Robinson hot air engine question?

[wespete66]

Hi all!
I am studying the Robinson 'B' hot air engine by reading what I can find and by patent #445904 drawings. I am also 3D modeling it to help me understand it.
I've found little about the speed regulating valve found on the back end of the power cylinder. Can someone help explain the workings of this assembly, how does it work? It looks to me that air flows freely between the displacer and the power cylinders unaffected by the valve, while any pressure/compression inside the power cylinder will force the poppet shut against its seat, and any vacuum inside the cylinder will pull the poppet open against the spring to allow outside air to enter. Yes??
Does anyone have pics of the components of the speed regulating valve?
Thanks!
Wes

 

[Jasonb]

You adjust the valve looser so that it is drawn towards the power piston as the piston moves towards BDC which restricts the flow or tighten it so the flow is not restricted as much

It is no more than a flat head on a stem, a weak spring and an adjusting nut on the end of the stem.

Red flow of hot air draws the valve forward and closed the green gap, spring pressure alters its movement and therefore speed of engine.

It does not bleed in air, only restricts the internal flow

My scratch built 24mm bore one

 

[wespete66]

Thanks JasonB for the explanation! That makes more sense now! I guess one should not take patent drawings for granted.
Your engine is a small one. How big is the displacer bore on it?

 

[Jasonb]

36mm diameter

 

[wespete66]

This is my "concept" design at this point. (working out geometry, sizes, placements, etc) I have a power piston bore of 2.75" with 2.75" stroke, and the "displacer" is 5.50" bore x 1.838" stroke. Looking at the swept volumes, the ratio of displacer/power is 2.654/1.
- Does this ratio seem practical, or should I try to achieve a higher ratio? (larger displacer, smaller power dia's..)
- Is there a listing somewhere of the actual bore diameters of the Robinson B engines?
- Also, I've read about drawings for a Robinson B engine were available somewhere on the webs. Anyone know where to find those?
Thanks!

 

[Jasonb]

A A4 is:
Power bore 4.5"
Power Stroke 3.0"
Dis Bore 6.75"
Dis Stroke 2.0"

A No5 is
Power Bore 7.5"
Power Stroke 7.5"
Dis Bore 12"
Dis Stroke 5.0" approx

The model mine is based on was a half scale of a A4 measured from an actual engine. I scaled it down again but the proportions are the same