Clutch Pedaless Shifting 2

[rewing]

Im working on a Hewland NLT transmission and am thinking of removing the hydraulic clutch pedal and trying for all electronic-controlled shifting. Im having trouble finding documentation on the subject. Does anyone know in racing setups how this kind of system works? For example, how might you know the clutch is displaced before the computer shifts? Thanks

 

[waross]

The computer reduces power until there is no pressure on the gears. It then shifts to neutral. Next it matches the engine speed precisely to the gear speed on the next gear. It then shifts the gear into place and then turns control back to the foot pedal. Old time truckers did it by ear without a computer.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[GregLocock]

...and motorcyclists have been doing it since the year dot.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

I still do it on downshifts as you push the gear through faster if you don't have to wait for the syncro, you get less wear and tear and a smoother change. I learned to drive in an A model Ford. It was actually required then.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[rmw]

Bill, I guess that makes me an "old time trucker". I do it on anything that has a stick that I drive. I learned on my first car when I was 17 and the hydraulic clutch slave cylinder had a bad leak (I could usually pump it up enough to jam it into first at a dead stop most times although I did have to crank it in gear often in order to roll off from a dead stop) - up-shift, downshift; whatever.

I had a 4 speed Volkswagen when in college and when I would get a girl out on a date that I knew knew how to drive a stick shift, and especially one whose father had done a good job of teaching her a lot about cars, I would get to a point where I was in tight traffic where I had to do a lot of rapid up shifting and down shifting, all of which I would be doing without a clutch of course when I would ask her, 'what is that third pedal over there on the left for?' with the question being timed for an occasion when a shift or two was required and as she looked at the clutch pedal, I'd make the shifts without it.

Invariably, she'd say something like, well, you have to use that when you shift the gears at which time I'd grab another gear (without it, of course) and answer, no you don't, I just shifted and I didn't use it. Usually, I'd have another shift timed for just about when I finished that sentence too. I got a wide variety of reactions, most of which I enjoyed thoroughly. I don't know what their fathers told them when they got back home and asked about it.

I trained drivers for a church with a coach sized bus with sticks (4, 5, 6, and 7 speeds) which required double clutching if the clutch were to be used, and I often found it easier to teach them how to shift without using the clutch at all, and when they mastered that and the speed matching that it required, then teach them how to use the clutch to make the shifts.

On an 18 wheeler that I once owned that had a 14 speed transmission, in the lower range, the first 5-6 speeds, it was much faster to just pump the fuel pedal rapidly and move the stick through the gear pattern about as fast as you could move it than to try to pump the clutch pedal each time along with it. I taught several "old truckers" who still drive today how to do it.

I've had several people say "well you can't do that in this vehicle" but I haven't found the one I can't yet. For some reason Fords tend to be a little more difficult than the others to shift like this, but not impossible once you get the feel and learn their quirks.

rmw

And PS: The girl whose dad had trained her well to get her oil changed, etc, did come looking for me when I asked her if he had mentioned about changing the air in her tires. She went home and ask him about it. He reminded me of that for years after when I would see him from time to time, but I digress, that has nothing to do with trannies.

 

[waross]

The single axle trucks and buses with a 5 speed main and an electric shift two speed rear end are a no-brainer to shift without the clutch.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[tonyg64]

On WRC cars i have worked with the hydraulic clutch was actuated with a hydraulic actuator which was controlled with a separate ecu. When the clutch had been actuated another hydraulic actuator would then move the shifter to the next gear. This would take place in milliseconds and although controlled by ecu it was important to "time" the actuators to make it perfect. These gearboxes were obviously dog engagment that were capable of very quick shifts, synchromesh boxes will still be at the mercy of the synchro assembly being able to move the oil (between the cones) quick enough to engage.

As a side note when we built gearboxes with a gear lever we would life the gears by eye -as in if they had wear they were changed. When the "auto" box was introduced we had to life the gears with mileage as the dog wear was virtually non existant.

When gear shifting is this quick it almost negates the need to drop engine load momentarily.
ps i was a techy not an engineer so cant give specific timings etc.

Tony