I finally got out to give it a test run. The first material I used was real hard dirt/clay. It worked great and fast for breaking it down.
I tried a lesser amount in the traditional way, and it made me appreciate it more.
The 4.7mm holes are a good starting size to use.
It took very little effort to spin and has a good body postion to use, not squatting over all the time.
Draw backs, and mods needed...
45deg angle left too much wasted punched sheet towards the top area, to help spread the material out better. ( Slowing down the process)
so I will be reducing the pitch.
This may lead me to retro fit a lip around the top edge (40mm) tapering to a cone shape for easier emptying.
This should allow for a flatter angle.
The tumbling action should be inproved after this modification. So I will leave the internal fins etc in place till then.
THE TUB.
it was ok, the tub only needs to be about 30mm either side of the drum.
For the best of ease of using it, set up and total emptying. At least 10 -15 shovels, or when the clearance to bottom of drum is lost. (Full).
MAJOR MODIFICATION...
only to the tub idea. Going to play with the idea of making another drum 50mm oversize to the tumbler drum, that is basically cut through at sea level. A bit like an old flour/sugar scoop.
with a simple large drain plug at the lowest point.
But that will be a few hours of pondering away yet.