The First SPirules

The end of World War II had precipitated a bust to the aviation industry boom years of 24/7 factory aircraft assembly lines. Industry executives realized they would have to re-invent their companies to survive. Far-sighted executives such as those at North American Aviation understood that this new industry to become known as “aerospace” would be founded on technologies that World War II had either jump-started or promoted to a new level -- e.g., radar, propulsion systems, materials science, inertial guidance, and automatic control systems based upon servo-mechanisms. Application to their business of the war-time advances would require re-training both their current workforce and college hires, most of whose text books bore pre-war publication dates. 

Walter Evans’s wartime work experience at General Electric in Schenectady, New York and his classroom experience at Washington University in St. Louis made him an ideal new-hire for North American Aviation. He could bring to bear both his experience as a practicing engineer and as a teacher of the latest developments in servomechanisms -- a field critical to North American’s goals of achieving the dominant position in guided missiles. At General Electric, Evans had become intrigued by a graphical technique called “flux plotting” invented by a Swiss Professor Paul Profos. At Washington University he worked to extend the flux plotting idea with the encouragement of two mentors -- John R. Moore and Dr. Frank Bubb. Evans later enjoyed joking that Profos’s ideas “got me off the jw axis” -- a reference to the one-dimension focus of “frequency response” -- the reigning servomechanism analysis technique of the time. Upon his arrival at North American in June 1948, Evans shared with his new colleagues the techniques he had developed and received further encouragement from two in particular, W. D. (Bill) Mullins and R. M. Osborne.

And so, no sooner had Evans moved his family from St. Louis into a small Santa Monica apartment and its short commute to North American’s Aerophysics Laboratory on Aviation Boulevard in Inglewood, that he found himself teaching his new colleagues analysis of servo-mechanisms. His carefully hand-written and typewritten teaching notes preserve a record that nails the date of the birth of root locus to a lazy Monday -- August 23, 1948. It was his eighth or ninth class of the summer, and in Evans’s notes he lays out “several different methods for designing a servo-mechanisms, including the (1) frequency response method, (2) differential equations, (3) experimental, and (4) combinations -- itemizing the advantages and disadvantages associated with each method. His classroom goal was to achieve instruction tailored to the needs of each student. His subject that day was a question guaranteed to solicit strong re-actions. Although he himself had strong opinions, he sought to understand the reasons why others held different viewpoints. His course notes that day exemplify his sensitivity to diverse points of view.

The choice (referring to servo-mechanism design methods) depends not only on the problem at hand, but also upon the previous experience of the designer. Thus many men who are accustomed to thinking of servomechanisms in terms of examples that they have seen will probably lean heavily upon their own physical picture of their operation. For them, the output lag behind the input can be decreased by using “anticipation”. Other engineers, particularly those with extensive background in analysis of electric circuits, are apt to prefer the frequency response method. In this method the servo is described in terms of its response to a wide range of frequencies and corrective action is taken in terms of band-elimination filters. 

Finally a person who has had extensive experience with differential equations will tend to stay with this method and thus find himself devoting considerable effort to finding the roots of equations. Unfortunately, no one single method by itself is as useful as knowledge of all three. Any attempt to classify the advantages and disadvantages of each method is bound to be highly colored by opinion. 

His notes then proceed to acknowledge that he is not impartial on the subject at hand:

With a warning to the reader that the writer has been involved in several rather heated discussions on this matter in on previous occasions, the following is an attempt to describe the merits of each.

The situation Evans described to his students was of a field still formalizing its methodologies. MIT’s Radiation Laboratory had been the pre-eminent center of excellence of the control-system universe during World War II. In 1948, its Instrumentation Laboratory (legendary Clark S. Draper, founder and director) and its Servo-Mechanism Laboratory (Gordon S. Brown, director) were applying so-called “frequency response” analysis techniques that use the Bode Plot and Nyquist Diagram, named after their pre-war developers --Harry Nyquist and Hendrik Bode of Bell Laboratories. MIT’s Gordon Brown, along with his associate Campbell, had just published the first seminal edition of Theory of Servo-Mechanisms(Wiley, 1948) in what would become a seminal textbook. 

