Several times in the forums I have come across references to wanting to reverse the rotation of a motor, or someone looking for a replacement motor and upon locating one discovering that the direction of rotation is wrong for their application. There have been some interesting ways that this problem has been solved, requiring rework of the motor mount or creative belting paths. I am hoping that this pictorial instruction will remove a little fear from the chore of replacing a motor.
First of all I would like to say that electric motors are not magical, at least not completely. There is one closely guarded secret concerning the main ingredient in ALL electrical contraptions: The magic smoke! As long as you don’t accidentally release this and don’t attempt troubleshooting and modification while the plug is in the outlet you should be fine.
Some tools/ supplies you may /will need:
wire cutter for cutting wire and nylon ties and tails
soldering iron and solder or small crimp connectors
liquid tape if you want to use it
shrink wrap should you prefer
continuity tester/ VOM/ Ohm meter (any one of the three will do) Dont use 110 volts and a light bulb!
screwdrivers and wrenches appropriate for disassembly
Electric motors have been around for a long time. The basic theory is relatively simple. Over the course of time the manufacturing process has been refined in order to keep the cost of production down and increase the rate of production in any way possible. One way this is done is by using the same parts where ever possible and putting the same parts in the same places so there are fewer places for error along the line in the manufacturing process. They are a smart bunch! They use the same parts and market them as different products! The fact is that most single Phase low voltage motors in a horse power family use the same parts internally. For the most part any single phase motor can be easily changed to be any combination of voltage and rotation. Some are very easy and some take a little work. None are out of the scope of someone who can successfully use a volt ohm meter and make a good solder joint. If you are not familiar with soldering a crimp connector will usually do anyway.
This particular motor required digging out the windings as the manufacturer did not want to make it easy. Believe it or not the motor was speced out as a single rotation single voltage as many are on todays equipment for liability reasons. This is another reason why customer adaptable motors are much more expensive its not just the cost of the few extra pieces of wire and or the landing pad for the spade terminals. The manufacturer has to pay more for the liability insurance for this type of motor.
Of course you have to start by getting the sander disassembled far enough to access both ends of the motor. you wouldn’t really have to remove it from the base but I did. Take the shroud off the back of the motor and using a pry bar between the motor housing and the CENTER portion of the fan slide the fan off the shaft. Make alignment marks on the joint between the front bell housing and the body of the motor and do the same for the rear bell housing.
after removing the four through bolts on the motor (still installed in the above picture) Use a peice of wood to protect the end of the cooling fan end of the shaft and lightly tap the end of the shaft. Typically the rear bell housing will stay in place and the front bell housing will separate from the main body. remove the front housing and the armature and set aside. tip the motor up on the rear housing.
In these two pictures the white tubes cover the connection points of windings to line and capacitor leads.
carefully cut the nylon wire ties and discard. Also cut the cords where needed to release the connection points so they can be worked on and work them up and away from the windings. Carefully use only your fingers no screwdrivers pens scales prybars, hammers etc.
slide the sock back to expose the soldered connections. The blue wire o the left connects to one end of one winding. the other end of the blue wire connects to the capacitor. The white wire on the right has three winding wires connected to it.
being careful to remember where the wires are being disconnected,Either cut or unsolder the connections at the white and blue wires. you should now have six loose wire ends. The white wire and the three winding wires that were attached to it and the blue wire and its corresponding disconnected winding wire.
Our goal is to reverse the connection of the winding to the capacitor. We know that the winding wire to coming from the right that was connected to the blue wire is one end of the winding. We have a choice of three on the right. Eeny, Meeny, Miney, Moe, which wire is it I don”t know?, but I know how to find out. Set your meter to ohms (the horseshoe looking thingy). touch one lead to the wire on the left. Touch the other lead in turn to each of the three on the right. You want to find one that changes the reading on the meter. The other two should show no change in the meter. If they do we have one of two problems one the motor was already bad or you are useing your fingers to hold the probes to the winding leads. Here I have determined that the one from the left(that used to be connected to the blue wire) is the other end of the wire that is bent toward the outside of the motor housing.
So I connect the opposite end to the blue wire. I cut one of the insulating socks in half and threaded that on before I made the solder connection.
Here you can see the completed and recovered connection of one end of the capacitor winding made to the blue wire and tucked back down against the rest of the motor windings. I have similarly tied the remaining loose ends together. the green wire is an extension of the wire from the left as it was to short on its own. the piece of green wire is just something I had laying on the bench.
everything back in place with a couple of wire ties to replace the ones I cut and discarded. the loose ands of the cord are glued to the windings with a few drops of super glue and a coating of liquid electrical tape to finish it all off.
Watch this spot one of the through bolts has to get between the wires and the housing. make sure that the opening where the armature goes is clear (no wire tie ends hanging out in the way etc)
reassemble in reverse order of dis assembly. put a couple drops of super glue on the shaft just before reinstalling the plastic fan. Test run the motor before installing the belt.