Matt
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Re:Crash box - 2007/01/02 07:41
I have never heard of a crash box before. I'm not sure if it's the same thing as a dog box. This is all a major simplification, but it should give you an idea of what's going on.
In a gear box you have atleast 2 shafts. one comes from the engine and the other goes to the wheels. There are all the gears in different paired ratios that make up your speeds, with one of the pair on one shaft, and the partner meshing on the other shaft. The gears on the input shaft are free spinning on bearings, not connencted to the shaft at all. Beside every gear is a slider on a spline on the shaft. this slider can engage something on the side of the gear that will effectively connect it to the shaft. When you move your shifter back and forth, your sliding these around.
A dog box is a gear box that uses 4 or six big hooks, called dogs, (this is a major simplification) that catch other dogs to engage gears. This differes from a syncro box that uses hundreds of tiny brass teeth that have to aligh at the correct rpm before a gear will engate. The syncro box makes for very smooth shifting, but you have to wait for a fraction of a second for the gears to engage, and you must use a clutch (or match your engine speed to your gear speed perfectly).
Because of the large amount of space between the dogs, of you shift fast enough, the hooks can engage without ever needing the revs to match very well, and without needing a clutch. In the end the dog box gives you faster shifts, and you never need to move your feet off the gas and the brake. Very fast.
There are also sequential shifters. Instead of the normal "H" esqe pattern of a manual gear box, you simply push up to move up a gear, or pull down to go don a gear. The shifter spins a drum in the gear box, and the drum does the work to move the sliders that engage gears.
After all that writing, I hope one of thoes is a crash box. It might just be a weak gear box paired to a strong motor, but I typically call thoes gernades.
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