Evans understood the frequency response method, but counted himself among those “who had extensive experience with differential equations (and) will tend to stay with this method and thus find himself devoting considerable effort to finding the roots of equations.” The equation Evans refers to is the “characteristic equation” of a control system. For simple feedback control systems, the characteristic equation is can be expressed as a quadratic algebraic equation (ax^2 + bx + c = 0), and as middle school algebra students are taught, its solutions or “roots” are obtained from a formula: x = [- b +/- root(b^2 - 4ac)]/2a). However, more complex feedback systems of interest to Evans and his colleagues -- those with two or more sources of delay -- are of a higher order than quadratic, and, as middle school students learn, no closed form solution exists. It may have been while Evans was explaining this point on August 23 that an unknown NAA engineer/student asked him 

“How large can the second time delay in a system be compared to the first one before the rules for a quadratic to be too much in error?” 

Evans would later refer to this case as the “slightly” cubic problem, the key word being “slightly”, for his teachers had taught him the importance of finding approximate solutions for complex problems. He later attributed his grappling with answering the questions as the trigger for his root locus technique. What is clear from the dates on his class notes is that the question inspired him, because those he prepared for classes two and three weeks later introduce root locus’s graphical approach to plotting roots for characteristic equations of any order. (A-1 through A-5). His student colleagues instantly preferred this new explanation to any they had seen before. Root locus was born. In a matter of just a few more weeks Evans prepared the draft paper of a paper and submitted it to the AIEE on November 1. North American published it as report AL-787. 

Evans’s September 1948 class notes, the earliest descriptions of root locus, strongly suggest that he had arrived at the root locus idea by using approximation techniques as his Washington University classes had emphasized. On the page of his September 7 notes that apply root locus to systems with multiple time delays (i.e., higher order than slightly cubic), he wrote

The above procedure represents a trick which is often handy: Simplify the problem down to one for which the answer is known, -- then change the answer slightly to allow for the extra complications. Another trick which is frequently handy in many problems (not just this particular graphical scheme) is to take the extreme case.

In a 1961 letter to his Washington University’s Engineering School’s former Dean, Alexander S. Langsdorf, Evans wrote

The General Electric Advanced Engineering Program put great emphasis on solving practical problems in approximate form starting from a few basic principles. ... I personally learn most effectively by starting from simple examples and working up. Washington University was excellent in that professors such as yourself, Professor Glasgow, Dr. Bubb, and Dr. Middlemiss could and did take a student all the way back to the beginning if necessary, and work up to the question at hand. 

Thus, the root locus idea was born in a classroom taught and attended by practicing engineers. The form of a question resonated with a teacher who sought to satisfy his individual student’s needs. That he developed the answer into a paper was due in considerable measure to the enthusiastic response to it of students. As practicing engineers, the students who learned a new problem solving technique were in a position to make use of it immediately. As they put Evans’s ideas to practical use, the ideas began to spread within the Aerophysics Lab at North American Aviation and beyond.

A “Plastic Device”: September 1948 -- November 1948

Joined at the hip at the birth of root locus was a need for an aid to designers to sum angles and multiply the distances from a trial point “p” on the complex plane to other fixed points on the plane. Evans’s own September 14 classroom notes describe his initial approach using transparent overlays held together with a thumbtack:

Place a transparent sheet on top of the diagram, draw the red line for reference, stick a thumbtack through at the guess point to serve as a pivot. 

One of Evans’s colleagues (and a student in Evans’s servo class) was Jeff Schmidt. Schmidt’s assignment in the summer of 1948 was to design an analog autopilot for the NATIV missile. It had to work without adjustment throughout the changing mass and center of gravity during the launch phase. Schmidt was stymied until Evans presented root locus September. In 2003, Schmidt recalled

When Walt first started discussing Root Locus in his class I saw a ray of hope. While the problem was still very difficult, I could at least get a feel for what I was trying. As more people started to use Walt’s method, many ideas for automating the plot were thought of.

I was looking for something better than transparent paper to add angles. I went over to the engineering shop and made an “angle adder” out of a circle of plexiglass with a straight arm held on with a small bolt. This worked much better than the transparent paper for determining the locus, but I still had to measure lengths and multiply them to get loop gains. Walt and I were kicking this problem around one day and we came up the idea of adding a logarithmic spiral to my angle added. This worked well and became the first spirule. (A-24).  I applied for a patent but the company decided a copyright was more appropriate.

The spiral shaped curve was key to simultaneously using the principles of a linear slide rule (i.e., multiplication by addition of logarithms) and performing the addition with the circular protractor. DeWitt Lyon, a colleague of Schmidt and Evans, looked at the spiral curve on Schmidt’s device and coined the name “Spirule” as a contraction of “spiral” and “slide rule”.

