Warren-Knight Theodolites

© Brooke Clarke 2016

20-8403 Pibal

Warren-Knight
                    20-8403 Pibal Theodolite


20-8353 Telemetering

Warren-Knight
                  20-8353 Pibal Theodolite w/shaft encoders





Background
Theory
Description
Operation
Photos
Patents
Related
References
Links

Background 

This instrument was made by Warren-Knight and they are still in business (web page).  Most of the pibal theodolites have electronic readouts, but they still make this 8403 model as well as another all mechanical model 8500.
This theodolite is designed to track a ceiling (pilot) balloon, it's also called a PiBal (Pilot Balloon) theodolite or a Radiosonde.  Since the balloon is usually at a high viewing angle the optical design has a right angle bend so that the observer always looks horizontally into the eyepiece and the elevation of the balloon does not effect the observer.  This is very different from a normal theodolite that you can not use at high elevation angles without a 90 degree eyepiece adapter.

This is a commercial version of the military ML-47 (?) pibal theodolite.

My interest is for looking at stars, and Polaris (Wiki) in particular but also for it's use in relation to weather.

Theory

There are a number of different things that can be determined using a balloon.  The balloons are very standardized in terms of construction and inflation so that their rate of rise will be known.  Balloons are also used to raise antennas like for the Gibson Girl lifeboat survival transmitter.

Cloud Height

This is done using a ceiling balloon (Wiki) and a stop watch.  Not sure if just by eye or if binoculars or a telescope is used in addition.  Ceiling height is not when the balloon disapears, but rather when it starts to fade.
Ceiling height in feet = 460 * (minutes since launch)

Winds Aloft

The balloon is tracked and data recorded for time since launch, azimuth relative to true North and elevation angle.   For daytime observations it's just the balloon that goes up, nothing is attached to it.  In times past a water activated reserve battery was used to light a flashlight bulb so the balloon could be tracked at night.

Weather

To determine weather parameters aloft a Radiosonde (Wiki) can be lifted by the balloon.  It transmits back the pressure, temperature and humidity.  The units used in the 1950s used the pressure change to switch between temperature and humidity so that only a single parameter was transmitted and by paying attention to the time and number of cycles the pressure could be determined and the pressure is related to the altitude.  Not sure if these were tracked with a pibal theodolite.  But later they were tracked by the SCR-568 radar (these used to be advertized in military surplus flyers). 

Disk Microphones

These are microphones supported by springs which in turn are attached to a ring.  That way a mechanical shock to the stand would not make as much of a noise.  A short hand name for these microphones was "disk".  So when the AF put out a press release sayhing that "flying disks" were what crashed in Roswell New Mexico in 1947 a newspaper reported who was not farmiliar with that termonology reported that a flying "sauccer" had crashed.  See: Roswell Connection

Description

Mounts on a standard 3-1/2"-8 surveying tripod

There are three ways to aim at a target:
  • Use gun type open sights (this part is in the transit case)
  • Look through the low power inverting finder scope
  • look throught the high power inverting main telescope
There is a level under the eyepiece that switches the optical path between the finder scope and the main telescope.

There is a through compass, i.e. a compass without a scale that's only used to indicate North or South.  You can see it in Fig 1 on the right just under the main telescope tube.

The 20-8403 is a first generation analog type where the readout is a veneer.  Battery holder is a separate item resembling a flashlight.

The 20-8353 (W-K web page) has shaft encoders added for azimuth and elevation.  Battery holder is on instrument frame and uses side-by-side "D" cells.  It's intended to be located near a radio aid to navigation (ILS, MLS, VOR, TACAN, VORTAC) and the encoders are used to modulate a UHF radio transmitter.  A matching telemetry receiver is in the test aircraft so that they can easily compare the instrument reading with their actual position from the theodolite.

Operation


Setup and leveling is the same as for any surveying tripod mounted tranist or theodolite.  And like a surveying instrument the elevation angle is relative to a bubble level.  But unlike a surveying setup the azimuth scale needs to be referenced to true north.  TM 11-6675-200-10 for the military ML-47 lists a number of ways of finding North in order to calibrate the azimuth scale.  The ways of orienting the azimuth scale to North are: Compass, Sun, Polaris, Equal star/Sun Angles, Datum Lines or Transference.

