Home-made electrical motor not running

[S_Noakes]

TL;DR Summary

For school, I am trying to make an electric motor. When I try to apply power across the commutator however, it will either twitch a little bit or do nothing at all.

Here are the details. I started with a nut and bolt, and drilled a hole down the center of it. I inverted and glued into place a carbon fiber rod in the hole. I glued a bit on the end of the bolt. I wrapped magnet wire around the bolt on each side of the rod 400 times. I made a commutator using brass, and soldered one end of the wire to each side. The separation in the commutator is lined up the the bolt head and nut.

For magnets, I am using two small (but strong) magnets per side.

For power, I am using a 9-volt battery with copper wires connected to it. I’m touching the copper wires against the commutator 180 degrees apart.

The structure is made out of aluminum, if that matters.

What am I doing wrong? Am I missing anything obvious?

let me know if you want more info or pictures.

 

[S_Noakes]

Summary:: For school, I am trying to make an electric motor. When I try to apply power across the commutator however, it will either twitch a little bit or do nothing at all.

Here are the details. I started with a nut and bolt, and drilled a hole down the center of it. I inverted and glued into place a carbon fiber rod in the hole. I glued a bit on the end of the bolt. I wrapped magnet wire around the bolt on each side of the rod 400 times. I made a commutator using brass, and soldered one end of the wire to each side. The separation in the commutator is lined up the the bolt head and nut.

For magnets, I am using two small (but strong) magnets per side.

For power, I am using a 9-volt battery with copper wires connected to it. I’m touching the copper wires against the commutator 180 degrees apart.

The structure is made out of aluminum, if that matters.

What am I doing wrong? Am I missing anything obvious?

let me know if you want more info or pictures.

View attachment 291165
View attachment 291166View attachment 291167

Let me also add that I checked the copper wire and brass commutator with a multimeter, and had a little less than 20 ohms of resistance across the system.

 

[Drakkith]

Does your wire have an insulating coating on it? If not, you're just shorting the whole thing out.

 

[S_Noakes]

I’m Does your wire have an insulating coating on it? If not, you're just shorting the whole thing out.

I think so. It was advertised as having a coating.

 

[marcusl]

Is your coil wound continuously from one end to the other? What are the nut and bolt made of? (They should be plain steel, not stainless.) You don’t show the orientation of your brushes (contacts)—they should contact side to side, not top to bottom, because the coil (armature) wants to change electrical polarity just at the point you are showing. Finally, you could give it a spin with your finger after connecting the brushes to start it moving. Make sure your battery is fresh, too.

 

[Rive]

You grabbed the strongest magnet at hand, I guess?

In this setup the magnets are trying to hog the iron and you would need current through the coil strong enough to rival that force.

I would try reduce the amount of magnets and extend the magnetic field (and make it more homogenous), maybe by some iron plates.
Also, how is the polarity of the magnets?

 

[tech99]

Check that the magnets are attracting each other, in other words, N at one end of the bolt and S at the other.
Commutator must be altered as mentioned.
You need to give the motor a good spin top start it because the magnets attract the bolt even with no current.
A 9V battery might not give enough current due to its internal resistance. Maybe use 4 x AA batteries in series giving about 6 volts. I usually use an air coil for the armature.

 

[Baluncore]

@S_Noakes
Is there a web link to the instructions you were given?

 

[tech99]

Check that the magnets are attracting each other, in other words, N at one end of the bolt and S at the other.
Commutator must be altered as mentioned.
You need to give the motor a good spin top start it because the magnets attract the bolt even with no current.
A 9V battery might not give enough current due to its internal resistance. Maybe use 4 x AA batteries in series giving about 6 volts. I usually use an air coil for the armature.

It is also possible that the shaft is too thick, which increases friction. Best to use a small diameter shaft.

 

[S_Noakes]

Is your coil wound continuously from one end to the other? What are the nut and bolt made of? (They should be plain steel, not stainless.) You don’t show the orientation of your brushes (contacts)—they should contact side to side, not top to bottom, because the coil (armature) wants to change electrical polarity just at the point you are showing. Finally, you could give it a spin with your finger after connecting the brushes to start it moving. Make sure your battery is fresh, too.

1) yes, the coil is wound continuously from one side to the other

2) the nut and bolt ARE stainless. How would this affect things?

