The Talking Machine Forum — For All Antique Phonographs & Recordings

How does one measure the amount of energy available to the spindle? Foot pounds, torque, is there a quick and easy way to measure this?

When a spring is wound up completely, it delivers the most amount of energy and that energy slowly decreases as the spring unwinds until it gets to a point that it will no longer drive the turntable with a reproducer playing a record. A weakened/aged spring will arrive at that point sooner, a new strong spring much later. (these are my observations/assumptions, not proven scientific fact)

In most multiple spring motors, the springs are installed in series, where they are connected as virtually a single spring. Example - a 2 spring motor with 2 17' springs provides roughly the same energy output as a 34' spring would. The initial energy measurement of this fully wound 2 spring motor would be the same as a fully wound single spring motor with 1 17' spring, but the energy loss would be twice as fast in the single spring motor. (again, my assumptions)

Late in the Brunswick phonograph spring motor development, they used a 4 spring motor with 2 double spring barrels. Each spring barrel connected the springs in series, but the spring barrels operated in parallel, with each independently and simultaneously providing power to the spindle. It seems this motor would provide twice the initial energy of a motor using the same 4 springs connected in series. (my assumption, again)

I would like to find a way to measure that energy to confirm my assumptions.

Any ideas?

Thanks! Cliff

Could you attach a torque wrench to the spindle?

You'd get a base torque reading though, meaning it wouldn't be factoring in the
momentum of a turntable that is already in motion.

Not sure if that helps.

CDBPDX wrote:Late in the Brunswick phonograph spring motor development, they used a 4 spring motor with 2 double spring barrels. Each spring barrel connected the springs in series, but the spring barrels operated in parallel, with each independently and simultaneously providing power to the spindle. It seems this motor would provide twice the initial energy of a motor using the same 4 springs connected in series. (my assumption, again)

That's not necessarily true, it depends also on the demultiplication of the gear ratio.

Could you attach a 6" bar to the spindle and hook a spring scale to the end of that?
I figured 6" bar as that's the radius of a typical turntable, I'm sure there is a physics formula to work back to the torque right at the spindle.

Hi,
The torque is force times distance of it's moment arm if you measure the force at 6 inches radius the torque is 6 inches times the force F and it's units are in inch-pounds, therefore, torque is 6F inch-pounds or force times ½ foot would give you the torque as 1/2F foot-pounds foot-pounds. Power is proportional to (torque)x(rpm) and energy stored is (average torque)x(rpm)x(running time). If more information is needed let me know. It does not matter where you measure the torque it is the same if you measured it at one inch the force would be 6 times as large as at 6 inches and therefore the force is 6F and the torque (or moment) arm is 1 inch the torque is still 6Fx1 or 6F inch-pounds.
Thank you all for all the information on the TMF,
Allen

Make yourself a prony brake out of wood with a small piece to tighten around the spindle as illustrated. Couple carriage bolts and thumbscrews to tighten just until the motor begins slowing. Use a digital or a small spring scale. This way you'll have a baseline to compare the motors and see which is stronger.
Here's the formula if you wanna get all technical onto it.
http://stirlingengineforum.com/viewtopic.php?t=1706

Marco Gilardetti wrote:

CDBPDX wrote:Late in the Brunswick phonograph spring motor development, they used a 4 spring motor with 2 double spring barrels. Each spring barrel connected the springs in series, but the spring barrels operated in parallel, with each independently and simultaneously providing power to the spindle. It seems this motor would provide twice the initial energy of a motor using the same 4 springs connected in series. (my assumption, again)

That's not necessarily true, it depends also on the demultiplication of the gear ratio.

The 2 spring barrels on this Brunswick motor connect to a worm geared drive shaft and that shaft drives the turntable spindle. It looks like about a 1:2 gear ratio from the drive spindle to the turntable spindle. Attached is a picture that shows this setup. Cliff

Panatropia wrote:Make yourself a prony brake out of wood with a small piece to tighten around the spindle as illustrated. Couple carriage bolts and thumbscrews to tighten just until the motor begins slowing. Use a digital or a small spring scale. This way you'll have a baseline to compare the motors and see which is stronger.
Here's the formula if you wanna get all technical onto it.
http://stirlingengineforum.com/viewtopic.php?t=1706

This setup measures 'mousepower' instead of 'horsepower'. Cool! Cliff