Quote:
Originally Posted by rc'Z
O-cha it is difficult to read, but read the first three words:
When shifting up on a non-synchroniser equipped vehicle, the clutch pedal is pressed, the throttle is released, and the gearbox is shifted into neutral. The clutch pedal is then released. As the engine idles with no load, the RPM will decrease until they are at a level suitable for shifting into the next gear. The driver then depresses the clutch again and shifts into the next gear. The whole manoeuvre can, with practice, take no more than a fraction of a second, and the result is a very smooth gear change.
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Seriously read the rest of your own article or actually evaluate what it says, you're so lost it's funny.
Quote:
Originally Posted by MVF4Rrider
We're only talking 1st to 2nd gear changes as being an issue. Remember the difference in crank speed vs. gearbox speed is biggest in 1st gear (5th is 1:1 and 6th is overdriven). So it would seem a solution is to slow down the actually shift lever movement into 2nd's gate (fractionally) to allow time for the crank speed to reduce thereby minimizing the speed differential between the crank and gearbox.
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You have arrived at the correct idea of a solution through incorrect logic. I misunderstood what you meant by crank vs gearbox speed at first, but the rest is still flawed a bit too. It's less of s retort as a better explanation of what you're trying to convey.
There are basically three free spinning parts in the driveline, the engine (and for ease of explanation) the "front" of the gearbox and the "rear" of the gearbox. The rear always moves with the wheels, the engine obviously always with the engine and the "front" which is what is free when the clutch is depressed and what the synchros are acting on to change it's speed. The actual gear change itself occurs between the "front" and the "rear" of the gearbox and the engine itself has nothing to do with it.
The 1st to 2nd shift is "special" because it's the
widest ratio and what this means is that the "front" of the gearbox needs to slow down the most out of any gear change in order to meet the new speed of the "back" of the gearbox. This is because the 1st gear set is spinning at less than 1/4 of the speed of the engine, but the second gear set is spinning at a much faster at at less then 1/2 the speed of the engine if my memory serves me on our ratios. This means that in order for the "front" to meet up with the new gear set it must slow down a great deal by comparison with the other gears.
This slowing (or speeding up in the case of a downshift) is what the synchros are responsible for. As explained the 1st to second shift is what makes the most use of the synchros. So it needs the most time to adjust the speeds, which is why the idea of slowing down the shift is correct. The same effect can be done by shifting smoothly however since synchros don't like to be mashed together and that is what most people do in the 1st to second shift.
I'll edit some later for correctness of numbers, can;t be bothered right now.
This also highlights why it is ridiculous to double clutch an upshift like this as the "front" of the gearbox slows down much faster then the engine itself (so is more quickly able to be engaged then the rpms are to be at the new speed of the next gear) and you would just be slowing down the speed in which you could shift gear regardless of all the extra movements and steps you have to take.