1950 Hebrew ISRAEL Engineer SLIDE RULE Electric ELECTRICITY Moveable CALCULATOR

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Seller: judaica-bookstore ✉️ (2,805) 100%, Location: TEL AVIV, IL, Ships to: WORLDWIDE, Item: 276313696229 1950 Hebrew ISRAEL Engineer SLIDE RULE Electric ELECTRICITY Moveable CALCULATOR.    DESCRIPTIONHere for sale is an EXTREMELY RARE original vintage HEBREW CARDBOARD SLIDE RULE which was MADE IN ISRAEL in the 1950's up to the 1960's.  The Hebrew SLIDE RULE is a professional tool for ENGINEERS , Computing and detailing the requiered ELECTRICAL - ELECTRICITY data . Written in HEBREW . Each of its two faces provides the technical data of different kinds of DATA . Measures around 5 x 10". The vintage SLIDE RULE is USED . It is in very good condition. Working nicely. ( Pls look at scan for accurate AS IS images ) .Will be sent inside a protective rigid packaging .   AUTHENTICITYThe ISRAEL HEBREW SLIDE RULE is fully guaranteed ORIGINAL from ca 1950's - 1960's , It is NOT a reproduction or a recently made product or an immitation , It holds a life long GUARANTEE for its AUTHENTICITY and ORIGINALITY.   PAYMENTS : Payment method accepted : Paypal & All credit cards. SHIPPMENT : SHIPP worldwide via registered airmail is $ 25 . Will be sent inside a protective packaging . Handling aroud  5-10 days after payment.  Electrical Slide Rules Background Electrical slide rules were designed to perform two types of calculations: Efficiency of motors and dynamos Voltage loss in cables. For motors the efficiency was the ratio of the mechanical energy output divided by the electrical energy input; in the case of dynamos it was the ratio of the mechanical energy input divided by the electrical energy output. Apart from the fact that the units of energy were different, horse power for mechanical energy and watts for electrical energy, the calculation was basically very simple. The calculation of voltage loss in cables was not much more complicated. The voltage loss was given by ohms law:     volts = current (amps) * resistance (ohms) The resistance was given by:     resistance (ohms) = length * resistivity / sectional area. In metric units the dimensions of resistivity are ohms metre. There are however a few complicating factors that users of rules should be aware of: There were two different units for horse power. The first, used in the UK/US, was based on the energy to lift a 550 pound weight through 1 foot in one second and was equivalent to 746 watts; the second, used in continental Europe, was based on the energy to lift 75 kilograms through 1 metre in 1 second and was equivalent to 736 watts. The latter is sometimes marked as PS, from the German Pferdestärke. Different units of area were used. Normally in the metric system the sectional area of the cable was square millimetres, in the UK/US system it could be either square inches or circular mils. The latter was a slightly unusual unit in that it was based on the diameter in 1/1000s of an inch squared. In the US gauge sizes were sometimes used. Since calculations using basic units (e.g. 1 square inch and 1yard) would result in voltage values very different to those found in real life, the rules were usually set up for a combination of more usual units (e.g. 10 mm2 and 10 metres). Although in the above equation the resistivity is used, the use of the inverse, the conductivity, was more common. The resistance of a metal varies with temperature. Sometimes the resistivity/conductivity is expressed as the value at 0 °C ( 32° F) and at other times at 20 °C (68° F). Typical values of resistivity for copper are 1.56 * 10-8 ohms metre at 0 °C and 1.67 * 10-8  at 20 °C . The equivalent values of conductivity are 6.41 * 107 and 5.98 * 107. On some rules there is a gauge point at 28.7 which is considered to be 0.5 * conductivity. Which does not quite agree with the figure of 5.98; another complicating factor and one I can not yet explain. Some rules have gauge points for the use of metals other than copper, for example aluminium. The rules These instructions are based on the rules listed below with their units of measurement : Rule Length Area Unique Electrical yards circular mils Thornton/P.I.C. 4866 10 yards .01 sq. inches Thornton/P.I.C. No 131 10 yards .01 sq. inches Faber Castell 378 10 metres 10 sq. mm. Faber Castell 398 10 yards 10000 circular mils Faber Castell 1/98 Elektro 10 yards 10000 circular mils W&G Dualface comprehensive 432 1 yards .001 sq. inches Graphoplex Electro 650 metres sq. mm Most of the rules have special scales for efficiency and voltage loss. Sometimes these are set in the well of stock The example below comes from the Thornton/PIC 131. The scales for efficiency are in the upper part (dynamo in black and motor in red). The lower scale is for voltage loss. To read the values of the scales in the well of the stock,  a variety of different methods