Making a Muller might look
like a real challenge, but it's
real a simple machine!
It's basically just a slow
turning mixer. Some have
just blades and others have
I'll try an clear this up.
Lawyer BS to cover my Butt.
WARNING!!!: You got a brain... USE IT! Building and working with a foundry furnace is "NOT" child's play. It can be very dangerous and if 'you' screw-up don't come crying back to me! If you don't know what you're doing and didn't take the time to read and study all the safety procedures that are available on the net, as well as your local library, and you get hurt that's your problem. You are responsible for yourself and your own actions and safety.
--- "NOT ME!" ---
THE POORMANS MULLER:
Take a 5 gallon bucket or a small to medium "Metal" garbage can and mount it on some kind of a turntable, (Slow turning not over 40 rpms), seeing that a garbage can has a recessed bottom you could make it so it sits over a turntable and use screws or bolts to hold it in place.
Line the bottom of the can with 3/16" to 1/4" steel plate, (this will be the wear plate otherwise the sand would wear thru the bottom of the can in no time.)
Cut the plate to the exact diameter or maybe even a 32nd bigger. Put it in tight against the bottom and turn the bucket/garbage can over and drill small pilot holes all around the inside edge and about an inch in from the edge; (About 3" spacing is good), then another circle of holes closer to the center. Take a black magic marker and mark a spot on the plate and the bucket so you'll know where it lines up with the holes you've drilled. Remove the plate and drill and tap to whatever size you like, (1/4-20 is a good and common size). Drill out the holes in the bucket to fit the size you choose. Now replace the plate and using the biggest flat washers you can get; bolt it in. Making sure that you don't use too long of a bolt. If it's too long you may have to use extra flat washers as spacers or just get shorter bolts.
Now you need to make an overhead 'u' shaped bracket that just clears the top of the bucket by a few inches, 6 inch at the most, (Think of an upside down square ended "U" ), In the center of the U bracket drill a 3/4" hole. (This bracket has to be strong enough to take the pressure and twisting of mixing the sand. Rectangle tubing to 3" or 4" "C" channel would work.)
Take a 1/4" or 3/8" flat bar about 2" to 2-1/2" wide and about a 3/8" shorter in length then the inside diameter of the bucket.
Drill a 3/4" hole in the center. Then you have to measure out an inch each way from the center. Keeping the 2" center section flat, heat the bar with a torch and do a "Quarter" (45°) "twist" from there to the end of the bar on both sides. One going to the left and one going to the right. Then check to make sure the bottom edges are inline with each other. (The bottom edges should be flush against a table or straight edge.)
Next take a 1/4" x 1-1/2" x 6" flat bar and form it to the inside diameter of the bucket and weld that on the ends of the twisted bar so that leading end is about a 1/2" past the end of the twisted bar and they will 'just' scrap/rub against the sides and be flush with the bottom of the twisted bar... on the back end of this scrapper bar add a little more bend or hook to it so it will push the sand back into the center. Braze or weld a 3/4" nut over the center hole of the "TOP" of the bar. (making sure the side that's bent down is facing into the direction the bucket turns. so if you're looking straight down into the bucket and it turns clockwise the right side of the bar should be down and the left will be up. Can you see what happens? the left side facing up compresses the sand down against the bottom of the bucket and the right side scraps the sand back up off the bottom of the bucket.)
Next get a 3/4" ready rod, ( the rods that have threads the entire length -- NOTE: The bigger you make this Muller the bigger this rod has to be.) and several nuts and lock washers. On the bottom end of the rod spin on a nut 'then' a lock washer then thread on your twisted bar so it's flush with the end of the rod and tighten down that top nut to lock it in place. On the top end of the rod spin on a nut then lock washer far enough down so you can get the bucket in place, then slip it into the hole in the 'u' shaped bracket and put the bucket in place and lower the (Now) mixing rod down to the bottom of the bucket. Spin the lower nut up and put a lock washer and nut on top of the bracket and tighten them up. (NOTE: You don't want the mixing bar tight against the bottom of the bucket... if anything it should be about 1/8" but not more than 1/4" off the bottom.)
You now have a poormans muller.
Be sure to check out my page on making "GREEN SAND"
The bucket turns on the turntable and the twisted blades --- one side compress the other side scraps it up and the side scrapping bars help roll the sand back into the center and keeps the bar centered in the bucket...
Side Note: If it looks like it isn't working right --- you might have made the blade upside down or turning the bucket the wrong direction. You can fix that by either changing the rotation of the table or make a new bottom bar with the nut and scrapper bars welded on the other side, "OR" you welded the scrapper bars facing in the wrong direction.
How much you can mix at one time will depend on how powerful your turn table is. If you got a 1-1/2 hp motor and you gear reduce it to 30/40 rpms at the table, it "might" be able to do 40 to 50 pounds at a time.
FOLLOW-UP SIDE NOTE:
Another type of muller is like the old style cement mixer style with the paddles rotating on a horizontal shaft.
They have the tub and then a cross shaft with paddles in it. You might be able to find an old one laying around in some junk yard or check at a cement contractor and see if they've got one they don't use any more. You'll have to modify the paddles and maybe replace a bearing or two, but it's a lot cheaper. Forget about the newer styles with the rolling drum, they turn to fast and the sand/clay mix is just to thick once you start adding in the water or oil. (BEEN THERE DONE THAT!! DOESN'T WORK!)
I found another design by George Vontorne, in which he uses a (NEW) propane tank, but I'm going to modify his design and see if it's works any better. I'll post pictures of the build when I get into it.