Double declutching
Discussion
Slowly Slowly said:
I don't see "extending the duration of a gear change as undesirable" at all
The reason it's undesirable is that the driver has their hands and feet and (to a lesser extent) mind occupied for longer. So their ability to brake, steer and accelerate is compromised for longer, and typically at a point when driver workload is already high.Being able to drive without the clutch is commendable - I've had to do it myself (not in an 18 wheeler though!) and it's good fun although rather stressful if you have any mechanical sympathy - but not something I'd recommend doing in a vehicle you care about. The damage this will cause to the gearbox will outweigh the wear and tear gains you're claiming for double declutching by several orders of magnitude.
If you want to take the long route, or learn a difficult technique that might come in handy some day, then go ahead by all means. No other justification is necessary other than the fact you want to. What I take issue with is you claiming that the technique you're using is superior to the normal sensible and easy approach. It isn't; it's inferior.
GreenV8S said:
Slowly Slowly said:
I don't see "extending the duration of a gear change as undesirable" at all
GreenV8S said:
The reason it's undesirable is that the driver has their hands and feet and (to a lesser extent) mind occupied for longer. So their ability to brake, steer and accelerate is compromised for longer, and typically at a point when driver workload is already high.
I find that if you practice a particular skill, whether it's driving or not it becomes easier and so you can devote your attention to something else because the thing you practiced becomes automatic such as DDC.GreenV8S said:
Being able to drive without the clutch is commendable - I've had to do it myself (not in an 18 wheeler though!) and it's good fun although rather stressful if you have any mechanical sympathy - but not something I'd recommend doing in a vehicle you care about. The damage this will cause to the gearbox will outweigh the wear and tear gains you're claiming for double declutching by several orders of magnitude.
Unless the skill you have learned gets you home without calling a recovery firm out(with a truck you have to disconnect the propshaft) or gets you off the HS on a wet night were as we know 40% of motorway accidents happen, maybe my skill has saved my life (if someone ran into my vehicle on the HS they would probably be the ones that died) at some timeIf you want to take the long route, or learn a difficult technique that might come in handy some day, then go ahead by all means. No other justification is necessary other than the fact you want to. What I take issue with is you claiming that the technique you're using is superior to the normal sensible and easy approach. It isn't; it's inferior.
Slowly Slowly said:
When you say "normal sensible and easy approach" what you really mean is your way, I didn't realise you were taking issue with it, all I can say is I've never heard of the SDCHT before.
What I'm taking issue with is the adoption of unnecessarily slow and complicated techniques without a good reason. With respect I think that's what you're doing. If you're applying DDC for the sake of it then that's your choice, but be honest and say so instead of trying to claim that there are good reasons for doing it. There's far too much misinformation spouted about DDC and H&T already without adding to it the confusion. Slowly Slowly said:
When I drove from J1 M6 to Wandsworth without a clutch it was in a loaded 16 tonner, I went off J1 and back on again stopping on the down on ramp as I came to a stop it stalled, thats when I realised my clutch was knackered, It was now stuck in gear engine not running, I couldn't (at first) get it out of gear.
Normally I would have had to phone for recovery which would take me to the nearest base to tranship, very time consuming I'm sure you'd agree, Instead I used my knowledge and may I say skill to get it to it's destination, about 100 miles, try it sometime in a car, then try it in a loaded 16 tonner.
Presumably you got the stationary truck moving by allowing it to roll downhill down the on ramp in neutral then selected a gear once rolling. But did you not stop anywhere in the next 100 miles (except on downhill slopes)?Normally I would have had to phone for recovery which would take me to the nearest base to tranship, very time consuming I'm sure you'd agree, Instead I used my knowledge and may I say skill to get it to it's destination, about 100 miles, try it sometime in a car, then try it in a loaded 16 tonner.
Not sure how firmly your tongue is in your cheek, but you could start it by engaging gear and moving off on the starter motor. Or as we did at Le Mans, jack back end up, engage gear, start engine, drop jack - ensuring of course all the disbelieving French are cleared to the pit lane exit as there would be no choice other than exit!
ph123 said:
Not sure how firmly your tongue is in your cheek, but you could start it by engaging gear and moving off on the starter motor. Or as we did at Le Mans, jack back end up, engage gear, start engine, drop jack - ensuring of course all the disbelieving French are cleared to the pit lane exit as there would be no choice other than exit!
I could have rolled it down the ramp then blipped it before selecting 2nd but I knew that at some stage I would have to start it on the level so I turned the engine off, put it in 2nd(I think) then turned the key and did a kangaroo start then went up the box picking the right revs and upping the revs when changing down.There were 27 sets of lights down the Egdware road, by driving steady I managed to get them all except 2 on green, when I stopped I had to perform the Kangaroo start again.
