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AtlantaTerry
15-Apr-2016, 12:50
I have an idea for a project where I will be photographing items on a surface that rotates slowly and smoothly.

For the surface I'm thinking of starting off with my Ikea "lazy Susan" since it is fairly large and seems to rotate without any wobble. Or I could purchase from a hardware store the mechanism that makes a "lazy Susan" function then install it between a couple pieces of plywood.

But I need to be able to make the surface rotate extremely slowly. Possibly as slow a 1/4 RPM to 1 RPM. Maybe faster.

I own various power tools such as electric drills and a Dremmel. But I don't believe they work slowly enough.

In an ideal world the motor would have a dial where I could set the rotation speed. The maximum load would be only a couple pounds.

Also, how do I calculate something like gear reduction? I know if I have a motor with a small spindle that I can put something like a pulley on it then run a belt around the surface. Can't I by changing pulley sizes make the surface rotate faster or slower? We probably covered gear reduction in junior high shop class but that was way back in the '50s and I have forgotten most of it.

Where would I find a motor that would do the job? Money is an issue...

Thanks,
Terry

Jim C.
15-Apr-2016, 13:15
What you want is a DC gear motor, you can vary the speed of DC motor with the motor controller, eBay has all sorts of new and used Bodine gear motors
you'll have to get a controller ( basically a variable voltage DC power supply ) with the correct voltage for the motor.

You can also look into variable speed display turntables if you don't want to get into the nitty gritty of gear ratios,
search eBay for rotating display stand

Bob Salomon
15-Apr-2016, 13:15
Why not check out old turntables and see if one can be slowed down easily?

Sean Mac
15-Apr-2016, 13:18
Windscreen wiper motors often come with a reduction box built on. Scrapyard cheap.

Set it up to drive a piece of allthread as a "worm drive" for the slowest reduction. Let the allthread cut its mating teeth in a disc of something soft.

The reduction ratio is the ratio of the circumferences of your two pulleys. 3.142 x Radius Squared will probably ring a bell.:)

Drew Wiley
15-Apr-2016, 16:00
You need to look for gearmotors, with reduction gearing built into them. And no, at 25,000 RPM, a Dremel tool trying to drive a reduction gear would not be a good
idea. It would probably fry in about a hundredth of a second. Leave those things for doing root canals on meadow mice.

Taija71A
15-Apr-2016, 17:22
B&H sells 'Small' (9" Platter, supports up to 25 lb) Motorized Photography Turntables.
They come on sale quite frequently (< $100 USD).

The Rotational Speed is 1x Full rotation @ 1 to 2x RPM.

Kind regards, -Tim.

Emmanuel BIGLER
15-Apr-2016, 19:43
Hello from France

1 rpm motors are standard industrial products that you can buy on eBay!
For example those motors made in France (the speed is fixed)
http://www.ebay.com/itm/CROUZET-82344771-MOTOR-GEARED-230VAC-1RPM-/111803825772

You can buy the gears separately
http://www.ebay.com/itm/1-Reducteur-RAP-150-pour-des-Moteurs-/190375387776

So you juste have to chase on eBay close to your home and look for similar products.

thaakre
15-Apr-2016, 23:26
Why not a discoball motor?

el french
16-Apr-2016, 00:01
Surplus Center usually has a selection of AC and DC gear motors like this: http://www.surpluscenter.com/Electric-Motors/AC-Gearmotors/AC-Gearmotors/1-8-RPM-115-VAC-GEARMOTOR-2051788-5-1771.axd

Struan Gray
16-Apr-2016, 01:28
Butcher a clock. Use the second hand drive for 1 RPM. Change the photo-taking rate for other speeds.

B.S.Kumar
16-Apr-2016, 02:23
Butcher a clock. Use the second hand drive for 1 RPM. Change the photo-taking rate for other speeds.

That was my first thought, but:
a. most second hands move jerkily - how could smooth motion be achieved?
b. would a clock motor support a load of say a kilogram?

