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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Slowing down motor
I have a 1.5 hp motor that I have running on a vee belt pulley, turning
a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. |
#2
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Slowing down motor
On 12/24/2013 8:32 PM, Steve Bulicz wrote:
I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. Your motor is designed to work at only one (synchronous) speed determined by line frequency. A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Good luck! Carla Interestingly, the two states which require no license to carry (firearms), Vermont and Alaska, have not had any problems due to this liberal approach. Equally curious is that Washington, D.C., where not only concealed carry but any firearms ownership is illegal, has one of the highest rates of violent crime. |
#3
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Slowing down motor
On 12/24/2013 9:52 PM, Carla Fong wrote:
Your motor is designed to work at only one (synchronous) speed determined by line frequency. A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Good luck! Carla I can see that I am probably going to have to run the motor straight into the gear reducer, and see how that rpm does. If it is unacceptable, then I will have to determine the acceptable rpm, and put an intermittent pulley assembly to drop the rpm down to a usable rpm. Which is what I was trying to avoid. Steve |
#4
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Slowing down motor
On 12/24/13, 8:52 PM, Carla Fong wrote:
On 12/24/2013 8:32 PM, Steve Bulicz wrote: I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. Your motor is designed to work at only one (synchronous) speed determined by line frequency. A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Good luck! Carla Some years back my sister tossed out an old exercise treadmill... I snapped it up for whatever hardware I could recover before re-scrapping. It's speed control was accomplished by such a variable diameter pulley. If your not in a hurry, keep your eye out for one... in my 'hood' you see them out for collection several times a year. As always, YMMV. Or... maybe you could cobble up some sort of step pulley arrangement as used by many drill presses and similar machinery. Good luck! Erik |
#5
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Slowing down motor
On Tue, 24 Dec 2013 21:32:13 -0700, Steve Bulicz
wrote: I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. You need to vary the frequency to change the speed of an AC induction motor - which requires a rather expensive variable frquency drive (VFD) - and generally speaking a 3 phase motor starts much better on a VFD than a single phase and produces better torque across the speed range. |
#6
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Slowing down motor
On Tue, 24 Dec 2013 20:52:56 -0800, Carla Fong
wrote: On 12/24/2013 8:32 PM, Steve Bulicz wrote: I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. Your motor is designed to work at only one (synchronous) speed determined by line frequency. A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Good luck! Carla Interestingly, the two states which require no license to carry (firearms), Vermont and Alaska, have not had any problems due to this liberal approach. Equally curious is that Washington, D.C., where not only concealed carry but any firearms ownership is illegal, has one of the highest rates of violent crime. Or get a DC motor and you can vary the speed by changing the voltage to the feild if it is shunt wound, or to the armature if it is PM. 1.5HP is right in the treadmill motor size range so they are quite readily available surplus - with PWM controllers. |
#7
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Slowing down motor
On Tue, 24 Dec 2013 21:18:30 -0800, Erik
wrote: Or... maybe you could cobble up some sort of step pulley arrangement as used by many drill presses and similar machinery. ============ see http://www.wttool.com/index/page/cat...gory_id/15990/ http://www.wttool.com/index/page/cat...gory_id/21687/ -- Unka' George "Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants, but debt is the money of slaves" -Norm Franz, "Money and Wealth in the New Millenium" |
#8
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Slowing down motor
On Tue, 24 Dec 2013 20:52:56 -0800, Carla Fong
wrote: On 12/24/2013 8:32 PM, Steve Bulicz wrote: I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. Your motor is designed to work at only one (synchronous) speed determined by line frequency. A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Good luck! Carla Only 3ph motors work on a VFD. That being said...3ph motors are dirt cheap, particularly in the 1.5-3hp range. There are a number of VFDs out there that are designed to input SINGLE PHASE and output 3ph..so not having 3ph is not an issue. Id strongly suggest going up a full hp or more when using a vfd and running at slow rpms. Example...if your motor is 1.5 hp..install a 3hp VFD at minimum, so your motor doesnt bog down the VFD. A 3h p VFD can be had on Ebay for less than $100 and new ones are about $200-225 from DrivesDirect etc etc One can pick up a 3ph 3hp motor for $25-50 easily enough. Gunner Interestingly, the two states which require no license to carry (firearms), Vermont and Alaska, have not had any problems due to this liberal approach. Equally curious is that Washington, D.C., where not only concealed carry but any firearms ownership is illegal, has one of the highest rates of violent crime. -- "Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that but it is great if your best friend does. That way you get all the benefits without any of the upkeep" --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com |
