I was reading a thread on Coffeesnobs about the Niche Duo @tompoland will know the one I mean. There was discussion about burr speed not making a difference, but it actually makes a huge difference. The problem is that the other grinders can’t really grind well down at the low RPM of the Niche Duo..Some try but their throughput can be 18g in 50 seconds, which in itself is problematic….all that extended time spent in the breaker zone.
When burrs grind coffee, a % of work is done by the burrs and some of the “milling” is done by the coffee rubbing against itself. It’s why grinders produce a much coarser grind for the same setting when beans are fed through a few at a time. I like naming things and this is something I call “burr packing”. Optimal packing is where coffee “milling” against itself is reduced to the absolute minimum. This reduces fines and gives a better grind, something that can actually be tasted in the cup.
The Niche uses a number of clever mechanisms to not only be able to grind at an acceptable rate with optimal burr packing at the speeds it runs at…but also clear the chamber and the burrs themselves even when close to turkish.
For the 83 mm burrs used, I found what I felt was the optimum speed range at the voltages it will work in to give optimum packing and reasonable grind speed. Of course it could have been speeded up and ground much faster, there was plenty of “torque” to do that, as the green coffee grinding has shown. However, it wasn’t desirable from the grind quality perspective.
So a grinder running at 1300 to 1400 rpm, starts at a huge disadvantage in getting the best from it’s burrs, many go down to 900 or 800, but that’s not slow enough. problem is any slower and they run into torque limit problems (brushless and brushed motors) and clearance/grind time problems. To overcome these things they need the complications of an inline planetary box which Niche (martin) are extremely good at. Instead the competitors vary the motor speed, which limits torque and is the reason many (I won’t mention names) won’t go below 800 or 900 rpm.
As far as the mainstream manufacturers are concerned, for the big commercial grinders they don’t care, speed is king and AC induction motors are cheap, easily available, robust and…run at 1350 ish rpm ant 50Hz. Sure you can get multipole motors, but the weight/price and size increases sharply.
the above mainly affect espresso, and for filter a slower grinding speed generally is beneficial…I am sure filter could even go slower, but the additional complexities, would introduce more cost and don’t stack up for the extra benefits you would get….which would be marginal.
