Now that we've actually made a start on the beetleweight walker, we need to seriously consider a weapon for it. The plan all along has been an overhead hammer, so we need to work out how to build one and affix it to the body. We've not made a hammer before, so it's been a challenge trying to figure out the best way to put one together, and here's our initial design for it. We wanted it to be able to rotate, to be able to attack on the sides of the 'bot, but that was a bit too much complexity for the first time out. Hit Back after viewing an image.

To keep things simple, we'll start with the top plate of the body. From there we'll put eight one inch long #4-40 threaded stand-offs in, to give us some space from the mess of cabling that sticks up from the top of the controller board.

On top of that is a simple plate to act as the platform for the hammer. This is 1/8"-thick 6061 aluminium, just because we happen to have some (we think) and we'll cut and drill it ourselves, versus getting it waterjetted.

On to the platform we'll mount a couple of bearings from McMaster, good for a half-inch shaft - we can use a piece of the keyed shaft that's already on order for the fifth featherweight drive axle. We also have a couple of shaft collars in there to lock the weapon shaft into place.

There's the shaft, and there's also a 14-tooth #25 sprocket, which will be hooked to the largest servo we ordered a week or two ago, which will be doing the actuation. We're going to write a simple set of moves in the PoMoCo script for Hexy for up, down-front, and down-back.

Couple of things here - firstly the platform has been trimmed, because we don't need those corners sticking out. Secondly we have a piece of 1" 6061 bar, which has a half-inch hole drilled through it to sit on the weapon shaft, and will have the rear rounded off, and a couple of set screws put in to fix it to the axle. In the front of the block there's a 1/2"-13 threaded hole drilled and tapped, into which is the long dark grey cylinder, representing a length of grade 8 threaded rod.

Here's the business end - another drilled and tapped 6061 block with a length of grade 8 threaded rod in it, only this time the two ends have been ground to points. It's not going to hold up super-well, but at least it'll be cheap and quick to replace if it gets blunted. The actual lengths of the rods will have to be determined once the body has been put together, to ensure sufficient clearance. These weapon components weigh close to two pounds, so with the aluminium body we weighed last night, we've used four and three-quarters of our six pound allotment, with battery and electronics left to go. There may even be weight left over for armour ...

The first of our two Hobby King packages showed up today, featuring some electronics and motors - hurrah! The second package, with metal gear servos for the Hexy kit is looking like it might show up by Friday - fingers crossed! We also put in an order at Pololu for an Arduino Uno Starter Kit, as we will need something to take a PWM signal from the receiver on the walker and turn that into something the servo controller board can work with. We were also notified by our friend up in the frozen wastes of Canada that our custom wheels had shipped with speed controllers and power switches - Wheee! Hit Back after viewing an image.

First, half a dozen speed controllers. Five are destined for our featherweight Intrusive Interloper 3.0 to control the motors we mounted yesterday. The other is for the drumbot Nihilistic Naysayer 2.5, just in case we blew one up at Franklin trying to run a siezed wheel-motor. We still need to check whether it's operational or not.

The rest of the box contents are three replacement motors for the drumbot. We've cunningly decided that we're going to skip the urethane molding, as Kurtis over at FingerTech Robotics has done that for us, creating a 2.5" outer diameter 45A wheel, with an inner diameter of 1.25". Guess what the outer diameter of this motor is? Yup - a touch under 1.25", so we're going to mount this motor inside the wheel, and try running it directly, once we've programmed the speed controllers to run as hot as we can get them to.

We've also been thinking about the walker. The basic plan is going to be to install the metal gear servos into the plastic kit as soon as they show up - multiple people on the Arcbotics Hexy Forum have stated these are drop-in replacements. Then we're going to weigh down the kit with enough stuff to make it weigh six pounds, and then we're going to see if it can move. Truthfully, it may not, because these servos have the same torque as the plastic-geared ones, and we guestimated we would need twice as much, but we're going to try anyway. The reason is that if these servos can move the 'bot, we don't have to redesign any of the parts - we can simply have the existing design cut out of aluminium. If the servos can't handle it, we'll have to scramble and get the original servos we were planning on switching to, and redesign around them.

As far as controlling the walker goes, we've decided against trying proportional speed when making the 'bot move - it's going to be an all-or-nothing approach: depending on where the transmitter stick is located, the 'bot will perform one action continuously until the Arduino board receives PWM pulses indicating the transmitter stick is in a different location. For example:

The right stick will tell the 'bot either: move forward; move backward; turn to the left; or turn to the right - but only one operation at a time. The left stick controls the hammer using the rudder channel (left/right) swinging it either in front of the 'bot or behind the 'bot. The top of the throttle channel (up/down) is a special move, in that if the Arduino detects full throttle, it will ignore the right stick, and put the 'bot into "Defensive Mode" where the two front legs come together, to allow an impact, for example, to be received by the titanium plates on the front.

