1936—A BANNER YEAR FOR STRAIN GAGES AND EXPERIMENTAL STRESS ANALYSIS—AN HISTORICAL PERSPECTIVE

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  • by Peter K. Stein

    1936A BANNERYEAR FOR STRAINGAGES AND EXPERIMENTAL STRESSANALYSISANHISTORICALPERSPECTIVE

    THIS PAPER IS DEDICATED TO THE MEMORY OF:WILLIAM M. MURRAYAPRIL 24, 1910 AUGUST 14, 1990

    It was in Bill Murrays course on experimental stress analysisthat I first was introduced to strain gages, brittle coatings,and photoelasticity. I was his graduate assistant and, later,instructor from 1950 to 1955. He was my teacher, mentor,supporter, and friend. We first met at Massachusetts Instituteof Technology (MIT) in spring 1949. He was also a founder ofthe Society for Experimental Stress Analysis, now Society forExperimental Mechanics, and was invited by BLH Electronicsto attend the early meetings of Western Regional Strain GageCommittee as its honorary chairman, to lend distinction andcredibility to this unusual group.

    Bill came to MIT in 1932 with his BS degree in mechanicalengineering from McGill University. He received his MS andScD degrees from MIT in 1933 and 1936 and remained thereuntil his retirement in 1973 when he was appointed professoremeritus of mechanical engineering at MIT and then visitingprofessor of civil engineering at University of Houston, in Texas.

    He was a great educator in experimental stress analysis,offering the first course on photoelasticity, strain gages, andbrittle coatings in a college/university curriculum, and thefirst summer sessions1- and 2-week courses for practicingengineers, scientists, and managers from industry starting in1953 and continuing for two decades, first at MIT and later atUCLA and in many other locations in the USA and in Mexico.SESA was run out of his office for over a decade. His profes-sional contributions and honors are legion. SEMs annualMurray Lecture is awarded in his honor.

    To this pioneer and educator in experimental stress analysis,I humbly dedicate this paper of a history to which he contrib-uted so much!

    STRAIN GAGE TYPES INVENTED OR USED ANDTHE CAST OF CHARACTERS

    d Carbon strain gagess Unbonded

    j McCollumPeters telemeterBurton McCollum (18801984)Orville S. Peters (18831942)Francis G. Frank Tatnall (18961981)

    s Bondedj Liquidd Aquadag

    Edwin H. Hull (19021964)j Solidd Charles M.Kearns, Jr. (1915, living inTucson, AZ)

    d Metallic strain gagess Unbonded wire gages

    j Roy W. Carlson (19001990)s Bonded wire gages

    j California Institute of Technology, Pasadena, CA

    d Edward E. Simmons, Jr. (19112004)d Gottfried Datwyler (1906 July 30, 1976)d Donald S. Clark (19061976)

    j MIT, Cambridge, MAd Arthur C. Ruge (19052000)d J. Hans Meier (1913, living in California)d Frank F. Hines (19132001)d William M. Murray (19101990)d Alfred V. A.V. de Forest (18881945) together

    withd Wilfrid L. Bill Walsh (18931967)

    s Magnafluxs Scratch gages Electrical strain-sensitive (ESS) strips Bonded wire gage (catalyst)s Stresscoat brittle coating (catalyst)

    s Printed circuitsFoil strain gage precursorj Earle Kent (19101996)j LeRoy Paslay (19072001)j Paul Eisler (19071992)

    d Brittle coatingss Stresscoatj Greer Ellis (19101997)

    d Mechanical strain gages in use at the time and for manyyears laters De Forest scratch gages Huggenberger extensometer

    SUMMARY AND OUTLINE FOR 1936

    SpringE.H. Hull of General Electric Co. applies Aquadag, a graph-ite emulsion in water, to be painted on surfaces for strainmeasurement. It has many problems, but it is used.

    April 7Roy Carlsons patent on a telemetric device based onunbonded strain-sensitive wires is issued. He has manu-factured his transducers for some years. He will receive hisScD from MIT in 1939 together with Prof. A.C. Ruge andJ. Hans Meier. His office and lab at MIT are next door toProf. Ruges.

    May 20The Franklin Institute awards the Longstreth Medal toAlfred V. A.V. de Forest and William E. Hoke for the inven-tion of Magnaflux (RTM). De Forest has already commercial-ized his scratch gage through Baldwin-Southwark andfounded Magnaflux. He is destined to be the catalyst for com-mercializing the bonded resistance wire gage throughBaldwin and Stresscoat through his Magnaflux Corp.

    JuneJ. Hans Meier arrives at MIT with his Dipl.-Ing. degree fromSwitzerland. He obtains his MSc under William M. Murrayand becomes Prof. Ruges assistant. He develops the bondedresistance strain gage, invented by Prof. Arthur C. Ruge,April 3, 1938, and writes the first and definitive still-pertinentdoctoral dissertation on the new bonded strain gage.

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  • JulyBaldwin-Southwark issues Bulletin 132: McCollumPetersElectrical Telemeters, 32 pages of operating principle, staticand dynamic applications, and commercial forms. It wasinvented at National Bureau of Standards (NBS), seen byFrancis G. Frank Tatnall, financed and commercialized byhim, and sold through Baldwin-Southwark for whom he trav-eled extensively. He did the same for many other mechanicalstrain gages. After his initial opposition to the bonded wiregage because of his financial ties to the older mechanicalgages, he becomes its most enthusiastic supporter andpropagandist.

    Early AugustCharles M. Kearns, Jr., a recently hired Penn State EE grad,invents the bonded carbon strain gage during HamiltonStandard Propeller Co.s vacation period. Within 4 years, in-flight propeller failures will go from dozens per year to none.The carbon gage is sold, copied, and spreads like wildfireworldwide.

    August 10Earle L. Kent and LeRoy Paslay file for a patent on an appa-ratus for generation of musical tones. In it, they describe themanufacture and use of printed circuits. They did not realizewhat they had invented, but this patent, 20 years later, willinvalidate all then-existing printed circuit patents in theUSA, especially Paul Eislers.

    September 10Edward E. Simmons, Jr., at Cal Tech suggests to Dr. GottfriedDatwyler that he bond a wire to a bar to make a load cell formeasuring forces in an impact machine. The bonded wireresistance strain gage is born but not recognized as such. Itlies dormant for 2-1/2 years until Prof. Ruges reinvention atMIT on April 3, 1938.

    September 16Dr.-Ing. Paul Eisler, a Viennese PhD in electrical engineeringwith extensive experience in lithography and printing,obtains a UK Provisional Patent for the printed circuit. Heis struck by the immensity of its potential application. Hebecomes the father of the printed circuit.

    William M. Murray earns his doctorate from MIT. He remainsthere until his retirement in 1973 and becomes the primeeducator in experimental stress analysis, especially bondedresistance strain gages, brittle coatings, and photoelasticity.He founds the Society for Experimental Stress Analysis in1943, now Society for Experimental Mechanics.

    FallGreer Ellis arrives at MIT. He has his BS in physics and endsup doing his masters thesis in A.V. de Forests lab where heperfects a nondestructive brittle coating, which he callsStresscoat (RTM). His thesis is completed in 1938. Stresscoatis commercialized through A.V.s Magnaflux Corp. and by1940 is a success. He founds Ellis Associates, an instrumentcompany, now part of Measurements Group, Inc.

    Frank F. Hines transfers to MIT from West Virginia Univer-sity. The courses he needs in spring 1938 are not offered; hetakes a temporary job in Prof. Ruges lab, helps develop thestrain gage, which Ruge invents, and spends his life withbonded resistance transducers. He was last chairman of theboard of RdF Corp., Hudson, NH.

