Where availability was headed in 1948...80 broken out of 205,279 inspected.......

What is that publication?

Railway Mechanical Engineer Nov. 1948.......
plus a little more......

Very interesting posts Matt. It sounds like staybolts were approaching being a non-issue. I recall reading (but I've never been able to find the quote again!) that the N&W averaged 3 broken staybolts per year on their modern power. That's not hard to believe based on what your article says.

It does sound like they had quite a way to go on making reliable superheater units. Wardale mentions similar issues with superheater connections in his book, and Porta had noted the same thing years earlier during some of his work. They maintained that this was largely caused by insufficient elasticity in the superheater joint bolts. This could be drastically improved by using longer bolts and stacked Belleville spring washers so that clamping force would be maintained despite wear or fretting corrosion at the joints. (This seems like something that could be retrofit to current operating steam very easily.)

I've always wondered if there wasn't any better sealing technology available by the late 40's than a ground metal-to-metal joint. It seems like spiral wound gaskets might work for this application, but I'm not sure when they were developed.

SLM went one better than that on their 1990's built rack locomotives by deleting the superheater element joints altogether. These locomotives feature a welded superheater assembly consisting of a flanged inlet header with welded-on elements. The outlets of the elements lead directly to the cylinder inlets (1/2 to each cylinder), where they connect to the cylinder by a long, narrow flange. I have a picture I'll post if I can find it. Apparently this arrangement has been very reliable despite high superheat temperatures (700 deg. F + IIRC). Of course these engines are oil-fired so they don't have the problem of cinder-cutting to deal with.

So why the big push for fillet welded staybolts if these gentlemen were making staybolt failure a non issue?

Robby Peartree

I'd venture to say it was far from a non-issue. They still had broken bolts to deal with, even if a small number, and they still had hundreds of thousands to inspect, no matter the time interval.

What really hurt was that diesel availability was much better from the get-go and was still getting even better at the time, as railroads began to better understand how to utilize them and that they didn't have to maintain them to steam engine time/mileage standards.

I purchased some Barco union elbows suitable for steam service recently and noticed they had replaced the metal seal with Teflon. Teflon was a available after the war. I have to wonder if it could have been used in locomotives for some of the sealing problems. I do not know how Teflon stands up to steam leaks. It always seemed rather soft, but it is an amazing material.