Evans’s November 1948 paper referred to this creation when it stated, “a plastic device has also been developed to greatly improve the actual mechanics of this procedure.” In Appendix B of his second (March 1949) draft paper Evans wrote:

A “Spirule” has been developed which, with a little practice, permits a particular p-point to be calculated in one minute for a system involving 10 dots and crosses, of which only 1/4 of this time is needed for adding angles.

The same paper encouraged its readers to duplicate the spirule for themselves with pieces of transparent paper and his words of explanation -- the first of many occasions in which Evans would suggest to others that they need not purchase a spirule from him to teach (or to learn) the principles involved in root locus -- they could spin their own.

Ties between UCLA and North American Aviation were particularly strong in those days. Dr. Edlefsen, deputy director under William Bollay of the Aerophysics Laboratory, hired UCLA’s Professor John Barnes as an assistant. In September 1948, John Moore, became UCLA’s first “Visiting Associate Professor of Engineering” and began evenings and Saturday to teach a graduate-level course in the principles of servo-mechanisms.[1] 

In the spring of 1949, John Moore invited Jeff Schmidt to lecture his graduate servo course at UCLA on the use of his spirule. Schmidt recalled in December 2003:

After the first spirule had showed its worth, a design was made for a more precise model. A bunch were made for use in the department. After my demonstration in John Moore’s servo class, employees of several large aerospace companies asked for a set of drawings. Hughes had several hundred made, but the person doing the assembly looked at the assembly drawing and cemented the parts together in that position. Since nothing could rotate they were worthless. Walt commended that Howard (Hughes) could afford to build another set but to advise him not to try making them of wood like his Spruce Goose.

Among the students in Moore’s UCLA class was a Northrop engineer – Duane McRauer.. 

The Northrop Corporation produced a “root locus plotter” in the spring of 1949 (A-7). On the backside of the drawing is the following hand-written note:

Dear Walt, 

This a print of the root locus plotter dreamed up here at Northrop. I believe it will solve all problems of friction, etc. We are having several made up by Vard in Pasadena. Best regards to you and the boys at Aerophysics.

The enclosure, dated June 15, 1949, contains a drawing of a 13’ x 5” Lucite card with a spiral curve and a 1” diameter inset disk affixed to the card with three radial spring-loaded legs. A 0.03” pointed “fintle” at the center of the disk provided the pivot point. The drawing shows a rather smallish disk without any markings that would permit it to be used to add angles. It does have the characteristic spiral curve on the arm radiating outward from the pivot point.

Kulda’s attention to “the problems of friction, etc.” and the detail the drawing gives to the construction of the attachment of disk and arm at their common pivot point was a foreshadowing of things to come. No other aspect of the future Spirules construction would receive nearly as much attention (or controversy) as its pivot mechanism[2].

North American organized in April 1949 a series of “Servo Seminars” (A-6) at which engineers such as DeWitt Lyon, Evans, Norm Parker, Ken Jackson, R. M. Osborne, and John Moore taught their colleagues in their respective areas of expertise. Interestingly, Jackson and Osborne had already mastered root locus well enough that they made the presentations on its use in the design and analysis of autopilots. Evans met with engineers of all stripes -- young and old, impressionable and stuck in their ways. Some went away simply impressed by Evans’s mastery of the concepts, but others followed and became effective and enthusiastic champions themselves of root locus. These people included men like Ward Harmon, Ken Jackson, Bob Cannon, Jeff Schmidt, Mark Campbell, Bill Mullins, and John Moore. It was through these root locus “disciples” that the ideas began to spread, even as the AIEE vetting process dragged out the paper’s publication. 

Another school teaching servo-mechanisms to engineers from aerospace companies was Caltech, where a young professor, Charles Wilts, taught the servomechanism class. He incorporated AL-787 into a 1949 class. In a letter dated October 1, 1949, Wilts sent Evans a personal letter thanking him for making AL-787 available to him and enclosed a list of 35 names of engineers affiliated with ten companies and government organizations who wanted their own copy. (A-9). [3]

As 1949 came to a close, Evans signed a contract with McGraw Hill publishers. He pinned his hopes on more widespread dissemination of a complete development of his method in book form. 

