I was ask to look into a problem with a small antique signal cannon, someone had run a ball bearing down the bore and it stuck about two thirds in. Its a 7/8 bore and the ball is 9 inches from the muzzle.. I have determined that there is no powder and have filled it with Krolls oil on both ends and warmed it up with a heat gun. The problem is that the ball has rusted in, air pressure won't move it. I am hoping to pick your collective brain and figure out how to move the dang thing. I do need to be careful as it has some value.
Cannon help
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Two options come to mind.
1. If it has a screw in nipple for percussion caps. They usually can be fitted with a grease fitting then pumped full of grease and pushing the ball out.
2. I f it has a touch hole fill the rear part of the barrel with water and freeze it.
Bob
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Neglected to add it is cast iron barrel. It has a nipple but has grown in to the casting and would cause too much damage to remove. The combustion chamber is fouled with old powder and after flooding it with oil would be hard to get enough water to move it. I was thinking of machining a piece to match the diameter and trying epoxy to glue on a shaft and perhaps assist in breaking it loose but not sure what adhesive would hold it .
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make a barely loose-fitting bushing, then use a carbide drill, probably a die drill, to drill thru the ball bearing with the bushing as a guide. Then, it may be possible to hook it and pull it out. Possibly cut a split in the end of a rod the size of the hole, put a wedge in loosely (maybe using some rubber cement, or the like), run the rod and wedge in far enough to push the wedge in and separate the split, then pull it back so it jams in the hole. Pull hard, possibly with a slide hammer arrangement.
Obviously an extension shaft is needed to reach down the 9", die drills are longer, but not that long.CNC machines only go through the motions.
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Easy. First, use Evap-o-rust or something similar to remove any rust in the bore.
Second, heat the barrel to 200-ish degrees, using something like a weed burner, to warm it rapidly without transferring too much heat to the ball bearing.
Third, strike it muzzle first on the ground, protected by a chunk of hardwood or even aluminum.
Might take a couple of tries, but unless the ball bearing was hammered in, it's only a light press fit at the moment. Removing any rust first removes any tight spots. The barrel is very likely slightly tapered, so once the ball starts to move, it should come right out.
Doc.Doc's Machine. (Probably not what you expect.)
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I would clean the oil out using Gunk or acetone or?? and then use phosphoric acid to remove the rust. If the ball isn't air tight, a fitting could be made to go over the nipple and epoxied in place so those liquids could be injected behind the ball. I like the carbide drill/bushing idea next, once the bore is better.
Here's another wild idea; fit the end of a heavy copper rod or thick tube with a pointed section of electrode carbon, wrap the tube well in Kaowool, insert it to where it's just touching the ball, and run some DC- current through it. Only problem is knowing how much & when to stop...and which way to orient the cannon. Base up or down? Might be good as a last resort, or just to anneal the ball.
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I wouldn't add water and freeze. I'm afraid it might crack the cast iron barrel. If it's a signal cannon, the barrel wouldn't need to be designed to withstand particularly high pressure.
I think your best bet is phosphoric acid to get rid of the rust, then try doc's suggestion of quickly heating the barrel then whacking the end of the barrel. If you cam give trhe barrel sharp blows, the inertia of the bearing will tend to break it loose.
The coefficient of expansion of cast iron is less than that of steel, so uniformly heating the whole thing won't make the ball loose. It might break the bond between the barrel and the ball though, then some time in a freezer might make it loose. I'd heat and cool slowly though, for large temperature changes.----------
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