For kicks we might add the "Dance" move to one transmitter toggle switch, and the "Wave" move to the other toggle switch :-)

After researching on the Interwebz, there are basically two ways the Arduino board can read what a receiver is putting out: by using the PulseIn() method, or by using interrupts. The PulseIn() method is simpler to implement, but apparently wastes a lot of the compute time on the board. The interrupts are more complicated, but allow you to change the commands faster. Now, given that Hexy will only be doing one thing at a time (move forward, turn left, defend, etc.) we're thinking that PulseIn() ought to be fine. The basic command program will be something like:

Initialize the servo controllers
Initialize the servos (stand up)
Begin main routine
Loop {
   Check to see if Throttle channel pulse is > 2000µs {
      Position the servos for defensive posture
      Restart Loop
   }
   Check to see if Elevator channel is > 2000µs {
      Move the servos to move the 'bot forward a step
      Restart Loop
   }
   Check to see if Elevator channel is < 1000µs {
      Move the servos to move the 'bot backward a step
      Restart Loop
   }
   Check to see if Aileron channel is > 2000µs {
      Move the servos to turn the 'bot right a step
      Restart Loop
   }
   Check to see if Aileron channel is < 1000µs {
      Move the servos to turn the 'bot left a step
      Restart Loop
   }
}


Anyhow, that's enough rambling for now - not sure if we're building tonight, but stay tuned for more in the run-up to Motorama 2013!

We had fun with Intrusive Interloper 2.0 at NERC's Franklin Cup 2012, making it to the final against Tetanus, but failing to overcome that beast, ending up sitting forlorn in the arena, immobile. With that in mind, we wanted to beef up the drive train in this next version, preferably without spending $200 per wheel in motors and speed controllers. Hit Back after viewing an image.

We've decided to make the drive train modular, so that if needed we can swap in a complete wheel/motor/ESC set, plug in the ESC, and have it ready to roll. With that in mind, here is the frame for the drive pod, made from half-inch polycarbonate.

Here's where the oomph comes from: a G25 610kv brushless outrunner motor for $25. There's a 12-tooth gear pushed on to the 5mm shaft, which mates to a 56-tooth gear, giving a 4.666:1 reduction.

Here's the axle assembly: a half-inch shaft, with bushings on either end, and the wheel is a custom 40A durometer 2.5" FingerTech Robotics sumo wheel. We used 40A at the Franklin Cup, and while it was grippy, it did wear faster than the traditional 65A Colson tire, so we'll need to remember to pack a few spares.

Here's the drive pod assembly all together. The green block is a 60A reversible car brushless ESC, again about $25, so throwing in the gears, wheels, and polycarbonate, each drive pod is around $100 to build - much more reasonable than a DeWalt and a Victor 883!

The chassis for Intrusive Interloper 3.0 is a slightly modified version of the previous one. The frame is entirely 3/4" 6061 aluminium, with a 3/8" thick front wedge. The top and bottom plates are 0.071" titanium. Excluding the wedge, the chassis is 14" wide, 12.25" long, and 2" tall.

Here's the chassis with four drive pods installed. The pods are designed to be installable in any place, and just switching a pair of wires from the ESC to motor to set the direction.

The top and bottom plates both have mounting holes for the chassis and all four drive pods. That means it takes 46 bolts to remove the top plate - that's a few too many to be able to get the battery out for charging, so we're cutting a battery access panel into the top plate - three bolts is much more reasonable!

The battery is a 4S 3Ah lithium polymer pack, and should provide sufficient current by itself to power all four motors. On the other side of the polycarbonate stand is where the power switch, receiver, and gyro go.

Here we have all the internal components in place. There is a quarter-inch between the left and right drive pods, to allow for the ESC power and PWM signal wires to make it out to the middle of the 'bot. Although we haven't factored in the weight of the hundred or so bolts there will be in this 'bot, we're not worried about weight:

Here's the obligatory "Team Colours" render - note the purple wheels - we've about talked Kurtis over at FingerTech to do a custom colour for us ;-)

Back at Motorama 2012 we debuted a new fairyweight, Trancendental Terror 1.0, with a titanium spinning blade attached directly to the motor driving it. It was a decent design, but it had one fatal flaw - it wasn't invertible, and lost two out of three matches by being flipped. We decided to see if we could tweak the design to make it invertible. Hit Back after viewing an image.

Here's where we started, by sketching to try and lay out the components. This was our third attempt, and happy with it we decided to switch to CAD and see if it would make weight.

The baseplate went through a few iterations as we trimmed more and more weight off the design aiming for that magical 150 gram mark. The baseplate is 0.03" titanium, waterjet-cut, along with the plates for our antweight.

