Sciencemadness Discussion Board

ball mill question

Trotsky - 1-6-2013 at 01:01

I recently made myself a pseudo ball mill, consisting of a large pill bottle wrapped in wire, the ends twisted tight around each other, inserted in an electric drill. I control the speed with another bit of wire, one wrap around the trigger and twisted around each other, tighten the twists to speed it up, loosen to show it. Pretty basic and chintzy.

However it works.

1) are lead balls required? I threw in some pennies and socket heads. It seems to be doing the trick. Do they offer any benefit over random hard chunks of metal?

2) how long do you usually mill aluminum for? I intend to use it in a potassium permanganate enhanced ammonal blend for bullet initiation.

3) will it all mill down or do you call time after some point and remove any larger chunks that remain? I have little powder so far but many tiny flakes, very tiny flakes. However there are also some larger pieces that don't seem to be milling down despite 24+ hours. I only have it running at night when I'm home, so I get about 12 hours a day. Four days should be 48 hours, I know, but the wire I used to hold it at first broke off at some unknown point on days two and three.


Ral123 - 1-6-2013 at 01:11

How long will that drill last? Let me give you a hint, it's not made to work for days.
How do you expect to mill aluminium with lead balls?
In what scale do you plan the madness of mixing AN/KMnO4?

Dornier 335A - 1-6-2013 at 06:54

It takes about a week to mill the aluminium. You don't have to remove anything. Here is a good instruction.

Hennig Brand - 2-6-2013 at 08:15

Nice tutorial. Milling time varies though and is dependent on several factors. I have a homemade ball mill that uses a 1/2 hp induction motor and 4" PVC sewer pipe as a drum. It can mill 1/2 pound or so of aluminum sandings down to powder, that works well in small salutes mixed with KClO4 or KClO3, in about 2 days. I put a lot of steel balls in the drum. I used 3/8" steel slingshot ammunition because it was readily available. I think I put about $50 worth in the drum, at 5 dollars per pack of 75 that works out to 750 3/8" steel balls. It would have been nice to have larger media, at least half inch or so in diameter. A larger drum size is also much better for milling aluminum. I have materials for a 6" drum and an 8" drum but just never got around to building them. I found a nice piece of 8" PVC on the side of the road when the city had some streets dug up replacing sewer lines. I found a supplier for end caps, and quickly realized that the price of fittings go up very quickly as the pipe size increases. An end cap for 4" is about $5, for 8" about $20. Anyway, I am sure once I get the right motor and media, etc, I will be able to mill aluminum very quickly with the 8" drum.

Milling time also varies greatly depending on how fine a product you desire. The following was taken from Wikipedia.

Taken from Wikipedia:

"Bond Work Index

In the 1930s through early 1950s, Bond developed a new theory of comminution that introduced an index, called the 'Bond Work Index', which relates power consumption in crushing and grinding to the feed and product size distribution.[1] His theory and index were introduced in a widely cited 1952 journal article.[2] Bond called his theory the "third theory of comminution", counting those of Peter von Rittinger and Friedrich Kick as the first and second. This term and the terminology of "laws of comminution", as in "Rittinger's law", "Kick's law", and "Bond's law", are sometimes used in the field, along with those of subsequent researchers including Walker and Hukki.[3][4][5] Whereas Rittinger's theory held that the work done in breaking rock is proportional to the new surface area produced (that is, inversely proportional to the diameter of the product particles), and Kick's theory held that the work done is directly proportional to the reduction ratio (ratio of feed particle diameter to product particle diameter), Bond's theory held that the work varies inversely as the square root of the product particle diameters. Bond's theory and index brought a greater measure of openness to the calculations for selecting the type, size, and power ratings for ore milling equipment"

Example using Bond's theory:

Work is proportional to 1/ (Product Diameter) ^0.5 - 1/ (Feed Diameter) ^0.5

Going from say 1mm sandings to 100 mesh (149 micron) product gives 50.3
Going from 100 mesh (149 microns) to 625 mesh (20 micron) product gives 141.7

These values are not actual values of work but are only used to make a comparison between the energy required to mill to the 2 different sizes. Efficiencies were assumed to be equal in both cases and the constants were excluded.

Anyway, it takes 141.7/50.3 =~ 2.8 times as much energy to go from 100 mesh to 625 mesh than it does to go from 1mm to 100 mesh.

So as you can see a large amount of work is required to mill material down to a small particle size.

