Roundhouse cylinder design change.

[funandtrains]

Can anyone tell me when Roundhouse changed their cylinder design to have flush valves chests? I'm interested as I have just bought a used Fowler and it has the newer chassis design but with older design cylinders. Was the redesign only cosmetic are did any dimensions change?

[TonyW]

The cylinder design changed around 1998/1999.

The mounting holes for the new cylinders are different (further apart) than those for the old design, so they cannot be interchanged without some work.

The new cylinders also have much better exhaust clearance due to a redesigned slide valve head. I have changed the cylinders on a number of locos from old to new to improve their running.

[funandtrains]

Tony,
Thanks for the information I guess this would make my Fowler late 90s then.

[TonyW]

Forgot to say...

The only exception was Argyll, which continued to use the old-style cylinders until it was withdrawn from sale in 2004. I believe that this was because the new-style cylinders would not fit under the footplating.

[JMORG]

I believe after 1998. I have a Katie from after millenium era and it indeed has the old cylinders. However, my Millie is one of the very first and it has the new cylinders :S
Katie could've been made from spares however, or was an unsold model from an earlier batch...

[Paul H]

Right around 2000, Roundhouse changed from cast cylinder blanks to CNC machined blanks. I have a Millie from 2000 (bought in January as new, old stock) that has cast cylinders and the rectangular valve chests.

Incidentally, this loco put in a run time of 1 hour, 20 minutes during its running in period this January. In the spirit of full disclosure, it was indoors and I did top up the gas tank once 10psi was reached and the cylinders warmed.