DC Motor Tips

We recommend black motors, chrome motors dissipate heat too slow. We recommend the PRESTOLITE MDY-7070 ( Old School ) or the MHN-7001 ( Old School Plus ) four field motor because of its reliability and its easy to work on. Prestolite also makes a motor that is a two field called the MUE. The MUE is not as good as the other motors Prestolite makes though. The Prestolite motors have copper brushes and are much better than carbon brushes. Cheap foreign made motors ( Saco ) or whatever they call them, use pure copper for the commutator bars and it is too soft. Prestolite uses a copper and silver mix for the commutator for improved strength.

Improvements can be made on every motor used today. Most motors have ball bearing ventilated end caps. If the motor does not have ventilated end caps then you can remove the end cap and CAREFULLY drill out holes so the motor can breath. Make sure you develop a schedule to clean your motors periodically. Below are some improvements you can make to your motors and a good explanation on how to do it.

The best coupler key for your motor are the slotted TANG style. This is because they break easily to save your expensive pump heads from when the system is over locked or deadheaded. The MDY-7070 has a tang coupler and the MHN-7001 has a nine spline shaft. Recently Prestolite has sold off their winch motor division and these fine motors are no longer made. If you look around you may be able to find them with a little luck and some extra money.

Important: For longer motor life never use a setup right after charging the batteries. This sounds crazy but a setup that is wired for example at 48v will put out more than 48v and it will start destroying the motors. Wait 24 hours after charging to operate the setup when ever possible.

Prestolite

prestolite MDY7070

Above: A rare Prestolite MDY-7070.

DCMotorApart

MDY-7070 NEW

Above: A close up of a rare Prestolite MDY-7070.

MDY-7070 Custom-1

Above: A close up of rare custom Prestolite MDY-7070’s.

MDY-7070 Custom

Above: A rare collection of custom Prestolite MDY-7070’s.

Pump Diagram


Rebuilding a DC motor

Above: Here are two used armatures, you can see that the windings have been wrapped to prevent them from coming apart under high heat and Rpm's. The commutators on each of these armatures are also looking pretty bad, note the smearing and discoloration of the copper. Wrap fine grit sand paper around the commutators and twist until it cleans up and is smooth. Once it is sanded you'll notice that each bar of copper is separated by a thin piece of mica. Cheap foreign made motors use pure copper for the commutator bars and it is too soft for heavy use. Prestolite uses a copper and silver mix for the commutator for improved strength.

Above: Here are two used armatures, you can see that the windings have been wrapped to prevent them from coming apart under high heat and Rpm’s. The commutators on each of these armatures are also looking pretty bad, note the smearing and discoloration of the copper. Wrap fine grit sand paper around the commutators and twist until it cleans up and is smooth. Once it is sanded you’ll notice that each bar of copper is separated by a thin piece of mica. Cheap foreign made motors use pure copper for the commutator bars and it is too soft for heavy use. Prestolite uses a copper and silver mix for the commutator for improved strength.

Above: Here is the stator without the armature inside it. You can see the brushes are getting worn out. Brush dust is also all over the inside of this stator and must be cleaned out because the brush dust conducts electricity and may short out the motor. The brushes are one of the biggest causes of motor failure on your hydraulic pump. New brushes can be purchased at a local electric motor supply house. The best brushes have a high content of copper and the bad ones have a ton of carbon in them. High carbon content brushes don't tend to last very long. Most cheap motors come this way so be aware that you get what you pay for. The carbon brushes break down very quickly in high heat.

Above: Here is the stator without the armature inside it. You can see the brushes are getting worn out. Brush dust is also all over the inside of this stator and must be cleaned out because the brush dust conducts electricity and may short out the motor. The brushes are one of the biggest causes of motor failure on your hydraulic pump. New brushes can be purchased at a local electric motor supply house. The best brushes have a high content of copper and the bad ones have a ton of carbon in them. High carbon content brushes don’t tend to last very long. Most cheap motors come this way so be aware that you get what you pay for. The carbon brushes break down very quickly in high heat.

Above: The stator has been cleaned out at this point. The positive brushes are carefully removed from the brush holder by using something to pry the brush springs back. The brush holder is carefully removed from the stator by taking out three screws on the side of the stator. The positive brushes are attached inside the stator and the grounded brushes are attached to the brush holder. The old positive brushes are unsoldered and removed. The ground brushes are carefully removed from the brush holder using a small flat screwdriver and bending the tabs up that hold the wires.

Above: The stator has been cleaned out at this point. The positive brushes are carefully removed from the brush holder by using something to pry the brush springs back. The brush holder is carefully removed from the stator by taking out three screws on the side of the stator. The positive brushes are attached inside the stator and the grounded brushes are attached to the brush holder. The old positive brushes are unsoldered and removed. The ground brushes are carefully removed from the brush holder using a small flat screwdriver and bending the tabs up that hold the wires.

Above: The new positive brushes are now soldered in and wrapped up with electrical tape. Liquid electrical tape is used over the wires also and the insides of the stator are treated with liquid electrical tape. This prevents arcing at high voltages and protect things from the conductive brush dust..

Above: The new positive brushes are now soldered in and wrapped up with electrical tape. Liquid electrical tape is used over the wires also and the insides of the stator are treated with liquid electrical tape. This prevents arcing at high voltages and protect things from the conductive brush dust..

Above: The brush holder has been treated with the liquid electrical tape and the new ground brushes are installed on the holder. The brush assembly is installed back in using the three small screws. The armature is carefully installed and the end cap is put back on the motor. It's that simple. If your in a pinch this info will come in handy and you have nothing to lose by trying to fix it.

Above: The brush holder has been treated with the liquid electrical tape and the new ground brushes are installed on the holder. The brush assembly is installed back in using the three small screws. The armature is carefully installed and the end cap is put back on the motor. It’s that simple. If your in a pinch this info will come in handy and you have nothing to lose by trying to fix it.


Wrapping Armatures

Wrapping armatures prevents the wires from coming off the armature. This happens when the solder that is holding the wires becomes too hot and the spinning action of the motor opens up the wires.

Above: Most motors do come with wrapped armatures but some don't. If they are not you can wrap them with some fiberglass tape and a thin coat of high heat epoxy.

Above: Most motors do come with wrapped armatures but some don’t. If they are not you can wrap them with some fiberglass tape and a thin coat of high heat epoxy.

Above: Notice both sides of the armature are wrapped.

Above: Notice both sides of the armature are wrapped.


Insulating Brush Holders

Shorts can cause serious problems when you are running 48 Volts or more. Using liquid electrical tape can help with this common problem.

Above: A can of liquid electrical tape that you can find at a good hardware store.

Above: A can of liquid electrical tape that you can find at a good hardware store.

Above: You can see that there is a lot of bare metal in this motor where high voltages can arc and short out.

Above: You can see that there is a lot of bare metal in this motor where high voltages can arc and short out.

Above: Here is the brush holder with the armature removed.

Above: Here is the brush holder with the armature removed.

Above: The liquid electrical tape is put on the brush holder with care. Try to avoid getting the gunk on the brushes.

Above: The liquid electrical tape is put on the brush holder with care. Try to avoid getting the gunk on the brushes.

Above: This is what the brush holder will look like when you are done. Don't forget to coat the brush springs also.

Above: This is what the brush holder will look like when you are done. Don’t forget to coat the brush springs also.

Above: Here is the other side done on the stator to the right. Both sides need to be covered for this to work good.

Above: Here is the other side done on the stator to the right. Both sides need to be covered for this to work good.