Locally-made Short Circuit frames
Back in the 1950s and 1960s the Hunter Valley was the hub of Short Circuit racing in New South Wales, with venues such as Heddon Greta, Salty Creek, Hillview at Muswellbrook and Jubilee at Cessnock. So it was to follow that a significant number of Australian and state titleholders would come from these areas. The likes of Dave “Sputnik” O’Brien, Norm Fraser, John Rumford, Jack Davies, Keith Davies, Herb Jefferson and others spring to mind. So it was that if anyone was going to construct Short Circuit frames it only followed that it would come from this area. Newcastle identity Bill Rawlinson built around 7 or 8 frames which were ridden by riders such as Kevin Fraser, Jim Rawlinson and Keith Davies.
Davies tells me that he used one around 1966 with a B33 BSA engine. These frames had a 19-inch rear wheel and initially a 21 inch front but later ones had 23 inch front. He used various small sized brakes and laced his own wheels. Davies tells me that these frames tendered to be rather stiff to ride and later he preferred the handling of the Hagon frames he later rode. Rawlinson used T45 Chrome Molly tubing and incorporated his own ideas. He made the fuel tanks and the forks, which were different in that he used conventional springs instead of the large rubber bands used on the Hagon.
Jason Spruce has sent me several photos of a Rawlinson frame that he purchased recently in the Newcastle area. Finished in a similar blue to the dominant Hagons, it could easily be mistaken for an imported product rather than one made in the hot bed of Short Circuit racing in Australia. turned the ignition key off and heard a “clack” type noise from under the fuel tank. The next thing was that the machine caught fire. Others came to his assistance but the fire could not be put out until a fire extinguisher arrived. The rider was of the opinion that when he turned the key off the spark plug fired and ignited back through an open inlet valve to the flooded carburettor. This machine was fitted with a Boyer ignition and had extensive damage.
Recently talking to an enthusiast in the Forbes area he told me that he had a 1969 650 Triumph also fitted with a Boyer ignition. Around last December he rode the machine to his front gate. Switched the ignition key off, opened the gate and turned back to the bike which by then was on fire. He had no water nearby and no other means to extinguish the fire. The machine was totally destroyed and was a write off. He was at a loss to understand what had happened but when he told me about it I related the story to him about the Rocket 3. He then formed the opinion that this was the same cause as to his problem as he had only just started the engine and more than likely there was sufficient petrol around the carburettor to feed the fire.
Seeing as how I am not familiar with these electronic systems I need to get an expert opinion hence I contacted Steve Kelly at Tri Spark Ignitions, Adelaide. He advised that some of the older Boyer boxes were set up to switch the coils on all the time except when sparking. This creates a risk of the danger of making a spark when you switch off the ignition key. Boyer systems vary and some would not have the same fire risks as others. They are not very clear about explaining the evolution of the design which they have altered many times over many years. So Steve could not say which systems are more at risk.
The Lucas Rita systems all have the risk of sparking when the key is switched off. They also leave the coils on all the time so they have the same risk as the older Boyer systems of sparking when the key is turned off. The risk of this sort of fire can vary depending on the air cleaner fitted. The more enclosed it is the safer it should be. Velocity stacks would be a higher risk for fire.
The Tri-Spark Ignitions only turn on the ignition coils just before making a spark so there is no spark when the key is turned off. This feature not only eliminates the risk of fire but reduces the power consumption and heating of the coils.
See you next issue, Pete