Presentation and Aftermath: January 1950 -- April 1950

With the AIEE Transaction’s committee’s acceptance of his paper, Evans’s root locus ideas had their first forum outside of Southern California, the January 1950 Winter Meeting of the Feedback-Control Systems Group of the AIEE in New York. Evans traveled to New York to make what turned out to be a very well received presentation on root locus and at which Evans described the spirule. After the talk, some seventy attendees expressed interest. Buoyed by the response, Evans returned to California. However, the post-conference follow up more closely resembled a trickle than a deluge. 

Evans’s files of correspondence documents the response. Three letters were sent in March 1950. (A-9) The first to arrive, dated March 1, 1950, came from W.C.Osterbrock, head of the University of Cincinnati’s Department of Electrical Engineering. On March 21 Professor R.C.H.Wheeler from the U.S. Naval Postgraduate School in Annapolis wrote, asking, “Have you made the ‘Spirule’ for sale? If so, how can I obtain one?” On March 27, W. E. Meserve, Professor of Engineering at Cornell, reminding Evans he had told his audience that if one wrote to him, Evans would provide more specific information on how to procure “the slide rule device you described.” 

Evans waited until April 1950 to provide individualized responses to his three new correspondents (A-10), explaining he had waited until he had received copies for distribution of his AIEE paper. To all three, his response included the followingt:

Thank you for your interest in the root locus idea. As you may recall at the AIEE meeting, approximately 70 indicated an interest in obtaining a spirule. Since then, only 3 persons have written. This presents the following problem in costs: $30 each for a machine shop model, 50 cents each for a stamped model in a lot of 500. The spirule isn’t worth $30 and the demand is far short of 500! It looks like they won’t be manufactured until some intermediate method is found or until I finish writing a book in which the spirule is to be enclosed. 

Meanwhile, I believe than much can be learned particularly in classroom work, by working problems in which the angles need for the locus are just estimated by eye. Most problems have enough special points that the angle will be correct to within 10 degrees. The product of the line lengths needed for computing the gain at any one point can probably be estimated to within 20%. 

Of the three, W.C. Osterbrock wrote back (A-11), prophetically, to encourage Evans: 

“I wonder whether you are justified in your doubts about the demand for the ‘spirule’. We could have disposed of 65 at a reasonable price, and we shall have another class of about 80 students in servo this summer. Undoubtedly other schools teaching the subject would be glad to recommend it to their students, if properly circularized. Thanks again for your help, and I hope you will find it possible to have the ‘spirule’ produced and made available.”

In March 1950, AIEE Transactions published Evans’ paper on root locus. The paper’s publication produced few new written inquiries about root locus. One letter did arrive from Edward Samario, a graduate student of George J. Thaler’s at the University of Notre Dame, who learned from an NAA recruiter of the availability of Evans’ more extensive NAA servo class notes.

John Truxal, an influential ally: May 1950 -- August 1950

The last six months of 1950 produced a steady stream of requests for copies of Evans report AL-787 and/or reprints of this AIEE paper. Most of the received letters make no reference to the spirule, however. 

In August 1950, an MIT graduate student, John G. Truxal, receiving guidance of Professor E. A. Guillemin, published Technical Report 162 as his doctoral dissertation. Its title was “Servo-mechanism Synthesis through Pole-Zero Configurations”. Truxal’s report references the AIEE paper Evans presented at the 1950 AIEE Winter Meeting. Upon his graduation, Truxal accepted a position at Purdue University as an assistant professor. There he became an influential champion of the direct synthesis approach they were both pursuing. In April 1951, Truxal wrote a cordial letter to Evans, in which he associated himself with this new approach to control system synthesis.

I was quite pleased to hear while at the IRE Convention in New York of the wide acceptance your ideas seem to be gaining particularly the underlying philosophy of controlling both the transient and the frequency responses through control of pole and zero positions. I believe people are slowly beginning to realize that the necessity in so many problems of control over the effect of load-torque disturbances or other corrupting signals, etc. practically screams for a synthesis with some concern over the actual positions of the relevant poles and zeros.

