Hi everyone.
Here is a little fill in project that I have been playing around with as time allows. I still have at least a couple longer term projects in the works that I’m not ready share yet; but what the heck sometimes a guy just needs to make some chips!
This engine was designed by Henry Essex and was patented in 1902 US 723,660
The engines were on sale around 1905 and were advertised as suitable for running fans, window displays, model machinery, peanut roasters and sewing machines.
Some models had a fan to cool the cold end of the cylinder driven from the engine flywheel; others had a water tank at the cold end. A twin cylinder version was also available.
The engine works on the Stirling cycle principle but is unusual in that the heat is applied to the centre of the engine rather than at one end.
Essex claimed greater efficiency was achieved with this layout.
I built a full sized replica of an Essex hot air fan a number of years ago from Myers castings. I have always desired owing an engine too but the originals are scarce and quite expensive when found. When I discovered that castings were available from David Abbott in England I decided to go ahead and snag a set. I think that he actually pours them to order. They arrived in reasonable time and are nicely made.
Here is a picture of a completed engine from David’s web site AKA Myford Boy. My engine will have a wood base which I believe is more true to the original anyway. I guess shipping the cast base is cost prohibitive.
Here is a picture of the castings as received.
I also decided to purchase the castings for the turntable that goes with the engine.
I decided to start with the Crankshaft Bearing casting. Sorry I got carried away and didn’t take any early on pictures of the machining. This pretty much was chuck it in the lathe and bore the hole for the crank bushings. This will be used to reference most of the remaining machine work. As you can see from the picture of the raw casting there is lots of extra material that needs to be removed; some manually i.e. hacksaw. I mounted the casting in an indexer which allowed me to access multiple sides without changing my setup. After establishing the height of the mounting flange from the crank centerline the screw holes and flange profile were carefully laid out. I needed to establish the piston center line as everything else is measured from that. Once the center was established the profile was machined and the mounting holes drilled using the CNC.
You can also see here that I had previously machined the mounting foot and it is being used to stabilize the casting by clamping to an angle plate.
Next the casting is rotated 180 and the mounting lugs are brought to thickness and also machined back far enough to allow the round head mounting screws to seat properly. This is not called out on the print you just need to make it happen. Here you can see that even after removing quite a bit of material that there is still plenty to go to bring it to the proper shape.
The casting is set in the vice and the round chucking lug is brought to length. This dimension is from the center line of cylinder bore. The previously machined surface was set on the parallel and back figured from that surface.
Using the same set up the CNC was used to machine the opening. No dimensions for this feature on the drawing, you just need to make it look good. Notice the steel slug placed in the bore to keep from crushing the bore.
The next step was to drill and counter sink the hole. There are two bronze bushings that leave a gap in the middle for an oil reservoir.
The bushings were turned and installed, I had to do some figuring to establish the stick out of the bushing on the crank side, this needs to place the crank shaft so the throw is centered in the cylinder bore. This dimension is not on in the drawings, but there is enough information to figure it out.
Except for the mounting screw hole here is the Crank Bearing pretty much complete.
There is a whole series of videos on building this engine which are great! And I think this is the reason there are some missing dimensions on the prints. By watching the videos some of this will become clear.
Do to different equipment sets and working styles everyone does things differently, so while I have watched and enjoyed all the videos I will most likely change the way I go about doing things on some of parts; I guess that I already have.
More to follow,
Dave