Omega Force 2.0
Updated Sept. 3rd 2008
- 12# class for DragonCon Robot Battles
- Invertable chassis and weapon
- All wheel drive using sprockets and roller chain
- Powerful electric rotary flipper with flywheel energy storage
New Rotary Flipper Weapon.
A small brushless DC motor (Mega ACn 16/7/6) turning at 37,000 RPM is geared down 77:1 to the flipper arm which spins at 480 RPM. Number 25 roller chain couples the gearbox to the rotor. The rotor tip speed is 16.7 feet per second. A flywheel also geared to the motor spins at 27,750 rpm storing 60 Joules. Most of the energy used to flip the opponent comes from the flywheel. The flipper arm is made of spring steel and will deflect about 2 inches with 200 pounds of force. All the shock from the impact is stored in this spring and released a few milliseconds later to increase the launch speed.
|Prototype wood chassis with weapon mounted. Wood will be replaced with metal later.|
|Omega Force rotary flipper test
Video by Dale Heatherington
July 8, 2006
(Wait a few seconds for it to load then click the play button)
July 20, 2006
Aluminum frame complete. This is made from 1/4 inch thick 6061-T6 aluminum and required may hours of CAD design and CNC programming. This thing is rigid! It weights 21 oz.
|July 23, 2006. Aluminum Side panels complete.|
July 23, 2006
One drive train assembly. Rear wheel is 3 inches in diameter and the front wheels are 1.5 inches. To get the same linear ground speed on both I used an 18 tooth sprocket on the rear and a 9 tooth sprocket on the front. The front wheels rotate twice as fast as the rear. Note that Colson doesn't make 1.5 inch wheels so I filed down 1 5/8 wheels in a lathe.
The custom gearbox is 20.8 to 1 from the motor to the output sprocket. The chain and sprocket drive gives another 2:1 reduction on the rear 3 inch wheel running it at approximately 800 RPM. The 1.5 inch front wheels turn twice as fast at 1600 rpm.
|July 24, 2006. Now it's starting to look like a bot!|
July 25 2006.
All Omega Force parts are weighed and total more than 12.5 pounds. Since the limit is 12.0 pounds I have to remove some weight. Lets start with the weapon. It weighs a bit over 4 pounds. The rotor alone weighs 16.2 ounces. There's a lot of metal that can be removed without affecting performance.
|July 26th, 1.8 oz removed||Sprocket after weight reduction surgery.
5.8 to 3.6 oz
Center of gravity is unchanged :)
|Original Rotor at 16.2 oz||Rotor after weight reduction surgery. 12.4 oz|
July 27th. Next I'll perform surgery on the aluminum weapon frame. Each side weighs 10.4 oz. I'd like to remove about 3 oz from each. Here's a short video of bot parts being machined (7 meg Flash)
|July 27th. Original weapon frame at 10.4 oz||Weapon frame after the CNC mill had its way.
It's now 7.0 oz
|July 28, 2006. All the wood is gone!|
|July 28, 2006. Rear view. It's still overweight and I need some guards to keep debris out of the chain drive. Those NiMH cells have to be replaced with LiPolys.|
|3300 mAh, 14.4 volts = 28 oz||3200 mAh, 16 volt LiPoly pack = 10.5 oz.
Wow! Changing battery technologies saves 17.5 oz! Now the bot is about 1/3 pound under the weight limit. This battery came from Robot Marketplace
This is the electronic speed control for the brushless weapon motor. I added the relay to reverse 2 motor leads so the weapon can reverse if the bot gets flipped over. It seems to have very good overload protection. Unfortunatly it shuts down for several seconds after flipping the opponent . I need to understand why that's happening and fix it. Maybe I need a bigger flywheel.
