Re: Gebr. Wichmann Berlin experts around? Wichmann Electro made by Nestler?
Andreas Faßbender
Hi Andreas,


Re: Gebr. Wichmann Berlin experts around? Wichmann Electro made by Nestler?
Rod Lovett
Hi Andreas,
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Peter Hopp (Slide Rules: Their History Modes and Makers Pg 235) thinks that Wichmann mainly sold other makers rules but may have made their own simple rules.) If you don't have the book (shame on you!) I can send you a copy of the relevant page. I'm sure Peter won't mind! P.S. If you don't mind searching for scale matches then why not us Herman's Archive. Goto https://sliderules.lovett.com/herman/hermansearch.html and click "Search" which will show you how to search for specified scales in the Archive. Best wishes, Rod
On 31052022 14:07, Andreas Poschinger wrote:
Hi,


Gebr. Wichmann Berlin experts around? Wichmann Electro made by Nestler?
Andreas Poschinger
Hi,
I've bought today in ebay a Wichmann Electro (please scroll down): https://www.ebay.de/itm/RechenschieberFaberCastellSchuberAlbertNestlerAGNo37/284827408443?mkpid=0&emsid=e11003.m43.l2649&mkcid=7&ch=osgood&euid=42742d5d30974b43910e0115c4b79b5a&bu=43204544845&osub=1%7E1&crd=20220531054053&segname=11003&sojTags=ch%3Dch%2Cbu%3Dbu%2Cosub%3Dosub%2Ccrd%3Dcrd%2Csegname%3Dsegname%2Cchnl%3Dmkcid&nma=true&si=pHY7Zj2yHqrPG%252F3w646Q0FWbzyA%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557 Nothing special with respect to the scales; standard Electro loglog layout as on Faber 378, LLs folded to e. Seemingly however it is no Faber. It has screws as Nestlers. It will come in a Nestler 37 box from Nestler AG times. I did not find another copy of this slide rule in the net yet. Anybody who knows about Wichmann slide rules and maybe especially this one? Made by Nestler? Ideas why there is no Wichmann box? Best regards Andreas PS: I still look for a wooden simplex model with sin and tan on slide bound to C and standard LL2 and LL3 scales bound to D on body. Any idea whether there is such a model around?


Magnifying glass on the backside of a simplex slide rule pre 1900
Andreas Faßbender
Hello all,
does anyone know a manufacturer who used a semicircular glass cylinder, on the back as a magnifying glass before 1900? Kind regards, Andreas


Re: Use of Inverse LogLog scales First resume
Andreas Poschinger
Hi,
I interpret Rods questions also like do we really need inverse LL scales? From my point of view not necessarily. In most practical cases I know about the use of LL scales as replacement is almost as effective. But what is really needed? One may say that a Mannheim is sufficient as well. Or for a long time there obviously was not seen a need to have a CI scale, also not on Rietzes, Electros and others. Since my Hemmi 149A I feel this to be the optimal layout for my need as long as hyperlog not needed, with inverted LL scales not necessarily needed. So a simplex slide rule with LL2 and LL3 as well as Trig on Slide bound to C/D would be sufficient. Thats why I started to play a lot with the Nestler 37 Electro. On the Nestler however it is a disturbing for me that the LL scale is bound to A. Which wooden or plastics simplex slide rule exists with A B C D, preferably but not neccessary CI, necessarily SIN TAN on slide both bound to C/D, L and ST not necessary, and necessarily LL2 / LL3 bound to D on body, LL1 ok but not necessary, prefereably but not necessary a second C on Trig side of slide? I remember the Graphoplex 640 but thats it. For those prefering TrigOnBody the very late Faber D Stab and Aristo BiScolar LLs with second S on slide may have been the most value for money duplex scale layout for general purpose; they do not have inversed LL scales. Which duplex sliderule models are compareably efficient with TrigOnSlide? Best regards Andreas


