Correct treatment of rotary valves will ensure the precision and the longevity of your instrument. Like all mechanical objects, the key to their success is adequate and regular lubrication. This ensures they run smooth, helps to reduce wear and keeps them running more reliably.
There are several points of lubrication to consider.
The most important place to oil regularly are the two bearing points. Seen below are where these points are located. A rotary valve is supported and actuates on these two points therefore it is the most critical area to keep oiled.
I prefer to use Hetman’s range of lubricants. The viscosity of the oil largely depends on the age and condition of the instrument. Bearing Oil No 13 works well for instruments that are under 5 years old, and I might use 13.5 for older instruments or bearings that are more loose. Rotor bearing oil is more viscous than just standard valve oil or rotor oil. 1 to 2 drops of oil every week is suffice for these points. Regular lubrication is key.
There are several reasons to drop oil down the slides.
- Slow/sluggish rotors
- Rotors that become seized
- Protection against oxidisation*
When rotors become so slow or sluggish to the point it is affecting the playability, drip some rotor oil (Hetman no. 11, 11.5 or 12 for example) directly onto the surface of the rotor. To do this, you remove the slides and use the needle applicator to apply oil directly to the walls of the rotor. Rotors will become slow due to old oil thickening, or because grease has washed into the casing. It is important when oiling the internal valves to avoid dripping oil on the walls of the slides, to avoid grease from slowing the action of the rotor. This is why most bottles of oil use a needle applicator, to allow more direct oiling.
The second issue is that rotors become stiff or become dry. I see this more frequently with instruments that are not used regularly infrequently. With regular use, the valves remain moist due to condensation, and the rotor won’t become dry/crystallised.
If this occurs, oil the bearing points and oil the rotor internally as per the diagram. When all points are oiled – turn the valve by using the stop-arm (photo below). Don’t use the lever arms to move the valve as this may lead to accidentally bending the lever arms, or loosening the string.
By lubricating the bearing points, and dropping oil onto the valve, it will relubricate the walls of the casing and you should be able to rejuvenate the action. However, sometimes this is unsuccessful and at that point it is best to see a professional repair technician.
*Another reason to oil the valves internally is to help deter corrosion. This is the same principle as applying a lubricant onto a bike chain or any other metal component exposed to oxidising agents such as air, moisture or salt. However, for less careful or experienced players this can lead to washing slide grease into the rotor casing which is a nuisance. This is an issue the occurs a lot more with french-horns. Inevitably the rotor surfaces will still develop corrosion, so I don’t believe it’s critical in this case.
Instruments that feature mechanical linkages such as minibals or older style pinned mechanisms should be oiled to reduce noise and wear. Hetman ball joint oil is a suitable oil for this purpose.