This time in five weeks we'll be in the midst of the Motorama 2013 competition, yet at the moment we have zero 'bots ready to participate. Losing a week to the 'flu has definitely impacted the build schedule, so we'll just have to see how much we can get back on track. Today we're going to focus on the 'bots that are closest to being done, so we can cross some things off the list. Hit Back after viewing an image.
So here's something new to us - a BotBitz ANTSwitch. We figured out last time how it works, which sounds silly, as it's only a switch, but it wasn't as intuitive as you might think. The battery connector for the fairyweight has been cut to length, and we've soldered it to one side of the switch.
We soldered a random length of wire to the other side, and snipped holes in the polycarbonate casing of the switch for both wires. Due to the sloppy soldering the switch fits extremely snugly in the case, so no tape or bolts required.
More soldering - this time all the ground wires on the fairyweight are being soldered together: two drive ESCs, the weapon ESC, and the negative lead from the battery. Fiddly, but accomplished.
After soldering together all the positives too, we were about ready to give the 'bot it's test drive! There are a couple of minor issues to get out of the way first, such as ...
Trimming down the prop-saver bolts on the weapon motor, to ensure that they don't rub on the top plate. The already had been cut off, but as the top of the motor needs to fit in a hole in the top plate now, we wanted to trim them down entirely.
At this point we were ready for a test drive, and bolted down the lid, with all the components fitting nicely inside - yay! The 'bot was zippy, as you'd expect with Pololu HP 30:1 motors on 3S and 1.5" wheels, but the weapon wouldn't spin up. We had previously tested all the components before assembly, and everything was fine, so we're going to have to tear down the weapon assembly and see what's up.
Disappointed with the fairyweight, we decided to take a break from it, and take a look at the antweight. The issue here is that the weapon ring doesn't want to spin up. We decided to disengage one of the motors and see if that helped. It did. A lot. The ring spun up just fine on one motor, but pretty quickly slipped out of alignment.
So we needed something to keep the ring in alignment. Specifically what we needed was a 9/16" outer diameter washer. Not having any on hand, we took a 3/4" OD bronze thrust bearing and judiciously applied it to the belt sander, to whittle down the outside. Eventually we ended up with something fairly roundish, that fitted nicely.
Having formally decided to ditch the second motor - hey, instant spare! - we decided to upgrade the battery pack. You can see too that we're using a couple of bronze bushings to keep the thrust bushing in place on the standoff. With the original 470mAh battery pack, we're at 15.59 ounces, so we're pretty much good to go, finally, with this 'bot.
Happy that we finally have some progress made, we turned back to the fairyweight, and started disassembling the weapon. You can see the problem here - one of the motor leads did not 'stick' when we soldered it to the speed controller. At this point we spent a good ten to fifteen minutes trying to resolder it, but the solder simply would not 'stick' to the motor wire. Frustrated, we decided to go mechanical, and needed a simple, lightweight way to hook these wires up.
Remembering our experiences with the PWM cables from the other day, we decided to crimp a pin set to the wires, and just plug them together. The pins were a bit fiddly to deal with, as everything was still mounted in the 'bot, but it worked. We taped it up, and put the battery on the charger before testing again.
Meanwhile, back with the antweight, and we finally worked out the best arrangement of motor, idlers, and washers. The battery on top of the 'bot is just a test pack, but with this arrangement of the original two idlers at 3 o'clock and 9 o'clock, and the washers effectively taking the place of the second motor, straddling the 6 o'clock position, the ring remained engaged on the weapon motor, and all was well.
The day was surprisingly warm for a January day, and we took advantage of that to deposit some paint on the chassis of our hobbyweight Steel Stiletto. Unfortunately the photo doesn't do the paint colour justice - it's a pretty loud, neon pink - you'll have to see it in person to get the full effect :-)
One final check on Poor Punctuation and you can see we're cutting it pretty close - 451 grams (forgot to change the setting). One pound is 454 grams, so this is 15.9 ounces - fingers crossed the official NERC scale is in sync with ours.
We didn't have all the bolts in for that test, and so the two that were in unscrewed themselves, which let the weapon ring slip off the motor, hence the sparks you saw at the end, but the weapon did actually spin up, and with that, we can declare we have a working 'bot!
After looking at the field of fairyweights for Motorama 2013, they all have spinning weapons, so Lauren decided to scale down her pushy-'bot design to 150 grams, and gathered up some parts. We'll throw together some CAD designs for it, and make sure it'll make weight before committing to it.
Ta-daa! Presenting Poor Punctuation 2.5! The scrape on the top right, by the way, is from drilling the top plate (titanium) with a relatively dull drill bit to enlarge the hole for the top of the motor - the plate spun at the very end and scraped the paint a bit.
And a second Ta-daa! Presenting the rebuilt Malicious Mule. This time we think we have the right balance of speed and torque, still within a quarter-inch thick 6061 aluminium chassis. With both antweights done, we can get some skirmishing in between now and Motorama. We're wrapping up today with 20% of the fleet ready for Motorama - hurrah!
Tags: antweight, fairyweight, hobbyweight, build, pp2, tt2, mm, teti
Picking up from last night, we have some antweight issues to work out, and a fairyweight badly in need of some chassis parts. This is our last build session of 2012, so we want to make it count! Hit Back after viewing an image.
We now have all the parts and pieces for the fairyweight, so we've thrown them on the scale, and as you can see they weigh in at a nice 147 grams out of the 150 allowed. Factoring in the fact we're going to be chopping wires down, and added a couple of pieces of double-sided foam tape, we should still comfortably have a few grams to spare when all is said and done. To building!
Here we've mounted the weapon motor speed controller, and are in the process of soldering it to the weapon motor. Lots of wire trimmed off, and hopefully we can keep the fiddly soldering fairly neat.
A short while later and we have all three connections hooked up, and taped down to the baseplate, with plenty of clearance for the weapon blade above. Not a bad job, if we do say so ourselves.
Here's the result of some fairly accurate marking, punching, and drilling: #0-80 screws that have been pushed through the chassis walls. The key question is was this accurate enough to mate with the waterjet-cut top and bottom plates?
All six bolts line up virtually perfectly, and we're very happy about that. Can you figure out what we're not so happy about? An error in judgement has left the side walls with what is essentially a pivot point. The drive motors are going to be attached to these, so there's a real possibility of the drive motors splaying out as the 'bot moves. Hopefully the internals are compact enough to keep pressure on the walls, and prevent that from happening.