Attachment: Comminution Theory.pdf (967kB)
This file has been downloaded 4702 times

[Edited on 2-6-2013 by Hennig Brand]

Trotsky - 2-6-2013 at 12:26

I dunno how long it'll last, it barely gets warm after 12 hours, brushes will probably wear out quick though, I don't think it's brushless.

Your tubes turn like they're rolling, right? I have mine set up to flip end over end. It, turning real slow. As fast as I can set it so the pieces aren't just stuck to the ends

Trotsky - 2-6-2013 at 12:47

Oh for size of material, I'm planning on filling a pill bottle with the material. I'm not sure offhand how much that'll weigh

Hennig Brand - 2-6-2013 at 13:05

Not exactly sure who is talking to who, but we are all on the same subject so hey.

Yes, the drum rolls on rollers. The electric motor drives one of the rollers via a belt and pulley.
I have 3 strips of the same PVC piping, PVC glued (solvent welded) to the inside of the drum. These lifters greatly increase the tumbling effect of the balls and material to be milled in the drum. I don't remember the exact speed, but I remember looking it up and then changing pulley sizes 2 or 3 times to get the right rotational speed for the size of the drum. Balls should tumble inside the drum, not be glued to the side by excessive centrifugal force from excessive speed. Too little speed is bad also, balls don't climb sides enough and milling/grinding action is slower.

BTW, like the tutorial author I also add some fast burning charcoal (like is used for hot black powder) to the aluminum sandings before milling. I think I was using 5-10% charcoal.

I use a bench top belt sander to sand some aluminum scrap down to sandings.

I haven't made any aluminum powder in a while because I bought a bunch a while back.

[Edited on 2-6-2013 by Hennig Brand]

Ral123 - 2-6-2013 at 16:34

Here's a tutorial for easy to make mill. It will grind quite hard materials with hard ceramic balls.

Trotsky - 5-6-2013 at 10:27

How do you collect the shavings from the sander? Mine just flung them all over the place.

Hennig Brand - 6-6-2013 at 06:30

I set the whole thing in a box with the sander on an incline. Some was lost but most was recovered. If you use too much force it destroys the sanding belts quickly and at the same time results in more contamination of the aluminum sanding with grit from the belt. I was going to set something up that put a constant light pressure on the scrap, as it was fed into the sander, but never got around to it. Some sort of system exploiting gravity or a spring(s) was the idea, which would allow the system to just be monitored instead of applying pressure by hand. I think it took me about 45 fun filled minutes to get a half pound or so of aluminum sandings the last time.

testimento - 11-7-2013 at 22:44

Can one use hardened steel balls(not stainless) for milling aluminium? I plan to use PVC or stainless steel as the mill material, but SS balls are so sick priced in my country that I have to go for normal steel balls or something else. Even gave a thought for small rocks. :D

Metathesis-izer - 14-7-2013 at 04:46

I have seen ball mills for as little as $40 on Craigslist.

In that case it was about 18 inches diameter with 2 drive rollers. I believe it was somebody's ex-rock polisher.

I have also seen other rock polisher - same geometry as ball mills - on Craigslist, but more expensive, e.g. $100.

For grinding media, if you can live with steel, the old type with the ball. Most of them have about a .700 diameter steel ball, coated with rubber.

It may impart some impurities to the media being milled.

On to the ir-relevant section. I know one guy with a larger ball mill. He uses concrete balls to process low-yield gold ore. Processes about 20 tons a day, grinds it from rock to powder. Must be noisier than heck.

The guys at

are also interested in ball mills, they always have some active threads about them. Varying in size from smaller to humongous.

The rock-polisher type are about 10 inches diameter. The gold-mine type are about 4 meters diameter.

testimento - 4-1-2014 at 06:15

Would it make the mill more efficient to make the drum from high strength steel instead of PVC tube? With this, when the balls tumble inside, they will also adhere between the drum and not only with other balls, and afaik this should create additional power.

I'm planning of using 250w motor to drive 160mm drum of steel or PVC at 180-240rpm with 1000pcs of 8mm steel balls and pre-grind the aluminium with blender.

Would it improve the effect to use some form of solvent, like ethanol or oil to adhere the aluminium?

Second, how fine should the powder get? I'd like to procceed all the way down to 1-10mic scale with few days of milling.