#9
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Slowing down motor
On Tue, 24 Dec 2013 21:58:04 -0700, Steve Bulicz
wrote: On 12/24/2013 9:52 PM, Carla Fong wrote: Your motor is designed to work at only one (synchronous) speed determined by line frequency. A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Good luck! Carla I can see that I am probably going to have to run the motor straight into the gear reducer, and see how that rpm does. If it is unacceptable, then I will have to determine the acceptable rpm, and put an intermittent pulley assembly to drop the rpm down to a usable rpm. Which is what I was trying to avoid. Steve I do..do have a variable speed drive in a can..NOS..Ill have to see if I can find it and see what the ratios are. I figure its worth $300 plus shipping if you want a mechanical method. They sell on Ebay for over a grand. As I stated earlier...do a search on Ebay for "3hp vfd" and they are showing up as new..for $149 and used ones are less..but they are not mechanical. Gunner -- "Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that but it is great if your best friend does. That way you get all the benefits without any of the upkeep" --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com |
#10
Posted to rec.crafts.metalworking
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Slowing down motor
On 12/24/2013 10:32 PM, Steve Bulicz wrote:
I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. $25 But it WILL work. Something like this: http://www.ebay.com/bhp/variable-speed-motor-controller http://www.turbineproducts.com/servlet/Detail?no=30 Will work with any universal AC motor. On/Off/variable rocker switch, dial speed adjustment. Allows you to vary the speed of tools, or any brush type universal motor. Will not work on induction, shaded pole, soft/slow start, or brushless type motors. |
#11
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Slowing down motor
On Tue, 24 Dec 2013 21:32:13 -0700, Steve Bulicz
wrote: I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. Why not use a jack shaft and use up a second set of pulleys to get the speed that you want? -- Cheers, John B. |
#12
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Slowing down motor
On Wednesday, December 25, 2013 12:18:30 AM UTC-5, Erik wrote:
A VFD might work with a single phase motor (I've never tried it) Do not bother to try a VFD on a single phase motor. It will not work very well. Looking for a treadmill is a good idea. Some of them use DC motors to control the speed and some use variable speed pulleys. Either would work. If you end up having to add a jack shaft , check laundry dryers. They usually use a jackshaft to slow the speed down. You did not state the speed of the motor that you have. If it is a 3450 rpm motor, switching to a 1750 rpm motor would help. Another idea is to check your lawn mower shop in your area. The axle of the rear end has about a 6 : 1 reduction and they are good for about the horse power you are using. You might say where you are. Maybe someone here has a solution that would not involve expensive shipping. Dan |
#13
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Slowing down motor
"Steve Bulicz" wrote in message
... ... Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. You aren't the first person to want a variable speed AC motor. Look at the design of price-sensitive power tools, they have either a constant-speed AC motor and pulleys or a DC (sparks) motor with a variable voltage speed control. If there was a good way to slow down small single-phase AC motors you would see it everywhere. You could buy a cheap used variable-speed drill with a bad cord or chuck to experiment with, to find the best speed range for a pulley speed reducer for your AC motor. jsw |
#14
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Slowing down motor
The cheapest option is to replace the single phase motor with a 3
phase 1 HP motor and 115v variable frequency drive. This will cost you roughly $200-250. You can sell your 1.5hp single phase to recoup some of the cost. You can also make additional mechanical reduction, but this is more painful and cumbersome. Of course, if you had access to a lot of motors and reducers, like if you were a scrapper, it would be a different story. But since you do not have such access, the above is my advice. i On 2013-12-25, Steve Bulicz wrote: I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. |
#15
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Slowing down motor
On 2013-12-25, Carla Fong wrote:
A VFD might work with a single phase motor (I've never tried it) but the It will not work due to centrifugal capacitor switch. easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Good luck! Carla Interestingly, the two states which require no license to carry (firearms), Vermont and Alaska, have not had any problems due to this liberal approach. Equally curious is that Washington, D.C., where not only concealed carry but any firearms ownership is illegal, has one of the highest rates of violent crime. |
#16
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Slowing down motor
A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Problem is safety. I want a direct drive into the main trommel shaft, or maybe one secondary shaft, so that it doesn't get all complicated with multiple spinning pulleys. This is going to be somewhat dangerous, and I want to keep it simple, and would rather have a spin dial to control rpm than have to change pulleys. Another thing, the operating speed of the motor is 1725 rpm, and I have to drop the trommel speed down to around 50 rpm. So I would have to have a HUGE pulley in a two pulley arrangement to come down to 50 rpm, or I would have to add an intermediary to reduce it down. Think I will go from motor to gear reduction, which will spin at about 72 rpm on output, then do another set of different sized pulleys to step that down a little, and call that good. Steve |
