Slow, torque-ey motors

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Slow, torque-ey motors

#1  Postby ScholasticSpastic » Apr 12, 2016 4:34 pm

I need a small electric motor which gives me reasonable torque (dealing with a ~1kg mass, vertically lifted) at <0.01rpm. Anyone have any ideas? I've been thinking about how difficult it would be to cannibalize some off of used telescope tripods, but I think those require more electronics than I'm willing to mess with. I just want something I can switch on and let it go through a few rotations over a few days, then switch it off.
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Re: Slow, torque-ey motors

#2  Postby ScholasticSpastic » Apr 12, 2016 4:36 pm

If I can get something workable, I'll show you my results. It'll take a few months from assembly to finished product, though.
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Re: Slow, torque-ey motors

#3  Postby Scot Dutchy » Apr 12, 2016 4:43 pm

Use thyristors for regulating the motor.
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Re: Slow, torque-ey motors

#4  Postby ScholasticSpastic » Apr 12, 2016 5:48 pm

Scot Dutchy wrote:Use thyristors for regulating the motor.

Which sort of electric motor, regulated by a thyristor, will give me sufficient torque to lift a 1kg object off the ground? Because I've heard that typical electric motors lose torque when you damp their current and I imagine that going to <0.01rpm by that method would make most motors practically useless.
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Re: Slow, torque-ey motors

#5  Postby Scot Dutchy » Apr 12, 2016 6:16 pm

ScholasticSpastic wrote:
Scot Dutchy wrote:Use thyristors for regulating the motor.

Which sort of electric motor, regulated by a thyristor, will give me sufficient torque to lift a 1kg object off the ground? Because I've heard that typical electric motors lose torque when you damp their current and I imagine that going to <0.01rpm by that method would make most motors practically useless.


I only remember years ago when building a block system for a model railway layout and thyristors have the ability to slow down the motor without losing torque. Sorry I cant remember any further (it is 40 years ago) but it worked a treat as the locs would slow down very life like without stalling which happens if you use resistors. They are used to control electric motors in real trains as well because of the same reason.
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Re: Slow, torque-ey motors

#6  Postby tuco » Apr 12, 2016 6:16 pm

How small?

[Reveal] Spoiler: sorry!


oh slow .. forget it
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Re: Slow, torque-ey motors

#7  Postby ScholasticSpastic » Apr 12, 2016 6:44 pm

Scot Dutchy wrote:
I only remember years ago when building a block system for a model railway layout and thyristors have the ability to slow down the motor without losing torque. Sorry I cant remember any further (it is 40 years ago) but it worked a treat as the locs would slow down very life like without stalling which happens if you use resistors. They are used to control electric motors in real trains as well because of the same reason.

Cool! :thumbup:

I will look into thyristors further, and learn something.

I honestly have no idea what I'm doing at this point. I have a desired outcome and am trying to work from there to parts and assembly via the least-technical path I can find. I'm not even going to try to pass myself off as some sort of electronics whiz, because that would be a silly thing for me to even attempt to pretend to be.

What I would LOVE would be if there were somewhere that you could simply buy the desired assembly without having to put it together yourself. Because then that's what I would do. Which is why I mentioned, previously, cannibalizing telescope mounts.
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Re: Slow, torque-ey motors

#8  Postby ScholasticSpastic » Apr 12, 2016 6:45 pm

tuco wrote:
oh slow .. forget it

:lol: Yeah. I would have to gearbox the hell out of something like that.
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Re: Slow, torque-ey motors

#9  Postby tuco » Apr 12, 2016 6:47 pm

It was brain fart sorry .. you know this project, we have two hints already ;)
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Re: Slow, torque-ey motors

#10  Postby laklak » Apr 12, 2016 6:50 pm

A bucket full of water, over a pulley, with a small hole in the bottom.
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Re: Slow, torque-ey motors

#11  Postby ScholasticSpastic » Apr 12, 2016 6:51 pm

laklak wrote:A bucket full of water, over a pulley, with a small hole in the bottom.

I actually thought about this. It's too fast. (Not joking!)
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Re: Slow, torque-ey motors

#12  Postby Adco » Apr 12, 2016 6:51 pm

A geared DC motor can do the job. You can get very low gearboxes running off small motors. Also, you can cascade the gearboxes to give extreme ratios. I have a 100:1 gearbox at work the has a 12VDC motor driving it. The motor runs fine at low voltages as well. I have run it off 3VDC without a problem. At the low speed you cannot stop the shaft from turning with a pair of pliers. Imagine putting it into another 100:1 gearbox! You could lift a ton with it. And very slowly.

My local supplier Mantech, has a range of geared motors. Most of them from the Far East. http://www.mantech.co.za. Have a look at their range. Got to their page then do a product search for components, then electro-mechanical, then motors. You should be able to find something worth following from your local supplier.

