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djr777
Premium
join:2005-01-25
Pacific Grove, CA

Need help slowing down this electric motor.

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You may remember this older post about a rock tumbler.

»My daughter would like this home improvement...any ideas!?

...after many delays and a career change and back to college we finally got to it.

I was going to throw this old cabinet away but my daughter suggested we could use it. We drilled holes in the sides and glued sockets in for the 7/16 shaft on the rollers.

The trouble is even with 6 containers of rocks it still spins to fast. I need to slow it down to get a tumbling action.

Is there a way to add a speed control to this motor?
...or...
how big a pulley would I need to make a difference, can a pulley even be added?

Safety thought. Any reason i cant use this cord off an old lamp for this motor? The motor didn't come with a cord. But I had one laying around. I will eventually tape it up.

Any Ideas?

Thanks again.
--
...there will be an answer. let it be


rockotman
...Blown On The Steel Breeze
Emerging Research
join:2000-08-06
DSotM
kudos:2

1 recommendation

A pully system would work, but it doesn't look like you have room for it in the box.

The speed ratio is drive pully diameter (in this case, the gear) divided by driven pully diameter.

At 1650 rpm, if you wanted to slow the rpm of the tumbler rollers down to 275 rpm you would need to put a pully on the rollers that was 6 times the diameter of the output gear on the motor. Given that the jars look to be about 4 times the diameter of the rollers, that would give the jars a rotation speed of about 68 rpm, which is a little over 1 rotation per second - about right for tumbling.

That gear looks to be about 1" in diameter, so the pully on the tumbler shaft would have to be about 6" in diameter.

But it doesn't look like there is enough room for 6" pullies on the tumbler shafts.

Do you have room for another shaft; then you could put the larger pulley on that shaft, and use yet another pully on that shaft to drive the belt that drives the rollers. This may give you adequate room for the larger pully.
--
Shine on you crazy diamond...


djr777
Premium
join:2005-01-25
Pacific Grove, CA

2 edits
Thanks rockotman,

There is about 9'' in the back behind the rollers.

A 6'' pulley would not fit on the rollers but i could raise up the motor to enable a 6'' pulley on the motor, would that work?

I have 4 of these heavy bearings that I could install on the belted rollers which would put more of a load on the motor because they don't turn all that easily. I might try that tomorrow. I wonder if that would slow it down enough?
»www.thebigbearingstore.com/servl···e/Detail

Thanks for your ideas.
--
...there will be an answer. let it be


Raphion

join:2000-10-14
Samsara
Reviews:
·Verizon FiOS
reply to djr777
This place has a great selection of pulleys, belts, bearings, and motors »sdp-si.com/eStore/

If you can't get that motor to work, they have some really nice, very low speed (even down to half a revolution a minute) DC gear motors. You'd need a DC power supply for that obviously though.


nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
Reviews:
·Charter
·voip.ms
·surpasshosting
reply to djr777
You could try and slow it down with pulleys. You could try and slow it down with a triac controller ($).
1st choice for this job would be a DC gear motor.

BTW, the cord isn't acceptable. You need a ground.
--
Looks like Reverend Wright got his wish - God Damn America.
Nancy Pelosi - House Minority Leader 2010
Harry Reid - Senate Minority Leader 2010

scross

join:2002-09-13
Cordova, TN

2 edits
reply to djr777
AC motors run at fixed speeds by design, usually at some multiple of line frequency, which is why you see two different speeds printed on it. You might be able to slow this one down with some fancy electronics, but that would be expensive and might even cause the motor to overheat or burn out. DC motors are really what you need when you want slow or variable speeds.

The pulley option is your best bet. From the looks of things you could probably drop your speed by maybe 50% if you could switch to a smooth belt, remove the sprocket from the motor and just put the belt directly on the shaft; this is because the shaft looks to be about half the diameter of the sprocket. You'd have to have some way to maintain good tension, though - maybe via a pivot and a strong spring attached to the motor mount. Doing this allows you to pair it with a smaller pulley - maybe one that will actually fit inside your box.

You don't want to do anything to mechanically overload the motor just to slow it down, because it will just burn it out prematurely - maybe in a matter of minutes or even seconds. It might trip the breaker, too, or shut down on thermal overload protection, if it has it.

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel

1 edit
reply to djr777
The simplest thing would be to get one of those AC gear motors such as the ones from microwave oven turn tables.

Then use pulley ratios to fine-tune the speed.

Or is that a bit too slow? Such motors are available in a variety of different speeds though.

