5 Build Your Own Electric Car: DC Motor Basics

[Music] obviously one of the biggest differences between a gasoline car in an electric car is that an electric car has an electric motor we got our electric motor out of a forklift and I've got a different motor here did you show you the basics of how a series wound electric motor works all electric motors work basically the same we're going to be using a series wound forklift motor in any motor it's one magnetic field pressing against another magnetic field that makes the motor spin now there's more than one way to do that in smaller motors it might be a permanent magnet motor that means one of the set of magnets are mineral magnets permanent magnets and then the other magnetic field is created by an electromagnet the electricity from the batteries through the motor now those motors are limited in power because of how how strong those permanent magnets are now if you instead have two electromagnetic fields pushing against each other to spin the motor that's typically a series wound motor there are some other style motors we're not going to cover those also this is a DC motor DC motors use electricity straight from batteries they don't need any circuitry that converts the DC power of the batteries to AC to then run an AC motor so these are going to be the most simple durable robust powerful motors that you're going to be easily able to get your hands on and we have just tons of electric forklifts all over the place in factories and warehouses and in junkyards so if you go to a junkyard odds are that you can find a pretty good motor for not much money so let's take a look at some of the parts on this motor here this came out of a forklift this was the drive motor the style of forklift was one of those kind of three-wheeled ones where there was a single drive wheel in the back and the whole motor rotated on that wheel to steer this is a series wound motor right up here we have an identification play that tells us a little bit about it it tells us that it's a 36 volt motor it also has a part number on there which we could go on the internet look up and find some more information on this motor now I took a couple of bolts off then here just to open it up a little bit make it a little easier to see in here but start with from over here this is the drive end the drive shaft and if I spin this you can see inside here it's not just the drive shaft that's spinning but there's also a large electromagnet inside that's all part of it that all rotates together that whole assembly is called the rotor or the armature now you also see right inside here is a bearing and the same on the back so that entire rotor or armature and the drive shaft is all supported on those two bearings the whole electric motor is really a very straightforward thing we've got kind of this end cap that end cap the middle part and that armature that's there's really only about four parts to this whole thing so it's real easy to take apart typically to take it apart you're gonna have maybe four or six bolt holes on the end you pull those bolts out if you have any bolts on the opposite end you'll pull those out too and then you just need to yank this whole thing off and you want to support the shaft as you do that so that the inside parts don't whack against each other and damage to the motor now another thing you're going to notice on this motor is that there's four power connections and you're thinking uh-oh this doesn't make sense because the battery only has two power connections a positive and a negative so the motor should have a positive and a negative as well well that's true sort of this is a series wound motor and that means that the electricity that runs through the inside the armature and makes that electrical field and the electricity that runs through the field coils these magnets that are on the outside the stator it's all the same electricity and it runs in series between the two it runs through the one and then it loops and goes through the other and then goes back to the battery so that's what for power connections are for two of these are for the armature and two of them are for the stator so on a motor that has four power connections on it what we're going to do is use a cable or some piece of copper bar to connect two of the power connectors to each other now another thing that's kind of interesting here is how you run a series wound motor the opposite direction if you put the motor in the car and the motor spins the wrong way you're gonna have multiple years of reverse and only one forward gear so we want to make sure the car goes forwards the trick with this is if you find that the motor spins the wrong direction you simply reverse that criss-crossing power cable so that that we were reversing the power only on the one magnetic field or the other not both if we just swapped the connections on the battery cable we'd be reversing both fields and the motor would still spin the same direction now if you only have two power connections on there it could possibly be a permanent magnet motor or the other possibility is it's still a series wound motor but that connection is on the inside and you can reverse that it's just gonna be a little bit more work because you got to take this whole thing apart go in find that wire cut it and redo that yourself so that's a little bit of a pain for connections makes this a lot easier also if you want you could set up your car to have a power switch that makes your motor spin of either direction now in my car I didn't do that I only designed it to go the one direction and I just used reverse gear now some motors not only have a drive shaft but they'll also have a tail shaft coming off the other end the motor that I chose to use for my car did have a tail shaft on it but I actually ended up having to cut it off because the motor was too long to fit in the front of the car that tail shaft would have gone right into the passenger side tire and that would have been not good for anybody now on your motor it may actually have a horse power rating on this little identification plate right here the most important thing to keep in mind for horse power on an electric motor is it has almost nothing to do with horsepower on a gasoline engine they really are that different for example I also have an electric motorcycle and the motor on that's rated for eight horsepower and yet without a transmission I can just twist my throttle and stick right on the tail of any Harley no problem horsepower really doesn't mean a whole lot on electric Motors they have a lot of torque they just have that Fe Go Power and in my metro I can actually start from a dead stop in any gear including v without a clutch that's the difference between torque and horsepower another thing that we'll notice on a motor like this is that it uses a face mount design we're able to put bolts through from this face portion into the adapter plate and that's what's actually going to hang the motor onto the transmission some other motors sometimes they might have a foot coming off the bottom and if we were using a motor like that we would have to make some sort of an l-shaped adapter