Motion System Design

Sometimes the old way is the best way

The many new products and tools make it easy to overshoot the mountain

Some engineers strive to always use the newest and greatest technologies. Doing otherwise, they feel, will indicate they’re behind the times. If this is their credo, they stand a good chance of selecting the wrong product or tool to do the job.

Case in point: A salesman was presenting the features of his latest Whiz-Bang. Equally important to him was his new Super- Dandy Laptop Computer with the famous 796 chip and six whistles. He sat down by his “fabulous” presentation tool and invited us to gather around to view the presentation. Even with the room lights dimmed, it was difficult, at best, for more than two of the five attendees to see the screen at any one time. Plus, all five of us had less than perfect eyesight. Three wore bifocals. You know how those limit close-range vision.

The longer the salesman went on, the more negative points he earned. He simply selected the wrong presentation tool (although one of the newest) to convey his message. Had he made copies of his visuals and used them as flip charts — or even used a large pad of paper and a big marker — he would have made several sales. But he didn’t. Moreover, he wasn’t aware of the situation, because he was so enamored with his Super-Dandy.

By contrast, we attended a conference where the presenter used a similar computer, but it was connected to a transparent LCD panel that was placed on an overhead projector. Bingo! Ten people saw each and every visual with all the glitz and glitter the computer program delivered. This combination of the new with the old was a winner.

Of course, we have all heard many cases where 3 X 5 cards are beetter suited — offer faster information retrieval, easier to carry, etc. — for some applications than a computer.

In the plant, a fluid coupling may produce the required motion better than a precision servo system. A high-slip (NEMA Design D) ac motor often delivers the needed machine characteristics more economically than an adjustablespeed drive. Although it seems strange, wood bearings are better suited for some applications than the best rolling element bearings available.

Moving outside, the On Site Marine Co. built a 1,000-ton showboat, Branson Belle, for Kenny Rogers on the shore of Table Rock Lake. Located near Branson, Mo., this lake is landlocked so the sternwheeler had to be constructed at the lake. The first part of the construction was done onshore. One of the challenges was selecting the best lubricant to be used between the steel rails and the wood beams when the nearly completed boat was launched into the lake. One approach was to use grease — 55 gallons of it. However, this would require solving some environmental issues. Instead, the marine engineers reverted to the lubricant of choice for the ancient Egyptians — environmentally friendly bananas. Interestingly, bananas are slicker than grease. Result: successful launch without a massive cleanup job.

As our bag of motion system components and design tools keeps growing, it is more important now than ever to select the right product or tool for the job. Being trendy just for the sake of being trendy can be counterproductive, especially if the user doesn’t understand the new device. Does this advocate forgetting the new technologies? Of course not. Good engineering involves evaluating all the approaches, old and new.

— Phil Kingsley
[email protected]

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