were used. Some of these were based on "chisel" type cursors (which owed something to the early cursors). I give below four variants. Of these the most convenient is the latest of them - on the Thornton 131. The fourth image, the Aristo, was provided after I had developed this site and has a similar cursor to the Thornton. On this rule it is possible to see not only the cursor but also the mark D/M for dynamo/motor efficiency and different gauge marks for Copper (Cu) and Aluminium (Al) wire. Thornton/PIC 4866 Faber Castel 398 Thornton 131 Aristo Elektro Other rules had the efficiency and voltage scales set below the principal scales. The example given below is from the Graphoplex Electro. The W&G 432 used a similar approach. The Unique is the only one which does not have special scales for efficiency and voltage, relying instead on gauge points. Most of the rules have additional scales for the change of resistance with temperature. Those on the Unique Electrical were particularly extensive covering the range from 0 °C to 300 °C. The above image also shows the gauge point marked W used for efficiency calculations. Most of the rules also mark the scales to be used for kW and HP or PS. In passing it is interesting that the French rule also uses PS rather than the French equivalent CV (chevaux vapeur). I have to confess to being unsure as to why electrical rules often had the scales in the well of the stock, particularly as the Unique manages perfectly well without them. One theory on the egroups forum was the it meant a basic design of stock and slide could be used without the need for re-tooling;  a more cynical explanation was that it was done to make them look more special and so attract a premium price! Dynamo Efficiencies The basic equation is:     Efficiency = Electrical energy output / Mechanical energy input. Example:    Calculate the efficiency of a dynamo which gives an output of 13.5 kW for 21.0 H.P. Faber Castell Elektro    Set 2.10 on the B scale against 13.5 on the A scale.    Read the efficiency, 86.2% on the Dynamo efficiency scale. As a check, 21.0 multiplied by .746 is 15.67 and 13.6 / 15.67 is 86.2 Most of the other rules, including those with the scale to one side operate in the same way. For example the same calculation is shown below on the Graphoplex. It will be seen that the answer is not the same as the above. This is because the Graphoplex used the continental horse power. The answer in this case is 88%. To perform the same calculation on the Unique Electrical it is necessary to use gauge points.     Set 33.4 on D scale against 51.6 on C scale.     Read the efficiency, 86.6% on the d scale, opposite the gauge point N on the c scale. Motor Efficiencies In this case the basic equation is:     Efficiency = Mechanical energy output /Electrical energy input. Example:    Calculate the efficiency of a motor which develops 150 H.P. for 128 kW. Since for most rules the calculations of motor efficiency are simple mirror of the calculations for dynamo efficiency I give below the method for the W&G 432.    Set 128 on the kW scale against 150 on the HP scale.    Read the efficiency, 87.5% on the Motor efficiency scale, opposite the gauge point. For an example of the calculation on a rule with scales in the well of the stock I will consider a Thornton 131.    Set 150 on the HP scale against 128 on the kW scale.    Read the efficiency, 87.5% on the Motor efficiency scale. Finally let us carry out the calculation on a Unique. Set the horse power on the D scale against 128 on the C scale. Read the answer, 87.5%, on the d (equivalent to the DF scale) or D scale opposite the " gauge mark. Voltage Drop Background Voltage drop is given by the formula:     V = (I x L )/ (c x A) Where:     V is voltage drop (volts)     I is the current (amps)     L is the length (yards)     C is the conductivity of copper     A is the section of the conductor. Typical units for this are square inches, square millimetres and circular mils. Circular mils is calculated from the diameter of the wire in thousandths of an inch squared. The calculations all assume copper wire. Example: Calculate the volt drop in a copper conductor 131 (119.7 m) yards long, 0.14" (3.56 mm) diameter, carrying a current of 20.4 amps. The area of a wire 0.14 diameter is .0154 in2 , equivalent to 9.94 mm2 and 19600 circular mills (=140 * 140). Thornton PIC 131 The Thornton is set up for current in units of 10 amps, lengths in units of 10 yards and areas in units of .01 sq. in. So:     Align 1 on the B (length and area) and scale against 2.04 (2.04*10amps = 20.4 amps) on the A (current) scale.     Cursor to 13.1 (13.1 * 10 yards = 131 yards) on the B (length and area) scale.     Align 1.54 (1.54 * .01 sq. in = .0154 sq.in).on B (length and area)scale.     Read the answer 4.24 volts in the well of the stock. Faber Castell 1/98 The Faber Castell 1/98 is set up for units of 10 amps, 10 yards and 10000 circular mils.     