Cannon construction

[Bill Baldock]

This cannon is on Angel Island in San Francisco Bay. The plaque says it is 18th century English, found in the Caribbean.

It looks to me like it's composite construction - wrought iron over a cast iron body.

Is this type of construction (or corrosion effect) something anyone knows about?

http://i7.photobucket.com/albums/y287/WRussell/DSC21865sml.jpg[/img]]

[Ed Wenger]

Bill...

I'll preface this by saying I'm certainly no expert on cannons...  If I remember correctly (from folks who are very knowledgeable) this type of construction, especially with bigger guns, was not unusual.  The cast iron was not deemed strong enough by itself to handle the 1 lb+ charges and an all wrought iron constructed gun started to get pretty heavy.  The result was a gun constructed like you observed, cast iron wrapped in wrought iron. 

                  Ed

[LynnC]

Honestly, I think what you are seeing is major corrosion having flaked away down to the remaining solid cast iron.

Cannon were generaly reinforced with wrought iron bands shrunk on at the breech and would resemble the CW US Parrot rifled gun.  The Confederates banded a lot of guns, both foreign and domestic, often rifling them.

From the photos, I don't see any evidence of banding.

Nice lawn ornament though

[TPH]

I think Lynn is right, solid cast iron, standard for the time, with no wrought iron used.

[Dphariss]

Wrought iron would show the tell tale striations/inclusions that run down the length of the bar.

Dan

[ironwolf]

  Corosion for sure.  The layers of "scale"  on the outside is the iron already converted to ferous oxide.  The inner is still converting, or as we say, rusting away.  Having worked around ship yards and salt water-cooled power plants, it's a sight I've seen all to often.

  Kevin