I'm hoping to get an EFM, AHS or A-A at some point. Not so clear to us newbies is that untended operation is limited not by stoking but by ash removal. I'm wondering if anything can be rigged to remove ash 'semi-automatically.' I haven't seen any ash removal systems.
To design an ash remover, I would think that you would first consider how long you are comfortable letting one of the above boilers go untended.
As one with no stoker experience and not knowing any better, I'd use a week as the emptying interval. As a 55gal drum has about 7 days of coal (~450lbs) and will produce about 90lbs of ash, I'd use that as the design capacity. Figure a galvanized garbage can as a convenient receptacle.
Any ideas; feed augur? Ash hopper on a EFM-type retort in reverse? Step down pit in basement?