Re: Motors: was Re: [automata-forum] WIP "The Politician" Eye Mechanism


Gus
 

Hi Jim,

DC negates the need for a power outlet, does not need a wall, can be in the middle of a room for example, doesn't have a trailing cord etc. That's why I prefer that option. DC motors from what I can see are easy to source too. There is an electronics store here which has a range of geared motors, AC and DC, and plug in speed controllers. Makes selection easier than an online order from overseas suppliers. Initially, I will set up the "engine room" as manual, see how much effort it needs to operate everything, then find a suitable motor. It may be that the input speed and torque is easier to find than I am supposing. Then the motor RPM can be ordered to suit. All grist for the mill !
By the way, what is a "wall wart", a power outlet on a wall, or something else ?

Regards,
Gus 

Keep Safe

On 2 Jul 2020, at 12:47 pm, Jim Coffee <jim@...> wrote:

Hi Gus...
  • Regarding the fuses that I use:  I don't use fuses, rather I use circuit breakers.  3 amp.  They don't draw any power.  They just sit there and if the amperage exceeds 3 amps they disconnect things.
  • Regarding motors: I've only powered about 7 automata...so have limited experience.  
    • I've chosen to use gear motors because they have built-in speed reduction.  They provide excellent torque and I only need low speeds.
    • I've chosen to use 120 vac motors because (in this country) 120 vac power is universally available.
    • I've chosen to NOT use motors that require some sort of 'wall wart'.  This means I've chosen to not use 12 v or 24 v etc. motors.
However...your queries and thoughts are provoking my thoughts...and I am questioning my own solutions.  For example...you keep mentioning that you want DC.  I wonder why?  And then I look at variable speed motors and find that brushless DC motors are available and that they work well.  I also find that servos can be speed controlled at continuous revolutions.  So what I am doing right now is (re)investigating motor solutions.  
I agree with you that an automata has a 'golden speed'...a speed that is perfect for it.  So I understand you wanting variable speed motors.
This motor thread will go for a while I think.  I hope others will join this conversation.  Between us all we have collective knowledge that is greater than any individual.
I appreciate this forum and the opportunity to learn and to share.
Regards from San Diego, California
-Jim Coffee-

On Tue, 30 Jun 2020 at 22:26, Gus <klekner@...> wrote:
And to you Jim,

Thank you for your comments and help with motor information and sources. Until now, all 15 automata built have been manual, driven by hand. I have found that they have an optimum crank speed, all different, even though governed by a  gear train. I expect that this will apply equally to motor driven mechanics. Having no experience with motors, and to avoid the purchase of a number of them, I am considering an external  speed control,  but not decided anything yet. With the exception of a gear motor being DC. In a similar vein, the cams would be much smaller blank than I am used to working with. All these aspects, and others, have to do with having to think of every single component of the total concept during the building, and is dictated by the absence of working drawings and specific planning. 
Would you discuss your use of a fuse, what type, does it cut in on overload, and also if there a change in the load, ie a component disconnects ?

Not happy to read that the virus is spreading fast and furious in your country !

Regards,
Gus

Stay Safe

On 30 Jun 2020, at 12:35 pm, Jim Coffee <jim@...> wrote:

Greeting Gus...
Very ingenious and inventive.  I believe that I've been able to follow all of the motion paths and that I understand what you have created.  What a joy to see an automata like this under construction!  Your mechanism looks solid and functional.  Thanks very much for sharing this!  Please keep posting your progress.

Regarding variable speed motors...I have little experience.  A top-level question that I have is "why" do you want a variable speed motor?  In the end, do you want a single-speed motor and you are going to experiment with speeds until you are pleased?  Or something else?
If you are just going to experiment you could use something that you already have laying around like a variable speed electric drill. Or, a sewing machine motor and pedal.
In the end, I suspect that you will want a gear motor.  Gear motors come both constant speed or variable speed.
You will notice that the world of variable speed gear motors is smaller.  
And something that surprised me...a sewing machine motor and foot pedal combination is relatively inexpensive

Thanks again for sharing
-Jim in San Diego-


On Sun, 28 Jun 2020 at 16:23, Gus <klekner@...> wrote:
The mechanism has two parts - a hinge section which is fixed to the hollowed out head, and the eyes which are part of a device to move them side to side and up/down. The eyes section connect to the hinge by a clamp, which allows adjustment to the eye sockets. The hinge has a return spring eliminating the need for hard wire controls, in favour of cable/cam.



The eye mechanism front view



Eye mechanism rear and cable connections



The assembly fitted to the head



The face, eyes fitted. I have made a video of the movements, but not able to post here. 



Jim,
Thanks for your comments. I would want to use a speed controller for the motor. Have you used speed control, and if so, is there  power loss ? 

Regards,
Gus

Keep safe


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