spinning wildly.  What if it comes off while spinning like that?  Would it fly across my workshop, cutting whatever it hits? Like me?

When I bought a woodworking spindle moulder many decades ago, an uncle advised me to NOT use it.  He had seen a co-worker die, when a cutter flew off a spindle moulder, slicing into his abdomen.  I did use the new spindle moulder, but with great caution, and never had any problems.  

Visions of the gear cutter slicing into my belly.

But, the cutter slowed, then stopped, to my relief.

A quick look at the workpiece was disheartening.

The brake drum attached to the gear was bent .  A spoke had a big gash.  The tooth which was the culprit for this disaster was gashed too deep.  and the shaft was bent to a crazy angle.

First thought.  “Bin it and start again”.   Steps to make another big gear.   1.  3D print a new PLA gear (with machining allowance this time, and include an oversize shaft).  2. Make a casting tree. 3. Mix and pour the investment. 4. Dry, burnoff, and bake the investment. 4. Melt the bronze and pour. 5. Machine the gear blank, cut new teeth.  2 days estimated, if all goes well.

Oh well.

No photos of the damaged gear.  Not in the mood.  But I did take a closer look.   I wonder if it can be repaired.  Maybe the distorted brake drum could be bent back into shape?  Or cut off totally, and silver solder on a new one? Fill the defects, and tidy up the damage.

I decided to call it a day.   But first I used a hammer on the damaged bronze gear brake drum.  Somewhat to my surprise, it went back into reasonable shape, without cracking.  So, a bit more tapping, and it looks quite good.  It will require a bit of filling and filing, and machining, but maybe it is resurrectable.

After a sleep, and fresh look, I relented and took a couple of photos.

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But what about finishing cutting the gear teeth?  It will need a new shaft.   My plan is to machine off the bent shaft, insert a new steel shaft while holding the external circumference of the gear in the lathe chuck.  Might just work.  If the over-gashed tooth looks too odd when I finish cutting the teeth, I will fill the void with bronze or silver and re-machine it.  Watch this space.

 

BRONZE POUR- everything went wrong!

Just to recap, I made the trees and investment powder moulds about 2 weeks ago.

The biggest gears on the Armstrong cannon. Some with cast teeth, and some with blanks for teeth to be cut. And some brackets in red on top.
And the 2nd tree has 6 brackets on top, and another T rex to fill the spare space.

The first problem was that when I was adding the carefully weighed and expensive investment powder to the carefully weighed water, the f***cking scales timed out and shut down. So I had to guess the amount of powder to add. Then mix furiously. Then a briefer than normal degassing. All to be completed in 10 minutes. 10 minutes sounds like a long time. But it is all too short when there is any hick-up at all. (read.. “stuff -up”). #1.

I knew that the scales had a shut down timeout, and following the Chinglish instructions, I thought that I had turned the timeout off. But apparently I had not. After that I ordered some new scales.

Then I had to wait almost 2 weeks for the 15% phosphor copper to arrive.

Yesterday, after installing a new heater element in the melting furnace the day before, I fired up the investment oven and went through the drying, burnout and baking cycles, about 8 hours. And prepared another tree and mould for the next pour, in a few days time.

The melting furnace with its new element took a lot longer than previously to melt the bronze ingots, about double the time. But that was OK. Just had to ring SWMBO to warn her that I would be very late. (Got home about 9pm. She had organised take away.)

I added the 15% phosphor copper in approximately the recommended amount. And poured the first cylinder. But I forgot to wait the recommended 2″. #2.

Then I poured the second mould. And there was not enough melt!!!! #3. I had underestimated the amount of bronze! Those 4 big gears were guzzling the molten bronze! So what to do? Abandon the second cylinder? Or melt another ingot and just pour it on top of the first one after another 30-45″?. Nothing to lose, so I plopped in another bronze ingot, and waited for it to melt. Meanwhile I put the mould half filled with bronze back in the investment oven to keep it warm at 710ºc. Then, for some reason, the electronic controller of the investment oven shut down, and the element stopped heating. #4.

When the extra bronze melted I added bit more phosphor copper and completed the pour into the now substantially cooler mould which was already half filled with bronze which presumably had solidified. I assumed that the join between the 2 pours would be a problem. And it was.

Forgot my camera. Some photos to be inserted here later.

