Oscillator with two ports?

[PaulR]

I was thinking about a single-acting oscillating engine with a small stroke and short 'wheelbase' (from pivot to crank axle). With the usual single port in the cylinder the ports on the port block would need to be very close together and/or small in diameter. It occurred to me that it might be possible to have two ports in the cylinder and thereby put the holes in the fixed port face much further apart. There would be compression on the return stroke but I can't decide if that would be any worse than on a single port version. As far as making the thing, the slight issue I see is the ports breaking through into the cylinder where it is curved. EDIT: or just drill them before making the bore 

Any thoughts?

In this picture (with a circular cylinder, don't ask!), the fixed port block with inlet and outlet is shown at the top, the piston is blue and the cylinder ports are white.

[Jasonb]

It looks like it should work.

I always prefer to do the bore first as any small holes can make the drill wander, not such an issue if you are finishing with a boring bar but a reamer will follow a wayward drilled hole.

[PaulR]

It looks like it should work.

I always prefer to do the bore first as any small holes can make the drill wander, not such an issue if you are finishing with a boring bar but a reamer will follow a wayward drilled hole.

Thanks Jason. Here's a cross section using the proportions in my first drawing - I think it would be easier to drill in from the sides (yellow), up from the port face and then plug the yellow holes. What do you think?

EDIT: Ignore that, I'm getting the cylinder and the port face mixed up there - been staring at a screen too long today!

[Jasonb]

Nearer to the edge than I thought but I would say it will still be OK to drill in just from the port face. make sure the work is held down well so if the drill did snatch it or the vice won't get picked up.

You could always try in a short scrap piece first

[PaulR]

You could always try in a short scrap piece first

This is how the cylinder ports would look, which should be fine I think.

[Team ricky]

Superior design?

[Team ricky]

Only one set of port used , the drawing simultaneously shows old school and EVT confusingly lol 😂

[Jasonb]

I applied those larger holes on my Preston's Oscillator after seeing the EVT site

https://www.modelenginemaker.com/index.php/topic,9519.msg213652.html#msg213652

[PaulR]

Superior design?

In what way is it superior and what does EVT stand for??