Exhaust pipe length

[Black Flash]

I am building a new exhaust for my Comet special, using a DBD34 Goldstar silencer (now is the time for the purists to shudder and turn away in disgust!!), because I really like the look of this silencer . it will finally be tilted upwards by about 15°, so the frontpipe needs this little upward and outside kink. My question now, does anybody know how long the exhaust pipe and/or complete exhaust should be for good performance?

Bernd Schmitz

 

[nkt267]

goldie silencer

Not sure on the lengths..My first Comet back in '69 had a goldie silencer fitted in the normal vincent mountings and it went like'stink'.The only trouble was that living in London it could still be heard over a mile away.What a lovely sound.

 

[nkt267]

I've looked at some old Vincent technical sheets and they don't seem to list any pipe/silencer lengths for singles.there are lenghts and pipe diameters for twins, maybe this would be a place to start looking.
Sheet 4D:-'A straight through extension pipe can be made up or ordered from the works and should extend to a point just behind the rear axle. A variety of racing exhaust pipes are listed in the Spares Book, a megaphone will reduce power a lower revs,and is not suitable for this type of engine. in any case the valve timing is not one which answers well to a megaphone. 2"(50.80mm) diameter pipes,44"(111cm) long,will give an increase in maximum power at the loss of flexibility below 4,500 rpm. these pipes fitted to twins reduce the ground clearance on righthand bends and they are recommended for sprints and fast circuits only. For short circuits 1 5/8"(41.27mm) diameter pipes 54" to 56" (137 to 142cm) long are recommended; it should be bourne in mind that separate exhaust pipes preclude the fitting of the standard kickstarter and that an alernative crank is not supplied.'
So sayeth the Works

 

[Black Flash]

I can well rember visiting a cobweb run in Kings Newton many years ago. somebody turned up there with a very nice Comet special using a BSA frame with cut off front downtubes connected to the headbracket and a Vincent RFM. It was really a nice bike, but most impressive was the look and the incredible barking sound (roar) of the goldie silencer, goose pimples raise now when I think about it! Since that day I swore whenever I have a Comet, it has to be this silencer (amplifier). Thank you very much for the data, at least I have an idea now and I have plenty of tubes, so I could make two or three versions and try out.

 

[TouringComet]

Sheet 4D:-'A straight through extension pipe can be made up or ordered from the works and should extend to a point just behind the rear axle.'
So sayeth the Works

Wow, maybe I can pass off this one my father had made back in the '50s as a genuine 'works' one, and sell it on ebay!

I think I'll put it on tomorrow, and go for a ride. I just love the way it sounds.