Slip Rings

The slip rings are made from two cut sections of copper water tubing supported on a Delrin rod. The rod needs to be turned down to a diameter to provide a snug fit in the copper. Next, the Delrin is drilled lengthwise to fit the camera axle. Axle diameter is 3/8" . This happens in three steps. First a center drill is used to locate the hole. Note that drilling on the lathe is done with the work piece rotating, not the drill. Center drills are short and consequently stiff. They will not "walk around" the end of the work before engaging the cut, as a regular drill bit will do.

After the center drill has made a pilot hole, a conventional drill bit is used to drill out the entire rod to a diameter just below 3/8". To open the bore up to its final diameter, a reamer is used. This reamer is 1/1000" over the 3/8" diameter, providing a very snug fit onto the camera axle.

The redundant ground requires a pointed end on the camera axle. Shown here is the taper being turned on the end of the axle. Five items are set-screwed to the camera axle. (From left to right in the pictures below, the timing pulley, two collars to hold the axle in the bearing, the Delrin rod, and the connector block.) Whenever a set screw is used to hold an item on a round axle, a flat section should be made on the axle, against which the screws are tightened. This step should not be neglected. The operation, performed on the milling machine, is called "flatting the shaft", and the flat spot is called a "flat".

There is a small channel milled along the Delrin so that the red wire can pass underneath, what is in the photograph above, the right hand copper ring.The slip rings are shown here assembled with the brush holder. Judging from the size of electic motors which use brushes of this size, this slip ring assembly could probably carry around 3 amps at 120 volts without overheating. In this application the brushes carry only milliamps.