Author Topic: Douglas Bantam expansion chamber / muffler  (Read 4649 times)

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Offline Daren W Australia

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Douglas Bantam expansion chamber / muffler
« on: 27 Jul 2006 at 09:45 »
Hi Does anyone have Douglas Bantam expansion chamber/muffler or drawing or photos as I want to get this bike going for the 100 years rally Regards Daren
too many dougli not enough time!

Offline Chris

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Re: Douglas Bantam expansion chamber / muffler
« Reply #1 on: 27 Jul 2006 at 18:18 »
There were two designs of expansion chamber for the Bantam. There is one long flat one that then only uses short pipes to the silencers. I think that was the early design. The later one is a very short box shape that plugs up onto the two parallel outlet ports of the cylinder. This design then uses much longer pipes to the silencers. I used this latter design on my 1935 restoration. I made a wood pattern for the casting and a plaster of Paris core box to make the cores used in casting the chamber. I will try to photograph these and provide overall dimensions. Most of the dimensions are largely dictated by the cylinder outlet ports and the size of exhaust pipes to be used. Having cast the chamber I set it up on my large bench drill with a home made boring bar entered into the No 2 morse taper of the drill spindle. I was then able with great care to bore the inlet pipes to match the diameter and distance apart of the cylinder ports and likewise, at 90 degrees and further apart, with not quite such accuracy required, the outlets for the pipes. Chris.