Photos

8403

Fig 1 Pibal theodolite mounted on 3-1/2-8 surveying tripod
Warren-Knight 20-8403 Pibal Theodolite
Fig 2 Transit case with factory label.
Warren-Knight 20-8403 Pibal Theodolite
Fig 3 bottom & Az cal assy
Installing Az cal assy requires special 2-pin spanner.
Warren-Knight 20-8403 Pibal Theodolite



8353

Fig 20 In packing case
The red ring at the lower right is a thread protector cap for the
included tripod.
Warren-Knight 20-8353 Pibal Theodolite
                      w/shaft encoders
Fig 21 Far side
2 vertical cylinders are battery box
There  is a 1/4" phone jack for each encoder.
Warren-Knight 20-8353 Pibal Theodolite
                      w/shaft encoders
Fig 22 Observer's side 
Light colored cylinders are shaft encoders.
Warren-Knight 20-8353 Pibal Theodolite
                      w/shaft encoders
Fig 23 on factory tripod, legs at minimum length.
Warren-Knight 20-8353 Pibal Theodolite
                      w/shaft encoders




Patents

Class
33: Geometrical Instruments
73: MEASURING AND TESTING
235: REGISTERS
340: COMMUNICATIONS: ELECTRICAL
342: COMMUNICATIONS: DIRECTIVE RADIO WAVE SYSTEMS AND DEVICES (E.G., RADAR, RADIO NAVIGATION)
356: OPTICS: MEASURING AND TESTING
702: DATA PROCESSING: MEASURING, CALIBRATING, OR TESTING   
708: ELECTRICAL COMPUTERS: ARITHMETIC PROCESSING AND CALCULATING
  
  940329 Optical instrument for determining the direction of travel of air-ships and the like, Otto Krell, Nov 16, 1909, 356/150; 33/318; 74/5.3 - gyroscopic stabalized right angle telescope for looking at the ground from the balloon.
1296477 Instrument for Recording the paths of Aeroplanes, G.J.N. Carpentier, Mar 4, 1919, 33/228 434/15-
1446574 Nephoscope (Wiki), Alexander McAdie, Feb 27, 1923, 33/284, 356/27, 33/1.00R - measuring the altitude, direction, and velocity of clouds
1913512
Meteorological indicator, Anita Reynolds, Jun 13, 1933, 73/170.11, 73/170.15, 73/170.8, 73/178.00R, 333/24.00C, 340/949, 340/870.1, 73/170.16, 341/173, 73/170.28 - radiosonde
2027367 System of determining meteorological conditions by radio, William R Blair, Jan 14, 1936, 342/450, 340/870.28, 73/170.28, 340/870.1, 455/61, 342/460 -balloon &  radiosonde
2162582 Device and Method for Determining Upper Air Wind Direction and Velocity, H.B. Kaster, June 13, 1939 33/228, 33/274 - instrument for observing a free balloon and method of determining wind speed & direction
2216161 Apparatus for making meteorological observations, Allen V Astin, Leon F Curtiss, Oct 1, 1940, 340/870.28, 73/170.28, 346/33.0TP, 235/61.00B, 346/50, 346/33.00B - balloon & radiosonde
2347160 Radiometeorograph transmitting apparatus, Charles F Wallace (Wallace & Tiernan), Apr 18, 1944, 340/870.1, 340/870.28, 73/170.28, 340/870.13, 200/56.00R, 340/870.12, 200/19.21 - barometer switches temp and humidity
2381009
Chronometric radiosconde system, Joseph A Siderman, Aug 7, 1945, 340/870.1, 307/651, 455/91, 340/870.12, 340/870.16, 340/870.13, 307/650, 455/98 - radiosonde: uses clockwork to switch sensors & reference resistor for calibration
2519180
Wind data computer, William K Ergen, Aug 15, 1950, 702/3, 235/413, 708/809, 235/400 - convert free balloon observations more useful data
2651459
Velocity and direction computer, James M Brady, Athelstan F Sipilhaus, Sep 8, 1953, 235/413, 33/1.00R, 701/519 - convert free balloon observations more useful data

Related

Astronomy
Surveying
Theodolites
Lietz 115 transit

References

Military Manuals
TM 11 6660-258-25P ML-474 (Pilot Balloon type) PIBAL
TM 11-6675-200-10 ML-247 (Pilot Balloon type) PIBAL
TM 5-6675-200-14
TM 5-6675-200-25P
TM 11-6675-200-25P ML-247 (Pilot Balloon type) PIBAL
TM-11-6675-200-35 (Pilot Balloon type) (Wiki) PilotBalloon.com
Theodolites ML-47 - C through  ML-47-R,
ML-247 and  ML-247-A  and
Double Center Theodolite ML-474/GM

Links

Martin Brenner's, Pilot Balloon Resources -

Liberated Manuals - theodolite -
PRC68, Alphanumeric Index of Web pages, Contact, Products for Sale


Back to Brooke's: PRC68, alphanumeric index of web pages, Products for Sale

Page Created 11 May 2016