Greg Brillus Racer

Bill Thomas

Well Known and Active Forum User
VOC Member
Never knew how Hot H.T. was.
Playing on the bench with a twin mag', Thinking of putting on Ron's Comet, With a wasted spark or earthing one lead, With the end of the lead laying sideways to earth, Just driven with a drill, The end of the lead was melting !, Strange.
Done some more miles on my Special, With the" Trick " "D" Distributor, Twin spark coil, Wasted spark, No dist' Cap !!, Len's idea , Not mine, Thanks Len.
Goes well , Starts well, 50 mph to 70 ish in top = Nice Squirt !!. Cheers Bill.
 

Canning

Forum User
Non-VOC Member
Big thanks to Greg for a massive weekend at the National Historic Titles. We had significant engine trouble, but Greg got us running and competitive.
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Flo

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VOC Member
Hi Greg, Balance is indeed a strange thing. When I first built my Brough replica I had a bad vibration at tickover but after that it was smooth as silk at speeds up to 90mph (never had it faster than that) so I sent the crank off to be balanced, they told me it was at 86% and how come it hadn't shook itself to pieces as they're normally balanced at 42%. I can only assume they were flywheels for cast iron pistons, now it's balanced at 42% it's not as smooth but at least the forks want to stay in place at tickover !!.
Chris.

The engineering 'sience' of the engine/vehicle dynamics is quite well understood nowadays. It is quite involved nevertheless. The excitation is due to the free forces and couples after balancing. The basics of balancing reciprocating slider-crank mechanisms based on assuming constant angular speed have been known since FW Lanchester's work. To analyse perceived vibration the transfer function (frequency and phase response) to handlebars, footrests and seat needs to be taken into account. Additionally the non uniformity of angular speed, which is strongly linked to engine revs, is nessing things up.

Hence either it is some experimental effort and a lot of work or the use of very sophisticated instrumentation and software. At the times when our motorcycles were made none of that was practically available - hence empirical methods ('seat of the pants' development work) and engineering flair were applied in the available helpings.

Personally I believe we have drawn quite a good lot.

PF
 

greg brillus

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Thanks Phil, I have recovered now after an exhaustive few days. Changing cams/followers in the pits at the track is not so easy, but we got a result. The clean up was difficult and a compromise, then the ignition gave us more headaches. The twin spark system had overloaded the condenser/points, and it wasn't till we had replaced all of these that the engine finally ran OK. You feel bad until you look around the pits and see everyone else having difficulties as well. One of my mates who was racing his period 3 Harley engined sidecar managed 3 laps before his carby fell off...............;).
 

timetraveller

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VOC Member
Cams and followers!! Was this due to the fitting of the new high lift cams and, if it is not secret information, what lift was expected? I have had some parts made to give up to 0.5", although they will be installed at 0.45", and I know that they do not foul anything. One of our 'go faster' American cousins has used 0.7" but with a lot of modification to the heads etc.
 
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