So is this a failed design?
Possibly - for higher maintenance costs certainly (was a problem with all compounds), but I don't understand the other two problems with it (why would the high-pressure cylinder limit the ability to use steam, and the low-pressure cylinders are supposed to snag only if they aren't within the line's standard cross section). But two cylinders on the same crosshead - that sounds like a recipe for stress cracks to me. *Lunatic*, n. One whose delusions are out of fashion.
The Colorado Midland had trouble with their engines snagging because they had such tight curves, some exceeding 16 degrees--which is a very sharp curve for a standard gauge railroad. The concept of "standard cross section" wasn't really in play during the 1890s in Colorado. Here's an explanation of how curves are measured in 'merica. http://www.du.edu/~jcalvert/railway/degcurv.htm
Here's an interesting account of the terrible snowstorm in 1899 that closed the Colorado Midland for 78 days! http://www.netreach.net/~rphillips/_pg3_19.html
I still don't understand this. First, the high-pressure cylinder is where normally the single outer cylinder is, and that can be rather big depending on the locomotive. High-pressure cylinders are smaller by default - force is proportional to the pressure imbalance and the area of the piston, so if say pressure is reduced by 75% between the two cylinders, the high-pressure one has to be half the diameter of the low-pressure one. (In this example, a single cylinder of a non-compound locomotive with the same power would have a diameter sqrt(2) times the high-pressure cylinder's.)
Thanks for that on curves - I saw it a few times, now it makes sense... 16-degree curve, that's a 109 m radius curve, ouch!
Here's an interesting account of the terrible snowstorm in 1899 that closed the Colorado Midland for 78 days!
Also see my earlier Forgotten Colorado diary for more on the Colorado Midland (from which I also linked to the same story) *Lunatic*, n. One whose delusions are out of fashion.