Re: Use of Inverse LogLog scales Part 5: Logarithms
Andreas Poschinger
Hi,
this part is now about the use for logarithms for numbers smaller than 1, that I've almost forgot. I still teach Bode (though in my practical time never applied) with the amplidude response be calculated by 20 log(U_a/U_e), with means that we take the ratio of output to input, e.g. of voltages, take the decadic logarithm of this ratio and multiply it in order to obtain so called Decibel (dB). Usually it is not necessary to actually calculate the logarithm, when knowing that 6dB corresponds to the ratio 2:1, 3db=1/2*6dB to the ratio sqrt(2:1), 2 dB to the ratio 1.26:1. By these all other values can be derived, e.g. 11dB = 4*2dB+3dB and thus corresponding to (1.25)^4 * sqrt(2) according to logarithmic calculation laws, which still can be calculated on a Mannheim layout without any LL scales. Thus so far I thought, that in my field logarithms were not really needed in slide rule times. In wikipedia I've however found that until the 70ies the Neper (Np) calculated by A/Np=ln(U_a/U_e) was dominant above dB and thenin the 70ies it has changed. Does anybody know about that from own experience? Neper would be simpler to be calculated on the sliderule, since we get rid of 20 times and a base which is not the Euler number e. Let's e.g. assume U_a=2.5V and U_e = 5V. Using LL02: Calculate 2.5/5 e.g. by C:5 to D:2.5; at C:10: result D:0.5 Cursor to 0.5 on LL02; result 0.693 on D (the  comes from e^0.1x, which es the expression calculated by LL02 from values X between 1 and 10 fed into D!) Using LL2: Calculate 5/2.5 e.g. by C:5 to D:2.5; at C:10: result D:2 Cursor to 2 on LL2; result 0.693 on D (the  comes from having inversed the ratio!) So we do not save time using LL2, we only can use a more direct recipe. For the sake of completeness: The LL scales can deliver logs of all kinds, so e.g. calculating 20*log(2) (decadic): First cursor then C:1 (or for other cases C:10) to base 10 on LL3; at 2 on LL2: 0.301 on C; C:1 to 3.01 on D; at C20: result 6.02 on D That is why I e.g. do not understand that the Studio wastes space on slide for an L scale, instead using this space e.g. for a second S scale. Any other usage for (inverse) LL scales? Best regards Andreas


Re: Use of Inverse LogLog scales Part 4: Hyperbolic functions
Andreas Poschinger
Hi,
indeed I lost at least one use case: logarithms of numbers smaller than 1. This I will put into part 5. Any other use cases lost? Hyperbolic functions are of some importance in transmission line problems. This I will not look upon. Another application of hyperbolic function is to calculate the geometry of suspension bridges or cables between electric towers. Chains (and ropes) follow what in direct German translation we would call "chain line" but in English actually catenary. cosh(x) = 1/2(e^x + e^(x)) so that for arbitrary catenaries something like b/(e^(x/a) + e^(x/a)) needs to be evaluated, and thus first e^(x/a) and e^(x/a). It is a mixture of the table building in part 4 and simple reading the inverse in part 1: a on C to D1 (or to D10); at C x e^(x/a) on LL3 and e^(x/a) on LL03 respectively on LL2/LL02 and LL1/LL01 for 1/10 and 1/100 of x between 1 and 10. For this application inverse LogLog scales considerably speed up calculation since calculation of the inverse is not needed. Though personally I've never seen cosh(x) unit paper the unit function approach should be also possible. The use for sinh and tanh=sinh/cosh would follow the same approach. Best regards Andreas


