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By Design News Staff -- Design News, June 18, 2001
High fives (or 101s!)
I just got done reading your editorial on slowing down speeders (DN 04.23.01). I have one thing to say: BRAVO!! I thought it was great! I'm a 31-year-old electrical engineer, and I thought about driving home at the average speed of 101,000 mph. I began to shudder. :)
Thank you for the laughs. It's nice to see that other technical types out there have a sense of humor.
Liberato Rizzi
Hardware Development Engineer
Schindler Elevator Corp.
Randolph, NJ
A matter of perception
In contrast to your adventure of driving a Fiat in Morocco, in early April I had the opportunity to drive on one of Germany's famous Autobahn highways. The German Autobahns compare with most divided 4 lane U.S. highways. In the open German countryside, if you drive along at 80 km/hr, you will soon see a large truck-tractor radiator in your mirror, and you will feel the sideways push from the displaced air from other cars going by at 150 km/hr.
In noting that my rental car speedometer scaled to 220 km/hr, I took an opportunity to follow a pair of passing cars. The two fellows quickly pulled away from me, each going well over 200 km/hr. I made no effort to keep up, settling down with the rest of the sparse automobile traffic at around a smooth 150 Km/hr. The keyword here is smooth. After a time at this speed, the excitement wears off.
After a midnight return landing at LAX, I picked up my American car, and drove down a nearly vacant, 6 lane 105 freeway at 65 miles-per-hour (104 km/hr). After the previous day of Autobahn driving, 65 seemed to be a slow crawl. You become accustomed to the higher German speeds very quickly.
The mind's perception of what is a safe speed is a factor of incoming stimuli. Driving at 50 km/hr on a rough Moroccan road, inside a noisy Fiat, with unbalanced tires, and 4 bad shock absorbing struts, seems much faster than driving a new mid-size sedan on smooth Autobahn at 200 km/hr. In your Fiat, your visual speed mixed with vibration and noise, makes for a lot of sensory stimulation adding to the speed sensation. Drive the same Fiat on a Baja Mexico dirt road, and 35km/hr is fast.
The Space Shuttle(s) orbit at incredible speed in vibration-less silence. The earth below appears to move along at a visible snail pace at over 35,000 km/hr. Would you have perceived the lowly Fiat as moving faster than the quiet smoothness of Low Earth Orbit? Of course you would have. If you closed your eyes in the Space Shuttle, you would not sense any motion unless a change occurred.
For a real shift in the driving paradigm, visit Japan or England, where you drive on the left side of the road. You will quickly forget all about speed the first time you enter a traffic circle.
Jon Lenhert
Senior Project Engineer
Too cool for comfort?
On page 102 of your 04.09.02 issue of Design News, I was amazed by the write-up on the vortex cooling system from Hoffman. The technology for the VCool system truly is not new; the devil is decades old. The energy waste of this unit has to be horrendous! A single compressed air horsepower costs 8 to 9 electrical horsepower. If an equipment purchase is truly evaluated via life cycle cost analysis, the real cost is identified with ever increasing electrical costs and the competitive business atmosphere, how can one even consider such a cooling device?
I stand to be corrected and welcome enlightenment.
B. R. Howard
Thiokol Propulsion
Alcoa Industrial Components
Hoffman Product Manager Scott Hill responds:
We agree with Mr. Howard's comments:
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The technology has been around some time (we said so in the article)
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Comparatively speaking, the vortex cooler is less efficient than a conventional "air to air" refrigeration unit.
Bruce is correct. The vortex cooler operation costs could be as much as 7-8 times as great as a conventional system. That "inefficiency" argument is also the reason why the market price for the Vortex cooler is approximately 40 to 50% less than that of a conventional refrigeration unit. Without a doubt, even though the vortex has a lower initial cost, when you compare total cost (including operation) the conventional refrigeration unit is less expensive (due to its efficiency). The vortex cooler's strength is that it can operate in nasty environments (high temperatures, extremely dirty/oily) and with its small footprint, it can be mounted to a small enclosure. In certain applications that require these performance attributes, the lower efficiency of the vortex cooler is an acceptable trade-off.
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