when driving large goods vehicle do you still have to double de clutch.if so do you do it under braking to?

Question

i know at one time you used to have to double de clutch when changing gear in lorries.with new gearboxes about didnt know if you still had to.also do you still pull off in 3rd gear leaving gears 1&2 for steep inclines

Answer 1

you don't need to double clutch any more and yes you can set off in third

Answer 2

This is such a difficult question to answer.

Syncromesh is a device which uses friction cones to speed gears up, so that as they slide into engagement with the clutch depressed, they don't "crunch" into gear.

In reality, due to the heavyweight nature of the gears required in a truck, this makes gearchanges very slow as the "baulk-rings" rub against each other to decelerate or accelerate the gears before the dog-clutches engage and the gearlever slides into place.

I was brought up on "crash gearboxes" which didn't have syncromesh at all, and I still prefer them, due to realtive speed and ease with which gearchanges can be made if the double de-clutch technique is used. In fact, there was a way of double-declutching which only pressed the clutch once!

The technique was to ease off the throttle to the point that the engine was neiher driving nor slowing the vehicle, and then slip the gearlever into neutral without clutch. Then you let the gears speed up or slow down, still without using the clutch, but adjusting the engine-speed on the throttle. When you knew that the engine and gearspeeds matched, you then pressed the clutch and slipped into the next gear of your choice . So you were effectively double-declutching, but only actualy pressing the clutch once.

With some modern trucks which retain a manual change and a clutch pedal, the above technique is very useful, because it actualy helps reduce wear on the syncromesh cones and makes gearchanges a bit easier.

In most trucks, there are two gear switches in addition to the actual gearlever: one for high and low gear range, (No's 1-4 and 5-8) and one for "split" gears (each gear either high or low)....a total of 16 forward gears and two reverse gears.

In the old days, some trucks had more than one gearlever to do this job, one for High/Low overall range, one for the main gearbox, and sometimes a third to get a split-range. It could get quite complicated, and for those who drove an old Scamell; very physically exhausting. Double de-clutching was an art in itself, and the only way of making smooth progress.

In recent years, various other types of gearboxes have been used; among them the Eton "twin-splitter." A lovely gearbox with the fastest gearchange in the business, the actual gears on the stick represent 3 "speed ranges," and a toggle switch selects 3 gears within each speed range using a twin-splitter box arrangement. Because the box has a free-wheel machanism, you just lifted off the throttle (or eased the revs up or down), flicked the toggle, and the gears would automatically engage very quickly. Then you would go up the box in a series of stepped ranges, each time toggling through the speed-range 1-2-3 before going to the next speed range and moving the toggle back to 1 again. Once on the move, and once you had mastered these lovely gearboxes, they were an absolute joy to drive, but unfortunately, many drivers couldn't understand them and didn't like them.

Nowadays, most new truck are automatic, which makes life boring.

However, just for fun, I'll tell you my favourite truck when it comes to gearchanges, which is a Leyland-Daf. It's a lovely gearbox to use normally, but when I drive them, I only use the clutch to set-off from a standstill.After that, I use no clutch at all, and just slip the gears out on a neutral throttle, let the revs rise or fall to where I want them, and then just slip into the next gear. It's the same as a double-declutch, but without clutch, if you see what I mean.

There's some a bit satisfying about travelling 200 miles, and only pressing the clutch once when I drive the length of a motorway at night.

I do the same thing in my own car, and the gearbox has now done 156,000 miles and sounds as sweet now as it did when I got the car new.

Finally (at last), the point about low gear starting. The important thing is not to overload the clutch on a big vehicle, and with a full load, it is best to just get the vehicle moving in 1st gear, and then very quickly move to the next. With an unladen truck, a 2nd or low 3rd gear start is more normal.unless it is a steep hill start.

Sorry to write at such length, but it's all a bit complicated, and I hope I've given you the information you require.

Bring back crash gearboxes!

Answer 3

No you don't have to double clutch in modern trucks, most manufacturers say you should always move away from the stationary position in 1st gear, but then miss any gears you don't need.

For instance I regularly go from 1st to 4th

Answer 4

depends how many gears you have, i had 16, started in 4th or 5th. now they teach you that gears for going and brakes for stopping modern trucks are semi or fully automatic, chooses the right gear for you

Answer 5

welcome to the 21 century most are automatics now
its easy peasy