Atom Bomb

[nyditch]

I decided I may as well just make a thread for Atom Bomb. It's been around a few years and has changed drastically over that time. Peterwaller was curious if here in the US we use any similar parts to you guys, so I figured I'd start off wit ha parts list.

My current version is as seen here, the little drum bot.
http://www.youtube.com/watch?v=HRQ3_bR8Jaw

I'll get a close-up picture of it some time.

It has a 1in (2.54cm) aluminum drum on a 1/4" carbon fiber dead-shaft. The shaft is press-fit into a magnesium bracket, to which I have the all of the electronics taped. The drum has 4x 10-32 steel countersink screws that stick out and spins up to 15,000RPM and weighs about 40g. It's tough to see in the video, but the front is supported by a small titanium foot in the middle of the drum, thus why it hops around when upside down.

For drive, I'm using motors from the website Pololu Robotics. They're 30:1 sanyo-style gearmotors with an extended output shaft. Each one is about 9.6g and stalls at about 660mA (at 11.1v)

The weapon motor is brushless 1750kv that peaks current at 15A and rated to 98 watts. The motor can is press-fit inside one end of the drum, and the stator is pressed onto the 1/4 inch shaft.

For battery, I'm using Turnigy 160mAh 30C in 3s configuration for 11.1v. They're a little weak on current, but they do they job and haven't blown up yet.

The drive ESC is an old Barello board, which aren't being made anymore.
Receiver is AR6110e Spektrum. Brushless ESC is some Hobby King cheapo thing.


Once I got the parts machined (about 10 hours of shop time), it was about 5 hours to get it all assembled the first time. Now I can take it all the way apart and put it back together working in about a half hour.

It has no back armor (or should I say armour) at the moment since I'm pushing the weight limit. I'm also a little over the UK size limit by 1/4 inch, but that can be fixed with some different wheels. US competitions don't enforce size limits very strictly, especially amongst the less popular weight classes here such as US fleaweight ( 150g UK ant weight) and US Beetleweight (3-pound).


One problem I've had with it, is the titanium foot on front is very springy. If I so much as spin up the drum too abruptly, it will flex and the drum hits the floor, sending me tumbling. It's manageable, I just need to be careful.

Previous version:
Polycarb frame
Ammo brushless in-runner mounted in frame with rubber band drive
.75in Al drum (22g)

Previous to that version:
Maxon 13mm 30kRPM w/ rubber band drive to drum.

Previous to that version:
Banebots motor w/ rubber band drive to drum

It's been to about 14 competitions over the past 4 years, all in California.

I'm not sure how often you all compete, and it seems that there are differences in antweight build style between us. I hope to be able to learn some stuff from you guys.

[Andrew_Hibberd]

I have watched the videos its looks like a nice little robot. The parts list seems fairly similar to the UK robots. There haven't been many drum robots competing in the UK as there are in the US, not really sure why that is.

As the 150g robots are less popular in the US do you tend to use the 1lb Antweight arenas as they are bigger? I am curious about the arena rules for the US ants as they have a small drop off arena and very high walls. Do you find this favours the spinners over pushers or any other class?

The UK rules use a 3' square arena with a 50% drop off, and the sides are ~2" walls or full height.

[nyditch]

Mine is the only 150g drum bot I know of actually. It's a decent design, but takes some serious planning and balancing of weight so not to go over.

As for the arena, yeah, the 150g bots compete in the same arena as the 1lb bots. As for the arena, there are no rules other than it has to be safe. The one in the video is 7'x7' outer with 6x4 insert, 2x 12" pushouts, and 8" tall 1/8" polycarb wall. I've also seen a 4x4 insert, a straight 6x6 or 8x8 box with or without corner pit, and the arena that my club at my college has is a 6' hexagon (just enough to fit through a standard doorway). Lemme tell ya, fighting a US flea on a 8'x8' rough steel floor is a little silly. Most arenas work alright though. Pretty much whatever someone builds and decides to hold a competition with is what we use. Each person has their own idea of what an ideal arena would be, so they do vary a lot. The only thing that's pretty standard is that the outer wall is always at least 1/4" polycarb.

A UK arena would be pretty fun I think. I'll have to see if I can build an insert that size. I probably have enough materials for it.