The chassis walls were originally designed to be 1/8"-thick polycarbonate pieces - we didn't want to do the one-piece chassis block like last time because it was awkward to work with. Just to give a sense of scale, the chassis is roughly three inches across.

One thing we're keeping from the first version is bolting through the 'bot to keep it together. These are 7/8"-long #0-80 screws and nuts. Note the notch in the front wall for the weapon motor wires.

With the baseplate on, we've also mounted the Pololu 30:1 HP drive motors, which will have 1.5" Lite Flite wheels attached for the drive train. We know from our antweight these will be more than enough to make the 'bot mobile.

The weapon motor and blade combo are transplanted directly from the first version, but sit parallel to the base of the 'bot, rather than angled, and the whole 'bot will be angled anyhow, due to the size of the drive wheels.

Next we need to pack the electronics in the 'bot. The green boxes at the back approximate the FingerTech TinyESCs we'll be using; the large blue box is a 3S 180mAh LiPo battery pack; the transparent orange is the OrangeRx receiver; and finally under that is a 10A brushless motor controller for the weapon motor. Not shown is a BotBitz power switch which will be mounted over the two drive ESCs.

And here's the 'bot all bolted up. The hole in the top plate is simply because we didn't want to design different top and bottom plates - this way we can have three identical ones cut, and use them interchangeably. The 'bot actually rides on the front lip of the baseplate, and if it ends up flipped, it'll ride on the same point on the top panel.

As we're bolting through the walls, they don't need to be able to hold a thread, and so we could switch the polycarbonate for UHMW, which would save a few grams of weight, plus it comes in black, so we'll paint the top and bottom in Team Radicus purple.

Adding it all up, we have a few grams free, but this doesn't include the four bolts for the weapon motor and six bolts for the body, but then again this also shows polycarbonate walls, not UHMW, so we're thinking that all-in-all we can safely make weight.

Malicious Mule did really well in Lauren's hands at Motorama 2012, and really poorly in Toni's hands at Franklin Cup 2012. The next competition for us will be Motorama 2013, so we're going to tweak the antweight's design one more time to try and work out the issues we've had at the two events. Hit Back after viewing an image.

One thing that's been rock solid in both competitions is the choice of quarter-inch thick 6061 aluminium, which is pretty heavy duty in the one-pound antweight world, so we're going to stay with that basic chassis. No inner rails this time though.

The top and bottom plates are eighth-inch thick polycarbonate, and inside you'll see four pairs of 1/4" thick polycarbonate mounts for the drive motors.

In the ant's first competition we had old, slow-and-torquey 50:1 Copal motors - the 'bot could push most opponents, but was very lethargic speed-wise. In the second event we switched to Pololu HP 10:1 gearmotors, and while the 'bot was very quick, it barely had enough torque to move itself, let alone push an opponent. We've decided to take the middle ground, and go with Pololu HP 30:1 gearmotors, the same we use in Poor Punctuation 2.0 and Transcendental Terror 1.0, as they have a good balance of speed and push. Rather than mess with aluminium spacers for axles we're going to try out FingerTech's Lite Hubs mated to 1.5" Lite Flite wheels, the same as we used in the first version of the 'bot. The motors press-fit into the motor mounts, and ought to be fairly sturdy. Not using a bearing for the other end of the axle will hopefully mean less friction, and better performance.

The light blue box is the receiver, the two darker blue boxes are a pair of 260mAh 2S LiPo batteries that will be run in series to provide 18.8V to the drive motors. The black box in the back of the 'bot is a gyro - we still want an ant with a gyro in it! :-) The little clear box at the front of the 'bot is a BotBitz power switch.

This is what the 18.8 volts gets us - almost 14 miles per hour! That's why we want the gyro. We know from using the 30:1 motors before that they generate enough torque to push an antweight opponent, so we ought to have a good mix of speed and torque this time around.

Here's the 'bot all buttoned up. There's an access hole in the top panel to get to the battery connectors for charging, otherwise we'd have to take 28 #4-40 x 0.25" screws out every time we wanted to get to the battery. Seems par for the course in our smaller 'bots! Truthfully we may not need to bolt the motor mounts to both the top and the bottom panels, but it seems like if we have the weight it's the thing to do.

Speaking of weight, we're cutting it a bit close - there's a bit under an ounce left, and we haven't totted up all the screws yet, so there may be a touch of pocketing of the side rails being done as the 'bot comes together ...

And of course a paint job, including our attempt within Rhino3D to emulate the stickers that will be made for the 'bot. All in all it should be one solid little 'bot!

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!

In trying to redesign Poor Punctuation 2.0 to make it sturdier we were having terrible weight issues, so we wiped the slate clean, and doodled for a while. After a short while, we'd come up with this antweight design, and we've decided to build it for Franklin. Hit Back after viewing an image.

