Happily Using Technology
by John
Yep. To make my models I use a computer for drawing, making lists, ordering fasteners and materials and tools on Ebay and from suppliers, driving CNC 3D printer, driving CNC machining tools. And laser marking parts. I also do a lot of traditional machining, hand filing and sanding.
The cannon barrel will elevate to 30º, and depress to 5º for firing, although in practice deviations from a degree or two from 0º were rare. Plus there is an extra mark for 17º depression, which was the reloading angle. The numbers which the laser marked are only 0.6mm high. Hard to see with the naked eye. But in scale.
Lasering the tiny marks and numbers took 2 seconds per pass. That is, 2 seconds to make all of the marks and all of the numbers. After some experimenting, we settled on 50 passes. Which was still less than 2 minutes per part.
Click on the following frame to see the video…
How fantastic is that????
So quick, precise and clear. Yep. I am quite happy to employ any new technology which is available to me.
Then today I made the fittings to secure the recoil tube, and drilled and tapped the 8BA fasteners.
The recoil tube is a commercially available gas strut. It was so close to my 1:10 scale dimensions that I decided to cheat, and use it.
I drilled a 1mm hole in the gas tube to release the gas and oil, turned and re-threaded the front end of the piston rod to 6mm, and made the brass supports and end cap. I released the gas because it was too stiff for the model. Even without the compressed gas the strut has some “shock absorbing” activity, and I am quite happy with the decision.
johnsmachines 
Hi John
That’s a beautiful job you have done there, I love it.
I am also trying to make a 7 inch RML cannon that I will start to produce soon. You can see my 3d model on the model engineer forum by searching for RML cannon. I have also made a 10 inch mortar that is on the same site as well. But the reason I’m dropping you a line is because I am at the stage of connecting the gas ram to the back of a dwarf A pivot. I can’t see how this attaches to the back of the slide as it isn’t normally shown in any photos. Is there any chance you have a photo of an actual slide as there aren’t any around where I live. I hope you might be able to help. My email is bufferbrown@btinternet.com Regards Rich
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Hi Richard, the only gas rams which I know of are those on the 6.3″ Armstrong RML’s which you have probably seen in my earlier posts. There are some larger bore RML’s in my area (southern Victoria) with Elsworth mechanisms, but that is of no use to you. I will let you know if I find anything. I assume that you have searched Google Images. Where are you located?
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John
I am in the UK and there are none near me at all. The CAD model I have come up with has been made from the photos I have seen on google images and a few scale drawings that I have. The 7″ Dwarf A pivot shows a gas ram attached to the back of the slide but unfortunately I cant find any images where someone has a close up of this bit. Quite a bit can be inferred from looking at all the pictures and the 2 drawings I have but its just a shame all the pictures are from similar views. But yes if you do see one when your out and about a few detail shots would be superb.
One other thing, I want to look at all your lost wax stuff and look through the entire build again but I’m finding it very difficult to navigate round this site. The only thing I seem to be able to do is use the previous and next post buttons, am I missing something here? There must be an easier way to get around your posts. In fact normally when I search google images I see another image that is yours and by following the image link it takes me to another whole bit of your blog that I’ve never seen. It does baffle me!
By the way I have just started using an Elegoo Mars Pro 3d resin printer to make patterns for some of the parts. You ought to look at these as they produce absolutely amazing prints with a perfect finish it doesn’t even compare to a filament printer, not expensive either.
Regards
Rich
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Navigating the site baffles me too Rich. I use the search button, using key words, but I am unsure if my readers have access to that. I presume that you have seen the “older posts” button at the bottom of the screen when you have backed up about 5-6 posts? That will get you another 5-6 posts. The posts go back 7 years, and there are more than 800 of them.
I will look at the Mars Pro 3d printer, thank you for the suggestion. John
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