On 27 Aug 2005 00:04:13 -0700, "John Martin"
wrote:


Chris wrote:
"John Martin" wrote in message
oups.com...
So, Chris, just where does that extra torque come from?

The increased drag will cause the transmission to wear faster. But it
won't cause it to break. Nor would putting it in a semi, although the
clutch wouldn't hold up.

John Martin


You are basing your thinking that the motor is putting out its entire torque
curve in the bike at all times, which it is not. In order for it to move a
heavier machine more of the torque will be required from the motor at a more
consistent curve. Bike motors are built for HP not torque, although there is
still an inherent amount of torque there, that is not really called upon.

At the extreme, take the driveshaft from the motor and tranny and weld it to
a 20,000lb weight. Then you will see what the consistent full torque from
the motor will do to the tranny. Better yet take the original bike and have
it drag around a 1200lb trailer. Tranny should not last that long.

You are correct increased drag will kill the tranny faster. Drag means more
torque to overcome = more torque being passed through the tranny. In the
same regards weight will require the same. To overcome the weight more
torque will be needed. More torque being passed through = greater
deflection = failure.

Look down a couple of posts, seems like there was even an issue with the
tranny not holding up in a 385lb bike.



You're missing the point. The transmission is the link between the
engine and the drive wheel. It doesn't matter how much the car weighs
- if the engine can drive it, the transmission can handle it. I'm
talking here about failure due to breakage, not to wear. The Norton
gearbox only has to be adequate for the Norton engine, not for the car.
That's what I meant by the weakest link.

Wear, as I said, is another question. The car is heavier and less
aerodynamic than the bike, so the engine will be required to run at a
greater throttle setting. Which will wear the transmission out
quicker. But it will also wear the engine out quicker. Which one goes
first is anyone's guess. Remember, the Norton engine is matched in
performance to the Norton transmission.

You want to take things to extremes, so let's put a truck transmission
in the 1200 pound car. Now what happens? The transmission will be
fine, but the engine will wear out, won't it.

Eric knows, I'm sure, that putting the Norton engine into a car will
wear it - and the transmission - out a lot quicker than on a bike.
It's that simple. He's no more likely to strip a gear in the
transmission, however, than he is to throw a connecting rod in the
engine. Unless that's the typical scenario with the bike as well.

Again, the torque comes from the engine, and is the same whether the
engine is in a bike or a car. If the engine can drive it, the
transmission can handle it. Although both will wear faster than they
will in a lighter vehicle.

John Martin


Not quite right, John. The norton bike limits the maximum torque that
can be deliverd to the rear wheel by the engine. How? By the
co-efficient of friction between the tire and the road, and the weight
acting on it. The Norton engine and transmission will spin the rear
wheel before it will break the transmission (at least in most cases).
In a car, there will be significantly more "traction" which will allow
the transmission to be subjected to more torque load on intial
accelleration - which is where it will break if it is going to break.

Norton Commando and Manx engines were used extensively in automobile
racing in the sixties in the "Formula Cooper" cars.

As for the truck trans in a 1200 lb car - I don't suspect it would
remain a 1200 lb car - and that would be the only factor causing the
engine to wear out faster.
Final Drive ratio is something else to consider - to keep engine RPS
and loads both in check.