In article , "KERRY MONTGOMERY" wrote:

"Doug Miller" wrote in message
t...
In article .com,
"onoahimahi" wrote:
On Feb 9, 2:39 pm, (Doug Miller) wrote:
In article . com, "Geo"
wrote:

Just a couple other things that might make a difference. I've heard
that having 3 wheelers makes a difference. Check your rules on that
one. That is, one of your wheels simply doesn't touch the track. The
friction of three wheels is less than four.

Incorrect -- the total friction is unchanged, because the weight
supported
remains the same. With only three wheels touching the track, the wieght
on
each wheel, and consequently the friction force on each wheel, goes up
by
33%.


A three wheel car is faster because it takes less energy to spin three
wheels than four.

Again, incorrect. The total energy is the same, because the total friction
is
the same.

If anything, a car riding on only three wheels is likely to be somewhat
slower: since the friction force will be imbalanced left-to-right, the car
will travel a slightly curved path, with the two wheels on the concave
side.

Also, on the wheels
themselves some people make the part of the wheel where the nail goes
through convex. Again, less friction.

Again, incorrect. Changing the size or shape of the contact area does
not
change the amount of friction.

Moving the friction point closer to the axle reduces the torque on the
wheel.

And that makes a difference how?

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

Regarding 3 wheels VS 4; 3 wheels will require less energy to accelerate
than 4, won't they?

Go back a few posts and see where the 3 vs. 4 discussion started. The case
being discussed is 4 wheels with only 3 in contact with the ground, vs. 4
wheels with all 4 in contact.

The friction forces are _exactly_the_same_.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.