Horsepower

So now I'm thinking...
How do I measure the Horsepower of my Sonerai's 1835cc VW motor?
Or do I just make a couple of assumptions?
Prop 52" dia. 42" pitch motor can turn it 3000rpm static at WOT and a ground
elevation of 5000 feet and temperature of 31 degrees Celsius or 87.8 degrees
F.
Assuming that the prop is more or less efficient (guess 80%???) where does
that leave me?

1: Make a stand to mount the motor on similar to some of the rotating engine
rebuilding stands, only use a small truck wheel that uses 2 timken bearings,
and a hollow axle---mount the axle rigid to the stand.
2: Attach a big plate or framework to the wheel, using the lug bolts as attach
points.
( I made my framework motor mount points the same as the mount points on
my fuselage, to allow testing different engines)
3: The motor mount MUST hold the engine with it's PROPELLER center line-
centered on the wheel hub.
4: extend an arm---horizontally-if you want to use a bathroom scale--with a
single ball(from a large ball bearing) welded to the bottom of the arm at a
precise
distance from the center of the wheel hub.You will want a smooth plate of metal
on the scale platform to make the contact point constant & little friction.--I
used
a little pneumatic cylinder with an accurate pressure gage, & air pressure
regulator
to hold the tork arm in the center of the travel of the cylinder.
If you have a conventional Rt. Hand prop, --the arm should project out to the
left,
as you stand behind the engine--
which is where I mounted a panel with all the usual engine instruments.

Run the engine, measure the pressure on the scale(subtracting any tare wt.)
Multiply by the length of the torque arm-(in feet).--This is your torque in Ft.
Lbs.

Measure the PROPELLER RPM--which equals engine rpm divided by
the ratio of the PSRU ( if you have one)
Then your HP =
Torque X RPM X 2pi 2pi= 3.14159 X 2 =
6.28
------------------------
33,000 1 HP = 33,000 ft lbs
per minute
( the 2pi X arm length gives the distance the arm would move, if the propeller
were held still--)
NOTE: record the temp, & actual barometric pressure----when your figures seem
a little puny, you can correct them to sea level, std baro, & temp (68 OR 70
DEG.F) I fergit which.

Note: this makes a nice club project where everyone can test their engines.
If you get real interested, I can send a pic of mine .

Andre wrote:




So now I'm thinking...
How do I measure the Horsepower of my Sonerai's 1835cc VW motor?
Or do I just make a couple of assumptions?
Prop 52" dia. 42" pitch motor can turn it 3000rpm static at WOT and a ground
elevation of 5000 feet and temperature of 31 degrees Celsius or 87.8 degrees
F.
Assuming that the prop is more or less efficient (guess 80%???) where does
that leave me?

Thanx Jerry,
This sounds not too complicated. I get the general idea , but maybe you can
send me a pic to the address which is made up of my name below with a dot
and then viljoen and then the approriate AT sign ended off with ast dot co
dot za. (I hope my elaborate explanation makes sense and still fools those
spam engine email address collecters. :-)
Looking forward to your reply.
Regards
Andre

"Jerry Wass" wrote in message
...
1: Make a stand to mount the motor on similar to some of the rotating
engine
rebuilding stands, only use a small truck wheel that uses 2 timken
bearings,
and a hollow axle---mount the axle rigid to the stand.
2: Attach a big plate or framework to the wheel, using the lug bolts as
attach
points.
( I made my framework motor mount points the same as the mount points on
my fuselage, to allow testing different engines)
3: The motor mount MUST hold the engine with it's PROPELLER center line-
centered on the wheel hub.
4: extend an arm---horizontally-if you want to use a bathroom scale--with
a
single ball(from a large ball bearing) welded to the bottom of the arm at
a
precise
distance from the center of the wheel hub.You will want a smooth plate of
metal
on the scale platform to make the contact point constant & little
friction.--I
used
a little pneumatic cylinder with an accurate pressure gage, & air pressure
regulator
to hold the tork arm in the center of the travel of the cylinder.
If you have a conventional Rt. Hand prop, --the arm should project out to
the
left,
as you stand behind the engine--
which is where I mounted a panel with all the usual engine instruments.

Run the engine, measure the pressure on the scale(subtracting any tare
wt.)
Multiply by the length of the torque arm-(in feet).--This is your torque
in Ft.
Lbs.

Measure the PROPELLER RPM--which equals engine rpm divided by
the ratio of the PSRU ( if you have one)
Then your HP =
Torque X RPM X 2pi 2pi= 3.14159
X 2 =
6.28
------------------------
33,000 1 HP = 33,000
ft lbs
per minute
( the 2pi X arm length gives the distance the arm would move, if the
propeller
were held still--)
NOTE: record the temp, & actual barometric pressure----when your figures
seem
a little puny, you can correct them to sea level, std baro, & temp (68 OR
70
DEG.F) I fergit which.

Note: this makes a nice club project where everyone can test their
engines.
If you get real interested, I can send a pic of mine .

Andre wrote:




So now I'm thinking...
How do I measure the Horsepower of my Sonerai's 1835cc VW motor?
Or do I just make a couple of assumptions?
Prop 52" dia. 42" pitch motor can turn it 3000rpm static at WOT and a
ground
elevation of 5000 feet and temperature of 31 degrees Celsius or 87.8
degrees
F.
Assuming that the prop is more or less efficient (guess 80%???) where
does
that leave me?

Belive or not, the way it works on dyno's of engine manufactures is
that a test standard engine is used to calibrate the dyno to it's
output. Typically these engines are re checked for repeatable
dependable performace data frequently under government measurements
quality assurance audits.
Check with MOFOCO in Milwalkee, they sell their VW engines
with dyno time on the rebuilds. Don't mention the word airplane...;-)
Ask for a horsepower and torque plot.
I'd say 53-55 horsepower depending on what parts options are used.