Somewhat surprisingly considering the guessed amount of investment powder at the original mix, and short duration degassing, the first mould was, apart from a few bubbles, completely successful. The second mould, with its 2 pours, was not a total disaster.

Today I sawed apart the trees, removed the bits of sprue and vents, and partly machined the parts. These are the bits.

The toothed gears and non toothed gears are the biggest gears on the cannon. And they include the drum brake, I was unsure whether the cast teeth would be adequate, or whether I would need to cut the teeth. It was not a fair test, in view of the interrupted pour, and the brief degassing. But I will cut the teeth from the blank wheels to the right. The toothed gears were probably the join between the 2 pours and total failure and will be remelted.

Even the blank wheels are not without problems. I did not allow for shrinkage, #5. and the diameter of the wheels is 57.5mm instead of the intended 58mm. So I cannot cut 56 teeth per wheel. I can cut 55 teeth on the smaller diameter. Still pondering that one. Do I repeat the entire exercise with a machining allowance? Or just be satisfied with one tooth less? I have not decided definitely, but am tending towards accepting a slightly smaller tooth count.

But, at least the brackets to the right came out well. This photo was taken after some belt sanding….not perfect, but not bad at all.

Incidentally, the T Rex is quite good. substantially less surface oxidation, and the oxidation layer that was present came off much more easily. Next pour I will add a bit more of the phosphor copper. And I will wait the recommended 2″.

2 steps forward, one step back. A familiar dance.

15% Phosphor Copper-2

It arrived today. Rather uninspiring small grey bits of metal about the size of rice grains.

But how much to add to the melt?

So I searched the net and found this.

Description:
15% Phosphor Copper Shot is use as a deoxidizing agent for copper, brass & bronze alloys. It will also increase fluidity and inhibit gas porosity. The shot we carry is approximately 1/8″ x 1/32″ in size.

Usage:
Melting of brass, bronze and copper should be done quickly in a slightly oxidizing atmosphere. The crucible is removed and surface is skimmed, then phosphor copper shot is added by simply dropping it onto the surface. The reaction is very visible. The metal will become fluid and bright. Allow a minute or two for the reaction to complete, and pour. 

The phosphorus is a reducing agent (deoxidizer). This product must be carefully measured so that enough oxygen is removed, yet a small amount remains to improve fluidity. Too much phosphor can cause the melt to be so fluid that it leaks from the mold and penetrates the sand. A little goes a very long way! 

The primary reason to use the shot is because the molds aren’t filling well or have gas porosity problems. The literature suggests that 1 ounce of 15% copper phosphor shot be added to 100 lbs of metal. A teaspoon of shot weighs about 1 ounce. 

Start with these amounts: 100 Lbs add 1 Tsp. 50 Lbs add 1/2 Tsp. 25 Lbs add 1/4 Tsp. 

For lesser amounts start with about 1 to 4 granules per pound of metal

At that rate the 1kg will last a lifetime.

Metal Casting Research

The video featured in this post is fairly recent, and will probably be of interest only to those who are actively involved in casting, and those who like to keep up with developments.

While aimed mainly at industrial level casters, there are lessons which amateur casters can apply.

Thanks to GSMEE member John Bernoth for sending me the link.

As a very amateur beginner, the video made me aware of how little I know about the subject.

You can watch the video on the small screen here, or find the YouTube link to watch it full screen. The video quality is pretty ordinary, but the message is, I found, very interesting.

ps. waiting for the 15 phosphor copper to arrive by our very slow post before I do any more casting. Still in level 3 lockdown. I am making a negative pressure pouring apparatus, almost finished, but after watching the above video I wonder if I am on the wrong track. Maybe I should be thinking about bottom filling, spinners, and restricting the flow rate.

The heavy plate with the hole is connected to the water chamber on the left. The mold cylinder will sit on a silicone pad which will have a corresponding hole. The hot air will pass through a copper coil in the water chamber to the left, and the cooled air will then go through a tube to the evacuation chamber and then the evacuation pump. The filler and drain plug positions were determined by pre-existing holes in the copper tube.

15 Phosphor-Copper Shot.

Never heard of 15 phosphor-copper?

Neither had I.

T Rex, in bronze.

