Clas­sic Cob From the shed

Old Bike Australasia - - CONTENTS -

A Wa­ter Cooled Tri­umph

Well known pre-unit Tri­umph guru, Paul Dempsey from Ren­mark, South Aus­tralia re­cently sent me pho­tos of an­other spe­cial he has built. It is a 1949 T100 in a 1956 swing­ing arm frame fit­ted with a wa­ter-cooled cylin­der head. He ac­quired this from a fel­low in Ade­laide who at one stage was in the RAAF and sta­tioned in Syd­ney. An­other ser­vice mem­ber had pur­chased this en­gine in Syd­ney about 1960 when it was fit­ted in a small rac­ing hy­droplane. When Paul told me about this it re­minded me of an en­counter I had around the early 1980s. I got to meet an el­derly chap liv­ing at Forster named, from mem­ory, Norm Cooper. He told me he had been a work­shop fore­man for many years at a mo­tor­cy­cle deal­er­ship in Went­worth Ave, Syd­ney which I seem to re­call, but not cer­tain, may have been A.P. North. He was friendly and very in­ter­est­ing to talk to. He in­sisted, rightly or wrongly, that the only bal­ance fac­tor to use in any en­gine was 50%. He would ask for a 20 cent coin and draw a se­ries of cir­cles on pa­per and then write in var­i­ous bal­ance fac­tors and show which way the crank­shaft would have a ten­dency to dis­tort out of bal­ance. There was no men­tion or con­sid­er­a­tion as to what frame the en­gine was to be fit­ted into. He balanced both of the en­gines used by the late Graeme Gates in his twin Nor­ton, and as any­one who saw him ride knew that he revved the en­gine very hard. Cooper told me about a mo­tor­cy­cle en­gine he built where he ma­chined the crank­shaft from the axle of a rail­way car­riage and the alu­minium bar­rel from the cen­tre por­tion of a vari­able pitch air­craft pro­peller. He used a 250 BMW head and fit­ted it into a prewar Tri­umph frame. How­ever now get­ting back to Paul Dempsey ac­qui­si­tion, Cooper used twin pre-unit Tri­umph en­gines in a hy­droplane that he raced on the Ge­orges River, Syd­ney in the early 1950s. He burnt out sev­eral ex­haust valves so he made a wa­ter jacket around the head which then solved the prob­lem. I think he told me that he re­lied upon con­vec­tion in some form to cre­ate a wa­ter flow. Paul has fit­ted a ra­di­a­tor mounted up­wards of the head which would al­low for the heated wa­ter to rise and the colder to sink down­wards to­wards the head. I am un­able to say if oth­ers un­der­took the same mod­i­fi­ca­tion as Cooper but there is a pos­si­bil­ity that this could be the same head that he used all those years ago. Just when you think that this ma­chine might be unique, I made a phone call to an­other Tri­umph guru, Bryce Find­lay and learned that he has a sim­i­lar en­gine with a wa­ter jacket around the head on a 1951 650 Thun­der­bird. So per­haps af­ter all it was a com­mon mod­i­fi­ca­tion back when im­pro­vi­sa­tion was the or­der of the day.

Swel­ter­ing at Goul­burn

The Goul­burn Swap Meet held Sun­day the 21st Jan­uary saw 254 traders which was about the same num­ber as last year. How­ever the buy­ers were down to about the 1100 mark no doubt due to the very un­com­fort­able tem­per­a­ture which in the high 30s. There were some good buys around at com­pet­i­tive prices. The com­mit­tee has iden­ti­fied sev­eral ar­eas upon which they can make fur­ther im­prove­ments. Gra­ham Sin­clair had one of the Aus­tralian-pro­duced RTV Vin­cent en­gines which he had sold prior to the swap. When started up on Satur­day af­ter­noon and Sun­day morn­ing it sure made a racket. For sale was a 1922 500 In­vin­ci­ble JAP be­lieved to be one of only 4 or 5 as­sem­bled in Swan­son St, Mel­bourne, and be­lieved to be the only one still in ex­is­tence. There was also a 1914 500cc Pre­ci­sion made in UK but as­sem­bled by A G Heal­ing in El­iz­a­beth St, Mel­bourne. Both of these ma­chines are for sale and fur­ther de­tails can be ob­tained by con­tact­ing Graeme Sin­clair 0418 711 405. See you next is­sue, Pete You can get in touch with Pete at... cob.smith@big­pond.com or call (02) 6553 9442 af­ter 7.00pm

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