HMS Bellona 1760 by SJSoane - Scale 1:64 - English 74 gun, as designed

[albert]

Great beautiful work, very very nice.

[Hubac's Historian]

That looks dynomite, Mark!

[Stuntflyer]

Very nicely done, Mark!

 

Mike

[dvm27]

No more getting sick, Mark - we've been waiting for this update. Looks marvellous! Have you considered making a cutter that bores the hole while shaping the muzzle swell ? I've seen it in Frolich's book and perhaps elswhere on this site.

[druxey]

And there you go! Repeat...repeat...and repeat. Well done, Mark. To blacken the metal you will need pewter black - copper blackening agents don't work well.

[SJSoane]

Thank you, albert, Marc, Mike, Greg and druxey, for your words of support and encouragement. This cannon project seems to have been an exceptionally long time in development this winter, and I haven't even begun mass production. Your continuing support really helped keep me going when the project got a little bogged down at times.

 

Thanks again to Chuck for providing those exceptional king's cyphers. They look great in the casting, and I concede that it was beyond my ability to create them after numerous failed efforts. I may still try photo-etching when the sun comes back this summer, just to see if it was a problem with using an incandescent bulb instead of the sun...

 

Greg, I haven't seen the idea of a cutter; intriguing. Do you recall where you saw it? I am reworking the split collar for clamping the barrel in the lathe, because it is still not quite centering the drill. I will show experiments as I work on it.

 

druxey, I last used Jax's Pewter blacking on earlier experiments, which seemed to work well. But I have noticed that some cannon treated this way a few years ago lost the blacking in a few places like edges on the face of the muzzle. Do you have thoughts about how to clean the barrels for Jax's to work better? And my Jax's is a few years old; do I need to get a fresh supply?

 

Thanks again, everyone,

 

Mark

 

 

 

Edited March 6, 2019 by SJSoane

[dvm27]

Sent you a PM with info Mark. Unsure about copyright protocol in this instance.

[druxey]

There may be traces of RTV deposit or talc on the surface of the casting, Mark. I cleaned the surfaces of my castings with isopropanol, then a 400 grit 3M/Scotch-Brite abrasive 'spider' wheel (radial bristle disc) run at slow speed in my rotary tool. I can't speak for the shelf life of Jax chemicals. Perhaps the manufacturer has specs on that.

[rlb]

Mark,

 

Congratulations on the initial casting, it looks great!   I have been silently following your cannon saga (and entire build since you've been on the site).  

 

Ron

[mtaylor]

Sweet looking cannon, Mark.   Very nicely done.  Well worth the effort, me thinks.

[SJSoane]

Not much new to report; starting to work my way through 74.

 

I have noticed, though, that I am sometimes having trouble with the registration of the two halves, leading to mal-formed cannon. The rubber moulds are no longer as sticky as they were when new. I think this allows them to slide around a little relative to each other. I have to be very careful to ensure that the mould sides are aligned when clamping them between the pieces of wood with rubber bands.

 

We will see if the 32# and the 24# moulds are durable enough to cast 28 good cannon each...

 

Mark

[Landrotten Highlander]

I have no experience with rubber moulds, but have worked in the manufacturing industry for over 2 decades.

Is it possible to drill a minimum of 2 holes in the corners to which you would then insert a dowel?  Have it fixed in the bottom half of your mould, then the top half will slide over the pin.  This should increase repeatability of alignment (this method is used fron injection moulding to hot forging).

[SJSoane]

LH, that is a very good idea. I could clamp the master in the mould to position each side to the other, and drill through both. I'll try it on a reject mould and see how that works. Thanks!

 

Mark

[SJSoane]

Hi LH, a quick question. Do I assume correctly that the pins should be as close as possible to the cannon shape in the mould? I have a feeling that the rubber stretches a tiny bit across its width, and so it wants to be anchored as close to the cannon shape as possible. Or is it normal practice to keep these pins at the outer edge of the mould box itself? I suppose the only danger is getting too close to the cannon shape, and risking a tear.

 

Mark

 

 

[Landrotten Highlander]

I think somewhere in two opposing corners should be sufficient. 

Any difference in stretching of the rubber will be due to differences in tightening the two halves. No need to go too close to your cavity, as then any stretching of rubber will lead to deformation of the cavity itself (so you could have a banana-shaped gun, instead of one where the two halves are slightly misaligned).

The purpose of these pins is to align the moud halves at the same spot every time, then try to keep the same format of tightening for all subsequent pours.

 

Personally, if your test is successful and you wish to use this technique on your good one I would take the brass template gun and place it in the mould cavities. Then tighten the two halves using a spare bit of wood so you can drill the necessary holes through this wood (I think two is a minimum, but no more than one hole in each corner).  Then for pouring your material, only use pins that are slightly shorte than the overall thickness of your mould so you do not risk misaligning the rubber by forcing the wood over the pins.