    In 1936, Arthur C. Ruge is a research associate in engineeringseismology at MIT. He will invent the bonded resistancestrain gage as a deliberate solution to a strain measurementproblem, April 3, 1938. Hans Meier and Frank Hines will helphim perfect the invention, and with A.V. de Forest to commer-cialize it by mid-1939.

    By fall 1936, this team is assembled at MIT.

    CommentsNote that both the first printed circuit (out of which grew thebonded foil gage) and the first bonded wire gages were unwit-tingly invented. Kent and Paslay did not appreciate the sig-nificance of their invention. Simmons thought his was toosimple to even document, and no one on the Cal Tech ImpactProject (see later) realized the significance of the invention.

    Not until later, commercialization by Eisler and Ruge was thesignificance appreciated!

    INTRODUCTION

    As the summary and outline shows, 1936 was a turning pointin the history of experimental stress analysis and straingages. The events were listed approximately chronologicallyin the outline. The body of this paper, however, will divide theevents by subject:

    d Carbon strain gagess Unbondedj The McCollum Peters telemeterj Bonded

    s LiquidAquadagj Solidthe Kearns gage

    d Metallic strain gagess Unbonded wire gagesj The Carlson gage

    s Bonded wire gagesj Simmons at Cal Techj Ruge at MIT

    s Printed circuitsFoil gage precursorj Kent and Pasley in the USAj Eisler in the UK

    d Stresscoat brittle coatings Greer Ellis

    All these methods either originated in 1936 or achieved a crit-ical mass that assured success or reinforced it.

    CARBON STRAIN GAGES

    The Unbonded Carbon GageIn July 1936, the Southwark Division of Baldwin-SouthwarkCorp. in Philadelphia, published Bulletin No. 132,McCollumPeters Electrical Telemeters. This 32-pagebooklet contained a description of the device and a large num-ber of practical field applications along with a catalog of the

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  • available hardware and prices. The bibliography includedsome 25 references to the telemeters use on aircraft in flight,concrete structures, oil well tests, railroad tests, rolling millpressure, transmission towers, automotive applications, ele-vator cable, and general usage and description. The partiallist of telemeter users included 110 organizations in the USAand over a dozen in eight other countries. Even though thebasic strain gage version was fairly large (3/40 3 1-7/80 3 8-1/20) and heavy (1 pound), it is obvious that the deviceinvented by Burton McCollum and Orville S. Peters, electricalengineers at the NBS, had arrived.

    BurtonMcCollum had been hired by NBS in the early 1910sto help solve a problem of electrolytic corrosion of water andgas mains due to current straying from trolley tracks. He thenbecame engaged in investigations of sound-ranging andsound-detecting equipment for locating distant or concealedenemy guns during World War I. He also worked on geo-phones and seismographs to detect enemy mining operationsin the trenches and special microphones for underwatersounds until well after the armistice. The work was done inthe electrolysis section.

    McCollum left the bureau in 1926 to work in the oil-prospecting industry.

    Orville S. Peters was born in November 1883 and joinedNBS in 1910, working his way up from assistant physicist toelectrical engineer by 1929. In 1930, he became consultingengineer. At the bureau, he worked on electrolysis in concrete,together with McCollum. In 1923, he coauthored a paper,which seems to be the first publication on the carbon-basedtelemeter, with R.S. Johnston: New Developments in Elec-tric Telemeters (Proceedings of ASTM, Vol. 23, Part II, 1923,pp. 592601). This paper already showed operational hard-ware and practical applications such as field tests on bridges,dynamometers, pressure gages, and stresses in airplane staycables during flight.

    The traditionally cited paper by McCollum and Peters, ANew Electrical Telemeter, appeared in Technologic Papersof the Bureau of Standards, No. 247, January 4, 1924, partof Vol. 17.

    It describes a carbon pile displacement transducer with twodifferentially coupled elements shown in the illustration as Dand D2. Each element consists of from 20 to 55 carbon rings,carefully lapped, under an initial pressure of some 180 psi,produced by preloading the frame, A. When the tongue, B,held by a frictionless fulcrum, C, was moved up or down, itwould increase the compression in one element and decreaseit in the other. Since the elements were in adjacent arms ofa Wheatstone bridge (i.e., differentially coupled), the nonlin-earity of response in each element was canceled by that in theother.

    The movement of the tongue could be produced by force, pres-sure, torque, acceleration, etc., and the basic frame could beadapted to serve in a wide variety of transducers.

    In about 1930, Peters set up his own instrument company. It isknown that Frank Tatnall was instrumental in this transition.

    Francis G. Frank Tatnall was then working for the Bald-win-Southwark Corp., selling testing machines and associ-ated equipment. He traveled widely and knew everyonethere was to know in the testing business and what they weredoing. In his charming and sometimes imaginative autobiog-raphy, Tatnall on Testing (American Society for Metals,1966), he relates his discovery of numerous strain gagesin use by imaginative inventors in various laboratorieshe visited. It is believed that Frank often helped these inven-tors set up their own businesses, had a financial interestin those, and then arranged to sell the devices throughBaldwin-Southwark.

    Baldwins Bulletin 132 does carry the footnote, Exclusiverights granted under contract with Emery-Tatnall Company,and Frank also relates his meeting with H.L. Whittemore,chief of the mechanics section in NBS, whose invention wasalso treated in that manner and sold by Baldwin as the Whit-temore strain gage for many years.

    Roy Carlson remembered using one of these McCollumPeters carbon gage transducers embedded in the StevensonCreek Dam for measurement of forces, displacements, andpressures, and being frustrated by the instabilities and tem-perature sensitivity of the carbon elements. They were,indeed, better suited for dynamic studies. It was this experi-ence with carbon gages that drove Carlson to develop his owntransducer based on unbonded wires, to be discussed in a sub-sequent section.

    In 1936, however, the McCollumPeters telemeter was at theheight of its popularity, although, also in 1936, Carlsons pat-ent for his unbonded wire transducer was granted.

    Frank Tatnall recalls that when he first heard of the teleme-ter and went to NBS, McCollum had already left, which he didin 1926. By May 19, 1927, Frank had already written anUnofficial Observers Report on Telemeter Tests on FreightCar Truck Side Frames by American Steel Foundries, pub-lished in mimeographed form by Baldwin-Southwark. Thiswould appear to date the arrival of the telemeter on the com-mercial scene, to 1927.

    The BondedPainted Carbon Resistance GageAmong the early attempts to paint a liquid, carbon-based sub-stance to surfaces for strain measurement was Alfred Blochspublication in Nature magazine, August 10, 1935. A. Bloch,New Methods for Measuring Mechanical Stresses at HigherFrequencies,Nature, Vol. 156, No. 3432, August 10, 1935, pp.223224, discusses carbon pile and piezoelectric transducersas well as a painted carbon film. Bloch was with the PhysicsDepartment at Trinity College, Dublin, when he publishedthis paper. He mentioned plans to publish details in a futureissue but never did.

    Born in Weiden/Oberpfalz, Germany, Alfred Bloch (August 1,19041979) moved to Munich in October 1923 and earned hisdoctorate at the University of Munich, July 22, 1932. Hisdissertation translated roughly as, On the Mechanics ofBrake-Shoe Impact and Related Events on Railway Opera-tion. In this dissertation, he used an unbonded carbon straingage transducer developed by Dr.-Ing. Rudolf Bernhard,

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  • which looks a lot like a copy of the McCollumPeters teleme-ter that arrived in Germany in 1925. In fact, Dr. Bernhardvisited the NBS in Washington, DC, and the laboratory ofMcCollum and Peters in 1926. This gave him the impetus todesign units with improved frequency response with twin res-onances of 1335 and 2000 Hz, versus the American unit (ashe put it) that had a 500-Hz resonance when mounted and 250Hz unmounted.

