Rotary Valves - their care

This excellent article was written by Mr. Robert Osmun*  several years ago.

"Rotary valves are mechanical devices and need to be treated as such.  Many people seem to think that their valves require no attention at all.  Others have been given information that is just plain wrong, such as the notion that water normally present in the horn adequate lubrication.  Surely no manufacturer of cars would honor a warranty on a car that had never had any oil put into it.  Why then should a player complain about the valve action of a horn that hasn’t been oiled for a year or so?  Proper valve maintenance is essential to preserve the playing quality and valve action of the horn.  The following procedures will help prolong the life of your valves and ensure the fastest and smoothest action.

The two enemies of rotary valves are friction and corrosion.  The mechanical wear on the rotor bearings increases tolerances, causes noise (clicks), and in time allows the face of the rotor to come into contact with the casings, increasing wear greatly and causing a poor air seal.

Corrosion is perhaps the greater problem.  The breath contains elements which chemically attack the interior of the instrument in a process called de-zincifaction.  De-zincifacation is the removal of zinc from the brass to leave behind a red colored porous layer of copper.    The valve face suffers from both piting or dezincification and copper carbonate buildup.  Copper carbonate is hard and rough.  As is builds up, it increases wear on the valve casing and causes a rough feel and a poor air seal.  In the worst cases, (such as poorly maintained French Horns in schools), the valve will eventually freeze up.   Acid dipping in this case will remove the carbonate deposit, but only valve replacement will solve the pitting problem.   

Prevention of this problem is possible by using certain kinds of valve oils. 

To oil string action rotary valves two kinds of oil are needed.  A light valve oil like ROTOR, and a heavier oil for the bearings. For the bearings we recommend Sears Household Oil or Singer Sewing Machine Oil. Do not use 3-in-1. It contains paraffin, which will gum up.  Oil your valves using the following procedure:

1. Take off the valve caps.  Put a drop of Singer oil (or equivalent) on the end of each rotor shaft where it shows through the bearing-plate.  Without depressing the valves, pull the F slides about halfway out.  This creates suction which pulls the oil into the bearing surfaces.  Then work the valves to distribute the oil, return the slides to their original positions, and replace the valve caps.

2. Turn the horn over.  Put a drop of Singer oil into space between the stop arms and the valve casings.  This time pull the Bb slides without depressing the valves. Work the valves to distribute the oil and return the slides to their original positions.

3.  Pull out the 1st, F and Bd slides and put several drops of ROTOR into each.  Holding the slides vertically, insert them all the way into the horn ( so as not to get oil onto the slide tubes).  Turn the horn over and rock it back and forth while working the valves.  Also pour several drops into the mouthpipe and blow it through the horn.  Finally, drain the oil just as you would water. The main purpose of the ROTOR oil is to shield the rotors from the corrosion effects of the breath. ROTOR accomplishes this through a special corrosion passivator.

The procedure outlined here should be done on a regular,  weekly basis.  In addition,  the lever rods and the springs should be oiled with Singer oil once a month.  If your horn has mechanical linkages,  these should be oiled twice a month with SAE 90 gear oil  (available from auto parts stores).

If these steps are followed on a regular basis you can count on a long and trouble free life for your valves. "

*Osmun Brass 
    #5 Forest Street 

    Arlington, MA 02472
    800-223-7846
   www.osmun.com

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