Electronic Design

Bob's Mailbox

Note: When I was on the road, a guy told me about some special software called "CP COOL" that's supposed to significantly slow down your CP clock when you're just typing, and thus considerably prolong a laptop's battery life. I tried searching for this on the Web, as the guy suggested. But for some reason, it wouldn't show up for me. Can anybody tell me where to find this? I'll let you know if it's any good.

Hello Mr. Pease:
Not so long ago I realized the reason why my shoelaces got loose so often. I have used something like a "granny slip knot" to tie them. Afterwards, I noticed that this was the case with those of my friends who had the same "problem." Even though I am now very familiar with all kinds of knots used, like in maritime traditions, it seems hard to recognize some bad habits that I learned 40 years ago. Thank you for your interesting articles.
Hannu Mikkola
via e-mail

I don't think the "slip granny" is your problem. Usually, I'm careful to tie my shoelaces with a slip reef knot, and careful to not use a slip granny. But recently, I tried a "slip granny," and it doesn't flop apart all day. So I think the knot isn't the problem.

Rather, your shoelaces don't like to stay tied—they're too slippery, and hard or stiff. It's like comparing nylon or polypropylene rope to cotton or hemp. Some ropes and some cords just do not like to stay tied, no matter the strength of the rope. Old cotton and hemp do like to stay tied. Try some cotton laces, and you'll see the untying problem go away. Let me know how this experiment works out! If you buy nice cotton laces, they will probably stay tied much better than those that came with your shoes. I often throw away (or retire) the laces of a new pair of shoes if they refuse to stay tied.—RAP

Hi Bob:
Concerning the recent Bob's Mailbox (Electronic Design, March 19, p. 136), what's the fuss about hybrid vehicles? This isn't new earth-shattering technology. Railroads have been successfully using hybrid diesel/electric traction systems for many decades.
Ira A. Wilner
via e-mail

Ira, these are new hybrid cars of types not seen much before. Some of the time they run on batteries, sometimes on gas engines, and sometimes they run on both. Diesel-electrics have been around for a long time, but they're not "hybrid" in that sense, as they never run on batteries alone!—RAP

Bob:
I didn't read "What's All This Knot Stuff, Anyhow?" (Electronic Design, March 5, p. 142), but I saw the feedback on it in "Bob's Mailbox" (Electronic Design, May 21, p. 99). Let me add this account to Why It's Important to Stand Away from Taut Cable. I'm talking about taut steel here.

From 1969 through 1973, I worked as a radio engineer at WWJ in Detroit. The guy there who got me the job was a great big hulk, sometimes referred to as a "human crane.'' One day he recounted for me how, always having been big for his age, he could successfully lie about his age. Thus at 16, he was able to attain a job on the Detroit waterfront, unloading coal barges. Each day with a lunch packed in a bag, his mother drove him down to the dock, where the coal barge would be moored. To unload the barge evenly, it was winched back and forth by pulling or releasing steel cables from each end, so that the appropriate hatch would be brought to the unloading machinery. This required coordination of the two winch operators, one at each end of the barge.

One day when he arrived, the unloading activity had been suspended and there was a commotion on the dock. He quickly found out that the winch operators had crossed their signals, each winching his end in until one of the steel cables snapped and whipped down the dock. As he approached, they were just hosing down the area where the recoiling flying cable had cut a man in two and killed him.

I can't remember just what stimulated big Jim's recall of this incident on that particular day. A few of us in the radio studio were sailors and we probably were talking about winching in sheets, halyards, and cable tensions in strong wind. I will never forget that story.
Frank Laperriere
via e-mail

I doubt if I can forget it either, and I wasn't even there! Best regards.—RAP

Dear Bob:
Your note about air conditioner thermostat efficacy and system gain brought this to mind: when the new wing was built for our labs (~1981), there was great difficulty in getting the HVAC system to stabilize. It was cold outside, the building was very cold in the mornings, and the heat would cycle wildly. Several attempts to fix or patch the system failed. Finally, the problem was found. This advanced HVAC system had an outdoor temperature sensor, which was used as an "anticipator" circuit to start the furnaces early on cold mornings. The outdoor sensor had been carefully installed inside the building! Once the sensor was moved outside, we had warm, stable (temperature-wise, anyway) offices.
Ken Welles
via e-mail

Lovely!!! Hilarious! A tiny error like that can screw you up for months!—RAP

All for now. / Comments invited!
RAP / Robert A. Pease / Engineer
[email protected]—or:

Mail Stop D2597A
National Semiconductor
P.O. Box 58090
Santa Clara, CA 95052-8090

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