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Notes from Tony's desk Random thoughts from Tony Bryer

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Old 14th October 2010, 09:56 PM   #1
Tony Bryer
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Default On designing airships

In Neville Shute's autobiography 'Slide Rule' he writes about the design of the R100 airship (c.1930):

The forces and bending moments in the members could be calculated by the solution of a lengthy simultaneous equations containing up to seven unknown quantities; this work usually occupied two [human] calculators about a week using a Fuller slide rule and working in pairs to check for arithmetical mistakes.

Ah, the good old days. I went through university (1971-74) without ever seeing a computer. In my last year we used slide rules for our structural engineering calcs; the tutor owned an object of wonder, a calculator with trig functions. From memory it had cost him 400, several month's salary then. Five years later I owned my own computer and the long path to today's programs began - see the SuperBeam museum page http://www.superbeam.co.uk/museum.
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Old 3rd November 2010, 04:43 PM   #2
factory-fit
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Default Re: On designing airships

Strangely enough, I once used Prosteel to reduce a chore on an aircraft; this was the effect of drag on the wing, which is worked out with a simple aerodynamic formula.

As the wing tapered (it was a Rogallo Delta on my microlight, or 'flexwing') it was a chore to work out the distribution of drag loads along it.

I was able to use Prosteel to input each loads along a one metre length of 'leading edge' or beam, and find out the rearwards force as a Live load. This was the value that came out on a notional 'column', fixed at the point the drag was resisted by the Cross-boom, a bracing member inside the wing.

The chap examining the result didn't have the flexibility to handle this unconventional approach, and kept asking why the leading edge (an alloy tube) was shown as a 50x50 box section...

Cheers

Kev
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Old 3rd November 2010, 10:56 PM   #3
Tony Bryer
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Default Re: On designing airships

I'm not sure I want to know about this
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Old 15th January 2015, 10:43 AM   #4
factory-fit
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Default Re: On designing airships

Hi Tony

I'm actually Dyscalculic so Prosteel is invaluable, use it to work out end reactions by popping simple moments into a beam and reading off the results

It's quite handy for working out what bending happens to an airframe in a drop-test. Take a simple weightshift trike and work out what height it fell from and how much the suspension and tyre squishes, and you get the 'G' load on it, input the load positions and the keel bending is in the result. As the Young's Modulus is three times that of steel you can get a rough approximation of the amount the airframe bends.

This got results that had been missed by a Doctor in Aeronautics on a suspension design, great fun to do.
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