Hi all,

this is maybe a question for the (elementary) math teachers here (or others who deal with rulers on a daily basis).

The Wikipedia article on the HP 35 mentions

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The HP-35 was exactly 5.8 inches long and 3.2 inches wide. This was the size of William Hewlett's pocket, hence "pocket calculator".

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HP museum confirms these dimensions here. Now the question: Can you buy rulers which will have tick marks at these distances? If not, any idea how these numbers were determined?

Cheers, Peter.

I guess I should wish all the people who can potentially answer this a nice 3 day weekend.

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Now the question: Can you buy rulers which will have tick marks at these distances? If not, any idea how these numbers were determined?

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You can readily buy engineering rulers which are triangular in cross section and a foot long, and have six different scales along the vertices (one along each side of each vertex): 10, 20, 30, 40, 50, and 60 divisions per inch.

So, measuring with 0.1 inch tick marks would have been no challenge, especially to a group of engineers in the 1970s.

"HOW" they actually did it, I've no idea! Probably measured Bill's shirt itself, with or without him in it.

They probably did it the same way engineers always get their data. They sent a surveyor to measure it for them.

It's difficult to use a ruler to measure a three dimensional object. Most mechanical engineers would use a micrometer:

http://en.wikipedia.org/wiki/Micrometer

These devices are usually accurate to .005 of an inch.

For operations such as part inspection or QC, yes. But a shirt pocket? I'd just reach for a ruler.

I have several rulers that are graduated in 1/10 and 1/50 inch increments.

Stefan

Yes, but...these were electrical engineers, and EEs do almost everything as a schematic without reference to actual dimensions :-)

Assume they have used a slide gauge. No problem to measure pocket with these.

I expected otherwise, but just checked and saw that BH's pocket was not governed by the golden ratio.

With some disappointment (and no math),
Andrés

PS: Somewhere I read a story in which Sony CEO Morita challenged his engineers to create the first Discman (portable CD player). According to the tale, Morita kept a wood block as a physical specification of what he wanted, avoiding tricks with the targeted size.

Edited: 1 Sept 2007, 4:11 p.m.

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According to the tale, Morita kept a wood block as a physical specification of what he wanted

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This trick was used for many a great design.

Walter Zapp used a wood block to determine the size for the first Minox camera. the wood block still exists and there is a photo of it in the book "Spy Camera, the Minox Story".

Jeff Hawkins used a similar method in developing the Palm Pilot. From the "The Next Small Thing" at Fastcompany.com:

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How small is small enough? His answer yielded the second principle: Small enough to fit in a shirt pocket. He paced the hallways at Palm headquarters, ruler in hand, measuring pocket sizes against small blocks of balsa wood.

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Original Link to Full Article: The Next Small Thing

Bill

Edited: 1 Sept 2007, 4:42 p.m.

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Assume they have used a slide gauge. No problem to measure pocket with these.

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Ths sounds logical. The ones I've seen however are all scaled in (1/2)^2" like this one.

However, I'll go to WalMart next possible opportunity and buy one of these rulers which Stefan V. mentioned. I should get some discount in the "back to school" department :-) Maybe they even have the nice ones with the little cats or ponies.

Cheers, Peter.

Sure is. I have an old 6-inch General ruler with 32nd and 64ths on one side and 10ths and 100ths on the other.

CHUCK

Edited: 2 Sept 2007, 1:19 a.m.

Even my cheap Chinese steel ruler from the stationary store I use at home has 1/10", 1/16", 1/20", 1/32", and 1/64" scales.

Dave.

At work I have one of these (851-012F) from Products Enineering:
http://www.productsengineering.com/tools/onlinecatalog/rules/roundendrules.html

1/10", 1/16", 1/20", 1/32", 1/50", and 1/100" scales.

Mine comes in a nice black though. Very thin and flexible, great for measuring shirt pockets. Calibrated at 20 degC.

Dave.