You should be able to control the speed with a small variable switch mode power supply like the type that Meanwell sells.
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Re: Slow, torque-ey motors

#13  Postby ScholasticSpastic » Apr 12, 2016 6:53 pm

tuco wrote:It was brain fart sorry .. you know this project, we have two hints already ;)

The disembodied, genetically modified organs in a vat are for another secret project. I have several secret projects. The one with the organs I will probably never be able to tell you about. The one this thread's about I will be able to show you a movie of when it's done.
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Re: Slow, torque-ey motors

#14  Postby ScholasticSpastic » Apr 12, 2016 6:55 pm

Adco wrote:A geared DC motor can do the job. You can get very low gearboxes running off small motors. Also, you can cascade the gearboxes to give extreme ratios. I have a 100:1 gearbox at work the has a 12VDC motor driving it. The motor runs fine at low voltages as well. I have run it off 3VDC without a problem. At the low speed you cannot stop the shaft from turning with a pair of pliers. Imagine putting it into another 100:1 gearbox! You could lift a ton with it. And very slowly.

My local supplier Mantech, has a range of geared motors. Most of them from the Far East. http://www.mantech.co.za. Have a look at their range. Got to their page then do a product search for components, then electro-mechanical, then motors. You should be able to find something worth following from your local supplier.

You should be able to control the speed with a small variable switch mode power supply like the type that Meanwell sells.

:thumbup: This is good information. Is their customer service good? Do they have application specialists that I can bug with questions? Don't bother answering, I will find this stuff out myself.

Using my own Google-fu when I don't really know what I'm doing is not a good idea. :shifty:
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Re: Slow, torque-ey motors

#15  Postby Adco » Apr 12, 2016 7:04 pm

Well, they are a local supplier so I would not try and use them with you being in the US. I just wanted to show a sample of what you could use on your side. There must be a heap of suppliers that will have the same stuff near you.

I would stick to a DC motor. If you gear it down enough the power supply needed will be small and simple. AC motors are generally larger and need more tricky controls. With DC you just vary the voltage. Easy. I saw one of the motors has a 3000:1 ratio. You could use that as a winch to pull your car out of the mud!
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Re: Slow, torque-ey motors

#16  Postby Adco » Apr 12, 2016 7:07 pm

And, if you wind your string/rope onto a small shaft, you get even more torque. How far do you want to lift the 1kg?

With enough gears and a good anchor you could stop the earth's rotation.....
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Re: Slow, torque-ey motors

#17  Postby ScholasticSpastic » Apr 12, 2016 7:15 pm

Adco wrote: How far do you want to lift the 1kg?

That's a tough question. I haven't designed the armature yet. I plan to design it around whatever I find motor-and-gear-wise. Can I get away with batteries or will I need a cord? That'll change the armature design. And the armature design will determine how much mass really needs to be lifted and how high. Of key importance for me is that I manage to obtain very, very slow motion over a period of days or, preferably, weeks. I want movement so slow that you can't see it, and I want to be able to move my load at that speed.
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Re: Slow, torque-ey motors

#18  Postby Adco » Apr 12, 2016 7:26 pm

Batteries can be dodgy. Especially if you want it to last for weeks. A proper DC regulated PSU will be better. Also, as the batteries go flat, the speed will change.

What about driving the motor with a start-stop effect. For example, turn it on for 5 seconds, turn it on for 5 seconds. If the ratio is large enough, you might not notice it. You might be able to set the on/off ratio at 1 second on, 5 seconds off. Small steps. Depends on what you are lifting.

There are many ways to solve the problem, more info is needed to come up with a final design.

Another way is to use a stepper motor. Not as strong as a normal DC motor but if the gearing is well chosen it could work. Much more complicated because you will need a steeper motor controller. Not a train smash though.
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Re: Slow, torque-ey motors

#19  Postby ScholasticSpastic » Apr 12, 2016 7:36 pm

I keep seeing servomotors being mentioned when very low speeds are required. What would I need for the most basic sort of servomotor setup? Is this something I need to be electronics-savvy to do? Because that's something I'd like to avoid. I would prefer something I can switch on for a few days and forget about while it does its work, and then switch off when it's done. Wikipedia says they have sophisticated controllers, which is very off-putting for me.
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Re: Slow, torque-ey motors

#20  Postby ScholasticSpastic » Apr 12, 2016 7:38 pm

Adco wrote:You might be able to set the on/off ratio at 1 second on, 5 seconds off. Small steps. Depends on what you are lifting.

This feels circuit-board-ey to me. I'm trying to avoid circuit boards. I want to link up motor(s), shafts, gears, and possibly pulleys, flip a switch, and make it go. Doing circuit board stuff would require an expensive expansion of my tool collection.
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