The chasiss is a blend of 6061 aluminium (front and rear walls) and polycarbonate drive walls and top/bottom. We went with aluminium in order to try and put some rigidity into the chassis.

The outer rails are 1/4" UHMW, slotted for the aluminium walls, again to try and increase the stability of the frame.

This is a two-wheeled drive train, with Pololu HP 30:1 motors, TinyESCs, and 1" foam wheels, just like we used in Poor Punctuation 2.0.

And here's the business end of the 'bot - a 5" length of 1.5" diameter UHMW tube, with 1/4" steel teeth milled into it. We will use #6 bolts going through one tooth and threaded/Loctited into the other tooth to keep both teeth in place.

What's going to make this interesting is that powering the drum are two of the 2204-14T motors we used in Poor Punctuation 2.0, bolted to the side walls, and then the set-screws that act as the retainer for the prop saver will be removed, and those holes will be bolted into from the outside to secure the pipe to the motors.

In order to provide the juice to the pair of weapon motors we need a freakishly large battery - the blue brick is a 1000mAh 2S 25C LiPo pack running to the two TinyESCs and two reversible weapon ESCs. The orange box is the receiver, and there's even a little bit of space left inside!

When Persistent Pugilist 0.9 comes out swinging at NERC's Franklin Cup, needless to say it'll be in team colours, and fingers crossed survives the first hit ...

We were really excited by our last beetleweight design but then we got to thinking about the fact we're going to be flying to the NERC Franklin Cup competition, and trying to get a 36" blade in a case would be a challenge. Reluctantly we put Lincoln Limboer 0.9 on the back-burner and set about designing a beetle that would be more flight-friendly. Hit Back after viewing an image.

Here's the basic chassis. The front and rear walls are 1/4" 6061 aluminium; the inner walls and top/bottom panels are polycarbonate. The two inner walls at the front of the render are for the weapon motors, and the two at the back are for the drive motors.

The outer side walls are 1/2" UHMW plastic, waterjet-cut, and milled for the front and rear walls to slot in. We're thinking - if we have weight - of putting a couple of titanium splints on the outside, where the front weapon mount points stick out from the 'bot, but we'll see how sturdy things seem once the 'bot it assembled.

The drive train is unremarkable - 1000rpm gearmotors from Kitbots controlled by two FingerTech TinyESCs, and 2" solid rubber wheels. It won't be the fastest 'bot on the block, but hopefully simplicity translates into reliability.

The weapon is a steel beater, waterjet-cut from a 2.5" wide x 0.5" thick piece of chromoly steel, then milled down to a quarter-inch thich on the outside, and a 5/16" diameter steel shaft welded to the beater (or vice versa, depending on how you want to look at it). The beater is powered by a pair of 2836-11T brushless motors. These motors get 750 rpm per volt, so running at 3S, or 11.1V, the motors will get up to 8,325 rpm. The transmission is a 16-tooth MXL pulley on the motor linked to a 30-tooth MXL pulley on the beater shaft, for an effective reduction of 1:1.875, so the final beater output could theoretically be in the region of 4,000rpm. We're running the motors off reversible ESCs, so if the 'bot is flipped we can run the beater the other way.

Add into the chassis a decent-sized Lithium Polymer battery, OrangeRx 4-channel receiver, and a Whyachi MS-05 switch and you have the gist of things for this 'bot, which we're going to name Belligerent Battler 0.9.

Finally some team colours - the UHMW is black, so we'll paint the front and rear walls black too, and the top and bottom will be purple. We're also going to have to add a mark to the top and bottom so we know which way the throttle is supposed to be for that orientation!

Lauren did really well with her first ever 'bot at her first ever competition, going 3-2 with Malicious Mule [But we're not bitter - Ed.] The one flaw was a lack of speed, as those 50:1 Copals, while having plenty of pushing power were geared very low - we only used them because we had them handy. As an upgrade, we're putting very fast motors into this redesigned antweight, and tweaking a few things around them. Hit Back after viewing an image.

The chassis of the first version was made from 1/4"-thick 6061 aluminium, and came away from the competition with barely a scratch on it, so there's no particular reason to change that part of the design.

A small change for version two will be the use of polycarbonate for the inner walls, rather than more 6061, to save a little weight. We're also going to switch from a UHMW top and bottom to polycarbonate, and it will be fitted, rather than just 'sitting' on top.

The drive motors will be Pololu HP 10:1 gearmotors, with 1/4" aluminium axles mating with 1.25" diameter rubber wheels, rather than the foam ones we had previously. Depending on time, weight, and inclination, we may try making wheels with the 40A durometer urethane we're playing with.

Not an intuitive render, but here's a quick run-down of the electronics in the 'bot: the white block is a BotBitz power switch, the dark blue box is the 300mAh battery, the light blue box is the receiver, the red box is a V-tail mixer, and the coup de grace is the pink box - a gyro! Yup, this ant is going to be a fast sucker, and we're going to do everything we can to make it as driveable as possible.

