Hercules Restoration: A New Webster Magneto

The Hercules engine gets a Webster type M magneto and some finishing touches.

| December/January 2016

Igniter Bracket

This engine was restored to use a Webster Tri-Polar magneto. I found a well-worn igniter bracket (type number 303M1A) on eBay, recognizing it would require a little work. As usual, once received and examined, it needed a lot more work than anticipated.

It was clear that the advance/retard lever spring, pivot and roller would need replacing. The pivot pin had completely lost its shape with wear, the roller had worn through and the spring on the adjustment arm was broken.

The spring was easy to fix; the old rivets were drilled out, the holes cleaned out and a new spring riveted in place. Fixing the pivot pin was a relatively straight-forward turning task to create the eccentric. Some 0.50-inch diameter steel was set in the 4-jaw chuck, but with a piece of 0.125-inch steel between one of the jaws and the rod as a spacer. This was adjusted to run true, then the opposite jaw to the one with the spacer was slackened so the spacer could be removed. This jaw was then tightened so the steel rod moved across to rest against the opposite jaw. This resulted in the steel rod moving its center by 0.125-inch creating the eccentric cut. The rod was trimmed to length after turning it and holes were drilled at each end for the retaining split pins.

I had an old but serviceable roller in the oddment box, so I used that as a replacement. The hole in the igniter bracket for the pivot pin was distorted, but I left that until later to see if it affected the operation of the trip rod.

When I first tried turning the moving electrode it appeared reasonably tight in the bracket, but on stripping the igniter it was clear this had been achieved by bending it slightly. The first step was to pass a 0.3125-inch reamer through the igniter body to check shaft size. This wobbled, but a 0.343-inch reamer gave a clean hole. A moving electrode shaft would have to be made to fit, which could be done by cutting off the electrode head and brazing it to a new oversize shaft.

The overall length was measured and a spot punch was used to mark the head in precise alignment with the keyway in the shaft. This would help set the alignment for the new shaft. The head of the moving electrode was held in the 4-jaw chuck. Measuring with a dial gauge ensured the section of old shaft near the head was running true. The shaft of the electrode was cut off 0.50-inch from the head and that stub was turned down to 0.1875-inch diameter.


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