Engines > From Plans
Muncaster Grasshopper - Work in Progress
kvom:
I decided to start a new thread for a build as opposed to keeping on with the discussion of the plans. As I mentioned in the other thread, I will be using Julius' original SW parts plus any modifications needed to use the two piece beam in V2.
As I wrote in the NAMES thread, I'm going to adopt Cliff Roemmich's idea of using honed hydraulic tubing for the cylinder. I have ordered a piece of 2" OD x 1.5" ID tube from Bailey Hydraulics of Knoxville TN. Since the OD is close to the OD of the cylinder itself, this tube will be the cylinder body and not a sleeve. I had to order the minimum 24", enough for 4 engines. If anyone else wants to share, I paid $90 for the tube, so a 6" piece would be 22.50 plus shipping. I'll do an evaluation as soon the piece arrives. FWIW, this is the 2nd smallest tube they have, and the smaller is 1.875" OD.
kvom:
My piece of tube from Bailey arrives this afternoon, so I was able to take the first baby steps in this project. Here's the raw tube as shipped:
I cut off ~ 5.25" with the bandsaw, then mounted on the lathe. Faced both ends and applied a chamfer to remove the internal burr, then a second face/chamfer to length. Finally a pass with some Scotch Brite to remove the external mill finish.
The OD of the tube measures 2.002" and the ID 1.502".
I also ordered a piece of 6061 4" round bar on eBay from which to make the beam mounting bracket. I noticed that this bracket attaches to the top flange of the cylinder via 6 M4 screws, which means that the matching holes in the flange must be clearance and the holes in the bracket tapped. But the other two hole in the flange (those over the port block) must be tapped in order to secure the matching holes in the cylinder cover.
kvom:
More work on the cylinder. First, I turned down each end to 1.75" diameter for a length of 8mm. DRO makes this mix of metric/imperial relatively math free. The tube sticks out a bit more than I like, but I don't have a live centerlarge enough. I used the nose of a large drill chuck to align it.
Now for the bottom flange, I used a length of 3" 6061 bar to turn down the outer diameter to 65mm and the inner to 51x4mm. Then opened up the center with a 1-3/8" endmill that I've never otherwise used. Then boring bar to creep up on a sliding fit to the cylinder tube.
Then parted off and faced flange to 4mm thickness. The mounting holes will be drilled and tapped later on. Then I repeated the operations for the top flange, that differs in being 70mm diameter.
With both flanges done, the assembly was clamped on the Bridgeport's vise, and a flat machined for mounting the port block. Julius drew the port block with a concave inner surface to match the outer surface of the cylinder, but I feared being able to get an air tight fit that way. The two steam ports were then drilled with a 5/32 endmill.
kvom:
This weekend's shop time was occupied with the port block. Again I used imperial measurements but needed to retain the metric spacing of the mounting holes for the steam chest. I started with a piece of 6061 5x2x1 inches and whittled it down to this:
Posing with the cylinder:
I still need to drill the exhaust outlet and tap the mounting holes 8-32.
Gas_mantle:
Looks good, a lot bigger than I expected :)
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