I have been reading Roy Darlingtons book in which on page 30 he outlines the sizing recomendations for a Stirling engine which are:

Power piston diameter = 2x sweep

Displacer swept volume = 1.5 x power piston swept volume

Displacer swept volume = 1/3 total volume

Displacer cylinder length = 3x diameter

On the basis that I want to

*measure twice and cut once*so to speak, I am trying to dome some sums before I start drawing. In order to comply with the dimensions above, everything can be described in terms of the power piston diameter:

So if we take the diameter of the power piston as “d”

Sweep = d/2

Power piston swept volume = pi*d^2/4 *d/2 = pi*d^3/8

Displacer Swept volume = 1.5*pi*d^3/8 or 3*pi*d^3/16

Total volume of displacer cylinder = 9*pi*d^3/16

If we take the diameter of the displacer as “D” then

the volume of the displacer cylinder = pi*D^2/4*3D = 9*pi*d^3/16

Therefore D=0.909*d

The length of the displacer =2.725*d

The crux of all this is that the sweep of the Displacer piston will be 0.908*d whilst the power piston will be 0.5*d. This means that the displacer needs to have 1.82* the movement of the power piston.

All the images that I have seen of Ross Linkages show a symetrical arrangement, but this will not allow for the 1.82 variation in movement. I have put together a spread sheat to calculate the dimensions that I will require for this asymmetrical arrangement and think that it should work but I would be interested in what anybody else thinks.

The spreadsheet can be found below if you are interested.

https://1drv.ms/x/s!AnMn0rJaalvJ-GWjfOTzfe2qIXh7