    It was E.H. Hulls application of Aquadag at General ElectricCo. in 1936, however, that, at the time, came close to a small,weightless, bondable strain gage. (E.H. Hull, AlternatingStress Measurement by the Resistance Strip Method, Gen-eral Electric Review, August 1937, pp. 379380, presentsEdwin Hulls Aquadag (RTM)based painted carbon strip.In 1935, he had experimented with the method by paintinga small strip of paper with India ink. This gage he used suc-cessfully in measuring strain concentrations in fillets onsteam turbine shafts, as reported in Claude M. Hathaway,Electrical Instruments for Strain Analysis, Proceedings,Society for Experimental Stress Analysis, Vol. I, No. 1, 1943,pp. 8393.) It was no panacea, however. A.V. de Forestdescribes Aquadag in his paper Measurement of PropellerStresses in Flight, Journal of Aeronautical Sciences, Vol. 4,No. 6, April 1937, in which he is listed as affiliated withHamilton Standard Propellers Division United Aircraft Corp.,a fact of interest in the next section.

    In its first form, this pickup consists of an insulating layerof paper cemented to the metal surface, and carrying lead-incontacts of tin foil cemented to the upper surface of theinsulating paper. The paint, applied between the two metalcontact strips, was made of very finely divided graphiteeither in water or in alcohol suspension. The steady resis-tance of the strip varies in an irregular manner at zero loaddue to temperature, moisture, and perhaps other disturban-ces. To avoid this difficulty, the strip was connected so thatonly changes in resistance with strain were measured. If thestress variation is above 30 cycles per min, the amplifieronly records the cyclic fluctuations and is not sensitive toslow changes in resistance.

    Calibration of such strips at the General Electric Co., atHamilton Standard Propeller, and at MIT showed that themeasurement of strain was almost independent of frequencyand closely proportional to strain amplitude. The resistancecould be made quite high, 1000 to 50,000 ohms, and a consider-able voltage applied to the system. In this way, slip ring dif-ficulties were largely avoided. The weight of the pickup wasinfinitesimal and the measurement could be carried out any-where on the (propeller) blades regardless of the centrifugalloading.

    The major difficulties were the necessity for calibration ofeach paint strip under vibratory stresses, and the change insensitivity due to temperature and moisture. The device is, ineffect, an extreme refinement of the carbon pile telemeter asoriginally developed by Peters of the Bureau of Standards andmarketed by Baldwin-Southwark Co. for the last 10 years.

    FrankTatnall recalls that it was impossible to reproduce thethickness, gage length, and resistance. Charles M. Kearns,Jr., inventor of the bonded (solid) carbon strain gage (see next

    section) recalls that powdered sulfur would be mixed with thesolution, and the gage, once painted on, would be heated tomelt the sulfur and solidify the installation. He also preparedsuch strain gages on paper strips. Therefore, his memory ofAquadag is associated with the vile smell of heated sulfur.

    The (Solid) Bonded Carbon Resistance GageAs related by Charles M. Kearns, Jr., I had the goodfortune, after graduating in June 1936 from Penn State,to join Hamilton Standard, then a division of United Air-craft Corporation. I was assigned to the problem of doingsomething about propeller blade fatigue stress failures (inflight). After a couple of months of working with a terriblemixture of sulfur and graphite (Aquadag) which did indeedchange its resistance with stress, but also with just abouteverything else, I was left alone during the vacation periodof the company (the first two weeks of August). (Authorsnote: as a new hire he was not eligible for vacation). Havingbeen a ham radio nut, in fact I still amI got to thinking:a microphone provides a resistance change when carbongranules are compressed. What we need is a more ruggedsubstance than a carbon granule button, and, having usedcarbon resistors, I simply ground one down, cemented it toa beam, and sure enough, it changed resistance with strainmore or less linearly. The calibrations were on a baragainst a Huggenberger tensometer. With this type of gagewe made hundreds of thousands of propeller stress meas-urements and succeeded in reducing the incidence of pro-peller failures from a major problem to, in some years, zeroproblem; and I think we saved a lot of lives. I was mainlyinterested in solving the problem of safety in flight. Thestrain gage was an important means to that end but notthe end itself . we viewed ourselves as having responsibil-ity to the whole aviation community to spread the word ofwhat we were doing. I published a paper in 1937 in theJournal of Applied Mechanics, Vibration Stress Measure-ments in Strong Centrifugal Fields (December, p. 15659,with Ralph Guerke).

    Between the years 1931 to 1938, propeller failures in flightran anywhere from 8 to 41 times a year. By 1938 we hadbegun to study all the installations in the field and restrictingthem so that they did not operate under conditions of severevibrations. In 1939 there were 6 failures and in 1940 therewere none. I am proud of that, because it has led to improvedsafety in flight.

    The Kearns gage was widely copied but also made for saleby Hamilton Standard who sold many thousands all overthe world. It was replaced in 1938 by a more flexible carbongage, which obsoleted not only his first invention but alsothe ESS strip developed by A.V. de Forest and Wilfrid L.Bill Walsh at MIT in 1937. In fact, the Kearns carbon gageand its copies were used at least through 1944 and probablylater.

    Kearns retired in 1975 as staff vice president of UnitedTechnologies, the parent company of Hamilton Standard,Pratt & Whitney, and others. He now lives in Tucson, AZ.He was awarded many honors, including the LongstrethMedal of the Franklin Institute in 1942.

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  • It is interesting to note that bonded carbon film gages are stillused today in shock pressure measurements at very highpressures, as developed by Dr. Jacques Charest, Dynasen,Inc., 20 Arnold Place, Goleta, CA 93017.

    WIRE STRAIN GAGES

    Unbonded Wire Strain GagesUS Patent No. 2,036,458 on a telemetric device was granted toRoy W. Carlson on April 7, 1936. He had applied for itAugust 4, 1934. The attorney preparing the patent was Royscousin, Chester F. Carlson, the inventor of the xerographiccopying method and founder of Xerox.

    Roy achieved international fame, acclaim, and honors in thefield of dams and large concrete structures, especially in theirinstrumentation. He got his BA in mathematics from Univer-sity of Redlands, worked for Southern California Edison fora year, attended California Institute of Technology for a year(19231924), but left without a degree. After teaching a yearat University of Redlands, he returned to Southern CaliforniaEdison and worked on the Experimental Arch Dam onStevenson Creek in 1925 where he began his work on damsand concrete technology. Every type of instrument known atthe time for measuring structural action was used to test thatdam, he wrote for a February 3, 1978, lecture in Sao Paulo,Brazil, including strain meters of a carbon resistance type.These strain meters (the McCollum-Peters Telemeter) werefairly good for quick changes in dimension, but were worthlessfor long-time measurements.. The Stevenson Creek Exper-imental Dam was probably the most researched dam in theworld . built. solely for the purpose of testing theories forarch dams. All told, Carlson helped determine the safety of37 dams for Southern California Edison. He was then a testingengineer on some 10 dams for County of Los Angeles, 19271931, and the assistant director of research on materials forHoover Dam until 1934. During this time, he earned his MSEat University of California at Berkeley in 1933 and taughtthere as an associate professor in 1935, when he went toMIT for his doctorate.

    In the early 1930s, culminating in his 1936 patent, hedesigned his own instruments for dam investigations, basedon unbonded wires, pretensioned in a frame that differen-tially coupled the responses of two loops of wires. Very muchas in the McCollumPeters precompressed carbon stack, themovement of Carlsons frame increased the tension in onewinding as it reduced the tension in the other, giving a linear,temperature-compensated output. He found that carbon steel,when drawn small enough (about 0.010 diameter), approaches700,000-psi tensile strength with a gage factor of 3.6. Twothousand of his strain meters were used in the Glen CanyonDam; 1600 in Flaming Gorge Dam. They are still manufac-tured by Carlson Instrument Co. and (in copy form) by KyowaElectronic Instruments.

