Truck parts Dynamometer.--telma

[Kalle Pihlajasaari]

Hi,

> >>Other stupid ideas......
> >>Build a back yard dyno out of a truck axle..... 
> >
> >Not so stupid... Know what a Telma is?
> >It's an electromagnetic brake system used on trucks & buses.
> >They are normally mounted inline with the propeller shaft.
> >If you've noticed the bus driver activate braking through a
> >multiposition stalk near the steering wheel, that's the control stick.
> >
> >They should be fairly easy to find at appropriate breakers yards.
> >The nice thing about them is that the braking effect is current
> >controlled. So they should need only (very) high current drivers
> >to be directly controlled from a micro. They are also small and
> >light in proportion to their braking effect.
> >
> Is anybody in the U.S. on this list familiar with a "Telma"?  This sounds
> like just the ticket!

I think they might be called a Thelma but the same thing at any
rate.  There are 2 other similar devices collectively called retarders
that are retrofitted or option on trucks and busses. One of them is
a Hydraulic system (similar to a locked output fluid coupling
with variable fluid level) made by Voith (a german company) the third
one I'm not sure of.  Some Voith transmissions have the retarder
built in.

All of these units convert to heat and are typically plumbed into the 
vehicle cooling system with 2" pipes.  They would certainly be
a suitable load for a cottage dyno as they are pretty well self contained
but you would have to work with the controls a bit.  Normally very
secretive about the load dump algorithms to prevent overheating and
such.  The Thelma units have a dubious reputation in South Africa
due to the poor heat removal with big hills and warm weather, some
of them I think had air only cooling.  They aer not rated for continuous
load but you might get bretty close unless you are trying to test a
truck engine.

Cheers
-- 
Kalle Pihlajasaari     kalle at data.co.za
Interface Products     Box 15775, Doornfontein, 2028, South Africa
+27 (11) 402-7750      Fax: +27 (11) 402-7751