Looking for some guidance on gearbox options for next seasons racing. I'm running a standard f23 along with a standard clutch. The clutch disc only lasted 3 events before it had to be binned
and 3rd gear got a bit clunky on the last event... I need to up the ante a bit with my gearbox/clutch combo.
For race use commonly people go for a ceramic 'puck' clutch. They don't like to be slipped, but for immediate 'on-off' engagement they are great and can last quite some time in these conditions (inversely they tend to not last long on road cars...). Even more harcore are cerametallic and carbon ones. Very short wear lifespan though.
Choice for an un-sprung clutch hub or a regular sprung hub on the clutch disc can also be for speed/agressiveness of engagement, but keep in mind that an unsprung hub transmits a lot more torque variations and pulses through to the gearbox and the gears tend to not like that long-term. (ditto for fitting unsprung front pulley setups that leave the torque damper out)
What's failing on the gearbox itself? Gearbox oil getting cooked and smelling burnt? Or are you destroying synchro's? Are the gears themselves breaking teeth or (support) bearings on the shafts going?
The first issue can often be remedied with an external electric oil pump and oil cooler rad on the gearbox (usually best to trigger it via a thermostat) to keep the gear oil within it's operating temp. When adding an LSD and especially a plate version this becomes more important as the diff and plates will also be dumping extra friction heat in the gearbox oil now. Perhaps add some ducting to the gearbox case from the bumper or grille area to help cool the case.
Second issue could be resolved with a dog-box, but can in some cases also be remedied with perhaps a different gear shift strategy and more precise rev-matching so the synchro's don't need to do as much work and they can last a lot longer. Not sure about the F23,but sometimes other synchro's are available that may last longer under certain use types (eg. carbon lined)
Of course consistent heel&toe is required anyway to make clutches and gearboxes last under race conditions.
When using a dogbox you definitely need to rev-match, but you also need to be 'firm' and 'direct' with your gear shifts. Dog boxes do NOT like gentle gearshifts. That's when they grind and that quickly wears the teeth on the dog rings to nothing.. Shifting is a lot quicker on a dogbox though than on a synchro setup. That's simply the nature of the beast.
When gear teeth are breaking or support bearings go then (unless running ridiculous power and grip so it's bending a shaft outward and sometimes breaking cases) often it's vibrations/pulses from the engine 'hammering' the gearbox parts into oblivion. Commonly seen on cars with very light weight flywheels, solid/undamped front pulleys and un-sprung clutches. On cars like this it's normal for teams to refurb gearboxes every few races and keep one or two boxes 'standby' as the internals pretty much become consumable at some point. Straight-cut gearsets can help extend the service interval, but they are very NOISY.
Real sequentials are great, but also keep in mind that most of these are definitely high on the 'consumable' and very low on the 'rebuild interval' timescale so just buying and fitting one is not the end of the story but need constant upkeep.
Bye, Arno.