Update Aug 13: I ordered another ESC from Century Helicopter Products and did some more tests. The Century Electron 25 ESC doesn't shutdown when the weapon hits the opponent. I tried it 4 times. This is great! Problem solved! Well, no, not really. The ESC went up in smoke the first time the weapon stalled when it tried to hit the opponent while against a wall! Looks like I'll need to get creative now. First I'll order at higher power version ESC from Century and attempt to devise some method to monitor the current and cut back the PWM in response to an overload.
Aug 3: Software mods. The custom controller was removed from Invertabot and needed a few software changes for the use in Omega Force. The flipper control code had to be deleted and replaced with PWM controller code to run the brushless ESC. I also added some code to make a beep every 8 seconds when the bot is turned ON but idle. I hope this will remind me to turn it off before draining the $150 LiPoly battery pack. Once they get drained below 3 volts per cell you have to throw them out! While I was in the mood I did the same for Thrasher. Since I did not want to add any more parts or weight I used the motors as speakers to make the beep sounds. It was easy, I just alternated forward/reverse at 1/4 power at 1800 HZ for 1/2 second. They make a nice "BEEP" evey 8 seconds.
Aug 5. Chassis wiring is finally finished.
Saturday, Aug 5: Smoke test. After I completed the chassis wiring I turned on the power to my custom speed control and tried to drive the bot. The bot spun counter clockwise and ran over my foot just before an op-amp on the controller board burst into flame. Arrrrg! This is not good. An autopsy was conducted and the cause of death was a tiny 4-40 nut stuck in the leads of a power MOSFET. Op-amps do not like 16 volts at 50 amps routed to their inputs. They explode. After replacing 2 shorted MOSFETS, drivers and the op-amp the controller works again. :)
Video by Dale Heatherington
Aug 6, 2006
(Wait a few seconds for it to load then click the play button)
Aug. 16 2006
Good News! Pictured on the right is a 55 amp brushless ESC from Century Helicopter Products. It's now running the weapon motor and works great. No shutdowns, or smoke! There should not be any problems since the motor is rated at 18 amps and actually only pulls 7 while spinning up and pulls only 3 amps after it gets the flywheel up to speed. Massive overrating seems to be the way to go. I think this one is a winner.
These glamour shots were taken on August 16th. Omega Force is at last battle ready and 5 ounces under the weight limit. I could put the wedges back on and still be under weight but testing indicated they offer only a slight performance increase at the expense of certain problems when hitting the opponent in the wheel.
Here's a closeup of the weapon gearbox that shows the nylon protective cap on the motor and the flywheel. The flywheel size was increased and it was moved outside the gearbox. It now stores a little over 100 Joules.
Rear view. There's a cutout for the power toggle switch and a window for the status LEDs.
|New Smart Wedge demo
Video by Dale Heatherington
Aug 26, 2006
(click the play button)
Dragon*Con Robot Battles 2006
On Monday Sept. 4th we took OmegaForce to DragonCon Robot Battles for the ultimate test. There were a total of 8 entries in the 12# class including a new and improved version of Probulator by Evil Robots Inc and TestBot 4.0 by Charles Guan. It was clear from the first round against TestBot 4.0 that I should have practiced driving more. But fortunately Test Bot had serious reliability problems and was easily defeated (unlike previous years). Next we fought Dagger and defeated him easily. Next was the match I was looking forward to. OmegaForce vs Probulator! This is the bot that defeated me last year and I thought OmegaForce should do very well against the basic box with 4 wheels (yeah well, it does have a pneumatic probe too). Things went well at first with probulator taking several good hits from the OmegaForce rotor. But, there were rubber snakes scattered all over the stage. One got stuck in the left chain drive and burned out the speed controller. Arrrg! Snakes in the chain. I didn't see that one coming. With only the ability to rotate left in place, OmegaForce was at a major disadvantage and eventually got knocked off the stage by the persistant probing of my worthy opponent. But even with a snake in the works OmegaForce flipped Probulator several more times!
