Re: rotary valve noise


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Posted by JohnK on December 22, 2002 at 10:53:11:

In Reply to: rotary valve noise posted by Jordan Jay on December 19, 2002 at 21:08:52:

There are several things that could be causing "noise". However, having looked through the responses that you have gotten so far, I would suggest a few things.

Beyond loose screws and missing bumpers on your stop plates, the other cause of clank is slack in the linkage. This usually takes place somewhere in the bearings where the connecting rod is screwed to the stop arm (and the lever, on the the other side). Some of these problems can be fixed without too much trouble. Others have an expensive price tag on them.

First, VMI has used several different types of linkage over the years. The two most common to see today are both ball-bearing. First, there are linkages that have connecting rods with screws on the ends, to hold the ball in place. In this case, you should take the screw out, and clean the parts really well with brasso and a Q-Tip (then with soap and water). Then, oil the parts with a drop or two of heavy oil (10w-30 motor oil). These bearing can wear out, but this proceedure can sometimes help to reverse the clank caused by corrosion.

The other type would be a Uni-Ball Bearing. On the end of the connecting rod, there is a bearing that screws on. There is a ball in the center of that bearing, and a screw that holds that bearing to the stop arm. In this case, try applying heavy oil to the bearing to help dampen the vibrations. Apply a drop or two of 10w-30 to the ball, and allow to set for a few minutes.

If your tuba has linkage other than these two, most likely there isn't much that can save you. Most likely in this case, you are in the market for a linkage-change-over. The reason why the second type of linkage I described is the preferred type of linkage is because of its ease of repair. A repairman can replace the Uni-Ball Bearing in a matter of minutes, and your linkage will be like new. Any other form of linkage can only be fixed through tedious custom work.

Hope this helps,
John


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