Speed/reversing control

[modeng2000]

I came across this picture recently and have been trying to work out how the speed/reversing control might be constructed. I understand the 'disk type' but this one is of smaller diameter and taller.


Any ideas please?

John

[AndrewP]

Looks as if it's moving something like a piston valve up and down, that spindle appears to be packed like a loco's valve rod.
Can't picture the drillings in the chamber though.
Whole thing looks vaguely Shayish, interesting, any more pics?

[modeng2000]

Andrew,

Thanks for your interest. I have not worked out the drillings either. It is normal for the control to make a 90 degree turn in either way so any thread would probably be fairly coarse to get enough movement.

Here is the link to the web page where I found the picture. There are several others and using Google to translate the text is readable:-

translate.google.com/translate?hl=en&sl=de&u=http://www.buntbahn.de/modellbau/viewtopic.php%3Fp%3D4843%26sid%3D3e212da55e01abf073466a07f18db7e3&sa=X&oi=translate&resnum=10&ct=result&prev=/search%3Fq%3DWaldbahnlok%26hl%3Den%26rls%3DGGIH,GGIH:2006-51,GGIH:en

I suppose this topic should be in the Gauge 1 section.

John

[baggo]

John,

it could be a simple rotary valve similar to this:



The valve is just a piece of bar with a slot on either side connecting to the vertical drillings in the housing which go to the cylinder ports. In the middle (off) position the centre of the valve blocks off both steam and exhaust pipes. When the valve is rotated in either direction it connects the steam and exhaust to the cylinder drillings, the direction of running being dependent on which way the valve is rotated. The speed will depend on how far the valve is rotated.

Just one possible design. Hope the drawings explain what I mean!

John

[AndrewP]

That would explain the cheese headed blanking plug on the front of the chamber as well - by jove I think you've got it! Just as well, my head was starting to hurt.

I still think an inside admission piston valve arrangement could work - using O rings as seals might make it relatively steam tight too - I feel another distraction from Rob Roy coming on - oh no.

[modeng2000]

Hi John, I also think that you have given the answer to the problem.
I just couldn't work it out.

John

[paul]

Nice engine however the reverser works... but why the strange brown colour??

[modeng2000]

Thanks all for the info on this reversing valve. The seal between the rotating and fixed parts would have to be sound, just carefully made I suppose.

Paul, the colour is probably black and has changed in the copying from one site to another.

John