I'm sorry, I used the wrong word. I meant removable, but the horns sliding through idea is genius.
I agree, but I can't take credit for it. Somebody suggested it at Bot Blast when I brought up the issues with horns, and I can't believe nobody's done it before.
You noted in your Bot Blast recap that the screws had started to pull out of the frame. Would you recommend a different way of connecting armor to UHMW/HDPE frame rails? (Something like Fingertech's nutstrips, maybe?)
Yep, the screws had pulled out about 1/16" and the wedge was loose. It might have been the screws loosening, but I'm worried about the threads in the plastic failing after a few more vertical spinners. Nutstrips might work better, with screws going all the way through the UHMW, but I'd still be worried about those holes stretching if they're close to the edge. A block of metal between the wedge and the nutstrip would push them back and solve that problem, but the only real advantage of UHMW is that it is thick enough to put screws in directly. I would either move to a larger screw size and make some backup rails, or use nutstrip and a thinner, stronger armor.
For Sisu, I've been looking around at what other people make their ants out of, and the bent aluminum method seems interesting. Brushless outrunners are lighter than the 280s that come on the 1000rpm motors, and also shorter so that I can make the chassis narrower. Along with switching to a 1mm titanium wedge, this thing is now down to 0.82lbs, and it's only missing the nutstrip. With the extra weight, I would increase the wedge to 0.0625", but I haven't found a good supplier yet as Fingertech only goes up to 1mm. I could also change the 1/16" UHMW wheelguards to 0.5mm Ti. The center of gravity is also a little too far back. I can't move the motors back any more because of the wheelguard. Without wheelguards this robot would be laid out a lot better. Would sticking the wheelguards out past the back of the bot make them more vulnerable?
With motors this big in an ant, I'm anticipating this thing being hard to control, and so I'm going to try to make my own gyro/mixer that can be used upside down, using a multicopter flight controller like Lucas Grell suggested. The OpenPilot Atom happens to have exactly the hardware I need: a microcontroller, RC inputs and outputs, a gyroscope and an accelerometer. It has open source software, and for 4g and $25, seems pretty awesome. We'll have to see how much of their software I can reuse.
For Mad Props, NERC has emailed me back confirming that I won't get any weight bonus, but Bot Blast has not. For NERC I'm definitely going to put bearings on the bottom to make it roll smoother, and hinged wedgelets on the front. I couldn't figure out a way for it to self right when it's stuck on its face, except running one prop backwards to fall on its side, which I doubt there will be enough thrust to do, so I'm designing in a self righting arm on a servo. I think this will let me get rid of the large, heavy, and fragile self righting hoops, at the expense of slower self righting.
And I finally got to do a bit of work on Whirl and Hurl. The motor mount is mostly done, and the top and bottom plates are cut and still need to be rounded out some more. It's a ridiculous amount of aluminum. Drilling through the motor mount took 4 hours on my 1/4hp drill press and the brand new bit is now totally dull. For the wheel issue, I'm thinking of putting steel washers on either side of the wheel to help protect it, or Gene brought up using an RC car wheel with foam tread and a plastic hub.