That type of motor would be perfect for this application though. More than enough torque and very quiet.


djr777
Premium
join:2005-01-25
Pacific Grove, CA
reply to Raphion
said by Raphion:

This place has a great selection of pulleys, belts, bearings, and motors »sdp-si.com/eStore/

If you can't get that motor to work, they have some really nice, very low speed (even down to half a revolution a minute) DC gear motors. You'd need a DC power supply for that obviously though.
I would like to keep it simple
I'm looking at the possibility of DC but I haven't worked with one before.
Thanks
said by nunya:

BTW, the cord isn't acceptable. You need a ground.
If I find a 3 wire where do you recommend i ground on on the motor?

Thanks

said by scross:

You don't want to do anything to mechanically overload the motor just to slow it down, because it will just burn it out prematurely - maybe in a matter or minutes or even seconds. It might trip the breaker, too, or shut down on thermal overload protection, if it has it.
I don't want to overload this motor but I am pretty sure that it is thermal protected which means that it will shut off if it gets too hot, is that right?

Do you think that if I use those bearings it will put too much strain on the motor?

Thanks

said by TheMG:

The simplest thing would be to get one of those AC gear motors such as the ones from microwave oven turn tables.

Then use pulley ratios to fine-tune the speed.

Or is that a bit too slow? Such motors are available in a variety of different speeds though.

That type of motor would be perfect for this application though. More than enough torque and very quiet.
I'm looking at all my options. I looked at those little motors but I'm not sure they could handle the load but I'm still looking at them.

Thanks
--
...there will be an answer. let it be


rockotman
...Blown On The Steel Breeze
Emerging Research
join:2000-08-06
DSotM
kudos:2
reply to djr777
said by djr777:

A 6'' pulley would not fit on the rollers but i could raise up the motor to enable a 6'' pulley on the motor, would that work?
No. To reduce speed, the larger pulley has to be on the driven shaft, not the driving shaft.
--
Shine on you crazy diamond...

scross

join:2002-09-13
Cordova, TN
reply to djr777
I don't know about the bearings, but anything you do that artificially loads and slows an AC motor will eventually cause it to overheat, because the AC continuously cycles at 60 Hz and what it can't turn into motion will instead turn into heat. Also, the motor itself has to maintain a certain minimum speed in order to keep air flowing over it; otherwise it will overheat. You will probably run into a situation where it either runs at around it's expected speed, or it doesn't run at all and just sits there and hums, cooking all the while.

Also, the "-AOT" in the model number leads me to believe that it may be an "air over" motor, meaning that it expects to be in an air stream or driving a fan or blower which keeps it cool. If true then it will probably overheat without that, whether overloaded or not.

It may very well have thermal overload protection, but since this isn't stated on the label and I can't find a spec sheet for it then I can't say for sure. Even if it does, every time it overheats the insulation inside cooks a little and leads it a little closer to death. And don't rock tumblers need to run for hours and hours, maybe even continuously for days? Do you really want to leave it unattended for long periods, overloaded and shutting down all the time, maybe even smoking or starting a fire? Perhaps I'm being overly cautious but that would definitely concern me.

scross

join:2002-09-13
Cordova, TN

1 recommendation

reply to rockotman
said by rockotman:

said by djr777:

A 6'' pulley would not fit on the rollers but i could raise up the motor to enable a 6'' pulley on the motor, would that work?
No. To reduce speed, the larger pulley has to be on the driven shaft, not the driving shaft.
Agreed. Think about it for a second. A 1-inch diameter pulley on the driving shaft has to turn about four times in order to move the belt one foot. A 4-inch pulley only has to turn about one time, meaning it effectively multiplies the speed by about four. You don't get a free ride, though, because what you gain in speed you lose in torque (power). The reverse is true for pulleys on the driven shaft.

Here's the math:

Diameter = 2 * Radius
Circumference = 2 * Pi * Radius = Pi * Diameter

For Diameter = 1, Circumference = Pi = 3.14
12 inches divided by Pi inches = 12/3.14 = approx. 3.82 turns

For Diameter = 4, 12/12.56 = approx 0.95 turns

If you tell us what RPM you are targeting then we can no doubt calculate the pulley size(s). Also, for V-belts they make split pulleys which come in standard sizes but can be adjusted in or out in order to move speeds up or down. For example, a 4-inch split pulley can be adjusted from anywhere down to the shaft size (which I'm assuming is about 1/2 inch here) up to 4 inches, or anything in between.


djr777
Premium
join:2005-01-25
Pacific Grove, CA

1 edit
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Thanks scross,
Its becoming painfully obvious that I haven't messed with pulleys and motors before, but hey, I can make a mean steak. That is if you like onions, jalapenos, black pepper and garlic salt sauteing into the steak as the fat drips into the simmering coals below and sends up small explosions of lustrous aromas that bring neighbors climbing fences and parachuting into my back yard...

