Alas, I’m using 130 motors and the 180s are too long. Those nerf motors are a shout though, those are some ludicrous stall current numbers for a brushed motor that size. Apparently a colleague is into his nerf modding, so I’m off on the scrounge before I buy anything…
I bought some of the Out of Darts Valkyrie motors and they arrived yesterday. Straight swap for the aliexpress ones and I feel like they should perform great, except when starting out they pull more current than my little Allegro A4950E 3.5A drivers can supply and trip the internal over-current protection.
I’m going to throw my hat in the ring for the pub beetle event in May, if I get a spot I guess it’s rev2 PCB time and I’m spinning my own motor drivers. I also think the aliexpress motors might behave more acceptably at 4s (or more), but I need to do some testing as that means more current draw while switching the intended 530mAh battery for something with less capacity.
As it stands, here’s how it performs with the aliexpress motors running on 3s: https://www.youtube.com/watch?v=Y6qvmATpInE
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Turns out I’m fighting on the 25th, so basically all my time spent not at work or asleep has been robot related. Current status:
(infodump below)
Drive is mostly done. The gearboxes took a lot of fettling to get gear mesh just right (and repeatable) and the parts easy to fabricate. I switched to 6V motors and the bot now scoots about happily at a speed that’s actually fun to drive. They don’t get too warm so I don’t think they’re going to explode but I’ve put connectors on the wires anyway, because if I make it easy to service they’re guaranteed to survive, while if I hard wire them that’s just asking for a failure.
The weapon assembly needs more machining work, it’s getting a couple of bulkheads to sandwich the worm gear onto the motor shaft and handle the forces of lifting, and also to keep it from shooting into the battery pack with just the right impact to the lifter. I’m making the parts from brass because I have broken so many drills already this project I can’t even
The weapon motor tucked in there is some aliexpress weirdness (the listing literally says “we don’t know anything else, please don’t ask us about it” but I managed to find the datasheet), it’s an in-runner brushless motor that happens to fit on a gearbox from a 16mm gear motor with a little persuasion. It also has a hall effect sensor, so I can get arm position in my software for free with no extra parts. Napkin maths and trusting the datasheet say I get roughly 40kg/cm of usable torque (60ish stall) at the arm pivot while taking about half a second to rotate 90 degrees to vertical (not at the same time).
I’m slowly running out of internal space, and that was kind of the plan all along. Any space not filled with Stuff gets chunks of foam and (if possible) some low-infill TPU inserts.
Also, weight check: As pictured, 945g.
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I love this. It’s a great combination of a minimalist design in some ways (right angles, symmetry) mixed in with some outrageous over-engineering (welded unibody and custom PCBs). The build quality is lush, great to see that welded body, and glad it’s come out fun to drive.
(On the subject of over-engineering, I kinda feel like this whole hobby is by definition over-engineering since none of us get paid for this or achieve anything other than our own satisfaction. I do boring “proper” engineering as a day job, building robots is where I do stupid unnecessary engineering just for the hell of it.)