Hints & Tips № 4 — the Power of String

“It’s a great asset to be able to play a musical instrument” my parents used to say to me as I wrestled with my violin as a small boy. The violin beat me at wrestling, so I concentrated more on Meccano as a result.

One Meccano problem I had as youngster was with using pulleys. I could never get the darned tension of the string between one pulley and another just right to transmit any usable power. String too loose — belt slip, too tight — binding bearings. I was unaware of the existence of Meccano rubber drive bands, which would have been too short for most of my ambitious schemes anyway, and the string I was trying to use was thick stuff (unravelled Army Surplus socks, no doubt), which didn’t help.

After being born again, Meccano-wise, I came up against this problem again when making models requiring simple transmission systems with changes in direction, so I had to apply my adult (?) brain to the problem. Which is where the violin comes in. I still had it, and remembered that in its dusty case was a block of violin bow rosin. Applying this by rubbing it along the string (genuine Meccano green, of course), gives ample grip, even when it’s quite slack.

So, if you are after a simple, adjustable way of transmitting power, consider pulleys and string, using rosin to give grip — if you can get it from your local music shop. If not, I wonder if the powdered version used by your ballet-mad daughter on her points, or by your weight-lifting son for his presses and jerks (who are these people? — Editor) might also work. Let me know. Other possibilities include lathe belt grease (messy?) or ‘rubberising’ the string using Copydex. Any volunteers to try it?

A more technical solution of course is to use an idler wheel to tension the string. If this can be applied and released at will by a lever it will serve as a clutch — useful, for example for transmitting power from a steam engine, to maintain high revs.

Me, I like the smell of the rosin. And it works.

So my parents were right.

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