As you can see from the Tentacle Torque calculator, these motors at just 7.4V (2S) are going to get the top speed up to over 13 miles per hour! Hence the gyro ... although truthfully, how fast it'll top out in an eight-foot arena remains to be seen, but still - pretty zippy!

Weight-wise we're doing well - 92% of our one pound allotment has been used up, with just bolts to account for, so we're fine here.

We're not sure whether we'll be taking this 'bot to the Franklin Cup or Motorama first, but it should be a quick build, so plenty of time to practice driving it.

And of course plenty of time to paint it :-)

Ever since the dismal failure of our featherweight Formidable Fustigator 2.0 we've put large blades on the backburner and focused our efforts on simpler, more robust 'bots, but this design crept up on us over the weekend - Lincoln Limboer 0.9! The name is a portmanteau-ish reference to two other large-bladed 'bots: Greenwave (think Lincoln Green) and Limbo. This design is for the three-pound beetleweight class, and is actually quite simple. Hit Back after viewing an image.

We tried a number of base chassis designs, but they ended up being pretty hefty in the weight department, and with only three pounds to work with, we had to keep it lean. This is our final[ish] design, with a 1/8"-thick piece of 6061 aluminium as the base, and four Pololu HP 30:1 motors on 1" wheels.

A 2" outer diamter, 1" inner diameter piece of 6061 pipe is our central dead shaft. The bronze things are thrust bearings, and the pipe bolts to the baseplate with four 1/4"-20 bolts. The hollow core to the shaft is to allow power leads to run out to the drive motors from the two TinyESCs running the drive.

This is the weapon setup with the upper bronze thrust bearing removed for clarity. That's a 3542 brushless motor powering the blade, which is a piece of 0.071" titanium. Bolted to it is a 78-tooth XL timing pulley, which connects to the 19-tooth pulley on the drive motor with a 100-tooth belt. The blade weighs a little over half a pound, so we think that this 40A motor ought to be able to get it up and running without cogging.

Here is the electronics platform bolted to the top of the dead shaft. LiFePO4 batteries in blue, power switch in white, weapon ESC in red, and the receiver and drive ESCs are not shown. The platform is 1/8" polycarbonate.

We selected Pololu 30:1 HP gearmotors for this 'bot, because our original plan of using the copious 50:1 Copals we have sitting around would have meant a 1mph 'bot, which isn't all that interesting. As you can see from the Tentacle Torque Calculator below we're going to run the whole setup at 13.2V, or 4S in LiFePO4 terms.

This is the worrying aspect of the design - how close we are on weight! Truthfully we guessed at the weight of the two polycabonate pulleys and the belt, so hopefully we've over-estimated. The only place we can save weight is by switching the baseplate from 6061 aluminium to polycarbonate, but that'll be a last resort move!

Here you can see the final effect - that's a 36" titanium blade, and the base is roughly 12" by 12" - it remains to be seen whether that's sufficient footprint for the 'bot to remain stable with that blade running at roughly 1500 rpm.

And lastly some team colours. This is the first asymmetric 'bot we've ever designed (with the weapon motor off to one side, but hopefully we've counter-balanced the weight okay with the batteries diagonally opposite. Win or lose, if that blade spins up, it'll be a treat to see! :-)

A few weeks ago, the first ever Kickstarter project we backed was successfully (over-)funded, and we're now waiting in anticipation of a Hexy the Hexapod kit. It comes with an acrylic chassis, eighteen metal-geared servos, and a controller on board. After thinking a while on the specs of the kit (18" across, 5" tall, weighs a bit over two pounds), we began to realize that we ought to be able to convert this kit into a Beetle!

As a walker, we'll be allowed six pounds to work with, so assuming the density of acrylic to be roughly a third that of aluminium, and guessing that a third of the kit is the chassis, an all-aluminium chassis would be about two pounds.

There are eighteen servos onboard, each one weighing 13 grams, or about half an ounce, for a total of nine ounces of servos. These servos evidently produce 2.2kg/cm of torque, and they can ably move the kit (2.2lb) plus an additional 0.8lb, i.e. these servos can move 3lb. In order to move a six pound 'bot we would need to find servos that are capable of producing 4.4kg/cm of torque, something like these, although they'll be a pricey upgrade.

Finally, we'll drop the head sensor from the 'bot, and mount an over-head hammer on the top plate, in the style of Mangi:

The 'bot may get chewed up and spat out in it's first match, but it's going to be fun learning how to interface a receiver with the Arduino-based controller, and it'll be a good learning step on the way to building a 60-pound walker Sportsman for the following year!

