A simple form of driving gear is shown. The main shaft C is rotated by a large bevel gear D, meshing with a small pinion E on the end of a driving shaft F, which is driven by a belt. This shaft also carries a bevel gear L, which meshes with a bevel gear K mounted on a sleeve. This sleeve surrounds and rotates freely on the central shaft C, being supported at its lower end in ball bearings m m, mounted on the shaft. This combination gives opposite rotation to the faces and stirrer arms and at different speeds. The driving mechanism can be of course varied.
Another simple method of air cooling would be to let the mash run down a series of enclosed steps or chutes, the casing being kept cool by an air blast. Mashes may be even cooled by mere stirring by paddles, but this takes a long time and much labor.
The preparatory mash vats used to-day are almost all provided with stirrers formed of hollow blades capable of a rapid stirring movement through the mash. Through the hollow blades cold water is forced. Mash vats of this kind should have the following qualities. They should be strongly built, particularly as regards the stirrers so as to be used with thick mashes. They should thoroughly and uniformly stir and mix the mash and they should be capable of cooling the mash within an hour, and should be so constructed as to be easily cleaned.
By using coils of pipe which may be inserted or withdrawn from the mash tub, and through which cold water is forced, the mash may be effectively cooled, but the best plan for quick cooling is to bring a comparatively thin layer of the mash in contact with the coils. This may be conveniently done by using a system of comparatively large water pipes enclosing small pipes for the passage of the mash.
Fig. 4.—Mash Cooler, Water System.
This should be arranged in a stand like the coils of a radiator with an incline from the inlet end of the top pipe to the outlet end of the lowermost pipe. As stated, the small pipe carries the mash, the large pipe the water.
Preferably the mash flows downward while the water is forced upward in a contrary direction by means of a pump or a high level reservoir. The cooled mash should flow into the fermenting tank at a temperature of about 68° F.
There are many varieties of mash cooling apparatuses on the market of more or less complication suited to the needs of large and expensive plants.