Brushed motor info and maintenance

[xjnation]

So what are the main parts to a quality brushed motor

1. The axle.

The axle is normally made of hardened stainless steel with a thickness of 3.14 mm. (0,125 inch) with a flat spot at one side for the pinion set screw. Very rarely nowadays we see axles without flat spots.

2. The stack of laminations.

The 3 pole stack is made up out of very thin "slices" of silicone steel, which are pressed together to a length between 21.5 ( minimum regulated size ) and 22.5mm. For protection against damage and rust and prevention of the sharp edges cutting the wire while winding, the stack is often coated.

There are various inside designs used, the most used are the straight or tapered leg (the part the wire is wound around) The difference in these designs is small but can make a difference to the performance of the motor, the more silicone steel material, the more punch/torque.

3. The commutator/collector.

This part is the most important part of the motor together with the brushes. Looking at the collector is easy to discover that it has 3 separated thin segments, which are made of pure copper. These segments are baked on a ceramic insulation material, which is pressed and/or glued on the axle.

4. The wire

The wire is wound around the 3 poles in such a way that it will react in the magnetic field created by the magnets when power is applied to the commutator. If the wire can move it will create 2 things: an unbalance and a possible short circuit in the wires. To protect the wire from moving on the stack the armature will often be dipped in a special corrosion preventing epoxy coating and heat hardened treated for maximum strength. The number of turns around each pole, and the number of strands of wire used generally dictate how the motor will perform. The Ikarus Sport motor has 23 turns of a single wire (referred to as a 23 single or 23 x 1) The Integy Lathe has 55 turns, as most of us know.

5. Holes or putty - Balancing methods

Holes on top or /and epoxy putty on the side of the stack is the method used to balance the armature. This balance is necessary to increase the RPM and to increase the life of ball bearings and bushings.

6. Brushes

The last part is the end-bell, which house the brushes and springs. The end-bell fits over the top of the shaft and has the fixings for the power cables from the speed controller. The current is fed to the motor via a set of carbon brushes, which are held against the commutator by wire springs. Brushes vary in type and hardness and have a profound part to play in the performance of the motor.



Maintenance


Which ever motor you chose its efficiency will decrease as it is used as carbon deposits build up inside the motor and arching damages the copper on the commutator. If you have a rebuildable motor you should remove it from the Eco and dismantle it for cleaning after every 20 packs or so. Some motors are zero timed, some are advanced. It’s worth making a mark in the end-bell and the can so they end up back in the same place after the strip-down. Un-clip the springs and remove the brushes, then undo the two screws securing the end-bell. Remove the end-bell and place to one side. Inside the can there will be a retaining disk, which needs to be rotated so the slots line up with the dimples on the inside of the can before it can be removed. Then remove the armature, checking to see if any small washers are left inside the can.

Now squirt some WD40 (damp start often used on cars) inside the can to release the carbon deposits. This may need repeating several times, with the application of a paper towel to wipe up some of the fluid. The can should then be rinsed in warm water and left in a warm location (airing cupboard is ideal) to dry. Now do the same to the end-bell and the armature, making sure you don’t lose any washers or insulators.

Once dry you can re-assemble the parts, however you should also polish up the commutator by placing 1000 grade wet and dry paper on the com and gently rotate it whilst applying pressure with your thumb and fore-finger. Always rotate in one direction and not back and forth. Now once assembled install a fresh set of brushes and re-align the timing marks, job done!

[JohnRobHolmes]

I would like to add that the physical dimensions and characteristics described are of hobby grade 540/550 size three pole motors. These dimensions have been greatly influenced by ROAR and are considered standard for 1/10th scale rc cars.


Great write up!