I must have saved the company a small fortune in recovery costs, another truck and driver plus sorter loaders plus delayed goods and missed connections in London, so any wear and tear to the gearbox dingle dongle bearings was insignificant.
BertBert said:
Slowly Slowly said:
Yeah right.
Is that agreeing or disagreeing?Bert
The boss thanked me for getting the truck in on time so perhaps he doesn't know I've worn his baulk ring, I don't think Lewis Hamilton would be bothered about his BR if he was 2 laps away from the checkered flag and had a knackered clutch.
Slowly Slowly said:
BertBert said:
Slowly Slowly said:
Yeah right.
Is that agreeing or disagreeing?Bert
The boss thanked me for getting the truck in on time so perhaps he doesn't know I've worn his baulk ring, I don't think Lewis Hamilton would be bothered about his BR if he was 2 laps away from the checkered flag and had a knackered clutch.
I don't geddit!
Bert
PS this might help... http://en.wikipedia.org/wiki/Synchromesh#Synchroni...
Edited by BertBert on Monday 16th July 15:20
BertBert said:
Slowly Slowly said:
BertBert said:
Slowly Slowly said:
Yeah right.
Is that agreeing or disagreeing?Bert
The boss thanked me for getting the truck in on time so perhaps he doesn't know I've worn his baulk ring, I don't think Lewis Hamilton would be bothered about his BR if he was 2 laps away from the checkered flag and had a knackered clutch.
I don't geddit!
Bert
PS this might help... http://en.wikipedia.org/wiki/Synchromesh#Synchroni...
Edited by BertBert on Monday 16th July 15:20
R_U_LOCAL said:
If you do it properly, there's no reason why changing gear without a clutch should cause any damage to the gearbox whatsoever.
If you do it perfectly. It's very sensitive to the slightest error matching the revs though, amd not something I'd recommend practicing on a vehicle you care about.R_U_LOCAL said:
If you do it properly, there's no reason why changing gear without a clutch should cause any damage to the gearbox whatsoever.
I am not sure that the perfect change is possible time and time again. When I was shown how to do it, the technique involved (albeit slight) pressure on the gearlever against the gate. The revs were taken past the right point and the pressure applied as the revs are allowed to fall back. As the right revs are found the gear slips in. This naturally wears the gearbox more as it's the baulk rings of the synchro that are engaging early.The technique was taught to me an ancient truckie who used it on crash boxes. There is of course no synchro to wear. The technique with a synchro box might be different of course.
Bert
BertBert said:
The revs were taken past the right point and the pressure applied as the revs are allowed to fall back. As the right revs are found the gear slips in.
That's essentially the same technique I'd use for a clutchless gear change on a synchro box, but applying very light pressure until the gear lever is felt to yield slightly, then pull it in positively before the revs have drifted too far. Done right I'm sure there's no great harm doing this a few dozen times in an emergency, but I suspect the gearbox would quickly get tired of it if this technique was used every day. Unless you have a computer monitoring the relative speeds and snicking the gears in perfectly every time, this is a technique that is IMO inevitably going to lead to increased gearbox wear.GreenV8S said:
BertBert said:
The revs were taken past the right point and the pressure applied as the revs are allowed to fall back. As the right revs are found the gear slips in.
That's essentially the same technique I'd use for a clutchless gear change on a synchro box, but applying very light pressure until the gear lever is felt to yield slightly, then pull it in positively before the revs have drifted too far. Done right I'm sure there's no great harm doing this a few dozen times in an emergency, but I suspect the gearbox would quickly get tired of it if this technique was used every day. Unless you have a computer monitoring the relative speeds and snicking the gears in perfectly every time, this is a technique that is IMO inevitably going to lead to increased gearbox wear.
I think that's right.The ability to perform clutchless gearchanges is a useful trick to have in your toolbox in case of need, but to me it wouldn't make sense to regularly be making gear changes on that basis. Unless you can execute them perfectly it seems bound to increase the risk of breaking something, or causing additional wear.
Best wishes all,
Dave.
MarcusL said:
In relation to the above discussions and the difficuty of H+T has anyone tried left foot braking (rally style) - now theres a recipe for disaster...
it takes a while to get the sensitivity to do it. I've never real found a huge advantage by doing it (probably because I'm no good at it!), other than spin correction in a RWD car or 'braking with the left foot' (which is a different thing) to save time when going into fast corners (when racing of course!).Gassing Station | Advanced Driving | Top of Page | What's New | My Stuff