A Tale of Two Handles

A little 'technical' bit about handles.

What happens if you turn the handle faster?  I’ve been asked.

Yes the music does play faster but only up to a point. 

Turning the handle does two things.

      Firstly, it turns the crankshaft at the same speed as your turning….it’s on the same shaft….no gearing. So twice as fast.. twice the volume of air. Now as we do not need all this air, the ‘spill-valve’ valve or “over-blow” valve will just release it to atmosphere.

      The second function of the handle is to drive the spool pulling the paper off it’s roll and across the tracker-bar. Now turning faster moves the paper faster but the small pneumatic motors or “puffs” cannot inflate and deflate quick enough to separate out the individual notes.

These small organs are designed for a paper speed across the tracker-bar holes of between 2 ½” to 2 ¾” per second. (65mm to 70mm). I arrange all my music to play at a speed of 70mm per sec.

There is a reduction drive between the handle shaft and the drive-spool shaft, adjusted to get the correct balance between the paper speed and the volume of air required.

In the above photo you can see the 1" wheel on the right driving the (black) idle wheel.

This can be lowered by the snail-cam above it, to separate the drive on rewind (ie clutch).

The large left-hand wheel is on the take-up spool shaft.

As the air requirement can vary from organ to organ, this 'gearing' is arrived at by trial.

On the opposite side of the organ to the crank handle is the smaller rewind handle.

This also requires a clutch to disengage the rewind when playing 'forwards.

There is also speed change, but this time the ratio is to speed up the turning so that we can rewind music twice as fast a we can play it (fast rewind).

On this side I have used a belt drive between the two wheels. The clutch is activated by pulling out the knob, just to the left of the small handle.

The other small knob to the upper right, is for fine adjustment to align the tracker-bar holes to the holes in the paper roll if necessary.