Drive: Lynxmotion Sumo wheels driven by COPAL 50:1 6V gearmotors
Battery: Thunderpower 11.1V 750 mah lithium polymer pack
Drive ESC: Dimension Engineering Sabertooth 2X5 R/C
Receiver: 2.4 Ghz Spektrum BR6000
Weapon: Ti. spinning bar friction driven by Turnigy 1650Kv Brushless Outrunner
Weapon ESC: TURNIGY 18amp Brushless Speed Controller
Frame: Custom milled .25" polycarbonate with Hexcel Texalium carbon fiber
Build Report (most recent updates near top of page)
Phalanx made it through the March 7th Central Illinois Bot Brawl in mostly one peice but sadly was unable to destroy all who stood in his way. The final match tally for the event was 2-2. To hear the whole story, be sure to check out the event report.
Tomorrow is the 2009 Central Illinois Bot Brawl. The last Bot Brawl I was able to attend was back in 2005. I wanted to bring Phalanx back even better than before so I made a few modifications. There wasn't enough time for a complete overhaul nor did I have access to the necessary tools. Instead I focused on addressing the problems encountered at Phalanx's last event and upgraded most of the electronics with newer and more powerful components.
The single biggest problem I ran into with the first version of Phalanx was the weapon motor drawing too much current causing the lithium batteries to fail in a rather dramatic fashion. After the event I looked into upgrading to higher discharge batteries but it would also help to swap out the speed 280 weapon motor. Ideally a different motor could be used to provide the same power or more but without drawing as much current. The most obvious solution was brushless technology but this option was too expensive at the time. The technology has since become much cheaper and I was able to find a good sized motor and matching 18 amp ESC for less than $50 combined. Based upon conversations in the Delphi RFL forum, I decided to go with TURNIGY 1650Kv brushless outrunner motor. This motor was described as a cheaper alternative to the popular Axi line of motors. I installed this motor using the included aluminum mount. I also added a new friction drive wheel which is mounted to the motor shaft using a prop adapter.
The other upgrades I made included a new set of drive wheels, a new drive ESC, new drive motor mounts, and new aluminum standoffs for the front weapon shaft mount. Because my trusty Barello 100 drive ESC was being used in my line-following robot Xenops, I needed a new drive ESC for Phalanx and tried out a Sabertooth 2X5 R/C. This ESC is packed with featured such as built in mixing, BEC, flip control, lipo cut-off, and more. To save weight and to provide a stronger mounting design, I installed a pair of Lynxmotion sumo tires with matching aluminum hubs.
The new Phalanx is much more solid and robust than the previous version. Several weak points have been strengthened and the final weight is still less than 16 ounces. There are still a few areas of the design that worry me but they'll need to be addressed after the event when I have time to do a complete rebuild. For now, enjoy the picture of Phalanx 2.0 and check back for an update on his performance at the March 7th Central Illinois Bot Brawl!
Phalanx and I just got back from Peoria, IL where we competed in the Central Illinois Robotics Club's Bot Brawl event. Visit the full event report to see how Phalanx did.
Sorry for the lack of updates but the wait was well worth. Phalanx is now, for the most part, finally complete. The one main task that still remained was making the weapon blade which can be seen in the picture below. The blade features two destructive "knockers", a rather intricate design focused on aesthetics as well as pragmatics, and is machined from hearty 6Al4V Ti. Thanks to Brian Schwartz of Python Engineering for the excellent machine work. After continuously analyzing the friction drive reduction, I decided to stay with a very demanding ratio of about 2:1. I figure that in order to make a lower reduction work, I would need to move the friction surface out further but as the weight on the blade moves out, the inertia of the blade becomes higher and thus harder to turn anyway. Instead I decided to opt for a simple spring which forces the blade against the friction wheel with a constant but rather weak pressure. Hopefully this will save the weapon motor and ESC from a flaming death.
