Web page contents, chart concept and design, engine designs and all information contained here is copyright Littlelocos Model Engineering © 2003, 2017
Handy Lathe Charts
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for the Home Metal-Shop Hobbyist
& Model Engineering Projects
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The following is a collage of photos of the final days of assembly and completion. These pictures were taken January 2004 before and during the Cabin Fever Expo. Since then, initial bugs have been worked out, a diffuser has been added to the rear section, and the drawings and instructions have been finished. To see other progress shots, scroll down, and then go to the next page.
The cylinder is held in a clamping fixture in the rotary table, located with a Morse-taper pin. Relief is being cut for the mounting screws. At this time, the top of the cylinder is still flat. The cylinder is bored, finned and parted off in the first set-up in the lathe.
The clamping fixture in the background securely holds the blank end of the cylinder. The Morse-taper pin in the foreground is used to quickly set up and maintain the centering of the fixture in the rotary table. (The end of the pin is center-drilled, making for quick centering of the table in the mill using a dead-center instead of a drill chuck in the spindle.)
One clamp is left holding things together between cylinders. Note the end of the Morse-taper pin in the center.
The fins are cut in the top of the cylinder using a profile-shaped parting tool in the lathe. The cylinder is held using an expanding arbor clamped in a large round of aluminum machined to give the right offset. The whole thing is backed up with a live center to keep things stout.
Here we have the cylinders threaded and counter-sunk for the glow-plugs. The next several pages will show the set-ups needed to get at some of the tricky angles and offsets needed at the top end.
The setup to machine the cylinder to receive the glow plug and the valve chests (set 120° apart and 30° from vertical) seemed to grow vertically, incorporating a tilting table, a 6” rotary table, and a mounting fixture for the cylinder. Leave enough room for a drill chuck in the mill, and the 18” vertical capacity is just about spent. A cleaner set-up would be to use a tilting dividing head. This set-up was also used to machine a setting fixture needed to center the set-up later.
The cylinder is mounted to the fixture, centered by a 3/4” boss and retained by 8 each 2-56 screws. A 1/2” end-mill is used to machine the countersunk recess, followed by drilling and tapping for the 1/4”-32 thread for the glow plug.
Note: This is the fourth time the same mounting fixture has been used— crankcase, ring gear, main bearing ring, and now the cylinders. It is centered on the rotary table with the Morse taper plug.
After machining the glow plug recesses, the entire set-up is rotated by 42° clockwise prior to machining the cylinder to receive the valve chests and the exhaust rocker stanchions. The set-up is rotated 42 counter-clockwise to machine the intake rocker stanchions. Here an adjustable square and angle plate are used to set the angle.
Once the angle is set, the setting fixture is attached to the top of the cylinder-holding fixture to “find” the set-up with a dead center mounted in the milling machine spindle. The setting fixture imitates the inside of the cylinder and has a center-drill indicating the location of the glow plug and valve chest locations. This is necessary since the top cylinder fins prevent any external references.
Remember to slot each stanchion after drilling and tapping the cylinder for them and before tearing down the set-up or losing the reference point. This will ensure that the slots are centered. After all stanchions are slotted, cross-drilling is performed by cutting a slot in a piece of scrap steel just wide enough (and thick enough) to allow the stanchion to be steadied. Center drill, drill and ream 1/8”, holding each cylinder in the fixture with hand pressure only.
Here, all four cylinders have had the stanchions installed, slotted, and cross-drilled. The tops of the stanchions are rounded with a file and three 5/16” filing buttons. They are retained on a temporary shaft using model airplane wheel collars.
Finally, we are to the point of installing the valve cages. The tool in the foreground is made to fit over the valve guide and into two holes in the top of each cage. It is held in a 1/4” socket and nut driver to firmly screw two guides into each cylinder. High-temperature Loctite 620 is used to fix these into place.
Here are two cylinders after installing the valve cages. The bronze valve seats and the hole for the glow plug can be clearly seen.
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Once the valve cages are installed, each cylinder is mounted to the rotary table, and centered up for drilling the intake and exhaust passages. The cylinder on the left was drilled and tapped to receive the intake and exhaust pipes. The one on the right was machined for a flange connection and tapped for two 2-56 screws. The flange connection makes for a much neater appearance and was chosen for the design. The drilled and tapped connection will be used for the single cylinder prototype. This completes the cylinders.
The cast iron piston rings are turned accurately to match the cylinder ID and bored to the correct thickness. These will later be broken, stretched over a special fixture and heat-treated.
Each piston is accurately turned in the lathe and parted off. Then a clamping fixture is made to mount on the Morse Taper Plug. A button just smaller than the ID of the piston skirt is turned, center-drilled and parted off. This is used to clamp the piston into the centering fixture for cross-drilling and reaming the wrist pin holes.
The rotary table is set up on the angle plate to cut the clearance recesses for the valves into the top of each piston. Again, the clamping fixture is used; however, this time the piston is registered in the slot of the fixture with a 3/16” pin. The fixture is held in place with the mill clamp. The “C” clamp tightens the fixture, securely holding each piston for machining.
Each piston is accurately turned in the lathe and parted off. Then a clamping fixture is made to mount on the Morse Taper Plug. A button just smaller than the ID of the piston skirt is turned, center-drilled and parted off. This is used to clamp the piston into the centering fixture for cross-drilling and reaming the wrist pin holes.
This picture gives a better idea of the size of the Master Rod.
A scrap of aluminum is drilled to match the holes in the Master and Slave Rods. The rods are then pinned to the plate and clamped before rounding the ends to shape.
The Slave Rod is pinned to the plate for rounding the ends. Here the first end is rounded and the second one is still “in the rough”.
Most turning operations have been completed on the crankcase. Now for the cylinder flats. The part is fixtured by turning a groove in the end of a 2-1/2” Rod of Aluminum, facing off the end, then carefully boring a 1/2” hole for the Morse-taper pin. All turning and milling operations are set up with the pin, enabling the part to be transferred from the lathe to mill and back.
This is the end view showing the internal turning needed. The crankcase is one-piece, loaded from the back for assembly.
After all of the horizontal and vertical milling and drilling is completed on the crankcase, the whole set-up is transferred to the angle plate set over either 5° or 10° to face, drill, and ream the holes for the exhaust and intake tappet bearings.
Here is another view of the same setup giving another angle. After this, the crankcase is transferred back to the lathe to machine the angled area in front of the tappets. While in the lathe, the backplate is temporarily attached to the crankcase and then faced to a final finish. Once these operations are complete, the crankcase is (finally) parted off of its fixture. The fixture will be re-used for other parts.
NOTE: The above two photos show a set-up needed to lay the valve tappets over by 5°. This was later dropped and the tappets run perpendicular to the Crankchaft. In the final version, use the same set-up minus the angle plate.
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