We were fairly pleased with how the UHMW drum on Nihilistic Naysayer 2.0 held up at Motorama 2012, but the drum shaft was an issue, and the drive train was pretty poor, so with these two issues to fix in mind, we went back to the drawing board, and set about redesigning the hobbyweight. The shaft ought to be an easy fix, but how to make a simple, yet robust, drive train? Hmm ... To Hit Back after viewing an image.

First upgrade is the side rails, going from 3/8" 6061 aluminium to a full half-inch. Otherwise the shape is roughly the same, although we did make sure to make them interchangeable, so we can have three waterjetted, and the third can be swapped in for either side.

The rear wall is a piece of 1/4"-thick 6061 pipe that we already have handy, although it will need to be trimmed down, as the rear of the 'bot is shorter than the front section, which is the same height as the current version. The center wall is half-inch polycarbonate and the front wall is quarter-inch 6061 - when our drum came off in the first match at Motorama, it hit the polycarb wall we had in version 2.0 and shattered it, so an aluminium wall ought to hold up better. And no holes this time, just a solid piece.

We started with eighth-inch polycarbonate top and bottom panels, but towards the end of the redesign we realized we could afford to go with 6061, so we'll do that. The dividing wall and weapon motor mount are reused from the current 'bot.

So here's what we're thinking for the drive train: take two Turnigy G32 600kv Brushless Outrunner motors, which have an outer diameter of 42mm (1.65") and cast some 40A durometer urethane onto the can, for a final diameter of two inches. Then mount the motors directly to the drive walls, add a bearing for the shaft on the other end, and hook them up to a pair of Turnigy 60A Reversible Brushless speed controllers.

If the kv of a motor (number of revolutions per volt) is 600, the torque (in inch-ounces per amp) is equal to 1352/600, or roughly 2.25in-oz/A. We know from the product page, that the max amperage is 60A, and because we want to take this 'bot to NERC's Franklin Institute, we need to use Lithium Iron Phosphate batteries instead of Lithium Polymer, which have a voltage of 3.3V per cell, so let's say a 4S pack, or 13.2V. With these numbers, we can head over to the Torque Calculator and see where we're at. Big thanks to Gene Burbeck for guiding us through the drive train math!

We set the weight of the 'bot to eight pounds, because most of the weight of the drum will actually be resting on the front skids. The torque required to spin the wheels is less than half the maximum amperage, so in theory the 'bot ought to move. Note the insane top speed of 47mph - there's no way we can drive a 'bot that fast, so we're going to set the maximum rate on the radio to 25% of normal. This will cause the ESC and motor to work harder than simply 100%, but a 12mph 'bot is significantly easier to control than a 'bot at four times that speed! The caculator says we need just over 50 amps peak, and the LiFePO4 batteries have a constant current output of a little over 60A, so that's fine. The only issue really is that the Amp-Hours needed is quite high for a three minute match. LiFePO4 batteries come in 2.1Ah versions, so we're going to go with one of those in the design.

The weapon motor and transmission are transplanted straight from the current 'bot, as it seems to work well, but we will be making a new drum shaft, as it needs to be a bit longer to sit in the pockets in the half-inch outer rails.

This is the majority of the internal components - the blue brick is the LiFePO4 battery, the green blocks are drive ESCs, the red block is the weapon ESC, and we've mounted the Whyachi MS05 power switch to the center wall.

After tallying everything up, we've figured we can definitely switch the top and bottom plates to 6061 aluminium, so here we are!

Except with team colours applied, of course! And yes, thanks to Jason Ribeiro for the information on casting urethane, which means we can have purple wheels ;-)

We've pretty much spent the weekend on the couch, knocking back Alka Seltzer Cold and Flu, suffering from the "Motorama Plague" or "Motorama Flu", as it's diversely known. Heck, we haven't even unloaded the 'BotMobile yet, but sitting here with not much to do except avoid infecting other people has meant idle hands - hands which decided to do some CAD work! After thinking about our last two failed attempts to build a weaponed 'bot in the thirty pound weight category, and thinking about all the huge weapons that were in the weight class at Motorama last weekend, we've dusted off an old 'bot design we used to have fun with and decided it was due a revision. Hit Back after viewing an image.

In the first version of Intrusive Interloper we had a three-quarter inch thick rear wall, and half-inch think sides and front angle. Given the damage we've seen dished out at the last couple of Motoramas, that may not be sufficient these days. We initially wanted one inch 6061 on all four sides, but didn't have the weight, so we're going with 2.5" tall by 0.75" thick 6061 aluminium on the rear and sides, then a half-inch thick front wall.

Attached to the half-inch thick front wall is some three-eighths thick 6061 aluminium angle. The bolts are threaded into the angle, pass through slots in the front wall so the height is adjustable, and then we'll use grade 8 washers and lock-nuts to secure the wedge. Fingers crossed that's enough to hold it! The inner walls are 2" tall by 0.5" 6061 aluminium.