3) picture included below. Mine is the same way. The “cuts” in the brushes face the nut and the head of the bolt

4) I have tried giving it a boost with my finger. No luck.

 

[S_Noakes]

You grabbed the strongest magnet at hand, I guess?

In this setup the magnets are trying to hog the iron and you would need current through the coil strong enough to rival that force.

I would try reduce the amount of magnets and extend the magnetic field (and make it more homogenous), maybe by some iron plates.
Also, how is the polarity of the magnets?

1) they were the strongest magnets I could find.

2) where would I add the iron plates? Horizontal to the base of the motor, at the same height the magnets are currently?

3) the polarity of the magnets is north on one side and south on the other

 

[S_Noakes]

@S_Noakes
Is there a web link to the instructions you were given?

This is what I was basing my design off of.

 

[Rive]

2) where would I add the iron plates?

The original context of that coil you brought up as template is something like this:

With this setup the magnets cannot 'hog' the screw, since the magnetic circuit is always closed, without singular positions.
Try to reproduce this as much as you can.

Or, you can drop the screw and use a wooden stick instead. That will work too.

 

[S_Noakes]

The original context of that coil you brought up as template is something like this:
View attachment 291191
With this setup the magnets cannot 'hog' the screw, since the magnetic circuit is always closed, without singular positions.
Try to reproduce this as much as you can.

Or, you can drop the screw and use a wooden stick instead. That will work too.

I’ll give that a shot after I get back from school. Thanks!

 

[Baluncore]

2) the nut and bolt ARE stainless. How would this affect things?

Stainless steel is not usually magnetic. Test it with a magnet and compare it to a cheap bolt.
I expect the cheapest soft iron bolt would perform much better than any more expensive bolt.

 

[S_Noakes]

Stainless steel is not usually magnetic. Test it with a magnet and compare it to a cheap bolt.
I expect the cheapest soft iron bolt would perform much better than any more expensive bolt.

Didn’t know that stainless was less magnetic than iron. I’ll see if I can track down a soft iron nut and bolt. All of the hardware stores around me only carry the stainless stuff

 

[Baluncore]

All of the hardware stores around me only carry the stainless stuff

The silver surface could be zinc plate on a carbon steel bolt, which should not be a problem.
I cannot read what is written on the head of the bolt you used. What does it say?
If the bolt head is marked 304 or 316 then it is stainless steel and will need to be changed.

 

[S_Noakes]

The silver surface could be zinc plate on a carbon steel bolt, which should not be a problem.
I cannot read what is written on the head of the bolt you used. What does it say?
If the bolt head is marked 304 or 316 then it is stainless steel and will need to be changed.

The head of the bolt says A2-70 and “THE”. What number bolt is the best?

 

[S_Noakes]

The silver surface could be zinc plate on a carbon steel bolt, which should not be a problem.
I cannot read what is written on the head of the bolt you used. What does it say?
If the bolt head is marked 304 or 316 then it is stainless steel and will need to be changed.

Here’s the bag it came out of

 

[Baluncore]

They are stainless steel.
"THE" is the manufacturer registration code, which makes failures traceable.
Google A2-70 and you will get; "When we say A2-70 it generally means that the bolt / screw is from SS 304 grade and has an ultimate tensile strength as 70 kg or 700 n/mm2."

You must replace the bolt with mild or carbon steel. Use the cheapest lowest grade available.
I don't know your supplier so I don't know the national numbers used.

 

[S_Noakes]

The silver surface could be zinc plate on a carbon steel bolt, which should not be a problem.
I cannot read what is written on the head of the bolt you used. What does it say?
If the bolt head is marked 304 or 316 then it is stainless steel and will need to be changed.

I looked into it and the A2 signifies 304, while 70 is related to the hardness. What number is recommended?

 

[S_Noakes]

They are stainless steel.
"THE" is the manufacturer registration code, which makes failures traceable.
Google A2-70 and you will get; "When we say A2-70 it generally means that the bolt / screw is from SS 304 grade and has an ultimate tensile strength as 70 kg or 700 n/mm2."

You must replace the bolt with mild or carbon steel. Use the cheapest lowest grade available.
I don't know your supplier so I don't know the national numbers used.