    In 1935, he went to MIT where he earned his doctorate in 1939on Development and Analysis of a Device for MeasuringCompressive Stress in Concrete. At the same time as hereceived his doctorate, so did Arthur C. Ruge and HansMeier. Frank Hines received his bachelors degree by mailthat yearhe was too busy making the SR-4 bonded wire

    strain gages, which Prof. Ruge had invented April 3, 1938,and which Hans Meier had developed as his doctoral disser-tation. These individuals appear in this story a little later. Butit is interesting to note that Carlson and Ruge had side-by-side offices and labs in the basement of Building I, Civil Engi-neering Department, at MIT.

    Roy Carlson, September 20, 1900 November 20, 1990,accumulated numerous honors and awards including theSouthern Cross of Brazil, recognizing his years of involvementwith construction and testing of concrete dams in that coun-try. He is noted for three major inventions used in under-standing the behavior of concrete: the stress meter, strainmeter, and conduction calorimeter. He had envisioned theunbonded wire strain gage as only for applications to concrete.Louis Statham built many other transducers on that princi-ple: force, displacement, acceleration, pressure, fluid flow, etc.He infringed on Carlsons patent until he was finally forced tobuy it, paying Carlson a 3% royalty on all Statham trans-ducers while collecting 50 cents per transducer that Carlsonsold. In some forms, the unbonded wire strain gage is stillavailable today.

    Bonded Resistance Wire Strain GagesIt was during the first 2 weeks of September 1936 thatEdward E. Simmons, Jr., an inventive MS EE graduatefrom California Institute of Technology (also 1936), was con-sulted by Dr. Gottfried Datwyler about a better way ofmeasuring the dynamic forces produced by an impact-testingmachine at Cal Tech.

    Datwyler had received his Dipl.-Ing. degree from the Fed-eral Technical Institute (ETH) in Switzerland in 1929 and,to please his mother, continued for a doctorate, which hereceived in aerodynamics from ETH March 19, 1934. Thissame year he appeared at Cal Tech as a research associ-ate in aeronautical engineering under Prof. Theodore vanKarman (18811963) who had under his wing in theGuggenheim Aeronautical Building all sorts of orphanprojects that could not find a home in other departments.One of these was the Impact Research Project headed byDr. Donald S. Clark, Cal Tech (BS 1929, MS 1930, PhD1934).

    Exactly how Datwyler came to work on that project withClark we now know. Simmons had been involved for sometime as a consultant to many of the projects in the buildingbecause of his inventiveness especially of measuring appara-tus and instrumentation. Datwyler had tried Aquadag andother electrical strain gages of the day, but nothing workedunder the high-speed transient conditions of impact.

    From Dr. Gottfried Datwylers Deposition of February 9,1958, in the landmark lawsuit, Baldwin-Lima-Hamilton Cor-poration and Edward E. Simmons, Jr., v. Tatnall MeasuringSystems Co., and the Budd Company, US District Court,E.D. Pennsylvania, Dec. 1, 1958, Civil A. No. 23505, someinteresting facts emerge that fill holes in the story as previ-ously available.

    After receiving his doctorate in Switzerland in 1934, he spentabout 6 months in the family plant in Altdorf, Switzerland.

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  • The plant produced electric wires and technical rubber goodsamong other products. They were having some problems withthe wire drawing process.

    In September 1934, he landed in the USA and drove across thecountry to Cal Tech. Prof. von Karman had assured hima research fellow position in aerodynamics, his major field.At Cal Tech, however, he found that the wind tunnel wasbusy with confidential work, and as an alien I couldnt getinto the tunnel. After I got tired of just pencil pushing, I gotin contact with Professor Clark, Professor in Metallurgy andTesting Materials. We got to talk about various problems ofmetals, mostly in connection with the copper wire drawingproblem which they had in Altdorf, and then I got more intothe field of testing materials.

    Datwyler described the start of the Impact Project at Cal Techand the meeting at which some $10,000 were raised by a groupof sponsors listed below.

    Work started on June 20, 1936. By July 29, he was work-ing with Aquadag, all the way through September 8. He wasaware of Carlsons unbonded wire strain gage and of Kearnswork at Hamilton Standard Propeller of just a few weeksbefore, through private correspondence with the Hamiltongroup, but apparently did not use the Kearns gage.

    September 10, 1936, was the date when Ed Simmons sug-gested thatDatwyler try using a bonded wire. Simmons evenwent to the physics stock room and got a spool of No. 40-gage,cotton-wrapped, insulated Advance, constantan wire for

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  • Datwyler to try. Datwyler bonded it to a piece of clock springwith Glyptal cement and tested it cantilever beam style, Sep-tember 10, 1936. I had just a straight piece of wire, varnishedonto a spring steel strip. By bending the steel strip into aU-shape, resistance increased by 0.25 ohm. The initial resis-tance was 17 ohms .. No shifting of zero after several tests;wire finally broke. The 1.4% resistance change would be 7000microstrain!

    It was linear, repeatable, and hysteresis free. The bonded wirestrain gage had been born, and its immediate derivative, thestrain-gage-based loads cell. Later he used No. 40-gage var-nish-insulated wire, bonding the fine wire to the surface ofa prismatic bar and to use that as a load cell on the impact test.

    The Aquadag-based strain gage had shown incurable zeroshifts, drifts, and hysteresis effects that made it useless forhis purposes.

    Impact Research Report #1-Confidential was signed by Dat-wyler, Prof. Don Clarke, and Prof. von Karman. It wasreleased to no one outside the Impact Project except itssponsors.

    It is interesting to note that no one realized that a significantinvention had been made. Simmons the electrical engineer,Datwyler the aerodynamicist, and Clark the metallurgistwere apparently unfamiliar with the intense search by stressanalysts for just what Simmons had conceived. Simmonsrecalled his thought at the time: Patent such a ridiculouslysimple thing???

    It was an invention, which solved a problem, as we shall seeagain for the printed circuit. It was not an aim in itself.Although the sponsors of the Impact Project read like a whoswho in American industry at the time, it also did not occur tothe recipients of the periodic progress reports to note anything

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  • significant about the way in which the dynamic impact forceswere measured. Even when Clark and Datwyler presentedtheir paper at the ASTM Meeting, June 1938, in Atlantic City(Stress-Strain Relationships under Tension Impact Load-ing, by Dr. Donald S. Clark and Dr. Gottfried Datwyler,assistant professor of mechanical engineering and researchfellow in aeronautics, respectively, California Institute ofTechnology, Pasadena, CA. Symposium on Impact Testing,ASTM June 1938. Proceedings printed in January 1939, copy-right 1939. Proceedings of the 1938 Annual Meeting), none ofthe discussants whose comments were published noted any-thing significant about the measurement systemnot evenDr. Louis B. Tuckerman of the NBS and the inventor of theTuckerman optical strain gage, and who was in the audience,commented about the load cell. It is interesting that the very

    first successful application of bonded resistance wire straingages was on a problem still considered challenging: high-speed transient force measurement during impact. Electricalengineer (with a masters degree) Ed Simmons developedcircuitry, using triggering and single-current-pulsed techni-ques that are still used, on that first application in 1936!

    The sponsors of the Impact Project at Cal Tech were AllisChalmers Manufacturing Co., Caterpillar Tractor Co., Gen-eral Petroleum Corp. of America, Hughes Tool Co., Lane-Wells Co., National Supply Co., Arnold Pfau, A.O. SmithCorp., Union Oil of California, and W.M. Whiteall of whomhad also given permission to publish the results of thoseinvestigations and none of whom realized the significance ofthe invention.