Re: Use of Inverse LogLog scales Part 3: Expressions containing e^(t/T)
Andreas Poschinger
Hi,
the third application is the computation of expressions containing e^(t/T), especially the calculation of tables of values for these functions. For this application the inverse loglog scales are not necessarily needed, but make it simpler to follow what happens by a more straight forward recipe. These e^(t/T) functions often occur as impulse or step response of technical system. If one e.g. changes the valve of a radiator in order to reduce a room temperature from 20 deg C to 15 deg C then the resulting temperature function will roughly be something like 15 + 5*e^(t/T). Depending on the room T may be something like 2h, so that we first need to compute x=e^(t/2) for all points in the table of values and then 15+5*x. The other way round, temperature from 15 to 20 would roughtly follow 205*e^(t/T), so that it is almost the same procedure. For all values of t in principle we need to repeat the following steps though the first step only has to be done twice: Set 2 on C to 1 on D (or 2 on C to 10 on D if out of range) Cursor to e.g. on 3 of C; on LL03 0.223 for t=3h; on LL02 0.861 for t=0.3h; on LL01 0.985 for t=0.03h Then cursor to next position until all t are evaluated. Next 15+5*x needs to be evaluated. Depending on taste +15 can be done in head so that only 5*x needs to be calculated: CI 5 to D1 (or to D10; for general setting of 5 *); at e.g. 0.861 on C 4.3 on D; in head 15+4.3 = 19.3 in total. Alternatively 15 could be factored out and calculation of 1+5 x /15 could be performed. Instead of inverse loglog scales also normal LL scales can be used by reading at the respective normal LL scale (thus reading e^(t/T)) and inserting this result into the second step by using CI scale: Set 2 on C to 1 on D (or 2 on C to 10 on D if out of range) Cursor to e.g. on 3 of C; on LL3 4.48 for t=3h; on LL2 1.162 for t=0.3h; on LL1 1.015 for t=0.03h Now we need to look on CI!: CI 5 to D1 (or to D10; for general setting of 5 * as before); at e.g. 1.162 (for t=0.3h) on CI 4.3 on D; in head 15+4.3 = 19.3 in total. This inverse loglog scales only help in order to have a slightly simpler recipe but not to save work in this use case. So even with inverse loglog functions table building is quite a lot work, so that uniform functions (in the example e^x) plot on paper were used. The actual results were obtained by scaling the x and y axis, e.g. in the example to write 20 instead of 1 on y and 15 instead of 0 on y, and 2h instead of 1 on x axis. By use of these uniform function papers as well as Bode paper and Smith charts paper most likely students in Germany could "survive" their studies without ever buying a high end slide rule comprising inverse loglog or even hyperbolic scales. The next part will be about hyperbolic functions. It is a special case of reading the inverse numbers as in case 1. Does anybody know more use cases for the inverse LL scales than those four mentioned so far? Best regards Andreas


Re: Use of Inverse LogLog scales Part 2: Arbitrary powers of numbers small than one
Andreas Poschinger
Hi,
I've forgot to mention arbitrary powers of numbers smaller than one which is maybe the most obvious use in most instructions. Let's look on 15*(0.5^3). If we only have LL1LL3 then we need to calculate 15/((1/0.5)^3) which involves at least one value transfer more than using inverse LogLog scales: 0.5 on C to 10 on D; at C1 read 2 on D (Calculate inverse of 0.5) Cursor to 2 on LL2, 10 on C to cursor; at 3 on C: 8 on LL3 C8 to 10 on D; (at 1 on C 0.125 on D); at 15 on C 1.875 on D With inverse loglog scales it gets slightly simpler, with only one instead of two value transfers: Cursor to 0.5 on LL02; C10 to cursor; at 3 on C: 0.125 on LL03 (going to left means her to switch to the scale LL0x+1) C1 to 0.125 on D; at C15: result 1.875 on D Remark: I strictly use C and D because I use a Studio for these recipes. If you use a slide rule with inverse and folded scales on its loglog side you also may use these scales of course. Unfortunately DI scale virtually never is on LogLog side, so that when starting with an inverse number is appropriate then the old fashened replacement needs to be used by setting this number on C to one of the indices of D. Remark: Intermediate results on LL scales always need to be transferred for following calculations. Best regards Andreas


Re: Use of Inverse LogLog scales Part 1: Absolute inverse numbers
Andreas Poschinger
PS: Ive meant I hope that I do not bore you.... ... allready late;
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technically it is hopefully ok!) Good night! Am 18.05.2022 um 22:09 schrieb Andreas Poschinger:
Hi,


Use of Inverse LogLog scales Part 1: Absolute inverse numbers
Andreas Poschinger
Hi,
I hope that I not borrow, since by sure all can be also read in manuals. The most simpliest use of inverse LogLog scales together with nomal LogLog scales are absolute inverse numbers. Absolute, because there is no need to take care about the decimal point. If you look e.g. for the inverse of 100 then place your cursor on 100 on scale LL3 in order to read 10^2 or 0.01 deending on engravings on scale LL03. Or 25 on LL3 to read 0.04 on LL03. Just always use the corresponding scale, so LL1 woth LL01, LL2 with LL02 and LL3 with LL03. Of course it also works to loo for a number smaller than 1 on an LL0x scale and read the inverse on LLx. Best regards Andreas


