By Matt Walters (low brass specialist at Dillon Music, Inc. of Woodbridge, NJ)
So, the rotor valve on your trombone (French horn, or tuba) has become noisy. Perhaps the person sitting next to you brought this to your attention, and now it has been driving you crazy like a raspberry seed stuck in your tooth. Did you take off the valve cap, put some rotor oil in the center and screw the cap back on like you were told to do? Good. You should oil the bottom bearing point found under the valve cap on a regular basis (at least every two weeks). However, I doubt that alone made the noise go away. Most of the time the excess rotor valve noise is “ON THE OTHER SIDE”.
I’m constantly surprised how few people know that a drop of oil placed under the stop arm (the part that hits the bumpers) on the shaft of the rotor valve is VERY important for a quieter valve that works smoother and lasts longer. Just like that bottom bearing point that you know is under the valve cap, there is a second bearing point “ON THE OTHER SIDE”. Every time you operate a rotor valve via the linkage, there is a small amount of push-pull motion in conjunction with the obvious rotary motion. A poorly lubricated valve will prematurely wear the top bearing hole wider, which will lead to noisier valves and premature wear in the casing. At least every other week, you should put rotor oil under the stop arm right on the shaft of the rotor valve. Oil more often if it looks dry before two weeks go by.
While you are there “ON THE OTHER SIDE” oiling the rotor shaft with a drop of oil on that crack just under the stop arm, take a look at the bumpers in the strike plate. Work the trigger while you watch what happens when the stop arm hits the bumpers. If the strike plate moves, the screws holding it to the casing are loose. Gently tighten them and also check the big screw in the middle of the stop arm. If the bumpers have deteriorated so that the stop arm is now hitting the metal of the strike (bumper) plate, you now know why the valve is making too much noise. A more subtle, loud noise is heard when the rubber bumper material gets hard with age. Has it been a couple of years since the horn was last serviced? Bumper material that is either worn down or too hard with age needs to be replaced. In the case of old worn bumpers, you may prefer to take it to the repair shop, as the average musician is not likely to have the correct material on hand. There are plenty of other articles about servicing rotor valves if you are so inclined to replace the bumper material yourself.
The linkage is the final excess noise causing item “ON THE OTHER SIDE” that I want to help you with. I have a saying when it comes to rotor valves; “IF IT MOVES, OIL IT.” When you push or pull the trigger, you move at least one hinge point. Often, this is where the lever spring is. That spiral wound spring is typically wrapped around a hollow tube that has a hinge pin going through it. Put a drop of rotor oil on each end of the spring so it can work its way in to coat the hinge pin. Depending on the exact model of horn you have, there may also be a linkage between the lever and the stop arm. If there are moving parts there, OIL them. Also, make sure the attaching screws are snug.
You can keep quieter and longer lasting rotor valves if you don’t forget to oil every moving thing “ON THE OTHER SIDE” too.