Quote:
Originally Posted by Nick JM
Ok. I am afraid I am going to show my ignorance.
How does a dog box actually work? My understanding is that providing the engine sped is momentarily reduced the downshift can be engaged without use if the clutch and to some extent one can almost preselected. I am not an engineer and have also never used a dog box but can one of you engineering types explain in layman' terms what happens; how you use it; and if it's that great why wasn't it used in period?
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Mmmm, that's a challenge. Early gearboxes required user to double de-clutch in order to synchronise gear speeds and facilitate crunch free change. Each gear spun independent of it's neighbours. The early form of automatic synchroniser was the dog clutch type, it used toothed 'dog rings' between the gears that locked them together as the gear was moved along the shaft. Very crude, abrupt and still noisy. Then the cone synchromesh was invented, which gradually by friction slowed the gear down to correct speed for engagement. Quiet and best option for road cars. Downside was wear, requirement for correct oil so that friction level was as designer intended, and ability to be overcome if gear change too aggressive.
So 'dog boxes' were still popular for competition / race cars, and are still used today where regs allow. (Hewland for instance.) But for FIA, if a production car was homologated with cone synchros, that's what you use.......
Not sure any suggestion of 'pre selection' is correct, but you can change gear without using the clutch- in fact changes can be smoother that way. Downside is that the 'dogs' wear and have to be replaced regularly. Ask any historic Hewland user!
Any help?
Whoops, see that Terence and my posts have overlapped!