Re: lologs and ilologs
Andreas Poschinger
Hi Rod,
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today I have an online meeting. I will write something together the next days. The mean usages for me right now are: Inverse numbers in their precise value without taking care of the decimal point Calculation of e^(t/T) which is the important function for many technical problems and Calculation of cosh / sinh / tanh if those scales are not existant. Best regards Andreas Am 18.05.2022 um 20:36 schrieb Rod Lovett:
Hi Andreas,


Re: lologs and ilologs
Rod Lovett
Hi Andreas,
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I was merely interested in the uses for an inverse log log function. Regards, Rod
On 18052022 11:27, Andreas Poschinger wrote:
Hi Rod,


Re: lologs and ilologs
Andreas Poschinger
Hi Rod,
to be honest, when flying over the paper I did not find the point in the paper other that somehow the invention history of the inverse Loglog scales is described. Did I miss something? Or is question simply why we could need inverse LogLog scales? Best regards Andreas


Re: lologs and ilologs
Rod Lovett
Hi Andreas,
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I think that you are correct. I hadn't associated the "i" with inverse. Now I would like to see some useful applications of these ideas! Best wishes, Rod
On 17052022 21:34, Andreas Poschinger wrote:
PS: I found in your literature search an article:


Re: lologs and ilologs
Andreas Poschinger
PS: I found in your literature search an article:
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Author Bob Otnes Title Log Log Scales  Revisited Location Journal of the Oughtred Society Vol. 4, No. 1, March, 1995 Pg 9 This fits quite well. So I believe my theory about the meaning of the sentence may be valid... Am 17.05.2022 um 21:59 schrieb Andreas Poschinger:
Hi Rod,


Re: lologs and ilologs
Andreas Poschinger
Hi Rod,
I did not look into the old messages (due to time restriction...); this may however senseful to solve the puzzle in order to know what Bob has triggert to write this. May Bobs sentence mean something like: Seeing the current interest in log(arithm)s and co()logarithms [i.e. logarithms of inverse numbers 1/x], it might be that some readers would be interested in a short (50k pdf) paper that I have written on lo(g?)logs and i(inverse?)lo(g)logs. ? Best regards Andreas


lologs and ilologs
Rod Lovett
Hello Everyone,
Back in 2006 ( ISRG #29477 ) Bob Otnes (sadly no longer with us) wrote the following: Seeing the current interest in logs and cologs, it might be that some readers would be interested in a short (50k pdf) paper that I have written on lologs and ilologs. Does anyone know what lologs and ilologs are and what they are/were used for? I'm pretty certain this is not a joke! Best wishes, Rod


Re: Do any duplex circular slide rules have the front and back center disc connected?
Mark Davis
I must add that, while the discs are connected front to back, there doesn't appear to be any useful way to chain calculations from front to back. In any case, neither the disk nor outer ring are aligned on the Dempster model 'AA' I have. They are almost aligned on my B.C. Boykin RotaRule 510, but this appears to be coincidental.
Mark Davis


Re: Do any duplex circular slide rules have the front and back center disc connected?
Mark Davis
The Dempster RotaRule model 'A' and model 'AA' circular slide rules have a single central disk that is functional on both the front and back of the rule. These slide rules were made primarily of "Vinylite" plastic, introduced by the company that later became Union Carbide about a year before the first RotaRule model 'A' was manufactured in 1928. This Oughtred Society article, by W. Richard Davis, provides a good deal of detail on the design and construction of the Dempster RotaRule models: https://www.oughtred.org/jos/Davis_DempsterRotaRule.pdf
After the Dempster patents expired, a different manufacturer, B.C. Boykin, produced a very similar product in two models; the "RotaRule 510", and "RotaRule 560". The model 510 has decimallydivided trig scales, vs. the minutesecond divisions on the model 560 trig scales. A key feature of both the Dempster and B.C. Boykin designs are threecycle spiral C/D scales, for an advertised scale length of 50 inches. Additionally, there is a 3cycle spiral LL1/LL2/LL3 scale and a 3cycle spiral LL01/LL02/LL03 scale in the inner rings on the disk, on the same side as the spiral C/D scales. Mark Davis

