Edison Home phono--missing pinion

[jboger]

I recently bought a rather dilapidated-looking Edison Home Phonograph. I thought the mainspring was busted but turns out the motor is missing a pinion. The pinion slides on over the arbor, then one tightens down on a screw. The wheel is there, just the pinion is missing. I believe with this pinion, the motor will run again and the machine give new life to old cylinders.

I don't know which pinion this is, 2nd pinion or some other. I included a picture of the overall motor, so you can see what model this is. Then there is a close-up of the motor. I drew a circle where the missing pinion should go. If more photos are required, I can add them.

Thanks for any help.

John

[MisterOpera]

That is called the 19 tooth gear. They are know to break. It is a safety gear, that, if it goes, it can be replaced. I am sure Brian (formerly Sitko) has them I have replaced quite a few of them. Ron's had an extended shaft with a screw to hold it to the shaft.
Good luck!
Burdette

[jboger]

Burdette:

Thanks. Now I understand. This pinion is a safety pinion and is placed just downstream from the mainspring. If the mainspring breaks, then the pinion also breaks and protects the rest of the train. You know, a pocket watch has a similar feature, also a safety pinion, which is reverse threaded. If the mainspring breaks, this pinion loosens and stops the power from being transmitted through the rest of the train. Without the safety pinion, a sudden burst of power could do serious damage.

Again thanks. I checked with Brian (The Phonograph Shop) and he has the part. I thought I had a busted mainspring--maybe still do--but I might get lucky. This pinion is a third of the price of a new mainspring.

John

[Dave D]

When installing one of these with the set screw, it's a good idea to file a small flat spot on shaft for the screw to tighten down on.
Dave D

[JerryVan]

The original gear was brass. Like all old brass that's under stress, they age harden and crack open, allowing them to spin freely on the shaft. Not sure how that makes them a "safety gear".... Seems they'd be safer if they didn't break. Anyway, you got some good advice on the replacement.

[jboger]

Now with the pinion in place. Motor runs.

Jerry: If the pinion was designed to break under excessive force, then I would consider this a safety pinion, analogous to that on a watch. Where would the excessive force come from? Possibly from the sudden release of power when the mainspring breaks. That power could lead to a rapid acceleration of gears that might lead to a stripped gear downstream from the mainspring. Either that or a broken pivot. You would want to place such a safety pinion up close to the mainspring--which is where this pinion is--in order to protect the train. Whether Edison actually designed this pinion to break under excessive stress, I don't really know. But it would make sense if Edison did.

John

[JerryVan]

Now with the pinion in place. Motor runs.

Jerry: If the pinion was designed to break under excessive force, then I would consider this a safety pinion, analogous to that on a watch. Where would the excessive force come from? Possibly from the sudden release of power when the mainspring breaks. That power could lead to a rapid acceleration of gears that might lead to a stripped gear downstream from the mainspring. Either that or a broken pivot. You would want to place such a safety pinion up close to the mainspring--which is where this pinion is--in order to protect the train. Whether Edison actually designed this pinion to break under excessive stress, I don't really know. But it would make sense if Edison did.

John

I have never seen a broken gear of this type in a motor with a broken spring. Obviously, you have! Not saying a broken spring would be kind to that gear, but then a gear fracturing, causing the sudden release of the spring, could indeed cause the spring to break. Either way, you're up & running, so good news!