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awe those clutches • •
Page 46
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r AN OVERNIGHT stop in Aisle recently I was king shop with some other ivers staying at the digs. It is a safe bet that everyone
s done something better, ;ter, more dangerous or more likely than the next when in a lain situation, and I listened the chat with interest.
I have noticed on previous ip-overs that a number of vers from one firm in . rticular always get down to .cussions on driving :hniques before the
-too-short evening is out. I find it enlightening to listen descriptions of the many rthods used by many of my leagues to carry out the -ne operations. If airline pilots irked the same system I adder to think what would open.
Let's take the first step in ving a truck; moving off. Adv this is the worst moment transmission misuse and )-re often than not the engine itarted, clutch pushed out d one gear or another mmed into mesh long before clutch plate has slowed wn sufficiently to prevent mage.
Often, even when the licle is fully freighted, first 3 r is not used to get the lorry motion and the poor old tch gets a hell of a bashing. This is all very elementary, .1 might say, and you are golutely right. But the sad is that the greatest
)portion of clutch failures can directly attributed to misuse. len you sit quietly listening a crowd of drivers discussing totors" this fact does not pear surprising, for many do t understand too well just at they are expecting their 'ides to do.
On this particular evening I 3rd the following )Ianations of the right rthod of using a Ichro-meshed heavy-duty rbox.
The argument started when
one chap said he preferred a crash box because it is easier to :change gear. He obviously did not understand the difference between crash, constant and synchromesh boxes and ,neither, it appeared, did any of the others. His method of gear changing had not changed for the last 20 years and it went like this. "I push out the clutch about one inch, then I move the lever to neutral. Then I let the clutch up and push it down again very quickly right to the floorboards and bang the lever into the next gear:
By this time I was involved, and I asked the question: "Why do you think that is the right _way to do it?"
"I'll explain," he said, and he passed on the following .information. "The clutch has a !brake on it to slow down the eri-617ieTand so if you push the Clutch out too far you can't get the gear-lever into neutral.
"Now," he went on, "when I de-clutch the next time I have to put the clutch brake on hard to stop the gears clashing and move the lever with a lot of force."
What he said is complete nonsense, of course, in many respects. First, there is no need for a clutch-brake or stop on a synchro-box.
Secondly, a clutch-stop slows the clutch friction plate and input shafts of the gearbox, not the engine.
Thirdly, if you use a clutch stop properly, you do not double the clutch, ie let the clutch up between the two gears, because the reason for doing that is the same as the clutch stop, to slow the friction plate down, and you can slow it much quicker if you do not recouple the clutch to the spinning mass of the engine.
Lastly, you should never use a lot of force on a gear lever; it is not necessary because when, and only when the dogs have lined up, the mesh will occur .quite easily.
By this time I was acting as the discussion's chairman, and
asked the next chap to describe what he thought was the right method. His .explanation was quite simple: "Clutch out and change as quick as you can," he said.
I asked if he used a lot of force. "Oh yes,he came back, "you have to on a synchro-box, don't you?"
But the fact is — you don't. The synchro clutches do the job of preventing the dogs clashing with each other and the harder you press on the gear lever the greater the load you put on the synchro clutch. If in doing so you also jam the dog faces together you get a baulk condition and the dogs will not mesh. A lighter pressure on the lever allows the synchronisation between the mating dogs to occur and the meshing comes easily and cleanly.
Forcing the synchro is not only extra effort for the driver but causes excessive wear on the synchromesh cones.
The next candidate I asked said quite simply: "I don't use the synchromesh, I double de-clutch all the time."
"Don't you use it on hills?" asked, and he replied, -Yes, sometimes, but I still
double-clutch as well."
Like his friends this last min did not really understand ho4 to use the synchromesh box 1I its best advantage.
Double de-clutching is perfectly OK provided that when the clutch is engaged i neutral you have no load on Ilhe. gear lever. And that you are fact matching your input an output shaft speeds accurate before trying to re-mesh the next higher or lower gear.
If you are keeping load on the lever during the doubling exercise or not matching the mesh speeds correctly then t e synchromesh clutches are being made to do much mor work than that for which the were designed and their live will consequently be severel curtailed.
The villains of the piece ale the operators or vehicle mak s who will not take the time or accept the cost of a good vehicle handling instruction course. Note that/do not sa driving instruction. I've met vast number of drivers who ie acceptable as drivers but sin14 appalling vehicle handlers. After all, when an airplane pital changes from-one type of pll
a 6
to another he gets a conversi n course.
So why do we expect the truck driver to know all about every make of vehicle withou g: similar albeit shorter conversool training period?
Making money is not onlyl being able to earn it; you have to be able to hold on to it as well. Unwarranted breakdo415 are the surest method of losi your grip on it.