Here's the drive train: four 18V DeWalt gearmotors to 3" Colson wheels. In the previous version we had our two "Mini-Walts" but those are currently in use in Steel Stiletto, so we'll re-use the DeWalts from the defunct Formidable Fustigator 2.0 and one of our spares. Not shown are the strengthener kits for the DeWalts which will be installed.

Because we want to take this 'bot to NERC's Franklin Institute competition this year, we can't use Lithium Polymer batteries, so instead we have Lithium Iron Phosphate. These batteries have a slightly different cell voltage than LiPo (3.3V/cell instead of 4.7V) so we'll use two 2.1Ah 3S packs in series to give the DeWalts 19.8 volts of power. The 2.1Ah capacity should just be sufficient for a rumble. The two red bricks are hacked TZ85A brushless speed controllers converted to run brushed motors. The white block is the MS1 power switch, and the purple block is a Hobby King HK401B gyro, which we want to try out, and see if it helps our driving.

Here we have the chassis assembled, and the quarter-inch thick top and bottom plates have been installed. The 'bot was designed so the top and bottom plates are simply 12"x12" to make fabrication nice and easy, and depending on weight, they'll either be polycarbonate or UHMW.

Here's a final render of the 'bot with team colours applied. We have the motors and un-hacked speed controllers for this 'bot, and that's about it right now, so we'll be placing an order for some extra parts like wheels, chassis components, and batteries, once we've had a think about other 'bots for the Franklin Institute competition and see whether we need other components for those.

According to the Killerbotics/Tentacle Torque Calculator we ought to have plenty of oomph from those four DeWalts:

And with judiciously applied pocketing to the chassis parts we ought to just squeak in underweight - completely different than version one, which used to run around 23lb fully loaded:

Okay - this is way too cool! Jerome Miles suggested we take a look at CamBam, which is a tool that takes a CAD drawing and allows you to specify what you want to do to the part with the mill, then it automatically generates the G-Code for you! How neat is that??

We created a DXF of the chassis base for the new fairyweight, imported it into CamBam+, told it we wanted three pockets 3/8" deep, and it spat this out:

And it gave us a text file with the G-Code for it!

( Made using CamBam - http://www.cambam.co.uk )
( FW2 Bottom.dxf 1/19/2012 10:30:14 PM )
( T0 : 0.1875 )
G20 G90 G64 G40
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( T0 : 0.1875 )
T0 M6
( Pocket1 )
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M5
M30

How cool is that?! Can't wait to try this out!!

We spent some time sizing up the fairyweight (150g) opponents for Motorama 2012, and decided that a simple lifter wasn't going to cut it, so we needed something more offensive.Hit Back after viewing an image.

We decided to go with a weaponed 'bot, using as many components as we already had available, so drive motors and TinyESCs, a battery, receiver, and 1.5" tires, and we're already at 81 grams out of 150g allowed in this weight class.

One of the nice things about both fairyweights and antweights is that you can usually sketch a design at 1:1 size. Here we're planning a layout for the components.

Plus said components overlaid on the design. It's a bit messy, but you get the general idea. The wires will all need trimming, etc., and we need to hit the CAD program to find out how much a chassis will weigh to accomodate all these parts.

To try and make things both neater and easier, we taped together the 350mAh 2S LiPo battery and the receiver. Together they make a ni 2" by 1.25" block.

This was our first attempt at a chassis design, but unfortunately came out too heavy, even using UHMW rather than polycarbonate, so we had to rething the layout a bit.

Rather than put the motors outside the battery, how about if we put them behind the battery? There's space on top of the motors for the weapon ESC, and space in front of the motors for the drive ESCs.

This is the top half of the chassis, with pockets for the internal components, and a slope on the front where the weapon motor will be mounted.

And here's the bottom half of the chassis - the hole in the front is simply to save weight. The two halves of the chassis will be bolted together with 1"-long #0-80 screws and nuts.

The weapon motor is a 2204-14T brushless outrunner, the same as we're using in Poor Punctuation 2.0, and the 0.071"-thick titanium blade will be super-glued/expoxied to the outside of the can, again just like we've done in the antweight. The red brick is the 10 gram ESC for the motor.

With the 'bot all assembled, it hopefully will be a fairly tough competitor! Although it has a touch of Little Rat about it - we hope the wheels stay on ...

And of course, some team colours. Although we may end up reversing this, as the two chassis pieces will be milled from black UHMW, so we may just paint the blade and be done with it.

According to the Tentacle Torque Calculator it should be a zippy little thing:

Although weight is cutting it a bit close! There aren't many places we're going to be able to shave off weight, but we'll see what we can do ...

Oh - and I guess we need to come up with a name for this thing too ...

