Grabthar - 150g modular combat robot

This is a 150g combat robot (which is the antweight class in the UK and Australia, and the fairyweight class in the USA), designed to be modular with different interchangeable weapon options. I designed it initially for my youngest son who wanted a hammer bot - my working name was Grabthar but he named his Smasher (with which he has had some success at our local competitions). Since then I have made a grabber option (which is a loan bot for our local group under the name Claw-dine) and am working on a lifter module.

All versions of the robot are designed to use N20 gearmotors (I recommend 50:1 / 500rpm ones) for drive, a small slide power switch, and a 3mm power led. ESCs and receivers there are too many options to list, and I recommend discussing with local bot builders if just starting out. The motor mounts should be held in by four M3 bolts and nylon threaded spacers, with the lid attached via four more M3 bolts down into the same spacers.

There are two versions of the chassis - one for ~32mm wheels (such as sold by Pololu) and one for smaller ~24mm wheels - I mostly use 3D printed hubs (included) with silicone "wedding bands" I bought online as tires. The printed hubs should be tapped for short M3 grub screws to hold them secure to the motor shafts.

The hammer and lifter weapons can both use either a 5.6g or 9g servo (I have seen both labelled as either micro or sub micro - the terminology seems confusing!), and I include lids for either option. The servo gear interfaces with the servo via one of the standard plastic two armed servo horns with the arms both cut down short, with a M2 bolt screwed through both. I include a printable hammer head but my son's version has one cut out of 3mm titanium. The lifter arm and spikes are designed to be attached via M3 bolts and nylon spacers.

The grabber weapon uses a 9g servo. One claw interfaces with the servo via a single arm servo horn, and the other attaches to the lid via a short M4 bolt and not. I found strips of adhesive backed rubber improved the effectiveness of the mechanism. The googly eyes are essential to the proper functioning of this weapon module.

This design is somewhat of a work in progress - I would like to refine the lifting weapon design, and create some further weapon options. I am currently very happy with the hammer and grabber options though.

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