That looks like it should work pretty good with granulated rubber...
How long do you suppose the cloth belting material would last with dirt?
That has always been my hang up with trying to build a small conveyer like this one, finding the right endless belt that is soft enough to roll up on the edges to keep the material in the middle, will grip a 1" drive roller well & be durable enough to last moving abrasive materials - like dirt & sand.
I ordered some 2" width belting material from McMaster that was 060 thick, it was too stiff! Had to tighten the belt alot to get it to grip on the drive roller, which then made the 180rpm spur gearhead motor too weak to propel it. And sometimes the "stapled" splice would stop on the drive b/c it would not grip the metal surface.
I've seen a few european scale minature conveyers that seem to function perfectly, But I can't find any information on what materials were used, nor what right angled gear motors at what rpm.
The Bruder conveyers work pretty good, but they are a bit short to do much of anything with. I have a couple of them, I may try stacking two or three together & using one or two continuous servos to propel them.