Metal tape with round or square holes in, engaging with balls or pegs set in pulleys. Firstly any generic name for this? I'm after design criteria, for steel tape, 1.25 or 1.5 inches wide, flexible enough to wrap around 1 foot diameter pulleys. So the trade-off between tape thickness , size and spacing of holes/sprockets for maximum tension/torque transfer and tape integrity.

That sounds like a prescription for fatigue failure, if I understand you correctly. A lot depends on how big the pulleys are and how long they're expected to last. Bandsaw blades are made to take it, but the wheel size has to be large enough to keep the flexing within bounds. Have you worked that into your design?

Perforated tape and sprocket pulleys?

Dec 23, 2017 22 Replies

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N_Cook 8 years ago

These machines were semi-custom made, the axial length of the plotter drum , varied for different sites with widely different tide ranges.

So custom made tapes along with custom-made plotter papers makes sense.

Especially as I'd not allowed for parallax in the lower view. Taking that into account, the width of tape cpmes out to 1.62 inches, perhaps 1

5/8 in wide. Spiggot spacing of 13/8 inches would not give 2 to 2.5 inch slip , but 13/16 spacing would. But then 43 spiggots to a pulley of 11.12 in diameter. Setting a dividing circle to 43? com[ared to step and repeat punching at any desired interval makes sense. So looks like non-standard holes pitch on the tape for sensible number of spiggots, ie that idea comes to a grinding halt, to zero in on the slippage value.

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Jim Wilkins 8 years ago

Presumably the band was cut from sheet stock of a commercial thickness. For such a low production count it would be hard to justify not buying standard components wherever possible.

(36" / pi) - 0.08" gives 11.38" for a diameter that would move the neutral plane of the band 36" per revolution. If the camera wasn't at the level of the wheel its apparent height would be foreshortened but the round drum's diameter wouldn't.

-jsw

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Jim Wilkins 8 years ago

I doubt that the perforated tape was a standard product. It could have been sheared to any desired width from a roll of shim stock,

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and the holes laid out with dividers.

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I could make one myself with hand tools.

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If the effective circumference is indeed 36" as I suspect then easy-to-generate pin counts give reasonable spacings within your estimated slip range; 1" or 2" for 36 pins and 2.25" for 16 pins. 2.5" gives 14.4 pins. 24 pins would jump by 1.5" or 3". I'd check if 16 or

18 fit the evidence.

-jsw

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