Posted at almost the exact same time. Oops. Lowe’s is my main supplier, but Home Depot and Ace Hardware are also options

 

[artis]

@S_Noakes , forget the bolt markings, just take one of your neodymium magnets and stick it to the bolt with your fingers, if the magnet doesn't stick, then it;'s stainless if it sticks then it;'s iron. You can use the same technique in store before buying the bolts, just take the right size bolt you want and apply a magnet test.

Other simple points to make. First of all your shaft bearings seem like made out of bolt nuts from what I can tell , what is your shaft made from , metal?
Now bolt nuts are very bad bearings, they have sharp grooves and high friction which might be one reason nothing wants to move.
I suggest just find a piece of plastic that is one of those slippery ones like on some food packaging , attach it to your frame, and make a hole which is just a bit larger than your shaft. Get a few drops of cooking oil on the shaft where it meets the plastic and you will be far better off than with these metal bolt nuts.

Another thing, do you have a compass ? If not take one of your magnets (just one) label one side of the magnet (one pole) with a marker and apply current to your coils, then put the labeled magnet side to each side of the rotor and see , one side should repel the magnet , the other side should attract it, this way you can know whether your wire wound direction is correct because maybe you have wound the wire in wrong directions and your rotor has the same pole on each end?Also check whether your stationary magnets are correct polarity, different pole on each side.Also remember this is a two pole motor, two pole motors have lower torque than motors with more poles like 4,6, etc. The reason is because each pole has to push/pull for a longer distance/ more degrees, than if there were more poles.

Finally check the placement of your commutator, as others pointed out. It is crucial at which point the current is switched , if if happens at the wrong moment instead of a motor you simply get an electromagnet which could also be the reason why nothing turns and everything sticks.Finally if you can maybe you can get a hold of a smaller lighter car battery , 12v DC.
12v Dc is safe but a car battery is much more rugged and fully charged will give you much time to play around , tests for errors. A 9v flat handheld battery will dry out fast and can also get hot because it's small and has poor heat sinking.

 

[S_Noakes]

@S_Noakes , forget the bolt markings, just take one of your neodymium magnets and stick it to the bolt with your fingers, if the magnet doesn't stick, then it;'s stainless if it sticks then it;'s iron. You can use the same technique in store before buying the bolts, just take the right size bolt you want and apply a magnet test.

Other simple points to make. First of all your shaft bearings seem like made out of bolt nuts from what I can tell , what is your shaft made from , metal?
Now bolt nuts are very bad bearings, they have sharp grooves and high friction which might be one reason nothing wants to move.
I suggest just find a piece of plastic that is one of those slippery ones like on some food packaging , attach it to your frame, and make a hole which is just a bit larger than your shaft. Get a few drops of cooking oil on the shaft where it meets the plastic and you will be far better off than with these metal bolt nuts.

Another thing, do you have a compass ? If not take one of your magnets (just one) label one side of the magnet (one pole) with a marker and apply current to your coils, then put the labeled magnet side to each side of the rotor and see , one side should repel the magnet , the other side should attract it, this way you can know whether your wire wound direction is correct because maybe you have wound the wire in wrong directions and your rotor has the same pole on each end?Also check whether your stationary magnets are correct polarity, different pole on each side.Also remember this is a two pole motor, two pole motors have lower torque than motors with more poles like 4,6, etc. The reason is because each pole has to push/pull for a longer distance/ more degrees, than if there were more poles.

Finally check the placement of your commutator, as others pointed out. It is crucial at which point the current is switched , if if happens at the wrong moment instead of a motor you simply get an electromagnet which could also be the reason why nothing turns and everything sticks.Finally if you can maybe you can get a hold of a smaller lighter car battery , 12v DC.
12v Dc is safe but a car battery is much more rugged and fully charged will give you much time to play around , tests for errors. A 9v flat handheld battery will dry out fast and can also get hot because it's small and has poor heat sinking.

Thanks for your response.

1) the nuts aren’t bearings, they are glued to the shaft to prevent it from moving side to side.

2) the bolts I have currently are magnetic, but very weakly.

3) I have verified that the magnet poles are correct (north on one side, south on the other)

4) how should the commutator be oriented? Could someone post a picture that I can try to emulate?

5) I have been using a wall-plug power supply that produces 13.8 volts and 3 amps for testing purposes.

