How is countertorque fought ?

[Externet]

The stem body with the motor, gears and batteries does not counter-spin in this stirrer gadget, it still manages to revolve the thick sauce/soup.  How is it achieved ?

 

[swansont]

The case is opaque. How can you be sure there is no counter-rotating mass inside?

[koti]

36 minutes ago, Externet said:

The stem body with the motor, gears and batteries does not counter-spin in this stirrer gadget, it still manages to revolve the thick sauce/soup.  How is it achieved ?

 

The whole thing spins, check the video below. Even if it didn't and the case would be like you proposed, the initial torque would be very low and rotation speed would be low so the thing might as well spin without the top part moving (which is not the case ofcourse)

 

Also...there is no way that this stirrer could cope with the thickness of my Spaghetti Bolognese sauce. Crappy product

Edited December 23, 2017 by koti

[Externet]

50 minutes ago, swansont said:

The case is opaque. How can you be sure there is no counter-rotating mass inside?

I see a power switch, 4 cells holder, shroud, gearmotor? :   ¿?    I do not have one to dismantle.

[John Cuthber]

I see two feet that rest on the bottom of the pan providing friction and hence the torque.

What I don't see is "a problem to address"

.

[swansont]

6 minutes ago, John Cuthber said:

I see two feet that rest on the bottom of the pan providing friction and hence the torque.

What I don't see is "a problem to address"

.

They're all rotating, but one has an extension toward the center which doesn't have to.

[John Cuthber]

OK, I see 3 feet resting on the pan, providing friction...

[Externet]

There is no 'problem to address'  It is about understanding why the stem does not spin enough  leaving the legs stationary.  The 'providing friction'  by the 3 feet against the bottom of the pan would promote the opposite effect, causing the stem to turn. The more friction from the feet, the more the countertorque would make the stem spin instead of the legs.

From observation, the extension towards the center is to provide thorough sweep of the 'sauce' and avoid areas not swept that may overheat/stick. The feet and legs do not provide much stirring; that extension appears doing most of the work. 

Another style ---->  https://www.uutensil.com/products/stirr-automatic-pan-stirrer-bright-colours

 

Edited December 23, 2017 by Externet
Better link

[swansont]

32 minutes ago, Externet said:

There is no 'problem to address'  It is about understanding why the stem does not spin enough  leaving the legs stationary. 

It looks like it's all spinning at the same rate. 

[koti]

Since the whole thing spins I presume it gets its rotation from a motor producing vibration in which case there's virtually no torque anywhere (at least not any noticible torque) If this thing spins due to vibration produced by that motor, its another reason that it would most likely fail to cope with my thick Bolognese sauce.

 

Edited December 23, 2017 by koti

[swansont]

10 minutes ago, koti said:

Since the whole thing spins I presume it gets its rotation from a motor producing vibration in which case there's virtually no torque anywhere (at least not any noticible torque) If this thing spins due to vibration produced by that motor, its another reason that it would most likely fail to cope with my thick Bolognese sauce.

 

If it starts rotating, a torque is required.

 

[koti]

1 hour ago, swansont said:

If it starts rotating, a torque is required.

 

Hence I noted „noticeable torque” I’m fairly sure the torque produced by the vibration which propells this thing to spin is miniscule.

[arc]

Torque in these situations is usually provided by an eccentric movement of a adequate mass somewhat akin to a flywheel on an offset input shaft. It would vibrate considerably if connected directly to the motor shaft. This one probably utilizes a considerably sizable gear reduction before the eccentric that reduces what would be noticeable shaking. The viscosity of the liquid dampens or reduces the remaining gyration to just the slight wander that the device makes around the pan.

[arc]

Just viewed this demonstration without the soundtrack masking the device in action. It sounds like the eccentric mass is directly attached to the motor shaft and is spinning at the same RPM as the motor. It is likely off center to the shaft by a very small degree from what the video demonstrates.

 

[John Cuthber]

14 hours ago, Externet said:

The 'providing friction'  by the 3 feet against the bottom of the pan would promote the opposite effect, causing the stem to turn.

So, in the limit, if I increased the friction by gluing the feet rigidly to the pan, you would expect it to turn?

 

There are 4 torques involved here, they have axes coinciding with the 3 feet, and the stem.

[Externet]

Well... found how it works from a 'tear down' video.

There is no rotation at the 'waist line' of the stem. The gadget walks from vibration due to an excentric weight at its motor shaft,  the whole thing turns in one piece, legs are fixed, there is no gears.

Jump to time stamp 5:40  :

 

[koti]

1 hour ago, Externet said:

Well... found how it works from a 'tear down' video.

There is no rotation at the 'waist line' of the stem. The gadget walks from vibration due to an excentric weight at its motor shaft,  the whole thing turns in one piece, legs are fixed, there is no gears.

Since the whole thing is rotating and it showed in all the previous videos, that is kind of obvious isn't it.