#17
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Slowing down motor
Steve Bulicz wrote:
I have a 1.5 hp motor that I have running on a vee belt pulley, turning a 16" dia. x 3' long trommel of sorts to dehull pecans. I have a gear reduction motor, with a reduction of 24:1. Right now, I have the trommel hooked up to a 1725 rpm motor with a 1.5" dia pulley, then a 14" pulley. I hooked it up today, and it nearly took off across the shop. I don't want to really want to use the gear reduction drive, as I compute that if I hook it up straight through, I will end up at about 71 rpm on the trommel, kinda fast sounding, but wouldn't know unless I hook it up and run it. It needs to spin just fast enough so that all the nuts keep tumbling, and not go to one side of the cage like a blanket in a washing machine spin cycle. So, I wanted to hook up a rheostat. Tried a dimmer, forget that. Looked at variable voltage controls, and they are from $20 to $2,000. What do I need to put in line on this motor to be able to regulate its speed? It is a big heavy motor, and it has two covers on top, I think cap starts. Look like the old bulbous things on a 55 Chevy starter, but two of them. Want to keep it simple. I could get another gear reduction, but that would have to be a miracle, as I won't pay retail. Don't want a series of pullies, would rather have electrical controller. I need some control, as the hopper will be loaded with different poundages of nuts, and different shapes which will change tumbling characteristics. Help appreciated. How about friction drive? Use the current motor & pulley to drive a powered bed. 4 pillow blocks, some 3/4" shaft and some 3/4" heater hose glued to the shaft. Couple the shafts with a pair of pulleys or sprockets and chain. Drive one shaft with your current motor. Would give you about a 13 rpm rotation speed of the drum with the current motor and pulleys. Could easily be sped up by dropping the 14" pulley size. If you tossed a step pulley on the motor you would have a lot of adjustment. -- Steve W. |
#18
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Slowing down motor
On Wed, 25 Dec 2013 19:53:39 -0700, Steve Bulicz
wrote: A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Problem is safety. I want a direct drive into the main trommel shaft, or maybe one secondary shaft, so that it doesn't get all complicated with multiple spinning pulleys. This is going to be somewhat dangerous, and I want to keep it simple, and would rather have a spin dial to control rpm than have to change pulleys. Another thing, the operating speed of the motor is 1725 rpm, and I have to drop the trommel speed down to around 50 rpm. So I would have to have a HUGE pulley in a two pulley arrangement to come down to 50 rpm, or I would have to add an intermediary to reduce it down. Think I will go from motor to gear reduction, which will spin at about 72 rpm on output, then do another set of different sized pulleys to step that down a little, and call that good. Steve So you want a VFD . Quick, simple and easy. Gunner -- "Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that but it is great if your best friend does. That way you get all the benefits without any of the upkeep" --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com |
#19
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Slowing down motor
On 12/25/2013 9:53 PM, Steve Bulicz wrote: ... the operating
speed of the motor is 1725 rpm, and I have to drop the trommel speed down to around 50 rpm. ... Other suggestions about slowing down the motor (e.g., 3 phase & VFD) have this complication: you lose horsepower proportional to the speed drop. So a 1725 rpm 3 hp motor running at 50 rpm will only produce 1/12 hp! This is a matter of physics, not a technicality. I.e, unavoidable. Mechanical slowings down (pulleys, gears) do not suffer this effect. They lose some hp, but not in a big way. Bob |
#20
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Slowing down motor
On Thu, 26 Dec 2013 18:28:15 -0500, Bob Engelhardt
wrote: On 12/25/2013 9:53 PM, Steve Bulicz wrote: ... the operating speed of the motor is 1725 rpm, and I have to drop the trommel speed down to around 50 rpm. ... Other suggestions about slowing down the motor (e.g., 3 phase & VFD) have this complication: you lose horsepower proportional to the speed drop. So a 1725 rpm 3 hp motor running at 50 rpm will only produce 1/12 hp! This is a matter of physics, not a technicality. I.e, unavoidable. Mechanical slowings down (pulleys, gears) do not suffer this effect. They lose some hp, but not in a big way. Bob You lose the horsepower if you match the VFD to the motor. If you DOUBLE the size of the VFD..you loose very little if any power. Gunner -- "Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that but it is great if your best friend does. That way you get all the benefits without any of the upkeep" --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com |
#21
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Slowing down motor
On 12/26/2013 9:43 PM, Gunner Asch wrote:
You lose the horsepower if you match the VFD to the motor. If you DOUBLE the size of the VFD..you loose very little if any power. I don't think so ... horsepower is torque x rpm; torque is proportional to current; current is limited by motor windings. Bob |
#22
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Slowing down motor