Kumar

Struan Gray
16-Apr-2016, 03:57
Kumar, I don't think there are general answers to that. A lazy Susan usually has a bearing, so they spin quite freely. You would have to find a clock that can generate enough torque, but the torque involved won't be that high. Ditto on the jumping second hand: you just need to find a sweep hand clock.

FWIW, *I* would do this by raiding my children's LEGO box. LEGO make nice compact low-speed high-torque motors, and they're designed to be used robustly. They can be controlled by everything from an on-off switch and a battery box to full-on microprocessor control. Gear trains and pulley systems are easy to rig up too. New equipment may break the budget here, but second hand is available.


PS: the OP might want to Google for astronomer's homebrew solutions to a motorised azimuthal mount. The rotational speed is even lower, but many of the rigs solve the same problems.

B.S.Kumar
16-Apr-2016, 06:10
Thanks, Struan, the LEGO sounds promising. It might be better than using a clock.

Kumar

Struan Gray
16-Apr-2016, 06:22
The Mindstorms motors are the most flexible in terms of connections and programming. But they are also the most expensive.

Easy to rig up a motor and a wheel with a tyre driving the lazy Susan by friction.

mdarnton
16-Apr-2016, 06:28
This place is totally unpredictable, since they have whatever they have, but a good look around their website is never wasted time: https://www.sciplus.com/ I see there's a little geared 3/5 RPM motor on their front page today, in fact, for $3.95!

My wife is always wary when I want to go there because I inevitably come out with a bunch of questionable junk that might someday be useful, maybe.

normanv
20-Apr-2016, 03:08
Surplus shed have geared motor with an output of 2/3 RPM. Their Ref M2106P price $8.50

Tracy Storer
27-Apr-2016, 12:44
Also, how do I calculate something like gear reduction? I know if I have a motor with a small spindle that I can put something like a pulley on it then run a belt around the surface. Can't I by changing pulley sizes make the surface rotate faster or slower?
For gear and belt drive pulleys, looks at circumferences. (diameter x pi) A pulley with circumference "2x" will spin at half the rate of the drive pulley of circumference "x" (the drive pulley goes around two turns to turn the driven pulley one turn.)
With gears, its the same, but go by tooth counts.
This is a big part of what you need to know to set up gear trains for thread cutting on a lathe, by the way.

Randy Moe
27-Apr-2016, 14:12
This place is totally unpredictable, since they have whatever they have, but a good look around their website is never wasted time: https://www.sciplus.com/ I see there's a little geared 3/5 RPM motor on their front page today, in fact, for $3.95!

My wife is always wary when I want to go there because I inevitably come out with a bunch of questionable junk that might someday be useful, maybe.

That place was more fun 30 years ago...

barnacle
28-Apr-2016, 14:15
Tracy - forget PI - it cancels out! Just compare the diameters.

Neil

Tracy Storer
29-Apr-2016, 14:24
Absolutely true, pi becomes a common denominator.


Tracy - forget PI - it cancels out! Just compare the diameters.

Neil

eli
5-May-2016, 20:36
You need an inexpensive barbecue spit turner, the kind that uses a pair of D cell batteries? You can most likely find one at a home center, like Lowe's or Home Depot, or a Walmart. I have one that I tried to use for a small project engine and it turned so slowly, with new batteries that I thought it was broken, but nope, it worked as the engineers begat it. This type motor has good tork and can 'spin' a fair amount of weight. Its also cheap.

AtlantaTerry
6-May-2016, 18:01
You need an inexpensive barbecue spit turner, the kind that uses a pair of D cell batteries? You can most likely find one at a home center, like Lowe's or Home Depot, or a Walmart. I have one that I tried to use for a small project engine and it turned so slowly, with new batteries that I thought it was broken, but nope, it worked as the engineers begat it. This type motor has good tork and can 'spin' a fair amount of weight. Its also cheap.

What a GREAT idea!

