DR. BOB TECHNICAL'S WHEELS OF BEER
We're sorry to say that these beautifully simple devices are out of print at the moment.
The Wheel of Beer and Hop-Go Round are analog slide rule calculators designed to make on-the-fly homebrewing recipes easy without the complication of computers and software. Nothing against any of those fine and useful products; sometimes simpler is just better.
There are two of them: The Wheel of Beer is a wort gravity calculator. It was my first published project of any kind. The Hop-Go-Round calculates hop bitterness.
They really do work well; the hop calculations were tested by a group of highly technical homebrewers back in the 1990s and according to their tests, the Hop-Go-Round did better than anybody else's system at accurately predicting beer IBUs. Of course, there are a lot of variables besides the six this wheel deals with, so as with any calculation system, a little personal calibration based on experience will give best results.
I have been working on rebuilding the original graphic files from the late 1980s, which has been just a little bit of a challenge. Our plan is to get them into the wholesale market, and also offer them one-by-one on eBay, or volume sales (by the dozen) directly through us. Hopefully, this will happen sometime this fall. I know there are people waiting for them.
INSTRUCTIONS FOR USING
Wheel of Beer
• The outside of the scale corresponds to the batch size you're brewing. 5 gallons is highlighted as it is the most common brew size.
• The next scale inward (the outside scale on the middle wheel) represents pounds of your chosen ingredient.
• On the inner wheel, various ingredients are listed, each one contributing a different theoretical amount of extract per unit of weight. Line up the curved line from your chosen grain or sugar to the "Ingredient" pointer on the middle wheel and lock them together with your fingers to prevent them from shifting. If you know the theoretical gravity contribution, you can use the percentage scale adjacent to the ingredient list.
• Now line up the batch size you're brewing with the number of pounds you wish to use.
• The gravity can be read in the window on the right side of the middle disk, with one scale in OG and another in °Plato. Gravity must be read at a particular efficiency. 100% is the laboratory maximum, but most homebrewers fall somewhere between 70 and 80% of this. If you don't know you efficiency, recalculate a past recipe with this wheel assuming 100% efficiency and then compare to your actual results. Divide the actual gravity by the theoretical one; the resulting number will be your percentage.
• Each ingredient must be calculated separately. If you want to work backwards, assign an OG target (or a percentage of gravity or to each ingredient and calculate its needed contribution), then slide the wheel so you see the gravity in the window, and then look at the weight quantity across from your batch size on the two outer scales.
• Everyone's system is different, due to a variety of factors, including mashing procedures. Over time, you'll develop a good idea of what to expect for any given brew.
• Be aware that sugars always come in at 100% of their theoretical gravity, as they yield all their weight directly into the kettle.
• Small changes in the total quantity of wort can have surprisingly large effects on efficiency, so be careful not to end up with too much or too little wort at the end.
• Start the process on the back of the wheel. You will need to know the alpha acid content of each of the hops you're using, along with the gravity of the beer you plan to brew. Normally this is provided on the hop package, but more general varietal information will work as well.
• Each hop addition and variety must be calculated individually and added up at the end.
• Find the intersection of the wort gravity and the curved line for the length of time this hop will be in the boil. Read across horizontally to the utilization number on one of the scales at the right of the chart. Note that pellets and whole cone hops have different efficiencies. Make a note of the utilization number.
• Flip the wheel over, and line up this utilization number with the alpha acid percentage of the chosen hop. Holding those two scales together with your fingers, line up the batch size on the outer scale with the quantity on the scale across from it. Note that quantities are marked in both ounces and grams.
• Finally, read the estimated IBU (bitterness) from one of the two windows in the black area which reference either the ounces or grams scale.
• To work backward, assign a bitterness target for each hop addition. Then follow all the instructions, but rather than lining up the weights across from batch sizes, line up the gram or ounce pointer with the desired bitterness value, then read the quantity needed across from the batch size.
• Small variations in final batch size can have a surprisingly large effect on bitterness, so try not to product too much or too little wort. Even more important, allowing the boil to go on longer than planned will significantly increase the bitterness of all the hop additions, to try to brew in schedule
• Getting a larger amount of bitterness from hops added late in the boil will greatly increase hop aroma, so use this technique if you're looking for a blast of hops in the nose.