On Fri, 27 Dec 2013 09:23:30 -0500, Bob Engelhardt
wrote: On 12/26/2013 9:43 PM, Gunner Asch wrote: You lose the horsepower if you match the VFD to the motor. If you DOUBLE the size of the VFD..you loose very little if any power. I don't think so ... horsepower is torque x rpm; torque is proportional to current; current is limited by motor windings. Bob What Bob says is true. Induction motors are designed to work at a certain frequency and voltage. If the frequency is increased then the voltage should be increased too in order for the motor to have the same torque. This results in the motor developing more horsepower as the speed increases. However, most VFDs will not increase the voltage along with the frequency. This means that when the motor is running faster it will have less torque and instead will have a constant power output. The VFD will also not reduce the voltage when it lowers the frequency because this would result in a loss of torque. So as the frequency drops the voltage still stays the same. This results in motors operating slower than the nameplate rating becoming constant torque machines and motors operating above the nameplate rating becoming constant HP machines. Eric --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com |
#23
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Slowing down motor
On 12/27/2013 8:23 AM, Bob Engelhardt wrote:
On 12/26/2013 9:43 PM, Gunner Asch wrote: You lose the horsepower if you match the VFD to the motor. If you DOUBLE the size of the VFD..you loose very little if any power. I don't think so ... horsepower is torque x rpm; torque is proportional to current; current is limited by motor windings. Bob Slowing down? wouldn't that be a lower RPM? |
#24
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Slowing down motor
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#25
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Slowing down motor
On Fri, 27 Dec 2013 09:23:30 -0500, Bob Engelhardt
wrote: On 12/26/2013 9:43 PM, Gunner Asch wrote: You lose the horsepower if you match the VFD to the motor. If you DOUBLE the size of the VFD..you loose very little if any power. I don't think so ... horsepower is torque x rpm; torque is proportional to current; current is limited by motor windings. Bob True indeed. That being said...I make my money fixing VFD run machine tools and most have zero gearing with a VFD doing the hard work. So perhaps in calcs it may not work..in the real world..it most certainly does. One could simply make one pulley larger than the other so the works are turning at 75 rmp..but the motor is turning 150-300-600-1200 rpm What ever you are happy with. Gunner -- "Owning a sailboat is like marrying a nymphomaniac. You don’t want to do that but it is great if your best friend does. That way you get all the benefits without any of the upkeep" --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com |
#27
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Slowing down motor
On Wed, 25 Dec 2013 19:53:39 -0700, Steve Bulicz
wrote: A VFD might work with a single phase motor (I've never tried it) but the easier solution is a Variable Speed Belt Drive. You shift the motor back and forth and the spring-loaded pulley in essence changes diameter to give variable speed operation. One source among many: http://www.lovejoy-inc.com/products/variable-speed-drives.aspx Problem is safety. I want a direct drive into the main trommel shaft, or maybe one secondary shaft, so that it doesn't get all complicated with multiple spinning pulleys. This is going to be somewhat dangerous, and I want to keep it simple, and would rather have a spin dial to control rpm than have to change pulleys. Another thing, the operating speed of the motor is 1725 rpm, and I have to drop the trommel speed down to around 50 rpm. So I would have to have a HUGE pulley in a two pulley arrangement to come down to 50 rpm, or I would have to add an intermediary to reduce it down. Think I will go from motor to gear reduction, which will spin at about 72 rpm on output, then do another set of different sized pulleys to step that down a little, and call that good. Steve Let that gearbox and single pulley step-down get you into the neighborhood - If you can find an old Universal brush type motor (look for the nameplate specifying 120 Volts AC /or/ DC, then you can get a simple reactor motor speed control (think Sewing Machine, but heavier) and vary the motor speed down some. But Not Up, you'd need a stepped pulley or such to do that. If that works and you plan to build this semi-permanently, go get a matching HP 1725-RPM 3-Phase Inverter Duty motor to run the drum drive, and a small Variable Frequency Drive to power it - if you don't have 3-phase power available make sure you get one that is rated to run on 120/240V single-phase input. Then you can vary it down and up maybe 30% each way before you start getting in trouble. Major speed deviations may require a separate exterior cooling fan on the motor to make sure it doesn't cook itself - the motor's own fan isn't turning fast enough. Sometimes with a tumbling or polishing action you need to vary speed slightly to find the sweet spot where the abrasive is flowing and not fighting. |
#28
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Slowing down motor
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#29
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Slowing down motor
I don't think the pecans will all stick to the side of the drum at 71 rpm. If your bearing supports are stiff enough, you can likely run at this speed.
If you need a soft start and you're more of a mechanical guy, you could build in a centrifugal clutch. Chris |
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