The Electric Starter and Housing, Part 2


In Part 1, I showed the sequences which generated a snug, bullet-nosed pod to contain the Speed-300 and clutch mechanism. Here, I will show one way to create elegant supporting arms which can be attached and detached in 45 seconds from the engine.

With the pod complete, I needed to engineer the supporting arms. A tripod arrangement I decided would be best for rigidity (important) and appearance.

To this end, I enlarged the Wren 54 side-view print to 2X scale, and verified the correct dimensions. Onto the center-line, I added a scaled, pencil drawing of the pod, which can be faintly seen next to the spinner nut. From there, it was a simple matter to generate a 2X scale outline of a pod arm, which needs to be produced as a set of 3.

  Scaling the drawing back down to 1X, I simply cut out the pattern and glued it to one of three aluminum blanks of 1/4" thickness. Rather than make 3 separate pieces, I decided to drill a series of 4 lightening holes which I then reamed to .1875". Using these holes, I inserted 2, 3/16" pins to hold them all together for milling. This ensures 3 identical pod arms and reduces the work required significantly.
  After milling and drilling, the sandwich of pod arms is shown here next to the pod itself.

The leading edge of the arms is rounded to fit the milled slots which I cut in the pod. Attachment is 2 ea. 3-48 SHCS per arm into the body of the pod.

  Firmly attached, the pod/arm assembly is chucked and the ends of the arms which fit onto the outer case are bored to size, and with the cross-slide set at 34 degrees (the print-generated angle) the arm interiors are nicely profiled.
  Once attached, I reinserted the motor and tested the unit. It worked perfectly!
All that remains is to route the wires through a slot planed into the interior of the body (no cheesy wires to disturb the bullet nose), down through one of the arms, and out at the junction of one of the lower arms and the case outer..

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