Thanks Peter. The Hackworth gear does indeed look like it has a similar channel which lets the valve lead the crank depending on what angle the channel is at. Just need to work out the geometry that will move the valve rod in using the cylinders movement rather than the link from the crank that the Hackworth uses.

I too think it sould make a nice model, The old advert says the engine came in 4", 6" and 8" bores, it does not help that the bricks on the wall vary in length but I think I will assume that the 6" is illustrated so at 1/4 scale that would give me a 1.5" bore x 3" stroke which my compressor can just about keep up with. The flywheel will also be an easy job cut from the solid.

Watch this space

J

PS While I'm here I seem to remember the SMEE having an old oscillating wall engine that they have on their stand at some shows, does anyone have a photo of it?

Edited By JasonB on 01/08/2016 14:54:59

You could go teh forging and bending from solid route but it would need a good heat source to form tight bends. Or the other opttion is to just machine it as you would a solid crank and rather than leave the webs rectangular section shape then so the are round, this could be done with a roundover bit followed by files.

A third option would be that I design it to use a SG iron cast crank from something else like this one one of mine.

Duncan, there are several designs that use an eccentric such as Penn's which I mentioned earlier. But this one does not use an eccentric there are a few ways these were arranged, in this case there is a STRAIGHT channel much like on Joy or Hackworth valve gear but the rocking motion of the valve chest provides the main source of movement not an eccentric.

The only thing I can't see is an actual reversing lever for the operator to select direction.

This is one example without an eccentric but as the pivot is fixed off to one side of the pivot point the engine can't be reversed, also better suited to end pivoting rather than middle. Valve gear closeup at about 1min in.

And this is Elmers No 42 which is close to whats needed but not reversible

Edited By JasonB on 02/08/2016 07:44:09

As I said earlier the roller is in a straight slot that is set at an angle. By altering the angle of the slot you can set the valve to lead the crank in either direction and therefore reverse the engine, the steeper the slot the more lead the valve has. Have a look on you-tube for some examples of hackworth or Joy valve gear to see how the straight slot works. The only difgference here is how the movement is generated.

From having seen that SMEE one running at the shows I would say it's a good runner.

J

PS Thanks for the extra photo Gwil.