Date: Wed, 22 Jul 2009 14:51:41 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: was: Friction, any extra wear 'n tear?
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re
He said the state wants us to be in gear with the clutch pedal depressed.
that's completely bogus ....
I believe you that he said it, but there is no sensible reason to do what he
says.
It's unsafe even. Your foot sips off the clutch .................and the
engine doesn't stall....
your car would go right out into the traffic crossing in front of you.
and it's stressful on the mechaisms in general - I said more on that in
another post a while ago.
as far as the drag of the oil in the trans ( with trans in neuatral )
it it's zero degrees outside, and you've got 85W90 gear oil, and it's not
warmed up ........yes , big affect.
On a warm summer day ..........with a warmed up gear box .........almost no
affect.
and .....speaking of that .....
whether or not to hold the clutch in for starting.
I never do ..........with one exception.
IF it's super super cold ............say 10 degrees F ............with the
clutch pedal up in neautral, you are aksing the starter motor to turn over
the engine and push the input shaft through that cold thick oil - so in that
case, yes, hold down the clutch pedal to start.
Otherwise, I perfer clutch up in neutral for all normal starts.
I would think that having the clutch pedal pushed in, which on all 'normal'
push to release pressure plates ( there are pull to release pressure plates
here and there in the auto world ) - you are putting an end load on the
crankshaft .....
which might add loud to the starter's job .......or even wear on main
bearings/ thrust bearing more than you need to have happening.
switches have been added to the clutch pedal of modern cars for safety
reasons. Very nice.
there is one big disadvantage to that ......besides the minor penalties I've
mentioned......
and that is ...............if you just need to get your van or car to move
20 feet to the side of the road .......
but it won't start ..........
with a normal manual trans and no clutch pedal switch, you can just 'drive'
it on the starter.
just put 'er in gear, let out the clutch, grind away. The car will move
nicely. Since starter motor torque is so high.......use 2nd gear, not
first. Third might even work. On level ground you could drive a whole city
block easily, on just the starter if you had to.
If there is a swtich on the clutch pedal, you can not do this handy
emergency manuever.
On late 80's era 4 X 4 Toyota Pick-ups ......
there's an override switch on the dash. If you hold that button, it'll start
without holding in the clutch pedal - handy sometimes.
what fun !
scott
www.turbovans.com
----- Original Message -----
From: "levi hawkins" <b1levi@YAHOO.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, July 22, 2009 2:21 PM
Subject: Re: was: Friction, any extra wear 'n tear?
This happens to bring up something I've been wondering about.
I recently was required by the state of Nevada to take a driving test with
one of their inspectors.
At the end of the test I had passed, but he mentioned what I had "done
wrong" during the test: Sitting at a red light with the gear box in neutral
and my foot on the brake.
He said the state wants us to be in gear with the clutch pedal depressed.
Of course I'm not going to change, but my first thought is, wouldn't this
cause extra wear on components? Some of these lights would have you sitting
there for 5 minutes with the clutch in.
I really don't know, but I'm curious if anyone does.
--- On Wed, 7/22/09, Larry Alofs <lalofs@GMAIL.COM> wrote:
From: Larry Alofs <lalofs@GMAIL.COM>
Subject: Re: Friction
To: vanagon@GERRY.VANAGON.COM
Date: Wednesday, July 22, 2009, 4:38 AM
Interesting question, more complex than I thought at first.
With the trans in neutral, depending on the design of the MT, there
is still some frictional coupling between the input end and the out
put end, depending also on the viscosity of the lube. In most MTs I
believe this would tend to make the two ends turn at the same speed as
if it were in high gear (straight thru).
Assuming that the clutch pedal is not depressed, the viscous
coupling in the trans could then either help or hinder the coasting of
the vehicle depending on its speed and the rpms of the engine. If the
vehicle is moving fast and the engine is idling this effect would slow
the vehicle slightly.
If the clutch is depressed, the engine speed is not important.
There will still be some frictional drag as the output end of the
trans turns or tries to turn the input end. The frictional energy
loss at the throwout bearing is not relevant because it is just the
engine vs. the clutch fork.
Now of course if the clutch doesn't release completely.....ugh, too
complicated for this early in the morning.
Larry A.
On Tue, Jul 21, 2009 at 10:55 PM, John Rodgers<inua@charter.net> wrote:
> This came up today.
>
> if one were to coast, and allow momentum to do the pushing - which
> scenario would have the greatest resistance against rolling.
> 1) Coasting with manual tranny in neutral. clutch released
>
> or,
>
> 2) Coasting with Manual tranny in neutral, clutch pedal depressed.
>
> Curious minds, and all that........
>
> Thanks,
>
> John Rodgers
> 88 GL Driver and proud owner of new Altimax RT's 205/70/R14 XL 98T (grin!)
>
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