Here we've manually milled a small slot in the front wall for the weapon motor wires. All told this is coming together fairly nicely, which is a pleasant surprise for a 'bot this tiny.
We've mounted the battery with a small piece of padded foam tape, and tucked the balance cable back underneath itself. The receiver sits on top of the weapon ESC, and the drive ESCs sit between the two drive motors. Speaking of the drive motors, we're going to de-solder them from the ESCs and re-solder them with a fair length of wire chopped out. That means breaking out the soldering iron, which is an ideal time to procrastinate :-)
We had a pair of antweight issues yesterday - one was that the weapon on Poor Punctuation wouldn't spin up, and the other was that the batteries we had installed in Malicious Mule couldn't put out enough amps to turn the 'bot. We tried numerous different batteries in the pushy-'bot, and eventually decided that a 3S 950mAh 25C LiPo pack was sufficiently capable of giving the antweight oomph, but without being so crazily-fast that we needed the gyro, so we pulled the gyro and original packs, and installed the new pack. At 15.76 ounces we were good weight-wise, and the mix of speed and torque was about right for Lauren.
We were still stuck troubleshooting Poor Punctuation, and decided to fore-go removing the weapon motors again for today, and instead just have a skirmish between the two 'bots instead!
And a good time was had by all :-) Now, though, it's time to clean up, order up some Indian food, and throw a Mystery Science Theater 3000 on the TV, and count down to midnight, and 2013. Happy New Year to everyone!
Tags: antweight, fairyweight, build, tt2, pp2, mm
After spending the last couple of days working on the heaviest weight class for Motorama 2013, we decided to turn our attention today to the smallest 'bots. We have an antweight that needs a test run, an antweight that is seriously overweight, and a fairyweight to rebuild. Hit Back after viewing an image.
Before we start trying to figure out where to lose weight on Poor Punctuation 2.0 we decided to finish the wiring, so that the internals were done. Soldering is never our favourite task, but it's time to get to it. The wiring is a little easier in this rebuild than the previous version.
After not too long we have the positive leads all hooked up. The battery connection is aligned with a hole in the top panel, so we can attach and detach the battery with a pair of pliers as our power switch.
A bit more soldering later and the negative leads have all been similarly hooked up. With everything connected, we have all the components in the 'bot that we need, so it's time to tackle the weight issue.
As you can see, we're a full ounce overweight. With no more wire to remove, we need to start looking at structural components we can remove, without compromising the 'bot's performance.
After removing half of the nuts and bolts holding the UHMW rings to the top and bottom panels, and a couple of the internal stand-offs, we realized we were going nowhere fast in saving weight, so decided to play with some battery options to see how small the battery needed to be to get underweight. As you can see here, we wound up with a very small battery. That's a 2S 180mAh LiPo pack. It claims to be able to put out 35C continuous, which would be around 6 amps - probably not enough to run both the weapon motors, but we'll see ...
We've neatened up the wiring some with the aid of a strategically placed ziptie, so let's power it up and see what works.
Not much. With that tiny battery, the drive is fine, but the weapon motors can't overcome the friction on the UHMW ring. Because of the leads that stick out the bottom of the motors, the motor is sitting at a slight angle, which means the gear rubs the ring. So we fiddled a while trying to level out the motors. We plugged in a much larger pack to see if we could 'work in' the gears with a bit of excessive power.
While this worked to a degree, it was becoming clear we were going to have to trim some of the UHMW away from the motor/gear.
Which meant removing the motors, which in turn meant having to reinstall them after Dremeling down the ring. We've mentioned before how fiddly the #2-56 screws and nuts are. Reinstalling the motors took a good hour! We finally ended up clamping the 'bot in the vise so we cdould sit the nut in place from the front and work the screw into place from behind.
Success! Kind of - we were finally able to get both motors running, but off the much larger pack to the right of the 'bot - not the piddly little pack inside the 'bot. We let the motors run until the pack was depleted, to maximize the amount of UHMW rubbed away by the gears.
Finally we decided to button the 'bot up, and see if we could get the weapon to spin with everything assembled.
It didn't. Off came the top once more, and we sanded down the idler gears, Dremeled off a bit more UHMW around the motor gears, and that meant reinstalling the motors once again. Grr.
Finally we spent a little bit of time (relatively speaking) ensuring the weapon ring started precisely in alignment. You can see the marks we made on the ring so we would know which teeth needed to start out meshed the next time we took the 'bot apart.
Frustrated with the spinner, we switched gears and bolted up Malicious Mule for a test-run. There are two 180mAh 2S packs in there, with a custom battery adapter to put them in series. During the testing it was obvious that this battery wasn't going to be able to put out enough juice - the 'bot did fine going backwards and forwards, but wouldn't turn. We pondered our options, and decided to check out our battery stash tomorrow.
Lastly for today, we're checking out the components of our fairyweight Transcendental Terror to make sure that all the pieces from the previous version still work before installing them in the new version. Both drive motors and speed controllers were fine.
And the new weapon ESC worked just fine with the old weapon motor, so that was good. Finally something that worked as advertised today!
The remaining parts for this bot as the chassis walls, so we took out the hacksaw and some UHMW strip, and roughly cut out four pieces.
This picture didn't come out very well, but the roughly cut pieces weigh 19 grams, and we only have fifteen left, so hopefully when these are trimmed to proper size, they'll make weight.
To trim them to size, we clamped them up on Milly, and manually shaved them down to the proper dimensions - came out pretty well for a manual manouever.
When all was said and done, the parts ended up at 10 grams - so at the moment we actually have a few grams available, in theory! That'll do it for today, we're thinking. Tomorrow we need to troubleshoot the spinner ant, find a decent battery for the brick ant, and assemble the chassis for the fairy.
Tags: antweight, build, pp2, tt2, mm
Boxing Day is traditionally the day when the upper classes would distribute food to poorer folk in the UK. Not sure that happens much any more, but for Team Radicus, Boxing Day is traditionally a build day! Hit Back after viewing an image.
We spent much of the day tinkering with our Hexy the Hexapod kit. Arcbotics released new firmware just in time for Christmas, so we updated our controller board, and also updated the control script. The kit behaved better, but it was still very squirrelly, so we decided to upgrade the power too. We switched out the AA alkaline batteries in favour of a BEC that could put out 6 volts at 5 amps. This really helped, but in complex manouvers there was still a lot of twitching, so we ditched the BEC and plugged in a 6.6V two-cell Lithium Iron Phosphate pack - suddenly things started working really well!