 

[Baluncore]

I guess you are in USA.
Lowe's stock = Hillman, Zinc-Plated, Hex Bolt; In the size you need.

 

[S_Noakes]

@S_Noakes , forget the bolt markings, just take one of your neodymium magnets and stick it to the bolt with your fingers, if the magnet doesn't stick, then it;'s stainless if it sticks then it;'s iron. You can use the same technique in store before buying the bolts, just take the right size bolt you want and apply a magnet test.

Other simple points to make. First of all your shaft bearings seem like made out of bolt nuts from what I can tell , what is your shaft made from , metal?
Now bolt nuts are very bad bearings, they have sharp grooves and high friction which might be one reason nothing wants to move.
I suggest just find a piece of plastic that is one of those slippery ones like on some food packaging , attach it to your frame, and make a hole which is just a bit larger than your shaft. Get a few drops of cooking oil on the shaft where it meets the plastic and you will be far better off than with these metal bolt nuts.

Another thing, do you have a compass ? If not take one of your magnets (just one) label one side of the magnet (one pole) with a marker and apply current to your coils, then put the labeled magnet side to each side of the rotor and see , one side should repel the magnet , the other side should attract it, this way you can know whether your wire wound direction is correct because maybe you have wound the wire in wrong directions and your rotor has the same pole on each end?Also check whether your stationary magnets are correct polarity, different pole on each side.Also remember this is a two pole motor, two pole motors have lower torque than motors with more poles like 4,6, etc. The reason is because each pole has to push/pull for a longer distance/ more degrees, than if there were more poles.

Finally check the placement of your commutator, as others pointed out. It is crucial at which point the current is switched , if if happens at the wrong moment instead of a motor you simply get an electromagnet which could also be the reason why nothing turns and everything sticks.Finally if you can maybe you can get a hold of a smaller lighter car battery , 12v DC.
12v Dc is safe but a car battery is much more rugged and fully charged will give you much time to play around , tests for errors. A 9v flat handheld battery will dry out fast and can also get hot because it's small and has poor heat sinking.

Also, shaft is a carbon fiber rod.

 

[S_Noakes]

I guess you are in USA.
Lowe's stock = Hillman, Zinc-Plated, Hex Bolt; In the size you need.

Yep, USA.

I’ll go to Lowe’s and see if they have those, thanks.

 

[artis]

This is what I was basing my design off of.

Also don't expect anything near what the title of this video says. That handmade motor comes nowhere close to 21,000 RPM , if it did it would explode to pieces and the shrapnel would probably kill/badly injure the author of the video.

He simply measures the RPM wrong and gets a wrong result. Based on the camera shutter artifacts it seems the motor spins at a couple thousand RPM which is already magically good for a poor and simple construction like this.

 

[S_Noakes]

Also don't expect anything near what the title of this video says. That handmade motor comes nowhere close to 21,000 RPM , if it did it would explode to pieces and the shrapnel would probably kill/badly injure the author of the video.

He simply measures the RPM wrong and gets a wrong result. Based on the camera shutter artifacts it seems the motor spins at a couple thousand RPM which is already magically good for a poor and simple construction like this.

I knew that the 21,000 rpm was unrealistic, I was just looking for something that moved fast.

 

[artis]

1) the nuts aren’t bearings, they are glued to the shaft to prevent it from moving side to side.

2) the bolts I have currently are magnetic, but very weakly.

3) I have verified that the magnet poles are correct (north on one side, south on the other)

4) how should the commutator be oriented? Could someone post a picture that I can try to emulate?

5) I have been using a wall-plug power supply that produces 13.8 volts and 3 amps for testing purposes.

Ok , so I think you should redesign your motor somewhat, first of all why need the nuts in the first place ? If you mean to stop axial movement then I suggest simply buy some small ball bearings like the guy in the video , they will give you much less friction and also work as axial stops.

PS. if you have carbon fiber shaft, what is it rolling against? what is it rotating in ?

As for the commutator I'll give you a hint see if you can figure it out, it should be oriented in such a way so that the current goes in the coils and the coil S pole is attracted to the stator magnet N pole and coil N pole is attracted to stator magnet S pole, the moment your rotor has turned to the position where it's S pole is directly towards stator N pole and vice versa the current should stop, because as the rotor will try to move past this position due to inertia you don't want the current to still be applied in the same direction as that would pull the rotor back to the position is already was in.

