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Question
Hi,

I'm hoping you can give me some direction here.

I need a reversible, variable speed motor that will turn a platform about 20" across with an up to 400 lb load on it at about 2-8 RPM.

I have no idea if I'm describing a big or small motor, direct drive, belted, with transmission or what. Would need to plug into a regular 110 outlet.  
  
Much obliged for any suggestions.

Happy New Year,

Mike

Answer
Mike  actually I will be designing and building something very close to that in the near future,    a guy wants a rotating device for his commercial pizza oven,   

I know this much so far,   I will use a variable frequency drive     that also converts single phase power to three phase power,     that way I have motor starting,  reversing, ramping speeds,  46 or more parameters in one box  commercial off the shelf,  

Then I will use a three phase motor,   much cheaper  less expensive and complicated  in some sort of low output rpm gearbox,     then the drive would vary the speed by changing frequency   

That way I can hold torque,     

So I run 110 right off a normal 15 or 20 amp 115 circuit  no big deal,  

The box or VFD is commercially available  it depends on how he or YOU build the table   to determine down or up thrust load,   he is using like two matched thrust bearings but his pizza table is much larger than 20 inches more like 72     

So if he builds the table so there is little added friction to overcome  the smaller the drive the smaller the motor and it would be a gear motor,    right now we are thinking   1/3 hp   because of the centrifugal or flywheel effect  once I get it up and rolling,    

Gear motor to table,    all kinds of options,    regular belts, variable speed sheaves,  plastic belting,   direct drive     gear to gear drive,        he is thinking a pulley on the lower shaft   and mounting the drive to the side,        

The VFD  can be run remotely  or from the keypad,   and it comes in a NEMA one enclosure so it takes care of a lot of parts       motor starter  enclosure,  overloads,.    plus infinite speed and torque control,    

I would suggest you look up VFDS      that change single to three phase,  so much less fussing and if you want variable speed it is absolute,        get away from single phase motors,   

when you get down to 2 RPM  it is more in the gearing or sheaving than the gearbox,   the lower output speed of a gearbox   the more expensive  some are even double planetary and those are big bucks,        

I am looking at a drive that will run around $300  the gearbox  I hope I can find a new used surplus    for less than $500     then some wiring   and sheaves and whartever types of belts   they have so many non rubber belts and sheaves to pick from   you might look at power train options too,      

I like the belted option  simple is better,   even adustable sheaves  to get the final out RPM so slow,         

We run one of our lathes at about 6 or 7  RPM by using a drive just like this and tying into the lathe chuck drive,   then we use the auto feed   attach the welding torch to the carraige  set up the distance   type of wire,   gas    and weld up 9 inch shafts and no one needs to do anything but set it up,     

So I know it works very well,    

In your case you say platform  so I assume it is a horizontal surface,    now with the weight you need a good thrust bearing setup   which any bearing house can give you plenty of brochures and ideas,   but yes   very doable,     

But you are doing the most difficult,   the lower speeds are always difficult  to hold the torque at that low of an rpm,         but still doable,   and fairly cheaply    using new surplus gearboxes is the way to go,      a new drive always        and the drives have everything electrical you need to worry with in one box,  wire in 115  out comes 220 three phase  which is easy to control with frequency        but you want the base speed as low as you can get it,   so if you can find a gearbox with a low low output say   20 RPM  then all the motor has to be reduced by is very little   which helps with cooling and lots of other things,     

my home email is wbwill@sbglobal.net,   write me there and it will be easier than trying to go back and forth through allexperts    nothing against all experts   great great service   but not many are going to be doing this,    so  if you can send me sketchs or whatever  I can feed you ideas     but you need to be worrying with this table, and the 400 down load on whatever bearing setup, first,        and what is the ambient conditions?

The pizza oven I will put the electrical behind a firewall or heat wall so only the belt is driving in the oven,   some sort of steel belting I am guessing at this point,       

let me know some particulars and a drawing,     rough is fine,  

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Will

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Three phase/ AC DC single phase motors, controls, any problems or failures, motor installation, performance issues, connections. All other electric motors/gearboxes/apparatus. Specialty repair concerns, obsolete motors and solutions. Other mechanical or specialty equipment. See my profile under Home/electrical at this site

Experience

30 plus years in the electrical motor and apparatus repair industry. VP level management of repair facilities, current owner of my own specialty repair and consulting firm.

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EASA, IBEW [retired], other specialty organizations, Lubrication, Vibration EDI, Tribo-electric Councils

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Currently fielding concerns at this site under "Home Electrical"

Education/Credentials
4 year technical, College level specific courses, EASA repair courses, vibration analysis electronic and electrical trade school.

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