New Allies Speak Out: September 1950 - December 1950

The oldest drawing (704-83391) by Evans of a Spirule is an undated blueprint probably drawn in the spring of 1950. On it, Evans references a “final drawing” (704-952010) dated September 5, 1950. Soon thereafter, in an NAA inter-organization memorandum dated October 19 from R.M.Osborne to W.J.Toher and approved by John Moore, Osborne appeals for funds to underwrite the fabrication of 500 Spirules (A-12). Osborne’s memo refers to engineers having built a variety of their own hand-fabricated spirules, the use of root locus among engineers at NAA, Hughes Aircraft, and Northrop, and its 

“being taught in several colleges we know of as part of the standard curriculum in the theory of servomechanisms.” 

He went on to estimate the cost at 35 cents a piece in quantities of 500, with distribution might include their presentation as “souvenirs” to visitors. The memo also stated there was a “large demand for copies of AL-787, the root locus report. Interestingly, he wrote “it might be in order to send spirules as well as literature to such places as colleges, Government agencies, and possibly other companies.” He concludes, “Since we have an urgent need for additional spirules, it will be appreciated if prompt consideration will be given to this situation.” Osborne’s October appeal with NAA management, however, was to suffer a fate similar to Evans’s appeal for prompt attention to his root locus paper -- it became mired in a committee. On December 8, 1950, Evans wrote a status report to Dr. Edlefsen (A-13):

The plastic spirule sample was made by our shop and required one (1) man-day, it was therefore deemed to be too expensive to make in quantity. The drawing was made of a photographic method of making a die and printing five hundred (500). This involved printing these patterns onto a ten-thousandths thick piece of plastic, and then laminating ten-thousandths plastic on each side in order to give it body and have the printing on the inside. The bearing joining the disc and the arm was to be a simple eyelet with a light friction fit. We plan to add a little plastic plug in the center of the eyelet to hold a small needlepoint to serve as a pivot. 

One week later, on December 16, 1950, Dr. William Bollay spoke on the subject of “Aerodynamic Stability and Automatic Control” as the 14th Wright Brothers Lecture at the prestigious Institute of Aeronautical Sciences in the U.S. Chamber of Commerce auditorium in Washington, D.C. This lecture, and its publication nine months later, truly put root locus on the map. Bollay had stayed late many nights learning his subject thoroughly from his autopilot engineers. Bollay presented Evans a copy his paper (A-15) on which he wrote:

To W. R. Evans

With my sincere appreciation for your collaboration on this report. May it serve to disseminate the Evans Root Locus Method among the aeronautical engineers.

Sincerely, W Bollay

 

A Nine-Month Gestation: January 1951 -- September 1951

The year 1951 began with no apparent progress in finding a mechanism to underwrite the several hundred dollars required to fabricate 500 spirules and that Osborne had requested in his October 1950 NAA memorandum. Meanwhile, demand was building, as evidenced by a sharp increase in requests for Evans Root Locus report AL-787.  

Word-of-mouth appears to account for a good part of the more widespread interest. For example, Ward Harmon, a friend and former NAA colleague, had recently accepted a position in the electrical engineering department at Stanford University, where he became an effective ambassador of root locus. Joseph Chadwick, a research associate at Stan-ford’s Electronics Research Laboratory, said of Harmon in a letter dated January 8, 1951 (A-14): 

“Mr. Ward Harmon, recently of North American, has proved such convincing salesman of your Root Locus Method, that he has exceeded his ability to inform. ... Also, is there any way I could beg, borrow, steal, or buy a couple of your celluloid gadgets for summing angles, etc., to use on my project here?” 

Unfortunately, no. Evans, in his February 1951 response (A-14), summarizes the state of affairs of his “celluloid gadgets” as follows: Our efforts to get some spirules have been snarled in accounting procedure because the logical thing is to make a lot of them which could be given away.  On March 22, 1951, Evans attended meeting of specialists met to investigate the application of Nyquist’s criteria to dynamic systems. In April 1951, Evans compiled a list of all the names and addresses of fifty individuals who had sent letters other otherwise made known their interest in an Evans root locus paper. 

Evans himself was actively looking for companies interested in quoting him a price for a batch of spirules. Three companies turned him down outright and three other companies did not respond to his letters. Finally, however, one company, Cellulose Products in South Gate, California, indicated it was prepared to try to meet the specifications of the spirule. Thus began a decades-long business relationship between Evans and Cellulose Products. North American contracted with a partnership named “Universal Equipment Company” in Culver City received the first bill for spirules on April 30, 1951 for a lot of 513 spirules printed on vinylite with the name “Universal Equipment Company” printed on each spirule. No sooner had the Universal Equipment Company received credit for fabrication of the spirule, the partnership dissolved. Evans himself paid the bill on May 22, 1951 (A-18) and all orders for spirules directed to the Universal Equipment Company were routed directly to Evans.

