Thinking about going into model steam engine making

I have been thinking about this for quite a while but not sure what addition tools that I will need. I have an Emco FB2 mill and a Compact 8 lathe so machining is no problem in general. Base on what I have read I may be lacking tools for cutting and forming sheet metal, silver soldering and may be steel hardening ? Currently I use carbide tools only as I don't have a grinder. Is there any frequent need for formed HSS tools ? What is the minimum requirement on tools and equipment to make my first steam engine ?

Rather depends on what type of steam engine. What tend to be called startionary steam engines won't need much more, these are the Stuart type of engines.

If you are thinking more of a locomotive or traction engine then sheet metal work and soldering will be required.

I think I will start with stationary steam engine and see how it goes.

I found Stewart Hart's PottyMill to be beginner friendly: a fabrication (no castings needed) with enough challenge to keep me on my toes. No errors in the plans, this rather crowded version is what I used, and there's no need for soldering or heat-treatment.

To avoid boilers and air-compressors, I built a Jan Ridders Coffeepot Stirling. Again, no errors found in the plans.

And another engine which called for brazing, which I think was designed by Mogens Kilde, but I can't find the details.

First two done with lathe and mill: the third engine was done with a mini-lathe and hand files.

Dave

Looks like the kind of engine in my mind. Will need some time to study the drawing. E.g. What "BMS" refers to ( some kind of steel ? ). Some of the parts are also quite challenging to make with manual machines.  An example : 

How to fit the Teflon ring onto the piston is also puzzling unless the piston is split into two parts : 

Edited By Y C Lui on 21/07/2022 03:33:27

BMS usually refers to Bright Mild Steel. The BMS part you refer to can be made from mild steel (I use black or hot rolled mild steel), start with a rod of large enough dia. and then turn to the largest dia. of the middle section. You could set over the topslide for the tapers. You could then mill the two ends, I would silver solder (braze) the end parts on since I have a propane torch.

The piston can of course be split, or is the teflon ring split?

Thor

Edited By Thor 🇳🇴 on 21/07/2022 06:36:54

I'd make that part from flat steel bar rather than round but there are many ways depending on what tooling you have.

I would also go for the Viton option on the drawings and just stretch the ring over the piston. The original drawings called for graphite yarn which can just be wound around the grove.

Edited By JasonB on 21/07/2022 07:30:10

Yes, that sounds more logical for me because the amount of metal that need be removed will be far less hence saving in time and less wearing of tools and the machines. Furthermore, I just can't figure out any ways to cut out a nice joint between the ring and the rod. There will be steps of some kind there.

The usual way is to file or mill around the outside of the ring and then simply blend that into the shaft by filing. Chances of soldering all three together and getting the bore of the ring true to the flat face of the palm are slim.

This shows how Stew Hart the original designer made that part

Edited By JasonB on 21/07/2022 08:17:29

Back to the original question.

You already have tools. Decide what you want to build. Look at the drawings and list the materials you will need and the bits of material you already have. Find a part that you can make out of the bits of metal you have. maybe put in an order for some more material including common sizes which you will need anyway one day.
As you make it you may see that you need a particular tapping drill that you don't have, or a tap.. So try making another part. Once you have a list of a few things you need that are stopping you progress put in an order.

You have made a start and can just progress without being in too much of a hurry. After all you don't buy all you food for the year in one go in January, so no need to do that for model making.

Oh and start looking for a second hand grinder, You can put a wire brush on one end if you don't do lots of grinding.

I made mine the same way as Jason except I rounded the end by making this tool to hold the piece so it could be rotated against a spinning end-mill.

The rod was turned to make a step fit width and depth the hole drilled in the eccentric rod. The eccentric end was held in place by the mangled sacrificial washer which was turned to match the outer diameter of the ring and drilled to take a bolt tapped into the body of the rod. The whole was held in machine vice such that rotating the eccentric rold caused the end-mill cut a nice curve around the end.

I don't recommend the method and if tried approach with caution! Important that the milling cutter be a small diameter 4-flute type to reduce the risk of a grab, and only tiny conventional cuts taken for the same reason. The sacrificial washer bears the scars of a grab due to me trying a climb cut.

I show the item as an example of a tool made to achieve a purpose - to quickly machine mill round ends rather than manually filing them to shape with buttons or whatever. The tool did the job quickly and accurately with a good finish, but definitely a walk on the wild side. Having tried the experiment, I concluded the risk of this tool damaging me and the job is too high for routine use. This example was educational rather than practical, but I often make simple tools, jigs and fixtures to facilitate cutting.

Stewart's engine is a good beginner build because it has a few parts that make you think and develop new skills. I found the design to be a good balance of not too difficult and achievable challenges. Can all be done with a small mill and lathe, and the mill isn't essential.  It maintained my interest throughout.

I remember my first encounter with BMS. Did it mean Bright Mild Steel or Black Mild Steel? On this engine either will do, but Bright being pre-machined saves time unless it warps due to a cut unleashing rolling mill stresses... Doesn't happen often fortunately.

Dave

Edited By SillyOldDuffer on 21/07/2022 20:42:47