RC Truck and Construction - My first Tonka dump truck

Quote:

Originally Posted by 69tony12 (Post 60955)

thanks alot (again) i will do that on the front as i dont have much space, its taking ages as the bruder wasnt built to allow steering so i had to cut the whole front of the van lol, will post a build soon (when i can find enough time) as i just got myself a BIG toy, a 42" 3D TV hehe, lol

i will also have to ask you, how did you do the lift setup as i cant see much and i really cant understand it, i know you use a servo (is it 360 modded??) and then 2 wires to higher it and lower it, could you explain it please, thanks a lot mate, your great at this ence why i ask you so much lol

The dump mechanism is cable operated and yes, a servo is converted to continuous rotation and used as a "winch" to pull the bed up. I double back the cable (like a block and tackle) so that the it lefts half as fast as the servo turns which doubles your power. Each truck is a little different depending on the best place to mount the lift servo.

The easiest (mechanical) way is to mount the lift servo in the rear of the truck. Cable goes from servo to bottom of the lift bar (bar that rises to raise bed) and then back to the frame. As you winch the servo you pull the bottom of the lift bar and that raises the bed.

Here is a video looking from the bottom of the truck. As you watch the video you will see the cable traveling faster than the bed is lifting which is why it has so much power to lift. like a nice gear reduction but, using cables.

http://www.youtube.com/watch?v=5uAiwaQ8ekY

Also the mounting point on the servo where the cable wraps around is very small, (manufacture torque rating) about half the distance from center that the servo is rated at, so, whatever ounces of torque the servo is rated at you can double that because it has twice the leverage and then you can double it again when you double back the cable and then you can double it again if you give the lifting bar a mechanical advantage as it rises...allowing a little 28oz torque micro servo to lift a full load of stone.

http://www.youtube.com/watch?v=QwHEMHqjicg

Hopefully the first video will help visualize how the lift works.