Slide rules HOME page COLLECTION 10" RULES U.S.A.
Make Pickett, USA
Model 905-ES, Texas Speed Rule

1. Every year until about 1980 a slide rule competition was held in the State of Texas (US). The contestants had to complete a series of calculations in 30 minutes. As the competition was timed there was a premium on speed but  the marking system also required high accuracy. If the answer was accurate to three place of decimals, three points were awarded but if the answer was off by more than 2 places in the third significant figure no marks were awarded. Whilst other rules were allowed, and were used, the Pickett "Texas speed rule" was most popular.

3. The one sample test paper I have seen had 75 questions. It started with easy ones but  got more and more difficult. I give below three samples:

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3. Some of features which contributed to this rule's popularity for the competition were:

  • Range of scales limited to those needed for the test (no trig scales for example).
  • Clear and simple marking.
  • Same letter at left and right hand end of scales, for example K at both ends rather than K and x3 as found on some rules, anyone good enough to compete in the contest would know what the K scale was used for.
  • K scale on the stock and slider - many of the tests involved cubes and cube roots.

4. This rule is in Pickett's "eye-saver" yellow.

Front view
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Detail - front left
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Detail - front right
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Back view
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Detail - back left
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Detail - back centre
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Manufacturing date c 1960
Length 10"
Material Metal, Duplex
Scales K,A [B,K,CI,C]D,L
Cursor Plastic