I was BattleBots team leader on the GT RoboJackets for the academic year 2013-2014. While many photos were taken and documentation put together, unfortunately very little of that has made it on to the team website, www.robojackets.org. I include some of my experiences, thought process, and photos here for anyone interested.
I would like to thank the team for a great season. This is everyone who attended the competition:
Turner's cube, made by the new members of the team as a machining exercise (somewhat cheating since they used CNC mill instead of actually turning it, but still)
The team entered four robots to the 2014 Motorama competition, held in Harrisburg PA. They were: Cathi (30 lb ring spinner), Mini (3 lb drum spinner), HS (3 lb horizontal bar spinner), Lexi (3 lb full body spinner).
Cathi, Mini, HS, and Lexi
Unfortunately Lexi was not built in time for competition. HS experienced a problem with its bar coming off, suggesting imporvements to how the weapon is attached. Mini had a problem with traction and the drive motor controller, but otherwise performed OK until a critical hit took apart the frame. From this, the frame should be designed and held together in a more secure way, and motion system designed with center of gravity in mind for good traction. Cathi did OK in the first competition but broke the drive belts for the weapon, requiring a replacement with a tougher belt that got jammed in the weapon drive pulley and stalled the weapon motor, causing the ESC to set on fire - fortunately the rest of the robot kept functioning successfully even if a bit burnt. One of the wheel drive motors on Cathi also looked crispy, leading to a recommendation for beefier motors and better belts for next competition.
I was mostly involved with the design of Cathi. The ring spinner design allows the robot to be invertible and use its weapon as a full-body shield, thus saving armor weight and allowing a full third of the robot weight to be in the weapon. This is good in terms of moment of inertia and stored energy per unit mass in the weapon, but it should be kept in mind that the weapon has to be a ring meaning it may not be as mechanically rigid as a smaller weapon of the same mass.
While I was messing around with beam calculations and making stuff like this, there was still a bunch of machining to be done for the robots. This work is the main contributing factor to me choosing a much less machining-intensive design next year (or so I thought...).
Cathi --------------- Top Plate 15.3" diameter, 1/8" thick, Al 6061 Waterjet profile with holes Countersink holes (manual drill) Bottom Plate 15.3" diameter, 3/16" thick, Al 6061 Waterjet profile with holes Countersink holes (manual drill) Weapon Aluminum Top Weights (x8) 6"x1"x1" Al 6061 Waterjet (taper?) profile with holes Mill (chevalier/CNC) speed holes Mill (chevalier/CNC) top extrusions Countersink (chevalier/drill press) holes Weapon Aluminum Bottom Weights (x8) 6"x1"x1" Al 6061 Waterjet (taper?) profile with holes Mill (chevalier/CNC) speed holes Mill (chevalier/CNC) top extrusions Tap (CNC/hand) holes Weapon Steel Top Teeth (x4) 6"x2.5"x1" T1 steel Waterjet profile with vertical holes Mill (CNC) speed holes Mill (chevalier/CNC) top extrusions Countersink (chevalier/drill press/CNC) holes Weapon Steel Bottom Teeth (x4) 6"x2.5"x1" T1 steel Waterjet profile with vertical holes Mill (CNC) speed holes Mill (chevalier/CNC) top extrusions Tap (CNC/hand) holes Weapon Disk 17.5"x17.5"x1" 7075 aluminum Waterjet outside profile and weights from the middle; bolt holes in middle Attach to rotating holder on mill using bolt holes in middle; shave off 0.125" on both sides and add taper; cut out using mill Alternative: attach to big lathe... Weapon Pulley Passive (x4) 2.25" diameter, 1" thick Al 2024 Cut entirely on lathe Weapon Pulley Active (x2) 2.25" diameter, 1" thick Al 2024 Cut entirely on lathe Top/Bottom Pulley Spacers (x6) 2.25" diameter, variable thickness Al 2024 Drill holes first using mill Cut to size on lathe Internal Standoff Blocks (x4) 2"x2"x0.75" Al 6061 Waterjet profile Mill/CNC speed holes Drill bolt holes on mill/CNC mill Tap bolt holes by CNC/hand Top/Bottom Motor Spacers (x2) 1.8"x1.5"xvariable thickness Al 6061 Face-mill sheet to proper thickness Waterjet profile HS ----------------------- Baseplate (ABS Plastic 8"x8"x3/16"): water jet Rim Steel (2'x1'x1/16"): water jet, sheet metal bender Mounts (ABS Plastic .5"x6"x6"): mill Weapon Shaft (?): lathe, drill Weapon bar (2"x9"x1.25"): water jet, mill (to drill central hole) -Will require welding for steel rim Mini ------ Drum pulley -diameter 1.5"x ~1.75" long aluminum -using lathe machine from stock big side first then flip and machine the smaller side. Motor pulley -diameter 0.6" x~1" long aluminum -lathe? The part might be too small and there may not be enough to hold in the lathe. Side panels -1.5"x0.125"x5" aluminum -waterjet? Use water jet to cut pattern in panels and the mating ends as well as the bolt holes. Use mill or hand drill to countersink Side panels -1.5"x0.125"x6.5" aluminum -waterjet? Use water jet to cut pattern in panels and the bolt holes. Use mill or hand drill to countersink Bottom panel -4.7"x5" aluminum -bandsaw cut from stock Top panel -6.5"x2" aluminum -bandsaw cut from stock Non-pulley side support -2.2"x2.864"x0.25" aluminum -use mill. Hold bottom of stock then cut the outside pattern. Then flip and hold the outside shape and cut out the bearing holder and cut down to thickness. Then cut bolt holes Pulley-side support -2.2"x2.864"x0.5" aluminum -use mill. Hold bottom of stock then cut outside shape. Then flip and cut down to thickness and cut out hole for bearing. 2 smaller Steel Teeth -0.25"x0.25"x1" steel -use chop saw to cut to length. Use mill to cut holes and counter sink (mill or by hand) Big steel teeth -0.25"x0.25"x2" steel - use chop saw to cut to length. Use mill to cut holes and counter sink (mill or by hand) Drum -inner diameter 1.5", outer diameter 2", 5" long aluminum tube -lathe for cutting to length? Use mill and hold by putting flat ends of the drum against the vice and drill the holes. Use mill to flatten out places for the teeth? Frame supports -0.125"x0.125"x1.5" aluminum -cut to length using chop saw. Use mill to cut holes Drive motor supports -1.125"x0.749" uhmw plastic -use mill to cut shape Drum spacer -uhmw platic -use waterjet? to cut out of scrap piece on our shelf
Lots of time at the waterjet
Aluminum ring machined
Close up of CNCd aluminum attachment
Close up of CNCd aluminum ring
More detail photos
Adding steel teeth
Putting together the body and adding electronics
We drove to Harrisburg PA from Atlanta GA, which took just about 12 hours on the way there. On the way back, Ryan wanted to visit the New River Gorge Bridge, so we did!
Stuck in Atlanta, then taking a break at IHOP
Still taking a break at IHOP
Team photo after IHOP
Rising moon on the way to PA
PA capitol building in Harrisburg, and the long-awaited bridge at New River Gorge
These battlebots robots were made over the two years I was with RoboJackets before becoming the team leader.
Mandii (Mandi 2), competed 2013
Sindi, Aidan's design (or is it Nadia?), and Cami, Michael's design, both competed 2013
Mandi 1, competed 2012, and Soafi, its predecessor