A Stuart Twin Oscillator

[Sanjay F]

Yikes I didn't 

Oh dear that was a very bad idea, I didn't even think about that ..........

[Sanjay F]

Finished the day of by making the piston rods, pistons and fitting the 'o' rings - another new one on me, I've never used them before. (and they fit the cylinders nicely)

Not a bad Bank Holiday weekend and thanks for the help everyone, hope you had a good one too   

[crueby]

Great progress!  You've picked up a lot in the last few projects!

[Sanjay F]

The cylinders are now complete with the hole for the pivot pin, ports and lagging holes drilled. My goodness the ports come in close to the cylinder ends but they should be fine as the cylinder cover spigots are 1/32".

One to note is the drawing gives a distance from the port face of 1/16" for the lagging screws and should be 5/64" otherwise the screws will overhang

[Team ricky]

Looking good Sanjay

I know folks tend to say oscillators are easy beginner engines…….But there are a fair few difficult and accurate set ups envolved ! I found them equally challenging vs regular engines lol 😂

I like your jig block and thanks for the link

[Sanjay F]

Thank you, yes and agreed, I had the misplaced view that this little engine was going to be a breeze, how wrong I was! This is my first oscillator and have come the realisation that they are not beginers engines, and I would have definitely struggled with this as my first engine without some prior knowledge.

The cylinder covers are now complete and I had the same issue as several builders of this engine in the past which is the grooves for bolts need a fair amount of work to get the covers to fit. I had a round needle file which fitted nicely and worked my way around and at either end.

Also when making the top covers, drill the holes first and then part off otherwise you end up with a problem such as I did which is how to hold the cover for drilling. In the end I had to make the little jig you can see in the photo and glue the covers on! 

Piston/cylinder assemblies are now complete (bar the cladding) with gaskets and making a puffing noise 

[Sanjay F]

The reverser has now been machined; a clever little casting! The edges look a bit rough, but they are not, they are sharp as a razor and what you can see are burrs pushed inside. I don't fancy digging around and losing the sharpness on a something which is meant to be flat, very flat!

[crueby]

At least clear off the burs enough that no pieces can break off later and mar the inside of the cylinder. The tip of a needle file or xacto knife can be enough to break them loose.

[Michael S.]

Hi Sanjay,

Couldn't you deburr the two grooves with a rotating, cylindrical diamond grinding wheel?

Michael

[Jasonb]

1000g wet & dry plus a flat surface works for me

[Sanjay F]

Okay - I'll give it a go, with the 1000 grit on the surface plate or knife edge as the pieces are very fine and just clinging on 

[Charles Lamont]

Before the final rub (in a figure-of-eight pattern) you coul probably tweak out the burrs with something like a cocktail stick or fine tweezers. The edges of the cavities are not that critical.

[Sanjay F]

Well this is a bit puzzling, what have I done? I have one crosshead cut out facing outwards and one inwards which is correct, but only one cylinder is flush against its valve face? See photo (red arrow) and gap between top cylinder and its face

[Jasonb]

I thought they were notched to the mid point?

[Sanjay F]

Here's the diagram and I've realised what I have done - I have made the thickness 5/32" - 0.005 as per the diagram, but taken it from the outside 

You are correct should be mid point - right, a trim required!