Mount Trapezium

[Jasonb]

This shows the metric on the right and imperial on the left, Ideally the left should have a gap below the nut like the metrc one does. Also depends if the chest is 1/2" or 13mm with the rod central or anything else.

[redhouseluv]

Thanks all for your feedback and the drawings help a lot! Apologies if I'd read the text more carfefully it does say the nut is a brass rod 

I am aware that getting this right is key to the successful operation of the engine. Here is the diagram of the valve chest and some text re. fettling to get the adjustment correct

[Jasonb]

Are you making it to the imperial or metric sizes?

[redhouseluv]

I intend to make it in Imperial as all my tooling etc is Imperial. The valve chest is also Imperial so 1/2" overall depth and 0.250" to centre of where the rod will go

[Jasonb]

In that case I would reduce the length of the cylindrical nut to say 0.188" and centre the tapped hole. This will allow for 0.031" of lift.

As it is dimensioned in imperial it will not lift it will not lift

[redhouseluv]

Thanks Jason, that's great, that wouldn't have been known without your calculations. I'll make a start on it tomorrow and see where I get to

[redhouseluv]

The slide valve, nut and rod are now complete and are moving freely with a nice amount of room for lift. There's an understatement in the buildlog which states 'The steam chest is quite small for the size of cylinder and valve fills most of the space' - no kidding!! 

It then goes on to say the inside walls of the steam chest act as a guide for the valve which I've never seen before.....right now onto the valve crosshead and bolt

https://youtube.com/shorts/wcvFp_9q7zw?feature=share

[redhouseluv]

Hmmmm........this is a bit Heath Robinson, but it seems to be working atm......I think/hope!

The workpiece for the crosshead is too small to be held in my standard 4-jaw chuck; so I have a mini 4-jaw chuck with a 2MT backplate fitted into a 2MT to straight shank adaptor which is finally placed into the standard 3-jaw chuck........yeah not ideal, but I can't think of anything else?

[Jasonb]

For a lot of small square and hexagonal parts I just make them on the end of some round bar and mill the Sq or Hex.

[crueby]

Or if it will have a hole through the center, drill that and make an arbor with a center screw, and hold the arbor in the normal chuck.

[PaulR]

How about putting a piece of the same bar on each side (so it looks like a '+' viewed end on), making it three times the size?

[redhouseluv]

Thanks all for your great ideas, I'll try tomorrow with a clearer head and see where I get.

For a change I have plenty of small scrap bits which this can be made from, unlike the phosphor bronze which I bought for the bearings; the price of that for a small bit was eye watering!

[redhouseluv]

Crosshead and bolt are now complete, a little fiddlesome due to the size

This engine seems peculiar in some respects, some of the components are tiny in comparison to a Stuart 10v, yet other bits like the flywheel are huge

[Jasonb]

The Stuarts were generally made to do work at speed where as these more elegant scale models ran at a more sedate pace where the larger flywheel was needed to smooth out the stroke.

[redhouseluv]

The Stuarts were generally made to do work at speed where as these more elegant scale models ran at a more sedate pace where the larger flywheel was needed to smooth out the stroke.

Thanks for the explanation, I think this is the first of the more slower running engines for me. Does having a larger flywheel mean more torque for both model and real-world engines? It kind of feels like it should but I'm not sure mass naturally equates to torque ...........?