Hercules Restoration: A New Webster Magneto

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

| December/January 2016

  • Circa-1923 Hercules Model F
    Photo by Peter Rooke
  • Igniter bracket as purchased.
    Photo by Peter Rooke
  • Worn eccentric pivot pin.
    Photo by Peter Rooke
  • Roller worn through.
    Photo by Peter Rooke
  • Adjustment arm with broken spring.
    Photo by Peter Rooke
  • Setting the rod for the new eccentric pivot pin to run true with a spacer to set the needed offset.
    Photo by Peter Rooke
  • The bent moving electrode shaft.
    Photo by Peter Rooke
  • Reaming the hole for a new shaft.
    Photo by Peter Rooke
  • Base of the electrode with bent shaft cut off and a spigot turned at the end to fit into new shaft.
    Photo by Peter Rooke
  • Checking the taper of the new igniter shaft using engineer’s blue dye.
    Photo by Peter Rooke
  • Cutting the key slot on the new igniter shaft.
    Photo by Peter Rooke
  • The completed repair to the moving electrode.
    Photo by Peter Rooke
  • The oval mounting hole in the igniter bracket.
    Photo by Peter Rooke
  • Boring the oval hole in the igniter bracket true. Using the boring bar ensured a round hole.
    Photo by Peter Rooke
  • Testing the fit of the bushing to the igniter bracket before pressing it home.
    Photo by Peter Rooke
  • The finished advance/retard assembly.
    Photo by Peter Rooke
  • Machining the trip arm journal.
    Photo by Peter Rooke
  • The completed pivot assembly.
    Photo by Peter Rooke
  • The first stage in making the wedge was milling a slot in a piece of steel. A steel plate was then brazed to this.
    Photo by Peter Rooke
  • Milled piece with plate brazed to form square “hole” for the wedge.
    Photo by Peter Rooke
  • Finished wedge after shaping and filing.
    Photo by Peter Rooke
  • Two blocks of steel welded together for pushrod clamp block.
    Photo by Peter Rooke
  • The clamp after rough shaping and with pivot pin hole drilled.
    Photo by Peter Rooke
  • The completed clamp, with pivot pin and spring retaining tab.
    Photo by Peter Rooke
  • Almost ready for assembly, the completed trip arm and clamp.
    Photo by Peter Rooke
  • The original coils wouldn’t supply the desired 8-1/2 volts so new coils were sourced and installed in the Webster magneto.
    Photo by Peter Rooke
  • The original coils wouldn’t supply the desired 8-1/2 volts so new coils were sourced and installed in the Webster magneto.
    Photo by Peter Rooke
  • New metal poured into bearing rod cap to repair broken bearing locating stub and hold bearing in place.
    Photo by Peter Rooke
  • Cleaned piston and connecting rod assembly ready for engine.
    Photo by Peter Rooke
  • Fitting the piston after oiling the piston and cylinder wall.
    Photo by Peter Rooke
  • Cam gear and gear wheel showing timing arrow and marks.
    Photo by Peter Rooke

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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