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Phonograph Motor Basics

This particular motor came out of a very early Sonora Phonograph (c. 1910). It's design is typical of the Swiss motors found in most mechanical Sonora phonographs. The frame is in two parts and is made from cast iron. The posts are part of the upper casting. The small "U" shaped projection on the upper casting is the pivot point for the speed regulator arm. This motor obviously hasn't been touched and is in the exact condition in which it was found. 


Figure 1

1. Spring Barrels.

The springs are really the heart of the motor. This motor has two barrels. The springs are connected by a center shaft that passes through bot barrels with the bearing ends located in the upper and lower castings.

Multiple springs proved more efficient that single springs. Some motors have as many as four or more springs.

Figure 1
Motor - Front View

Figure 2

1. Pawl; 2. Ratchet Gear; 3. Spindle. 

The pawl and ratchet gear are what allows the springs to remained wound. This is also where the crank attaches to wind the springs.  The pawl is held by a spring that forces it into the teeth of the rachet gear. This allows the motor to be wound and also prevents it from unwinding.

Figure 2
Side View

Figure 3

1. Worm Gear; 2. Governor End Bearing; 3. Spindle Shaft; 4. Governor Disc; 5. Governor Weight; 6. Governor Spring.

This is the governor assembly. This is what regulates the speed of the turntable. The process is quite simple.

Energy from the springs is transmitted by the gearing to spur gear at the bottom of the spindle shaft. As the spindle attempts to wind, the helical gear caused the governor to rotate. When the governor shaft rotates, centrifugal force caused the weights to move outwards. This in turn caused the disc-weight assembly to shorten as a result. At this point, the disc is prevented from moving to the right by a leather or felt pad at the end of the speed regulator arm.  This keeps the speed at which the governor rotates from increasing beyond the specified setting.

There are two end bearings (#2) that permit the proper positioning of the governor in relation to the helical gear on the spindle. This is accomplished by rotating the governor end bearings which have eccentric holes for the pin bearings.

Figure 3
Governor Assembly

Figure 4

This is a close up of the worm gear. Original owner's manuals for Sonora Phonographs recommend putting a dab of petroleum jelly on the worm for lubrication and to keep the gear pair quiet (see lubrication notes at the bottom of this page.

Figure 4
Governor Assembly - close up

Figure 5

1. Spindle Shaft Bearing Cap; Spring Barrel Shaft End; 3. Gear Shaft End and Bearing; 4. Plate to Pillar Screw; 5; Ratchet and Pawl Assembly; 6. Lower Spring Barrel

Most of this is redundant, but it is worth noting #1, the Spindle Shaft Bearing Cap. This is an interesting little item in an arcane sort of way. The lower end of the Spindle Shaft has a small ball bearing mounted in it. The bearing cap has a small disc of metal upon which the spindle rotates. The screws to either side hold the cap in place. This is an important lubrication point and will be covered in the lubrication notes at the end of the page.

Figure 5
Bottom View with Maker's Mark (note hand written inspectors number)

Lubrication Notes.

All gearshaft end bearings should be lubricated with a light machine oil. I recommend using a 'sewing machine' type oil as opposed to a heaver general purpose lubricating oil. The lighter oil penetrates a bit better. When I say 'well lubricated' I mean just enough oil to do the job. I say this because oil is a dust magnet and you don't want dust accumulating where it can act as an abrasive. Adherence to firearms lubrication techniques is a good idea where metal-to-metal contact in involved (this is the "enough but not too much" rule).  More about this when I talk about gears.

The end shafts of the governor and the leather pad that rides the governor disc should also be lubricated with oil.

Gear teeth should be lubricated, but there's four schools of thought about this point:

1. The first school of thought says that you should use grease (like white lithium grease, gear grease or petroleum) and not oil- this is the school of thought I adhere to on this particular subject if the gears are sufficiently noisy and need some quieting down.

2. The second school of though involve using oil on gear mating surfaces. I do not recommend oil for lubricating gear teeth because, as I said before, oil is a dust magnet. Dust will eat up the mating surfaces of gears. Grease is better at isolating airborne dust and moving it away from the mating surfaces.

3. The third school of thought (an on which I also recommend if your gears are in especially good condition and gear noise is not a problem) involves using a dry silicon lubricating spray.

4. The fourth school of thought (and a fairly spooky one at that) involves using no lubrication at all on gear mating surfaces. There is a method to this madness but don't try this at home, folks. I don't recommend this last school of thought at all.

be sure to oil the bearing surfaces of the pawl and ratchet and grease the ratchet gear while your at it.

On an interesting side note, if you closely examine the gears teeth on a well-used phonograph motor, you will find that when brass gears mate with steel gears, the steel gears tend to wear out first. There's a reason for this: when grit is involved where brass and steel meet, the grit tends to get embedded in the softer brass. When this happens, it acts like sandpaper on the steel gear and wears the daylights out of it. Again, grease doesn't attract airborne dust like oil tends to.

The spindle gear - the bottom cap should be removed every once in a while and cleaned with a solvent along with the bearing end and re-greased with a good gear grease or white lithium grease. You also want to put a drop of oil on the bearing end where it passes through the casting. At the top side of the spindle bearing there is usually a felt dust seal. Put a drop or two of oil on that. You also want to put a drop of oil on the top bearing (where the spindle passes through the casting). Always use grease in the cap-end of the spindle bearing - lots of it.

Worm Gear - put a liberal slathering of petroleum jelly on the worm gear. It keeps it lubricated, quiet and happy.

Some brands of phonographs used 'fibre' gears ('non-metallic', as a general description). Avoid getting grease and oil on any pair of gears that involve a 'fibre' gear. It tends to damage the fibre gears.

Springs - if they thump and bump, carefully and gently wind your machine up full and let it play down a couple of times. If this doesn't cure the problem, then you have to open up the spring barrels and add some petroleum jelly (you can mix in about 10% by volume No. 2 graphite). Word of caution! If you don't know how to work with springs, send the motor off to a phonograph repair service or have someone do it who has done this type of work before. You can get hurt badly if a spring lets loose. I'm talking really nasty hurt bad. Just ask around with phonograph collectors and listen to the horror stories.

Frequency of lubrication.

If you play your machine a lot like I do (about an hour or more each day on average) you might want to do your lube routine on the motor about once a month where oil is used. On parts that you use grease, just check to see that the grease is in good shape - you don't need too much, just enough to lube the gears. If you use spay silicon lube, then spray away to your heart's content on the gear teeth.

Be sure to carefully wipe off any excess oil or spent grease with a lint free cloth (lint is very abrasive, by the way). If you even suspect that there is any grit crunching around, have the motor cleaned and re-lubricated.

And I'm not joking about springs.

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