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Electric Motors/Motor for custom ceiling fan


Hi. I need a motor for a custom ceiling fan I'm building. The fans will be 2 70" airplane props weighing 20ish pounds apiece and driven by leather drive belts. There is very little information out there but I think I want about a 1/2 hp 110 VAC motor capable of no more than 400 rpm, preferably with variable speed. It also needs to be very quiet and capable of running continuously. Any advice?
Thanks, John

Now that is a ceiling fan!   AIRCRAFT PROPS        how much area or is this for the uniqueness of the build?

Your biggest problem is finding the 400 base speed,    in a single phase motor,

This is how I would go about it.  1/2 HP should spin 40 lbs,  the amount of load from the shape of the props, cutting the air,  at a given RPM  is going to the be the REAL Load, which is how you should size the motor,     any way to get that data from 70 inch props turning at 400 RPM?  

The above link might help you calculate the HP and torque needed,   I have no way to gauge the amount of load,   it will depend on the actual weight and the type of props  plus the design and load created   

props are different than normal fan blades,   but if this is going in a typical residence,  you will probably be OK on a typical circuit,  1/2 HP if it is enough,  will run at around 10 amps plus you need a bit more for the inductive load on startup,  I would run a dedicated circuit,    

Now how to get down to 400 RPM is the big problem   you will have a hard time finding a 900 rpm motor single phase let alone anything slower,   plus the lower in RPM the larger the FRAME due to the number of poles,   

So do some figuring on your pulley ratios and give yourself all the rpm on the driver you can,   and move the larger pulley to the load,

Because you think you will need 400 rpm at the motor shaft,  I would use three phase.

I would get a three phase 220 volt motor,   and a 115 single phase to 220 volt three phase frequency drive which would give you variable speed,   and find the lowest rpm three phase motor you can in three phase, which still wont be easy but a hell of a lot easier than a single phase way down there.

The drive need not be mounted on the fan itself,   you can get these drives in a NEMA enclosure,  use the keypad for control  or a remote,  wired or wireless, keypad,  

The drive  will convert your single into three phase,  raise the voltage to 220, and supply infinite control of frequency which in turn will control speed, from 0 to above the motor's base speed, but only go above if absolutely necessary, and then not much maybe 20%   

If you could ratio the pulleys from an 1800 rpm motor that is going to be your cheapest option,   plus if possible it should give you more torque,   

This drive  [I have installed literally thousands of these drives, to convert single to three phase for speed control,  plus it should drive the motor without a lot of HUM   

Also most of these drives  like a VTECH or MARATHON   will have around 46 programmable parameters, from start up slope,  torque settings,  hertz settings,   ramp up, ramp down, noise reduction parameters,  braking,  overload protection, motor starter, all in one box,   

Trying to speed control a single phase motor at 1/2 HP is going to be real tough and without a drive the torque is nailed to the RPM and you will lose torque fast as you lower RPM.

But using a more solid, three phase motor,  now you have room for control of torque,   and you will have a hard time finding a 400 RPM three phase motor as well,   not as bad as a single phase,  but a shot,   it is going to be a big motor no matter what     @400 RPM, 1/2 HP  

900 is somewhat more likely to find,   are you mounting the motor shaft up?

I would try to go that way, if possible.

above single phase 50 hertz  [50 versus 60 rated at 1500 RPM]


You can check ebay there seems to be a ton of motors on there,   I would be very careful about what I bought because normally the seller knows less about motors than the buyer,   

You can try   or I can,   but a 400 RPM motor [base speed] is going to be hard to find,     and size is going to be an issue,     1/2 HP  in AC is about a 56 frame,  that is why I put the first link on here,  you can at least see the size of a 56 frame motor,  not much in a smaller frame,   up to 1/2 HP,       

You could think about DC  not a big problem to get a cube rectifier,  up to 30 or 40 amps but then you have the same problem of base speed,   DC is used for keeping the torque curve much much tighter at lower RPM,    but the expense is going to go up

