Box fan RPM

[upnorthwis]

Anyone know what the RPM's are on an El Cheapo 3 speed box fan? Will be making a brass tumbler out of it. Would be nice to know what the input RPM is so I don't have to keep changing pulleys to get my target of 45 RPM.

[Plate plinker]

ummm fast?

[big bore 99]

Not much power at all with those cheap fan motors.

[bangerjim]

As said those fan motors do not have much power. You will want to use a very small, almost shaft size pulley on the motor shaft. And probably at least a 3" pulley on the drum. BIG o-ring works for a belt.

RPM of the motor is unknown because they vary on brand, size, quality.

[upnorthwis]

Thanks for the advice. It might be a good idea for me to abort this project now. I turned the motor on and it seemed to not be running at the usual speed. Rolled my finger on the shaft and then it sped up. It's barely got the power to start itself, much less a bucket full of brass.

[JonB_in_Glencoe]

Old sewing machine motors are handy as heck for several type of projects. Many times those old sewing machines go for little or nothing. If geared down to proper speed, it might have enough power for a brass tumbler ???

[bangerjim]

What you want to look for is a smaller induction motor that does NOT use brushes like a sewing machine or appliance motor. Brush motors "universal" (AC/DC) home appliance motors are designed to run for short periods of time (sewing, blending, vacuuming, blowing, etc) and not for hours at a time like you need with a tumbler.

Brush-type appliance motors generally range from 5-20K RPM. They can be speed controlled with a router speed control box and CERTAIN (very important) kinds of light dimmers.

Try squirting some good 20W oil (not gun oil stuff or 3 in 1) in the bearings of that fan motor....probably dried out from what you said. That is a "shaded pole" motor that does not use brushes, starting contacts, or capacitors to run. Not much power at all. I have several BIG fans I use around the place that have a LOT of power and would work for a long run tumbler. But those fans sell for over a $100! You are better off just buying a tumbler. I use the Harbor Freight 2 drum machine that did not cost much with the 20% coupon.

And you could always use a standard 1/2 or 1/3 HP capacitor start motor found on tons of older shop tools. Standards are 1,725 & 3,600 RPM. Those are internal fan cooled, have excellent starting torque, and lots of run power. Around here in the desert, you can buy a 2 speed 1/2HP 120v evap cooler motor new for $70 or so in any big box store.

banger

[Petrol & Powder]

Simple induction motors, characterized by the lack of brushes, have very little torque. They are simple and inexpensive devices commonly used in low stress applications like box fans. Motors that have brushes (like the old sewing machine motors referenced by Jon B in Glenco) have much higher starting torque despite their small size. If you hang out in stores that sell second hand stuff you can often find good deals on small AC motors.
Bangerjim is also correct, most brush type AC motors are made for short term operation, sewing machines, drills, mixers, etc. There are bigger induction motors that are still self starting that can handle higher torque loads but those motors are a bit harder to find. Squirrel cage motors for air handlers are a good source but they are becoming a bit harder to find.

[Hardcast416taylor]

For many years back when I was both young and broke, I used the rotesserie motor from a grill coupled to a #10 (large) sized can with several metal strips inside to agitate the insides as it turned on the wheels of an old pair of roller skates. I would forget about the fan motor and save yourself wasted time and effort.Robert

[bangerjim]

For many years back when I was both young and broke, I used the rotesserie motor from a grill coupled to a #10 (large) sized can with several metal strips inside to agitate the insides as it turned on the wheels of an old pair of roller skates. I would forget about the fan motor and save yourself wasted time and effort.Robert

Most grill rotisserie motors are either DC battery powered or AC powered "record player" shaded pole motors. They are geared down A LOT and have tons of torque. One of those might be a candidate for your home-brew tumbler. You would need to use a larger pulley on the motor and a smaller one on the tumbler to get speed INCREASE!

But I still say save you time and $$ and just buy a good commercial tumbler. You will not be sorry.

banger

[huntrick64]

Find an old homemade ice cream freezer motor. Plenty of torque and you could the right speed fairly easy.

[upnorthwis]

Next motor I'll try is a meat grinder with a stripped gear that Oster won't sell me a new one. This is a brush type motor but I think for the short duration it will be running, it will be ok. This motor seems to have a very high RPM as the 5/16" motor shaft drives a 3" gear that goes way faster than I can count them. I'll turn down the smaller gear on it to fit a 1-1/2" pulley, then run it on a 10" pulley to see if I can get it slow enough to count RPM. May have to take shoes off.

[bangerjim]

One important piece of info you have left out: SIZE of tumbler drum you are planning on turning.

General rule of thumb: ANY universal (brush-type) motor will run at a minimum of 5K RPM.....all the way up to over 12K for some appliances. I have one that runs at 15K. I generally buy new stand-alone brush-type motors from Grainger when I need one and do not try to scrounge used stuff from old junk appliances. Most of those are generally built into the appliance and can be some what difficult to operate when removed from the device.

Small size, low overall power, and brushes make them perfect for the appliances they are built into. Not so much for other uses. A positive is: they are easy to vary the speed (roughly) on with the correct controller. Some use a HF router speed control box. (load-dependent speed)

Most brass tumblers run for many hours to accomplish what is desired. I run mine for at least 3-4 hours normally. Many run them for much longer! Most appliance universal motors do not have any internal cooling fans on their shafts and can and will get very hot rather rapidly.

Hope your efforts on that meat grinder motor pay off. Your best bet may be a 1/4HP capacitor-start tool or evap cooler motor. Those have excellent torque and most are designed for a 40C rise in temp for long-term operation.....and NO brushes!

bangerjim

[upnorthwis]

The drum was going to be a plastic 5 gallon bucket. I've found another motor to try. Says Washing Machine on it and not much more. Neighbor gave it to me years ago. He had it attached to a winch. Should be plenty of power.

[frkelly74]

I like the rotisserie idea.

[bangerjim]

The drum was going to be a plastic 5 gallon bucket. I've found another motor to try. Says Washing Machine on it and not much more. Neighbor gave it to me years ago. He had it attached to a winch. Should be plenty of power.

If it is an OLD belt drive washing machine, the motor will be a 120v 1/4 or 1/3 or 1/2 HP capacitor start 1,725RPM motor with a 1/2" or so keyed shaft. Perfect for what you are trying to do. I have at least 6 of those in storage! I have gone to either 220 VFD drives or 90VDC variable speed drives on all my tools these days.

banger

[upnorthwis]

Jackpot. Might even be able to use the 9" pulley on the winch.
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[upnorthwis]

And there it is, done. Will try it out in a week or so. Have some ice fishing to do and put miles on my new ATV. Thanks for all the assistance.
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[Walter Laich]

not seeing the motor run or anything I would start out with small batches and work your way up. just saying

[Geezer in NH]

And there it is, done. Will try it out in a week or so. Have some ice fishing to do and put miles on my new ATV. Thanks for all the assistance.
159488
You bought a new atv but cannot buy a 160 buck Frankford rotary tumbler. not judjing just asking.

[upnorthwis]

Sometimes I just like to make things myself. I had the motor and all those parts laying around doing nothing. My logic is that the $160 savings went toward the ATV. I think the $160 part is that front rack. Also, my old Midway catalog #34 only has the RCBS tumbler for $419.99 + shipping.
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