This article is in Bob Pease on Analog Vol. 1 in the Analog section of the Electronic Design Library.
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A little while ago, I ran across an article in Trains magazine (Oct. 1994, pp. 46-49) about “Martin Blomberg, designer extraordinaire.” What did Mr. Blomberg design—a snazzy engine paint job? A new Diesel engine? Nope. He designed the “Blomberg truck.” It’s an improved frame that goes under each end of an engine—a wheel assembly with two axles, four wheels, and two big 300-kW electric motors. The truck was designed by Mr. Blomberg for the Electro-Motive Corp., a subsidiary of General Motors Corp., in 1937. This was first used on a Demonstrator freight locomotive, which logged 83,000 miles on 20 railroads in 1939-1940, and was acclaimed as a great success wherever it went. Blomberg’s truck is still in use today on most of the GMC freight locomotives. I think that’s pretty good for a piece of 1939 engineering.
Why was the Blomberg truck considered such a good design? Well, previously, diesel passenger engines ran on flexible six-wheel trucks with two traction motors. The middle axel carried weight, but was not available to be powered. The early Diesel-electric engines had rigid four-wheel trucks and were suitable for yard switchers, not for long-distance, high-speed freight hauling. They had as good stability and ride comfort as steam freight engines, but not much better. In the late 1930s, Diesel engineers had to plan new freight engines that could move freight at fairly high speeds—but put out more power and more tractive force than any passenger locomotive. In other words, they had to provide the advantages of all the old, slow diesel switcher engines—and the advantages of the sleek fast passenger engines—yet put out a lot more power.
Mr. Blomberg’s new truck design did that. It put all the weight on the driving wheels without any unpowered axle. He provided a firm but flexible suspension, putting all the weight evenly on all four wheels. According to the article, “He designed the truck with a minimum of assistance, for there were no others at EMC acquainted with truck design. Strain gauges were crude, and finite element analysis was decades away. The designer himself had to rely on fairly simple calculations and a strong sense of mechanical aptitude, with perhaps a little luck added.”
So, what kind of man was Martin Blomberg? “He could be very courteous, but his standard answer, if anyone approached his ‘territorial waters’ with a suggestion was, ‘Ve do it my vay.’” Does that sound like anybody you know?
Recently, I was trying to write down the Job Description for a Product Engineer. Just for the heck of it, I also wrote down, for comparison, a definition of a Design Engineer. There’s a lot of similarity, a lot of overlap, except for one major difference: A good Design Engineer not only has to put together a lot of circuit functions, using known designs, but he also must know when existing designs aren’t good enough, and when and how to make new circuits.
What is a “Designer”? Is he/she a person who designs circuits? Wears flamboyant clothing and plans the décor for a house or an office—or a locomotive? Designs the transmission or the grille for a new car? Well, yes, a designer can be any or all of these things. But after you learn how to analyze things and prove the feasibility of a design, it’s also of great value to be able to invent new circuits—new designs. To do that, you have to be familiar with lots of old designs. You have to know what each old design did well, and what it did badly. Basically, you just have to KNOW a lot of old designs.
When I started designing discrete-component op amps in 1061, I studied every circuit I could lay my hands on—voltage regulators, vacuum-tube circuits, transistorized circuits. I used good old, proven circuits when I could and invented new ideas when the old ideas weren’t good enough. As I said in my first column four whole years ago, “computers may be able to help you optimize a given design, but it is not necessarily helpful when the old design is not good enough.” Guys like Bob Widlar, Bob Dobkin, and many others knew how to innovate. I can’t say I’m in the top echelon of innovators, but I know how to get a job done.
Note, you can learn a number of things in school, in college, but almost nobody learns a lot of circuits—or a lot of anything in detail. In the old days, a person had to LEARN a lot of circuits to get his amateur radio license. But these days, learning about and understanding a number of radio circuits—receivers and transmitters—is no longer required.
When I began to get interested in circuits around my senior year, when I got out of the Physics course and into EE, I got an appetite for learning a large number of circuits. I really got engrossed in this, as if it were a hobby. Only if you’re REALLY interested in a field, like the most enthusiastic hobbyist, will you learn all the history of design, so you can tell when you have to break new ground and invent new circuits. Most students never get that interested—they have to take a smattering of course on many different subjects to be able to graduate. That’s not the kind of intensity you need to be a good designer.
