PM Research Engine number 2
Contents
PM Research Steam Engine, Model Number 2
I purchased this steam engine kit, and could never figure out how to fixture (hold) the main body on my little Sherline mill. A recent you tube video by Tom Lipton, showing what he calls his "mini pallette" I realized that was the ticket. I made mine from cast aluminum (Mic 6) plate and drilled all 75 holes with the HAAS, but couldn't figure out how to tap them (since been resolved), so I spent about three hours hand tapping all 75 holes. The end result is a general purpose fixture plate that I expect to have many more uses for then just holding the main body of this steam engine.
Assembly diagram
Parts list
- Frame, casting, Qty. 1
- Flywheel, casting, Qty. 1
- Cylinder, casting, Qty. 1
- Bottom cap, casting, Qty. 1
- Head, casting, Qty. 1
- Crank, casting, Qty. 1
- Crank shaft, 1/4" diameter cold rolled steel, Qty. 1
- Piston Rod, 1/8" diameter brass, Qty. 1
- Connector, 5/16" square brass, Qty. 1
- Short bushing, 3/16" diameter cold rolled steel, Qty. 1
- Long bushing, 3/16" diameter cold rolled steel, Qty. 1
- Pipe nipple, not included in kit, Qty. 2
- Piston, 1/2" diameter brass, Qty. 1
- Cap screw, 5-40 x 7/8", Qty. 1
- Cap screw, 5-40 x 1/2", Qty. 1
- Cap screw, 5-40 x 3/8", Qty. 8
- Set screw, 5-40 x 1/8", Qty. 1
- Nut, 5-40 steel, Qty. 1
- Flat washer, 1/8" inside diameter, steel, Qty. 2
- Spring washer, 3/16" inside diameter, steel, Qty. 1
- Piston ring, teflon, Qty. 2
- Gasket, paper, Qty. 2
- #3-48 Hex nut, brass, Qty. 1
Tolerances
Linear dimensions
- Fractions, tolerance +/- 1/64" (0.015625")
- 2 place decimal, +/- 0.010"
- 3 place decimal, +/- 0.005"
- 3 place decimal for mating parts, inside dimensions, - 0.000" -- +0.002"
- 3 place decimal for mating parts, outside dimensions, - 0.002" -- +0.000"
9 June 2015
I performed the start of the machining operations on the main body casting, part number 1, this evening. Spent about 1.5 hours on these operations.
During the process I made two mistakes, I drilled the lower two vent holes 5/32 instead of 3/32 (did I mention my eye sight isn't what it once was). I have a way to fix this, but it will be a bit more work then I should have had to do. I also noticed a few small casting defects, which I may use some lab metal epoxy to fix, but they are only a cosmetic issue.
To fix the hole sizing mistakes, I plan to turn down some aluminum rod to slightly (0.001") larger then the 5/32" hole and heat the main frame so it expands. This will allow me to insert the slightly larger rod, and clamp it tight when the frame cools. I will then redrill the bottom two holes 3/32". Beyond that there are only three more things that need to be done to this part. I need to drill 2 inlet holes in the top of the part to intersect these four vent holes, I need to drill oil holes for the two shaft holes you see in the front of the part, and I need to drill two holes in the feet for later mounting for display and operation.
Next part will be the flywheel.
11 June 2015
I machined the flywheel today at lunch, the whole process taking about an hour. As you can see in the following photographs, I mounted the raw casting in a four jaw chuck and indicated both the inner rim to get it centered, and the face to ensure it was as perpendicular as possible to the bore.
After performing the above set-up, which took about five minutes, I started by facing the flywheel rim, and hub.
After the facing operating I set-up a dial indicator so that it would read 0.000" when I had the tool as close to the chuck jaws as I dared. This allowed me to perform the turning operating to reduce the rim diameter without risk of running the tool into the chuck jaws.
After turning the rim to clear all of the casting skin and produce a clean rim, I center drilled, then step drilled to 15/64", and reamed to 0.250". That completed all of the operations that could be performed with that first setup. I then removed the flywheel from the four jaw chuck and placed it on a 0.25" arbor that I placed in a three jaw chuck to allow a facing operation on the opposite side. After this the flywheel is complete except for the drilling of a 5-40 tapped hole at an angle to the bore to allow for clearance of the rim. This set screw will secure the flywheel to the main axle.
