When i was in highschool i cut,welded and did the lathe work to build a giant hammer mill.
I made the hammer mill from 1 cm thick steel( half an inch) ,had 36 hammers and the motor... was 11 KW motor ,3 phase and 3000 rpm conected in star( i think,had 1500 rpm conected the otther way ).
It crushed whole beef bones to dust .
The electric motor weighted like 100 kgs or more and the whole machine i think less than a ton.
When i sold it,i got the buyer in my metalic shack where the hammer mill was and wasnt fixed with screws in the concrete foundation .
I throwed 2 large beef bones into the chopper,it crushed them in a second then i stopped the machine and it started to vibrate and jump a little .
It made the ground shake along with the whoole metalic shack and the buyer was soo skared it wanted to flee but he couldnt find the door
.
He finally bought it .
As a wood chipper i have an electric one thats small ,just 3 hp( 2,8 kw) but its geared for torque and it chops easily 2 inch thick branches or firewood.I payd only 150 dollars on it and im verry pleased with the purchase.Its made in China and altough its not a professional wood chipper i use it almost as a professional one.Made a few cubic meters of wood chips with it.