On June 14, Evans sent Roy Fry a letter in which he wrote, “Enclosed is the “Spirule” which has long been promised to you. I believe that you will find it self-explanatory; the instruction sheet is not yet prepared.” (The Spirule was many things, but “self-explanatory” was not among them.) The letter to Fry is the only dated record of delivery in the spring and summer of 1951. Evans kept a handwritten list of engineers to whom he gave spirules. The list suggests he distributed thirty-one to colleagues, including Bill Bollay, John Moore, Norm Parker, Jeff Schmidt, Dave Chandler, Jesse Bowman, Al Grant, Walt Pondrom, and, from within Evans’s own platform servo department, C. J. Triska. He wrote their names on a 3x5 index card he kept on his desk at work. 

The absence of any orders for spirules in the spring and summer of 1951 is something of a mystery. What is known is that immediately after Bollay’s Wright Brothers Lecture was published in September 1951, Evans began a new list that recorded sales -- not samples. The published edition of Bollay’s lecture gave root locus and the spirule a real boost and put them into the mainstream of feedback control systems. Bollay gave Evans’s technique equal status with the better-known Nyquist plots and Bode diagrams used by those who favored the frequency response methods of servo analysis. Bollay acknowledges the value of Nyquist and Bode plots but went on the say, 

In comparing the Bode or Nyquist presentation with the Evans root-locus method, we note that the Bode or Nyquist diagrams permit the direct use of experimental data; thus they do not require the approximation of the frequency response curves... by those of a second order system. The Evans root-locus method presents directly a complete picture of the stability and transient response that are most important for aircraft control. 

Its merits are as follows:

1. The root-locus gives the roots of the closed-loop system directly, and, by a simple calculation, the transient response. 

2. The degree of stability can be read from the root-locus plot directly

3. Complicated systems can be set up in such a fashion that the effect of the transient response and stability of changing any parameter in the problem can be easily visualized.

4. There is no ambiguity of confusion concerning interpretation of the plots even for complex systems having any number of roots and poles in either the right or left half of the complex plane.

Bollay’s paper cites Evans’s Aerophysics Laboratory report AL-787 report and the journal article pictures the recently fabricated Spirule imprinted with the name Universal Equipment Company.

Initial Spirule Sales: October 1951 -- December 1951

On October 2, an “Avoid Verbal Orders” form from C. J.Triska lists the names of six engineers as the first engineers to pay for spirules (A-19). The first non-NAA order, dated October 11, came from Stanford University’s Joseph Chadwick -- $6 for three spirules (A-20). Chadwick joked in his letter “if Ward Harmon hasn’t got a new spirule already, I’m going to surprise him with one of these, as his home-made one is not too efficient.” Charles Wilts of Caltech’s Analysis Lab placed the next order (A-20), dated October 12, -- two spirules with instruction sheets for a total cost of $4 and sent directly to Evans’s home on Maple Street in Whittier. 

Five days later, on October 17, Edward Samario, the former Notre Dame graduate student and now at M.I.T. placed orders for five spirules for ten dollars (A-20). Hence, within a week of each other the first sales to academic institutions arrived from Caltech, MIT, and Stanford. The quantity of ten and sales of $20 may have been modest, but the return addresses were a promising beginning.

Fred Powell, a project engineer at Bell Aircraft in New York, placed the first order from a corporate customer on October 16 -- four units for $8.00 (A-20). Powell was among those in attendance at the March 1951 meeting of specialists sponsored by the IAS. Following Bell came order from the University of Illinois, Urbana (Frank Koenig) (A-20), Washington University in St. Louis (A-20), the University of Washington, and the University of California. 

In November, the same R. M. Osborne who had written an appeal for company funding a year before, had the pleasure of writing a more positive letter (A-21), announcing 

Arrangements have been made to have a number of spirules fabricated in accordance with the design which was arrived at after extensive discussion with those persons who had experience in their use and the need for those tools. ... Spirules ordered on RBR may be assigned to individuals on a temporary or indefinite basis. But are Government owned property and must be accounted for as such. Individuals desiring to personally own these spirules may obtain them from Mr. W. R. Evans at a cost of $2.00 each.

