Douglasmotorcycles.net
General => General Douglas Discussion => Topic started by: Dave on 01 Jun 2007 at 22:01
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Rossco kindly sent in the following information and photos.
Hi all. The mounting pads under the BTH magy on the D33, that were missing were made up from old tap washer stems. Regards Rossco.
(https://www.douglasmotorcycles.net/aa-files/images/rossco/2007/mag-pads-1.jpg)
(https://www.douglasmotorcycles.net/aa-files/images/rossco/2007/mag-pads-2.jpg)
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The originals were not all that much more substantial. Just a turned steel tablet with an integral peg top and bottom to locate in the holes of the crankcase and the magneto base. Used on all the S6 and variants from 1930 through 1934. The replacement 'Aero' models used a cast aluminum riser, that was less prone to chaffing and wear. This is exacerbated if the magneto is not clamped firmly and allowed to shimmy about.
Here the case looks to be in good shape, with just the original spot-face cutter marks denoting where the tablets register.
The idea of the tablets was to create an air gap and thermal break between the hot crankcase and the magneto. If the wear into the alloy case of magneto housing is significant such the proper registration and location is destroyed, then you are better off replacing the individual tablets with a larger sheet shim, drilled to receive the locating pegs.
-Doug