17 June 2015
I successfully turned down some aluminum stock to about 0.001" larger then the 5/32" port holes I mistakenly drilled. I then heated the base casting up and press fit these plugs into the holes. I also used some Lab Metal (epoxy) to patch the larger casting defect in the port face. So after doing this, I stopped at the space last night to reface all three surfaces to be in the same plane while removing the ends of the plug and making the lab metal flush with the other surfaces. I then used a pin gauge in the cylinder rotation bore to center my 0,0 on that point and then re-drilled the bottom two ports to 3/32" at a 1/4" deep. I then oriented the jig plate to plce the main body casting vertical. I again established my x-axis centerline from the gauge pin in the cylinder rotation bore and drilled and tapped the two inlet/exhaust ports per the plans. Finally, I lapped the three face surfaces with 400 grit wet/dry paper on a surface plate to clean up the machining marks and provide the best possible sealing surface for the cylinder.
The only remaining operations to be performed on the base casting are the drilling of the two oil holes for the two bores, and to drill the two mounting holes in the feet of the casting. These operations needed to occur without the piece mounted as it was to the jig plate, so they will be conducted in another session.
18 June 2015
I lapped the front face of the base casting with 600 grit silicon carbide paper as a final prep on these these surfaces. After that, I put the first of two coats of Rust-o-leum enamel primer on both the base casting and the flywheel on all non-machined surfaces.
19 June 2015
I drilled and tapped the set-screw hole on the flywheel for a #5-44 set-screw since I don't own the tap (or set screws) for #5-40. The machining on the flywheel is now complete. After completing this operation I put the first color coat of enamel on the fly wheel and the base casting. After letting that dry for a few hours, I drilled the two oil holes for the base casting. I then remounted the base casting onto the fixture plate to allow me to use the Bridgeport and its DRO to accurately drill the two mounting holes in the feet tomorrow.
20 June 2015
I drilled the two mounting holes in the feet of the base casting. The machining on the base casting is now complete. I put the second color coat of paint on both the base casting and the flywheel.
22 June 2015
I put what may be the last coat of paint on both the main body casting and the flywheel. I think they turned out reasonably well, though under the right lighting you can see the repairs that I had to make to the casting.
I also started to machine the cylinder head for the engine. I first roughly centered the core hole of the casting using a four jaw chuck then faced one end lightly to allow me to reverse it in the chuck and seat it well against the face of the chuck. Another light facing of the opposite end, I will bring the cylinder head to length after I have bored the main cylinder. I am having to use a long, thin boring bar to fit in the core hole. This is causing a bit of a tapering (~0.005") in the cylinder, but as soon as I widen it enough to fit a beefier boring bar I will switch to that. Which will hopefully reduce/eliminate the taper I am getting.
24 June 2015
Well the new boring bar arrived this afternoon, and what a difference it made. The thinnest part of the shank on the original boring bar was only 0.212" in diameter, while the new one is 0.313" in the same spot. Granted I could not have used the new one to start enlarging the bore since it would not have fit, but one pass with the new boring bar and all of the measurable taper was gone. Even better when I adjusted the crosslide to remove 0.020" in diameter, I could then fit the pin gauge that was 0.020" in diameter larger, but not one that was 0.021" larger. This allowed me to dial in the precise amount I needed on the cross slide dial to bring the bore to it's final size of 0.500". I brought the bore to 0.490" and will let it rest (and cool off) until tomorrow night. I will then remeasure the cooled off bore and adjust for one final cut to bring it to size. The other nice thing about the stouter boring bar is that chatter has been eliminated, which means I am getting a great finish and do not need to lap the bore. I also took a measurement of the current length of the cylinder at 1.219", which means I will need to remove 0.094" to bring it to its specified length.
25 June 2015
Finished the bore on the cylinder. It came out 0.500. It allows the 0.500 gauge pin to pass freely, but the 0.501" gauge pin will not even enter the mouth. No detectable taper. The ends were faced to bring the length to 0.129"
