Re: dynamometercar

[James Robinson <Wascana@my-deja.com>]

Tom wrote:
> 
> Does any one here know what a Dynamometer car does?
> and what its main function is.

A dynamometer car is basically a rolling laboratory.  They can carry
equipment to perform any number of tests on braking systems, train
handling, fuel consumption, schedule compliance, traction systems, radio
propagation, etc.

They were originally introduced to help evaluate the performance of
steam locomotives.  They were built with an apparatus to measure the
pulling force of the locomotive in the form of a big spring mounted
behind the drawgear, and a mechanical linkage to a strip recorder inside
the car that would plot the pulling force on a continuously moving
chart.  They also typically had a mechanical device that integrated the
pulling force over distance to calculate the amount of work done by the
locomotive.  Mechanical engineers could use the car to evaluate new
locomotive designs and to make improvements.

More recently, the old mechanical measurement equipment would be
replaced with electrical strain gauges and computer sampling equipment,
but the intent is still the same: to evaluate locomotive performance. 
As noted at the beginning, the cars are also used to perform any type of
test that would require a mobile laboratory.  The cars do not normally
measure any track characteristics, those are track geometry cars.  I
suppose there is nothing that would stop the combining of the two
functions, but it is not normally done.