Home brewed cheap Dyno

[DARROW COLE]

I looked into this a few years ago but abandoned the idea after 
some thought. Here is what I reasoned (please note that I did not 
actually build or test anything so I may be off base):

Whatever device is used as the Load Absorbing Device is 
essentially converting energy. A water pump is putting kinetic 
energy into the water. Restricting the flow rate will result in 
less kinetic energy going into the water although more energy may 
go into heat. It will take a big pump and a lot of water to brake 
a large engine.

A water brake, on the other hand, is putting most of the energy 
into heat. If you look at a schematic for a water-brake dyno 
system, you will see, in addition to the brake, a water pump and 
cooling tower. These are required to move the energy into the air 
as all the brake does is generate heat. Control is achieved by 
adjusting the amount of water in the brake. I took the view that 
the brake is "shearing" the molecules apart to generate the heat.

Water brakes run in the $2,000 to $10,000 range depending on 
manufacurer and capacity so I reasoned that if I ever got to the 
point of building a dyno, I would simply buy a brake. Check the 
Thomas Cat for sources or send me a note and I will dig out my 
notes.

Darrow Cole



On Sat, 17 May 1997 10:15:55 +0900 Ross Forgione <ross at apdata.com.au> 
wrote:
> 
> This is not really a chasis dyno, but I have spoken to a few people who
> have found a couple of sites on the Net talking about using "BIG" water
> pumps with a gate valve  to create a "Back Pressure" type function. The
> Idea is you get the pump, bolt a couple of strain gauages on its base,
> connect it to the crank of the engine (create the necessary protection
> barriers), close the gate valve to about 98% for  load and away you go. 
> 
> Once the engine runs, open throttle to max then SLOWLY open gate valve to
> bring RPM up and take readings (Strain gauage output v RPM) at appropriate
> points.
> 
> My questions.
> 
> 1. Will this WORK ?
> 2. Is this how non electrical load dynos work ? 
>