|Red Rover, Ant Weight Combat Robot:|
Ok, only a few weeks and a lot to do before Seattle Bot Battles 2008, complex weapons and creative artsy crap out the window for a bit,.. this is war,.. and its time to put a plan into action that can be accomplished within a short time frame.
Red Rover is a fairly simple design in principle, 4 wheel drive, low profile wedge, with a lifter poker, grabber arm. but this bot has multiple design elements worked into a seemingly simple concept to deal with all forms of spinners, and packs quite a bit into 1 lb using a large range of specialty parts and materials to get the job done.
Basic stats (assumed at this time)
H, W, D,:
~1.5", 7", ~9"
(4/26/08) A lot to do and only a little time. Quite a bit of testing pre dates this starting point, I did a lot of work comparing Tamiya crank axel gear boxes to Bane bot 16mm gear boxes, and even though through heavy modification (hand made carbon fiber axels, metal gears, Atomic tuned motor, and Aluminum Screws) I was able to bring the weight of the Tamiya box down to match the Bane Bots ~1.15oz. In addition the Tamiya gear boxes where faster at 6V, but the Bane bots motors where almost as fast and had a bit more torque behind them. Secondly it came down to stall current, the bane bots stall out at 2A max, the Atomic tuned motors which are much better then the stock motors where nice but they stalled out well past 5 amps and tended to let out smoke when left stalled for longer then a second. If that was not enough finally it came down to space, I was not able to position the innards how I wanted to with the Tamiya gear motors so the Bane bots won out.
Continuing with drive train I decided the aluminum hubs that I purchased with the bane bots wasted a lot of weight so I set to work shaving off about .1 oz from each by cutting into the thick back stock of the hub. Notice the burnt wood, these hubs are anodized so cutting through them takes quite a bit of effort, they sure got hot when I dug into them with the band saw. If need be ill cut even more off. From the get go, I am shaving every 1/10 of an ounce I can as my design packs a lot into very little weight, I know ill need it down the line when I am deciding how thick the armor can be.
I have decided to keep things really low to the ground So I figured I would use either 1-1/2" or 1-3/4" D, 1/2 thick foam hobby wheels. I mounted them to the modified hubs with the provided hardware replacing the metal washer with a plastic one and some loc-tight, I also added a single brass #0 wood screw through the hub and into the wheel to keep the tier from loosening during competition I may add a second one if needed.. all-together it feels as if they will have a lot of grip. I have ordered a set of the slightly larger tiers for testing who knows ill likely make the wheel holes wide enough to fit either tier size..
I spent some time deciding on materials to use for the vertical supports. I played around a bit with UHMW, but I wound up deciding on kitchen cutting board plastic for its ability to flex a bit and take damage without structural loss, and 2 sided Honeycomb Fiberglass for its excellent strength to weight ratio I also decided to use aluminum standoffs through the two materials to hold everything in place.
I wanted everything to be as low to the ground as possible so I set a goal of fitting everything in a package only 1/8 taller than the Banebot Gear motors that would fit inside (16mm). I started out making my side walls ~13/16ths tall, and factored in 2 - 1/32nd thick plates to make up the top and the bottom,.. this made the robots total height without wheels ~ 7/8ths of an inch tall. At this point I also decided to go with the 1-1/2 tall wheels I then factored in ~ 1/16" for button head hardware and this gave the robot ~ 1/4th" clearance on either side. A little more than I wanted, but smaller wheels would make the robot slower so I decided this was acceptable as I did not want to lose any speed.