Thanks,
Terry

barnacle
7-May-2016, 08:38
The well known auction site and/or well known search engine both produce lots of hits for '1 rpm geared motor'. DC motors will produce a variable speed with voltage; AC motors will lock to the mains frequency.

Neil

AtlantaTerry
7-May-2016, 20:11
The well known auction site and/or well known search engine both produce lots of hits for '1 rpm geared motor'. DC motors will produce a variable speed with voltage; AC motors will lock to the mains frequency.

Neil

What's going on here? Why not just say Ebay and Google??

Thank you for the information, it is helpful.

barnacle
8-May-2016, 01:10
You're welcome.

I'm still newish here and feeling my way around referencing other sites. I don't want to derail your thread into a bunfest... My preference would have been to point directly to an example, but that certainly seems to be frowned upon.

With regard to your problem, geared AC motors with accurate speeds - or at least, usually consistent speeds - are quite common and inexpensive, and probably ideal to your requirement. If you need to control a specific speed other than one that comes out of the box, you are almost always better off with gears rather than electronics for continuous rotation, although with the right controllers stepper motors can be very precise - but they're expensive.

Neil

AtlantaTerry
8-May-2016, 15:00
You're welcome.

I'm still newish here and feeling my way around referencing other sites. I don't want to derail your thread into a bunfest... My preference would have been to point directly to an example, but that certainly seems to be frowned upon.

With regard to your problem, geared AC motors with accurate speeds - or at least, usually consistent speeds - are quite common and inexpensive, and probably ideal to your requirement. If you need to control a specific speed other than one that comes out of the box, you are almost always better off with gears rather than electronics for continuous rotation, although with the right controllers stepper motors can be very precise - but they're expensive.

Neil

As far as I know there is no rule against pointing out an example on eBay or anywhere else. I do believe there is a rule against pointing to where one is selling their own item on eBay.

Thank you for the information about geared motors. There are a kazillion on FleaBay, I just have no idea what might work for my purposes. (See my next note.)

AtlantaTerry
8-May-2016, 15:01
You need an inexpensive barbecue spit turner, the kind that uses a pair of D cell batteries? You can most likely find one at a home center, like Lowe's or Home Depot, or a Walmart. I have one that I tried to use for a small project engine and it turned so slowly, with new batteries that I thought it was broken, but nope, it worked as the engineers begat it. This type motor has good tork and can 'spin' a fair amount of weight. Its also cheap.

Today I dropped into my local Lowe's store to visit their BBQ section.

I found a motorized BBQ Rotiserie kit for about US $30 but very little technical information was printed on the outside of the box. I will be going to the manufacturer's website to see what I can find out.

Universal Rotiserie
Char-Broil, LLC
Columbus, Georgia USA
www.CharBroil.com
Item #9768102

Update:
OK, I went to the manufacturer's website and they fail to show a product with that model number. They do have a similar Model number: 9468102. Yet there is absolutely no information about the minimum or maximum number of RPMs! For a product that rotates, I would think that is important information, yet it is not there.

I did send them a query about the number of RPMs. Let's wait to see their reply.

http://www.charbroil.com/universal-rotisserie

Reply received: 2 RPM (only). So I would need to figure a way to gear it up or down to control the speed I want when I am creating my photographs.

150621

normanv
12-May-2016, 16:23
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Join Date:Jul 2010Posts:17




Re: Need a very slow motor (like 1 RPM).



"Surplus shed have geared motor with an output of 2/3 RPM. Their Ref M2106P price $8.50 "
20th April

One gets very pissed off when a suggestion is totally ignored.

AtlantaTerry
12-May-2016, 18:19
--------------------------------------------------------------------------------
Join Date:Jul 2010Posts:17




Re: Need a very slow motor (like 1 RPM).



"Surplus shed have geared motor with an output of 2/3 RPM. Their Ref M2106P price $8.50 "
20th April

One gets very pissed off when a suggestion is totally ignored.

I'm not ignoring your suggestion. I have been looking at ready-made devices that have variable speeds rather than try to build something myself.