Pilot Balloon Slide Rule
From the Collection of Wangaratta RSL Sub Branch 2-4 Templeton Street Wangaratta Victoria
- The case is fabric covered wood with felt fabric lining containing a long black laminate ruler with numerous white markings and numbers. Top of the ruler is in three sections with the centre section movable by small gold metal knobs at either end.
- 63cm.L x 5.5 cm w x 1.5cm D
- pilot balloon slide rule
- The Mark II Pilot Balloon Slide Rule was made of wood laminated with heavy white plastic with a length of 24.5-in. and width of 2.5 inches. Mark II rules were manufactured in Australia by W & G (Melbourne). The W & G rule differs only slightly from the English A. G. Thornton LTD rule. The W & G rule uses serif fonts and has some fiducial marks that the English rule lacks. Exact dates of production are not known but the MK II is known to have started production by 1927. The printed scales are engraved in the plastic faces. The slide rule has 4 captive cursors (glass windows and brass guides) that ride in slots on the top and bottom edges. Each can be moved independently of one another. The cursors are missing from this item. Brass knobs at both ends of the slide facilitate its movement. The case is fabric covered wood with felt lining.
The Pilot Balloon slide rule is used to convert the observed azimuth and elevation readings into wind velocity and direction records.
No known history as the item was found in house after purchase.
- W&G White and Gillespie (Maker)
- This slide rule contains a engraved notation on the rear face "IMPORTANT. NORMALLY NUMBER OF GRATICULE SCALE DIVISIONS PER RADIAN (K) X LENGTH OF TAIL IN FEET (I) = 12X 105. IN OTHER CASES MULTIPLY GRATICULE READINGS BY 1.2/KI BEFORE CALCULATION ON RULE"
Top of Slide Rule - RAAF Ident No G268/480 Serial WG/22
- 16 Feb 2019 at 6:39PM