bazhart
Barcelona
- Joined
- 20 May 2009
- Messages
- 1,343
911uk MODERATOR EDIT: Moved from a different thread.
Funny you should mention Norton's - because I am writing a book about my motorcycle exploits for which the first issue was to find a way to make the gearbox of a fellow students 600CC dominator more suitable for racing (as the lower gears were too low to use on track and we couldn't afford a full C/R gearbox changing all 8 gears). We found a way to make the 4 gears closer ratios by making and changing just the sleeve gear ratios - just 2 gears to manufacture (because of the sleeve gear system and top always being 1/1). We made a sleeve gear with a ratio to speed up the layshaft so all the internal gears (1st, 2nd and 3rd) would then be higher - and third was then closer to 4th because 4th was always locked out at 1/1. 3rd to 4th became the same as a Manx ratio and it was this invention that enabled me to start Barton Motors and initially manufacture and sell those gearbox conversions World-Wide - leading on to the Sparton's (that were fastest at the TT and 1st and 2nd at the North West 200), the Phoenix fours (that won several TT's, The Silver Dream racer (for the film), several upgrades for Barry Sheene's Suzuki (including a 6 speed gearbox to replace the TR500 5 speed box and making his RG500 into a 650 (later adopted by the factory), the carbon fibre framed Armstrong 350 engine (that won the British Championship for several years and obtained podiums in full GP's etc.
Sorry - a bit off subject but while on Norton's and compression ratios - we fitted huge inlets and carbs and very high compression pistons to it - but then it only ran well if it was much too rich (because we could not influence a change in ignition timing throughout the range in those days and running too rich slowed the burn speed with H/C and made it faster and with more torque).
You are right about the studs - the reason they broke was because the only place not sealed off from the outside atmosphere was where the head joined the cylinder so moisture could creep in and slightly corrode the stud just there.
Then corrosion created a notch so "notch metal fatigue" set-in and because the cross sectional area gragually reduced just there so the load/unit area increased and each time the engine was run, got hot and then got cool again the thermal expansion of the cylinder and head stretched the stud increasing the tension in it creating fatigue cycles.
Eventually the cross sectional area could not withstand the cylinder head torque that had incr3eased of course as the cylinders and heads expanded and when they broke you could clearly see the typical metal fatigue polished rings where the section had gradually cracked and the smaller area where it finnaly broke- text book stuff.
Plastic coating largely overcame the problem but also keeping cars in heated garages for most of their later life also helped.
Baz
Funny you should mention Norton's - because I am writing a book about my motorcycle exploits for which the first issue was to find a way to make the gearbox of a fellow students 600CC dominator more suitable for racing (as the lower gears were too low to use on track and we couldn't afford a full C/R gearbox changing all 8 gears). We found a way to make the 4 gears closer ratios by making and changing just the sleeve gear ratios - just 2 gears to manufacture (because of the sleeve gear system and top always being 1/1). We made a sleeve gear with a ratio to speed up the layshaft so all the internal gears (1st, 2nd and 3rd) would then be higher - and third was then closer to 4th because 4th was always locked out at 1/1. 3rd to 4th became the same as a Manx ratio and it was this invention that enabled me to start Barton Motors and initially manufacture and sell those gearbox conversions World-Wide - leading on to the Sparton's (that were fastest at the TT and 1st and 2nd at the North West 200), the Phoenix fours (that won several TT's, The Silver Dream racer (for the film), several upgrades for Barry Sheene's Suzuki (including a 6 speed gearbox to replace the TR500 5 speed box and making his RG500 into a 650 (later adopted by the factory), the carbon fibre framed Armstrong 350 engine (that won the British Championship for several years and obtained podiums in full GP's etc.
Sorry - a bit off subject but while on Norton's and compression ratios - we fitted huge inlets and carbs and very high compression pistons to it - but then it only ran well if it was much too rich (because we could not influence a change in ignition timing throughout the range in those days and running too rich slowed the burn speed with H/C and made it faster and with more torque).
You are right about the studs - the reason they broke was because the only place not sealed off from the outside atmosphere was where the head joined the cylinder so moisture could creep in and slightly corrode the stud just there.
Then corrosion created a notch so "notch metal fatigue" set-in and because the cross sectional area gragually reduced just there so the load/unit area increased and each time the engine was run, got hot and then got cool again the thermal expansion of the cylinder and head stretched the stud increasing the tension in it creating fatigue cycles.
Eventually the cross sectional area could not withstand the cylinder head torque that had incr3eased of course as the cylinders and heads expanded and when they broke you could clearly see the typical metal fatigue polished rings where the section had gradually cracked and the smaller area where it finnaly broke- text book stuff.
Plastic coating largely overcame the problem but also keeping cars in heated garages for most of their later life also helped.
Baz