Above is a photo of a muller that I designed and built around 12 years ago. I got the idea from a roto tiller and this is basically a rototiller in a drum. Note the legs: The muller was mounted over my sand box and it dumps directly into the box.
Close up of the Muller. Note the cant of the blades. When run forward the blades provide a good mixing action and will handle a fairly large load. When run in reverse the blades provide a squeezing action for mulling. But as the mulling consumes a lot of power load capacity will be reduced. I cast in Petrobond and found that mixing was adequate with a mull around the 10th cycle of sand. If making new petrobond from scratch, you must mull it for around 20 minutes to activate the petrobond.
The above photo shows the drive train. The gear box is a 40:1 worm gear.
Last, this shows the dump arrangement.
Author: Jerry Twaddell