Hello friends!
Please may I ask for some advice? Now that my launch engine is complete, I have gone back to my locomotive and am in the process of laying out the Baker valve gear for a 1 1/2" scale 4-8-2. I have downloaded the software created by the late Mr Dockstader and, in combination with my drawing board have come up with a potential solution. The question now is what constitutes a good solution? What are good valve events so what am I trying to achieve? Everything I have read tells me how to lay it out but not quite what I am aiming at so I would value your opinions very highly.
I want about 1/64" of lead so in mid-gear I get this:
The lead is fine and, although the laps are different, I can make the valve to suit. Here is the Sine chart as well.
I set up the steam chart for nine reverser positions from mid to full forward gear and get this.
The chart doesn't tell me a lot but comparing the cut-offs between front of cylinder on the right and rear on the left, they are not identical but almost match my 75% cut-off target in full gear. (Don Ashton's recommendation). They do diverge in the mid-range so my question is, is this significant and will it matter?
As you can see below for the same set-up but in reverse, they differ more significantly and you can see the bias in the shape of the chart.
I just don't have a feel for what are 'good' valve events and how sensitive it will be so I would very much appreciate some views.
Cheers!
Steve