Re: C-17

Will try to answer your question regarding boiler courses and diameters.

Generally, the 1st course is the smallest. Every succeding course is larger, overlapping the previous course with a riveted seam. Whether a straight boiler, wagon top, etc, etc, this is a pretty consistant practice of construction.

The smokebox can be overlapped or, it can overlap the first course depending on the requirements of the design.

Most of the C class engines had straight boiler courses. None tapered such as the 20.

As boilers and locomotives were constructed larger, the need for high steam domes could not be maintained. So at times, a taper course was applied to get to a larger diameter course where where a shorter steam dome would be attached. This would allow for more steam space while not making a clearance problem on the external height.

Of course there is alot more to this, but hope this answers your question. Please feel free to contact me off list if need be should you need further discussion on the subject.

BTW, if a C class welded boiler were constructed today, there more than likely would be no riveted seams, just full penetration butt welded joints. Makes for a very nice construction with less maintenance and easier to do a boiler wash. But not something most local shops can perform.

Sorry for the delay in getting back to you.

Chris