# Help Creating Remote Controlled Brushless Motor Cable Cam System

Hi,

I am trying to build a RC controlled Cable Cam System. Basically just need to figure out the correct brushless motor size to move 15-25 pounds back and fourth on a cable with a top speed of around 25-35mph and be controlled by remote. I think the basic coding for it isn't difficult as I only need to tell the motor to go forward or backwards but I also would like to be able to tell it where the two end points are on the cable and I have no clue how to do that. The cable will change length depending on where I set it up so my best understanding is that the end points would be an equation involving the size of the pulley and how many rotations there are between each point.. but thats really just a guess ha

any help would be greatly appreciated!

The simplest way to move an object between two points with a DC motor is to use limit switches to tell the motor when to decelerate and stop. Object trips switch -> send motor a stop command.

To get a specific speed, you need to do the math: pulley diameter * pi/(motor rpms * 60) will give you the speed you want.

Now, to actually get to that speed, you need to take into account the mass of the object, potentially the inertia of the pulley (usually not) and the mass of the cable, the torque of the motor and the amount of time you have available for it to get up to speed.

You can find that math in any introductory Physics book: F= ma; velocity = acceleration * time.

Enjoy. Sounds like a fun project.

You could wrap some white duct tape on the cable a few meters (kind of yards but bigger) away from cable ends and optical switch to sense when your cart gets past it. Or shiny aluminum tape.

Tape marks need to be far enough from the anchors for the cart has time to stop. It needs a way to brake too.

Motor power depends mostly on how high steepest incline of the rope would be. If the 10kg cart runs at 15m/s up a 30 degrees slope it needs 750 watts only to overcome gravity. Add friction and electric losses and you’ll need a > 1000watt motor.

With less incline and a very taught rope you could cut that in half or less…

What kind of motor/drive - search “bicycle Kepler friction drive” - that’s a small RC outrunner motor pressed against the bicycle wheel, in your case you probably can press it against the cable directly

RC motor controllers also have braking function.

Thank you guys so much for your help!