UK Kilobots - 1.362kg (3 lbs) Combat Robots

[widow_twanky]

OK, just clarification on some of the rules ideas of this class.

What is the requirement for failsafes?

For antweights the weapons need to failsafe but the drive does not as a running robot doesn't create much of a risk and also servo's do not always go dead centre when they failsafe so will keep creeping. I think we all know what the rules are for feathers.

To me I think that the weapon failsafe would be sufficient for this class having seen the como drills performance, nice and puchy but put your foot in front of it and it aint doing any damage. I think this comes into the 'you can always put your foot on and crush it' category.

I also means I can use the 'compatible' spektrum receivers on these which would seem to make it a lot cheaper to put together a few kilobots considering they are about £30 cheaper that the genuine spektrum receivers.

Andy

[john_frizell]

Any news on how the build of the arena is going? When might we expect to see it, and 3 lb robots, in action?

[ewan]

I've been putting together a little machine over the last couple of months, I'd seen the idea of a 3lb class and reckoned it would be as good a weight as any to restart on, there's many nice components designed for hobbyists and 'conventional' robot builders at this size.



It's a nifty little machine and can climb over pretty much anything (note the plow goes 360° and if you only want to go forwards or back you can happily somersault along). Still rather a lot more to do, including cut and fit a titanium plow, it only weighs 650g at the moment.

http://www.youtube.com/watch?v=jn8JAMcWbQQ

I look forward to more arena news, especially if it involves an obstacle course!

[RogueTwoRobots]

Was wondering where you'd went Ewan, it's been a while since I've seen a post from you :P

Nice looking little kilobot there! That's probably one of just a few properly active ones around just now, most of the designs people have been discussing haven't yet fully materialised, mine included.

Those are the Lego Technic tracks aren't they? Just curious what you're using for rollers/hubs/whatever-you-want-to-call-them in place of the plasticy yellow rollers that are part of the Technic track kits, as I was contemplating making a tracked kilobot out of them but deemed the yellow bits too much of a weak spot for being brittle/not very robust.
In fact, a general parts breakdown would be cool if that's okay? Motors, controller etc?

[ewan]

They're actually the tracks from this kit http://www.inertialabs.com/srv.htm , still plastic hubs mind but somewhat tougher than lego (and given inertia labs is trying to sell them to the military, they're good enough for me!).
The motors are some of these http://banebots.com/c/MS-16XXX-050 , speed controllers are some of these http://www.robotpower.com/products/scor ... _info.html and all of it is run at 11.1v (a big fat 1000mah pack in fact, am probably going to run a smaller 14.8v pack for combat/short competitions, it lasts for 40mins of driving as of now). This build has been my first foray into carbon fibre and it's great stuff, tough as nails and yet cuts with the band saw like butter (has thoroughly blunted my countersinks though..).

Am liking the look of yours so far, was always a cassius fan tbh. What are you powering the arm with, if you've yet decided?

[razerdave]

Hey Ewan, long time no see

Last time I spoke to you in person was Exeter 2007, man its been a while.

I really ought to get to making my kilobot, these look awesome

[RogueTwoRobots]

Ooh I forgot about the Scorpion Mini controllers, they look quite nice and compact. Might well consider them if I end up increasing my battery voltage.

What I'm looking at for the flipper so far is a big heavy-duty servo. This one from Giant Cod reportedly has 20kg/cm of torque (although that is at 6V):

http://www.giantcod.co.uk/9805bb-towerp ... p-177.html

I'm going for a servo with that much torque in the hope that it will be quite similar to having a pneumatically powered flipper. To get a speedy flip and not just a push-up, I'm going to mount the linkage connection between the servo and flipper quite near to the flipper pivot point so the leverage ratio will be quite high. But hopefully with the high torque from the servo it will mean that there will still be enough power in the flip to chuck opponents and right the robot.

That, and the fact it's only £12

[daliad100]

What do people think to lego power functions as drive motors?

According to here the Xl motors have 40 Ncm stall torque, 220 ish rpm (no load, 9V), draw 1.8A when stalled and weigh about 70g and the medium ones have 11 Ncm stall torque, turn at about 400rpm (no load, 9V), draw 0.9A stalled and weigh about 35g.

I think they are both under 2 in all dimensions and you can probably do something about mounting them using the holes or glue/solvent (pretty sure the majority of lego is made from abs.)

[ewan]

Yeah Dave get building! =p at this rate we'll have a featherweight scale tournament by the time this arena is ready, I look forward to it.

The scorpions are very nice controllers, they've barely got warm after 40 minutes of driving about even packed together relatively tightly.

I'd imagine with a big enough servo you'd be able to pull it off (you've probably seen some of the antweights doing just the same thing), it's worth considering overvolting the servomotor to get some extra torque and speed (one thing I'd be wary of about the servo you've linked is the apparent lack of metal gears/no metal output stub to mount on which may lead to breakages if you're running at maximum torque). Of course if you overvolt you'll need to bypass the servo control board which likely wouldn't like it.

The lego motors look alright, certainly usable with those torque ratings although you can get better for the same weight. Do they have position feedback as the four-strand lead might suggest? =s

[widow_twanky]

What I'm looking at for the flipper so far is a big heavy-duty servo. This one from Giant Cod reportedly has 20kg/cm of torque (although that is at 6V):

http://www.giantcod.co.uk/9805bb-towerp ... p-177.html

Great minds eh??

Got two of those sat on my kitchen table. I've been testing these to see if they can be used effectively. They work just fine of a 7.2v lipo but are still noticably slower than you would want for a flipper although you could get something quite respectable in terms of tip speed with various mechanisms and a longish arm.

I'd like to run these at much higher voltages so will gradually increase the cell count until i get to 14.8V. Quick inspection of the internal electronics doesn't make me think this is too unreasonable. All the capacitors and stuff are rated for it, just depends on the little integrated circuits which i can't identify and the motor windings. The motor appears very similar to the Como Drills 918 which we are using for drive. It'll either end up as a melted mess or it'll work. Generally the results of this type of stuff is relatively instantaneous and very definite .

Anyone looking for a nice cheap speedo could consider doing what some of the antweight guys do and stripping the board out of these. Simply take out the potentiometer and measure the mid point and replace with two fixed resistors. ATM I'd say dont run them over 7.2V but I'll get back after I've wired up an 11.1v lipo and 14.8v lipo.

Andy