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The evolution of the Axial valve.


Traditional Axial Valve

C. Bosc Axial SMILE

Rotor in anodized aluminium.
After a certain period the anodized coating wears away, and the aluminium begins to oxidize, creating problems with motion (the rotor tends to “stick”) and a loss of compression.
Rotor in brass (weighs only about 30-35 grams more than the aluminium rotor)
Valve cap soldered to the tubes of the main branch and the exit of the second branch. During the soldering process the valve plate becomes deformed, and all the tension of the instrument is transfered to the valve cap. The valve cover and the valve plate are separate. The tubes are soldered to the cover without touching the valve plate.
Difficult to unscrew the lever screw. Screw changed to the sideway.
The rotor shaft tends to become worn and rounded. Rotor shaft made from cemented carbide with a bushing in nickel silver to prevent wear.

The valve casing is machined from a solid block and has no soldered parts.

In the valves for both bass and contrabass trombone the entry of the first and second valves are inclined 1,5° to have the corpus of the instrument aligned with the bell.

The rotor is made in a single piece from brass, machined to weigh as little as possible and lessen the problems of corrosion and wear.

Inside the rotor there is a stainless steel bushing that goes between it and the pin of the valve plate (see image below). If the valve develops play between the pin and the rotor, a smaller bushing can be substituted.

The valve plate (SMILE) is in stainless steel.

In the event that the valve begins to lose compression, the valve plate can be re-lapped with the rotor and its casing.

Inside the cover where the exit tubes are soldered there are the corks and a bushing in nickel silver for the rotor shaft which transmits the motion to the inside of the valve. The bushing serves to absorb all of the torsion from the movement of the valve lever.

Connecting rod with carbide shaft to transmit the motion to the inside of the valve.

Valve cover with cap for valve linkage. The adjustment screw is on the side of the shaft.

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