Chris_COLORADO

I'm posting here because I believe this is where the experts are who can answer my question.

I need help!

Has anyone had any experience installing an RC unit on a Power Wheels Jeep toy???

My kids (2 and 4) love their jeep, but it is backbreaking for me to have to scoot alongside to steer for them (and impossible for my wife who’s had spine surgery).

The Jeep runs of 12V, but I can easily regulate down to six volts (or any voltage) for the controls, etc.

What I need to know is what size servo would work best to control steering and is there a smart way to control speed (forward and reverse)

My brother is into RC planes, but nothing this size nor any electric powered stuff so he’s not familiar with speed controllers (I think). He said this forum would have the answers!

Anyway, can anyone come up with recommendations?

I have a “EXPERT 4-CHANNEL RM RADIO CONTROL SYSTEM”, a Receiver, four small servos, and nicads/charger for both transmitter and receiver. The whole system works and tests out well on.

Based upon talking to my brother, and a quick reading on the internet, my thoughts are:

1. Use one channel to control steering (Right joystick, left and right)
2. Use one channel to control speed (Left joystick, up and down)

There are two motors in the power wheels, and based upon the 14G wire feeding them, I “anticipate” a max load of 20 amps at 12 volts nominal.

I’ve seen electric speed controllers and think that a 70 amp controller would easily work (with space to spare) http://www.hobby-lobby.com/jetibrushless.htm

Question: Is there any speed controllers that can reverse polarity? Or do I need to use a different channel driving a servo which flips a DPDT switch to reverse polarity? I’m not sure if I even need reverse but I’d like to have it just in case. How do you guys do this?

My big QUESTION is what size servo(s?) to use for steering?

Also, what would be a smart way to “disengage” the RC unit (ideally remotely) such that the kids can drive the jeep without damaging anything but so I can override? How can the servos be put in the "free wheel" mode----is there such a mode or possibility?

Looking forward to your help!

Thanks in Advance

Chris

Item in Question
http://www.fisher-price.com/us/power...=&pg=1&id=9949
Parts Diagram
http://www.mendingshed.net/powerwhee...rams/75840.pdf

Hircflyer

Having run along side my grandson's ......I know what you are saying........I just don't believe any of our airplane or car servos are strong enough to turn the steering on any of those ride along cars.

Maybe a commerical application has bigger servos but I can't think of any......good luck. Might try Servo City.

Erich_F

Hello,

I think that if you used a pair of Hitec 5735 digital servos, one for each side, you may be able to control steering. These servos have over 300 ozs of torque at 6V, and decent speed in doing so.

You need to do some more research on your drive power system. I'm an electric forklift technician, servicing all kinds of electric powered industrial trucks. Most modern equipment uses MOSFET transistor type speed controls that can handle upwards of 500 amps. In your application, you need a controller that's capable of moving the vehicle, but starting it's movement, and if against an incline, or ramp. In such a situation, even a small electric vehicle as yours, the amps can reach well over 100. Albeit not sustained, it's quite a strain on RC car or airplane type MOSFET speed controls. If you use the 70 amp control as you say, fuse it with a 60 AMP ALS Buss type "barrel" fuse (available from a local electric parts house, Hughes Supply or Greybar Electric are a couple). This will protect your control in the event a stalled or ramp start condition causes over amp.

As for directional control, that can be done with a DPDT switch of suitable amp rating, but won't last very long. Electric vehicles use what's called a contacter to reverse traction motor polarity. It's essentially a heavy duty relay that's built as a DPDT circuit. These suckers can handle up to 600 amps, 300 continuous.

This sounds like a fun project, I look forward to hearing about how it turns out.

Erich

matthewn7

Gws makes a servo with nearly 600 oz inch of torque. Find it at
http://www.gws.com.tw/english/produc...avy%20duty.htm