So you want your current ON when the rotor is 90 degrees away from your stator pole and you want it OFF when it has reached the stator pole and is exactly at it , then the inertia moves the rotor further where it again reaches the position of being 90 degrees away from stator poles and now your current is applied in opposite direction and the rotor again moves in place, the current shuts off once more and the cycle repeats from starting position.

 

[S_Noakes]

Ok , so I think you should redesign your motor somewhat, first of all why need the nuts in the first place ? If you mean to stop axial movement then I suggest simply buy some small ball bearings like the guy in the video , they will give you much less friction and also work as axial stops.

As for the commutator I'll give you a hint see if you can figure it out, it should be oriented in such a way so that the current goes in the coils and the coil S pole is attracted to the stator magnet N pole and coil N pole is attracted to stator magnet S pole, the moment your rotor has turned to the position where it's S pole is directly towards stator N pole and vice versa the current should stop, because as the rotor will try to move past this position due to inertia you don't want the current to still be applied in the same direction as that would pull the rotor back to the position is already was in.

So you want your current ON when the rotor is 90 degrees away from your stator pole and you want it OFF when it has reached the stator pole and is exactly at it , then the inertia moves the rotor further where it again reaches the position of being 90 degrees away from stator poles and now your current is applied in opposite direction and the rotor again moves in place, the current shuts off once more and the cycle repeats from starting position.

I wanted to use ball bearings, but couldn’t really find any locally, and shipping for most of these parts takes upwards of two weeks to reach my location.

I think I understand what your saying about the commutator, I’ll look at it and see what I can do.

 

[artis]

Also the commutator contacts don't need to be as long , they can have more insulation distance between them , this way you will make sure the current is supplied only at the right moment and the current feeding wires don't overlap on both plates during each rotation which brings a moment of short circuit.

 

[S_Noakes]

Also the commutator contacts don't need to be as long , they can have more insulation distance between them , this way you will make sure the current is supplied only at the right moment and the current feeding wires don't overlap on both plates during each rotation which brings a moment of short circuit.

thanks for the advice.

I’m using copper wire for the contacts, and have them touching the commutator at 180 degrees apart.

 

[artis]

@S_Noakes ok let me make this simpler for you , your magnets are horizontally placed, take your rotor and place it so that the bolt and coils are situated vertically , which would mean 90 degrees away from your horizontal magnets. Now in this position apply the commutator plates in such a way that the current wires touch the plates only at the beginning of this moment when the rotor is in the vertical position, then make the plates only as long so that the wires touch them until the rotor moves 90 degrees and the bolts are matching the horizontal magnets, at this moment the current wires should stop touching the plates, then there should be a moment where the wires are not touching the plates and they should begin to touch them only after the rotor has moved 90 degrees more and is again in the vertical position.

see the simple paint file i attached, the brown wires are your current wires , the commutator is the green part, magnets red squares.

 

[S_Noakes]

@S_Noakes ok let me make this simpler for you , your magnets are horizontally placed, take your rotor and place it so that the bolt and coils are situated vertically , which would mean 90 degrees away from your horizontal magnets. Now in this position apply the commutator plates in such a way that the current wires touch the plates only at the beginning of this moment when the rotor is in the vertical position, then make the plates only as long so that the wires touch them until the rotor moves 90 degrees and the bolts are matching the horizontal magnets, at this moment the current wires should stop touching the plates, then there should be a moment where the wires are not touching the plates and they should begin to touch them only after the rotor has moved 90 degrees more and is again in the vertical position.

see the simple paint file i attached, the brown wires are your current wires , the commutator is the green part, magnets red squares.View attachment 291198

Thanks!

The picture helps. My commutator “cuts” are aligned with the coils. If I understand correctly, my commutator needs to be rotated so that they can operate in the manner above. I think the commutator halves need to be smaller as well

Sorry about this. This is all kind of new to me.

Below is how my motor is currently set up. I’ll make changes like a new bolt and adjust the commutator, and then get back to you all.

thanks for all the help!

 

[artis]

Yup @S_Noakes your drawing of the commutator shows it's wrong. as it turns and reaches the horizontal magnets the metal plates are still connected , so now your motor becomes an electromagnet , the poles just stick to the magnets and stay there because the current doesn't end ,
well it might end on a second thought but that depends on the speed of the rotor , if the plates are too close , they might short circuit the wires.

