Jeff,
The idea is not to run an engine at load for any length of time.  Short
burst under load should give you info you are wanting using the instruments
plan for the aircraft.  This is an cheap way to get fuel flows, horsepower,
egt, and more.  I would think 1-2 minute burst with cooling time in between
each test should keep things cool enough.

I don't think running water through the air vents in the rotors is a good
idea during a dyno run.  It would cause excessive drag giving a lower than
actual reading.  It could be used between runs to reduce the time between
each run.

It could be configured as a removable appliance to the engine test stand.
Once built, you could test changes to the engine for there effect without
having big bucks tied up in a real dyno.  I would think it can be built for
around $150.00 and a day in the garage.

Here in Denver, an engine dyno rents for $500.00 a day with a one day
minimum, that include setup and teardown.  You better be ready to do a lot
of work.

Glenn Sneed

What is the matter with a prop load Glen. You will need a redrive sooner
or later.

Paul Lamar

Just do the math.  It will save you much grief and agony of building this
useless device.  Q=m*c*delta T

Q=the heat of the horsepower absorbed
m=the mass of the brake rotor and pads
c=the specific heat of the brake rotor and pads
delta T=the temperature rise

My guess is that a "truck rotor" will be good for no more than 10 seconds
at 150 hp.  Certainly not enough time to obtain a stable dyno reading.
What's that smell?

O.K. Fine.   Here goes.
c=.10 btu/lb*deg F for cast iron
Q=150 hp = 6366 BTU/min
Use 1000 deg temperature rise
Use 15 lb for mass of rotor and pads

Damn, I was wrong.  That gives 14 seconds.  And I thought it would be less
than 10 seconds.  As for using water to get the heat out: It would take a
proper heat transfer solution to work i.e. proper flow and surface area.
There is not enough surface area on a disk to hose it down at high HP and
have it not overheat.

Jeff Spitzer

Your temp rise is too low Jeff. Those disk run 1600 F or more in road racing.
Bright orange at night. You have lots of radiation from the surface of the 
disk. It takes about the same HP to stop a road racing car as it does to 
accelerate it roughly. 800 HP from the engine 200 HP from each brake 
disk. Very roughly. Usually about a four inch diameter duct for each brake
pumping air into the hollow disk at an average 100 MPH speed will keep the 
disk brakes working on a 800 HP road racing car for 12 hours or so. Roughly.

Paul Lamar
 
The Aircraft Rotary Engine Newsletter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org