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DIY: Beer Engine

Want to have your own cask ale on tap? Jester Goldman shows you have to build a fairly simple version of a beer engine and then explains how you can pretty it up.

Jester Goldman August 11, 2017

DIY: Beer Engine Primary Image

In Great Britain, the Campaign for Real Ale (CAMRA) revived the demand for cask-conditioned beer, and today, it’s not uncommon for craft breweries to offer a cask ale in their tasting room. You can pull this off at home using a corny keg for conditioning, but how should you serve it? Like the pros, you can either elevate the keg and use gravity, or you can use a beer engine to pump the beer.

Beer engines typically cost well over $500, but you can save most of that money by building your own based around a hand pump designed for a sink in an RV or camper. While these devices are intended for potable water, I’ve been unable to nail down whether their plastic parts are FDA-certified as food safe. Personally, I’m not concerned, but if you are, this may not be a good project for you.

Let’s first take a look at a fairly simple version that will give you the beer engine experience and then talk about how to improve the aesthetics.

Keeping it Simple

In its bare-bones form, we just need to mount the RV hand pump onto a box, connect the pump to the keg, and extend the serving spout.

Parts

  • Valterra RP800 Rocket hand pump (or equivalent)
  • 36" x 24" (91.5 x 61 cm) rectangle of good quality plywood, 1/2" (1.3 cm) thick
  • Sixteen 1-1/4" (3.2 cm) wood screws
  • 5 inches (13 cm) of 3/8" (9 mm) ID vinyl tubing
  • 3 feet of 3/8" (9 mm) ID vinyl tubing
  • 2 hose clamps
  • Liquid line keg fitting (ball or pin lock)

Build Steps

1. From the plywood, cut the wood for the box.

  • Top: 9" x 9" (23 x 23 cm) square. On the bottom side, pencil in the diagonals to mark the center. Using a 1-1/2" (3.8 cm) hole saw, cut a hole on that center. Use a dremel with a sanding barrel to widen the hole slightly to accommodate the bottom cylinder of the pump.
  • Sides: Two 9" x 9" (23 x 23 cm) squares
  • Front and back: Two 9" x 8" (23 x 20 cm) rectangles

2. Assemble the box.
1. The front and back pieces will fit within the sides, making a 9" x 9" x 9" (23 x 23 x 23 cm) cube.
2. Drill 2 pilot holes on each side piece along the edge into the front wall. Drill similar pilot holes along the edge into the back wall.
3. Apply a thin layer of glue to the side edges of the front and back walls, then screw the sides to the front and back. You should now have a cubic box, with no top or bottom.
4. Drill pilot holes along each edge of the top piece, going into the sides of the cube.
5. Apply a thin layer of glue to the top edges of the cube and then screw the top onto the cube. Allow time for the glue to dry.
6. Sand and finish the box as desired.

3. Mount the hand pump to the box.
1. Place the pump onto the top of the box and use a nail to mark the screw locations.
2. Remove the pump and drill small pilot holes for the two screws.
3. Replace the pump and screw it to the top of the box.

4. Attach the beer line to the pump.
1. Use a hose clamp to attach the 3’ (91 cm) section of vinyl tubing to the barb on the bottom of the hand pump.
2. Attach the other end of the tubing to the keg fitting, using the other hose clamp.
3. Extend the spout by sliding the small piece of vinyl tubing over the end to simulate a swan neck. Voilà!

Getting Fancier

Our simple pump is functional, but it’s not nearly as pretty as what you’d see in a classic English pub. A few modifications can get us much closer. Before you dive in, understand that these changes are not trivial and the aesthetic improvements will increase the cost and the build effort.

The first step is to hide the pump body inside the box. This requires the pump to be mounted on an internal platform within the box. Rather than centering the pump, you will need to place it close enough to the side to let the handle through.

Speaking of the original handle, it’s a bit short and utilitarian, so you should remove the plastic grip. Then you can cut threads into the metal shaft with a die to make it compatible with a longer beer engine handle. Don’t forget that the hole in the side of the box needs to be large enough to give the handle free range of motion.

With the pump body hidden away, we can complete the project by mounting a swan-necked spout through the box, and then attaching it to the original spout with vinyl tubing. The spout itself can be made by shaping some stainless steel tubing into the familiar swan neck shape, and then running the pump side horizontally for about 4" (10 cm). You’ll need a connector fitting to mount the swan neck centered into the front of the box.

Pressure Management and Use

Contrary to some criticism, cask-conditioned beer is not flat, but the carbonation level is pretty low. Ideally, you would cask the beer near the end of secondary fermentation or add a touch of priming sugar when you transfer the beer. CAMRA wouldn’t approve, but you could also artificially carbonate. In any case, the beer should only contain about one volume of CO2.

It’s also important to understand that classic English cask ale has a short shelf life because air bleeds into the cask while beer is being served. Homebrewers using a keg can get similar results by just opening the pressure relief valve. That’s fine if you’re planning to finish the whole batch within a couple of days, but there are other alternatives.

If you have several kegs, you could purge the head space with CO2, then transfer only a gallon or so into each keg. This gives you smaller volumes that you’re more likely to finish before they spoil.

On the other hand, instead of letting air in, you can manually add a small touch of CO2 to maintain the blanket protecting the beer from oxidation, or you can use a low pressure CO2 breather to automatically do the same.

Cheers to having your own cask ale on tap!

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