 

[S_Noakes]

Yup @S_Noakes your drawing of the commutator shows it's wrong. as it turns and reaches the horizontal magnets the metal plates are still connected , so now your motor becomes and electromagnet , the poles just stick to the magnets and stay there because the current doesn't end , is not switched off at that moment.

Do you see your own mistake ?

Yes, I do. Thanks. That explains what my motor has been doing. I'll make the changes. Thanks for walking me through that.

 

[artis]

@S_Noakes on a second thought you don;t have to completely redo the whole thing, you can leave it almot as in your drawing but make the plates shorter at first , so there is more gap of insulation and the wires don't arc through.
Also position them such that the moment the rotor pole reaches exactly at the stator magnet the current is switched off , then a little bit of dead time/ insulation and only then the current switches on again to pull the rotor further.

The moment the rotor pole reaches the stator magnet is crucial because if the current stays ON for even a bit longer then it drags the rotor back and this is like "one step forward, half step back" kind of situation.

 

[Averagesupernova]

I built an electric motor similar to the one in question in this thread. My commutator plated were positioned exactly as the ones in this motor. It ran fine.

 

[S_Noakes]

I built an electric motor similar to the one in question in this thread. My commutator plated were positioned exactly as the ones in this motor. It ran fine.

Were there any other major differences between my motor and your motor?

 

[Rive]

I think this stainless thing is a dead end. In this configuration even a wood stick should work - to be honest, it should work better than real magnetic material.
Check/switch the polarity of the contacts.

 

[S_Noakes]

I think this stainless thing is a dead end. In this configuration even a wood stick should work - to be honest, it should work better than real magnetic material.
Check/switch the polarity of the contacts.

Switching polarity through the contacts has no discernible effect. The magnets will vibrate slightly and the motor will get hot. That’s it.

 

[Rive]

Without current running, how much force is needed to turn the rotor from horizontal to vertical?
Also,by any chance do you have the usual stuff (iron dust and paper) to actually check/display magnetic fields?

 

[S_Noakes]

Without current running, how much force is needed to turn the rotor from horizontal to vertical?
Also,by any chance do you have the usual stuff (iron dust and paper) to actually check/display magnetic fields?

Almost no resistance unmoving the rotor from horizontal to vertical.

no, I don’t have iron dust. Where would I get some?

 

[Rive]

Practically everything what can be a problem was already mentioned. So maybe it's time to actually see those lines.
My bet is on your rotor, though. Something is fishy there...

 

[Averagesupernova]

Were there any other major differences between my motor and your motor?

My motor had a wound field. .75 inch wide x .25 inch thick bent in a U shape wound with doorbell wire. The field was wound in such a way as to be continuous windings in the same direction. However, I skipped winding on the base of the U in order to run screws through it for mounting. Armature was a dowel with a hole drilled and a .25 inch bolt driven through the hole. It was also wound continuously in one direction. It's still around, I'll dig for it.

 

[tech99]

I have had a lot of difficulty making model motors, but the following link shows a design which is simple and easy to make.

 

[Averagesupernova]

Switching polarity through the contacts has no discernible effect. The magnets will vibrate slightly and the motor will get hot. That’s it.

At one point you mentioned a 9V battery. You also mentioned using a wal-wart. Vibration indicates you are using an AC source.

 

[Baluncore]

Switching polarity through the contacts has no discernible effect. The magnets will vibrate slightly and the motor will get hot. That’s it.

When not rotating, the armature gets hot because the current is limited only by the wire resistance and supply source resistance. When rotating, the current and therefore the magnetic field through the armature is alternated by the commutator, so armature inductance then limits the current.
The magnetic iron core is needed to increase the inductance of the rotating armature.

You will need a better armature, or better bearings and a lower voltage.

The silly RPM readings in the video are probably due to six reflections per revolution of the armature, two from the bolt ends and four from the hexagon sides. There are too many possibilities for errors there.

 

[Averagesupernova]

Collected a bit of dust over the years but you should get the idea. I didn't really have much to go by when I built this, I just tried it in a way I thought it should work and it did. 6 volt lantern battery gets it moving fast enough. Not balanced all that well so it wasn't something to just let run. Series wound so it will over speed easily.