Author Topic: Un-spiking a cannon by spark erosion (Read 1564 times)

Squire Robin · « **on:** March 03, 2006, 12:18:06 PM »

This is about as exciting as watching paint dry. But if you'd like to share in the tedium here's a movie of the EDM making one of it's occasional up/down cycles to help clear the gunge. Where's the yawn Emoticon when you need it?... :-D

Movie 2.8 Meg

3 hours today and I penetrated another half inch, can't be much further to go. Can there??? :shock:

One thing I have discovered, if you ever build an EDM machine for despiking, include a fine adjustment to tilt and align the electrode. It takes forever trying to do it with a hammer :roll:

best regards

Squire Robin

GGaskill · « **Reply #1 on:** March 03, 2006, 02:08:53 PM »

Cute. Are you going to publish the plans for the EDM? What are you using for the fluid?

Squire Robin · « **Reply #2 on:** March 03, 2006, 02:32:01 PM »

I would publish the plans if they were worth publishing, but there are a few bugs left in it. If I was making it again I'd do it differently but experience is that thing you get just after you needed it most.

I'm using kerosene

best regards

Squire Robin

NONYA · « **Reply #3 on:** March 03, 2006, 04:15:43 PM »

educate the ignorant,what are you trying to do? :?

Cat Whisperer · « **Reply #4 on:** March 03, 2006, 05:24:25 PM »

Quote from: NONYA

educate the ignorant,what are you trying to do? :?

The cannon in question has been 'spiked' - a process of driving a spike into the touch hole and bending the tip on the inside in order to render the cannon inoperable.

The process Squire Robin is using is called EDM - electronic discharge machine - used to remove metal under the cover of a fluid which clears the material that is removed by the action of the spark - the flow of electrons from the metal to the contact.

A more thorough explanation and plans for building an EDM machine are here:

http://cscott.net/Projects/FabClass/final/edesign1.html

Squire Robin · « **Reply #5 on:** March 04, 2006, 12:04:51 AM »

I only got another 1/4" today and then the silicone rubber pump element split and I have to mail order a replacement, so no more cutting until Tuesday - grumble, moan, complain, blooming modern technology :cry:

reddog · « **Reply #6 on:** March 04, 2006, 05:16:33 AM »

Was just wondering, How did the spike the spike get in there?

Squire Robin · « **Reply #7 on:** March 04, 2006, 06:22:41 AM »

The cannon were taken from a Reed Shipping Line schooner when it became too dangerous to sail the South China Seas because of the outbreak of WW1. They were put on another schooner parked at Newquay and used as a tourist attraction.

When that was set on fire by vandals the cannon were returned to the son of the shipping line owner.

His son test fired one with a load of golf balls and had to light it from the front because it was spiked. I bought them off his son.

I'm presuming the spikes were inserted before they went on public display, circa 1914, and they did a very good job putting them in :eek:

best regards

Squire Robin

NONYA · « **Reply #8 on:** March 04, 2006, 08:02:29 AM »

cant they just be drilled out?

Squire Robin · « **Reply #9 on:** March 04, 2006, 08:22:17 AM »

That would not be easy :grin:

Double D · « **Reply #10 on:** March 04, 2006, 11:06:31 AM »

Robin thing positive, when you get this one done you only have one more to go.

Nonya Robin posted about these guns some time back. The material used to spike the guns was harder than the guns barrel. He tried drilling then ran into the hard material. Drilling at that point migh have resulted in the drill drifting and damaging the vent hole

Powder keg · « **Reply #11 on:** March 04, 2006, 02:56:17 PM »

Were you able to determine how deep you have to go?

Cannonmaker · « **Reply #12 on:** March 04, 2006, 08:27:28 PM »

Robin, what material are the tubes made of? Are they Bronze? This is just a thought, if they are bronze, which is somewhat non corrosive and they used a carbon steel to spike the gun. if this is the case you may try using HCl, Hydrocloric acid, placed in the vent hole to disolve the metal used to spike the piece. it's just a thought, works great on taps.
Once a friend broght to the shop a Titainum shaft from his snowmachine which he tried to drill and tap. Ti gauls real easey and he broke the tap. I won the bet--- got the broken tap out. HCl did the trick.

Squire Robin · « **Reply #13 on:** March 07, 2006, 09:48:49 AM »

Hi

The cannon are iron and obviously I can't calculate the depth because I just finished burning the tool in to the hilt, took it out, measured it and by my calculations I should be 1/16" in to the bore :shock:

The tip was just about gone, I'll make a new, longer tool and start burning again tomorrow.

ShadowMover · « **Reply #14 on:** March 07, 2006, 03:33:56 PM »

They didn't pour some molten lead down the barrel to fill in the space behind the touch hole did they?