 

Again, I have no personal experience with this technique, but what I describe above is consistent with my observations and training in Industry relating to injection moulding and hot forming - the guiding pins are at the edge of the mould, and only so close as so not to cause undue deformation of the mould block - which requires both complex calculations and extensive experience when designing dies for hot forging (even though the deformation is within tight tolerances, it does happen).

Edited March 11, 2019 by Landrotten Highlander
additional thoughts

[SJSoane]

Thanks, LH, this make sense. It sounds like you have a wealth of experience in this fascinating technology!

 

Mark

[druxey]

This is one reason I use a full clam-shell outer plaster jacket: pressure on the mold will be evenly distributed. Clamping from two sides will lead to misalignment and deformation of the RTV mold.

Edited March 11, 2019 by druxey

[Landrotten Highlander]

4 minutes ago, SJSoane said:

Thanks, LH, this make sense. It sounds like you have a wealth of experience in this fascinating technology!

 

Mark

No problem.  It is true I have plenty of industry experience but in no way do I consider myself an expert.  As a matter of fact, to increase my knowledge I am currently enrolled in an MSc Advanced Manufacturing: Technology and Systems.  It is amazing the quantum leaps that have happened since I left college, including cold forging turbine shafts from a small billet - the machine treats the steel *** if it were plasticine (and I hope I do not need to expand on the theoretical knowledge behind this technology, it is worthy of an undergraduate course on its own)

[SJSoane]

Ah, druxey, I see that now. My failed plaster pointed me in another direction, but I may be back to this if I cannot get the pin idea to work.

 

Mark

[michael mott]

Mark looks like you are on your way. I would agree with Druxey, and as LH suggested put the brass master back in before making the jacket. If you know someone in the medical profession perhaps get a line on the same plaster that is used for plaster casts, which is basically the same stuff that Evergreen use for the landscape work make the plaster jacket the same way that you made the mold only make it so that it is 90 degrees and when it is slipped over the two halves it automatically holds them together.

 

Michael

[mtaylor]

You can buy plaster casting material online.   Or check with prosthetics companies and orthopedists.  

[druxey]

Dental stone sets harder than regular Plaster of Paris. Perhaps enquire of your dentist? 

[AON]

sorry to flog that dead horse ... but I just stumbled upon this

Fair American 1780

18th Century War Brig

Pg 24 figure 20

by Eric A R Ronndeag Jr.

 

Not certain what keeps it from falling off in rough seas or the heat of battle.

Edited March 12, 2019 by AON

[druxey]

The drawing above is accurate - to a point. While the outhaul correctly shows a double/single block arrangement, that was only used for guns of larger calibre. Smaller ones were rigged single/single. The breeching is shown secured to the ringbolts using seizings. This was correct for the early 18th century. However - about mid-century I think - the ends were half-hitched and secured by a single seizing instead.

[SJSoane]

hi everyone,

 

 

Alan, thanks for the image.  It seems that there are three likely ways in which the breech rope deals with the button on the cascable; the one you have shown, the idea of a cut splice, and the one Siggi showed in the cross section model with it simply lying over the top. Once I start installing the cannon, I think I will make a final decision about which looks the best or makes the most sense.

 

I can see the value of the plaster jacket now. As the moulds break in, they do not register as precisely as when they were new.

 

I once used Hydrocal art plaster a few years ago and it worked well for this. But when I tried it again recently, it was very lumpy and it set up before I could pour. So I threw that away.

 

My choices are more limited in my new little town, primarily plaster of paris for fixing drywall patches.

 

Is there a reason why I need to order dental plaster for this jacket? Does the hardness matter?

 

Mark

[michael mott]

Mark if you can only get Plaster of Paris, in my experience you can mix it in small batches and soak strips of J cloth or cheese cloth to add to the strength. just build up a few layers it will take longer but will give you the strength and integrity you need. and wait afterward until it is completely dry before using it for its intended purpose.

 

Michael 

[druxey]

Yes! Completely dry. Otherwise water content will turn to rapidly steam with heat....

[SJSoane]

Last time, I built a foamcore box, lifted the rubber mould half-way up off the base by two cardboard legs, and then poured liquid plaster halfway up. The cardboard legs were then encased in the plaster. I then flipped and poured the other half. It worked great the first time a few years ago, but failed in my recent effort when the plaster set too fast to pour.

 

So if I can only get wall repair plaster locally,  it would work better to build it up like a broken bone cast, with soaked cheese cloth? I assume this is so I don't have to worry about it getting too thick too quickly to pour.

 

Mark

[AON]

Okay... I admit I have never cast anything for models.  Industrially we used sand.  Yes it was a special casting resin but it had no "give".  It was solid.

 

What if you built two boxes.  One as a skin for the mould.  The other twice as large.  Put a couple inches of sand (clean dry beach sand) on the floor of the second.  Put your mould in the first box then put the first box centered in the second and on top of the bed of sand.  Then pack sand all around the first but inside the second.  These could be reused over and over again plus any spillage is on the sand.

 

Just a thought.

Edited March 14, 2019 by AON
Mold vs mould

[AON]

I should have mentioned the mould skin box would have the alignment pins!

Edited March 14, 2019 by AON