    Top Left: A Carlson Unbonded Wire Transducer. About 25cm,10 inches long. Force applied at left end increases the tension inone pair of pretensioned wires, and decreases the tension in theother pair. Top Right: Examples of the Kearns Bonded CarbonGage. The plaque was presented to Kearns when he left thegroup. Bottom Gage: Serial No 22103, original design; Top:Serial #M1174, more flexible design. Bottom Left: Huggen-berger Extensometer with 1200 magnification. Invented byA. U. Huggenberger in Switzerland, it was sold by Baldwin-Southwark in the US; one of the most popular strain gages of1936. Bottom Right: One of the first SR-4 MetalectricBonded Wire Resistance Strain Gages of the SR-4 type inventedby A. C. Ruge and sold through Baldwin-Southwark starting in1939-40. The team which perfected and commercialized it wasin place at MIT in 1936.

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    January/February 2006 EXPERIMENTAL TECHNIQUES 31

  • The volume of ASTM Proceedings containing the paper wasnot published until January 1939 and not until after Prof.Arthur C. Ruge, at MIT, had requested a patent release fromMIT on February 20, 1939, for his (re)invention of the bondedwire gage, did the MIT team find out about Simmons work!When the team of Prof. Ruge, Hans Meier, and FrankHines at MIT heard about the Clark and Datwyler paper(cited above) some time after February 20, 1939, great disil-lusionment and despondency descended on them. They werereadying their version of the bonded wire resistance straingage for commercialization. Hans Meier remembers, I justhad time to include the reference in my doctoral dissertation!

    It was A.V. de Forest who had gone through the samesituation in 1929 with the Magnaflux patents (see later sec-tion), who saved the day. He told Ruge that Simmons mightget the basic patent but that he, Ruge, would have anyimprovement patents, that the promise of commercializationand financial return was great, and that he should go ahead.

    It was also A.V., with his existing ties with Baldwin-South-wark through his scratch gage, who brought Ruge togetherwith Baldwin, who, in turn, approached Simmons to join theenterprise. As with Magnaflux, the two almost-concurrentinventors joined forces instead of fighting patent battles.

    Without A.V.s experience and business acumen, the historyof experimental stress analysis would have developed alongquite different lines.

    Datwyler returned to the ETH in Switzerland September25, 1938, and developed a line of hot-wire anemometersand associated instrumentation that he made and soldthrough his company, Polymetron, for many years. He alsodesigned, produced, and sold large- and medium-sized windtunnels throughout Europe and cross-flow compressors/fansas DatwylerHausamannDiesler in the early 1950s. Hegrazed the field of strain gages only once, briefly, likea comet.

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    32 EXPERIMENTAL TECHNIQUES January/February 2006

  • In 1936, Arthur C. Ruge, whom everyone called Prof asthough it was his first name, was a research associate inengineering seismology at MIT. J. Hans Meier appearsat MIT with his Dipl.-Ing. degree from Switzerland, getshis masters degree under William M. Murray in 1937and becomes Prof s assistant. Also in 1936, Frank Hinestransfers to MIT from West Virginia University. He hadwon the 1931 Fisher Body (General Motors) competitionfor a handmade exact model replica of Napoleons WeddingCoach. The prize for that National Competition was a$5,000 (1931 dollars!) scholarship, which enabled him toattend college.

    As happens with many transfer students, the courses heneeded in spring 1938 were not offered and he took a semesteroff to work for the MIT Hobby Shop. By luck and chance,he got a job in Prof. Ruges lab to maintain the notoriouslyfailure-prone earthquake-simulating machine. The team towhich we owe the commercialized bonded wire strain gage,as we know it today, has now been assembled!

    Prof. Ruge received a research contract from an insurancecompany to study the behavior of water towers under earth-quake conditions since the major damage in earthquakesis from fires rather than the quake itself. Hans Meier, his

    assistant, is to predict and measure the stresses in the double-curved, thin-shell vibrating structure. They try every strainmeasurement method known to them, but none will do the job.Finally, in desperation, professor has a eureka experienceearly Sunday morning, April 3, 1938. He unwinds the wirefrom a precision resistor, bonds it down on a test beam, and itworks! Hans Meier develops the gage on his doctoral disser-tation that changes from an emphasis on the water tower toan emphasis on the strain gage. Frank Hines with hisunusual manual dexterity and devotion to detail, which wonhim the Fisher Body prize, is an invaluable member of theteam and spends the rest of his life on bonded resistancetransducersfirst strain gages and then temperature sen-sors. He was the last chairman of the board, RdF Corp.,the last remaining vestige of Ruge-de-Forest ConsultingEngineers.

    Ruge and Meier, not having a galvanometer to read the out-put of their Wheatstone bridge, conduct their first experi-ments in A.V. de Forests Lab in Mechanical Engineering onthe third floor of Building I. When they see how well it works,they each recognize exactly what has been discovered andspend the rest of their lives developing (Ruge, de Forest,and Hines), making and using (Meier) the gages, and trans-ducers based on them.

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    January/February 2006 EXPERIMENTAL TECHNIQUES 33

  • Alfred V. A.V. De ForestA.V. deserves a separate section in any history of experi-mental mechanics. In 1936, he and William E. Hoke receivethe prestigious Longstreth Medal from the Franklin Insti-tute For the Detection of Hidden Defects in Magnetic andCurrent-Carrying Materials, commercially exploited asMagnaflux Corp., which de Forest founded in 1934. In1928, he noted that small iron particles tend to collect oncracks in magnetized steel parts. He found that by passingheavy currents through the material under investigation,the sensitivity of the test could be greatly increased, andhis development of circular polarization completed this verypowerful nondestructive testing tool. He found that his orig-inal patent application has been preempted by MajorWilliam Hoke, who in 1918 (!) also noted small iron particlescollecting around cracks but never used the process com-mercially. De Forest overcame his disappointment and real-ized that although Hoke may have the basic patent, he, deForest, would have the improvement patents, so they joinedforces and de Forest soon bought out Hokes interest. By1936, Magnaflux had arrived. (Note the parallel with inven-tion and re-invention of the bonded resistance strain gage asnoted above.)

    De Forest had also invented the de Forest scratch gage,a small, lightweight, mechanical self-recording strain gagethat he commercialized through Baldwin-Southwark Corp.The last Catalog Bulletin that the author has on the scratchgage is dated 1947! So late into the history of strain gages wasthat simple device still made and sold!

    Scratch gages are still used today. Two surviving varietiesused in applications ranging from offshore platforms to allfirst-line aircraft in the US Air Force use their distinct advan-tages: it is diver installable and retrievable, operates unat-tended, is self-recording, requires no electrical connectionsor lead wires, is radiation resistant, and can be self-tempera-ture compensated. Two manufacturers are Prewitt Associ-ates, Scratch Gage Division, P.O. Box 365, Lexington, KY40501. Their gage is suitable for low-frequency work such asthe offshore platform application and Leigh Instruments Ltd.,Avionics Division, Box 820, Carleton Place, Ontario, CanadaKOA 170. A removable cartridge contains a roll of steel tapeon which the record is inscribed. In aircraft applications, thecartridge will record 150 flight hours of vibration experienceand can then simply be exchanged for a new one.

    The scratch gage consists of a polished target that is attachedto the test specimen, adhesively, with screws, solder, etc., anda pointer with abrasive material at the tip, which sits on thetarget. The pointer is held in place by a frictional joint, butnear its other end, it is bent in the third dimension to forma torsional spring, the restoring force of which overcomes thefrictional force in the joint under vibratory (but not static)conditions. The other end of the pointer is, in turn, alsoattached to the specimen so that a 20 gage-length strain gage(usually) resultsnonelectrical, without lead wires, self-recording (the scratches on the target), self-contained, andlightweight.