We taped the battery to the top of the kit, and set it on the floor of the Build Space, giving it a more stable space to wander around in, and played for a while, getting the hang of the controller interface, and also learning what the moves did in relation to the servos in the kit. Spending this time playing really helped us get the hang of how the controller is working, and helped crystallize some of the design elements we have in the back of our minds for the combat version of this kit.
After a very tasty Boxing Day roast beef dinner we decided to spend a few more hours building, opting to work on our antweight spinner. We mounted the battery pack, and started connecting up speed controllers.
With both drive speed controllers soldered to the drive motors, we moved on to the weapon speed controllers. These were just as fiddly as the drive ones, but we persevered.
Eventually the controllers were all installed, and taped down to the baseplate. That leaves wiring up the power sources and hooking up the receiver. At this point it's getting fairly late - and cold! - so we decide to call it a night.
As we're tidying up, we decide to see whether the wires we've shortened have helped much with the weight issue with this 'bot. So far we've saved a fifth of an an ounce, but we're still 0.8 ounces overweight, so we're likely going to end up removing some of those bolts in the 'bot.
Tags: build, Hex1, antweight, pp2
We recently picked up a couple of replacement speed controllers for the hobbyweight Steel Stiletto, and decided this evening to get them installed, so we could try running the 'bot with a gyro in it, to see if it would be more controllable. Hit Back after viewing an image.
The first step is to put some connectors on the ESCs, and in this 'bot we're using ring terminals, so we crimp a set on, which takes no time at all.
Having not run the 'bot in a while, we pause and hook up the batteries to chargers to let them get topped up. The batteries are well wedged into the 'bot, and we don't want to mess with taking the front and back panels off, so we elect to charge the batteries in place. We can't do a balance charge, but the odd standard charge shouldn't hurt them.
While the batteries are charging, we turn our attention to Poor Punctuation 2.0 and drill and tap a pair of new motor mounts, for #4-40 bolts this time, instead of #6-32.
Rather than try and extricate the 30:1 Pololu motors from the current mounts, we dig out a pair of 50:1 HP motors, forgoing a bit of speed, and press the motors into the new mounts.
After pressing on a pair of fresh 1" foam wheels, we install the mounted motors onto the chassis of the antweight. We also spent a little while contemplating the internal layout of the 'bot, trying to minimize the amount of witing we'll need to do, to see how much weight we can save, remembering that we were an ounce over last time.
The underside of the 'bot - that's a lot of screws! We're debating whether we can take half of them out to save some weight.
Meanwhile, the batteries in the twelve pounder have charged up, so we set about installing the new speed controllers.
Eventually everything has been re-installed, so we fiddled a bit to make sure the ESCs were plugged into the right channels on the mixer, and also installed the gyro for it's test run ...
... Which did not go well. The 'bot went into a death spin, ejecting the receiver, gyro, and a speed controller, which sparked as it came out.
Here's where the sparking happened: the PWM control cable on the ESC was sheared, so next time we get to building, we need to replace or repair the cable, and keep our fingers crossed that the gadget is still functional. So much for the gyro test ...
Tags: build, antweight, hobbyweight, ss, pp2
Shhh! Don't tell Lauren, but we're working on a Christmas present in the garage Build Space, but between waiting for wood stain to dry, we're stealing a few moments to work on the two antweights for Motorama 2013. Hit Back after viewing an image.
Having painted the titanium top and bottom plates last time, we used low-profile #4-40 bolts to attach the UHMW rings to the top and bottom. Thanks go to one of our colleagues for loaning us a T8 torx bit, as we didn't have one that small.
Next, we installed the 5/8" long aluminium spacers to the baseplate - so far so good, although we did strip one of the low-profile bolts. Here you can see the idler gears have been installed.
And on to the motors - we're reusing the motors from the last build of this antweight, although we will have to test them to make sure they work - it's been a while. Also, installing these motors is a bit fiddly!
Very fiddly, in fact, but with conviction and patience, not to mention a small pair of needle-nose pliers, we finally get both motors installed.
Here's the weapon system with both motors and both idler gears installed. The weapon ring spins freely, and doesn't shift out of alignment now that all the gears are at 90 degrees to each other.
Hmm - here's the bad news: the 'bot is currently an ounce overweight. Uh oh. We'll have to see once we've trimmed all the wiring to fit just how much we need to drill out of the titanium top and bottom plates. Hopefully not a whole lot - no pun intended!
No such worries (yet) for our other anweight - Lauren's Malicious Mule which - without two ounces of motors weighs in at 13.5 ounces, so plenty of breathing room. Seeing as though we have the 'bot out, we decided to drill and tap all the frame pieces to allow them to be assembled together, and have the top and bottom plates installed.
Things go together quite well, but not perfectly, so we may end up having to widen a few holes in the top and bottom plates, and even put the front and rear walls back on the mill for a little tweaking. But the 'bot feels solid, and as soon as the motors show up from Pololu, we'll be going full speed on wrapping this one up!
Tags: antweight, build, mm, pp2
Having spent yesterday playing with our Hexy Kit, we decided to spend some time on the rest of the fleet for Motorama 2013 today, so we picked up a bunch of parts that arrived while we were out of town earlier this week. Hit Back after viewing an image.
The first parts out of the box are top and bottom plates for our antweight Poor Punctuation 2.0. These 0.032" titanium pieces are to replace the 1/16" polycarbonate that the bolts pulled through last time out. There shouldn't be any way those bolts are pulling out this time!
From the same 0.032" titanium we had top and bottom plates cut for our smallest 'bot, Transcendental Terror 1.0. The intention is to ensure that the 'bot can run inverted this time around, which is why the top and bottom look the same.
Here are some polycarbonate parts for Lauren's antweight Malicious Mule: top and bottom plates cut from 1/8" and some motor mounts cut from 1/4".
Here are some miscellaneous parts for a comical beetleweight design, Lincoln Limboer 0.9. We probably won't take this 'bot to Motorama, but you never know ...
All our spare motor mounts - universal press-on mounts for all the Pololu motors we use on the top, and clamp-style mounts that are also good for the Pololu-type motors, but can also be used for bolting into the front of the motor.
Some heftier half-inch polycarbonate parts for our featherweight redesign, Intrusive Interloper 3.0 - enough parts to make five of the drive pods we're going to build. Guess we should think about ordering some motors, ESCs, and gears, eh?
