Tiny motors on new grinders? - Page 7

Grinders are one of the keys to exceptional espresso. Discuss them here.
DaveC

#61: Post by DaveC »

buckersss wrote:how difficult is it to find out if grinders have a gearbox? i expect its really just a conical thing, no?
Just saw this... most small motors have 4 poles (adding poles reduces speed but has some undesirable effects) The slip speed is below the theoretical maximum so for 50 Hz, it's around 1300 ish for 60z around 1700 ish. if a grinder states the burrs spin at these sorts of speeds....it doesn't have a gearbox. Keeps it cheap, keeps it easy, and small induction motors are very inexpensive.

The Ceado E92 I have spins at 240 rpm, so must have a gearbox, the Olympus 75E slow speed "might" have had a 6 pole motor, and in short order Eureka got rid of it and introduced the Hi Speed version, undoubtedly to save money. If you can get hold of an Older Olympus 75E with the 900 rpm burr speed, it's a great grinder.

Ypuh

#62: Post by Ypuh »

BaristaBoy E61 wrote: image
I'd prefer this over single dosing.
I don't want a Decent

buckersss

#63: Post by buckersss »

DaveC wrote:Just saw this... most small motors have 4 poles (adding poles reduces speed but has some undesirable effects) The slip speed is below the theoretical maximum so for 50 Hz, it's around 1300 ish for 60z around 1700 ish. if a grinder states the burrs spin at these sorts of speeds....it doesn't have a gearbox. Keeps it cheap, keeps it easy, and small induction motors are very inexpensive.

The Ceado E92 I have spins at 240 rpm, so must have a gearbox, the Olympus 75E slow speed "might" have had a 6 pole motor, and in short order Eureka got rid of it and introduced the Hi Speed version, undoubtedly to save money. If you can get hold of an Older Olympus 75E with the 900 rpm burr speed, it's a great grinder.
Wow what a reply. Thank you. Do you think perhaps the motor on anfim grinders have more poles then, as opposed to a gearbox? On the Cody and Scody they turn at 750rpm at 50hz. I think the spii turns at 600 rpm at 50hz!

DaveC

#64: Post by DaveC » replying to buckersss »

Perhaps, I have never opened one up to see. Use the formula Ns=120f/P for the motor speed, deduct a little for slip and load, and you can discover the likelihood of Poles vs gearbox. This of course depends on the manufacturers motor speed rating being correct.

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cafeIKE
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#65: Post by cafeIKE »

1920 Model T 2.9L 20hp





2020 Audi 2.9L 444hp



Time marches ever forward.

buckersss

#66: Post by buckersss »

DaveC wrote:Perhaps, I have never opened one up to see. Use the formula Ns=120f/P for the motor speed, dedict a little for slip and load and you can discover the likely hood of Poles vs gearbox. This of course deoends on the manufacturers motor speed rating being correct.
Amazing. Thanks. If only it was that easy to get rpm stats on eureka grinders. I seen it suggested mine could be either 1440 or 1800

ira
Team HB

#67: Post by ira »

FWIW, if it's an AC motor with poles, 1440 at 50 hz would be 1728 at 60hz o maybe there's no difference.

Ira

PeterTheGoat

#68: Post by PeterTheGoat »

Here is my experience developing an electric grinder:

Motor size is constrained by packaging and cost considerations.

You are interested in motor torque, not power when choosing a drivetrain.

Larger diameter motor = more torque (this is simplified)
Larger diameter burrs need more torque
Burrs with more aggressive teeth need more torque
A small diameter motor that spins at high RPM can be geared down to give a lot or torque (case in point ARCO grinder).

The only thing that motor power really directly correlates to is grind speed. Because high power means high speed + high torque.
If you don't need very fast grinds (If your grinder is not designed for use in a busy cafe) then you do not need a high power motor. You need a slow one with high torque (think large diameter) if you have a big enclosure available or a small fast one that can be slowed down and torqued up with a torque multiplier (gearbox) - again; case in point ARCO grinder.

buckersss

#69: Post by buckersss »

PeterTheGoat wrote: The only thing that motor power really directly correlates to is grind speed. Because high power means high speed + high torque.
If you don't need very fast grinds (If your grinder is not designed for use in a busy cafe) then you do not need a high power motor. You need a slow one with high torque (think large diameter) if you have a big enclosure available or a small fast one that can be slowed down and torqued up with a torque multiplier (gearbox) - again; case in point ARCO grinder.
if you compare two grinders with the same sized burrs - and grinder A has a motor half as powerful as grinder B, but spins half as fast, id expect they have similar torque.

often times higher speed means higher power, but not necessarily higher torque.

@50hz 230V, the anfim spii spins at 650rpm and draws 720 watts. not high speed. hell of alotta torque though.