Align 1 on the B (length and area) and scale against 2.04 (2.04*10amps = 20.4 amps) on the A (current) scale.     Cursor to 13.1 (13.1 * 10 yards = 131 years) on the B (length and area) scale.     Align 1.96 (1.96 * 10 000 circ. mils = 19600 circ. mils)on B (length and area)scale.     Read the answer 4.14 volts in the well of the stock. Faber Castell 378 The Faber Castell 378 is set up for units of 10 amps, 10 metres and 10 mm2.     Align 1 on the B (length and area) and scale against 2.04 (2.04*10amps = 20.4 amps) on the A (current) scale.     Cursor to 13.1 (11.97 * 10 metres = 119.7 metres) on the B (length and area) scale.     Align 0.994 (0.994 * 10 mm2 = 9.94 mm2 ) on B (length and area) scale. The "volt" cursor is past the end of the rule so align the cursor with 100 and the move the slide so that the 1 aligns with the cursor.     Read the answer 8.5 volts in the well of the stock. As can be seen the answer is twice the value given by the other rules and should be multiplied by 0.5. This appears to be a common feature of all "metric" electrical rules. A similar result is obtained using the Graphoplex. Unique Electrical    Area is 1402 = 19600 circular mils.     Set 1 on C against 2.04 on D.     Move cursor to 1.31 on C.     Move 1.96 to the cursor.     Read volt drop, 4.16, above V on the c scale. W&G 432     Align 1.54 on area/length scale against 2.04 on current scale.     Align cursor with 131 on area/length scale.     Answer 4.19 volts under cursor on volt scale. Variation of resistance with temperature To solve:    A copper wire has a resistance of 2.8 ohms at 20 ° C (68 ° F). What is its resistance at 5 ° C (41 ° F) and 104 ° F (40 ° C). Unique Electrical    Set cursor to 20 ° C on lower temperature scale.     Set 28 on C scale to cursor.     Move cursor to 5 ° C on lower temperature scale.     Read 2.63 ohms under cursor on C.     Move cursor to 104 ° F on upper temperature scale.     Read 3.01 ohms under cursor on C. Faber Castell Elektro    Set the cursor to 2.8 on the A scale.     Set 68 ° F on the temperature scale to the cursor.     Move the cursor to 41 ° F (= 5 ° C).     Read 2.63 ohms under cursor on A.     Move the cursor to 104 ° F.     Read 3.01 ohms under cursor on A.**** ELEKTRO RULES Their use and scales Robert Adams BE Introduction Of the speciality rules, perhaps the most ubiquitous is the “Elektro” rule, almost every manufacturer of slide rules produced an Elektro rule. This paper examines the design of such rules and poses a few questions on the layout of the scales and their overall usefulness. Definition of an “Elektro” Rule A rule to aid the electrical engineer in solving specific problems. It is usually a rule with the scales of the standard Rietz system, supplemented with Log Log scales, motor/dynamo efficiency scales and a scale for voltage drop calculation. The calculations are normally limited to power system frequencies i.e. 0 (Direct Current) to a few hundred Hertz (Hz). Slide rules designed for Electronic engineering do exist; their main forte is the calculation of impedance of circuit elements in the higher frequency ranges i.e. 0.1 to 100 MHz. This paper concerns the rules that were primarily used in electrical engineering and not electronic engineering. Electrical Engineering Problems they where intended to solve The first “Elektro” slide rules were primarily designed to perform two types of calculations: • Efficiency of motors and dynamos • Voltage loss in cables For motors and generators (dynamos) the efficiency was, in the case of a motor, the ratio of the mechanical energy output divided by the electrical energy input. In the case of a generator, it was the ratio of the mechanical energy input divided by the electrical energy output. The calculation was basically very simple apart from the fact that the units of energy were different, HP (horsepower) for mechanical energy and KW (kilowatts) for electrical energy. The calculation of voltage loss in cables was not that much more complicated. The voltage loss was given by Ohms law: V = I * R (Volts = current (amps) * resistance (ohms)) The resistance was given by: A R L δ = * (Resistance (ohms) = length (m) * resistivity (ohm-metre) / sectional area (m2 )) But as usual in the real world, different countries and cultures use many different measurement units which invariably add a few complicating factors that require some explanation. There were at least two different units for horsepower. The Imperial system, used in the British Commonwealth countries and the US, was based on the required energy to lift a 550 pound weight through 1 foot in one second and was equivalent to 746 watts. The second, used in mainly in Continental Europe i.e. users of the metric system, was based on the energy to lift 75 kilograms through 1 metre in 1 second and was equivalent to 736 (or even 735) watts. The