I was able to only partly repair the controller board. OmegaForce did poorly in all other matches due to the right drive not having reverse or brakes. We did not win the 12# one-on-one but, with some persistance and a bit of luck we took home the 12# Battle Royale plaque!
The rotary weapon and smart wedges worked flawlessly. Omega Force needs only few minor changes to keep snakes and other vermin out of the chain drive. I'm looking forward to Robot Battles 2007.
Here's my Highlights Video of Robot Battles 2006.
I put 75 still photos on Shutterfly. You can view as a slide show or order prints. Click Here.
Visit my Dragon*Con Robot Battles 2006 web page for a full report and photos.
August 23, 2007 ... one year later...
I've been servicing OmegaForce for the 2007 Robot Battles event. I fixed a slippage problem with a left front wheel and added snake guards. However, the bot ran rather poorly. It seems the expensive LiPoly battery pack had lost about 30% of its capacity and the internal resistance had gone up to about .13 ohms. A couple of charge/discharge cycles didn't help. #@*! LiPolys!! So I ordered some A123 cells and a Hyperion EOS1210i charger from MaxAmps.com. They have 1/3 less capacity than the LiPoly pack but can be charged 4 times faster. In theory, they could take a full charge in 15 minutes. OmegaForce required five A123 cells to equal the voltage of the old LiPoly pack. This change added 2 ounces. I hope I'm not overweight now.
The new cells perked up the bot quite a lot. According the manufacturer, A123 Systems, they should last a long time and stand up to a lot of abuse. Also they don't explode or catch fire. I like 'em already. So does the Killacycle team. They use 990 cells to power a drag bike.
Five new 2300MaH A123 cells installed
On Sept. 3rd OmegaForce 2.0 returned to Robot Battles to kick some butt. And we did! Also had lots of fun doing it. The bot moved up through the elimination brackets effortlessly. It was not pushed off the stage a single time! Now that's a first for me.
The first victim was Robot Chicken. The first hit knocked Chicken about 4 feet across the stage to the delight of the crowd. Eventually Chicken drove himself off. During the second round Chicken was tossed about 5 feet and went off in front of the stage. Spectacular!
Next up was Guiding Light, a bot said to be constructed from parts from a stolen church chandelier. He got flipped off once and sort of fell off once.
Most entertaining was a bot named "Nicole Richie". It was so named because it was supposed to weigh 12 pounds but when finished only tipped the scale at 7 skinny little pounds. Actually I heard it's the reincarnation of a bot named "storm" which put a bunch of holes in Invertabot back in 2003. The wheels were made from wire brushes. Nicole got lots of "air time" due to the light weight design. In fact, I think she may have spent most of the rounds in the air. I had to fight Nicole twice because of the double elimination format. The second time Nicole had a 20 inch spike on one end designed to push OmegaForce without getting into rotary flipper range. It almost worked once. I just backed up and turned away to disengage. The final round ended with Nicole getting launched almost 6 feet and landing in front of the stage.
A video is worth about a million more words so please press the play button below.
On Sept. 1st OmegaForce 2.0 returned to Robot Battles to kick some more butt. And we did! Repeating last years performance, the bot moved up through the elimination brackets nearly effortlessly. For the second year in a row it was not pushed off the stage a single time! Even the 12# final match was a case of deja vu all over again. We were up against Nicole Richie again and tossed her skinny metal ass off the stage in a spectacular arc. Comic relief was supplied by "Free Cake" which split into several pieces on impact. Enoda Soda provided some entertaining end over end tumbles. The toughest customer was "Flat Line", dustpan wedge that was difficult to jam wedges under due to its near zero ground clearance. There was one near fatal technical glitch in the second round of the final. Omega Force's radio developed range problems and the bot shut down completely a few seconds before Nicole Richie accidentally drove off the stage. As I moved closer the bot came back to life. That needs to be fixed! Check out the video below.
Omega Force at Robot Battles 2008
For my full Robot Battles 2008 report click here.