College Bookstore Orders: January 1952 -- March 1952

Orders continued to flow in, some sent directly to Evans at his Whittier home, some to him at his North American Downey address, some to the Universal Equipment Company in Culver City. The most significant developments in the first quarter of 1952 were the enthusiasm of two engineering professors from the University of California -- Joseph Beggs of UCLA and Otto Smith at UC Berkeley (A-21). 

The UC schools’ embrace of root locus and the spirule into their department’s feedback control classes and laid the foundation for spirule sales to university bookstores. Joe Beggs and Otto Smith were in a vanguard of professors at UCLA, Berkeley, Stanford, and Caltech who chose to introduce the new root locus methods into their classes, many of whom had selected Campbell and Brown’s 1948 Servomechanism book as their text. (Many other schools followed suit, but only after root locus had made its way into other textbooks.) The March 8 order for 12 spirules from Berkeley ‘s associated student store notes “We have been asked by Prof. Otto Smith of Electrical Engineering to carry these in our department. We do not know the rule but he states that there will be a continued demand for them. This rule was invented by W. R. Evans”. (Note: Berkeley’s bookstore seemed confused about how to order them. Evans received their first order via the “Robison Corporation” at Universal Equipment’s Culver City address and their second order was addressed to the “W. E. Evans Company” at Evans’ home address. 

In March, an order of 55 spirules for resale by UCLA bookstore and 30 for resale by the University of California at Berkeley bookstore and 20 from Caltech’s Charles Wilts for his servo-mechanism class. The supply from the initial batch of 500 had begun to run dry. The Universal Equipment Company partnership had dissolved and the new owner wanted to raise the price of the Spirule. Having successfully completed the assembly, correspondence, billing, and shipping himself, Evans decided he would take over the entire enterprise. 

On March 27 he filled out Certificate of Business forms and submitted them for publication in the local newspaper, the Whittier News. There, on April 8, 15, 22, and 29 was published the following announcement (A-22): “The undersigned does hereby declare that I am conducting a mail sales business at 1706 Maple Street under the fictitious name of The Spirule Company.” 

The Spirule Company: April 1952

And so it came to be that on April 11, 1952, when Shedon Saks wrote to Evans for his order of a Spirule, thereby exhausting the batch of 500 which Evans had once predicted was a number that would exceed all demand, that the Spirule Company had been born over three years since North American published AL-787 in November, 1948. It came from an individual who was a practicing engineer, but taking a servomechanism course. UCLA courses in particular created a demand for Spirules, and so Saks’s UCLA connection was not surprising. Its arrival at 1706 Maple Street as letter requesting directly from Evans just one spirule, to which an individual shipment and letter accompanied the response, and subsequently a letter in return, was typical as well. Thousands of similar requests arrived at Evans home over the subsequent years. 

Evans immediately placed an order to Jesse Hogan of Cellulose Products for a second batch of 500 spirules in April 1952 (A-23). He informed her in an April 5th letter to replace the label Universal Equipment Company with The Spirule Company, and informed her that “he would be away next week.” It was spring break for his sons and he would be traveling with his family on a spring vacation holiday. He and Arline would celebrate their 10th Wedding Anniversary on the trip in addition to celebrating the founding of a company that they would operate together for another thirty years.

Others were celebrating that day besides the future president of the Spirule Company. Other future United States presidents were celebrating. Dwight Eisenhower asked to be relieved of his duties as Supreme Allied Commander of NATO on April 11 to make his run for the presidency. Also on April 11, 1952, a young congressman from Boston announced he would run for the US Senate seat from Massachusetts -- John Kennedy. Walter and Arline Evans celebrated that evening the tenth anniversary of their wedding. Arline had just entered her third trimester of a pregnancy that would produce in June the third child of their marriage, Nancy Arline Evans. 

[1] Several years later, when the Spirule became available, he required his students purchase them from the UCLA bookstore, whose purchases over the years exceeded that of any other institutional customer.)

[2] Evans’s records do not reveal whether Kulda ever had his design constructed by Vard. The name Richard Kulda is absent from all other correspondence. A Google search found a record of the Vard Company in Pasadena and its founder Vard Wallace. It was a supplier of drafting equipment and, interestingly, a unusual telescopic front fork Vard built for Harley-Davidson. The mystery of whatever became of the Northrop design remains unsolved.

[3] Almost exactly two years later in October 1951 Caltech’s Wilts would be among the first to order a Spirule.