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25th June 2017, 09:06 PM #1GOLD MEMBER
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W.I.P. Making a pattern for a cannon.
Got a rather unusual job on at the moment which will probably take some time to finish for various reasons.
A bloke dropped off a cannon that he has on loan for a short time that he wants to replicate. He also wants to be able to actually fire cannon balls from it.
It is my job to make a pattern for it so that he can get a foundry to cast it in iron.
Here is a picture of the cannon, it is a metre long and 162mm at its largest diameter. It is also somewhat rough in it's casting and quite heavy.
DSCF6041.jpg
First step is to measure the thing up as accurately as possible. I have chocked it up a bit so that the centre of each end is parallel to the flat surface it sits on, just to make measuring it a bit easier.
DSCF6055.jpg
The measurements are then used to draw a layout. Which is basically a drawing on a bit of mdf of the pattern that will be made. When casting metals, they all shrink or contract somewhat depending on metal type, from molten to solid as they cool down. This has to be taken into account and allowed for on the layout if the final casting is to be exactly the same size as the sample cannon.
Cast iron has a shrinkage rate of 1%. So if the pattern was made at 1 metre long then the casting would end up 990mm long if no allowance was made. Same with all the other measurements respectively.
This is where a "contraction rule" comes in handy. Following picture shows a contraction rule side by side with a normal rule. You can see that over 500mm the contraction rule is 5mm longer and all the other increments are the same percentage longer.
DSCF6044.jpg
This contraction rule is double sided and has 4 different contraction rates on it. 1/100, 1/30,1/50 and 1/70 for various metals. I have put a red line on the 1/100 scale just to avoid accidentally using the wrong scale when drawing down the layout.
Here is a picture of the layout. It also has drawn on it the cannons "trunnions" (the round bits sticking out from the sides that hold the cannon in the trolley it will eventually sit in). Showing both profile and plan view.
The pattern will be made in two halves so that it can be molded in sand with ease at the foundry.
DSCF6053.jpg
That is about all I can do for now. I now have the layout and the original cannon can go back to wherever it came from.
The bore of the final cannon will not be machined out later once cast in iron. It will have a special grade of steel bore/pipe cast into it that the client has on order and may be some weeks away. Minor alterations/additions to the layout will be required once this insert arrives.
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25th June 2017, 11:10 PM #2GOLD MEMBER
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Are you a pattern maker by trade, or one of the Jack of All, Master of None type, like most of us. Just wondering as how you found out this information?
KrynTo grow old is mandatory, growing up is optional.
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25th June 2017, 11:25 PM #3GOLD MEMBER
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Yes I am one by trade.
Rarely do much of it these days but you never forget.
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26th June 2017, 08:14 AM #4GOLD MEMBER
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Hi artful bodgere,
It is nice to pick up the occasional job that requires the skills you learned as you're trade and as you say you don't forget I also get the odd job for a pattern now and then and it is enjoyable to draw back on those skills we (pattern makers) are getting thin on the ground these days unfortunately as with a lot of specialist trades machine technology is taking over from hand skills.
Regards Rod.Rod Gilbert.
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26th June 2017, 12:47 PM #5
Is it legal to make a cannon? If he intends to fire it he has to have a special permit. It is a firearm. Not my concern but I am interested because, well...who doesn't want a working cannon?
Those were the droids I was looking for.
https://autoblastgates.com.au
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26th June 2017, 01:09 PM #6GOLD MEMBER
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In Victoria you only need a Category B shooters licence to own and use a black powder cannon. Don't know how you can satisfy the "Need to have" criteria.
Don't know the rules in Tassy.
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26th June 2017, 02:07 PM #7GOLD MEMBER
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That did cross my mind so I asked the client if it was legal to own such a thing.
He said that it was legal and all you needed was a license that had on it provision for a muzzle loading firearm. Not sure what the storage requirements are though.
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26th June 2017, 02:15 PM #8GOLD MEMBER
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BTW in Vic you need a B licence just to have it in your possession. Without one it will be confiscated and you will be charged so return it quick.
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26th June 2017, 06:06 PM #9
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26th June 2017, 06:13 PM #10
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26th June 2017, 06:45 PM #11
yes, you need the correct category Firearm Licence to own and use a cannon.
but more importantly, you also need the "correct" licence to make one. However, I doubt if making the wooden mold counts as making a firearm.
What I don't know is if the bore of a cannon is cast, or drilled out after casting. I have a vague recollection it is the latter.
Also, I'm really interested in seeing how the pattern for the crest will be made and fitted inside the "barrel" mold.regards from Alberta, Canada
ian
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26th June 2017, 07:01 PM #12GOLD MEMBER
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I do have a firearms license however I hope that is not going to be an issue making the pattern. The client has other cannons too and has told me he is licensed to have such things.
The bore of the cannon is going to be some sort of special steam-pipe material that will be fitted in the sand mold and have the cast iron poured around it. In other words it will be a type of insert that is cast into the final piece. The client showed me a bunch of pictures showing how this has been successfully done before.
The crest is out of my hands, client said that he has got someone else working on this (I think he said in epoxy resin). Will be surprised if it fits like a glove as the bloke making the crest has not seen the pattern.
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26th June 2017, 07:20 PM #13GOLD MEMBER
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Each State has different gun laws. All States have laws regarding cannons, some rather vague. If the OP does not have a firearms licence, they should not be in possession of any form of firearm requiring licence or registration.
To be in possession of an unregistered firearm or without an appropriate licence for that firearm
is in breach of the law. It matters not for what purpose you are in possession it is still illegal.
The cannon, if not deactivated, should be in the hands of an appropriate licenced individual or a licenced dealer.
If the cannon has been deactivated (barrel permanently plugged) it is no longer classified as a firearm and is just another lump of metal.
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26th June 2017, 07:28 PM #14GOLD MEMBER
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Didn't really want this to turn into a legal debate regarding firearms.
Client assured me he is doing nothing wrong.
As for a pattern made from timber. You could hardly call that a dangerous implement.
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26th June 2017, 08:26 PM #15
Hi Artful
There are a pair of wooden cannons beside the flag pole at the Derwent Sailing Squadron in Sandy Bay. Few realise that they are not genuine, but were turned from salvaged jetty piles.
Wooden need a license for a wooden cannon !
Fair Winds
Graeme
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