    Wilfrid L. Bill Walsh worked with A.V. as his technician/associate from the early 1920s to A.V.s untimely death in

    1945. Together they moved from American Chain Co. toMIT in 1934. It is correct to assess their partnership as fol-lows: every idea A.V. had and every invention he made wasreduced to practice and built by Bill Walsh. He made the firstMagnaflux equipment, all the scratch gages until after A.V.sdeath, and all the other devices, which A.V. needed.

    The consummate entrepreneur/inventor, A.V., commercial-ized the scratch gage through Baldwin-Southwark who soldthem by the thousands. A.V. was MIT class 1911 and the onlyfull professor on the faculty with only a BS degree. He wasvery proud of that.

    It is his ability to overcome disappointments, as with theMagnaflux patent, and to commercialize on his inventive-ness, as with the scratch gage, which are responsible forthe commercialization, in the form in which we know themtoday, of the bonded wire strain gage, the SR-4 Metalectricgage, and of Stresscoat brittle coating (through Magnaflux).He is also the author of the first publication on the bondedresistance strain gage, Letter to the Editor, Journal ofAeronautical Sciences, Vol. 7, No. 7, November 27, 1939,to preempt a copy developed in California from being thefirst published version.

    Bonded Wire Resistance Strain Gage: ContinuedThe Simmons gage, starting in the first two weeks ofSeptember 1936, was made of insulated wire, premountedon a paper carrier, and mounted paper-side up, wire-sidedown on the test specimen. The Ruge gage, starting in April1938, was made with bare wire, premounted on a paper backingor carrier. It was mounted paper-side down, wire-side up, sothat the paper provided the insulation.

    When the patent and contract negotiations started betweenSimmons and Clark at Cal Tech with Baldwin-Southwark,Simmons was happy for Cal Tech to get the royaltiesbecause he was told they would pay his salary on theImpact Project by which he was fascinated. When hisemployment and then the entire project were terminatedin 1941, he found that the royalties had gone to the gen-eral fund. He sued Cal Tech for fraud and recovered$125,000 in back royalties when the California SupremeCourt found in his favor in 1949 [Edward E. Simmons,Jr., v. Cal Tech (34 C2d 264; 209 P. 2d 581) L.A. No.19484, In Bank, Sept. 16, 1949] and about $1 million totalover the life of the patent. He lived in Pasadena, CA, wear-ing only Renaissance costume, still with an interest inengineering and science and with total and instant recallof the details of the early days. He received the LongstrethMedal of the Franklin Institute in 1944 for his invention ofthe bonded wire gage. It should be noted that he neverbonded a gage down in his life. Ive always had others todo that, he said even of the very first gage which Datwylerbonded. But because he had the idea, his were the patentand the royalties.

    It should be noted that Frank Tatnall was a long-time chair-man of the Longstreth Medal Award committee and had a lotto do with the medal award to de Forest & Hoke, Kearns, andSimmons. Prof. Ruge did not receive that medal.

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    34 EXPERIMENTAL TECHNIQUES January/February 2006

  • Slightly over two inches long, weighing less than two grams, and self-contained, the deForestScratch Gage has many applications in measuring strain in fast moving machine parts.

    Scratch Gages attached to rail. Use of half-targets facilitates obtainingmany records without removing gage.

    Open scale record of vibration in propeller. Magnification: 500x.

    deForest Scratch Gages mounted on airplane propeller blade for analysisof different modes of vibration.

    High frequency vibration, 3,100 lb. per square inch, superimposed onrepetitions of principal stress of 39,600 lb. per square inch.

    Close packed record from airplane propeller. Density of record may bevaried within wide limits. Magnification: 500x.

    Combined torsional and longitudinal stress in angle iron vibrating as acantilever beam. Magnification: 300x.

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    January/February 2006 EXPERIMENTAL TECHNIQUES 35

  • Printed Circuits: Precursors of the Foil GageThe bonded resistance strain gage of choice today is the foilstrain gage manufactured primarily by printed circuit etchingmethods. The die-cut strain gage had a brief period of successbut is not commercial today.

    August 10, 1936, Earle L. Kent and LeRoy Paslay filed fora patent on an apparatus for the generation of musical tones,issued as #2,147,948 February 21, 1939. It was an electronicorgan! In its construction and in the patent, they describe incomplete detail the still-pertinent manufacture of a printedcircuit.

    Since their aim was an electronic organ, they paid no atten-tion to the printed circuit technique by which they made itand, as in the case of Simmons and Cal Tech, did not recognizethe significance of their invention.

    September 16, 1936, Dr.-Ing. Paul Eisler received his Pro-visional Patent Application #24,543 in London, England, forproduction of electrical apparatus and components for weakcurrent purposes. As a doctor of electrical engineering withpractical experience in the printing and lithography indus-tries in his birthplace, Vienna, Austria, he had his eurekaexperience while walking with friends in Regents Park,London, and was struck by the immensity of its potentialapplications! He knew what he had invented and went onto become the father of printed circuits all over the world,except, ironically, not in the USA where the Kent and Paslaypatent invalidated the Eisler patents in a bitterly foughtseries of lawsuits of which Technograph Printed CircuitsLtd. v. Admiral Corp., Civil Action 62C671 in US DistrictCourt for the Northern District of Illinois Eastern Division,1964, and Technograph Printed Circuits v. Bendix AviationCorp. Civ. A. No. 11421, US District Court D. Maryland, May27, 1963; appealed U.S. Court of Appeals, Fourth Circuit#9085, decided January 17, 1964, for the defendant, are primeexamples.

    Earle Kent was born in 1910 in Adrian, TX. He was a pro-fessional musician playing clarinet and saxophone in concertbands from 19271935. He also developed an early interest inelectronics and helped build and operate one of the first reg-ularly scheduled experimental TV broadcasting stations inthe nation: W9XAK at Kansas State University, where hemet LeRoy Paslay who directed the project.

    While at Kansas State, he invented an electronic organ (men-tioned above), which incorporated the modem printed circuitin its manufacture, working with Paslay from 19331936. In1935, he received his BS EE and in 1936 his MS EE. From19361940, he was an instructor in EE at Armour (now Illi-nois) Institute of Technology in Chicago. He earned his PhDfrom University of Michigan in 1952.

    In 1940, he had joined C.G. Conn, manufacturer of musicalinstruments, and set up their electronic organ engineeringdepartment. During World War II, he directed researchon defense products for government agencies. He had over2-dozen patents to his credit. In his 29-year-long career withC.G. Conn, Ltd., he distinguished himself in the design ofboth electronic and acoustical instruments. We used strain

    gages in wind instruments and piano research!he wrotein October 1990. He won several awards and honors. Heretired in 1971 after 29 years as director of research, devel-opment, and design. He had his own consulting firm andeven at 80 was doing computer programming for the CountyCourt System in Elkhart, IN, where he and Nina live. Hiscivic activities, awards, publications, and presentations fillpages.

    LeRoy C. Paslay was born in Manhattan, KS, in 1907. Heacquired his BS EE at Kansas State in 1930, joined GeneralElectric Co. for 2 years, and returned for his MS EE, which hereceived in 1934. He remained as an assistant professor until1934, also as director of research.

    It is of that period that he wrote on November 2, 1990, Iwas mostly engaged in television research when Earle Kentapproached me for help in development of an electronicorgan he had been working on. The idea seemed greatand I agreed to go into it with him . we decided thata means of scanning exact wave forms of organ soundswas indicated (as obtained on oscillograms and translatedto polar coordinates). The system . required a lot of care-fully laid out (electrically) conducting forms on an insulateddisc. My father was a commercial photographer with somephotoengraving experience and with a fully equipped shopin the same town, so with that knowledge and expertiseavailable, it seemed logical to produce these forms and theconnecting circuits with printed circuits, and it worked likea charm.