Zyklon-A - 4-1-2014 at 07:24

Man where has this thread been, I had a lot of questions 2 months ago when I was building my ball mill, anyway I've answered almost all of them my self now, I still have 1 question, how fast is too fast? I'd be running it, and then it I would come back about 30 mins later, and it would act like a centerfuge, the contents would be on the outside of the container and it would make a lot less noise, (because no grinding was happening). I assume that all grinding affects cease as soon as this happens, the moter is from an electric mixer and there is no way to slow it down. Oh, one more question, would a smaller vessel prevent this action? Thanks.

Dornier 335A - 4-1-2014 at 07:56

180 rpm sounds way too fast. This is what it should look like inside:

[Edited on 4-1-2014 by Dornier 335A]

Zyklon-A - 4-1-2014 at 08:33

I think mine spins faster than 180 rpm, it's about 3 inches in diameter, maybe more?
Is there a formula to calculate how fast it can go based on the diameter of the vessel, and the density/weight of the powder and balls? Maybe some other factors as well, I don't know much about physics

Metacelsus - 4-1-2014 at 14:45

An upper limit on the angular velocity would be given by w=sqrt(g/r), where w is the angular velocity, g is acceleration due to gravity, and r is the radius of the ball mill. At this angular velocity the balls will not fall down at the top of the mill. Thus, for a 5 cm radius ball mill, the maximum angular velocity is about 14 radians per second, or 133 rpm.

confused - 4-1-2014 at 18:55

no first hand experience, but from a web search found that it should be 60%-75% of the mill's critical speed

Nc =76.6(D-0.5)

Nc is the critical speed,in revolutions per minute,
D is the mill effective inside diameter, in feet.

[Edited on 5-1-2014 by confused]

testimento - 4-1-2014 at 23:35

So for 160mm OD 150mm ID mill would ideally work at 110RPM.

But how is the mill drum material? Will harder be better? I can do it from PVC or steel. Or does it matter at all?

confused - 5-1-2014 at 02:07

harder would be better but you might want to avoid any materials that might be spark or might produce alot of static

but people usually use pvc

testimento - 5-1-2014 at 02:35

I dont think the sparking or static would be a problem, since the container will be airtight and aluminium does not react with plain steel - it needs oxidized iron. I have heard that using ceramic or SS media is required, but I see that this is necessary when manufacturing commercial, high grade powders, but for my use, in salutes, I don't wanna pay 5-10 times the cost of SS or special media.

hyfalcon - 5-1-2014 at 03:35

Here's what I use in my mill jars.

dangerous amateur - 5-1-2014 at 04:37

I use the alumina ball too.
20mm is OK for a small rock tumbler (with increased rpm), but not very effecient, for Oxidizers OK.

Ball milling aluminium does not pay off imho. It does not mill very well and takes too long, it's just not worthwhile.

Magnesium or magnalium maybe, if you dare to.

Zyklon-A - 5-1-2014 at 07:01

I use a plactic container,
thanks for your help guys.

testimento - 5-1-2014 at 07:48

Lucky for you Americans to get everything delivered to your door in two days. Try to order something to this forsaken land of mine, and the only quick thing here is the state force. :D That should be a good enough indicator that any aluminium that is finer than 0.1mm at foil form is classified explosive and therefore illegal so milling is only option.

roXefeller - 3-2-2014 at 14:51

I just finished my ball mill today while hanging out with the kids during their snow day. I used the drive from a frozen-bowl ice cream maker. It essentially turns a bowl slowly to push the product against a stationary agitator. It comes with two reductions to slow the motor to reasonable speeds. I tore it apart and mounted the motor/gears parallel to two rolling dowels and connected it with a wide gum band.

Trotsky - 4-2-2014 at 22:59

That's a good idea, but I use my ice cream maker. Home made gelato is wonderful

roXefeller - 5-2-2014 at 04:16

Eh, I can buy ice cream from the local creamery. They won't sell me pyrotechnic compositions though.:D

Refinery - 3-3-2014 at 23:03

I was thinking of making a planetary ball mill.

The idea is to make two different gears rotate around the center to balance out each other between to plates and bring up the rotational speed up to 300RPM.

roXefeller - 4-3-2014 at 16:41

300 seems fast, light it might throw everything to the circumference without tumbling.

hyfalcon - 4-3-2014 at 17:16

I run an 8" ball mill at 50 rpm. You don't want fast, that will glue your media to the sides of the mill jar.

