Mindsigh

Simple steam engine

Posted by jerry on September 3rd, 2006 — Posted in DIY, Journal, Steam, Technology

Inspired by McCabe’s runners I decided to have a go at adapting one of McCabe’s designs using standard plumbing hardware and a few basic tools. I bought an ‘L’- join from a hardware store, and a brass screw cap for the valve chest. The one I modelled mine on was the ‘Paul-Zee’ design.
I smoothed the bore as McCabe suggests – using a dowel in a drill with some sandpaper wrapped round. With the bore smooth, I took a three-eighth inch bolt and mounted it in a portable drill and spun it against a grinder wheel – with the grinder going in opposite directions – that gave me a nice rounded bolt head ground to just fit the bore of the plumbing pipe. I then found a washer and ground it to fit inside the plumbing sleeve on the end of the joiner.

I cut off the threaded portion of the bolt and drilled a small hole near the end – this would take the connecting rod.

I then took a small bolt, cut off the head and drilled down through the centre to make a small tube with a thread. I then drilled a hole in the plug cap just big enough for the bolt and cut a thread into it using a tap and die, and screwed it in place, held by a lock nut to keep it in place. This is the steam inlet pipe.

Then I drilled a transverse hole through the plug in line with the body to take the slide valve. The valve is made from small diameter steel rod, with a hole drilled near one end for the valve connecting rod, and another hole drilled to line up with the steam inlet hole when the piston is about halfway along the cylinder.

I filed the valve flat about half a centimetre from the steam inlet hole so it would line up with the edge of the valve chest internal wall – as I hadn’t used a solid plug as recommended.

Then I made a wooden base for the engine

Then after scraping off the flux from a steel welding rod I then cleaned the rod and cut it to be a good length to make the crankshaft. I carefully bent it to make two cranks 90 degrees out of phase, then made short connecting rods from wire to connect the crankshaft to the piston and the valve. With lots of spray grease the whole lot rotated quite smoothly, and when spun in the chuck of my drill it made a very satisfactory engine sound.

Tomorrow I shall make a flywheel, and then hopefully I will know if I have made a fatal error in construction. Here is the current state of the engine, and an animation based on rotating the crankshaft.

Anyhow – it’s a fun weekend project 🙂

Cheers
Jerry

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