On Sat, 03 Mar 2012 22:28:29 -0600, Ignoramus20398
wrote:

On 2012-03-04, Pete C. wrote:

Ignoramus20398 wrote:

On 2012-03-03, Karl Townsend wrote:
On Fri, 02 Mar 2012 21:28:21 -0600, Ignoramus22470
wrote:

On 2012-03-02, Karl Townsend wrote:
On Thu, 01 Mar 2012 23:03:30 -0600, Ignoramus6107
wrote:

I have been practicing and driving my semi tractor almost every day
recently. Not much time every day, but I usually manage to find at
least some time every day. At my age and after 17 years of driving
auto transmission, the skills to drive a truck with an unsynchronized
manual transmission do not come easily, but I am making progress. I
can now shift up and down, and by now, it works well most of the time.

I will soon try to pass a theoretical exam to get a CDL learner's
permit.

i

You're learning at a better age than myself. I started driving
truckloads of wheat to the elevator at 14. Dad told me to never go on
the highway. Of course, I ignored that. I forgot to down shift at the
top of pleasant grove hill. When the brakes wore out, I tried to down
shift and missed it. That old truck was doing 80 at the bottom of the
hill. I was lucky to see 15. But, I've never forgot to down shift
again.


I have found a golden guy, an honest mobile mechanic, I will have him
check my brakes out.

i

Iggy, just in case you don't alread know, NEVER go down a hill in a
gear higher than you go up it. Downshift at the top. No matter how
good the brakes are, it won't stop 80,000 lbs. I just told you how i
learned this.

Karl


Karl, I am aware of this, yes. I think that proper brakes are enough
to slow down downhill and to switch to low gear, but I am aware of the
brake fade phenomenon.

The problem is not the brake fade, the problem is if you do not do your
downshift before you go over the crest of the hill, you have very poor
odds of being able to successfully complete the downshift on the
downgrade. What happens is you get it out of gear and then you are
unable to get it into the lower gear and often you can't get it back
into the previous gear as well. This leaves you on a downgrade in
neutral with *no* engine braking at all and your service brakes won't do
the job. It's runaway truck ramp time if you are lucky enough to find
one.

OK, I will bite, why would the service brakes not do the job and stop
the truck, at least once?

With an unloaded truck, they probably would.
With a semi-loaded truck, they might.
With a fully-loaded truck, they would burn up in the process.
Think power-to-weight ratio. The weight requires so much force to be
put on the shoes/drums that they can't release the heat in time to
work effectively.

First you experience brake fade, where it takes more and more force on
the pedal to slow you down. Then you feel as if you've lost the brakes
altogether. About this time, you usually see smoke coming from your
axles and you occasionally lose a tire to bursting from the heat
generated by the brakes, transmitted through the wheels. (Retreads are
the quickest to do this, and I've seen/heard dozens pop on I-5 where
I'm living now, on a mild downgrade!) Then you see actual flames
coming from the axles, where the brake shoes have caught fire inside
the drums. I've seen all of this on the road, which I'm sure many
will now attest to. My buddy Phil has been driving portable TV
stations around to the sports events and has told me some real WOW!
stories. He survived losing his brakes; his truck (tractor) didn't.

--
It is characteristic of all deep human problems that they are
not to be approached without some humor and some bewilderment.
-- Freeman Dyson