My bronze castings had been coming out of the investment mould looking like this. I had been expecting to see a wonderful shiny golden bronze colour, and was a bit disappointed in the irregular black coating. But the casting itself was complete, with no voids, and having fine details like fingers, and 3D printing marks showing up clearly. And after laboriously attacking the black coating with Dremel wire brushes, files, sulphuric acid (ineffective), a lot of the black was removed.

This baby T Rex has found a home on my model dredger engine. The variegated skin colouring is reasonably convincing, but was not the shiny bronze colour which I wanted.

Maybe a problem with the LG2 bronze ingot? Something else?

So, I telephoned the supplier, Clingcast Metals, Sydney. Paul answered the phone, and he knew exactly what I was describing. “copper oxidation. Did you add 15 phosphor-copper shot to the charge? (The “charge”, I gather, is the crucible loaded with bronze pieces, for melting?)

“No. What is 15 phosphor-copper shot?”

“Small metal balls. If you add a tiny amount to the charge you will avoid the surface oxidation which you are experiencing, AND it will make the bronze melt thinner and run more freely.”

“Great. Where do I get it.”

“Oh. We have heaps here.”

“Would you post some to me?”

“Sure. How much do you want?”

Quickly thinking….”Maybe a kilogram”.

“That will last you a lifetime. $15, plus postage”.

“Fantastic.” – but I can’t find my credit card. Darn.

Paul. “I will post it. Just pay us when you get around to it.”

So, no more casting sessions until the 15 phosphor-copper shot arrives.

And big kudos to Clingcast Metals.

Meanwhile, I am making up trees and moulds.

Another T Rex, and some cannon parts.
The transparent PLA disks are the biggest gear with brake drum. I have not yet decided whether to cut the teeth on this part. And the red PLA parts are brackets for the cannon chassis.

Also meanwhile, I noted that Banggood have a special on melting furnaces which seem identical to the one for which I paid $425, and I have seen advertised at up to over $500. Banggood are asking $AUD290 + $20 p&p. So I have ordered one, as a spare. If you are interested I suggest that you check out this special, ASAP.

p.s. 2 Sept 2020. The 15% phosphor copper arrived today. I found this info on how much to add. I think that my 1kg will last a lifetime.

Description:
15% Phosphor Copper Shot is use as a deoxidizing agent for copper, brass & bronze alloys. It will also increase fluidity and inhibit gas porosity. The shot we carry is approximately 1/8″ x 1/32″ in size.

Usage:
Melting of brass, bronze and copper should be done quickly in a slightly oxidizing atmosphere. The crucible is removed and surface is skimmed, then phosphor copper shot is added by simply dropping it onto the surface. The reaction is very visible. The metal will become fluid and bright. Allow a minute or two for the reaction to complete, and pour. 

The phosphorus is a reducing agent (deoxidizer). This product must be carefully measured so that enough oxygen is removed, yet a small amount remains to improve fluidity. Too much phosphor can cause the melt to be so fluid that it leaks from the mold and penetrates the sand. A little goes a very long way! 

The primary reason to use the shot is because the molds aren’t filling well or have gas porosity problems. The literature suggests that 1 ounce of 15% copper phosphor shot be added to 100 lbs of metal. A teaspoon of shot weighs about 1 ounce. 

Start with these amounts: 100 Lbs add 1 Tsp. 50 Lbs add 1/2 Tsp. 25 Lbs add 1/4 Tsp. 

For lesser amounts start with about 1 to 4 granules per pound of metal

One to 4 granules per pound of melt! It really will last a lifetime. My crucible will melt a maximum of 3kg/6.6lb.

Spur Gears -1

The model Armstrong cannon has 7 gears, 2 of which are bevel gears, and 5 spur gears, including one quadrant gear.

4 of the original spur gears. These position the carriage on the chassis for loading and firing. There is also a decoupling mechanism on the second shaft. (Portland cannon)

The spur gears will be machined and cut from bronze, brass or steel. I have a set of module 1 cutters, which are close in 1:10 scale to the originals which are close to module 10.

The bevel gears I have made by casting them in bronze, teeth and all, and they are pretty darned good. Not perfect, but they will be hidden from sight in the gear case. They seem to mesh pretty well, but, if they are not up to the job of elevating the barrel I will cut some replacements.

The biggest gear is a spur gear, and it has a brake drum as part of the casting. It is a bit more complicated than a simple cut spur gear. Apart from the brake drum, the gear teeth have flanges at each end of the teeth, which will make them difficult to cut, unless I add the flanges later. I guess that the original was cast, teeth and all.