Refinery - 4-3-2014 at 20:24

Please note: planetary mill. There high speeds are must. I have 6" ball mill on me and I run it at about 90RPM. The critical speed is around 120RPM and I can easily hear it when the rumbling sound stops because all media is stuck to the walls because of centrifugal forces.

My idea is to use one inbound gear and align two inner hears with bearings around an axle so when they rotate, they turn counter-clockwise 2-3 times per each revolution. Planetary mill idea is to rotate the media and material by the walls, and when the vessel turns, the media and material is ejected directly on the other wall, creating very high impact energy. Planetary mills are supposed to get 1mm particles below 10um 6-8 times faster than ordinary mills, so one could grind foil aluminium into dark pyro within 24 hours.

If you can get the idea from this picture. The small pots contain the grinded stuff and the whole thing spins around 400RPM. The sub-gear rotation within the pot can reach even as high as 800-1600RPM.

[Edited on 5-3-2014 by Refinery]

Refinery - 5-3-2014 at 16:39

For those who understand more physics, is there any reasonable upper limits for plantary ball mill for critical speeds? For the reference picture I understand that the planetary flasks must be in critical revolution phase in order to work, but would the supporting disk have any upper limit?

planemils.jpg - 76kB

Refinery - 19-3-2014 at 10:51

For you to know, I am currently working on a planetary ball mill project. I have constructed a two-vessel structure with wooden gears and ran it for total of 2 hours now. Because I dont have lathe and other high level metalworking tools, I have hand-made the parts and therefore the tolerances are what they are. I dont have pics on hand because I forgot my camera to my workshop, but will post later. I did a 5-minute test with ballasts(I dont currently have the SS vessels, they are waiting for welding) using two plastic TCCA containers which fit into the rotating basket quite well, and the sheer centrifugal forces grinded the TCCA tablets down to powder during this time. I had to stop it because the containers were able to move few millimeters so that the metallic baskets began to grind through the walls of the baskets and there were a cloud of TCCA in the mill when I opened it. :D

The biggest problem so far is the noise. It's not just like rumbling of an ordinary ball mill, but imagine two 3-kg cylinders fixed at planetary gears to rotate at 900RPM around the planetary axis rotating about 300RPM powered by 1.2kW electric motor. :D The noise is so horrible that even when the mill is empty, I must wear protectors in my workshop. :D So sad my shop is too close to living compartments I could not leave the mill run there, so I must make some special arrangements. Well, I made a wooden coffin and simply buried the mill half-way to the ground and covered it with sandbags and installed some soundproof ventilation shaft and a fan, and now it is all quitet by 10 meters away and close it sounds like large but quiet diesel engine. :D

Waiting for some Al milling tests. Planetary mills should do the job in less than 24 hours what normal mills take weeks to do and they can't even get down to sub-micron level! :P

roXefeller - 20-3-2014 at 02:35

I imagine most of your noise is coming from gear tooth profiles and tolerances. Did you cut straight teeth or helical? Did you say that you powdered tablets in five minutes?

TheAlchemistPirate - 26-3-2014 at 20:35

I found a very reasonably priced professional ball mill at, I would check there.

Amos - 27-3-2014 at 07:04

If you continue having trouble with your ball mill, your grinding media may be lining up in a way that disrupts the grinding process. Upon adding a plastic bar along the inside diameter of my canister; this kept the balls from lining up and greatly sped up the process.

davidmichaud - 18-2-2016 at 16:02

Here is another critical speed calculator for wanna be metallurgists and a ball size calculator and more

JJay - 18-2-2016 at 16:26

Will something like this work as a ball mill if I use alumina balls:

Hennig Brand - 19-2-2016 at 06:06

I had the exact same rock tumbler, when I started milling things, which I got at a yard sale for $3 IIRC. I used it to make 10-15g of flake aluminum powder at a time suitable for flash powder for small firecrackers in 4 days or so from aluminum sandings. Stainless Steel sling shot ammo was used as grinding media. Used to make small batches of black powder with it too. Eventually (after about 10-12 batches) the drive wheel got worn down to the point that it wouldn't drive the drum anymore (I assume all the aluminum dust on the drum and wheel accelerated the wearing). I assume the rubber drive wheel could have been replaced, but it wasn't a great setup anyway. It was too small and the drum couldn't be sealed well at all; there was a big gap where the two pieces of the drum fit together which I sealed with tape as best I could and ran the mill on an incline so the powder was less likely to escape. I built a mill with a PVC drain pipe drum after that which was much better in every way.

