ross yoke in excel

[Ante]

I was trying to find some simple calculation to predict ross-yoke mechanism.
Because i did not find it, I made some simple excel file. So if someone need it just download it..

input variables are: radius of crank , bottom lenght of "T" element and two arms.
output is two strokes, phase angle and and centers of pistons
One simplification exist, that is motion of "T" element, it slides in vertical line. In fact it moves along a arc.

file is not locked
Salute! Ante

[Ian S C]

My method of finding the workings of the Ross Yoke was to build in plywood a model, a bit of adjustment to that, and I went ahead and built my motor. There is a photo in my gallery of my interpretation of a Ross Yoke motor. Ian S C

[Ferraccio]

Ciao Ante!
I understand that you have provided the movement of the lever to "T" as vertical.
This derives from the fact that you did not put in the variable the length of the lever that laterally the T lever.
Congratulations for your work, if so, however, this is not acceptable, since the movement of the lever arch play a main role in almost complete flattening of one of the two "lemniscate" such as to reduce to a few tenths of a millimeter displacement horizontal in one of the two nodes (and that node is used for the piston engine).
The second lemniscate is the other node, which is proportionally increased in horizontal displacement, and is used by the displacer.
Since the sealing surface of the displacer is higher than that of the piston, it is possible (alpha configuration) knowing the maximum horizontal displacements of the two two lemniscate, provide for the absence of upper pins, confined to vertical stems rigidly attached to the piston and displacer (perhaps) to float, and this is a remarkable mechanical simplification.

I extracted the development of the movement by CAD tracing of twenty positions of rotation, setting also the length of the piston and displ. stems, and considering that the horizontal shifts of the lemniscate were not excessive for the sliding piston and displacer without pins.
Salute a te!
Ferraccio

[Ferraccio]

I correct myself:
of the lever that BIND laterally the T lever.
Scusami, Ferraccio

[Ian S C]

I have only tried on the plywood model, but the bellcrank can be guided with a vertically slotted guide engaging a pin at the same point as the place where the side lever is fitted, this eliminates the slight curve in the motion.
I 'll perhaps fit my motor this way next time I pull it to bits, Or when it break down, its going OK at the moment so I'll leave it alone.
Find a copy of "The Stirling Engine Manual", vol 2 by James G. RizzoThere is a bit there about the Ross Yoke, including an adjustable one. Ian S C

[Ante]

I finished file and here it is, finished ross-yoke.


Salute !

[Ferraccio]

Ante excuse my bad english, I should be happy if you speack italian...
About your "Andy Ross in Excel": I'm not so abile in excel as you are, but I've done a variation, with one arm reduced to zero, and the other dimension optimized in scope to have minimum horizontal displacement, (reducing lateral forces).
Adpting double crank (one for piston and one for displacer) you can have a shape for "parallel" gamma, or alpha, engine.
(This archiecture of leverages are similar to beta "Philips bungalow set").
You can find here annexed an Excel file of my solution, in bottom (left) you find the dimension relations starting from the crank radius, for have the minimum relative horizontal displacement.
In Philips bungalow set, they have foreseen an "elastic"rod to avoid rotation or lateral forces residual on alternate running.
Ciao, Ferraccio

[Ante]

@ Ferracio
Sorry for long waiting on my response. My english is also bad so no reasons for apologies :)
I understand what you are thinking, but my opinion is that bigest advantage of ross yoke (except almost perfectly straight leading) is simple crank shaft. For our models this is easiest way to make two linear motions with angle of 90 degrees .

Salute!

[Ferraccio]

Understood thanks!

[Ian S C]

Sorry Ante, reported you by mistake, there was someone else I was not too sure of. Ian S C

[MvanderSluys]

Since the file was missing I created a new one. Lots off fun building!