From below, the biggest gear with the brake drum on the left of the picture. The brake band is a steel band. (Port Fairy cannon)

I have decided to cast this gear also.

You can see the flanges more clearly in this photo. (Port Fairy cannon)
So I have 3D printed casting blanks with teeth and flanges (left) and without teeth and flanges (right). I will cast both, then decide which to use. 58mm diameter, 25mm wide. The prints are colourless PLA. I have had problems with plate adhesion with this PLA.
The bevel gear case. Cast bronze. Some more finishing required.
The cast bevel gears. Since this pic I have machined bores and improved the finish. PLA blanks.
And can you guess what this fingernail size piece is? It will cast in bronze.

Bronze Casting. Can You Bake the Investment Twice??

I found out the answer to this question today, unfortunately.

This is the PLA + wax tree which I wanted to cast. There are 3 bevel gear cases, for the Armstrong model cannon.

There are internal cavities for the bevel gears, holes for the shafts, and external/internal surfaces, quite a complex shape.

Yesterday I mixed the investment, and poured into the flask, around the tree. It was a tight fit in the flask. I had miscalculated the flask diameter, and some parts were probably touching the metal cylinder. So I was not too confident about a good outcome. But I went ahead and commenced the drying out, burning out, and baking cycles. About 7-8 hours altogether.

Then started the bronze melt in the electric melting furnace.

Strange.

The temperature was not rising.

Usually, 1100ºC was reached in 30 minutes or so.

But it remained at 19-20ºc. Ambient temperature.

Penny dropped. Bummer. The Melting furnace was RS.

6 months old, still under warranty. But how long would it take to get parts or replacement from China? Email sent.

And what to do about the already prepared investment flask, happily baking away? So I turned off the investment oven, and let it slowly cool down.

Discussed the situation with Stuart. Probably burnt out the heating coil, but could be the relay or the control unit. Whatever, it will take days/weeks/months to sort out. Bummer.

Stuart: “You can borrow my spare unit”.

Me: “you have a spare melting furnace?”

Stuart: “sure”. “you can borrow it”.

Me: “wonderful, thank you”

So today I wondered if the investment flask could be reheated to 710ºc, and accept the molten bronze. Stuart: “Don’t know. Never done it”.

So today, I reheated the investment flask to 710ºc, over 3-4 hours, held there for an hour, melted some bronze in Stuart’s loan furnace, and poured.

Here is the result.

3 almost perfect gear cases. I have removed the sprues and funnel and most of the investment. Not showing up well in the photo, but I have demonstrated that the investment mold CAN be reheated. I will machine off the unwanted bits and surfaces tomorrow.

Casting with bronze seems a bit more forgiving than with aluminium. And Investment mold, at least with Goldstar Omega Plus, CAN be cooled and reheated without cracking up.

And a replacement heating coil will be sent from China. Maybe I should buy a spare melting furnace.

Japanese Knife

In common with every modeller, woodworker, metalworker, boat builder, surgeon, “hands on” person that I have ever met, I love tools, particularly tools made with thought and care and passion for quality.

And, although I have never been a knife maker, I have been a frequent watcher of “how to” make knife videos. Who knows, maybe I will branch out into that hobby one day.

This post was prompted by my purchase of a new knife. Undoubtedly the sharpest knife I have ever used. At first glance, it has an attractive, basic shape, and I thought, “that will make a good kitchen knife”. It is long and slender, not for chopping sweet potato or pumpkin, but more for fine slicing of tomato, or coriander. (or meat/fish if you are a Neanderthal).

And sharp! It is sharper IMO than a surgeon’s scalpel. It passes the paper held at one edge slicing test with ease. I could shave with it, except with a 8″/200mm blade, that would be a bit terrifying. Even cutting up vegetables is an activity to be approached with caution. A touch on a finger would end up as a trip to the casualty department for stitches.

The knife is Japanese. Of unknown age. Probably handmade.

It was offered to me by GSMEE member Neil, who has a substantial collection. One glance at the photo he sent to me was enough for a “yes please”.

The knife, and its wooden sheath.
Can anyone translate this?
The handle, ferrule and blade are asymmetric. The grip is quite positive. Previously I have rejected asymmetric blades because they tend to deviate sideways while cutting, but this one, for some reason, cuts straight.