NedsHead - 19-2-2016 at 06:15

I would be concerned that alumina may not have the mass to grind much in such a small ball mill, +1 for building your own ball mill to the specifications you need

Bert - 19-2-2016 at 06:50

If you are going to re purpose a rock polisher, larger diameter is always better. 6" ID and up drums will make for much shorter working times when grinding Al powders.

Alumina works, given a large enough Dia. mill jar and larger pieces of media, but heavy media like ball bearings works much faster.

JJay - 20-2-2016 at 01:39

Hmm... looks like I might have to build a ball mill.

I am very curious about United Nuclear's, but every time I check, they are sold out.

ecos - 1-3-2016 at 06:19

I built home made ball mill and I used washing machine motor.
the motor was overheated after few days of running however I used a fan to cool it down.
I think washing machines motors are not suitable to work for continues operation!!
any better suggestions ?

[Edited on 1-3-2016 by ecos]

James Ikanov - 1-3-2016 at 08:14

Perhaps the motor from a dryer?

I might be off, but I would consider the work load more comparable between a ball mill and a dryer than a washing machine and a ball mill.

If nothing else works, then perhaps you could consider putting your motor on a timer, so it has enough time to cool down occasionally? Even one of those "I'm going on vacation but want the lights to flick on/off for a few hours" type deals that plug into the wall could probably be had fairly cheap, if you're using out the wall current.

ecos - 1-3-2016 at 09:54

the washing and dryer motors are "universal motors"

from wiki:


negative aspect is that these motors may only be used where mostly-clean air is present at all times. Due to the dramatically increased risk of overheating, totally-enclosed fan cooled universal motors would be impractical, though some have been made. Such a motor would need a large fan to circulate enough air, decreasing efficiency since the motor must use more energy to cool itself. The impracticality comes from the resulting size, weight, and thermal management issues which open motors have none of.

It is a headache to reduce the speed of the universal motor using pulleys since it has average speed of 10,000 RPM. Mine has 16,000 RPM

I am thinking to use fan motor (induction motor), I am not sure yet if it is the right choice or not !!! :(
at least induction motors has better power efficiency but I am not sure about overheating.

Great - 1-3-2016 at 13:09

Trotsky: If you ever scale your ball mill up, here are some great materials I use that you might like too. The belt would be the rubber inner tube from a child's bicycle, with a diameter of 20 inches. One roller would be a PVC tube coated in this rubber too, and the other would just be inverted wheels from scrapped furniture. (The wheeled type used for patios and workshops)

wg48 - 1-3-2016 at 19:00

Quote: Originally posted by ecos  
the washing and dryer motors are "universal motors"


It is a headache to reduce the speed of the universal motor using pulleys since it has average speed of 10,000 RPM. Mine has 16,000 RPM

I am thinking to use fan motor (induction motor), I am not sure yet if it is the right choice or not !!! :(
at least induction motors has better power efficiency but I am not sure about overheating.

Most dryers have an induction motor. See the one I extracted a few days ago. Unfortunately one of its bearings is worn out. Its a pity as its a nice size (smaller than than many I see) for a mill.

Yes getting the rpm geared down is pain. I prefer a belt reduction system as its more tolerant of build tolerances.

With a universal motor you can probably use a triac phase controller to adjust the rpm or even better an adjustable dc power supply.

WP_20160302_01_29_05_Pro.jpg - 1.3MB

Great - 1-3-2016 at 20:12

I have the weirdest old electric stirrer from the 60s or older, which has a controllable rpm. Pretty big score, also considering how durable and strong the motor is.

ecos - 2-3-2016 at 01:15

I think dryers and washing machines motors are not designed to work for 11 days continuously without stop!

in their work , they run for certain point then stop again and so on, this is not as stressful as running for days without stop.

I am thinking that a fan motor or air pump motor will be the best solution since their normal work is to run for long time !

I am still thinking about better solution !

testimento - 2-3-2016 at 01:38

Could you use electric kitchen stirrer or just about any power kitchenware? Some of them have very low rotation ratios, for ex. I just obtained a stirrer that has 450W motor and five speeds.

