This is the ball mill that I purchased in Jingdezhen about 5 years ago. I believe the cost was around 2400RMB, approximately $350USD.
The mill accommodates two large jars on the top level and two small jars on the bottom level.
Model number YY7144, 220V, 550W, 6.5A, 50Hz, speed 1400r/min.
The large jars rotate at around 80 revolutions per minute.
From Ray Aldridge via Clayart:
The right speed is a function of the jars internal diameter. According to Cardew, the right speed is 64 to 87% of critical speed, which can be found by using this formula:
Critical speed in rpm=54.19 divided by the square root of R (when R is the internal radius expressed in feet)
Large jar internal diameter 24cm = .79ft
.79ft / 2 = .395ft radius
square root of .395 = .628
54.19 / .628 = 86.3RPM critical speed
Mill should be operated at 55-75RPM. Currently at 80RPM.
The jars are locally made in Jingdezhen using a strong porcelain body. Each jar is individually thrown (note the throwing rings) and has a heavy rubber stopper that is gently hammered in. The jars are only glazed on the outside.
Notice the rubber stoppers do not have locks. Even though quite a lot of pressure builds up inside the jar during milling, the rubber stoppers have never fallen out during use.
Two large jars on top level:
One large jar and one small jar (can fit two jars on each level):
Jar with rubber stopper:
Two types of grinding media are commonly sold in Jingdezhen, porcelain balls and a special type of natural stone (needs research). The natural stones come in a variety of sizes. According to the ball mill manufacturer’s recommendation, I only fill each jar with about 1/3 media. When wet grinding glaze, I only fill the jar half-way. The mill should be very loud when in use.
Ball mill steel frame dimensions: 80cm wide, 55cm deep, 35cm high.
Large jar dimensions: 35cm height, 30cm diameter. 12cm diameter mouth, approximately 24cm inner diameter.
Small jar dimensions: 20.5cm height, 16cm diameter. 8.5cm diameter mouth, approximately 12cm inner diameter.
TODO: Add all measurements