Exhaust port

Im currently building my first model engine and before i get any further, have a question. Should the valve block have an exhaust port drilling on either side of the port/piston, its the potty engineering horizontal mill engine that you can build without a milling machine. As i cant see how it wont just pressurise both sides. Cheers Mark

There is an existing thread on building a Potty engine.

Model Engineer thread

There may be an answer from someone with experience of building it in there.

Martin C

Follow the drawings. They work. Been a while since I made mine but ISTR the valve block has two cylinder ports, two exhaust ports and one steam inlet port. The two exhaust ports are the ones at each end of the block. The inlet port is the one in the middle of the block. The cylinder ports are the pair towards the centre that match the drillings in the cylinder.

I think the potty is like this, it is a common design for model steam engines.

Animated steam chest

Martin C

Later posts proved me wrong. Looks like it may be a spool valve design not a steam chest design.

Edited By Martin Connelly on 24/05/2020 12:04:03

Now that's strange, I thought I'd answered this one, and the pictures are in my album! Looks as if I forgot to press 'Add Posting' or summat. Anyway!

The two holes in the blue face are the exhaust ports. They're normally underneath. The pair on the right align with the cylinder passages. The inlet is on the other side of the block.

This drawing might help:

Dave

Fromn another piston/spool valve engine

Steam or air comes in from the central inlet and the position of the valve piston sends it to the port at the top of the drawing which goes into the cylinder and pushes the main piston down.

Spent steam or air on the other side of the main piston is ttherefoer pushed out the port at the bottom of the drawing, through the drillings and the valve piston directs it to exhaust

Edited By JasonB on 24/05/2020 12:21:11

Thankyou everyone, the picture with the blue face to the block is how i imagined it should be 👍 will get drilling