In addition, when you’re innovating, you must be good at circuit analysis so you can see problems, drawbacks, and limitations of new circuits. You must be good at this, by intuition or by quick analysis, so that you don’t have to drag every new circuit through a long, slow Spice analysis. Besides, as I’ve mentioned many times, Spice might tell you a circuit would not work even when it really does. You can’t run every potentially good idea through Spice.
Recently, I was trying to design a low-power R-S flip-flop in a bipolar circuit. I invented about four designs. Each one looked pretty good until I really did a one-minute pencil-and-paper analysis. Blah. They would not work. I finally asked a buddy for advice. He told me about a circuit he had used. We couldn’t use that one due to power-supply limitations. But, I modified that circuit to go with some low-voltage compactors I already had and everything clicked. I haven’t even bothered to breadboard it, nor to Spice it, because I can see how it has to work, perfectly, using just a little pencil and paper.
Now, I try to avoid saying good or bad things about a competitor, so I won’t. But I will mention something about a new design made by a kid engineer at National about 20 years ago. Once upon a time, we had an LM109, designed by Bob Widlar, and it was good for about 1.5 A at 5 V. We also had an LM140, designed by George Cleveland. It had a much smaller die size and would do at 1.5 A at room temperature, but only 1 A at all temperatures.
It was designed to be competitive commercially, especially when competing with Fairchild’s UA7805. Unlike the LM109, the LM140 came in several different voltages—5, 6, 8, 9, 10, 12, 15, 18, and 24 V. We knew that, obviously, customers needed various different output voltages.
About 1974, Bob Dobkin asked Brent Welling, the Manager of Marketing for Linear, “What if you could have an adjustable voltage regulator that you could adjust to any voltage from 1.2 V to 40 V?” Brent asked, “Will it cost more to manufacture than an LM140?” Answer, yes. So Brent said, “Well, then there will not be any possibility of significant sales.”
I’m not exactly sure how we did it, but in those days at NSC, we didn’t have “teams.” We didn’t exactly have consensus. We didn’t always have harmony and sweetness and light. But we had ways of getting parts out. I wonder if we wouldn’t be better off if we could reconstruct that..
Anyhow, Bob Dobkin convinced us to get the LM117 into production, and it was a big winner. Of course, the LM117 has never outsold that LM140 in number of chips sold, because the LM140 was quite adequate for simple requirements. But the LM117 made a good profit because it made lots of customers happy in critical applications.
Why? Well, it had a BIGGER power transistor with more ballasting. So, you could get more power out of it, at higher voltages, without blowing it up. Some of NSC’s competitors tried LM117’s good control circuit. But they used a smaller power transistor so they could get a cheaper, smaller die. As a result, their “117s” blew up with minimum abuse. So the LM117 sold well, because it could really do things that competitors could not do.
Here’s another quote from the Trains: “Blomberg’s truck design has been able to withstand the far greater demands imposed by today’s locomotives with their higher horsepower and increased tractive effort. It has been said that he was not as cost-conscious as he should have been, that his designs were heavier than necessary, and that he would not listen to others. Many people would gladly plead guilty to such criticisms if their designs could be as successful as Blomberg’s.” Ain’t that what Dobkin did with his LM117?
What else should a designer do? He must not just think of how to meet specs—although that’s important too. He/she must think like a customer (a user) and see what will really make them happy—and avoid things that would make a customer unhappy. You have to put on a marketing hat to see what features will appeal to the customer. You have to close your eyes and think—“how can I write a data sheet that will have sex appeal to engineers?” And if you can think of an advertisement, so much the better!
You have to be careful not to build in features that are excessively hard or expensive to make in production. You have to plan that any necessary test can actually be done without a lot of wasted time and expense.
Obviously, in every field—in styling a car, in decorating a room or a building, in designing a nine-ton two-axle truck to carry freight engines—you have to think about all of these facets. A good designer neglects none of these. Yeah, a truism. But it is true.
Recently, some outstanding engineers were described by the publication American Heritage of the Invention & Technology as “bold, self-reliant, independent, secure, powerful, daring, resolute, and sometimes, arrogant and overbearing.” So, what’s new?
All for now.
/ Comments invited!
RAP/Robert A. Pease/Engineer
Read more article from Bob Pease on Analog Vol. 1.
