Re: Test vacuum Gauge
By Douglas K. Rhodes
Greetings:
This is in response to Brett Mohr's query regarding the water manometer. I used a fancy term for a plain old vacuum gauge, an example of which is described by Reblitz in Player Piano Servicing & Rebuilding on page 8. My preference would be to make it direct reading instead of differential. Set up a quart or half gallon bottle on the back of the workbench with colored water in it, and stick a 1/4" I.D. clear plastic hose into the water by several inches. (Don't seal the neck of the bottle - air must be able to get in.) Take the hose straight up as high as you can (at least 40" above the water level), then over and down to your test situation. Tack a yardstick on the wall behind the hose, with the zero inches end even with the water level in the bottle. If the hose goes vertically more inches than the maximum your vacuum source can deliver, you won't get any water into your parts or vacuum supply. Experiment with smaller or larger I.D. hose until you get results that you like. And have fun.
I wouldn't worry too much about the mildly disappointing results of thirty seconds leakdown time for your pump. Try as we might, there are some systems that have just too many surfaces or junctions susceptible to leakage. I've seen players work well (as long as the stack was tight) with pumps that leak down in only ten seconds . A full minute would be ideal, but 30 seconds is nothing to be ashamed of.
By the way, do take note of Bob Conant's cogent comments at the end of his contribution Re: Cable piano motor in the Automatic Music Digest 96.01.20. I knew I didn't want to have to do much sucking on old player parts, no matter how much I'd be able to brag about it afterwards, but I'd forgotten about lead tubing, and how that innocent looking white dust is eventually distributed throughout the pneumatic system. The Mad Hatter got his name by absorbing mercury during the felt-making process in the 19th century. We can only guess what makes us crazy enough to work on old player pianos.
Cheers.
Doug Rhodes
Victoria, B.C. Canada
wo631@freenet.victoria.bc.ca |
(Message sent Tue 23 Jan 1996, 19:06:35 GMT, from time zone GMT-0800.) |
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