In my 1927 Loco & Car cyclopedia I see a type of flexible stay bolt, that seems very rare today, it was referred to as an Pitkin "Articulated" stay bolt. It was sold by ALCO. This Pitkin is basically a two ended version of the ball crown stay bolt, it has the ball heads on both ends.

I have also seen another example of a fully articulated stay bolt that was two rigid stay bolt ends connected by a chain link in the middle.

Would these fully flexible stay bolts have a place boilers that have with wavy side sheets and boilers that break the stays on their flat sides from too much differential expansion between the side sheets?

It would seem that the decreased rigidity of the articulated stay bolts, would solve the wavy side sheet issue (to some degree) and broken stay bolts, if you put the flexibility in the right locations.

Another ad.

Loco 112 and others;
One of the struggles with Northwest Staybolt Co. over the 25 years that I was in business was how to make a product that complied with the A. S. M. E. Boiler Code and was also affordable. Just a note to some of you theoreticians, MONEY IS AN OBJECT!!!. Very few if any of the boiler repair or rebuild projects that NWSB supported over the years had an unlimited budget. I have looked at the pictures of some of the "linked" flexible staybolts, and shudder to think of the manufacturing methods needed an the costs involved to replicate them. All this while operating out of a 1000 square foot shop!! I think one of the reasons these type of products did not find widespread use is even in the day, costs were a factor, even for the big outfits. How many of you locomotive oprators struggle to pay for a $45.00 flexible staybolt? Hey, we can make a better whizbang bolt for only $750.00 each.....How many do you want?....Cash in advance.
Nathan

Here in the US was the Jacobs Schupert firebox. It used stay sheets instead of stay bolts. You could boil one dry without fear of an explosion. The ATSF was a big user of this type of firebox for a while.

Yes, and as soon as it had a few miles on it, it wept and leaked from all those riveted joints between the sections... and it had a fearsome mass for its available heating surface... and would you want to have to clean or descale it? ...

That said, at least one of the developed modern-steam projects has reworked the idea for welded construction.

(Nitpick: it's "Jacobs-Shupert")

I think this has been discussed on here somewhere.

The problem with Pitkin et al. is that it put a big lump of complex machining where it would be exposed to combustion-gas heating, and ash, and take up space, and likely cause additional thermal effects and stress on the fireside plate. A nifty idea, in theory... not so much in practice. Like Baldwin's hinged boiler/feedwater heater.

First problem with the chain staybolt: putting it in is going to be interesting. Second, how will you keep boiler water from corroding where the eyes of the chain fret on each other ... lengthening the staybolt even as you weaken it. Then if there is a pressure surge in the water legs, you get just that much more 'free' acceleration before the staybolt snaps up short ... perhaps breaking the chain, perhaps tearing the inside threads out of the plate more easily, perhaps contributing to the kind of acceleration of water mass that produces fulminante boiler explosions. I would no sooner go near this nifty device than I would use Nathan drop plugs in the number and configuration that their own literature indicated would be needed to 'safeguard' a large modern American crownsheet...

I notice that nobody is discussing OVS Bulleid's approach to NON-flexible staybolting, which I do think has merit in welded boiler construction...

Just for "fun", below are 8 patented designs for flexible staybolts.

A. F. Pitkin


R. J. McKay


A. C. Negus

B. E. D. Stafford


Stafford-Dodds


Dodds-Stafford

J. A. Dowd


R. S. Mennie


That's it.

By the way, I did not mean to bury Overmod's good posts from today (Feb. 7) with all these images. If you missed Overmod's posts, please scroll up.