ABOUT THE FLOATING BALANCE
by Tinker Dwight
by Tinker Dwight
Names of the parts:
In general, the size of the swing of a balance wheel has nothing to do with the rate. A short swing will take as much time as a long swing.
Now for the "gotcha": A weak drive (low power) will cause it to run fast by shortening its swing. This is caused by a failure to get pallet lock on every swing. I'll try to describe this.
If you look at the escape wheel, you'll see two surfaces of each tooth. There are radial sides ( the lock surface ) and a ramped tip ( the impulse face ). On the lever arm that works the balance wheel, there as two pallet pins that follow the escape wheel. On every swing, a pin lands on a radial side of the tooth a certain distance in from the tip of the tooth: this distance is called lock. A momentary lock on each swing is necessary for the clock to run right. Following lock, the pin slides off the slanted face, receiving its impulse.
But if the balance wheel is not swinging enough, the pallet pin will land on the impulse face of the tooth instead of on the lock surface. When that happens, the tooth will be pushing against the direction of the balance wheel instead of going with it. This artificially shortens the swing, causing it to go back the other way prematurely, which makes the clock run faster.
This situation is almost always caused by a lack of enough power from the train to the escape wheel. But often someone will suspect the the balance itself is the problem and will fiddle with it trying to make it work better. It seldom does.
This means that once you've completed the rest of the repair, the bushings are replaced and the mainspring is lubed, you may have to undo the damage someone has done to the floating balance.
There are various things that can be wrong with a floating balance. Most are caused by someone fiddling with them.
1. It can be out of beat. With no tension on the lever arm from the escapement, the balance wheel roller pins (impulse pins) should be parallel to with the balance wheel's arbor (the wire the wheel floats on ) as seen straight into the clock. This is the first part of what is referred to as setting the beat on a floating balance.
2. The drop is the amount the escape wheel travels as each tooth is released. There must be the same amount of drop on each side. Carefully measure where the drop occurs by watching how far off center the top of the lever arm is when manually moving the lever arm from side to side.
3 .The lever arms fork should never touch any other part of the balance wheel except the roller pins (impulse pins) and then, only during the impulse.
4. The impulse pins that go inside the fork sit on a circular thing called the safety roller. It has a gap in it. One side of the fork has a prong sticking down, called the guard pin. As the balance swings one way, the guard pin will be inside the safety roller; as it swings the other way, it will be outside the safety roller. The guard pin should never touch the safety roller, as that will mess up the action.
5. The lever arm should be limited on travel by a couple of posts, called banking pins. These must limit the travel of the lever so that the guard pin doesn't drag on the spit ring safety roller. It must not limit the travel of the lever arm so much that it can not reach lock on the escape wheel as described earlier.
6. The amount of lock must be the same for both pallets.
7. The balance wheel should float easily up and down on the wire. Each end of the wire tube has a jeweled bushing in it. If the wire is worn, there will be a notch at the jeweled bushings. This can be detected by a slight catching when a light side pressure is applied and one tries to slide it up a little ( don't force it or you could damage the jewels ). It should move freely up and down ( float by the spring ). If it doesn't, it's time to replace the wire, and maybe the jewels.
8. Sometimes the helical spring will have been mishandled and bent to the side. This causes the entire assembly to hang at an angle and off center when not constrained by the wire. Being forced back to center by the wire causes excess friction between the wire and jewel. This can happen when mishandled during cleaning.
This is hard to test for without removing and replacing the wire. With the wire removed, the top of the tube should be close to the position it will be in when the wire is installed. It can often be seen as the spring not coiled uniformly around the tube but this is not always a sure indication of this problem. This is a very similar problem to a hair spring that doesn't center the pivots.
9. There should be no oil at the jewels on the floating balance. It is not recommended to use an ultasonic as it has been known to damage the spring.
10. Like a deadbeat, the escapement must lock on each pallet. Things that can cause failure are worn bushings on the escape wheel and lever arm. Also, the banking pins can be too tight or the fork hitting something else on the balance wheel other than the impulse pins.
I've purposely not described how to fix these problems as some interact. One has to look at all the possible problems and solutions before fiddling with any one thing.