On Sun, 26 Nov 2006 12:32:45 +0000 (GMT), "Dave Plowman (News)"
<dave (AT) davenoise (DOT) co.uk> wrote:

That's a good argument *for* putting a planetary gearbox, rather than
a synchro. one, behind a friction clutch. I'd love to know what I've
missed that would tell me why it's not done.
--
Dan.

In article <gq2jm214tndqlqtsg93nl6rfsi13tqv1qj (AT) 4ax (DOT) com>,
Dean Dark <ddrake (AT) comcast (DOT) notthis.net> wrote:
Probably because you've already got 'clutches' in a planetary box which
can do the same thing. Didn't the Model T Ford use this principle? Later
pre-select boxes of course used a fluid flywheel for starting from rest.

--
*When cheese gets it's picture taken, what does it say?

Dave Plowman dave (AT) davenoise (DOT) co.uk London SW
To e-mail, change noise into sound.

On Sun, 26 Nov 2006 13:18:26 +0000 (GMT), "Dave Plowman (News)"
<dave (AT) davenoise (DOT) co.uk> wrote:

Then why do you *have* to have a torque converter? Oh dear, I'll
never understand this...
--
Dan.

In article <1f8jm2tstqr7f8v6oc8lndedbd5cvfin8u (AT) 4ax (DOT) com>,
Dean Dark <ddrake (AT) comcast (DOT) notthis.net> wrote:
It has several functions. First it acts as a 'clutch' when starting from
rest. Next it acts rather like a continuously variable gearbox by allowing
the engine speed to exceed its output speed by up to around 2000 rpm and
converting most of that speed into extra torque at lower output RPM. Not
all though, as it gets hot in doing so. ;-) It also - and crucial for most
autos - cushions the actual gearchange.

When autos had two or three ratios, the torque multiplying feature was
crucial to reasonable performance - albeit at the expense of economy.
Boxes now have up to what? 8 ratios, so this part isn't much needed. So
many just use it for starting off and each gearchange, locking it out of
action via an extra clutch for most of the time.

--
*One of us is thinking about sex... OK, it's me.

Dave Plowman dave (AT) davenoise (DOT) co.uk London SW
To e-mail, change noise into sound.

On Sun, 26 Nov 2006 09:18:31 -0500, Dean Dark <ddrake (AT) comcast (DOT) notthis.net>
wrote:


A fluid flywheel is not the same as a torque converter. A TC will direct oil
flow onto a fixed stator that in turn directs oil flow to a turbine attached to
the gearbox input. whereas a FF is simply a spinning container of oil that
inertia eventually makes the outside tank oil viscosity turn the vanes of a
"spinner" connected to the output to the gearbox. David Brown tractors used to
have this arrangement and a similar arrangement although not fluid was the
magnetic flux flywheel (clutch less) setup designed jointly by Jeager and Smiths
and fitted to the once famous Hillman Minx and I think Simca or Renault cars in
France.

Here endeth the last lesson or rather useless information.


Sir Hugh of Bognor

The difference between men and boys is the price of their toys.

Intelligence is not knowing the answer but knowing where and how to find it!

Hugh Gundersen
hsg (AT) h-gee (DOT) co.uk
Bognor Regis, W.Sussex, England, UK

Unlike a clutch, it is not possible for a torque converter to completely
disengage so there would always be some torque present during shifts which
would wear out the synchros in very short order. That's also the reason
that a standard transmission will outlast an automatic by a factor of two
or three. If you want to keep your car for more than 300k miles I would not
recommend an automatic.

"Dean Dark" <ddrake (AT) comcast (DOT) notthis.net> wrote

On Sun, 26 Nov 2006 16:12:36 +0000 (GMT), "Dave Plowman (News)"
<dave (AT) davenoise (DOT) co.uk> wrote:

I've always had a pretty good grasp of the mechanics of it all,
including how the TC works and the subtleties of what it does.

I was kind of thinking that torque multiplication rather than the
'disengaging' effect of low torque transmission at low RPM was the
underlying reason they were first used, and I suppose there was then
no real reason to change things later.
--
Dan.

On Sun, 26 Nov 2006 16:24:40 GMT, "Jack" <grampajack (AT) verizon (DOT) net>
wrote:

That's completely the opposite of my quandary!
--
Dan.

In article <cdjah.7401$IW2.5435@trndny03>,
Jack <grampajack (AT) verizon (DOT) net> wrote:
Which goes against the findings of most large organisations who now
specify autos even for things like light vans. The beauty of an auto is it
is virtually driver proof. And remember you don't get a synchro
transmission without a clutch, so the two should be considered together
when assessing life. Not many will get anything like 300k miles out of a
clutch.

--
*What am I? Flypaper for freaks!?

Dave Plowman dave (AT) davenoise (DOT) co.uk London SW
To e-mail, change noise into sound.

I agree completely with Dave that the most prominent virtue of the automatic
transmission is that it is much more 'foolproof' than the manual
transmission and if your situation requires it by all means buy an
automatic. That's why commercial operators do it - many of their drivers
have no respect for the hardware. On the other point, if a clutch goes out
it costs you $150 and a Saturday spent under the car whereas band clutch
failure in an auto will cost you about 20 times that amount and will often
result in scrapping the vehicle. Automatic transmissions have their place -
it's just not in any of my cars.

"Dave Plowman (News)" <dave (AT) davenoise (DOT) co.uk> wrote