Build a Peristaltic Pump
Like many brewers, I have the occasional need to move liquids from one place to another (transfer wort from kettle to fermenter, or rack from fermenter to keg, etc.). There are many pumps on the market that can assist in moving liquids from place to place. Most of these pumps, such as the March or Chugger pumps are “centrifugal” pumps, which use a rapidly spinning impeller to push liquid from place to place. These pumps are great, but they have three significant drawbacks for how I want to use my pump: They require priming (meaning the pump head needs to be filled with liquid before you turn on the pump); They aren’t very portable (most brewing pumps run on mains voltage which makes it difficult to use outdoors); and they can be expensive. For occasional use, it is hard to justify that sort of expense to my non-brewing significant other.
If I could add a fourth issue, it would be sanitation. Those fancy pumps are opaque and full of little nooks and crannies where spoilage organisms could hide. That’s not an inherent weakness if you maintain proper sanitation, but I know people, and people are lazy.
So, how does an enterprising brewer solve these issues and move 6 gallons (23 L) of hot wort around? A peristaltic pump!
Peristaltic pumps are great because they don’t require priming. They can actually pull liquids up out of a carboy, kettle, or keg, instead of needing gravity to prime. A peristaltic pump can also be driven by virtually any motor. In my case, I use a drill. This way, I can brew outdoors. Peristaltic pumps are also cheap to construct and simple to sanitize. In fact, the pump itself never touches your precious beer, only the silicone hose does, which you need to clean and sanitize anyway.
Peristaltic pumps work by occluding (squeezing) a section of tubing, and moving that occlusion around the body of the pump, pushing along a volume of liquid, and pulling in the next slug of wort. For more information about how they work, check out the Wikipedia article on peristaltic pumps (https://en.wikipedia.org/wiki/Peristaltic_pump)
Now, let’s look at how we can make one of these wondrous liquid moving marvels for ourselves.
** Safety note: With this project, you may be pumping around very hot liquid. Don’t use a ball valve to control the flow from your pump, because the silicone hose can soften with heat and cause the hose to slip from the barb, spraying hot wort all over the place.
Materials and Tools
9.5-inch (24-cm) springform cake pan
(4) 2-inch (5-cm) casters
5-foot (1.5 m) silicone hose (1⁄2-inch ID, 3⁄4-inch OD)
Scrap piece of hardwood (~3 3⁄16-inch square, 1 1⁄2-inch thick)
(2) 1-inch or larger washers
(2) 1⁄2-inch washers.
(2) 1⁄4-inch -20 T-nuts
(2) 1⁄4-inch -20 nuts 1⁄4 x 3-inch – 20 bolt
(8) #12 3⁄4-inch wood screws
Zip ties
Hammer
Compass
Drill and bits
Dremel tool or similar with grinding stone and cutting wheel
7⁄16-inch socket/ratchet and wrench
Screwdriver
Framing square
Saw
Step by Step
1. CUT AND DRILL ROLLER MOUNT
Collect all of the materials and begin by laying your block of wood in the cake pan with your casters (rollers). Figure out the size your wooden block needs to be to mount all four rollers, in my case it was 3 3⁄16-inch (8.1-cm) square. Use the framing square to mark your cuts, then use the table saw to cut the block of wood to size. Use the framing square to mark midpoint of your square. This step is important, so measure three times. Drill a hole in the middle of your square of wood and insert the T-nuts. The hammer comes in very handy for this operation to help “seat” the T-nuts. You can also thread in the bolt and nuts on either side, tightening them will help tighten down the T-nuts. The T-nuts are very important to the drive system at this point, so take your time. Remove the bolt, not doing so makes the next step more difficult.
2. DRILL & MOUNT THE CASTERS
Since our rollers for occluding the pump are, in fact, cheap casters, care needs to be taken in this step to ensure that each unique hole pattern matches up with the holes in the wood block. You’ll notice in the picture that I marked numbers 1–4 on the wooden block and on the casters themselves. Also, the casters are all oriented with the divot side of their rivet facing up. That helps keep things aligned. Lay the block face up on a horizontal surface. The floor works just fine. If the block is wobbly because of the T-nut, just place one of those big washers underneath the block at the center. Place each of the casters up against the block, as evenly as possible. Now mark the center of the hole with a pencil. Once all the holes are marked, drill the holes for the screws at an angle so that the evens are angled up and the odds are angled down. This is easier if you start with a small drill bit and step up to a larger one. The reason for doing this is so that the screws don’t hit each other. Alternatively, you could use a larger caster with more mounting holes and alternate them. Once the holes have been drilled, line up the caster with the holes and screw them down. The casters should be relatively flush with the bottom of the wooden block once mounted.
3. DRILL THE CENTER OF YOUR HOUSING (CAKE PAN)
Take out the bottom of the springform pan and find the center, either by using a compass or careful measurements. Drill out the center of the cake pan bottom. I like to start with a spring-loaded center punch. It’s pretty thin metal so be careful drilling as you can get little bits of metal going everywhere. Smooth out the hole with some dremel grinding.
4. MOUNT THE ROLLER ASSEMBLY TO THE HOUSING
Start by adding your washers to the bolt that goes through the wooden block. I happened to have two that fit one-inside-the-other. If you don’t, that’s okay. A fender washer should work just as well. Insert the bolt through the hole in the cake pan bottom. Make sure you have it going the right way. Add washers to the underside of the bolt. Again, one inside the other. Thread on your nuts. I use two, one to go snug against the washers (not tight, it needs to allow the bolt to spin), then another snug against it. Then loosen the first nut (the one on the underside of the cake pan bottom), so that it tightens against the top nut. This is called a jam nut. If you had a cap nut, this would be a good place to use it for a more finished look, and to allow an easier time driving from the back, since you wouldn’t have to worry about over tightening the nuts and locking everything up.
5. CUT TUBING HOLES IN YOUR HOUSING
You now need to cut holes in the cake pan for the tubing to ingress and egress. Figure out where you want your holes. I figured I wanted mine at about 10 and 2, like driving. I put the holes on either side of the spring catch mechanism, so the rivets wouldn’t hit the tube. Make sure you are avoiding the catch itself as well as the part that slides in/out. Draw some rectangles near the bottom of the pan walls, where the rollers will be. Ensure that your tubing will fit through the holes. Cut out your rectangles with a dremel-type tool, but leave one edge attached. This will be how you mount the tubing. Bend out the tabs and grind away sharp edges. Now insert your hose and zip tie the hose to the tabs.
6. PUTTING IT ALL TOGETHER
Drop the top of the pan onto the bottom. Cinch down the springform mechanism, ensuring the bottom of the pan is aligned with the groove in the bottom part of the side.
Turn the pump assembly a few times by hand. The tubing should be pulled down and squished (occluded) by the rollers. Now you can go pump something! Attach that 7⁄16 driver to your drill, put the drill in forward drive, put the drill on the bolt and give it a few spins. Now put the inflow end of the tube in some liquid to pump, then goose the drill up slowly. You should be pumping!
To see video of my peristaltic pump in action, visit www.instructables.com/id/Inexpensive-easy-to-build-peristaltic-pump/
