The Talking Machine Forum — For All Antique Phonographs & Recordings

Guys, please help me. I am working on my Graphophone AT, completing the motor.

Does the crank turn while playing?

I am thoroughly confused!

Many thanks!

Yes, the crank turns while playing, as the mainsprings unwind. That's why Columbia provided a "fall-off" type crank for this model.

George P.

phonogfp wrote:Yes, the crank turns while playing, as the mainsprings unwind. That's why Columbia provided a "fall-off" type crank for this model.

George P.

That's another question: why didn't they just leave the crank to unwind without falling off?

Bill

Lucius1958 wrote:

phonogfp wrote:Yes, the crank turns while playing, as the mainsprings unwind. That's why Columbia provided a "fall-off" type crank for this model.

George P.

That's another question: why didn't they just leave the crank to unwind without falling off?

Bill

My guess is that because the crank shaft is horizontal, a large portion of the rotation would involve resistance caused by the weight of the crank arm. This and the additional driving force as the weight has the opposite effect as it uses it’s weight to help drive the motor on the way back down could rob power on the upstroke, increase power on the downstroke and stress the drivetrain during the transition between the up and downstrokes. The main purpose was probably to prevent the loss of power on the upstroke.

The loss of power on the upstroke is a good point, but my simple mind is drawn to the possibility of a rigid crank stopping at the 12:00 position and posing a hazard to removing the cylinder. I don't know...

George P.

With disc models the fall off crank would fall before it interfered with a large record. Jerry B.