Steam valve, is this a better way to make?

[geoff]

I have recently finished Gerry`s Beam engine and while i was working on the cylinder ports i thought i would start with just one hole instead of the 3 in the plan, as this may help it to run slowly as it should. I made the valve in the conventional way by carefull milling with a tiny end mill and after fitting to the engine you realise how precise you have to be with the dimensions. so i came up with an alternative method which also could be help if you don`t have a mill. The recess has to be 3/16" and the o/d 5/16" so i thought why not just drill it with a endmill cutter on the end of a 5/16" bar in the lathe and then part it off, i had to make a couple of flats on the sides as you may see from the pictures. but it was so much easier to workout. I fitted it to the engine and it runs just as well. Now i see the advantage of having just the 1 port which still lets in plenty of air.
Geoff

 

[steamer]

If the goal is to get it to run slow...sure. For performance, you want as big a ports as you can get to reduce the pressure drop during admission.

NICE work on those parts! :bow:

Dave

 

[gbritnell]

Hi Geoff,
You have to understand steam engineering to know the proper shape and size of ports and valves. I know your's will probably run on air but the original intent of these air engines was to operate on steam.
Here's the short version. When it's time for the admission of steam to the cylinder you want it to be quickly and with as much volume as required by the engine. Therefore you want a wide straight edge to the valve and the port so when it's opened you get an almost instantaneous charge of steam/air. A well engineered engine with properly designed ports will run efficiently, fast and slow but an engine with poorly designed ports will only run at slower speeds because it is being starved of steam/air.
Your engine will no doubt run slow but it will also do this by limiting the amount of pressure being applied as opposed to constricting the air flow.
gbritnell