You might look into some sort of servo motor,   but then the controller is going to be twice to 10 times of a single to three phase frequency drive,  upping the voltage in the drive, so we keep the motor voltage higher  [and the current down]

So you can use a typical 115 house circuit,  the drive allows for the transformer,  all in one, or you can run a 220 circuit and do the same thing,     but your preference was 115 so I went there first,    

Belted helps, but again think about the motor RPM<  and your pulleys,  the higher the motor speed the better,   1200 is fairly common,    

I don't know what your budget is,  but with two props and leather belts,  pretty fancy,  and for the most economical method is going to be an AC DRIVE,  WITH A HIGHER RPM MOTOR, USING SHEAVE RATIOS FOR TORQUE,  and of course fan speed,    

A drive that includes all the above  46 parameters,  at 1/2 hp  somewhere around $250 up,   not horrible for everything from motor starter to overload,   all in one, so you don't need more components to fuss with,    

If your budget is not a huge concern,  probably some sort of servo drive will five you torque, lower base speed, and speed control,  you can use 115 volt AC for supply,  but that type of setup is going to be pricey,   

The reason ceiling fans have large round motors is they are individual poles  that keeps the base speed to much lower but the diameter is large,    

I hand wound a solid brass ceiling fan antique for the Nelson Art Gallery here in Kansas City, it was probably around 1 HP,  the blades,  8 if I remember correctly, about 4 foot each,  the body of the motor three feet across,  with 30 or so poles around the parameter.

this youtube video will help you get an idea  of a ceiling fan motor,

What you might think about is some sort of existing ceiling fan,  industrial size or pro size,  and robbing the motor AND CONTROLS from it,    

A normal ceiling fan is not variable but multi fixed speeds,   this is done with changing the pole configurations by changing the external connections,  making some poles side by side the same, from alternate poles,  using some of the poles.   so on,  so the controller must match the specific motor,    

I am not sure where to send you to look for a motor only,  but if you found a deal on a complete fan,  you could trash the blades and use some sort of shaft connection to the hubs of your props,   maybe a hollow shaft extension,   you would have to cut one from raw material,  or have a machine shop do it, or we could do it,      

But to variable  I am taking it you want complete control not 2 or 3 speeds,     and the only way to do that is vary the motor,  but a single phase motor with a capacitor start,  is not going to be capable,  maybe a PSC   permanent split capacitor     motor you can vary the speed,but you lose torque when dropping the speed and voltage,       not a good choice depending how far you need to drop from base,

Above I picked out a condenser fan motor,  it will be two or three speeds,  not sure if you can get to 1/2 HP  but a place to start looking,

now maybe someone like Dan's would sell you a motor and controller,   generic motors in one single motor is going to be a special build    so you would have to live with whatever they have,  but they do carry some huge fans,   pretty sure 430 lbs of blades is going to be an issue, with a standard ceiling fan motor  available retail,       

maybe antique ceiling fan with a scrapped out or burnt out motor,  those could be rewound,  if the controls are with it,    you can build controls for three speeds,  a bit of engineering,  but it can be done,    

So that is why I still think your best shot would be a three phase motor with a freq drive,  

At this point we are guessing at the HP and torque,  no way to know,  unless you do a mock up of the blades on a hub    belt it to a generic motor and measure the current,    that would be one way to get in the ballpark,        

Quite a project,  it will be a great fan when done, it depends on budget,  anything can be done, reverse engineered, rewound,  whatever,    

If you want I can search for a motor and drive,   probably be some kind of new surplus or used, but we can search nation or even world wide,   

And if you come up with someway to mount the motor,  using say a 56 frame foot print, we can supply a drive and motor,  but most likely the lowest speed stock retail is going to be 1200 base,  maybe get lucky and find 900 but 400 base speed,    going to be tough    doable but tough       

once you look all this over,  get back to me    MEAR Services Inc in Kansas City,    816-650-4030  phone,     or my personal email,  

let me know what you think from this info,   and I can refine further,   

Will Babbitt

Electric Motors

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