DIY Network

Electrically Powered RC Cars: Speed Controller Upgrade From "Radio Control Hobbies" episode RCH-204

This Ultima ST by Kyosho (TM ) gets a power upgrade via an electronic speed controller and a hot new engine.

In this segment, Chris Chianelli performs a speed-controller upgrade on an electrically powered RC truck -- the Kyosho Ultima ST. The first modification will be the replacement of the stock speed controller with an electronic speed controller.

Important: This demonstration provides some of the basic information for assembly, upgrade and operation of this particular model truck or kit. There are variations in assembly for each particular model. Read and carefully follow the manufacturer's instructions that come with yours, whether it is this particular model or another. Additional information about assembly as well as running, troubleshooting and fine-tuning the model can be found in the manufacturer's instructions.

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	Figure A
	Figure B
	Figure C
	Figure D
	Figure E
	Figure F
	Figure G
	Figure H
	Figure I
	Figure J
	Figure K

Speed Controller Upgrade

The speed controller regulates the amount of current sent to the motor. Using an electronic controller eliminates the need for several pieces of equipment used in conjunction with the stock mechanical controller -- including wiring, servos and a resistor -- resulting in lighter and cleaner system. The controller upgrade will enhance performance in a number of ways including faster top-end speeds, longer run-times and better throttle response.

The tools you'll need (figure A) for this upgrade include Phillips screwdrivers, a 1.5 mm Allan driver, hobby knife, needle-nosed pliers with side-cutters and double-sided tape.

Our speed controller itself (figure B) came with double-sided tape supplied, as well as a small, plastic screwdriver for adjusting the parameters on the controller.

You'll also need high-quality rosin-core solder (figure C) specifically designed for electronic use and a good soldering iron.

Removing the Stock Speed-Controller

• Begin parts removal by unplugging the wires connected to the stock speed controller (figure D). You may use your fingers to do this, or needle-nosed pliers.

• Unscrew and remove the controller's mounting screws using a Phillips screwdriver (figure E). Since the motor is being replaced later, it was also necessary to remove the low-resistance plugs that attach the stock controller to the stock motor.

• Next, unscrew and remove the screws that hold the servo and control linkage in place, and remove the control linkage. The servo itself (figure F) can be removed after the resistor plate is removed.

• Unscrew the plate that holds the resistor in place (figure G), then remove the resistor and servo.

• Disconnect the electric switch that was connected to the mechanical speed controller (figure H) since the new, electronic controller not need this switch. In fact, the new electronic unit will come with its own switch to turn the vehicle on and off.

Installing the New Speed-Controller and Battery

• Use double-sided tape to mount the new speed controller to the chassis (figure I), following the manufacturer's instructions.

• With the new controller installed, connect the controller's plug into the receiver as shown (figure J).

• Mount the battery in the bottom of the chassis (figure K). The battery will later be connected to the speed controller using the pre-mounted plugs.

In the segment that follows, Chris installs a high-performance motor in the Ultima and shows how to solder the connections.

Kyosho Ultima ST

Length . . . 16.4 inches
Width . . . 12.5 inches
Engine . . . Electric
Assembly . . . Ready to run
Street Price . . . $125

Chris Chianelli's Mailbag

Q: Steve, a DIY viewer from Boulder, CO writes: Chris, I just bought a hot modified motor and put it in my Traxxis Rustler. After two runs, I've burned out the speed controller.

A: It's critical that high-performance be matched with suitable speed controllers that can handle them. Check with your hobby dealer on properly matching the replacement motor with the right controller. Here's another tip: It's also advisable for beginners to start out with less powerful upgrade-motors at first to build their driving skills gradually. Too much speed too fast -- and not enough driving practice -- may just put you into the woods!