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MMD > Archives > June 1996 > 1996.06.16 > 02Prev  Next

Re: Grasshopper Pump Solution
By Craig Brougher

If Patrick Mullarky wishes, he is welcome to send the pump to me, and I guarantee that he will get back a quiet pump, with original style wood crankrods. I have used one now for 12-13 years on my test bench. They are fine.

I haven't run into a flimsy grasshopper pump yet, but perhaps there was one. My pump has these measurements: crankshaft-- 5/8"dia. Main bearing posts are 2" x 1.5", maple, adjustable, with "oilers" inserted. The crankrods are about 4" ctr-ctr. The crankrod bosses about 2" x 1.25" with a 1/4" steel pin. The large pulley is about 12" dia. and the bellows are 6" wide.

Any pump that has too much resistance through the flaps will always be noisy, and increasing the width of the flaps exacerbates the problem. If a pump is to pump quietly, it must require as little flap motion as possible to exhaust as much air as necessary without tending to inflate each closing bellows. At least that particular flap is the outside flap and easy to get to. One of the faults I have found is, flaps which are too heavy and too tightly sprung. It is better to use a lightweight shoe leather and pneumatic cloth backing today to prevent stretching. The original leather was industrial grade, meaning it was pre-stretched and compacted. You cannot buy that anymore.

Also, the covering material should be regular weight bellows cloth, and not the lighter grades of treadle cloth such as the covering sold by Schaff.

Craig B.

(Message sent Sun 16 Jun 1996, 14:21:10 GMT, from time zone GMT.)

Key Words in Subject:  Grasshopper, Pump, Solution

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