Cut off vs. Angular Advance

[David Smith 48Participant @davidsmith48]

I'm considering reducing the lap of the slide valves on my 4-4-0 with Stephenson valve gear increase the cut off from 70% to 80%. The objective is to improve starting on a grade or with heavy load. I recently found on the internet a design spread sheet by Don Ashton that provides dimensions and predicted results for particular dimensions. Has anyone had actual experience with Mr. Ashton's spread sheet and made actual parts to his proportions? How were the results?

Thanks, Dave

[David Smith 48Participant @davidsmith48]

[Simon CollierParticipant @simoncollier74340]

I've used Don's spreadsheet and taken the data to the Wallace simulator. I've not cut parts for Stephensons but would do so with complete confidence.

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