latter marks are usually shown as PS on Page 2 European rules and are derived from the German word Pferdestärke. The difference in the number of watts for the PS mark is due to the derivation of the unit using 9.8 or 9.81 m/s2 for the gravitational constant. Different units of area were also used. In the metric system, the sectional area of the cable was normally given in square millimetres. In the Imperial system it could be either square inches or circular mils. This latter unit was slightly unusual as it was based on the diameter of the conductor, in 1/1000ths of an inch squared. Calculations using the base measurement units (i.e. inch, yard, metre) would result in values that were not usually practical for real world observation and more usual units of 10mm2 and 10 metres or 10yards and 0.01sq. inches were used. The resistivity/conductivity can be expressed as a value either at 0°C (32° F) or more usually at 20°C (68° F). Typical values for copper are 1.67 * 10-8 ohm-metres resistivity at 20°C or a conductivity of 5.98 * 107 at the same temperature. As electrical conductors could be made of differing purity and alloys of copper it should be stressed that the specific values for resistivity and conductivity are not unique. Many manufacturers placed gauge marks for conductor on their rules but usually the calculator needed to be aware of the specific properties of the cable they where using. Some rules have gauge points for the use of metals other than copper. For example aluminium, is particularly important in the modern world where it has nearly taken over from copper as the electricity distribution industry conductor of choice. The First Elektro Slide Rule? Here I have relied upon the books by Peter Hopp ref [6] and Dieter von Jezierski ref [5] for information on catalogues, registered designs and also patents. The earliest mention of a patent for a slide rule for electrical calculations is the 1890 patent number 1302 awarded to a Mr A.P. Trotter for a slide rule for electrical calculations with two slides – “Wiring Slide Rule”, it is unknown whether an actual rule based on this patent was actually produced. The earliest reference to an actual “Electro” (sic) was in Dieter’s book “Slide Rules. A Journey through Three Centuries”. In the list of Registered Designs, a design number of 334146 is registered to Nestler in 1908 for the Slide Rule Electro 32. In his book ref [6] Peter Hopp refers to a “Slide rule for electrical calculations” which was produced by A.E Colgate of New York in 1901, however the scale layout is unknown. Peter Hopp also mentions two other American rules which were made by the Lewis Institute of Chicago and called the “Woodworth’s sliderule for electrical wireman” and the “Woodworth’s sliderule for calculations with volts, amperes, ohms and watts”. Both rules according to Hopp date from 1909, however again the scale layout of these rules is unknown. The earliest example in the United States of an actual rule for electrical engineering is the Roylance slide rule by Keuffel and Esser in their 1913 catalogue (more correctly the addendum to the 1913 catalogue). A fellow collector Mr David Rance has in his collection an early A.W. Faber Elektro (398-like) with design numbers DGRM 271169 & 247514, this rule confirmed by Mr Guus Craenen in his forthcoming book is actually a A.W. Faber 368 rule ( note, this is not referenced in either ref [5] or [6]) . Both Registered Designs are credited to A.W. Faber for the years 1906 and 1905 respectively in ref [5]. The 271169 DRGM refers to a cursor extension and not to any specific electrical scale, the 247514 however refers to an index edge at the end of the slide. This index edge is the first such mention of what was to become the defining feature of an Elektro rule, note that this DRGM dates from 1905. There is also evidence of a Dennert & Pape rule, the number 15, which I believe was produced in 1905 (again confirmed by Mr Guus Craenen) which incorporated elektro scales in the well. This rule also incorporated log-log scales on the front of the rule according to the principles of the DRGM 148526 of 1901 awarded to Mr W. Schweth. This rule which had electrical scales in the well and log-log scales on the body of the rule would become the spirit of the Elektro rule for the next 70 years, alas I do not have a scan of the rule but by the courtesy of Mr Rance and Mr Craenen, I can show the Faber 368 and Nestler 32.    ebay5279

  • Condition: Used
  • Condition: The vintage SLIDE RULE is USED . It is in very good condition. Working nicely. ( Pls look at scan for accurate AS IS images ) .
  • Country of Manufacture: Israel
  • Type: ELECTRICITY SLIDE RULE - CALCULATOR HEBREW ISRAEL
  • Brand: MADE in ISRAEL SLIDE RULE / CALCULATOR
  • Country/Region of Manufacture: Israel
  • Time Period Manufactured: 1930-Now

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