[peterwaller]

I suppose it shouldn't be a suprise that most of your parts are the same as we use over here as we started buying them from the USA before we got distributors over here. The biggest difference is in the arena we have 50% of the arena edge must be straight fall off and even the other 50% is sometimes only about a 2inch wall although my arenas always have two walls up against the polycarb. This helps a little but many of my spinner fights are lost when the robot flies out of the area after hitting the opponent. Even if you have destroyed him you lose because out of the aren is instant loss while damage is counted out after 10 secs of inability to move. A nice big area like you fight in with little or no drop off must be great for spinners. I have never built a complete drum spinner but I did build an early version of Mutant which had two short drums one on each side of the motor.
http://i109.photobucket.com/albums/n66/ ... utant1.gif
It did quite well and I think it is still the only walker to win an AWS.

[teamocean]

That looks like a really nice little drumbot!

I built one last year called Tempest and it worked surprisingly well despite a few flaws in the design. It is currently being rebuilt to make it invertable and have a much more powerful drum.

Heres a couple of vids of the old version in action

Testing the drum: http://www.youtube.com/watch?v=qYWrN-svJX4

Fighting at AWS30: http://www.youtube.com/watch?v=qXfPbC1lQlo

I really like drum spinners, just a shame that there aren't more of them around.

[nyditch]

That's a nice drum bot there. Is it an ant? It looks big and heavy (comparatively). Seems like you had it working pretty well. What design problems did you run into?

And yeah, with that much pushout area, if you send yourself flying out you're done for. The only way you would win is if you threw your opponent out as well. I wonder if one spinner bot causes both to fly out, that the spinner one is the winner because it was in control - just like a clamp bot would pull an opponent out.

I think a neat arena design would be with the 2" wall around two opposite corners, kinda like this.
_______.............
|..........................
|..........................
|..........................
...........................|
...........................|
............ _______|

That way you have two places to still corner somebody and it leaves two corners completely open.

Also, I'm on a short break from building a new ant to figure out weight issues, but I have a walker in the making. Here we get 200% weight for walking (300g for ants), do you have the same or similar?

Here's my 1lb (US-ant) version of my walking robot.
http://www.youtube.com/watch?v=gxmJXRlsksY
It uses gyroscopic precession to move when I make the blade tilt.

I think the 150g (300g) version will be a bit big for UK rules though. The blade itself (1-tooth steel bar) swings 4". The blade weighs in at about 80g and I'll have a good 15A motor on it at 11.1V.

Oh, and as for the small pushout, I find that it still gives the wedges a good chance to win. A wedge wins about every other competition with a small pushout, if not more. For the 150g bots though, it's tough to give good statistics since there are so few of them; I'm going more off the 1-pounders. A skilled wedge driver with a halfway decent bot has a good chance to win by pushout still.

[peterwaller]

It was an ant we allow 1.5 x the weight for walkers or shuffle bots in the UK but they still have to fit the cube.
The main problems were it was slow and difficult to turn and the teeth which were 3mm steel wire (piano wire) ground to a trianglar section and glued in kept flying out. here are a couple of shot of slight variations I tried.
http://i109.photobucket.com/albums/n66/ ... 0112-1.jpg
http://i109.photobucket.com/albums/n66/ ... 160136.jpg
I eventually replaced the drum with a vertical disc or two and then to the present version with a horizontal disc.
http://i109.photobucket.com/albums/n66/ ... CF0308.jpg
http://i109.photobucket.com/albums/n66/ ... CF0608.jpg
http://i109.photobucket.com/albums/n66/ ... MG0651.jpg

[terminaldamage]

I really like drum spinners

I wholeheartedly agree

[nyditch]

Ah hah, there's a rule difference here. Shuffle bots strictly do not get any weight bonus. Here's the exact rules excerpt:

"Non-wheeled: non-wheeled robots have no rolling elements in contact with the floor and no continuous rolling or cam operated motion in contact with the floor, either directly or via a linkage. Motion is ?continuous? if continuous operation of the drive motor(s) produces continuous motion of the robot. Linear-actuated legs and novel non-wheeled drive systems may qualify for this bonus. [Contact this event with questions on weight bonuses to see if your robot may qualify.]"

And if you want further reading, this is the full set of rules we use. They're written for all weight classes.
http://botleague.net/doc/RFLTechRegs-2010-final.pdf

[peterwaller]

We had many so discussion as to how to distinguish shuffle from walkers that we compromised giving only a 50% advantage to any non rolling robot.
Actually under the rules shown below the older versions qualified as a walker as it never rested on part of the body but the later ones do.
Walker - A robot whose final drive output rotates through less than 180 degrees (e.g. legs)
Shufflebot - A robot that rests on part of its body during the recovery phase of its leg movement.
All work on a double crankshaft principle.