More parts for the featherweight: top and bottom plates cut from 0.071" titanium. The top plate has a battery access panel cut out of it, to make swapping the battery significantly easier between matches - three bolts beats 46!
Some simple marking to begin with, using the calipers to etch the midline of the polycarbonate parts for the 30lb'er in preparation for drilling and tapping. At least it's unlikely we'll break a tap in plastic ...
Here we've thrown together the parts in hand for Malicious Mule, and realized that we were supposed to slot the front and rear walls for the side rails, so we load those up on Milly and let her at it.
While Milly is doing her thing, we broke out the primer and gave the 0.032" titanium parts a basecoat. Almost time to get a new can of this stuff, but it does seem to help.
While the primer's drying we turn our attention to the featherweight, and having already slotted the front and rear walls, we can put the chassis together and check the top and bottom panels. The walls will need a turn on Milly to cut a 0.071" lip for the top and bottom panels to sit in.
Here's a quick mock-up of the drive pods in the body of the 'bot. Looking forward to seeing these in action with snazzy FingerTech wheels. Hopefully they'll hold up [crosses fingers].
Here's a quick weight check for the fairyweight - it's currently running at 96 grams out of the allowed 150, with all the internals. That leaves 54 grams for the chassis, and the top and bottom plates are 19 grams each, taking us to 34 grams left for the walls and bolts. Shouldn't be a problem.
The primer's dried, so it's on to a covering of Team Radicus Purple. Still haven't figured out why it always photos as more of a blue, but no matter.
Milly's done her thing with the front and rear walls for Malicious Mule, and here's a test fit - looks good. Next to do is drill and tap the walls and motor mounts. Oh, we'd better order some motors too ...
This slightly blurry shot was taken after finally managing to install the weapon onto the base plate of Transcendental Terror 1.0 - those #2 screws and nuts are fiddly, but we got there eventually! The motor leans forward very slightly due to the wires that protrude from the underside - we were originally going to run them under the 'bot, but this will work just fine.
Here we're testing clearance on the top plate - looking good! We will Dremel down the prop-saver bolts a touch more just to be on the safe side, but really the next big thing to do for this 'bot is cut the chassis walls.
The CAD model said everything should fit, but looking at things in real life we have our doubts, but we're going to soldier on anyhow, and make it all fit, by hook or by crook.
Malicious Mule's drive train upgrade involves using proper axles - specifically ones from FingerTech designed for Lite Flite wheels. We've drilled the hubs out to 5/32" and they fit nicely. We're going to cut off that excess on the left hand side, and use a dab of glue to secure the shaft to the hub.
All four axles/hubs/wheels are ready to be attached to the drive motors next weekend. We want that part of the build to go smoothly, and have everything ready for when the motors come in ...
... So we'd better get on and drill and tap the motor mounts. Actually, as we had everything lined it, it was time to break for dinner, so we'll pick this up [hopefully] tomorrow evening - Same 'Bot Time, Same 'Bot Channel!
Tags: antweight, fairyweight, featherweight, mm, ii3, tt1, pp2, build
We had high hopes for Poor Punctuation 2.0 when we took it to Motorama 2012, but those hopes were quickly dashed by a malfunctioning weapon and some nasty hits from Gyroscopic. [Unlike a certain other antweight we took - Ed.] We tried to work out how to redesign the 'bot for the Franklin Cup 2012, but couldn't figure out how to get it underweight, so we shelved it. Now the competition is done, and Motorama 2013 is a mere four months away, we decided to take another swing at it. Hit Back after viewing an image.
In the first version of this 'bot we had 1/16" polycarbonate top and bottom plates, with counter-sunk #6-32 screws. In our match with Gyroscopic we took a hit that essentially pulled the screws through the top plate, opening the 'bot up. To prevent that from happening this time we're switching the 0.0625" polycarb for 0.032" titanium. We're also switching from flat-head screws to low-profile button-head style bolts. We're re-using the UHMW rings that the weapon ring rides on.
We've also adjusted the layout and size of the spacers, going from 13 of them down to 10, and switching from #6-32 threads to #4-40, to decrease the weight of the many screws involved.
The drive is transplanted from the existing 'bot - a pair of Pololu 30:1 HP gearmotors with pressed on 1" ultralight foam wheels, and polycarbonate motor mounts.
The other issue was the weapon ring not spinning up. Here we've made sure to align the weapon motors and idlers at 90 degrees from each other, to ensure the ring is centered.
One thing we're not sure about is the battery - it was a 3S 470mAh pack, but due to weight we may need to drop down to a 370mAh pack. The red weapon ESCs are the same, and so is the 4-channel Spektrum receiver.
Here are all the internals in place. The only thing you're not seeing are the TinyESCs that power the drive motors, but experience tells us it's going to be pretty easy to cram them in between the drive motors and battery.
Here we've buttoned the 'bot up. Yes, it will take fourteen screws to access the inside, but we're leaving a hole to access the battery connector and will use in-'bot charging unless we're pressed for time and need to simply swap in a second battery.
Here's the bit we're worried about: weight. We did figure out why we were having such a tough time getting close on weight before - we had the density of the weapon ring and gears set to steel, not titanium, which doubled their weight.
The estimate there doesn't include the copious number of quarter-inch long #4-40 screws that hold the 'bot together, so we're going to have to keep our fingers crossed that we've over-estimated, and that we can trim enough wire, etc., to keep the weight to a pound. Failing that we'll be drilling the heck out of the UHMW rings, and potentially the top and bottom panels, in addition to switching the battery.
One final render with (bright) team colours - we obviously picked the wrong purple in Rhino this time, and the sheer quantity of steel bolts really does stand out ... Next step is ordering the titanium and having it cut - watch this space for updates!
Tags: antweight, design, pp2
The last two days we were on the road ... it was a relatively dull drive, which is a good thing: no speeding tickets and decent time, despite the near-constant rain through Arkansas and Tennessee we made good time to the hotel the first night and the Competition Hotel Thursday night. A gin and tonic or two the night before, and we were up and ready for Robot fights this morning. Hit Back after viewing an image.
Our hotel room this time has a stand-alone hearth, which is actually pretty neat, but still: we mustn't dwell - this is the first day of competition and we have 'bots to fight!
We made it to the arena about 8am after a quick diversion for coffee, and took a pair of tables near the main arena area after hopping a ride in with a quad-ride which was much easier this year due to the investment in the additional container for all our small parts. At arena-side there wasn't much happening yet, as the small arena was still being constructed, so we went back to work on our Sportsman.
