Phoenix - 30 lb Combat Robot

I've been involved in robot combat (BattleBots) for the past three years now. My first robot Shish-Kabot was extremely successful with one 2nd place and two 3rd place finishes but it had one weakness. Every time it fought a flipper robot called Upheaval, it would get tossed around and lose via knockout. (see 2nd image) After spending way too much time thinking about how to beat Upheaval with Shish-Kabot I decided to build a better flipper bot...

Step 1: Background

I guess I should probably explain a few things about what I'm talking about.

Robot Combat is an sport often referred to as BattleBots, but that term is trademarked so I'm probably not supposed to say it. But the basic idea is two robots fight to the death in an enclosed bullet proof glass box for 3 minutes or until one can't move anymore, when a knockout is declared. There are basically three groups all robots can be categorized into. Spinners are probably the most prevalent. They have some spinning mass (think exposed lawnmower blade) and try to slice or blunt force the other robot into submission. Pushy bots are the simplest to build. They often have a wedge to get under the opponent. They win by dominating the flow of the fight. The third group is flippers or lifters. They are designed to get under the other robot and flip them over or chuck them across the arena and hope something breaks on impact. This is often done using pneumatic rams. Flippers are not very common anymore because the introduction of cheap imported Chinese brushless motors and the difficulties associated with pneumatics.



The design goals/constraints for Phoenix were

1. Powerful flipper weapon

2. Entertaining

3. Cost must be under $700 (I'm a high school student without a high paying job)

4. Must be under 30lb weight limit

Comments

[mildlyimpolite]

Do you have a link for the ram that you used?

[AlexHrn]

no because i bought it used and have no idea where it was originally purchased from. it is a nfpa large footprint hydraulic ram like http://www.peninsularcylinders.com/lh.htm

the one i use on phoenix is 2 1/2" bore 4" stroke

[kelvinwolf]

Pretty cool did you win?

[AlexHrn]

Phoenix hasn't fought since February 2012 but it took 3rd at Motorama that year.

[oldmechanic]

I've got an idea for an upgrade for you! You said it weighs 28 lbs, and the limit is 30lbs. Why not put in another gaz canister to increase the number of flips?

And I have one last question. Is the robot you mentioned(Nyx) called near chaos? And is it traversable?

[AlexHrn]

"Why not put in another gaz canister to increase the number of flips?"

Phoenix doesn't have enough room inside it to put in a tank of a usable size. I also ended up using the weight to make some modifications to increase the durability of the frame and keep it from getting stuck on its side. I'll probably add a bit of info to this instructable about the modifications.


"Is the robot you mentioned(Nyx) called near chaos? And is it traversable?"

The other robot mentioned at the end of this instructable is called "Nyx" it was created by the team Near Chaos Robotics.

[oldmechanic]

Cheers!

[oldmechanic]

This is epic. why not create a youtube channel for it. By the way, can you maybye put in pictures of your last battlebots on?

[AlexHrn]

I have a youtube channel. http://www.youtube.com/user/Teamcooknwithgas

You can find all of Phoenix's fights on youtube by searching for "Phoenix" "Motorama" "Nerc"

Also you can read about my other bots on my blog which is linked somewhere near the top of the page.

[oldmechanic]

Thanks! I really mean, thanks! even though i live in the uk, i can still have access to all the materials you used!

[tomtortoise]

Hey, im working on a tank drive robot (non combat) and have the whole thing built but my only problem is that the wheels are horribly attached to the motors which happen to be the same exact motors your using, I was just wondering if you could go into a little more detain on how you attached your wheels, thanks.

Also quick tip, Amazon carries almost every type of structural metal, all the aluminum I got for my robot was less then half the price at Home Depot, you also get free shipping on almost all of it.

[AlexHrn]

Thanks for the info about Amazon.

I use Kitbots.com's drillmotor hubs and colson wheels.The wheels press fit onto the hubs which screw right onto the output shaft of the drill gearbox.

[RoboTable]

How much PSI are you using?

[AlexHrn]

I run unregulated CO2 in Phoenix. Since CO2's pressure is dependent on temperature it runs anywhere from 600-900 psi but it is typically around 850.

[RoboTable]

Do you know of a good rule of thumb to figure out how much PSI you need for any given weight class?

[AlexHrn]

No, not at all. The big thing about flippers that is often ignored or not given enough thought to is arm geometry (Phoenix's arm isn't very efficient at transferring the 2700lbs of force to a flip) and flips about the same height as Upheaval which uses much less force but uses it more efficiently. Upheaval runs at around 180psi with the same sized ram and gets a higher flip.

[RoboTable]

I already understood that different configurations used different amounts of PSI. But now that I know that even a 30 pound robot can use only 200 PSI to have good flipping power I then think 300 PSI could be plenty for a beetle weight robot (3 pounds for those who don't know).

[AlexHrn]

I'm not following...
Force= Pressure * ((1/2 Bore)^2 x Pi)

a 1" bore ram generates ~78.5 lbs of force at 100 psi
a 2" bore ram generates ~ 78.5 lbs of force at 25 psi.

You can run whatever pressure you want if your ram is large enough to achieve the force necessary to launch the other robot.

There aren't any pneumatic bots below 12lbs. The available necessary components are too heavy to make it work.

_____________________________________________________________

"I then think 300 PSI could be plenty for a beetle weight robot"

Were did that totally arbitrary number come from? Most pneumatic components are rated for 200(ish) psi maximum.

[RoboTable]

I understand that there are not many robots with pneumatic robots under twelve pounds. I said 300 PSI because I'm making a 'homebrew' pneumatic with PVC piping rated for 400 PSI. Thanks for claryifing about the bore ram.

[AlexHrn]

OK... but assuming you are using an pneumatic cylinder like these, not a hydraulic ram for the your actuator, it can still only see 200-250psi and you'll need a regulator to drop your 400psi down to a usable pressure. _______________________________________________________________ Do not mess with pneumatics unless you know what you are doing and or have prior experience working with them or have help/input from someone who does know what they are doing. (and just because you've read this does not make you an expert)

Do not exceed manufacturer recommended pressure ratings on pneumatic components. 

Always be careful when testing pneumatics and take proper safety precautions such as testing with the robot behind a lexan shield and everything in the robot secured.

[RoboTable]

Thanks

[megaduty]

That's a great flipper!

[crandolp]

I've been working on a flipper myself and the only part I havent been able to track down is the paintball tank cap to NPT fitting. Got any suggestions?

[AlexHrn]

Take the flow restrictor off the bottle the bottle. It should have a 9/16" NPT thread.

Now if you do that keep in mind you won't have anything to hold back the Co2 so you will have to add a ball valve or something to regulate the flow.