Extremely inspired by the Howdy Bots’ Shrinky Dink, we’ve been playing with a bistable carbon rollable boat hook climber. My team doesn’t quite have the bandwith to commit to doing an OA thread, but want to share our work with the community.
It’s bolted to a printed drum and has held up in our testing thus far! Today we loaded it to ~60 lbs with the current reduction at a 20A current limit for end of match stuff.
We haven’t automated any of it yet. That was just running it off of a PWM generator and the REV Hardware Client (after our knot on the crate holding the batteries slipped). I wish we had better video of the loaded performance.
We ran these to climb in FTC back when they were military grade antennae mast product and not the new cheaper boat hook product.
Part of the problem with using an encoder to determine the tip position of the mechanism is that axle position doesnt perfectly translate. Your axle can be at the same position but the spool can be at slightly different diameters when unspooling (respooling is actually pretty consistent).
Magnetic tape and hall effect sensor is a pretty optimized control solution when the same axle position on the encoder could result in ±1" height depending on spooling diameter.
We’ve been testing and tweaking various aspects of our prototype (model screenshot in the first post). We are moving on from HTD timing belt, discussed briefly here in 4481’s wonderful OA thread. We stopped the belt from slipping (bonus shop dog in the background) on the small pulley by adding a crude tensioner, but felt more comfortable throwing #35 at it, and calling it a day.
The new model uses #35 chain on 18x36 sprockets in addition to a yet undetermined MP reduction. We’ve added a WCP ratchet and pawl to allow us to shoot for an aggressive climbing speed without worry about backdriving post match.
The pawl is actuated by torsion springs and a bike brake cable. We’ve been playing with a NEO550 based system to actuate it.
So far we’ve only drilled some holes to attach a hook. There wasn’t anything remotely tricky about it. We will likely cut a few inches off of the end when we meet tomorrow (our first holes are a little misaligned - mentor user error). I’m planning on cutting it with our band saw and don’t anticipate any difficulty. The fibers are well contained in the resin system; I’m not worried about dust.
We are bolting an aluminum hook to the end of the tube. The current plan is shown below, (carbon tube not shown). The green parts are printed spacers to sandwich the aluminum hook inside the carbon tube.