The wooden sheath is not Japanese. It was made by Neil, and the blade snicks perfectly into place. The pattern on the sheath is unique, and random. Looks the part, no? Considering the terrifying sharpness of the blade, the sheath is an absolute necessity IMO.

Japanese knives, chisels, saws and other implements are available from Tetsu, Ocean Grove, Victoria, tel 0403 549485. If you want a knife with a fitted wooden sheath (strongly recommended), contact Neil McMeekin at neilmcmeekin@bigpond.com. tel 0491 212 258.

Bronze Tyrannosaurus Rex

Actually, I had some spare space on the tree which I used to make some more small gears, and I had some PLA T. Rex’s, so I added one.

P1074321

And this was the cast result, in bronze.  Yet to be cleaned up, tree bits ground off, and polished..

P1074328

 Again, the gears are close to perfect.  I like bronze.

And the gears have a short length of shaft, printed in PLA and cast in bronze, which I will be able to hold in a chuck for tidying and turning.  Lesson learned.   Think ahead, how the cast part will be machined….

And at our society Zoom meeting, Frank M  asked about the colour of burning Borax.   I could not remember, so took a shot today…

P1074324

I would describe the colour as white-gold, with a touch of green.  Like a volcano.   Maybe I overdid the Borax?

Oh.  And I had a brainwave.  When degassing the investment mix with negative pressure, add some vibration.  I tried applying my sanding machine once, and filled the room with old fine sawdust.  But for this session, I placed the vacuum pump on the vacuum chamber, and could hardly believe the volume of air which came out of the mix.  The best degassing to date.

P1074323

and it takes less bench space.   A no-brainer.  Try it!

 

Soft Jaws

The bronze gears which I cast yesterday were cut off the tree with small bolt cutters, band saw and hack saw.   Then a belt sander to reduce the daggy bits.

P1074316

The gears, and the tree trunk and branches which will be remelted.

P1074317

The faces needed to be flattened in the lathe, but how to hold the rather thin, delicate, irregular gears?

Soft jaws.

Soft jaws made of aluminium, and exactly machined to match the external diameter of gear teeth, so there are multiple contact points, and minimal chance of damaging the teeth.  I made these soft jaws ages ago, for just this sort of job.

P1074318

The soft jaws are machined to exactly fit the workpiece.

The soft jaws may be used multiple times, machined to shape each time.  Very handy in this situation.

P1074319

The larger gears are good.  I silver soldered some extra material on one of them for the shaft, then turned the shaft to size .  But, holding the small pinion gear is more problematic.  I will need to machine a soft jaw with a taper to hold the teeth.  Next session.  I should have anticipated this situation and designed the gear with a shaft to be PLA printed as one piece.

 

 

First Bronze Castings

Bevel gears seem to me to be rather difficult, even with CNC control of X,Y,Z and A axes.  The bevel gears on the model Armstrong cannon are rather small, being 32mm and 14mm outside diameter.

I read Ivan Law’s book on the subject, and I think that I understand the requirements, and I was prepared to try and cut the gears.  But, first, I decided to try to cast them.

That involved…

  1. Using “Gearotic” to design the gears, and save them as an STL file which was able to be imported into the 3D printer.
  2. Made PLA gears with the 3D printer.
  3. Attached the gears to a wax “tree”.

P1074311

3 pinions and 3 gears.  I need 2 of each.  1 spare of each.  Plenty of venting sprues.  And a head of about 70mm.

4. Then mixed the investment, poured it into the flask.  At least that was the intent.  The investment makers specify exactly 40:100 by weight of water:powder.  But the bloody scales switched themselves off while I was adding the powder to the water, so I had to guess the quantity of powder.   This was not looking promising.  First bronze casting pour not off to a good start.

5. Dry the mold flask in the potter’s oven for 2 hours, then 2 hours of burning out the PLA and wax, then 2-3 hours of baking at 750ºc.  A few minutes into the burnout phase, the oven died.   ?heating coil failure, ? control box failure?, ?thermocouple failure,  something else?    So I replaced the control unit and thermocouple (I had a spare of each), but problem persisted.  I rang my expert friend for advice.  “sounds like a broken wire” he says.  Suggested 3 or 4 things to try.  And the 4th suggestion worked!  The oven was working again!  Brilliant!   Thanks Stuart Tankard.  So I restarted the oven at the burnout temperature (400ºc) and continued.  Nothing to lose, after all.