A tip too, for those who dont have access to lathe and other tools, find a 3D printing supply and order a bunch of PLA or nylon gears, either common reduction setup or for higher speed motors a worm gear that allows huge reduction ratios, allowing the use of even very small motors, reducing noise and electric cost(as it would matter in non-production use anyways). Worm gears are very good for three-phase motors like those found on most drill presses and these motors are usually designed to be run for thousands of hours under load non-stop. On the other hand, you can also design and order a housing for your gears so you can just bolt em up, connect to the motor and rock'n'roll your balls.

Universal motors are way too fast and noisy for ball mill, even if you were able to reduce the speed with worm gear. It would sound a bit like vacuum. Second to that, as long as your ball mill construction is not rigid enough, it will rattle and chatter the more speed you push to it and the less the parts are perfectly balanced.

Adding a good fan to the motor will increase the lifetime to a huge degree. Small line fans, like 120mm that push something 30-150m3/h of air will keep normal 100-300w drill press motors cool. I use one on my customised X3 milling machine main stepper which gets hot to touch when I drive it on large bits for longer periods of time. I used a 3kW welding transformer that had duty cycle something like 10-20% at full power for days with a line fan I got from my pothead friend that pushed mere 1000m3/h of air - it was enough to keep the tranny cool to touch.

[Edited on 2-3-2016 by testimento]

wg48 - 2-3-2016 at 02:30

Quote: Originally posted by ecos  
I think dryers and washing machines motors are not designed to work for 11 days continuously without stop!

in their work , they run for certain point then stop again and so on, this is not as stressful as running for days without stop.

I am thinking that a fan motor or air pump motor will be the best solution since their normal work is to run for long time !

I am still thinking about better solution !


Yes the poor endurance of modern white goods worries me. Hopefully my dryer motor will not over heat as it should be rated continuously given it probably had up to two hours on the timer and will not be tumbling 10kg of clothes. The lack of stopping and starting in my application my help increase its life

The motor in the pic I posted above did not have sealed bearing. The bearing on the rusty shaft is worn out (noisy and excessive play probably caused the rusting. The cost of replacement sealed bearings may induce me to get an other. motor.

ecos - 2-3-2016 at 03:02

I forgot to mention this about universal motors (washing machines)


A negative aspect is the maintenance and short life problems caused by the commutator, as well as electromagnetic interference (EMI) issues due to any sparking. Because of the relatively high maintenance commutator brushes, universal motors are best-suited for devices such as food mixers and power tools which are used only intermittently, and often have high starting-torque demands.

Thats why universal motors are not suitable for ball mills

I wish I can build professional ball mill like this :

Capture.JPG - 34kB

I think he use 24v or 12v DC motor. I wounder how long can it run !

I am trying to search for DC motors as well since they have strong starting torque and speed can be controlled easily.

@testimento, kitchen stirrer !!
kitchen stirrer maybe be good but I don't know how long they can run :)
I will keep this in mind

[Edited on 2-3-2016 by ecos]

[Edited on 2-3-2016 by ecos]

PHILOU Zrealone - 3-3-2016 at 14:04

Maybe the good old eolian power could be used to provide spinning energy to pulleys activating the ball mill...
--> Wind ball mill
You know like those advertiser pannel (based on S shape from above) along roads that spins on itself no mather where the wind blows from.
So the only thing is to convert vertical axis rotation to a perpendicular horizontal rotation for the ball-mill...

If there is too much wind, there exist dynamic systems that increases inertia of the system and thus reduces the speed...based on the centrifugal force of 2 weights and the attracting force of springs attaching those two opposite weights to the rotating axis...

Hennig Brand - 4-3-2016 at 06:26

Ecos, it is easy enough to get some pillow block bearings. Not sure if these are the best bearings for you, but it gives you an idea anyway.

The frame is fairly simple and could be easily made from some scrap materials even. The motor could be the expensive component, especially if you aren't careful. It is nice that the motor in the YouTube video is so small and fits underneath the drum, but it really doesn't have to and if it wasn't required it would make motor selection much easier probably. Most places I have been, with even fairly modest population size, have motor shops. Often times second hand motors can be found too for good prices, especially at salvage shops (even the ones that don't specialize in motors). All motors eventually wear out, or need to be refurbished, so you have to figure out what is available to you and then what gives you the best value. Maybe you can get motors that only last a few months, or less, but they are really cheap or free. It might make sense to go through several dirt cheap or free motors, if you have a convenient source, rather than spend hundreds of dollars on one top of the line specialty motor. It depends what is important to you.