7.25" gauge Tinkerbell loco valve gear (Heywood)

Sorry for the choppy capture...

This is a clip of the gear operating in Charlie Dockstader's software. I started with original geometry as-drawn, and it didn't work - at all. Roger Marsh drew some big errors! I messed with dimensions for hours and this optimised version resulted after quite a bit of fettling, most substantially the removal of an erroneous pivot point above the die block that throws everything completely to pot!

It's not perfect (what valve gear actually is? - looks to work better than it's made out to, once the specs are right!). The only thing I can't do (not through lack of trying to find out how to) is incline the cylinder centreline in the program, however the error between horizontal and the correct 2.39 degrees is a cylinder to axle centreline linear error of +0.021", which can be made up in realworld valve & crosshead adjustment. The real angle is the result of frame dimensions, the angle itself not being specified but rather the trigonometric result of plotted geometry - which in simple terms, means this gear setup will work perfectly with my main frames, which were cut and drilled a full year ago... the sum of progress so far. Soon though, watch this space...

Category:

Science & Technology

Tags:

• roger
• marsh
• tinkerbell
• heywood
• valvegear
• valve
• gear