We were pitted next to Mike and Julie of Near Chaos Robotics, and Mike was good enough to lend us an extension cable for the drill press - Thanks Mike! It's quite a nice feeling to roll into the pits and not be franticly wiring something at the last minute. We had eight 'bots ready to fight, and the Sportsman was really a distraction - we were going to put some effort into getting it ready, but not worry too much if it doesn't get done in time.
For the first couple of hours it was just Sportsman-building and battery-charging, but the small arena had been assembled, and safety inspections for the fairies and ants started. Transcendental Terror 1.0, Poor Punctuation 2.0, and Malicious Mule all passed without a hitch, so all that was left to do was to wait for the brackets to be generated, and the fights to start!
As it turned out, Lauren was going to be thrown into the pool at the deep end - not only as one of the very first matches, but against a nasty-looking beater called OverClock. Here we go, then, the first match for a first-time participant:
YAY! A win! It should be confessed that Toni was more than a little jealous, having had to go through about five competitions before ever winning a match, but we suppose the experience helped, and Malicious Mule collected a winner's pog! Hurrah! Lauren did a pretty good job driving, and after the match we checked out the 'bot, but there didn't seem to be any damage at all, so the battery was put on the charger (not that it really needed it) and we lined up for our next match: Poor Punctuation 2.0 versus Mateo:
Well, darn it - the judges gave the win to Mateo, and we were left scratching our heads as to why the weapon hadn't spun up - it had worked just fine back at the Build Space, so something must have gotten out of alignment, so we headed back to the pits to take the top off and take a look. There didn't seem to be anything specific - the weapon motor gears and the idlers all looked to be engaged with the weapon ring gear ... hopefully we'll see signs of life from the weapon in Poor Punctuation 2.0's next match, but right now we're headed back to the arena for Malicious Mule's next fight, against Ferocious:
It looked from the outset that Ferocious had one side of the drive train out, and once again Lauren did a good job driving Malicious Mule, but the judges gave this match to Ferocious, presumably because it appeared to be engaging us more than the other way around. Again, though, no damage so the 'bot went back on the charger, and we had a little time to take a breather. Lauren's cousin and her husband had come out to visit, and they enjoyed themselves watching the matches, and generally catching up.
Next it was the turn of our smallest 'bot, Transcendental Terror 1.0 to head into the ring, up against a hacked R/C car called Rosie the Littler:
Unfortunately the blade on our fairyweight kept getting stuck in the thin aluminium on the front of the opponent, rather than really doing any major damage, so we spent a fair bit of time locked together during this match, but the Pololu motors on Transcendental Terror 1.0 were more than up to the job of running both locked 'bots around the arena, until eventually Rosie the Littler tapped out. A debut win for the fairyweight - yay! The next match rolled around quickly: Malicious Mule versus the spinning bar of Odahviing:
As with the match against OverClock, Lauren was able to drive Malicious Mule straight into the weapon of Odahviing, disabling it! From there it became a game of "Chase Me" as Odahviing kept running for space to be able to try and spin it's blade up again, while Malicious Mule kept after its opponent. Lauren had more pushing power, and with the weapon out of action, by the time the match went to the judges, it was fairly clear that Malicious Mule had prevailed! Yay! Again, the 'bot was put on the charger, and we lined up the next match, which was Poor Punctuation 2.0 versus Gyroscopic:
Grr! Again, the weapon wouldn't spin up, and without it we were ravaged by Gyroscopic, who put some good hits on Poor Punctuation 2.0, although in re-watching the video, we also caused Gyroscopic to take a few flips too! All in all, a fun match, but the last hit from our opponent split our antweight open, and we tapped out, as we didn't want to lose any of the internal components to another hit. We didn't have much time to mourn the antweight crashing out of the competition zero and two, because the fairyweight was up next!
An early hit on lolcat appeared to have knocked out one side of its drive, but we weren't in a position to capitalize on that fact, as we were upside down, and unable to right ourselves. Unfortunately the wheels on Trancendental Terror 1.0 weren't quite big enough for the 'bot to be able to drive inverted - oops! So although we were able to get a little motion, we had to hope a hit from lolcat would right us, but with one side of its drive out, lolcat had issues getting to us for that hit, until eventually we burned out the speed controller for the weapon motor, which was also powering our receiver, and the 'bot was dead.
Back at the pit table we had some time before the next match, so we pulled a speed controller from Poor Punctuation 2.0, scrounged some solder from Mike (thanks again Mike!), and replaced the controller in Transcendental Terror 1.0, getting it working again - phew! After that repair, we had a few more minutes free, then it was time to line up for another match with the star rookie: Malicious Mule versus KnightLight.
A tough match for Malicious Mule - a faster opponent with a veteran driver, but early on it appeared that one side of KnightLight's drive gave out, and Lauren was able to pin KnightLight repeatedly, winning the judges' vote at the end of the match! Three wins! Hurrah! There was a bit of breathing room, so the 'bot went back on the charger, and we waited for the next match to come up on screen. As it turned out it was Malicious Mule again, and against another fast, experienced wedge again, although this time it was our pit neighbour Mike, with Kobalos:
Phew! A very tough opponent and with its years-old Copal motors Malicious Mule was outclassed by Kobalos, leaving us with a second loss, and Malicious Mule was done for the day, but with a very respectable 3-2 record! Well done Lauren! We still have one 'bot running, and it's time for another match: Transcendental Terror 1.0 against Kongol:
Something was up with our 'bot - one side of the drive wasn't running, but the first hit was a good one, flipping both us and Kongol, although only one of us was able to self-right, and it wasn't us! With the next hit we took the saw blade off Kongol and cut his weapon motor wires, but unfortunately we were stuck on our back unable to show any movement, so Transcendental Terror 1.0 was counted out for lack of movement, a Technical Knock Out for Kongol.
For the rest of the afternoon we watched some matches, tinkered with the Sportsman, and chatted with Lauren's cousin and husband. At the end of the day, we packed away the 'bots, and headed back to the hotel for some pizza, a shower, and a good night's sleep!
Tags: motorama, competition, fairyweight, antweight, mm, pp2, tt1
After a very busy work week we were looking forward to making some 'bot progress this weekend, and we have a couple of 'bots very close to being done, so we're going to concentrate on those this weekend. First up, the second version of our antweight spinner: Poor Punctuation 2.0. Hit Back after viewing an image.