6. Melted a couple of bars of LG2 bronze at 1100ºc in the melting furnace.  Added a pinch of Borax.  Let the investment oven cool to 710ºc for 1 hour to let the core of the mold cool to 710ºc.

7.  Without any great expectations of success, considering the various problems, I poured the molten bronze into the mold flask.  It seemed a bit more viscous and thick than I was expecting.  Oh well.  It is experimental.

8.  When the mold flask had cooled to 150ºc, I plunged into cold water, and flushed out the investment.

THE RESULT….

P1074313

Unbelievable.  No voids.  Hardly any surface bubbles.  ALL teeth intact and complete.  6 good gears!   You can see the head of molten bronze between the funnel and the top gear.  It did not need vacuum or positive pressure.

P1074312

I will turn the faces, bore the shaft holes, and if necessary file the teeth.

Totally delighted with this result.  Beginner’s Luck.

 

 

Trunnion Mounts -3

I did not expect these mounts to require a third day session, and they are still not finished!

I discovered that two of the drilled holes in each bracket were in the wrong position, by approx 1mm.  That is a really bothersome error, because the correct position includes half of the existing hole.

I managed the problem by threading the errant holes, and Loctite gluing in some threaded rod.  Each rod was trimmed flush with the surfaces.   Then drilling the new hole, partly through the Loctited metal patch.  That fix worked well.

P1074281

Threaded rod glued into the errant hole.  Trimmed flush later.  Then redrilled correctly.

 

THE TRUNNION PINS.

The pins hold the trunnion caps in place.  And they took another whole day to make and install.   Ah….  just as well I enjoy all of this.  They are tiny, and I spent at least 50% of the time looking for them on the workshop floor after accidentally dropping them on several occasions.

P1074299

Milling the pin handles from 2mm steel.  The handles ended up at 7mm long.  The holes were drilled before the outlines were cut.  Then the tabs were ground off using my newly made belt sander belt.  The belt lasted 15 minutes before the belt itself tore, with the join still intact!

P1074308

Then some delicate silver soldering of a ring to attach a securing chain later, then the pin shaft itself.  The wire through the ring is just to hold it in position during soldering.

P1074309

And that is one of the 8 pins made.  I will polish them in a gemstone tumbler next session.

P1074310

On the model, the pins are jammed into position with a cam action, after some filing-shaping.  On the original cannon there was a small protrusion on the inner end of the pin shaft, which fitted through a slot in the side of the carriage.  I could not figure out a method of making such a tiny slot (1mm wide x 1mm deep) through 4mm of steel plus 2mm of brass, but the cam action seems effective.    I will attach some chain soon, because I do not wish to make any more of these.  And yes, the pins handles are slightly over-scaled, but I think not outlandishly so.

So, apart from polishing riveting and painting, I think that the trunnion mounts are finished.

Now planning to make the gear train for the carriage positioning on the chassis, and the pinion, quadrant gear, and bevel gears for the barrel elevation.  We are currently in level 3 lockdown for Covid containment, with level 4 looking likely any day, so obtaining brass for the biggest gears is difficult.  I am considering workarounds.  Apparently community anxiety and depression, family violence, and even suicides are mounting.  When I am in the workshop I am in a different world, thank goodness.

 

 

 

 

 

 

 

Making Sanding Belts

This idea is not original.  I spotted it on YouTube.

I have a very nice small bench belt sander  made by Sorby UK.  I don’t use it often, because the Australian made Radius Master is much more versatile and powerful, but occasionally it is the tool of choice.  Problem is the belts.   They are a really odd size.  Not available on ebay, and they are expensive.  So when I saw this method, I decided to try it.

Basically, you buy a roll of relatively inexpensive 50mm wide sanding paper, and make your own belts.   The issue is, the join.

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I have had this roll, and several others, for years, using a few inches at a time.

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I removed the old belt, cut it along its join, and used it as a model to cut some pieces off the roll.  The angle of the cut was 30/60º.  I used Tullen cutters in preference to scissors.

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And this is the method of the join.  Use “Iron On Mending patch”.  Freely and cheaply available on Ebay, and in haberdashery shops.