Here are some more pics.
There is about 8" in the back.
I could possibly put small pulleys on the two rollers.
I could possibly add one extra roller with a pulley as rockotman mentioned.
or maybe I could try this 3 speed motor. I called the company to find out what the lowest RPM was and he said to check back in a couple days and they will add that info to the website.
»www.surpluscenter.com/item.asp?i···electric

Any Ideas?
--
...there will be an answer. let it be


davidg
Good Bye My Friend
Premium,MVM
join:2002-06-15
none
reply to djr777
mount a double pulley directly above the motor, say a 6" and a 1". have the motor belt to the 6" pulley for reduced rotation. then have the 1" pulley drive your tumbler shafts with another belt. no need to change motors.
--
Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine!

bkjohnson
Premium
join:2002-05-22
Birmingham, AL
Reviews:
·Charter

1 recommendation

reply to djr777
I don't know how old your daughter is, or if she will ever show friends her tumbling rig. However, if you use belts and pulleys, be sure you guard them. I still remember pinching my finger badly between the pulley and belt on my Dad's jigsaw. It wasn't even running!


djr777
Premium
join:2005-01-25
Pacific Grove, CA

1 edit
reply to davidg
said by davidg:

mount a double pulley directly above the motor, say a 6" and a 1". have the motor belt to the 6" pulley for reduced rotation. then have the 1" pulley drive your tumbler shafts with another belt. no need to change motors.


thanks,
I like that Idea.

Would I use another roller with a 6" and a 1" or is there another way to go about it?

What do you think that would drop the RPM down too on the tumbler roller?

EDIT: The roller is 1 3/8 x 21 1/2
»www.surpluscenter.com/item.asp?i···electric

--
...there will be an answer. let it be


printscreen

join:2003-11-01
Juana Diaz, PR
reply to djr777
I was about to suggest using a DC gearmotor with a speed controller but Nunya beat me to it. Looks like you are recycling an old motor you have around but it doesn't look like the best choice for the application.


bigfitch
Premium
join:2005-06-01
Aurora, IL

1 recommendation

reply to djr777
I would suggest either finding a set of pulleys that would work would be the easiest.

Small pulley on the motor BIG one on the shaft you are driving.

Another way to go would be look for a motor with a reducer box built onto it
»www.bisongear.com/category.asp_Q_catID_E_2

Very nice company. I have used them in the past. Small motors with slow slow rpms. Think I see 1.5 rpm for the slowest.
They even have mounting bases!!!!!

Hope this helps

Mark

PS when you get this working I would like to see the fruits of your labor maybe a follow up pic
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Proud host of Crunchenstein #4.

--------------------------------


davidg
Good Bye My Friend
Premium,MVM
join:2002-06-15
none
reply to djr777
you could either direct bolt the 2 pulleys together, or put them on a roller shaft. really that would depend on your preference and the pulleys.

just do your math for figuring RPM. if your motor turns 1625RPM on a 1" pulley, that is 5102 inches per minute. a 10" pulley has a circumference of roughly 31.4", so a 1" to 10" would result in roughly 162 RPM on the 10". or for easier reference 10:1 speed reduction, a 12" would be 12:1, etc.... if the 2nd pulley is smaller than the rods you use to tumble, you can get even further speed reduction.

of course, the more pulleys you add, the more belts you need so try to keep it simple!
--
Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine!


djr777
Premium
join:2005-01-25
Pacific Grove, CA
Thanks for everyone's ideas.

Does anyone know where I can get a 8" V pulley with 1 3/8 bore?
....hopefully cheap!

I'm already set up for this roller plus it has a built in grove drive and... the price is right!
»www.surpluscenter.com/item.asp?i···electric

Thanks
--
...there will be an answer. let it be


nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
I thought those were old vacuum beater bars!


djr777
Premium
join:2005-01-25
Pacific Grove, CA
said by nunya:

I thought those were old vacuum beater bars!
They're priced like it!

I found this...but $43.00 + shipping, ouch...I'm looking for 1/2 that!
»www.amazon.com/Browning-Bk80x-Gr···-catcorr
--
...there will be an answer. let it be


Hall
Premium,MVM
join:2000-04-28
Germantown, OH
kudos:2
Do places like Harbor Freight sell replacement pulleys like you have on some air-compressors ?


djr777
Premium
join:2005-01-25
Pacific Grove, CA

1 edit

1 recommendation

Just ordered it!

QTY Stock Status Product Name
1 in stock 7.75 O.D. 1-3/8 BORE 1 GROOVE PULLEY
Item # 1-BK80-I
1 in stock 1-3/8" X 21-1/2" STEEL ROLLER WITH DRIVE GROOVE
Item # 1-2465-A

Pricing
Subtotal: $20.99
Tax: $.00
Shipping: $10.98
Handling: $2.00
Total Cost: $33.97

»www.surpluscenter.com/item.asp?i···electric
»www.surpluscenter.com/item.asp?i···electric

I will let ya know if it works
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...there will be an answer. let it be