The Museum of HP Calculators

HP Forum Archive 21

 trig scales on the Post Versalog slide ruleMessage #1 Posted by Al on 6 Sept 2013, 4:38 p.m. If anyone here remembers such things, they still have their uses, please clarify the following. Do the trig scales on this slide rule read degrees and decimal degrees, or do they read degrees and minutes. A manual I have seems less than clear on this point.

 Re: trig scales on the Post Versalog slide ruleMessage #2 Posted by Kimberly Thompson on 6 Sept 2013, 6:14 p.m.,in response to message #1 by Al AL From page number six of my 1951 edition sliderule manual the VersaLog slide rule, "The Cos S scale is used to obtain sine and cosine functions of angles and is graduated in degrees and decimals of degrees". Hope this helps. BEST! SlideRule

 Re: trig scales on the Post Versalog slide ruleMessage #3 Posted by Al on 6 Sept 2013, 7:46 p.m.,in response to message #2 by Kimberly Thompson Kimberly: Now that you mentioned it, thank you, looking at my copy of the 1951 instruction book, page 6, second paragraph, I see what you mentioned. Must have passed it by several times, which is a problem with instruction books and some people. The books have to be read carefully. I assume the other trig scales read the same way, degrees and decimal degrees. Thanks again. Al

 Re: trig scales on the Post Versalog slide ruleMessage #4 Posted by Garth Wilson on 6 Sept 2013, 8:09 p.m.,in response to message #3 by Al You should be able to tell just looking at the divisions. For example, if you look between the marking for 6° and 7° on the S scale, do they divide the space up in to 10 or some multiple of it, or into 6 or some multiple of 6?

 Re: trig scales on the Post Versalog slide ruleMessage #5 Posted by Kimberly Thompson on 6 Sept 2013, 8:19 p.m.,in response to message #3 by Al Al You're welcome. I had a SENIOR MOMENT on an earlier post. BEST! SlideRule

 Re: trig scales on the Post Versalog slide ruleMessage #6 Posted by Eddie W. Shore on 6 Sept 2013, 11:09 p.m.,in response to message #1 by Al Quote: If anyone here remembers such things, they still have their uses, please clarify the following. Do the trig scales on this slide rule read degrees and decimal degrees, or do they read degrees and minutes. A manual I have seems less than clear on this point. According to the slide rule for the Accumath slide rule, the scale is in degrees. I can't imagine a slide rule where the trig scales are in degrees-minutes-seconds.

 Re: trig scales on the Post Versalog slide ruleMessage #7 Posted by Eamonn on 8 Sept 2013, 1:05 a.m.,in response to message #6 by Eddie W. Shore Hi Eddie, The K&E 4080 and 4081 slide rules are basically the same except the 4080 is a Log Log Duplex Trig rule (i.e., the trig scale is in degrees-minutes), while the 4081 is a Log Log Duplex DeciTrig rule (i.e., the trig scale is in decimal degrees). An example of the 4080 scale can be seen here. Check out the T, ST and S scales, which are marked in degrees and minutes. The 4081 equivalent can be seen here, where the same scales are in decimal degrees. Best Regards, Eamonn.

 Re: trig scales on the Post Versalog slide ruleMessage #8 Posted by Kimberly Thompson on 8 Sept 2013, 9:30 a.m.,in response to message #7 by Eamonn the K&E 4100-Stadia HC scale is Degrees.Minutes. Thanks for the cross references, BEST! SlideRule

 Re: trig scales on the Post Versalog slide ruleMessage #9 Posted by Bill (Smithville, NJ) on 8 Sept 2013, 1:14 p.m.,in response to message #7 by Eamonn Wow, I grew up using a Post Versalog and just assumed that all slide rules used similar scales. Never really thought about them having decimal degree versus degree/minute scales. Turns out that a lot of the Post Slide Rules also have degree/minutes including the little 5" one I have, Model 1441. Just take a look at the Post scales at following site - some have decimal degrees, many have degree/minutes: I guess you would need to be careful if you were used to one type of rule and then borrowed a friend's rule and didn't notice the difference. Bill

 Re: trig scales on the Post Versalog slide ruleMessage #10 Posted by Palmer O. Hanson, Jr. on 10 Sept 2013, 11:47 a.m.,in response to message #9 by Bill (Smithville, NJ) If you think about it you will realize that it is easy to enter degrees and minutes on a Decitrig slide rule. One simply recognizes that if a degree is divided into ten parts then each part is worth six minutes.

 Re: trig scales on the Post Versalog slide ruleMessage #11 Posted by Derek Walker (UK) on 11 Sept 2013, 3:13 a.m.,in response to message #9 by Bill (Smithville, NJ) Quote: Never really thought about them having decimal degree versus degree/minute scales. Turns out that a lot of the Post Slide Rules also have degree/minutes including the little 5" one I have, Model 1441. Just take a look at the Post scales at following site - some have decimal degrees, many have degree/minutes: Despite having used slide rules at school and university, and having collected a number in more recent years, I hadn't noticed this difference either.Of the six slide rules I have at work, only one (a Faber Castell) has minutes, the others (from Germany, Japan and USA) all use decimal degrees.I have some more at home, I will be interested to see how they compare, including the British Thornton rule I used at university.

 Re: trig scales on the Post Versalog slide ruleMessage #12 Posted by Palmer O. Hanson, Jr. on 14 Sept 2013, 3:50 p.m.,in response to message #1 by Al The offering of an option to purchase a slide rule with either trig or decitrig scales isn't the only curious situation which has occurred with the trig scales on slide rules. Does anyone know why the trig scales which went with the Mannheim devices used the S scale with the A and B scales but used the T scale with the C and D scales. I do understand that the sine on the S scale covers the range from 0.01 to 1 while the tangent on the T scale covers the range from 0.1 to 1, and that one can use the left hand portion of the S scale to obtain a reasonable approximation to the tangent. The arrangement means that if one wants to calculate sinAtanB one has to read a result from one scale and transfer it to another scale. I admit that the user can circumvent that by calculating sinAsinB/cosB. But why didn't they just make the S scale range from 0.1 to 1 to work with the C and D scales, and let calculation of the sine or tangent over the range from 0.01 to 0.1 be done with a conversion of the input angle to radians, which is essentially what the ST scale provides on later slide rules? Does anyone know why the so-called Reitz system moved the trig scales from the slide to the frame? Some texts suggest that the Reitz arrangement is easier to use, but I don't believe it.

 Re: trig scales on the Post Versalog slide ruleMessage #13 Posted by John I. on 15 Sept 2013, 6:01 a.m.,in response to message #12 by Palmer O. Hanson, Jr. I have a Sun Hemmi 'vectolog' P253 which I bought a few years ago because it had an interesting arrangement - inverse sin and tan scales. As in, if you look up 30 degrees on the SI scale you find '2' on the C scale (and hence 0.5 on the CI scale). This makes some trig work easier - e.g. the sin rule (a/Sin A) = (b/sin B) =(c/sin C) - so this slide rule is meant to give you 1/(sin A) etc. directly. My old brain found it hard to adapt however!

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