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I asked SWMBO if she had some spare IRON for my workshop, and this was produced.  Sorry about the confusing ironing board pattern.

Important:   the ends of the cut sandpaper are precisely aligned, and the side edges are lined up against a straight edge.   Then the mending patch, cut a bit oversize, is laid on the join, and the heated iron is applied according to the instructions on the mending patch.  In this case the iron was heated to “cotton” heat (whatever that means) and pressed down for 25 seconds.  Best to use some brown paper underneath, otherwise the patch will glue to the ironing board cover.

Then I tried it.  Click on the arrow to see a short video.

 

So, the test was surprisingly successful.   Later I made another belt, and applied the patch obliquely, at the same angle as the join.  It was MUCH improved, totally removing the noise of the patch running over the workpiece.   I would certainly recommend this modification.

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This patch was applied straight across, but it was a bit noisy and I kept wondering if it would hold.  It stayed intact.  But an oblique patch is better. 

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After some use, the join opened about a millimeter, but remained intact.  I probably should have let it cool totally before using it.  Or maybe the patch fabric in this case was a little stretchy.

I think that this will be a good method, and I will continue to use it.  It is inexpensive.  I got 4 joins per $AUD5 patch.  I suspect that I overdid the size of the patch, and could probably get double the number of joins from this size material.   Try it!

 

 

 

 

Covid 19 Problems

Today, for the first time since I retired 5+ years ago, I wore a face mask.  In my professional life I wore them for 4-6 hours at a stretch, and never thought twice about them.

But in retirement, and with Covid social restrictions, I have not shaved for 6 months.

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And grew quite a respectable beard and mo.

But with the mask on today, because I had passengers in my car, I was obliged to wear a mask.

It was hot, my beard got in the way and was scratchy, and my glasses fogged up.  And there will be at least 6 weeks more of this…..

So I decided the growth had to go…..

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After the dog clippers….

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and then a blade….. 

SWMBO has not commented yet.  Maybe she has not noticed.  I know that she detested the beard.

Trunnion Mounts -2

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

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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.

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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.

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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.

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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.

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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.

Trunnion Mounts -1

On the Armstrong 80 lb RML model cannon, the trunnions are secured to the carriage with  steel brackets riveted to the carriage sides, and the trunnions rotate in a bronze bearing.

3404 trunnion L

The original trunnion on the Port Fairy cannon

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These are the component parts.

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The RSS ready for cutting out the brackets.  And my working drawing, with alterations.

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First the 2mm rivet holes were drilled, then the outlines were CNC milled.  The steel is 2mm thick.

P1074246Tidied the parts with a file and belt sander.

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The brackets sitting on a photo of the original Warrnambool cannon.

The bronze bearing involved some basic lathe work.

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Then the components were silver soldered together.  Delicate work.  I did not want the solder running into some areas, and the join needed to retain a degree of precision.

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After cooling, sulphuric acid soak, and washing, the top half of the bearing was milled off.

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Some filing to make it fit the carriage, then rivet holes drilled with a Dremel while the bracket was clamped in position.

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Bolted in position temporarily.  Tomorrow I will make the top half of the bracket.  The gap between the bracket and the carriage caused by the metal folding will eventually be filled, and invisible.  A millimeter or so will be removed from the width of the bracket and bearing.

I had a bit of milling excitement while cutting out the steel components.   I was using a 6.35mm 4 flute carbide cutter, and when I started the program the machine plunged into the shape at extremely high speed.  When I checked, the feed speed was 60 times higher than I had specified.  Somehow, the units had changed from mm/minute, to mm/SECOND.  Amazingly, the cut was close to perfect with no damage to the workpiece.  But, alas, it wrecked the carbide cutter.

I had recently upgraded the CNC software (Vectric V-Carve Pro) from version 10 to 10.5.  Maybe some of my settings in the program had been changed in the upgrade?  I never use mm/second.  That is a woodworking CNC router unit.

Using a Banggood tool to make spacers

I needed 20 spacers, 2mm thick, 13mm OD, 5mm ID, to finish the carriage axles for the Armstrong model 80pounder RML.

I could have turned some 13mm OD, drilled a 5mm hole, and parted off the spacers in my lathe, but I know from experience, that the pieces never end up exactly the same thickness (in this case, 2mm thick).

So I decided to try a Banggood tool which has sat unused since I bought it many months ago.

