While I’m not mentoring a team, I’m designing and plan to build a robot to play this year’s game for local workshops this fall, aimed at inspiring low-mid resource teams. That is, I don’t have as strict a budget as Everybot for parts, but I want this to be something that can be built from COTS parts with a rather basic set of tools - I’m looking to minimize cost of tools + parts, and shooting to keep it under $3k in addition to the KoP*. Anyways, I’m looking at having one of the 2022 COTS climbers on the robot (Likely Thrifty’s, but that probably doesn’t matter for my question.).
I definitely plan to use both software and hardware limit switches (magnetic reed, most likely) to keep from hitting the hard stops in a hard way, but I’m also big on having mechanical soft stops, because sometimes software and electrical solutions don’t actually solve things. Here are my current soft mechanical stop solutions - do you have something as good or better? [OBTW, I am looking at a single stage, but please feel free to post multi-stage solutions because someone else may find it useful, even if I don’t!]
Lower end (that is, arm retracted): Bolts and pool noodle. I plan to have an extra inch or two of the outer tube (2" square) devoted to this. The idea is to wedge an inch or two of pool noodle up the tube, past some holes for cross bolts similar to the Thrifty Climber’s top end hard stops, then put in those bolts. The pool noodle will catch the base block of the mobile arm.
Upper end (that is, arm extended): strain relief segment on the Dyneema rope inside the upper tube. I haven’t worked out the specific knots yet, but the idea is that a relatively short length of bungee will be linked to a relatively long length of Dyneema. The difference will be small enough that the bungee isn’t in danger of breaking, but that the bungee will serve as a soft stop, at least for a dry fire of the arm. This solution should also be applicable to a multi-stage arm.
* Let’s face it - if it weren’t for vendors stepping up, a low resource team could never have built that passive climber hook. My former mid-resource team couldn’t have done it.
Added 7hr later: After a bit of sleep, I realized I was sweating this too much. I’m going to climb with an AM Redline on a 48:1 gearbox, and a 0.787" spool (AM hex spacer stock). Even assuming free speed and no gearing losses, that’s going to be about 1.4ft/s or .42m/s. I’m not worried about that speed at all in cases where the robot weight isn’t a factor, and only a hook of less than 2lb or 1kg is involved.
In the case of lifting, a mass moving upward at 1.4ft/s and suddenly sent ballistic will “jump” about an inch. Easily solved with hook design (not using a COTS hook, but some 1/4" aluminum bar).
I the case of lowering, I’m still planning a bit of pool noodle, but probably less than an inch.
I’d still like to hear how teams are addressing (or ignoring) this issue.