Recently drive systems - belts and chains - were being discussed.
I'm becoming increasingly excited by the properties and possibilities
of flat drive belts.
So, FWIW:
Flat drive belt systems simply need enough grip on the pulleys not to
slip, and then they're almost 99% efficient through most of the power
range - better than any other type. Wikipedia says that with 'modern
materials', thin flat drive belts operate with reasonable belt
tension and transfer up to 100 HP per inch of width. (Larger pulleys
obviously will have more grip on the belt than small ones.)
I've been searching, rather fruitlessly, for satisfactory "modern"
flat drive belts. It has just occurred to me that the black
polypropylene strapping one buys off rolls in various widths at, eg,
fabric shops, is very strong with little stretch (like the yellow PP
ropes), flexible enough to go around the smallest pulley virtually
without friction, and cheap. (How about a 1" x 40" drive belt for
1$?) If the PP cloth has insufficient 'grip' without excessive
tension, it can probably be increased by spraying it with urethane,
or maybe some sort of rubbery material. (Urethane flat belts are
relatively common as flat belts go, but are elastic. Urethane paint
spray cans are common.)
The ends could be melted, glued or sewn together to form a continuous
drive belt.
Flat drive belts auto-center on slightly "barrel" or "egg" shaped
pulleys, always running towards the highest spot. I'm making ABS
pulleys for 1" flat belts on my 3D printer, but may start molding
them from (what else?) PP-epoxy composite to get bigger ones than I
can print (~7" O.D.) - which will also be very tough and strong. (A
sanded plastic pulley has more grip than a metal one and causes
little belt wear - I'm sure it's part of the key to using flat belts.)
And a clutch or (spring tensioner) can easily be made with an idler
pulley on a spring, pressing on the outside of the belt.
Finally on a rather unpleasant safety note, I would think that a hand
caught in a flat belt and dragged through a pulley with no sides
would probably emerge much less mangled than with a V-belt, toothed
belt or a chain drive. (Especially if it's one that's tensioned with
a spring.) (I mention this point as I've seen but thankfully not
experienced savage accident results with both V-belt and chain drives
in people I've known.)
Cheers,
Craig
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