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It is a HSS hole cutter.  18mm OD, but the disk removed is 14mm OD, just a bit bigger than I wanted.  2mm thick waste brass plate.

So I cut off 25 disks, from a piece of waste brass, 2mm thick.  The Banggood tool worked well, except that it need swarf picked out after almost every disk.   But it was quick, reasonably accurate, and the central drill bit was 5mm, just what I wanted.

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The disks were slid onto a 5mm capscrew bolt, and nutted down hard.

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The head of the capscrew was held in the lathe chuck, and the tail of the threaded end in a shop made tapered tailstock socket.  And turned to 13mm diameter. 

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About 12 spacers made per run.   Very quickly.  Reasonably accurately.  A bit of tidying to follow.

The Banggood tool worked pretty well.  I will buy some more of these.  They were quite inexpensive.

Today I polished the ends of the trunnions, being careful not to remove the lasered lines and markings.  I used a 200grit sanding pad in a sponge backed sanding disk in my milling machine.   Also worked very well.  I removed about 0.1mm of steel, without destroying the markings.

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Axles for a Cannon Carriage

How fascinating is that for a topic!

Well, I found it interesting.  Maybe says something about me.

My 2 carriages have 20 wheels and 20 axles between them.  Plus the 4 big ones under the chassis’.  I had made the wheels.  The axles required some planning and thought, after all, whatever I did was going to be repeated at least 20 times.

I decided on stainless steel for the axles, and brass for the end caps.  The originals were steel, but they will be painted, so the appearance of the metal is irrelevant.

First steps were to cut up 20 pieces of 5mm stainless steel, 25mm long, and drill 5mm holes in 12.7mm brass rod, and part off 20 pieces 5mm wide.  With a few spares.

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The the brass end caps need to finish 4mm wide, so there was a machining allowance of only 0.5mm on each face.  So the silver soldering of the 2 parts needed to be reasonably precise.

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To assist with keeping the brass disks square to the rods while soldering, I drilled some 5mm holes in an aerated concrete block, exactly 21mm deep.

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Fluxed the mating parts, and silver soldered 5 at a time.  Very quickly.  I could have used Loctite 620, but would have had to wait until it cured before machining.

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A soak in sulphuric acid for a few minutes, then a water rinse.

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Then turned the end cap shape on the Boxford TCL125

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Not quite finished. M2 Holes to be drilled through the end caps, and threaded to the brackets.  I will use the CNC toolpost milling attachment which I made in 2019.  That might warrant a short video.

A short video.  Well, a bit over 5 minutes…

 

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The capscrews are not kosher.  The original cannons had large slot screws.  But will anyone notice?  (idea…  I could fill in the hex hole with JB Weld, and machine a slot?!).  Maybe.

In retrospect I could have done the entire shaping and drilling and milling of the brass end cap using the toolpost mill on the CNC lathe.   Would have been a lot more efficient.

Recovering from Friction Welding

Back to the model Armstrong cannon carriage this afternoon, and fitting 2 internal transoms, which provide rigidity to the carriage.

The transoms had been laser cut some months ago.  I cut the floor from 2.8mm stainless steel.

Each transom is attached to the sides and floor by angle iron, 2mm thick.  In the original cannons the angle iron was mitred at the corners, and for this model “A” carriage I decided to try to replicate the mitres.

The angle iron was again bandsawn from RSS tube and milled to 10x10mm.  I used the following setup to form the 45º angles…

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This is the Eccentric Engineering tool sharpening arm, set up to 45º on my RadiusMaster belt sander, about to form mitre angles on the angle iron resting to the right.

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The Angle iron pieces were glued to their respective transoms, and 2mm holes drilled.  Bolts progressively inserted.  The lengths and cutouts will be trimmed later.

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Then milled and filed the corners until the parts fitted neatly into the carriage.  Rivets will be inserted later.

 

…and for your interest/amusement, depending on your UFO opinion…  Listen to the information, and try to ignore the appearance of the narrator.

 

….and do I think that UFO’s are real?    I would say that my “belief” has risen from 95% to 99% YES.   One of my readers, with whom I have spoken directly, and for whom I have no doubts about personal veracity, has seen one at close quarters.  Do I think that they are of non human origin?  A bit less positive about that one, but it does seem more likely than not.  Waiting to see if and what NYT does publish.