Re: Truck stopping distances?

["Andrew J. Graham" <grahamaj@APPSTATE.EDU>]

Old truck driver here,

The larger truck/trailer (18 wheelers) have separate brakes for the
trailer.  Stopping quickly in a straight line requires pulling the
trailer brakes first, and with more pressure than the front brakes
(obviously). When running winding roads truckers frequently use only the
trailer brakes, to avoid having the trailer push the truck in a curve
(or jack-knifing).  The most dangerous combination of truck and trailer
is the empty dump truck pulling a trailer hauling heavy equipment, and
no trailer brakes.  I was fired from my last truck driving job for
refusing to continue driving said combination. One close call too many.

andy graham

Michael Edmiston wrote:
> Here's the fourth shot... talk to a truck driver... find about about
> jack-knifing.
>
> Assuming we are talking about an articulated truck... i.e. a semi-truck...
> i.e. a cab pulling a trailer...
>
> the driver and brake system must avoid locking up the rear wheels and/or
> getting more braking up front than behind.  Otherwise the trailer
> jack-knifes.
>
> Perhaps someday cab units and trailers will both have antilock brakes.  But
> until that day, the truck driver simply cannot jam on the brakes like a car
> driver might do.  Of course the car driver would be better off if he didn't
> jam on the brakes.  But the truck driver is way worse off than the car
> driver if the truck driver jams on the brakes and does a jack-knife.  Not
> only does he lose control, the chances of a rollover of the trailer and cab
> are greatly increased, and the trailer or load could roll onto the cab area
> or onto cars.
>
> I think this is a physics example of the "tail wagging the dog."
>
> Michael D. Edmiston, Ph.D.              Phone/voice-mail:       419-358-3270
> Professor of Chemistry & Physics        FAX:                    419-358-3323
> Chairman, Science Department            E-Mail                  edmiston@bluffton.edu
> Bluffton College
> 280 West College Avenue
> Bluffton, OH 45817