This primitive machine was built from material and parts which were around for years, maybe for decades. The only parts I bought were the four flange-bearings. Pulleys, shafts, belts, motor were unused, left-over items. The frame used to be a hanging TV support in a demolished restaurant.
I had three tanks to de-rust. The one Jawa and the two Zundapp tanks would have taken a lot of muscle power to clean. The Jawa tank was rusty to an extent which I have never seen before. Also it was stinking after the full tank of gas, what it was put away with years ago, totally evaporated. I was just about to grind off the seam of the Jawa tank to open it up into two pieces, sand-blast it and weld the two pieces together back again (which would have been the real solution), when my sons brought me four ex-TV supports.
Looking at the TV supports standing in the garage gave me the idea for this simple and easy construction. The draw-back of the TV supports is that the two upright stems of them are 24 inches apart which limits the length of a tank to be cleaned. The turning part, is of 4" x 1/4" flat bars cut and welded to a "U" shape and supports the white-disk onto which the tank is strapped down. That white disk used to be the top of a small round table.
First I set-up a Zundapp tank with 5 pounds of roofing nails in it. While the tank was turning the nails were producing quite a noise, which can be heard by playing that short movie-clip. Two daughters of mine were present and they were rolling of laughter, they said that this looks like something out of the 18-th century, strait out of Dr. Frankenstein laboratory; they were right.
I also have a motor-gear-reducer which has a reduction to 12 RPM, an all-in-one construction which would have needed the attention of an electric machine shop. It needs a capacitor to start the motor, which would have cost a lot more, also it would have required considerably more work, however it would have been a more sophisticated machine.
This contraption can do the job for less money and effort.
The contraption has:
a 1/3 HP 1750 rpm single phase motor (should have been 1/2 HP.)
a reduction to 30 RPM (slower would be better)
the frame made of 2" x 1/4" flat bar and 1-1/2 x 1-1/2 square tube.
added pieces were cut from another similar frame.
the frame came with the 1/4" base plate welded on.
For days of continuous running I placed a floor-fan behind the motor.
The Jawa tank was turning for 5 days, 24 hrs per day. Every 6-8 hrs the white disk, supporting the tank, was rotated by 45 degrees. First, 5 pounds of roofing nails, then changed to, 5 pounds of sand-blasting silica were used for cleaning media.
It looked clean after five days. The tank was rinsed out by water and in order to dry water out fast a heat gun was used. Due to the sudden heat the thin layer of water left in the tank became steam and popped of a hand size piece of rust from the top of the tank. Several different shape of scrapers were made and using a mirror, as much as possible, the critical places and seams were scrapped.
Zundapp tanks were easier jobs, they are not split-tanks, open volume tanks easy to clean. 2 days of rotation, changing position by 90 degrees 3 times did the job.
Then, the three tanks were given out for coating. A day of etching followed by a rust protection coating completed the job.