Summer Winch - WHHSFTC/1718RobotDesign GitHub Wiki

The team spent a good deal of May and June speculating about what challenges could be a part of relic recovery, and one thing they were fairly sure would come up was hanging. The began by looking at designs from previous years (primarily RES-Q) and came up with a few noteworthy designs. The first involved a tape measure being driven by a wheel. Both the tape measure and the wheel were chained to motors, and the friction between the metal tape measure and wheel holds the bot up while it is hanging.

The other idea the team had was to use a lift (such as linear slides) to hook on to whatever the bot was supposed to hang to, and then to pull the robot up with a worm gear, which improves torque massively while sacrificing speed. However hanging is most likely an end game scoring opportunity, and we decided that the worm gear would take too long to raise our bot in the 30-second end game period.

The final idea we had was to use only slides. The linear slides would extend up and hook whatever the bot would hang on to, and then we drive the slides in reverse to pull the robot up.

After a few days of discussion, we settled on initially trying the tape measure design. We had two ideas about how to go about implementing this. The first was based off a video we saw from i2r robotics.

Advantages of this design were that it was compact, and that the torque from the two motors drives both the tape measure as well as the drum. However, we did not have the double chain that was required on hand when we initially prototyped this design, which led to the two designs below.

On the left is a very simple design in which the tape measure is powered by one motor and the drum (or roll) is powered by another motor. The other design has two motors chained together and to the roll, which is then seperately chained to two gears in order to ensure that the tape measure and the drum turn opposite directions in order to actually extend the tape measure. We decided that for our first attempt we would build the first design, because it was significantly simpler and we had concerns about the space required for the second design.

An Adobe Illustrator Sketch of the Front of the mechanism

We decided to use Andymark NeverRest 60:1 Motors geared 3:2 (16 tooth on motor to 24 tooth on drum/tape measure) to maximize the torque we would get, since speed was not as much of a concern. We initially planned on gearing it 4:2 but we were worried that the larger gear was too large and that it would run into the other gear on the drum.

A CAD of the design

Dimensions of the outside wall (in the first CAD it is that wall that is removed to see the mechanism)

Dimensions of the inside wall (the wall that is visible in the first CAD)

Dimensions of the bottom panel and the top panel, the only holes are the ones we use to mount the motors)

One final picture, showing the spacing of the inside of the mechanism