Home-made electrical motor not running

  • #36
artis
1,327
878
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.
 
  • Like
Likes berkeman and S_Noakes
  • #37
S_Noakes
23
1
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.
 
  • #38
artis
1,327
878
@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.
 
  • #39
Averagesupernova
Science Advisor
Gold Member
4,199
1,040
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.
 
  • #40
S_Noakes
23
1
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?
 
  • #41
Rive
Science Advisor
2,443
1,859
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.
 
  • #42
S_Noakes
23
1
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.
 
  • #43
Rive
Science Advisor
2,443
1,859
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?
 
  • #44
S_Noakes
23
1
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?
 
  • #45
Rive
Science Advisor
2,443
1,859
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...
 
  • #46
Averagesupernova
Science Advisor
Gold Member
4,199
1,040
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.
 
  • #47
tech99
Science Advisor
Gold Member
2,611
1,158
I have had a lot of difficulty making model motors, but the following link shows a design which is simple and easy to make.
 
  • #48
Averagesupernova
Science Advisor
Gold Member
4,199
1,040
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.
 
  • #49
Baluncore
Science Advisor
12,045
6,160
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.
 
Last edited:
  • #50
Averagesupernova
Science Advisor
Gold Member
4,199
1,040
KIMG1455.JPG
KIMG1456.JPG
KIMG1458.JPG

KIMG1457.JPG


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.
 
  • Like
Likes artis and Baluncore
  • #51
artis
1,327
878
@Averagesupernova wow I like your motor, the dusty looks of it and the wooden shaft it just seems like a museum example from the time of Nikola Tesla. It almost has that feel that it was found by archeologists.
#Iron age electronics :biggrin:
Was that a school project from long ago?


Switching polarity through the contacts has no discernible effect. The magnets will vibrate slightly and the motor will get hot. That’s it.
If this type of motor does that - vibrates without ever turning a single rotation then it can only be because you applied AC instead of DC to it. Check whether your power supply that you mentioned is DC output or AC.
 
  • Like
Likes Averagesupernova
  • #52
Averagesupernova
Science Advisor
Gold Member
4,199
1,040
@Averagesupernova wow I like your motor, the dusty looks of it and the wooden shaft it just seems like a museum example from the time of Nikola Tesla. It almost has that feel that it was found by archeologists.
#Iron age electronics :biggrin:
Was that a school project from long ago?
I've felt 'old' for a while now, but your comment makes me feel really old. Lol. I was very interested in electricity as a kid and it was just a project I wanted to do. I modified several world book encyclopedia projects and this is the result.
 
  • #53
artis
1,327
878
I've felt 'old' for a while now, but your comment makes me feel really old. Lol. I was very interested in electricity as a kid and it was just a project I wanted to do. I modified several world book encyclopedia projects and this is the result.
I'm sorry for making you feel old, I meant just a nice humor, but hey don't worry we all will get there.
Anyway the wooden shaft probably made the whole thing vibrate like an "earthquake machine"
 
  • Like
Likes Averagesupernova
  • #54
Averagesupernova
Science Advisor
Gold Member
4,199
1,040
I'm sorry for making you feel old, I meant just a nice humor, but hey don't worry we all will get there.
Anyway the wooden shaft probably made the whole thing vibrate like an "earthquake machine"
Don't worry about making me feel old. Every now and then we all need a reminder. It didn't move across the table as it ran but the small nails driven into the ends of the shaft are a concern for loosening up when it gets up to speed.
 
  • #55
Shane Kennedy
53
12
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
 
  • #56
sophiecentaur
Science Advisor
Gold Member
27,805
6,323
I expect the cheapest soft iron bolt
I wouldn't have a clue where to get hold of one of them. The only soft iron you can get hold of easily is the laminations in a transformer kit and real horse shoe nails, which are extremely bendy (from craft shops as well as farriers, I think). Mild steel is what hardware and DIY shops sell and will do just as well so the OP needn't be chasing all over to get Iron.

It's staggering what problems that 'beginners' projects present when wound components are involved. It's so often either down to open or short circuits. It wasn't a problem in my childhood when the available wire was cotton covered.

I remember when I was teaching secondary Science, there were some truly horrible 'Electric Motor Kits' which the kids were expected to wind, assemble and run. A real nightmare and it used to involve me leaning over each group of kids and manually holding wires to a naff commutator arrangement to get each motor to turn. I bet other UK teachers will recognise my experience with those pesky motor kits.
 
  • #57
StandardsGuy
145
8
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
I don't see any brush contacts. You haven't finished it yet.
 
  • #58
Baluncore
Science Advisor
12,045
6,160
Mild steel is what hardware and DIY shops sell and will do just as well so the OP needn't be chasing all over to get Iron.
One manufacturer who wanted to make the best electromagnets purchased 100 tonne of electrical steel for the first production run. Their first magnets would not turn off because of hysteresis in the steel. When they used the much cheaper (and easier to machine) mild steel, (as originally specified), the problem was resolved. That was a good example of management thinking more expensive material would be better, when the converse was true.

In the case for this OP motor, the 304 stainless steel bolt seemed like a good idea at the time. At least it was easier to drill the hole through the shank than it would have been with a 316 SS bolt. But a mild steel bolt would have been easier still. Unfortunately the cheapest black bolts are no longer available in hardware stores, they are all plated with zinc, which is conductive, reduces AC magnet efficiency, and slows the magnetisation. Maybe experiment later with a dip in an acid (such as rust converter), to remove the zinc, might make a difference.

Horseshoe nails were once cut with a cold chisel from wrought iron, which was the closest thing to pure iron. Wrought iron could be forge welded with a hammer, but was more expensive than mild steel. Now that electric welding is used for fabrication, wrought iron has faded into history, and cheaper mild steel products are stronger for the same weight. Electric welding also replaced soft iron rivets in about 1940, doing away with another source of magnet core.

It's staggering what problems that 'beginners' projects present when wound components are involved. It's so often either down to open or short circuits. It wasn't a problem in my childhood when the available wire was cotton covered.
It was for me. I wound my first unsuccessful electromagnet with double strength button thread, because it was the closest I could find to DCC. Later I met a technician who, while following the same book, had done exactly the same thing.
 
  • Haha
Likes sophiecentaur
  • #59
sophiecentaur
Science Advisor
Gold Member
27,805
6,323
It was for me. I wound my first unsuccessful electromagnet with double strength button thread, because it was the closest I could find to DCC. Later I met a technician who, while following the same book, had done exactly the same thing.
It's amazing how this sort of error is not always spotted by people who should know better. I used to find that my fellow (by no means dumb) Science teachers were really rubbish at fault finding and getting experiments to work. At least we had two Lab Techs who could usually dig them out.
 

Suggested for: Home-made electrical motor not running

  • Last Post
Replies
5
Views
188
  • Last Post
Replies
4
Views
195
  • Last Post
Replies
7
Views
485
  • Last Post
Replies
1
Views
501
Replies
4
Views
471
  • Last Post
Replies
4
Views
323
Replies
5
Views
529
Replies
4
Views
273
  • Last Post
Replies
3
Views
484
Replies
2
Views
627
Top