Build - Wobbler Engine

I started with a large piece of plate aluminum. Here you can see I have marked out a rough piece with layout die. Cutting was done the old fashioned way - with a hacksaw (helpful hint: a bit of tapping fluid on the hacksaw blade makes for an easier cut). This will be cut into two smaller pieces for the frame.

The upper part of the frame: A smaller piece was cut from the larger rough piece, the edges were squared up on the mill, and the piece was milled to the proper size. I then began drilling required holes. Note that the hole on the left was countersunk on the wrong side - fortunately this did not make a difference in the operation of the engine.

The hole in the bottom middle was made so that I could mill out the section on the lower left and leave a rounded internal corner. I did not remove this piece until all other operations (drilling, tapping) were complete - this simplifies work holding of the piece.

The bottom part of the frame ("foot"): This is a simple milled square piece. Two holes are drilled and countersunk from "below" to attach the upper part of the frame with flat head screws. Two smaller holes are drilled and countersunk on the "top" - this will enable the frame to be attached to a wood base with flat head wood screws.

The "locating jig" is made from a small piece of scrap steel.

The piston was made from a piece of brass rod. The rod was drilled and then bored out with a boring tool (shown at left). After boring to correct internal diameter, a small hole was drilled to be tapped later for the connecting rod.

The outside of the rod was polished using emery and crocus cloth, and oil grooves were turned.

A parting tool was used to part off the completed piston (note: before parting was completed, a slight chamfer was cut on the top of the piston).

After parting off, the hole for the connecting rod was tapped.

Connecting rod: A piece of brass rod was milled flat on one end, and drilled for the crankshaft.

Connecting rod: The milled rod was chucked in the lathe and turned down to the required diameter. This was done in stages so that only a short section of the un-turned rod was projecting from the chuck while turning.

Connecting rod: After the required length was turned down, the rod was parted off and then threaded. The square end was touched up lightly with a small file to remove sharp corners.

The cylinder is made from a piece of brass bar, milled to size. The required hole was drilled undersize, and then bored out using a home made boring tool. Using this method, it was not necessary to make an undercut for reaming.

I used the already made piston to size the hole, boring in fractions of a thou increments to get a good smooth fit.

As can be seen from the picture, I did not use any shims in the chuck to protect the workpiece from the chuck jaws. This worked out OK, although there were a couple very minor jaws marks. Since there were also tool marks from the milling, after all work on this piece was completed I polished it up with a emery cloth.

Note: I actually made the cylinder twice. The first time I made it from the same material as the flywheel (thinking it was brass instead of bronze). I couldn't get the pivot pin to solder onto the bronze, so I remade the cylinder from brass. I also made my own boring tool before I remade the cylinder, as the purchased boring tool I used before (brazed carbide) was a bit big for this job. With the newly made boring tool, the cylinder turned out much better the second time.

Once the cylinder was bored out, the piece was chucked "sideways" to enable drilling for the pivot pin. The surrounding face was turned at the same time, to ensure that the face would be square to the pin.

For this operation, I did use a small piece of scrap aluminum to protect the open end of the cylinder from the chuck jaws - definitely necessary.

The vent hole at the top of the cylinder (not shown here) was drilled on the mill.

The pivot was soldered in. A scrap piece of aluminum was placed in the cylinder prior to soldering to ensure that the pin was inserted correctly, and that no solder would get into the cylinder.

Crank: The crank was cut from a piece of stainless steel rod which had been previously drilled with a center hole. Sections were milled out, and the piece was drilled for the crank. The crank shaft and crank pin were also made from stainless steel.

Crank: Sharp corners were eased with a small file.

The spring was wound on the lathe (turned by hand!) around a 1/8" brass rod.

For good information on spring making, look on the links page.

The completed spring was lightly touched up on a grinding wheel to flatten the ends, and was then tempered by wrapping in aluminum foil and placing in an oven for an hour. The tempering was probably not necessary for this application, but it was easy to do and I just wanted to try it.

Flywheel: A friend gave me a large chunk of bronze, so I sawed off a small piece to make a flywheel.

Probably took me 45 minutes to hacksaw this. Some day I've got to get a power saw!

Flywheel: The rough bronze piece was cut to octagon shape with a hacksaw, then turned on a lathe to round it. After rounding, both sides were faced to complete the flywheel.

I also made a press-fit "hub" so that I could fasten the flywheel to the crankshaft with a set screw. I didn't want to drill a set screw hole through the flywheel proper and spoil its appearance.

Here is another view of the completed engine, seen from above.

One last picture.