Last time out we decided that we needed some idlers for the ring, and found some aluminium spacers, pressed the titanium idlers onto them with extreme predjudice on the arbor press, and installed them in the 'bot.
Which caused an issue - the ring terminals are too bulky with the idlers installed, and we didn't want them getting in the way, so we decided to remove them and look at alternative ways of wiring the 'bot.
With all the ring terminals out of the way, we sat for a while trying to figure out whether we could solder the leads together. They didn't all stretch to a common point though ...
And then we had a brain wave! Inspired by thoughts of old "Vampire Taps" in networking, what if we ran two 'bus' cables for positive and negative, and 'tapped' into them for the components? Sounds like an idea, so here we are soldering a weapon speed controller onto the busses.
And it actually was pretty painless to complete - we're going to have to remember this trick for other small 'bots!
We were almost ready for a first full test drive! We spent a bit of time with the 'bot hooked up to the battery charger in preparation, then ...
Tags: antweight, build, done, pp2
We didn't get anything done over the weekend on the 'bots, as we had some pretty big issues to deal with at work, but this evening we decided to see if we could wrap up the antweight Poor Punctuation 2.0. We need to install the weapon speed controllers and finish the wiring - ugh. Hit Back after viewing an image.
Unfortunately the bushings we ordered for the idler gears haven't arrived yet, so we'll approximating with some random bronze bushings and installing the weapon ESCs around them.
The ESC is a 12A HobbyKing cheapie, but light, and does come with a programming card. It can be programmed via the card to run in reverse, so we're going to be soldering the connections to the motor, as we won't need to undo them to switch direction if the leads are hooked up wrong. Here we're testing that the R/C connector we put onto the cut-down Y-cable works - success!
With one side done, we turn the 'bot through 180 degrees and start on the other side. We're trying to make sure that the spacer closest the wheel is keep clear for the idler, as we route wires, etc.
At this point we're verifying that both motors do run in the same direction: the don't. But on the plus side, our Y-cable works, and our soldered connections from ESC to motor are good, so we can move on.
To fix the motor direction we flipped the jumper on the card, applied power to it, and connected the ESC to it - took a couple of tries, but eventually we had it sorted out, and moved on to the rest of the wiring.
Not trusting our soldering skills to hook up five wires for negative in a single connection and the same for positive we decided to break out the ring terminals and go that route. Sure, they add weight, but last time we checked we had about an ounce spare, so no problems. The main issue is that they take up space, and that is a precious commodity inside this 'bot, but we managed to squeeze everything in, and we were ready for a quick weapon test!
After verifying that the ring did actually turn (and yes, we were kneeling behind polycarb while that test was being run - the white sparks at the end were due to the ring coming off the motor gear) we bolted down the lid and tried again, but this time there was too much friction for the ring to spin up. On review the cause of the friction isn't the UHMW buffers, but cabling inside the 'bot catching on the motor gears and not letting them get up to speed. There's also the issue of the ring getting out of alignment because one motor spins a touch faster than the other.
So close! All we need are our idler bushings, and we're going to have to hit YouTube for a crash course in soldering so we can neaten up the wiring and make everything fit inside the 'bot! But this 'bot will be finished by the weekend, and we'll be on to others ...
Tags: antweight, build, pp2
We received some parts today that mean we can get back to our cutest 'bot: Poor Punctuation 2.0, and see whether we can install the drive ESCs. Unfortunately this was going to mean soldering - never our favourite task - but we steeled ourselves to the task and decided to see where we can get to. Hit Back after viewing an image.
Here are the parts in question: eight TinyESCs, version two, from Kurtis at FingerTech Robotics. These things are awesome for fairies and antweights, and in a pinch can be used in a beetle, depending on the motors. Plus Kurtis gives amazing customer service, so if you're looking for small-bot ESCs, definitely check these out!
Here's our current situation - 13.47 ounces with everything but the weapon ESCs (which should arrive tomorrow) that weigh less than an ounce for the pair of them. We have plenty of weight to work with. We've also thrown in a couple of bronze bushings and two idlers for the weapon ring to help keep it in alignment.
As we're going to be soldering in the drive ESCs we need to make sure we're going to get them hooked up with the right polarity to the motors, so we're running some tests to verify which lead goes where. As you can see we've tied the battery down to prevent it from sliding into the weapon motor gears and getting chewed up.
On to wiring. We've stuck down the receiver with some heavy-duty 3M double-sided tape, and started routing wires. In order to run both weapon ESCs at the same time we need a Y-cable, but for some odd reason the only cable we found was quite literally two feet long! Fortunately we have pins to be able to cut them down and replace the connectors.
At this point the TinyESCs have been stuck down and soldered to the drive motors. We've been careful to leave clearance around two of the stand-offs where the weapon idlers will be located.
Test Drive Time! We didn't take video because it wasn't super-exciting, but it was great to see the 'bot running around under direction. The wiring is going to be super-tight, but we think it's doable.
Now that we have the 'bot running around, you can see from our To Do List there isn't a whole lot left to do on this 'bot - as soon as the weapon ESCs show up we'll wire them in and take the 'bot for a real test drive!
Despite trying a number of V-belts from Grainger, we still hadn't found a decent replacement for the drill press, so we had to find other things to work on this weekend. We do have a lot of drilling and countersinking to do, and we're waiting for more parts to show up, so we decided to tackle the things we could actually finish without the drill press. Hit Back after viewing an image.
We started out with some 3/4" UHMW blocks loaded into Milly's vise and a quick G-code script to cut out the wheel holes. We did three blocks, just to be on the safe side.
Another G-code script later, and we had cut the lip in the other side of the block for the top plates. Unfortunately we were down to two blocks at this point, because of a mistake mixing X for Y, and ruining a piece.
Here we've been scribbling to determine the paths for the half-inch end mill for the next two G-code scripts to cut out the insides of the chassis.
The outsides were easy. We had issues a while back trying to cut the whole block because the UHMW flexes in the vise, so we used aluminium spacers to prevent that from happening this time.
And success! Two fairyweight chassis blocks ready for the internals to be added, and no errant cuts. We still need to cut slots for the arm, so that's out next task.
Et voila! We've cut the slots for the arms, and the waterjetted top plates fit great! We finally have a fairyweight chassis to work with ... just as soon as the drill press is back in business.
We spent an hour trying to get the weapon motors mounted in the antweight, but the #2-56 nuts were too big to fit against the weapon motor can, so we decided to sand them down a bit and try again.
