Interesting, the original M3 planned on using a set of commercial conical burrs that went out of production at an inopportune time. A $20,000 problem with an interesting answer, custom cut water jet burrs for < $100 each... mind you 200 burr sets seem more than I would need right now.

http://www.ashlar.com/sections/ga...alab/versalab.html

Mark

pdx wrote:Why not chain drive? Seems simpler than gear drive. If you use bike chain & cogs you could cheaply & easily change out drive parts.

Not bad for prototyping being able to change things quickly, however belts are quieter.

Mark

I think that it's time to get with your local street-racing gear heads. I'll bet that they have some old tranny parts that'd make driving burrs quiet and painless.

The electric skate board groups have plenty of nifty DC motors, HTD belts and pulleys. I'm thinking that the starting torque of a dude on a skate board is less than coffee between two burrs, but I could be wrong. Hate to strip all the bumps off the belt. (Guess that's the advantage of a V-belts).

Anyone have any definative rating of the starting torque of a grinder?

mark

The versalab uses this motor.

Ben: Thanks this is sufficient to get some rough guesses to the amount of power needed by a DC motor to spin a conical burr.

Since Versalab draws about 120 watts, we can assume they run at about 110v (or so) on the motor. They also use a step down belt which will improve the torque.

Volts Amps RPM Oz-In
90v 0.78 1725 36
130v 1.0 2500 50

Estimate:
110 0.89 2100 43

2100/4 ~= 500 rpm
43 * 5 ~= 215 oz-in torque

From the Versalab thread:

Abe Carmeli wrote:Let me try to sum it up in a nutshell:

Pros

1) Near perfect distribution
2) No clumps
3) Better grind quality, resulting in overall better quality in the cup, particularly with high growth acidic coffees.
4) Minimal amount of stale coffee caught in the grinder burrs & housing
5) Practically no coffee is caught in the funnel
6) Esthetically outstanding & unique

Cons

1) No dial scale, though one can fabricate a half ass scale, with hilarious consequences. I'm working on putting together a laser etched scale. (with help from Sean Lennon & Lino). If we are successful, I hope to make it available to all who request it.
2) Takes longer to grind
3) May be too slow & inconvenient when entertaining a party
4) Requires the Barista to attend to the grinder as it grinds
5) Prone to stall if it is not fed properly
6) Requires slightly more time to maintain the grinder - weekly pulley cleanup

So, pretty clear that a stronger motor spinning faster would solve 2, 3, 5. It may however also negatively affect things, but heck it's a starting point. (More heat, larger, higher price, etc).

So need more than:
2000/4 == 500 rpm
43 * 5 == 215 oz-in torque

I also noticed I was mistaken in thinking there was a bottom thrust bearing in the Versalab, the top bearing does it all. Nifty in that the bottom sweeps perfectly clean with nothing to catch on.

Mark

Here is the Jet Grinder with internal bean feeder, active cooling grind chamber, organic led display and magnetic clamping portafilter holder. Motor and control unit are mounted below the counter. Pricing yet to be determined.



Mark

Very nice! One thing not mentioned as an advantage of the hybrid burr set used in the Versalab is that the flat burrs used for the fine stage are relatively insensitive to slight radial runout, whereas a conical burr set won't be.

One problem with the Versalab is the amount of popcorning. I'd consider adding the kind of shallow auger before the breaking stage that the conical Mazzers now use.

Best,
David