    We made several models, got a patent, and tried to find a wayto raise money and get into the organ business but withoutsuccess.

    I joined the National Geophysical Company of Dallas, Texas,as Director of Research and Development of electronic instru-ments for use in seismic exploration for oil and gas structures.That put the organ pretty much on hold.

    During World War II I became head of the Underwater SoundDivision of Naval Ordnance Laboratory in Washington, DC,where my division developed crystal pressure transducers forvarious mine applications. With this, then new, practicalapplication using various crystal materials, I was able todevelop, after the war, and patent, an entirely new methodof oil exploration in water-covered areas that has since beenthe means of finding almost all the underwater structurescontaining oil, in the world. His device is known today asthe Paslay Streamer. He received many awards and honorsand held numerous high positions with various organizations.He maintained his office in Dallas, Texas, and remained pro-fessionally active, living in Manalapan, Florida, until hispassing in May 2001.

    Dr.-Ing. Paul Eisler earned his doctorate in electrical engi-neering at the University of Vienna in 1933 and, as a Jew,could not find employment in the already-Nazi-contaminatedAustria. He did acquire a marvelous background in printingtechnology and lithography and in making the music playedon electrified trains free of noise and static, a major problem inthose days.

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    36 EXPERIMENTAL TECHNIQUES January/February 2006

  • May 15, 1936, he left Vienna for London. As an alien, how-ever, I was not permitted to work, he wrote in his biographyMy Life with Printed Circuits, Lehigh University Press/Asso-ciated University Presses, 1989. It was in the warm sunnydays of early autumn 1936, he wrote on December 18, 1990, Ihad met a friend . we were taking a walk in Regents Park.Suddenly out of the blue sky, without any conscious associa-tion I got the idea of Printed Circuits and was struck by theimmensity of its potential applications. I got in touch with mypatent agent . my application for a Provisional Patent gotthe number 24543. (Production of electrical apparatus andcomponents for weak current purposes.)

    When he offered his printed circuit invention to industry, itwas rejected. Eventually, after much hardship, he succeededin interesting H.V. Strong, proprietor of an old establishedfirm of music printers, but he was required to sign an agree-ment that conferred title of all related future patents toStrong.

    Eisler then constructed the first radio set incorporatingprinted circuits (see illustration). He demonstrated the setto the Allied Missions and received a highly favorableresponse. The Americans used the printed circuits in prox-imity fuses, and these were supplied to the antiaircraft bat-teries for the defense of London and of the Antwerpbridgehead.

    Technograph Printed Circuits, Ltd., was formed and he devel-oped a unique facility for making printed circuits. These even-tually conquered the world and he got patents in manycountries including the USA. It was not until after Eisler leftTechnograph in 1956 that Technograph tried to enforce theirpatents in the USA and launched some 100 lawsuits that theKent and Paslay patent was found by Bendix lawyers. It inva-lidated all the Technograph patents.

    Paul Eisler had numerous other inventions to his credit andstill maintained a Consultancy in London, until his death in1992.

    Foil strain gages as such came much later, in the early 1950s,and do not form part of this story. In 1936, however, thegroundwork was all laid and the technology and people werein place.

    Other Strain Gages in Use in 1936Although the author is not aware that 1936 was a crucialyear for the many mechanical and inductive strain gagesused for stress analysis and in some transducer applica-tions, the one mechanical strain gage, which should bementioned, is the Huggenberger tensometer (see illustra-tion). It was perhaps the most widely used gage for manydecades. Huggenberger developed it during a competition tomeasure strains in the Russian railway system and wonthat contract.

    In 1924, Dr. Arnold U. Huggenberger in Switzerlandinvented a compound-lever mechanical strain gage. The twopopular models had magnifications of 700 and 1200. It wassold in the USA by Baldwin-Southwark already before 1930,

    and the author used them through 1955. Frank Tatnall heldthe exclusive import right to the USA.

    It had to be clamped to the test specimen by one of a variety ofwaysmechanical, magnetic, electromagneticand was suit-able only for static measurements. A line of sight was requiredto read the position of the pointer against a scale.

    Dr. Huggenberger (18951981) was a world-renowned expertin instrumentation of dams and large concrete structures. Hiscompany also manufactured bonded resistance wire straingages based on the method of Dr. Gotthard Gustafson(November 14, 1902 March 5, 1975) that circumvented theSimmons patent. He also copied Roy Carlsons unbondedwire strain gage transducers and sold them along with a line ofelectrical/electronic strain indicators and signal-conditioning/readout instrumentation.

    Dr. Gustafsson was with the Aeronautical Research Instituteof Sweden, and the gage was known as the G-H Tepic, forGustafsson-Huggenberger Tensio Pickup.

    BRITTLE COATINGS

    Strain gages have always presupposed knowledge of where tomount them in stress analysis applications. The locations anddirections of the highest strains on a structure are usuallyunknown, but unless the strain gage is placed there, eventhe best strain gage and instrumentation system are power-less to predict failure, in general.

    It is fortuitous that in the same year and at the same institu-tion, and even in the same laboratory in which the bondedresistance strain gage, as we know it today, was developed,the first commercially successful brittle coating was devel-oped as the result of a masters thesis.

    In 1936, Greer Ellis had arrived at MIT with his BS in phys-ics and practical experience at the NBS. He received his mas-ters degree in aeronautics in June 1938 and for his thesis hadworked in A.V. de Forests lab developing a brittle coatingthat could be sprayed onto parts, and which would crackbefore the parts themselves were overstrained. He calledthe coating Stresscoat (RTM). It was commercialized by A.V.de Forest through his Magnaflux Corp. and by 1940 hadbecome a successful adjunct to strain gage work and oftensufficient in itself to solve important stress analysis problems.After some years propagating his invention, and doing con-sulting work, Greer started his own company, Ellis Associ-ates, designing and manufacturing electronic instruments,primarily signal-conditioning and readout instruments forstrain gage and transducer work. His designs still survive,and the BAM-1 (Bridge, Amplifier, and Meter) was still madesubstantially as he designed it in the early 1950s, until about1980, a true tribute to a great designer.

    Vishay Intertechnology bought his company in the 1970s, andit is today part of Measurements Group, Inc. Ellis lived inMattapoisett, MA, where he celebrated his 80th birthday in1990. He died in 1997.

    Strain gage and brittle coating pioneers of 1936 featured inthis paper.

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    January/February 2006 EXPERIMENTAL TECHNIQUES 37

  • Top rowleft to right

    Burton McCollum (photo courtesy of University of KansasAlumni Association) (June 1, 1880 July 20, 1984). Burtonwas a University of Kansas BS EE in 1903 and went intopower plant operations, 19031907. Professor in EE, 19071909 when he joined the NBS until 1926. His work with theunbonded carbon gage, culminating in the McCollumPeterstelemeter, was done at NBS.

    He entered the geophysical field, first in private research andin 1924 as President, McCollum Exploration Co. and McCol-lum Geological Exploration, Inc. It appears that some of theseventures overlapped his stay at NBS.

    He was a pioneer in oil field exploration by means of seismo-graphs and located the first oil well by seismographic meth-ods, ever so found, in 1924. Subsequently, he developed manynew devices and inventions. He lived in Houston, TX, after

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    38 EXPERIMENTAL TECHNIQUES January/February 2006

  • leaving NBS. He apparently touched the strain gage field onlyonce, at the NBS as a coworker with Orville S. Peters, whostayed in the field.