Yay! After fiddling around for quite a while longer we finally had the weapon motors installed, and they look good! We Dremelled the titanium gears out to fit the motors and Super-Glued them to the motors earlier this morning.
Here we've tested the fit with the weapon ring, and life is good, although this isn't quite as good as we had in our mind's eye, because there's the potential for the ring to move out of alignment if the two weapon motors aren't perfectly in sync, so we may have to add the idlers back in to this design.
Here we've milled down the lower UHMW ring by 1/32" and the titanium ring moves pretty smoothly, so hopefully we won't need to add bearings to the UHMW.
Tags: antweight, fairyweight, pp2, mm1, build, mill
We decided last night that we had to do something about the garage Build Space as it had become too messy to work in, so this morning, before building we spent a couple of hours tidying up and generally getting organized. It's going to be a short build time, as we're going to the movies tonight - Yay Alamo Drafthouse! - so let's see what we achieved ... Hit Back after viewing an image.
Here's where a couple of hours of tidying and organizing have gotten us. The worktable is clear, and all the 'bot parts are organized. Unfortunately the ShopVac seems to have run out of 'suck', so chances are we'll have to replace it soon, and probably for a larger model, as Milly does produce an awful lot of chips.
So, back to 'bots, and we elected to work on Poor Punctuation 2.0. Luckily, the Super Glue seems to have done it's job on the motor and gear we messed up last night, so we were okay to proceed. Note that on the bottom of the motor both the shaft and electrical wires protrude below the base of the motor, so we started by drilling a couple of clearance holes in the baseplate.
Next we attached the UHMW spacers with #4-40 bolts. We could have sworn we ordered our customary black oxide finish, but no matter. Note also that the bolts are not entirely flush with the polycarb - that's okay too - we'd rather have the 'bot ride on steel than the polycarb.
On the inside now, and here the 12 aluminium spacers that hold the top and the bottom of the 'bot together have been screwed down to the baseplate.
The battery pack fits exactly inside the spacers, although there is the potential for the pack to move sideways, which would put it in direct contact with the weapon gear in either direction, so we're going to have to come up with a restraint ... a ziptie running around the four middle spacers would probably work fine.
This is where the weapon motor sits. For some odd reason we don't have any fasteners to be able to bolt the motor down, so that'll go on the next McMaster order. We also ordered replacement motors for the one we destroyed last night from HobbyKing's USA warehouse, so they ought to show up next week.
Here's what the 'bot looks like with the top on! Truthfully the titanium weapon ring doesn't spin as freely as we want it to, riding on the UHMW, so we may mill a few thousandths off them later.
While we're here we may as well install the drive motors. Here are the motor mounts - drilled and tapped 1/4" polycarb with the outside shape of the Pololu HP 50:1 motor waterjetted into it.
With a tiny bit of filing and a quick push from the arbor press, the motors are happily situated in the mounts (the gearboxes are rectangular, so the don't go back any further in the mount) and the mounts were reinstalled.
With the top back on, you can see that the 'bot is actually invertable - yay!. The little battery hole we had cut works well for accessing the battery plug, so that'll be our power disconnect, and we can also put the whole 'bot in one of the Jumbo LiPo sacks when it comes time to charge it up! :-)
Time to see how we're doing weight-wise. The original design had steel weaponry rather than titanium, and was about 90% of a pound. As titanium is nearly half the weight of steel, we expect to be rather light. The chassis, drive motors, and weapon ring are 10.9 ounces.
Piling on as many internals as currently have, the weight goes up to 12.8 ounces. Factoring in another weapon motor/gear combo and speed controller, we're guessing we'll wind up at about 14.2 ounces. Hmm ... maybe we ought to invest in a couple of rare earth magnets ...
The top of the 'bot is right at 7/8ths of an inch, with the wheels sticking up another eighth, making the whole 'bot just one inch tall. Nifty.
And putting the weapon teeth right at half an inch above the deck, so hopefully at our opponents' tire level!
Right as we were packing up to go clean up for dinner and a movie the UPS guy showed up again - this time with the remnants of the water-jetted material, which made for an interesting (to us) photo :-)
We've had a pretty productive week so far! We're making good progress on two of the beetles, have one 'bot done, and are really waiting for parts to show up to get cracking on the others we're planning on taking to Motorama 2012. While we wait for those parts we have some pieces we can make ourselves, and we still have the wiring to do on Unlettered Understrapper 2.5. Hit Back after viewing an image.
We set Milly off and running on the remaining aluminium parts for the featherweight. While that was going on we decided to finish the lifter for the beetle. We've drilled and tapped one hole for the crank, to fit a #6-32 1" screw which will be Loctite'd in after assembly.
Looks like Milly has finished - we have the three aluminium wall pieces and a spare for each. Still some drilling and tapping to do, once the top and base plates show up.
With the aluminium done, we set Milly off on the UHMW wall pieces, and went to go find something else to do.
Here we've bolted in the crank for the beetle lifter. We still need to round off the ends on the sander, but it's looking okay so far.
A bit more drilling and tapping and the rocker arm has gone in place. Again we need the edges rounding down, but it's coming together nicely.
For fun, we decided to put the arm into place in the 'bot, using hex keys, and the holes all line up, so yay! :-)
Here's where the arm extends to, give or take, and it ought to be enough to be able to fall to one side and roll on to the wheels again. The only issue is that cranking the arm takes a bit of force, and we're not entirely sure whether the HD servo we have is up to the task. We'll have to see when the 'bot is a bit more assembled. We can always switch to a gearmotor, and figure out limit switches using a Team Delta relay.
Yay! The UPS guy just dropped off a fairly large box - let's see what's inside!:-)
Parts for Formidable Fustigator 2.0: base plate; top plate; and boom strengtheners.
Parts for Poor Punctuation 2.0: top and bottom plates for a one-weapon-motor configuration; top and bottom plates for a two-weapon-motor configuration; a pair of UHMW rings; and titanium weapon ring and gears.
Parts for Malicious Mule: top and bottom plates; inner walls; spare outer walls; front and back plates; and aluminium outer walls.
Parts for Didactic Duelist 1.5: base plate; top plate; side walls; wheels walls; engine mounts; rear walls; and side walls.
We couldn't resist: we had to do a little on the antweight parts! Here we've drilled the UHMW rings slightly to accomodate #4-40 locknuts.
And with minimal effort the locknuts have been pressed into place. We had originally envisioned regular hex nuts, but inexplicably we don't have any, hence the locknuts.
