The heart of the motor is its armature, and this the part that’s involved in the game called “rewinding”. Several makes of rewound armatures are available commercially; you can buy them rewound and epoxied, and even balanced and ready to insert into your chassis.

To do it yourself, study the following instructions. First, here are a few basic facts that may help:
1. Decreasing the number of turns of wire on the armature (dewinding) will decrease torque but increase rpm.
2. Increasing the number of turns will decrease rpm and increase torque. This means you will have less “top end” and more acceleration, a very desirable characteristic on most tracks.
3. Only very long, super-fast tracks require motors with very high rpm where torque is not necessarily desirable. On this type of track, the cars seldom slow down to hairpin-negotiating speed, so the torque is not needed for acceleration as badly as it would on a track with many slow curves and only a few long straights.
4. The most desirable motor has a happy blend of torque and rpm, which makes it tough to best on a great variety of tracks. If you race on one track and one track only, you should wind especially for this particular track’s characters- tics. If it’s a long, fast screamer, wind for top-end speed, not torque. If it’s slow and twisty, wind for torque, rather than for “top end”.

The rewinds, themselves, perform beautifully on a reasonably fast track. They accelerate just like a stock car, but have much higher top speed. Long straights are “home sweet home” to these motors. On a large, fast track, they cannot ba caught. Low-speed performance is good and braking doesn’t suffer at all.

Remove the body from the car you intend to rewind and lay it aside. Pry the copper spring clip off the chassis so that you can remove the gear plate. With a screwdriver carefully pry off the armature pinion gear, and remove the armature from the gear plate.

After identifying the commutator and the commutator tabs, pry back slightly on one of the tabs with a small screwdriver, and free the commutator, by sliding it from underneath the other two tabs. Now break away every one of those little wires from the commutator, and put it aside for later. Ten, cut the wires off each of the three poles of the armature with an Xacto knife, and remove them.

Now, all you add is the new wire Use good magnet wire made for HO motors and in a size suitable for your particular track or type of racing.

Among the many possible winds, two are especially suitable for the major types of racing — road and drag or flat-out racing. Use 17 feet of No. 38 wire (each pole) for road racing and 11 feet of No. 36 wire (each pole) for drag and flat-out racing. The only difference between the two is that the No. 36 wind is a little faster and gets a lot hotter than the No. 38 wind. If you use the No. 36 wind, be sure to ventilate the chassis and reduce friction to a minimum.

Measure off one length of wire for the wind you intend to user Stretch this out across the floor and tie a pencil to the loose end to keep the wire from coiling back up. The pencil will drag across the floor as you use up the wire. Cut the wire to proper length and tape the freshly cut end to a rotating part of the winding machine. If you are winding by hand, simply hold the end of the wire in the same hand as you hold the armature, leaving the other hand free for winding.

Now, starting at the innermost part of the pole, start wrapping on the wire clockwise (looking at the pole end-on). Do this by turning the crank of the machine and gliding on the wire from one side, or by simply wrapping the wire on by hand.

Lay the wire on evenly, working from the innermost part of the pole to the outermost and back again. Continue in this manner until about two inches of wire remain. This is the “finish” end of the wind and, along with the two inches you left at the “start” end, will be used to connect the armature to the commutator. Move the next pole into position and, with a new length of wire, repeat the winding process, winding in the same direction.

A word of caution! There is a shiny metal lump located in the center of the underside of the armature. During winding, be certain that you do not allow the wire to pile too high on top of this lump or the commutator will not fit on the armature properly.

When all the poles are wound, remove the armature from the machine. Bend all wire ends up (commutator side of the motor being “down”), making sure you can tell which are “start” ends and which are “finish” ends. Use very fine sandpaper to remove the insulation from the wire. Take care not to pull too hard on the wires, especially the “start” ends, since if you break one of these, you may have to rewind the pole again in order to connect it.

Reinstall the commutator on the armature and, if necessary, press the tabs against it to hold it in place.Take the “finish” end of each pole winding and wrap it twice around the solder lug directly to the left of its pole, as you see it looking end-on at the pole with the commutator side of the motor down. Wrap the remaining wire around the armature shaft. This serves the double purpose of holding the wire tightly around the lug for soldering aid of getting the ends out of your way. Similarly, take the “start” end of each winding and wrap it around the solder lugtothe right of its pole, then wrap the surplus wire around the armature shaft.

Use a soldering tool and electronic quality, rosin core solder to fasten all connections. After the solder cools, file off the excess taking care not to cut the wires. Otherwise, protruding solder may rub against the bottom of the motor casing, causing a loss of power and, possibly, overheating. Unwind the excess wire from around the Vmature shaft and cut off each piece at the solder lugs.

The armature is now finished. I do not recommend coating the wires with epoxy, as they are safe without it and the epoxy will trap heat. However, it would be a good idea to balance the armature if you can rig up the necessary equipment. If you measured the wire very carefully and wound it on evenly, the armature should be reasonably well balanced as it is.

You may now put the armature back on the gaar plate assembly and replace the armature pinion gear. It might be wise to install a new armature pinion gear, since the old one may start turning free on its shaft and cause a power loss.

There are some disadvantages to rewinding which we’ll discuss here. First, if you use either of the winds described in this chapter, you will need to use a low-ohmage controller with them. As mentioned before, heat may become a problem with the No. 36-wire wind. Excessive heat means that something may be shorting-out or rubbing. To help keep the motor cool, cut away part of its casing. Be sure however, that you do not cut the portions which hold the magnets away from the armature.

A rewound motor draws more current (amps) than a regular motor; this places an abnormal load on the pickups and commutator brushes. This makes the use of silver-plated pickups and HI-SlIver or Hi-Copper brushes quite desirable.

Rewinding the motor is just the beginning of what you can do. Silicone tires, stronger magnets. and lower gear ratio can all improve the performance of the car Normal tuning methods, too, are still helpful.

Balancing - Making a Poising Tool