Re: Piston or Rotary


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Posted by John S. on April 25, 2002 at 09:08:53:

In Reply to: Piston or Rotary posted by Nobody on April 24, 2002 at 14:32:17:

I wouldnít make a decision to buy a particular instrument based upon whether it has piston or rotary valves, or a combination of the two, because there are excellent and rotten examples of both types of horns on the market. I would advise throwing out your preconceptions and just selecting the instrument that gives you the best sound and response yet is playable in tune.

I own both piston valve and rotary valve horns. Piston valves can be problematic until they are broken in, but after that, and with the use of appropriate valve oil, they are agile and easily maintained. Rotary valves are not as easy to take apart but should require very little maintenance. I would say though that rotary valves have some (at least theoretical) advantages.

1. Rotary valves have less mass than piston valves. This should make it easier to make rotary valves quiet. I hate banging and clattering valves, especially during solo playing, but there are noisy rotary valve horns, usually due to bad bumpers or linkage and quiet piston valve horns, usually due to good pad and spring selection.

2. Rotary valves have less surface area in contact with the valve casing than piston valves. This should make it easier to keep the valves moving fast and freely. There are, however, rotary valve horns that stick, usually due to misalignment or lack of maintenance. Piston valve proponents often cite the difficulty of rotary valve maintenance. My personal experience: I have owned an Alexander 163 rotary valve tuba since 1971. I have never ever taken the valves apart personally. In fact, I donít even know how to take them apart! During the approximately thirty years of daily use since Iíve owned the horn service people have taken the valves apart four or five times, including one major overhaul and valve plating job. All I do to maintain the valves is flush them out about twice a year and add a drop of oil to the rotor bearings about once a month. I have to take my piston valve horn apart to oil it every two weeks!

3. It is easier to make rotary valves in larger bore sizes.



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