The simplest and cheapest solution might be a big trailer disk
brake. About $160.
http://www.trailerpartsdepot.com/itemdesc.asp?CartId={316C1101-2A63-4A70-814
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A4721EVERESTC6CE132}&ic=81104&eq=81104A&Tp=
Make an adapter plate/flange to match the prop flange. This is the
hardest part, but not all that difficult. The bolt circle for an SAE 2
prop is 4.75" and the bolt circle for the trailer wheel is 5.5". You
could probably drill new holes through the brake rotor and trailer hub
and just use a simple spacer.
Bolt a nice long extension on the caliper arm and get your torque
information from the force needed to keep that extension arm in place.
(Use a scale, or a load cell if you want to get fancy.) Make the
extension arm long so that you don't put too much side force on the
front bearing or the engine mounts. Adjust the torque with weights on
the brake actuator arm or a porta-power pump with a gauge. The torque
will be roughly proportional to the hydraulic pressure.
Direct the garden hose into the middle of the disk so the water goes
through the vented disk. Make a sheet metal "fender" to contain the
spray. Water is cheap and you are not going to run this thing for weeks
at a time.
Bill Dube'
I like this idea Bill. When converting water to steam it absorbs
a lot of calories. In fact I mentioned spraying water on a disk brake
in a book I wrote years ago on race car braking systems.
The big advantage Doug, is you can measure HP at many different RPMs
while with a wood prop club only at one RPM.
Paul Lamar ...No rotor no motor
Thanks Bill,
This sounds like the best way to go. I've heard of brake loading dynos but
I was concerned they would soon overheat. Cool it with water. Cool!!!
Timely suggestion as well. I was just trying to figure out how to support
all those staggered boards in the hydraulic press to get a good bond. I was
going to buy them all tomorrow.
Actually I can get truck disc brake discs easily. Misubishi Corp. has been
having a lot of trouble with their bus and large truck wheels falling off in
the last year. Sales are way down. Seemed they have been covering up the
casting problem for years. I should be able to get all the parts for free:)
Yea and measure torque as well which I believe would be harder to
extrapolate from water pressure as the temperature is fluctuating rapidly.
Which side of the engine should I put the brake arm lever? Opposite side of
revolution?
Doug Fir.
Depends on how you locate the load sensor. Do you want the load
sensor beam to go up or down? You can use everything you have.
Just anchor the brake caliber to the base frame so it cannot rotate.
BTW make sure they are hydraulic and not air. Hydraulic is easier.
Lots of truck brakes are air actuated. If air you will need some type
of air compressor and a way of controlling it. Shop air may be OK.
Also get the brake pedal assemble including master cylinder and or air
control valve out of the truck cab.
The water cooling system is total loss so the temp matters not.
Here are a few 3Ds
Paul Lamar ...No rotor no motor.
Paul
After sleeping on this idea a night I realized that I didn't explain it well
enough. Bill was probably suggesting a long lever applying manual disc
braking force perpendicular to the plane of engine rotation.
I want to anchor the whole assembly down and do my testing from the
adjoining room. That means remote controls. I have a box of servos and
linear motors, air and oils valves etc. laying around so the throttle
control and turbocompound ratio adjustment is relatively easy.
I was speaking about a lever attached to the caliber assembly that was
free to rotate an inch of arc. On the end of this lever I could place a
load cell (which I haven't found a good source for yet) or a hydraulic
piston and gauge for a rough test. I want to buy a load cell for future more
advanced testing and use in flight but I am not clear where or how at this
moment.
The real trouble for me is just to do a quick and simple test:) The
planning and the process are enjoyable. Been in Japan too long I guess. I
still have to get the stock engine running and figure out what hoses to keep
and what to plug. I am going to make the wiring harness between the EC-2
and the programming faceplate at least 24 feet long to emulate the SeaWind
installation harness length. Hopefully the length will be OK. I am a
little concern about voltage loss, resistance increase over that distance.
The EC-2 computer will be behind the fire wall.
Activating the disc brake could be done by air (which my shop has) or oil as
in the using the aforementioned hydraulic pump or linear mechanical motor.
Air would be easiest. First I'll see what type of brake I can find.
I also don't need to change my present motor mounting system either which is
good news.
Doug Fir
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Doug this is very very very dangerous. Cast iron disk brakes run cherry red.
That means the cast iron they are made from loses most of its strength.
A 3 foot diameter truck wheel and tire running at 80 MPH or 120 feet per second
has a circumference of 9.4 feet. That means the wheel is revolving at
only 12.8 revolutions per second or 766 RPM.
Not much. A far, far, FAR cry from 7000 RPM.
The force on the brake disk particles are Mass x Velocity squared / radius
766 squared = 586,456 while 7000 squared = 49,000,000 or 83 times
as much force on the cherry red cast iron brake disk particles.
When this thing come apart (and it will surely come apart)
it will go through anything short of M1 tank armor plate.
I was temporarily insane when I thought it was a good idea and
am sure Bill was too.
Forget it. Go with the wood fan.
Paul Lamar
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