Quote:
Originally Posted by Scooby_1970
(Post 472124)
.... why do you have to double clutch?
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To keep this simple, double clutching is used on an unsynchronized manual transmissions. Without synchromesh, you have to mesh the gears yourself. The entire point is to match flywheel speed, input shaft speed and output shaft speed, reducing stress on all the components of the gearbox, and stop power being lost as heat in the clutch.
You are basically doing two shifts, with each gear change. Clutch-move to neutral/clutch move to next gear. If you are downshifting, you will also tap the fuel pedal to increase the rpm to your shift point. You will learn about watching your rpm's while making your shifts. To begin with you are just going to get the basics down. Your clutching is like a half-pedal motion. It is done quick and smooth with gear changes in concert. When done right, it is a fast smooth process. (I'm going to let your instructor beat the basics into you)
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There is a clutchbrake towards the end of clutch travel. This stops the gears from turning so they can mesh at a standstill. You only clutch this deep to engage the clutchbrake, when you are stopped, or you will wear the clutchbrake out. I've driven plenty of trucks with a worn out clutchbrake. If you are stopped, and have a worn out clutchbrake, the gears just spin, and you can't engage a low gear. What I do then is clutch, slip into a high gear which will slow the gears down, then quickly into the gear I need before the gears start to speed up again.
You also learn about progressive shifting. You want to slip through the gears with less engine noise and get the truck up to speed quicker. Running the engine up to peak rpm in every gear wastes fuel and makes more engine noise. You also have more torque at lower rpm's. Progressive shifting saves fuel and equipment wear. The idea is to let more of the transmission do the work, and less of the engine. This takes stress out of the whole driveline. Transmissions shift on a percent of engine rpm, and you actually put the gears closer together when you upshift as early as possible. That spends less time in neutral and more time pulling the load.
It's easy to confuse a new driver in the beginning, so for now just plan to get the basics down, and build your foundation. These transmissions react differently bobtailing, pulling an empty trailer, to various weight loads. Also shifting is much different on flat land vs. hills, or starting out on steep grades. You will adapt to all of this, if you really learn the basics well. The basics is also what you draw on in emergencies, as your foundation becomes your instinct.
Your learniing process will be like progressive shifting. You will learn allot fast in the beginning, and go to the next step quickly. The process slows down with more space inbetween as you gain skills and experiance. A good driver is always learning something new, so keep this in mind when you start out. You are beginning a learning experience that will go on throughout your career. Take things a step at a time, and those first steps are important to learn right, so don't be sloppy. A sloppy driver will not learn skills, as much as bad habits.
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