Bellows Testing
By Les Smith
Hello again, Brett Mohr. With reagrds to your question about your rebuilt bellows holding suction for 30 seconds vs Reblitz's 60 seconds:
If this is your first player rebuild, 30 seconds isn't too bad, believe me, I've seen MUCH worse. However, Reblitz is right. With careful rebuilding you should be able to get your bellows to hold suction for 45-60 seconds EVERY time. The really critical question, however, is:
How long will your bellows hold suction when connected to the stack?
Try these tests.
First, disconnect all the hoses going to the lower bellows and seal off all their nipples with duct tape. Pump the pedals until the reservoir(s) collapse and measure how long they will hold suction. If it's 30 seconds or less you probably have leaks. Go down on the floor, have someone else pump the pedals and listen for leaks. Once you're sure you have the bellows as airtight as possible, connect the hose going to the stack, tape off all the holes in the tracker bar with another piece of duct tape, and pump the pedals until the reservoir(s) collapse. NOW see how long they'll hold suction. If you did a REALLY good job of rebuilding the valves, pouches and gaskets, the bellows should hold suction just as long as they did BEFORE you connected them to the stack. If there's a big difference -- say they held suction for 30 seconds before being connected to the stack and only 15 seconds after being connected -- you have problems, most likely related to the valves not holding suction on their lower seats. Which could be the result of not enough wobble in the valve, not enough dish in your pouches, or even using too thick a lifter disk. At any rate, a wide variance here, means that your stack has problems. A stethoscope can be a big help in locating leaks. Some people advocate sticking a piece of tubing in your ear to help locate the leaks, but I feel more comfortable using a stethoscope from which the collector has been removed. Summing up, your player probably will work with a bellows that holds suction for 30 seconds, but if you have pneumatic rail lifters in addition to a sustain pneumatic, your going to have to do some vigorous pumping to use them all at the same time!
Les Smith lessmith@buffnet.net
P.S. After removing the piece of tape from your tracker bar, clean the bar with some naptha and a soft cloth to remove all traces of adhesive. |
(Message sent Tue 23 Jan 1996, 06:07:18 GMT, from time zone GMT-0500.) |
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