Lawrence 10-B 10" Mannheim
Lawrence 10-B 10" Mannheim
Speaking of inexpensive slide rules, Lawrence, of Peru, Indiana, made very inexpensive slide rules (painted wood, printed scales) for students. This one has a magnifying cursor, which is kind of unusual for a cheap slide rule.
I have two of these. The case of one of them is integrated into the cover of a hardcover book, "The Slide Rule and How To Use It" by Hobart H. Sommers, Harry Drell, and T. W. Wallschlaeger. Grosset & Dunlap, 1942.
Lawrence 10" Mannheim
Lawrence Engineering Service changed their name to Engineering Instruments in 1947, so even though this slide rule has a different label than the one above, they're both from the same company. I have two of these. This slide rule was SO cheap that it didn't even come with instructions - the box was labeled "For instructions see page 95 Mathematics Made Simple Self-Teaching Encyclopedia"!
Acu-Rule No. 10-D, 10" Mannheim with Magnifying Cursor
This is also a very cheap slide rule; however, it has a magnifying cursor to make reading it easier.
Acu-Rule started out as Festus Manufacturing Company. They changed their name to Acu-Rule in 1940, and started producing slide rules under the name Acu-Math in 1950. In 1968, they sold out to Sterling Plastics. (Much more detail here.)
Acu-Math No.1200, 5" Mannheim
I'm not sure if it's proper to call this a Mannheim slide rule or not: while the scales are right (K A[B CI C]D L, S T on back, actually a "polyphase" Mannheim because of the CI, K, and L scales), its simplex design isn't what I usually think of as a Mannheim.
At first I thought the extra hairlines on the cursor were for some mathematical use; they seem to be at 0.86 and 1.16 times on the C/D scales, and 0.74 and 1.35 on the A/B scales. I finally decided they were there because the end brackets on the stator prevent the cursor from being moved far enough to bring the center hairline to bear on the ends of the scale.
Aristo Nr. 0903 Scholar, 10" Simplex
Aristo is a German company; they made very nice slide rules. I like this rule because it is so colorful. All plastic, it probably dates to the 1960's.
C-Thru No. 88 and No. 27 Mannheim Slide Rules
These two slide rules are bottom-of-the-line slide rules, being made from folded plastic. One is 10" and the other 6". They're interesting because the inch and centimeter rulers are on the slide, which has to be removed from the stator for the rulers to be used. I wonder how many lost slides that produced?
Unknown non-Logarithmic slide rule, 12" Simplex
This isn't really a slide rule, as the scales are linear, not logarithmic - which is to say, they're for adding and subtracting, not multiplying and dividing. But it looks like a slide rule, so that is what I call it (it beats "thingie"). I have no idea what it is for.
© 2003 W. E. Johns