Young Gill Propeller Anemometer Models 27106DT - Manual (Page 3)

Page 2
When the propeller is used for measuring vertical wind component,
users may want to apply a 1.25 multiplier to the output signal. This
may be done numerically in data processing operations or
electronically in the signal conditioning. Using the multiplier brings
the anemometer output signal within ±3% of the cosine response
for elevation angles between -30 and +30 degrees. Since the
standard deviation of wind elevation angle in open terrain rarely
exceeds 12 degrees, 98% (2.5 standard deviations) of
observations will be within ±30 degrees. Using the multiplier is NOT
necessary when the anemometer is used in a UVW configuration
with YOUNG Model 26700 Programmable Translator.
CALIBRATION FORMULAS
Model 27106DT Propeller anemometer photo chopper
w / 08254 Propeller
WIND SPEED vs PROPELLER RPM
m/s = 0.00500 x rpm
knots = 0.00971 x rpm
mph = 0.01118 x rpm
km/h = 0.01800 x rpm
WIND SPEED vs OUTPUT FREQUENCY
m/s = 0.03000 x Hz
knots = 0.05826 x Hz
mph = 0.06708 x Hz
km/h = 0.10800 x Hz
MAINTENANCE
Given proper care the Gill Propeller Anemometer should provide
years of service. Components are conservatively rated and
require little maintenance. The only parts likely to need replacement
due to normal wear are the precision ball bearings. The
replacement procedures are best performed in a service facility
and only by qualified technicians. If service facilities are not
available return the instrument to the factory.
Refer to the accompanying drawings to become familiar with part
names and locations.
FLANGE BEARING REPLACEMENT
If anemometer bearings become noisy or wind speed threshold
increases above an acceptable level, bearings may need
replacement. Check bearing condition using a Model 18310
Anemometer Bearing Torque Disk. If, after replacing bearings, the
torque is still too high, check the photo chopper transducer for any
misalignment.
Replace bearings as follows:
1. REMOVE OLD BEARINGS
a) Remove propeller from anemometer.
b) Unthread 27153A generator housing threaded collar.
c) Unthread generator housing from shaft housing.
d) Remove 3-48 screw securing photochopper circuit board
to photochopper mounting.
e) Remove 4-40 screw securing window disk to photo disk
hub.
f ) Loosen set screw on photo disk hub and remove from
propeller shaft.
g) Pull front bearing dust shield off housing.
h) Using the edge of a pocket knife, gently pry front and rear
bearings out of housing.
2. INSTALL NEW BEARINGS
a) Gently insert front bearing into housing.
b) Push front bearing dust shield back onto housing.
c) Carefully slide propeller shaft through front bearing and
into housing.
d) Slide rear bearing over propeller shaft and gently push it
into housing.
e) Place photo disk hub on propeller shaft.
f ) Allow 0.010 inch (0.25 mm) end play gap between shaft
collar/coupling disk and bearing. Tighten set screw (80 oz
in, 5600 gm-cm max torque).
9) Re-assemble in reverse order as stated in step 1.
h) Check bearing torque to confirm it is within specifications.
A DDITIONAL REFERENCES
References containing additional information about the Gill Propeller
Anemometer are listed below in chronological order:
Holmes, R. M., Gill, G. C., and Carson, H. W., “A Propeller Type
Vertical Anemometer”, Journal of Applied Meteorology, Vol 3,
1964, pp. 802-804.
Drinkow, R., “A Solution to the Paired Gill-Anemometer Response
Function”, Journal of Applied Meteorology, Vol 11, 1972,
pp. 7-80.
Hicks, B. B., “Propeller Anemometers as Sensors of Atmospheric
Turbulence”, Boundary-Layer Meteorology, Vol 3,1972,
pp. 214-228.
Fichtl, G. H., and Kumar, P., “The Response of Propeller
Anemometer to Turbulent Flow with the Mean Wind Vector
Perpendicular to the Axis of Rotation”, Boundary-Layer
Meteorology, Vol 6,1974, pp. 363-379.
McMichael, J. M., and Klebanoff, P. S., “The Dynamic Response of
Helicoid Anemometers”, NBSIR 75-772, National Bureau of
Standards, 1975.