We've pretty much spent the weekend on the couch, knocking back Alka Seltzer Cold and Flu, suffering from the "Motorama Plague" or "Motorama Flu", as it's diversely known. Heck, we haven't even unloaded the 'BotMobile yet, but sitting here with not much to do except avoid infecting other people has meant idle hands - hands which decided to do some CAD work! After thinking about our last two failed attempts to build a weaponed 'bot in the thirty pound weight category, and thinking about all the huge weapons that were in the weight class at Motorama last weekend, we've dusted off an old 'bot design we used to have fun with and decided it was due a revision. Hit Back after viewing an image.
In the first version of Intrusive Interloper we had a three-quarter inch thick rear wall, and half-inch think sides and front angle. Given the damage we've seen dished out at the last couple of Motoramas, that may not be sufficient these days. We initially wanted one inch 6061 on all four sides, but didn't have the weight, so we're going with 2.5" tall by 0.75" thick 6061 aluminium on the rear and sides, then a half-inch thick front wall.
Attached to the half-inch thick front wall is some three-eighths thick 6061 aluminium angle. The bolts are threaded into the angle, pass through slots in the front wall so the height is adjustable, and then we'll use grade 8 washers and lock-nuts to secure the wedge. Fingers crossed that's enough to hold it! The inner walls are 2" tall by 0.5" 6061 aluminium.
Here's the drive train: four 18V DeWalt gearmotors to 3" Colson wheels. In the previous version we had our two "Mini-Walts" but those are currently in use in Steel Stiletto, so we'll re-use the DeWalts from the defunct Formidable Fustigator 2.0 and one of our spares. Not shown are the strengthener kits for the DeWalts which will be installed.
Because we want to take this 'bot to NERC's Franklin Institute competition this year, we can't use Lithium Polymer batteries, so instead we have Lithium Iron Phosphate. These batteries have a slightly different cell voltage than LiPo (3.3V/cell instead of 4.7V) so we'll use two 2.1Ah 3S packs in series to give the DeWalts 19.8 volts of power. The 2.1Ah capacity should just be sufficient for a rumble. The two red bricks are hacked TZ85A brushless speed controllers converted to run brushed motors. The white block is the MS1 power switch, and the purple block is a Hobby King HK401B gyro, which we want to try out, and see if it helps our driving.
Here we have the chassis assembled, and the quarter-inch thick top and bottom plates have been installed. The 'bot was designed so the top and bottom plates are simply 12"x12" to make fabrication nice and easy, and depending on weight, they'll either be polycarbonate or UHMW.
Here's a final render of the 'bot with team colours applied. We have the motors and un-hacked speed controllers for this 'bot, and that's about it right now, so we'll be placing an order for some extra parts like wheels, chassis components, and batteries, once we've had a think about other 'bots for the Franklin Institute competition and see whether we need other components for those.
According to the Killerbotics/Tentacle Torque Calculator we ought to have plenty of oomph from those four DeWalts:
And with judiciously applied pocketing to the chassis parts we ought to just squeak in underweight - completely different than version one, which used to run around 23lb fully loaded: