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speed control on single speed motor

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Forum topic by Jesse posted 01-11-2015 09:26 PM 1156 views 0 times favorited 24 replies Add to Favorites Watch
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Jesse

58 posts in 1091 days


01-11-2015 09:26 PM

I am building a tumbler and I have a 1hp motor. I need to be able to slow it down until I get to 15rpm (so pretty slow). What is the easiest way or best controller to do this? Thanks for the help in advance guys!

Thought I would add this to the original post as well since folks are asking for more info below :)
I have not built this yet, but I plan to build a drum style tumbler that rotates somewhere between 15-25 RPM. I wont know how fast I need it for sure until it is built and I experiment with it. I have a 1hp motor that has a maximum RPM of 1800 RPM. I also have a 1/2hp motor that has the same rated maximum RPM. The barrel will be roughly the size of a 55 gallon drum (not a 55 gallon drum though, it will be a custom built octagon). Think of it rotating like a hog on a spit. I need the room below it so I can open the hatch and release the contents into a tub below the unit. the plan is to have a pulley on a shaft at the motor and also at the drum and I would like the motor hooked up with a dial of some sort so that I may “dial” in the speed as needed.

I am pretty good with wood but no real experience with mechanicals so any advice or help is appreciated.


24 replies so far

View bigblockyeti's profile

bigblockyeti

3668 posts in 1186 days


#1 posted 01-11-2015 09:59 PM

Is the motor and induction motor (like on a furnace blower or a large table saw) or is it a universal motor with brushes (like a router or hand held circular saw)? Determining that would be the first step to establish the best way to achieve what you’re trying to do.

View Nubsnstubs's profile

Nubsnstubs

826 posts in 1195 days


#2 posted 01-11-2015 10:01 PM

Depends on the RPM of the motor. At 1725 rpm, a 1 1/2” motor pulley and a 10-12” pulley attached to a 3/4” drive bar should slow it down enough to get your rpm you’re looking for. ......... Jerry (in Tucson)

-- Jerry (in Tucson)

View crank49's profile

crank49

3981 posts in 2436 days


#3 posted 01-11-2015 10:48 PM

Are you wanting the tumbler to rotate at 15 RPM?
Or, do you already have the tumbler drive designed and need the motor to spin at 15 RPM?

There is a huge difference depending on how the tumbler is driven.

Is this a horizontal drum type tumbler; sitting on two sets of rollers?

Any more info you could share would help.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View Jesse's profile

Jesse

58 posts in 1091 days


#4 posted 01-11-2015 11:55 PM

I have not built this yet, but I plan to build a drum style tumbler that rotates somewhere between 15-25 RPM. I wont know how fast I need it for sure until it is built and I experiment with it. I have a 1hp motor that has a maximum RPM of 1800 RPM. I also have a 1/2hp motor that has the same rated maximum RPM. The barrel will be roughly the size of a 55 gallon drum (not a 55 gallon drum though, it will be a custom built octagon). Think of it rotating like a hog on a spit. I need the room below it so I can open the hatch and release the contents into a tub below the unit. the plan is to have a pulley on a shaft at the motor and also at the drum and I would like the motor hooked up with a dial of some sort so that I may “dial” in the speed as needed.

I am pretty good with wood but no real experience with mechanicals so any advice or help is appreciated.

View Jesse's profile

Jesse

58 posts in 1091 days


#5 posted 01-12-2015 12:03 AM

Any chance it is as simple as using something like this or am I making myself look dumb :)

http://growace.com/speed-bully-motor-speed-controller.html?gclid=CPadvMaTjcMCFQmNaQodVA4AIA

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3141 days


#6 posted 01-12-2015 12:12 AM

Cutting the motor speed electrically will also reduce your horse power. Given the size of the drum you are turning, I would recommend doing the bulk of speed reduction mechanically. You could fine tune it electrically.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View TheFridge's profile

TheFridge

5765 posts in 951 days


#7 posted 01-12-2015 12:20 AM

I’d guess your motor is an induction motor and that speed control is for a universal motor which won’t work. You’d have to get a vfd or gear it down. Not sure how a vfd would affect the torque at Rpms that low.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3141 days


#8 posted 01-12-2015 12:35 AM

With that much speed reduction the only way to maintain torque is to go with a DC motor. They will start and move a load at 1 rpm if you want them too ;-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View gfadvm's profile

gfadvm

14940 posts in 2155 days


#9 posted 01-12-2015 01:14 AM

I have a similar drum tumbler. The drum sits on a pair of rollers and pulley size determines the drum speed. Mine works just like Jerry described above.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View bigblockyeti's profile

bigblockyeti

3668 posts in 1186 days


#10 posted 01-12-2015 03:21 AM

I would recommend performing the reduction mechanically as doing so electrically could prove very expensive very quickly depending on what level of control and torque you are requiring. Will the drum be driven directly or are will it be set on a pair of rollers that will spin in turn rotating the drum at your desired 15rpm? Will you be fine tuning the speed on every batch of whatever you’re making or do you need to dial it in only once to get the performance you need? If you only need to do it once then it would be less expensive to come as close as you can mathematically and adjust the size of the least expensive component, in this case the motor drive pulley.

View Jesse's profile

Jesse

58 posts in 1091 days


#11 posted 01-12-2015 02:47 PM

I believe I will only need to set it once as most of my parts are made from the same woods and roughly the same sizes. I planned on having the drum driven directly, it does not set on a pair of rollers. I attached a picture of what I am thinking in my head. My drum will be made of wood and solid to hold sanding media in but you get the rough idea at least.

I’m afraid I am not nearly knowledgeable enough in this department to do the math to set this up properly managing the speed mechanically. Buying a commercial tumbler the size I need is super expensive, like new car expensive so that is out too.

View Blackbear's profile

Blackbear

137 posts in 1684 days


#12 posted 01-12-2015 02:54 PM

Look up pulse width modulation. If you want to build your own circuit board you could build a controller to do this.

View Jim Finn's profile

Jim Finn

2413 posts in 2387 days


#13 posted 01-12-2015 02:57 PM



I d guess your motor is an induction motor and that speed control is for a universal motor which won t work. You d have to get a vfd or gear it down. Not sure how a vfd would affect the torque at Rpms that low.

- TheFridge


Does your motor have brushes! This is of prime importance! If it does not it is an induction motor. A common speed controller will kill that motor if it worked at all.

-- "You may have your PHD but I have my GED and my DD 214"

View firefighterontheside's profile

firefighterontheside

13489 posts in 1321 days


#14 posted 01-12-2015 03:27 PM

I’m trying to sell my old bandsaw right now that has a 3/4 horse DC motor and a speed controller. It sounds like that is the sort of thing you need. I’m not sure how slow you can make the motor go, but with pulley sizes you could probably get the rest of the way. I bought this saw like this and never used the speed control as I don’t cut metal. I looked at these systems after I bought the saw and they are not cheap. I’m hoping someone comes along and says he wants to pay what I’m asking just so he can have the motor and controller. I don’t think it’s gonna be possible to use two pulleys and go from 1725rpm down to 15.

-- Bill M. "People change, walnut doesn't" by Gene.

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3141 days


#15 posted 01-12-2015 08:19 PM

In the 45 years I was an electrician specializing in motors and controls, I discovered variable speed in AC motors is also variable HP. AC motors at low speed have no torque, that is why DC motors are required for low speed high torque applications. Do not waste your money trying to use variable speed in an AC motor for such a drastic speed reduction.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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