The Home Machinist!

It appears you have identical problems, Freds Hunslet was reported to steam well in his first contribution.
However it also ejects ashes, don't you have that? What type of coal are you using?
Kind regards
Jos Koopmans

During the research with Michael Guy we were pointed at research showing that for longer stacks a reduced taper angle was superior. The reference is in the original discussion. As for Lempor applications, one of the major flaws with Lempors is the angle of the orifices. After a lot of testing we con...

Pfff, confusion reigns! The issue is to get the stack exit velocity down to the level with sufficient draft but low enough for not entraining ashes. So tests first to see whether such a condition exists.
Kind regards
Jos Koopmans

Hi Fred, If I understand you correctly, you kept the .386 orifice, decreased the stack diameter from 2.32 to 1.1 in. and its length from 12 in. to 2.2 in. As a consequence there is a huge difference of the velocities in the stack. In your present case at the exit the theoretical total mass would be ...

Fred, Your exhaust proportions look ok to me. However, I have no idea how the orifice diameter was determined. What are the stack dimensions given on the original drawing? If the stack is wider and shorter it may diminish a fierce blast. Right now my suggestion is to try and increase the orifice dia...

I intend to add as little as possible since a full explanation takes two pages. Once the jet exits from the orifice it starts entraining and the velocity distribution has the shape of a Gauss curve (bell shape).After entering the chimney the transfer of momentum does not really change its behaviour,...

Yes, but it is not really about whether it is working or not. It is about whether it is working with the least effort and lowest backpressure.
kind regards
Jos Koopmans

Oh dear! Do I really have to go on explaining that this is nonsense? Around the jet an induced flow is formed so the expanded exhaust never never never fills the bore. It is the transfer of momentum within the stack that takes care of the suction by the stack.
Kind regards
Jos Koopmans

Yeah, third best solutions can also work!
Kind regards
Jos Koopmans

I think it should be on the upper side, not at the bottom, the main reason is the way both fresh steam and exhaust steam lines are plumbed. They act as frame stretchers as discussed here: http://easyweb.easynet.co.uk/~chrish/cancelled%20account/robroy.htm There are more suggestions for modifications...

Nice drawing! There is a strong suggestion to have an additional cross-bar just behind the cylinderblock. I found it indeed necessary.
Kind regards
Jos Koopmans

I bought a secondhand Rob Roy in parts which appeared made by the book. On assembly it appeared that it could never have worked properly. My caveats: a) I could not get the vertical slides steamtight until I made a tiny spring in the slide valve nuts, p 32/33 b) the crosshead pump should be carefull...