Here's how the antweight parts stack together - polycarb, UHMW ring, titanium weapon ring, UHMW, and then polycarb. There will be a bunch of spacers holding everything together.
Meanwhile, Milly is still turning away on the UHMW parts. Because even half-inch thick UHMW is a bit bendy, we're only doing four inches at a time - the width in the vise, to ensure that at least that much doesn't flex while we're cutting.
Here's the front wall for the 30lb'er, and it's 26.5" long, so we're having to work around the lathe chuck to be able to get the middle of the part, but we finagled it successfully.
Here's a test-fit of the 30lb'er walls on the baseplate. If you look at the back wall, it's not sitting on the baseplate, so obviously we messed something up. On closer inspection we mis-measured the length of the side aluminium walls - they should be a quarter-inch shorter! Thankfully that'll be pretty easy to take care of tomorrow, so we've put it on the list of things Milly has to do tomorrow.
A quick trip to the mailbox yielded junkmail and a package from Hong Kong - more spiral bevel gears! We were planning on using these on the 30lb Sportsman Walker Cyber Scorpion 0.9, but we've scrapped that idea - just too complex with not enough time for Motorama 2012, but on the plus side it'll be a project that will keep us engaged in 'bot-building through the year, rather than just the few months leading up to Motorama 2013 ...
Here we've already counter-sunk all the holes for the top and bottom plates for the antweight's two-motor configuration, so we're about to throw some team colour on them, while we fiddle with some other parts ...
... Namely the antweight weapon motors. They came with set screws in place for prop-savers, but by golly they were in there tight! We ended up Dremelling them off.
Right - we've taken the can off one of the motors intending to press the titanium ring onto the can!
Er - yeah ... not so much. We've mangled the can pressing the gear on, so something's obviously not right here. We broke out the calipers, and groaned. For a press fit you typically aim for three or four thousandths difference in size. What we have here is four hundredths difference. Grr. Our bad on the DXFs we sent to the Whyachis, so what can we do about it?
We set the Dremel-a-like onto it and see if we can neatly take the inner diameter of the gear to somewhere close to the motor outer diameter. Unfortunately we got far too carried away - not realizing the Dremel-a-like worked so quickly on Grade 5 Titanium, and now the ring just slips down the motor. Drat!
At this point we have one good motor, one bad gear, and two fresh gears. Obviously we're going to have to order some more motors, but we started wondering whether we could reclaim the bad gear some way, so we built a jig ...
... And applied some Loctite to the motor/ring combo. Ordinarily we'd have used duct tape, but felt this operation needed a little more finesse. The jig has the ring 0.25" from the bottom of the motor, so if this works we have one working weapon motor. We'll find out in the morning whether we were able to save the titanium gear.
But the first thing we have to do tomorrow is clean, tidy, and organize the garage Build Space, because we wasted a whole heap of time today simply trying to find things! This place is a bomb site hit by a tornado! So that's the plan for first thing tomorrow. For now, we're going to have a gin and tonic, and order some motors ...
Tags: antweight, beetleweight, build, dd1, featherweight, ff2, mill, pp2, vv1
The last version of Poor Punctuation had a pretty major flaw - well - two flaws really: (1) It was pretty ineffective in the weapon category; and (2) it wasn't invertible, and flipped over frequently. With those issues in mind, we set about redesigning the antweight, wanting to invest as much Moment of Inertia as possible into it's weapon, which would translate into kinetic energy, and make the 'bot invertible. Here's what we've come up with! Hit Back after viewing an image.
Starting from the bottom-up, we have a 1/16" polycarbonate baseplate, and on top of that is a 6" diameter ring of quart-inch thick UHMW. There are eight #4-40 nuts pressed into the UHMW, which are bolted into from the baseplate.
And the same again with the top plate, and upper UHMW ring. These two pieces leave a gap that is an eighth of an inch.
Because there's no direct attachment of the top and bottom through the walls, we need another way of holding things together, so these are 5/8"-long threaded spacers for #6-32 screws. Between the 13 of them, they ought to keep things fairly solid.
Putting the top aside, you can see here the weapon. The outer ring has 140 20 pitch teeth cut into eighth-inch steel, and two teeth. This piece will be waterjet-cut, and mates with the large gear you see in the bottom-left, which has 35 teeth, for an effective reduction of 4:1. The other two gears are idlers with a bearing in the, spinning freely on the spacer, to prevent the ring from being able to move around. Well ... obviously the ring moves a-round, but not around, if you catch the drift?
The weapon motor is a Turnigy 2204-14T which almost squeezes into the 5/8"-tall space inside the 'bot, but not quite, hence the hole in the top plate. The driving gear for the weapon is press-fit around the can of the outrunner motor. Nifty, eh? The red block is a 10A speed controller for the weapon motor.
Here are all the other bits, including our trusty Sozbots drive speed controllers, although if we have the cash we'll switch them for FingerTech tinyESCs; the drive motors are the same Pololu HP 30:1 gearmotors and 1" wheels from version one, and in fact so are the 1/4" polycarbonate motor mounts. There's a 460mAh 3S lithium polymer battery, and an OrangeRx receiver to wrap the internals up.
Here are all the internals in the 'bot. And there's even a little bit of space! We were contemplating two weapon motors, but we don't have the weight for it. The 'bot is 7" in diameter from tooth to tooth, and 3/4" tall, except the wheels.
At the moment we have about 1.6 ounces unaccounted for, but as you can see in the list above we haven't factored in the weight of all the fasteners yet, nor have we worked out a power switch, so that 10% of the pound will probably be eaten up quickly!
And of course a render in team colours :-) For those counting, in order to get at the battery, we need to undo 17 screws ... that's rather a lot, so we're trying to figure out whether we can make a battery hatch, and keep it under weight ...
Tags: design, pp2, antweight
While snacking at lunch time I started playing with a new program I downloaded from WoodGears.ca called Gear Template Generator. It took a couple of minutes to figure out the interface, but within moments I'd come up with this:
Using the Export to DXF function I was able to pull the ring gear into Rhino3D, tweak the outside dimensions, and add a couple of teeth, then extrude it into a solid. To have this waterjetted from 1/8th-inch steel would leave an antweight weapon blade weighing 2.75 ounces, which sounds very fair!
Now to design the rest of the 'bot ...
Tags: antweight, pp2
This site contains records of our trials and tribulations in building combat robots. So much to learn, and so little time!