doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Question For Chuck or Rocketman (Hoop Stress)

Actually, the tested strength of the wire is 160,000 psi. Although Roebling had requested 180,000 psi, he got American suppliers who cheated on the quality. The safety factor allowed the inclusion.And it still stands. Many ,if not most old boilers,failed not because of jacket strength, but because of lack of water. If water is then reintroduced, it touches red-hot iron.There is immediate decomposition to hydrogen and oxygen.The resultant recomposition will blow the tube or the boiler.

Regarding Williams last post I have heard the vast majority of bursts on the old agricultural traction engines (steam) was from low water. If the area over the fire-box known as the Crown Sheet was allowed to get "Dry" as William said it soon became red hot & lost the strength to hold the pressure which caused it to blow down into the fire box, & of course the engineer was right there behind the firebox, possibly even with the door open feeding fuel at the time. A few years back an engine blew at a major steam threshers reunion & I believe this was decided to be the cause.

Yeah that Haigh guy sounded like a used car salesman trying to pull the wool over on Emmy. 'had to add another 250 strands from what I read. 160ksi is nothing to sneeze at, certainly 180 would have been pretty special. Pretty hard stuff in the day, especially for the use. They must have got it right to stand the test of time, not only for strength but must have kept the loading very low to avoid fatigue all these years. Of course, today 160ksi or even 180 is fairly medium strength stuff and can be obtained with a medium carbon steel with something like .40 carbon.

On the boilers, I saw a "Dirty Jobs" episode where they were cleaning a ship boiler for it's annual crack inspection required by the Coast Guard.

Perhaps 160k does not impress.But,that was 120 years ago. Even now it has not gone to 300k for bridge work. The boiler does not have to be dry.Even the most itty bitty bubble that occurs and does not take the heat away will allow ultra heat with the resulting damage to the tube.The big ones run at 1000F+ and up to 3500psi for the steam. BTY,since drawn wire was so strong,that is why there was serious consideration to wire bound big guns.

Bill,
You underestimate my surprise. Although, thinking about it, this was at the height of the industrial revolution when most of the fundamental modern steel processes were developed.

That work the Zircon embarked on was to provide a looking glass back into the steel making of the early 20th century. I suspect he'll find pretty sophisticated alloys similar to modern stuff. Modern (contemporary) shotguns really haven't used much in the way of the very modern metals for the most part. I think purity is where there's been a lot of work, although we find very small inclusions at failure initiations in very expensive Vac-Arc alloys like 300M and HiTuff.