Driving a carriage up and down a cylindrical object isn’t the most popular activity but that is certainly no reason not to build such a device. Check out [Ryan's] creation that does just that, he calls it a Tubular Drive.
There isn’t much going on here, basically there are 4 wheels that grip a pipe. Two of those wheels have integrated gears and are driven by a DC motor. The remaining two wheels are idlers. When power is applied to the motor, two of the wheels spin, which then moves the entire assembly down the pole. A quick reversal in polarity brings the unit back the other way.
With those 3D printed plastic wheels you may think that traction would be an issue but [Ryan] insists that it is not a problem. The ABS wheels were treated with an acetone bath to smooth out the print layers and the distance between the wheels can be adjusted using a couple of bolts. Together that allows enough surface contact and pressure to ensure slip-free traveling.
Although the wheels were made to grip 1/2″ electrical conduit, it would be very easy to adapt this design to fit around and climb up all sorts of cylindrical objects, maybe even rope! Perhaps v-wheels with a spring tensioner system would allow for traveling on different size tubes while also adjusting for any variation in the diameter of a single tube.
[Ryan] says version two will have a linear encoder and be driven by a stepper motor. Check out the video after the break…