Keeping Displacement Cables Extended

Position Measurement & Control - Issue 42

PRODUCT FOCUS

Keeping Displacement Cables Extended

Fancy Braking Mechanisms Need Not Apply!

It's a dilemma that might even confound TV inventor/action hero MacGyver: how does one prevent a Firstmark Controls position transducer's extended cable from automatically retracting during installation? Firstmark Controls has no preferred method of preventing cable retraction but we can pass along some of our customer's creative recommendations on generating interference jams to keep displacement cables extended.

Figure A1 - Some users apply toothpicks and fishing weights to prevent displacement cable retraction during position transducer installations.

Our users noted that for any material to successfully cause an interference jam at the exit hole, it's best to be durable and pliable. Brittle materials tend to break upon cable retraction. Hard materials tend to damage the fine steel displacement cable wire strands.

One user found that all it took was the end of a wooden toothpick (we assume an unused one) to safely jam the exit hole with the cable extended. The retraction cable tension automatically held the peg in place, and the jam cleared when a slight cable extension set the peg free.

Another user went fishing for his idea: he used several crimpable fishing weights (sinkers) to create the jam. As these users demonstrated, there's no hard-and-fast rule for inventing solutions as long as the jamming material is durable enough to resist breaking and generates enough friction to eliminate slippage. Remember, Firstmark Controls does not recommend any particular method so make safety your #1 priority when experimenting with this subject.

APPLICATION FOCUS

Tough Enough for NASCAR

Even High-Impact NASCAR Crashes Can't Break Firstmark Controls Position Transducers

Imagine controlling several thousand pounds of steel, plastic, and vulcanized rubber, screaming along at 200 MPH over hot asphalt in a track built specifically for speed. Imagine taking that 600- horsepower engine hard around a turn, the smell of burnt rubber tingling your senses. Now, imagine all that crashing into a wall. During a recent NASCAR test run, this very situation occurred - with interesting results.

When a 3500-pound car slams into a wall at 200 MPH, not a lot survives. Obviously, the driver has the highest level of safety protecting him, and in this instance, the driver escaped without issue. The car, however, wasn't so lucky. The frame collapsed, the engine was mangled, the steering system was shattered, and an ensuring fire engulfed the engine compartment. Yet, to the amazement of the crew, one little mechanical device survived all that carnage.

Figure B1 - The Series 160 position transducer post-crash: not pretty, but still fully operational within calibration!

Figure B2 - Beauty and the beast: the Series 160 position transducer shown post-crash in its mounting location.

Through the debris and twisted metal of the car's burning remains, the Firstmark Controls position transducer monitoring throttle position was still in tact. It was nearly the only salvageable piece of equipment from the entire vehicle.

Firstmark Controls position transducers have been long known for their durability. We never had the chance, however, to put it in a test quite like this. Thanks to this unfortunate crash, we found out just how tough these little devices are. The next time your project needs a durable position transducer, give your favorite NASCAR crew a call. We think we'll know what they'll recommend.

TECHNICAL FOCUS

Even Elephants Need Position Transducers

Rose Parade Floats Come To Life Through The Magic of Firstmark Controls Position Transducers

Through the wonders of technology, not Disney-esque magic, Firstmark Controls and engineers from Cal Poly Pomona and Cal Poly San Luis Obispo brought cows, dinosaurs, skunks, gingerbread men, and seahorses to life. Over the past decade, Cal Poly engineers used Firstmark Controls position transducers on their annual Rose Parade float animals to give these constructed critters award-winning movement, and 2005 was no different. This year's Rose Parade saw Cal Poly's "EleFun Time!" elephant family riding bicycles and scooters down the parade trail.

To create the illusion of elephant family's leisurely ride, the Cal Poly students used Firstmark Controls position transducers to mimic a variety of movements. Parade viewers saw the parent elephants tilting back and forth on a tandem bicycle while the child elephant pushed for speed by kicking out from his scooter. These seemingly simple movements required the student designers to devise control mechanisms and motion control software for each and every motion.

Figure C1 - Cable extension position transducers offer ease of installation and size advantages for the unusual requirements of electromechanical animation.

Figure C2 - Most elephants are known for their memories. These ones are known for the flexible Firstmark Controls displacement sensors that guide their motion.

Attaching cable extension position transducers to the parent elephants' heads created side-to-side tilting of the parents' tandem bicycle. The scooter elephant had two position transducers: one Series 174 on the head for side-to-side tilting, and one Series 160 on the leg to simulate a kicking motion. Inside the float, an animation computer communicated with the transducers to control each elephant's motion.

Just as quickly as they came down the parade route, the elephants disappeared into Rose Parade memory, but what's next? The 2006 Rose Parade is just a few months away, and you can bet that Cal Poly students will be using some Firstmark Controls pixie dust (also known as position transducers) to bring mechanical structures to life.

ISSN 1527-5108 • Document Number S050AB(050922)