I’ve been making odds and ends for Christmas gifts for years but thought this year I would see if I could scale things out a bit. With the recent addition of a 1500 MX mill to the shop it seemed like some automation could bring the quality up and labor down. I had an old design for a basic steam engine that was made on a manual mill and lathe years ago that I intended to model and CAM for the 1500 MX. It became obvious early on that not only was the design primitive but didn’t lend itself to CNC. I used the same principles from the early engine but started with a clean slate leading to what is pictured here. Starting over was definitely the right approach for this project.
All of the parts were made on the 1500 MX with the exception of the spring, bearings and fasteners. Most is 6061 aluminum but the piston is Delrin, the air fittings are brass and the main shaft is steel.
I’ve given most away as Christmas gifts and they have been well received. One of the engines got a custom wood pallet and crate inspired by the Tormach 1500 MX packaging.
Working on the CAD for the USS Monitor steam engine. Not the fancy one. Couldn’t find the plans for it. They must have removed it from the website. I’m modifying a lot of the parts so they don’t look so blocky. Kinematics are spot on from the prints though. Good starter model.
Absolutely love this build! The shape and sizing really gives it a hefty feel, and the cutaway base is a nice touch.
Are you mostly gifting to people with access to compressed air? I’ve been thinking about doing a run of engines, but that’s been one of the things holding me back. Maybe I’ll try flame lickers or something.
Most people use an air compressor although to be honest I suspect a few will just admire the model on a shelf and may never run it.
The model is pretty forgiving about low air pressure. I was testing them after assembly with about 2-3 PSI and they loaf along pretty smoothly. The Delrin piston, close tolerances and ball bearings throughout make for a low friction engine. The cylinder was bored using a 15/16 reamer that I modified for TSC by shortening and drilling a hole through lengthwise. A fine boring head might have been a better choice but pricing was higher and this seems to work pretty well. I don’t have a tool to measure surface finish but it’s pretty smooth.
I love everything about this project. Did you employ a fixture for these or is this all vise/ soft jaws territory?
I know little more about steam engines than what I have seen on YT so please forgive my ignorance. The steam is coming from a different source and pumped into this engine?
I didn’t use a fixture for any of the parts. All first operations were done with TalonGrips or VersaGrips and then subsequent steps done with soft jaws or smooth. A few items were held in a small lathe chuck I have mounted to a plate that allows me to easily hold it in the vise.
I was considering fixtures for some of the pieces and if I was going to make more I would probably go that route to increase cycle times and reduce babysitting of the machine. For a lot of the smaller parts I was able to fit multiple of them in a single soft jaw. I had a few concerns about holding more than two parts at a time so this was mostly done with the plastic more compressible pieces. The metal parts were done two at a time if size permitted. Like wise, I was able to hold two pieces of raw stock at a time for the smaller parts reducing machine load, unload time. I was doing other stuff on the mill during this project so I had some interest in keeping the vice in place.
For simplicity I used multiple WCS for the two up parts. I found it easier to just set the two origins in G54 and G55 then tell fusion to run the job in both. For instances where more than two pieces were being machined I used the Fusion pattern feature to handle the multiples. This worked out well when there were soft jaws that would space the parts evenly and had an easy to reference origin. I suspect more advanced fixturing would fit great with the patterns feature.
Any of these little “steam” engine models are usually run on compressed air. For this engine at least compressed air can be connected to either port. The direction of rotation will depend on which is used as input and which is used as exhaust. The simplicity of this engine design is that it only has pressure applied to one side of the piston. Usually steam engine pistons are powered in both directions. Because of the single sided behavior in this engine the flywheel must hold enough energy to complete an exhaust stroke and return the valve back to allow compressed air into the cylinder. I’ll see if I can get time to add a couple of cutaway views of the engine so you can get an idea just how simplistic this is.
