I’ve been trying to figure out how teams retract their telescoping climbers that are extended through constant force springs. I thought it was with the standard continuous elevator rigging where it’s rigged to each stage but if I am wrong please let me know how your team, or a team you know, did it.
Based on my understanding, you could just connect a cable to the output stage and a drum. When you unspool the drum the springs extend the telescope and when you spool the drum the end retracts as it’s connected via the cable.
We had a single length of rope attached to the very top stage. The rope runs through the middle of the telescoping tubes and is just tied off to the bottom of the very top stage. We are using 1/4" Dyneema rope which is significantly overkill for the purpose.
At the base of the arm, we use a 5/16" bolt as a turning “Pulley” such that the rope feeds out the side of the base of the arm. We then have a drum winch mounted next to the arm.
Retracting the arm is simply a matter winding the rope around the winch. Extending the arm is simply a matter of paying out the rope from the winch. The constant force springs take care of the extension.
You don’t need much force to extend the arm, so we selected constant force springs with fairly low force: 5 lbs for the first stage, 2.5 lbs for the second stage and 1.5 lbs for the 3rd stage (the first and second stages use 2 springs, the 3rd stage uses a single spring). So the maximum force that the winch needs to overcome when climbing is 10 lbs (if we climb all the way to the point where we are compressing the first stage into the base). By using progressively weaker springs, we can keep the extension “orderly” which we used to our advantage to allow us to mount our “Pat Sajak” (WoF Spinner) on the first stage of one of the two arms.
Okay cool thanks!
It won’t look as cool, but it’s also entirely valid to run the cable external. You don’t see it as often, but it can make implementation and maintenance easier (at the risk of entanglement depending on location).