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Aug 14, 2019 at 17:27 comment added Russell McMahon Micheal Johnson's 3 comments are good enough to be your answer.
Aug 14, 2019 at 16:21 comment added micheal65536 So the short answer is that this simple design will in fact work and will in fact turn in either direction but once it's turning the inertia of the rotating part will keep it going in the same direction even under some load. However as others have pointed out a real-world DC motor will almost certainly use an improved (but more complex) design that ensures that the motor will always turn in the same direction and avoid arcing, and I have also disassembled real DC motors and seen this for myself.
Aug 14, 2019 at 16:17 comment added micheal65536 Regarding the shorting of the contacts during the crossover, this did also happen with my motor however it doesn't stop the motor as again the inertia will carry it across. However it will cause arcing between the brushes and the contacts and create a sudden high-current spike on the power supply, both of which are a bad idea. In my case, adjusting the size of the contact area between the brushes and the contacts so that it was smaller than the gap between the two contacts avoided this.
Aug 14, 2019 at 16:17 comment added micheal65536 This has somewhat been covered in some of the other answers and comments but I would like to add that I have in fact built such a motor and it does in fact work. Once the motor is up to speed, the inertia of the rotating part will keep it turning in the same direction instead of reversing direction. If I remember correctly, this design of motor can however be started in either direction (e.g. if you stop the shaft with your fingers and then flick it back the other way).
Aug 14, 2019 at 11:21 answer added Dmitry Grigoryev timeline score: 4
Aug 14, 2019 at 9:00 history tweeted twitter.com/StackElectronix/status/1161563150191403008
Aug 14, 2019 at 7:34 history became hot network question
Aug 14, 2019 at 6:50 vote accept Nicholas
Aug 14, 2019 at 0:23 comment added TimWescott DC motors are really super cheap. Get some (or get some toys with them from a second hand shop) take them apart, and look inside.
Aug 14, 2019 at 0:05 answer added hacktastical timeline score: 12
Aug 13, 2019 at 23:39 comment added MarkU I think that’s a simplified diagram, real DC motor commutators have at least 3 contacts if I remember correctly. AFk(phone) so cant easily find a better image...
Aug 13, 2019 at 23:26 answer added DKNguyen timeline score: 5
Aug 13, 2019 at 23:25 review First posts
Aug 14, 2019 at 13:38
Aug 13, 2019 at 23:24 history edited Nicholas CC BY-SA 4.0
added image
Aug 13, 2019 at 23:21 history asked Nicholas CC BY-SA 4.0