Re: 493 June 28, 2019

I should point out (or re-emphasize) that once all the partially broken bolts were worked out of 497, she settled down to breaking perhaps one or two a year. Most of the broken bolts we changed had been changed several times before. With each bolt change, the bolt hole gets reamed to the next size larger. I do not know what the original size for the bolts was (perhaps 7/8") but we were changing out bolts bigger than 2". The larger the bolt, the less it can flex with the expansion of the steel, which causes it to break more easily. Our solution was to weld up the bolt holes. Later we developed "doughnuts" of steel with the proper sized staybolt hole in them. The old broken bolt was removed and the hole enlarged to 3"+ and the new steel welded in to both the firebox and the outer wrapper. Then a proper sized staybolt was installed.

Apparently, 497 never got a major firebox renewal that the other 490's got in the 40's and 50's. If this had been done, the over sized boltholes would have been welded up and stock-sized stays installed.

And yes, the back lower corners of the firebox was where our first troubles were. This was also where the leakers were when the D&S turned it over to us, and the source of the in-cab steam leaks.



Edited 1 time(s). Last edit at 07/15/2019 12:01PM by Earl.