One main concern I had with Phalanx, specifically because of the slow spin up time, was the lack of speed. The COPAL 50:1's gear motors simply didn't offer enough ground speed. Thankfully the lovable "Buckybill" came to my rescue with an informative guide on swapping the 12V motors with 6V versions from the 30/60:1 gear motors. After a rather disappointing start trashing one gearbox and almost another, I finally got to see how much of a speed increase this would result in and WOW was I amazed. It must now be about 4X's as fast as before! Whoo Hoo! With the weapon and drive sorted out my only other plans for Phalanx include a possible weapon ESC upgrade to the C-20 and most likely wheel armor (probably heat-bent .0625 polycarbonate). Otherwise it's just constant debugging until the next competition. I'd love to get Phalanx super reliable for a less stressful competition unlike my last (read about my adventure at CIRC Nov.8 2003 with tOBOR). Check back later for more updates.
Current weight as shown - 15.6 oz.
I plan to lower the blade much further then this
As you can see Phalanx is not without the mandatory RMP Sticker
Last weekend I gave Phalanx to my friend Brian to show off at a robotics day event at his college (MSOE). He also brought his beetle Chimera and his unfinished super heavyweight full-body spinner White Rabbit and drove them around and sliced up some soda cans. Maybe he converted more followers to our sport. Before leaving my baby with him, I finished up some last minute details to make sure Phalanx was presentable. The switch and power LED were mounted, the top carbon fiber armor was attached, and the insides were cleaned up. Everything was operational and working good until the battery died. No problem, just charge it up.
Ok, problem now. It wont charge! Not sure which was malfunctioning, the battery or the charger, I ran out to the local hobby store where they told me the pack was fine. Seeing as the bot needed to be functional tomorrow, there was no time to get another charger online and the store's selection was not very good. Luckily after I left, Brian managed to build a Li-poly charger from scratch and the problem was solved. Although I wasn't around to see how it performed, he said that the pack ran out sooner then he thought it would so I guess I'll need to look into that. Luckily he said it only got slightly hot and just during the very demanding times so I think we'll be alright there. Since today was my birthday and one of my presents was a season pass to Six Flags Great America which is near Brian's house, I took a trip up North to ride some coasters and pick up the bot on the way. The bot is basically complete then except for the real Ti. blade which will be CNC'd later. I guess it's onto the debugging phase of the build in which I'll try to work out all the kinks. Below is an updated pic of Phalanx's current state.
Current weight as shown - 14.2 oz.
4/25/04This weekend my custom carbon fiber sheets and friction drive parts came thus I got right to work installing them. The carbon fiber sheets fit perfectly with no cutting required so all that was needed was to drill the holes for the screws. The friction drive required some slight rethinking as I decided to use a bracket to hold the motor in place rather than just wedging it into its mount. This means I can simply unscrew the bracket to remove the entire friction drive for easier repair. I could not keep myself from spinning up the prototype blade to test it out and was very impressed with the speed. Unfortunately after a few seconds on full power, the weapon motor ESC and wires got very hot with the leads melted a little. I am not too concerned however as the bot is still missing the bearing for the weapon blade and a spring of some sort to provide the force pushing the blade on the wheel rather than my current method of simply making a tight fit then locking it in place with a shaft collar. Once these are installed the setup should prevent the weapon motor from stalling and hopefully avoid burning up the electronics.
Current weight as shown above - 13.6 oz. (Note. Pictured blade is only polycarbonate prototype)
I finished the weapon mount this weekend. I eventually came to the decision that these will be made from polycarbonate after all as polycarbonate will accomplish the task just fine and save a bunch of weight. I installed the nylon hex standoffs and the structure is now very rigid. A little adjustment is still required to straighten the blade so as to avoid scrapping the ground during rotation but the added room allows me to simply slide the blade higher if neccesary. I can't wait to get the speed 280 motor and spin this puppy up! Also, while checking the RMP for prices on carbon fiber I found that for a certain fee per square inch, custom size sheets can be purchased. Seeing as Phalanx's carbon fiber base and top will be square in shape, by simply ordering two 3.5" X 5.5" sheets, these parts will be done with no work required. Problem solved and my life is made much easier. For now check out the shot below of Phalanx's current state.
Current weight as shown above - 6.2 oz. (Note. Pictured blade is only polycarbonate prototype)
Current weight as shown above - 3.7 oz.