Many people want their BPROs (battery powered ride ons) to go faster, have more torque or accept more voltage. In most of the BPROs, a 500, 600 or 700 series, brushed, electric motor is used. This series is also found in a lot of Radio Controlled cars, trucks, planes and boats. Being that it is fairly common, there are a lot of different companies out there that make them. Some of the older or bigger units use a 700 series motor. There are aftermarket offerings in both of the above sizes.
Here are some things that you should know before you start replacing the factory motor with an aftermarket one. These tips should help you to avoid making a purchase of something that will fail in only a few hours or days.
- a stock Tamiya 500 series motor (non-rebuildable)
- stock Tamiya 540.jpg (8.23 KiB) Viewed 59533 times
- an aftermarket Tamiya 500 series motor (rebuildable)
- Tamiya 25t.jpg (25.12 KiB) Viewed 59533 times
-Armature-The shaft that runs through the motor and contains the windings, the commutator and the core. It has a bearing or bushing on each end to keep it in line.
-Brushes- The primary contact point for the current to make it into the motor. The brushes are connected on one end to either the positive or negative input wire and on the other end they contact the commutator. Brushes are not replaceable on sealed motors but are replaceable on most aftermarket ones.
-Commutator- The part of the armature shaft that allows for current to pass through the brushes and into the windings.
-End Bell- The end cap for an electric motor that holds a bushing or bearing and on stock BPRO motors, holds the power input tabs. On an aftermarket motor, the end bell also holds the brushes and the springs. In a factory motor, these are sealed with metal tabs holding it on. On most aftermarket motors, these have screws holding them on.
-Timing- Has a significant impact on R/C car performance. Timing can be found with rebuildable and non-rebuildable motors. Most all aftermarket motors have some timing added from the factory to make it perform better. This is why some offer a “Reverse” rotation motor so that the timing will be even between the two motors while they are running in opposite directions. More timing means more speed but less torque. Less timing means less speed but more torque.
-Turns- Refers to the number of times a wire, usually copper, is wound around each pole of an armature. For example a 27 turn motor. The higher this number is, the lower the RPMs but with higher the torque and longer the battery life. The lower the number (like a 10 Turn motor), the higher the RPMs but with lower torque and less battery life.
-Winds- Refers to the number of wires wrapped around each pole of the armature making the above mentioned turn. This is usually the second part of a motors spec like 27 turn Single, Double, Triple or Quad. A single motor wound motor make more torque in the lower RPM range whereas a Double, Triple or Quad wound motor makes more torque in the top of its RPM range.
Now the Meat and Potatoes portion
-Factory BPRO motors are sealed units that are not rebuildable and shouldn't be taken apart. The metal tabs that are holding the end bell in place will likely break if you remove them. The brushes inside will also come out of their holders and are very difficult if not impossible to get back together.
-Aftermarket motors are not always sealed units. Most of the ones built for the R/C world are rebuildable so that the brushes or springs can be replaced. This also allows for the cleaning of the commutator, as it gets dirty over time.
-Aftermarket motors are designed for R/C applications. There are some exceptions in the robot market but most of the motors are designed to move a 3-6lb vehicle. Through gearing, they will power our BPROs just fine as long as we follow some rules. A BPRO stock 550 or 600 series motor is between 32 and 35 turns depending on who you ask. If that’s the motor that the factory decided would last the best, how long do you think a 10 turn motor will stay together? Not very long. A motor that is 21 turns or numerically higher will last longer. The R/C motors are also designed to operate within a range of 6-16 volts. That’s where it pays to get the FULL motor specs before you buy one. If it’s designed to make 31000 rpms at 8.4 volts, it probably will not last long at 18 volts. If it’s designed to operate at 18 volts but only makes 5000 rpms at 18 volts, why would you want it? Do your homework and ask the manufacture for a spec sheet.
-Aftermarket motors sometimes have factory built in “timing”. If you buy 2 motors and they are sealed units but they have 3 degrees of advanced timing, you shouldn’t run them as a pair. Make sure that the motors you buy either have zero timing when using them as pairs or buy them as a standard and reverse rotation package. Again, it pays to get a spec sheet from the manufacturer.
-Aftermarket and stock motors are designed to operate within a specific RPM, Voltage and load range. Overvolting is a common practice among the MPW clan. When a stock motor is overvolted, it puts out more RPMs than at its stock setting. The bonus is that this is the quickest way to make a BPRO faster. The downside is that overvolting creates heat and resistance that translates into eventual motor failure. The windings on the armature are usually covered with an epoxy resin. When the motor gets super heated, it causes this resin to melt in the motor casing and makes the “magic smoke” appear out of the motor compartment. There are ways to slow this down and speed this up.
Slow failure down-
Under gear the vehicle by going to a numerically higher gear ratio. This will add torque but will not add much speed.
Increase the wire size being used throughout the BPRO. This will lower the resistance in the wiring and translate into less heat at the motor.
Add heat sinks and/or fans to the motors. This will help the little fan in the motor to cool the motor canister off. Cooling the motor will keep the epoxy from melting and ruining the motor.
Speed failure up-
Over gear the vehicle by going to a numerically lower gear ratio. This will add more speed but will decrease torque. Decreasing torque will cause the motor to work harder and generate heat faster.
Use smaller wiring at any junction in the BPRO. This will increase resistance which translates to more motor heat and we already know what that does.
Overload the BPRO. I know we all want to ride them too but when we place a 250 pound person on the Dora Quad and joy ride in the cul de sac, we are asking for failure. This works like over gearing but worse. Now we are increasing the load on the motor usually till it stalls. When it stalls, the brushes burn a spot on the commutator and create a place that the power can no longer transfer through. This will also increase the heat so fast that they are destined to fail.
I hope this helps someone and keeps them from spending alot of money in the wrong direction.
