Mark's Place
Got Questions? E-mail me here
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Mark's Place Got Questions? E-mail me here |
The Pump
I got ideas for my pump mainly from photos and from a small medical pump my brother, Neal, loaned me from his veterinarian practice. The main difference is that my pump is much larger than its medical counterparts and some areas were simplified because I didn't feel they were necessary for my application. My design The tubing I use is 1/2" ID Norprene tubing (a variant of Tygon) and not to be confused with Neoprene. Norprene is suitable for peristaltic pumps, along with being food grade and boiling temperature rated. I only use a short piece of it, however, and transition to braided vinyl tubing on both ends with double hose barbs. With this setup, I can pump as much as 8 gallons per minute or as little as a quart per minute by simply altering the pump speed! |
The idea of using a peristaltic pump for home brewing was very intriguing to
me. They are somewhat limited in availability but have many attributes
that are great for homebrewing. For example, they are positive displacement
pumps so they are self-priming, they can pump at low to moderate flow rates, and the
liquid never comes in contact with the pump itself. That, and the fact
that they look really cool was enough for me. I chose to build my pump
from scratch for the simple reasons that "I wanted to" and because I would benefit
from the design and machining practice. Another reason was the fact that
purchased peristaltic pumps are normally very overpriced due to the predominant
industry they serve (i.e., the medical industry). In reality, a
peristaltic pump is a very simple design. Basically, a rotating rotor
pinches and releases a piece of tubing filled with the material you wish to
pump. To get an idea of how the principle works, place a straw in a glass
of water. Pinch the straw between your fingers just below the water level and
run your fingers upwards. If done fast enough and with a good enough seal
you will "push" the water that is above your fingers out and draw the
liquid below your fingers upward. A peristaltic pump works the same way,
only in a rotary manner. 
consists of a 3-rotor head, rotating inside a machined aluminum housing.
Each of the three tips on the rotor contains a cylindrical roller with a pair of
ball bearings for low friction support. I made the pump rotor adjustable
by moving each roller to a different set of mount holes. This is to accommodate
tubing of various thickness. The rotor assembly itself is supported by two ball
bearings located in a block on the rear of the pump housing. A DC motor and variable speed
controller (both a gift from my father) turn the rotor via a v-belt pulley
reduction, also at the rear of the pump.