plate for the motor to sit on the foot and then still line up with with the transmission and that adapter plate for everything to go together so let's take just a little bit closer look at this motor here as I said I already pulled out the the bolts out of the end of it so what I'm gonna do now is we're just real gently gonna pull this motor apart so now you have a little bit better view here we've got our drive shaft here's the drive shaft you can see it has a keyway on there and that's what would be used to attach it to a pulley or some other power connection through the middle here this is our electromagnet this is what all the electricity goes through and creates a magnetic field as it spins this right here believe it or not is not bubblegum but rather when they make the motor they add a little bit of a putty weight that balances the motor so that it stays nice and smooth as it spins down here this is the end bearing and this part right here is called the commutator and the commutator is a pretty important part of the motor what happens there is each of these copper bars is separated by a slot and these go over through this copper through the iron and creates the magnetic field and because each of these is separated every time the brushes hit one of these from one to the next it alternates the electric field to make a push pull push pull effect that spins the motor around like this now inside the shell here this is one of the coils this motor has four of them some motors might have six basically they're just copper coiled around a iron block inside there and that's the magnetic field that this one fights against to make the spinning motion now in the very back of this we've got the brushes and the commutator here lines up with the brushes now also over here this is usually called the drive end sometimes abbreviated de and here and over here is called the commutator end sometimes abbreviated as Cee now what you're looking at is the inside of the motor around the edges you can see those field coils right here when you get your motor and pull it apart you're going to want to take a look at that coils and make sure that the varnish doesn't look like it's worn off if it is you may want to pull out the screws that hold these in take them out clean them up and revarnished them I did that with just a can of a spray-on green varnish it really worked great and it was just uh Oh an hour two in the afternoon to really clean that all up in the back are the brushes and the brushes are basically just carbon a little blocks of carbon that conduct the electricity and they have little Springs so you can see here how the brush can slide up and down as its pressed in with that little spring well what you're going to want is some sort of a a screwdriver or a pick or something you can stick that through from the outside and pull back the spring and then when you do that you can slide the brush up and let the spring press back against it to hold the brushes out of the way and you're always going to want the brushes held out of the way when you're trying to get the armature in and out you know you also want to inspect those brushes to make sure they don't look burnt that they're not cracked that they're in good condition if you need new brushes they're commonly available consult the yellow pages or the internet to find a forklift repair shop somewhere near you and brushes ran me about $50 mine were we're in really bad condition there wasn't much left to them so I needed new ones so I paid 50 bucks for the motor 50 bucks for the brushes and you know five bucks for the can of epoxy and with a little elbow grease I basically had a brand new motor for about a hundred dollars here is another view of the commutator end this time I've got the commutator end bolts removed just to make a little room so we can see in here this here is the commutator itself here's one of the brushes that brush is pulled back right now this little spring holds it in there so if we pull that back that lets us slip the brush in and then that little hook goes right over the top of the brush to push it down just gently against the commutator now it's not going to do it right right now because we've got this pulled apart but just to show you how that works so we do just want to make sure that all the brushes are pulled back when we slide that back in there and again always be careful with the commutator and how things line up so you're not bashing anything around on the inside there so we'll just use this little scribe be punchy thing here to pull that pull the brush back out let the spring rest on the side of the brush and it'll keep it held out in the outward position like that so the motor that I ended up using for my project came out of a Nissan forklift motor it really didn't have an identification plate on it in fact the thing was just amazingly rusty when I got it I bought it for 50 bucks out of a guy's garage where it was still in a forklift motor that he was taking apart he was using the hydraulics to build a lift for his car for his garage I did make sure that the motor itself spun first I brought with me one of those portable jump starter devices kind of the battery with the jumper cables on it and I put that on the motor just put you know put the two connections right on the power posts and I brought with an extra little piece of cable to make the connections and it did spin barely I actually had to spin the drive shaft first and then it went but it's spun so I figured that was a good sign I brought the motor home I took all the end bolts out I took the motor apart I cleaned it up i revarnished the field coils I got all the grease out of there I put it all back together it was basically a couple hours worth of work and when I was done I basically had a brand new motor the brushes I picked up at a local forklift repair place I paid $50 for a set of four brushes brand new they had them right there in stock very easy to replace you just have to pull the old ones out pull out one screw that holds in the electrical connector for the brush put the new one in put that screw back in slide the brush back into position and you're ready to go again electric motors are very simple and very durable I can't imagine taking apart a gasoline engine and rebuilding it in one afternoon I wouldn't even know where to start but an electric motor for me never having done this before it really wasn't that tough so take a look around you should be able to find a good used serial series wound forklift motor at a junkyard possibly through someplace like Craigslist you might want to check around at electrical rebuilders repair shops there might even be a forklift rebuilding place near you give them a call see what you can find and I'm sure you'll be able to find a good used motor for not too much money

Channel: BenjaminNelson

Views: 1,224,589

Rating: 4.7962637 out of 5

Keywords: DIY Electric car, electric car motor, electric car conversion, Ben Nelson, Geo Metro, build, do it yourself, conversion, 300mpg.org, DC motors, series wound, how motors work, DC motor basics

Id: UnLEy8p9Xu8

Length: 14min 34sec (874 seconds)

Published: Sun May 06 2018