    Orville S. Peters (photo from the 19071908 Montanan,Alumni Association, Montana State University) (November30, 1883 August 24, 1942). Orville graduated from MontanaState with a BS EE in 1909 and was an instructor in EE therefor a year. In 1910, he joined the NBS as associate physicistand rose to electrical engineer.

    Presumably, under the influence of Frank Tatnall (see body ofpaper), he set up the O.S. Peters Co. in 1930, manufacturingthe McCollumPeters unbonded carbon telemeter and addedmany other mechanical and electrical strain-related instru-ments to his line over the years. He was under contract toBaldwin-Southwark who marketed his devices and eventu-ally acquired the company by exchange of stock. FrankTatnall tells The O.S. Peters Story well in his book, Tatnallon Testing (ASM, Metals Park, OH, 1966).

    Francis G. Frank Tatnall (photo by Ferdi Stem) (March 9,1896 December 5, 1981). As related in the body of this paper,Frank was the catalyst who brought together inventorsof strain-measuring instruments, mostly mechanical,manufacturing facilities, and the marketing function throughBaldwin-Southwark. Many of the devices he found weremade by the O.S. Peters Co.

    Edwin H. Hull (photo courtesy of Yale University AlumniAssociation) (November 17, 1902 November 7, 1964). Hullwas Yale, class of 1924, when he went to work for GeneralElectric Co. Research Lab in Schenectady, NY. He held pat-ents on elastic mountings, high-speed motor design, etc. Hehad an interest in lubricants. Reissued on December 22, 1931,was Trademark 290,221 for Aquadag, A Colloidal GraphitedWater for Various Uses in the Industrial Arts, which is still ineffect through December 1991. It is still manufactured asa general lubricant by Acheson Colloids Co. in Port Huron,MI. Its use as a liquid-carbon resistance strain gage isdescribed in the body of this paper.

    Second rowleft to right

    Alfred V. A.V. De Forest (April 7, 1888 April 5, 1945).His story is told in the paper.

    Wilfrid L. Bill Walsh (July 23, 1893 September 19,1967). His story is told in the paper.

    Roy W. Carlson (photo from MIT 1939 Yearbook and at theReception for the Carlson Chair, which he endowed at UCBerkeley, November 1984 courtesy of Matrix, Karen Holter-man, Editor) (September 20, 1900 November 20, 1990).

    Bottom rowleft to right

    Dr. Arnold U. Huggenberger (18951981) of Switzerland.See Appendix 4. He is the inventor of the Huggenbergerextensometer, one of the most durable mechanical straingages, used from 1924 through the 1960s and even today.Photo 1965.

    Dr. Earle L. Kent (May 22, 1910 1996). One of the twounwitting inventors of the printed circuit in 1936; see bodyof paper. Photo from 1960.

    Dr. LeRoy C. Paslay (December 26, 1907 May 1, 2001).The second of the two unwitting inventors of the printedcircuit, forerunner of the foil strain gage in 1936. Photo from1985. See body of paper.

    Dr. Paul Eisler (May 5, 1907 1992). The deliberate inven-tor of todays printed circuit. Photo circa 1989. He is holdingthe first radio set using a printed circuit chassis and aerialcoil. Photo courtesy of Maurice Hubert, Multitech, UK, withpermission of Lehigh University Press, from his book: My Lifewith the Printed Circuit, 1989.

    Top rowleft to right

    Charles M. Kearns, Jr. (March 20, 1915, living in Tucson,AZ). Inventor of the bonded carbon gage; see body of paper.

    Dr. Gottfried Datwyler (January 13, 1906 July 30, 1976).He made the first bonded resistance strain gage in 1936 at thesuggestion of Edward E. Simmons, Jr., at Cal Tech.

    Dr. Donald S. Clark (December 26, 1906 November 17,1976). He was in charge of the Impact Project at Cal Techfor which the bonded resistance strain gage was invented.

    Edward E. Simmons, Jr. (March 30, 1911 1904), in white,showing the Longstreth Medal awarded to him by theFranklin Institute, to Frank Tatnall (on the right), and toBaldwin-Southwark management (left). The ceremony washeld in spring 1944.

    Second rowleft to right

    Edward E. Simmons, Jr., with Peter Stein at the February1989 meeting of the Southern California Section of Society forExperimental Stress Analysis.

    Prof. Arthur C. Ruge (July 28, 1905, living in Lexington,MA). Photo by Hans Meier of Prof. in 1938 with his modelwater tank, strain gaged with his (re)invention: the bondedwire strain gage.

    J. Hans Meier (October 9, 1913, living in Vestal, NY). Photoof Hans in 1938 with the Wheatstone bridge he used for hisdoctoral dissertation on bonded resistance strain gages.

    Third rowleft to right

    Dr. J. Hans Meier and Prof. Dr. Arthur C. Ruge whohas just been awarded the Inventor of the Year award by theBoston Museum of Science in 1986. Photo by Maarten Spoor.

    Frank F. Hines (December 5, 1913 2001 in 1939 on hisbachelors thesis concerning strains on a pulley, as measuredwith the new bonded resistance strain gage.

    Dr.WilliamM.Murray (April 24, 1910 August 14, 1990) inJanuary 1960, Phoenix, AZ.

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  • SEM HISTORY

    40 EXPERIMENTAL TECHNIQUES January/February 2006

  • Bottom rowleft to right

    Frank F. Hines from the 1939 MIT Yearbook and at the 1989Jubilee Celebrations, 50 Years of Strain Gages, Load Cells,and Stresscoat.

    Greer Ellis (June 7, 19101997) inventor of Stresscoat(RTM), at the 50th Jubilee Celebration of his invention atthe SEM International meeting in Portland, OR.

    Dr. William M. Murray with his wife, Joan, at his retire-ment from MIT in 1973.

    About the AuthorPeter K. Stein, MSc, PE, President, Stein Engineering Serv-ices, Inc. Professor emeritus of Engineering, Arizona StateUniversity, 5602 East Monte Rosa, Phoenix, AZ, USA.

    Arranger and organizer of the Golden Jubilee Celebrationsfor the Commercialization of Strain Gages, Load Cells, andBrittle Coatings, as follows.

    19381988: Fifty Years of Strain Gages, Load Cells & BrittleCoatingsThe WRSGC/TCSG/SEM Jubilee, Portland, OR,June 910, 1988.

    19381988 Jubilee: Bonded Resistance Strain Gages, LoadCells and Brittle Coatings: The IMEKO TC-3 & TC-15 JubileeOctober 19, 1988, Houston, TX.

    The Mini-Jubilee of May 31 June 1, 1989, Hyatt RegencyHotel, Cambridge, MA. SEM Meeting. Lf/MSE Newsletter,No. 32, Summer 1989, pp. 312, from Stein Engineering Serv-ices, Inc., 5602 E. Monte Rosa, Phoenix, AZ 85018.

    The Strain Gage Mini-Jubilee of January 27, 1990 atCalifornia Institute of Technology. Lf/MSE Newsletter, No.34, Summer 1990, pp. 331, from Stein Engineering Servi-ces, Inc., 5602 E. Monte Rosa, Phoenix, AZ 85018.

    The 80th Birthday Celebration for Edward E. Simmons, Jr.,Peppermill Restaurant, Pasadena, CA, March 30, 1991.

    Strain Gage Inventor Turns 86: Dr. Arthur C. Ruge Other-wise Known as Prof. Lf/MSE Newsletter No. 37, January1992, pp. 1415, from Stein Engineering Services, Inc., 5602E. Monte Rosa, Phoenix, AZ 85018. Birthday celebration heldat La Bellecour Restaurant in Lexington, MA, August 20,1991.

    The author is still excavating strain gage history. Any helpwill be most welcome if you have additional information orcorrections. n

    SEM HISTORY

    January/February 2006 EXPERIMENTAL TECHNIQUES 41

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