The last version of Formidable Fustigator had a huge design flaw: At pretty much exactly the same time the blade hit the opponent, the opponent was perfectly lined up to hit a wheel, and being polycarbonate it shattered. The two goals in this re-design were to (1) Re-use as many components as possible; and (2) try and keep the wheels away from the opponent! Hit Back after viewing an image.

To try and get an idea of how we need the layout to be, we took the CAD for version one and rotated the body to put the wheels as far away from the blade as possible. We worked with this for quite a while, before realizing that there was too much area to cover for the top and bottom plates, so we needed to re-jig a little.

We wanted to keep the three-omniwheel design, but we were failing to stick with many elements of the previous design, so we laid out a new drive train and worked around that. This time the left and right wheels are perpendicular to the rear wheel, so top speed will actually be pretty quick.

Here's the basic chassis. We went back and forth on materials for a while, before coming up with a combination that would make weight. The top and bottom plates are quarter-inch polycarbonate; the front and angled walls are half-inch UHMW, and the three small walls covering the wheels are half-inch 6061 aluminium. On the weapon boom, the polycarb plates will be milled to an eighth-inch thick, and eighth-inch thick aluminium braces will be bolted on to help strengthen the boom.

The drive train is kept intact from the previous version in terms of components - DeWalt motors, omniwheels, and polycarb wheel mounts. We'll have to try and remember where we bought the omniwheels so we can get another one for a spare.

The electronics are pretty simple. Victor 883s for the drive motors, and a couple of 70A brushless ESCs (in red) for the weapon motors. The batteries are a pair of 3Ah 6S 40C Zippy LiPo packs in parallel, so they can offer up 240A in a pinch. Not shown here are the receiver, battery eliminator, and Whyachi power switch.

As far as the weapon goes, we have made a bot of a change here. Although the blade and pulley are the same, along with the nylon blade washers, we're switching the weapon motor, which used to be a G110 for two G60 motors. They'll have a bevel gear set for a 2.5:1 reduction, and then from that shaft a 16T pulley feeds the 32T pulley for the weapon shaft, so this should have an overall speed of 2200rpm.

You may note that the weapon boom isn't actually long enough for the blade to miss the front wall of the 'bot, so there's a slot milled into the front wall for it, and it just clears the internals. As long as the 'bot doesn't flex [fingers crossed] it should be just fine. We don't see what could possibly go wrong ...

Here's our weight spreadsheet, and without any wire or fasteners we have two pounds available. We could also pocket some of the UHMW walls, but that won't save a whole lot of weight, so if it comes to it we could drop a weapon motor and save a pound or so.

A screenshot from the Tentacle Torque Calculator showing that the DeWalts at 6S (22.2V) will run quite zippily on the omniwheels. It also figures that we'll use a quarter of our battery power for the drive, and the rest are available for the weapon, which should work out okay.

A final render, as we didn't have time to get some Team Colours slapped on the parts. We also left the batteries together on a single wall - it might mess up the weight distribution, but it means we can get the batteries out to charge by only removing ten screws, which would be handy. All in all this should be a fairly easy build, and we're looking forward to getting the parts waterjet-cut so we can get to assembling!

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 ...

At the last Motorama, Scott came to Harrisburg to hang out, and brought with him his wife and step-son. Turns out that Kyle was interested in the whole thing, and so a short while after the event, Scott asked me to design a simple 'bot he could work on with Kyle. Oh, and he had gotten his hands on a chunk of aluminium, and found someone who would be able to mill it out, so could I make a unibody-design 'bot? It took a while, but here's what I came up with. Hit Back after viewing an image.

The raw material: a 16" x 16" x 4" billet of aluminium. He'd better snag one for me too! This is a huge chunk of metal, and weighs almost one hundred pounds!

The first thing to do will be to cut it down to size. The block has been cut down to 12" x 12". Then sliced up to yield a 1/2" thick top plate, and 2.5" inch thick body. This is still 42 pounds of aluminium, so we'd better start hogging it out.

Here's the body after it's been milled out. I have no idea how long this would take to do. I just created a number of curves in Rhino3D, extruded them to solids, and BooleanDifference'd them out of the main block, assuming the radii of the cutting tool to be 1/4". There are a few virtual bolt holes in there too, but significantly less than usual!

Here's the top plate too. The two sets of nine holes are cooling holes for the drive ESCs, along with a hole to get at the power switch, and a hole for a power LED. Ten 1/4"-20 bolts hold the lid on.

The drive train is very simple, and very powerful! Two 18V DeWalt motors with Team Delta mounts and strengthening kits, 4"x1.5" Colson wheels, and some chain to hook them up. Because of the unibody construction, I had to cheat, and make polycarbonate bearings for the wheels and motors, otherwise we wouldn't be able to physically install the drive axles!

The electronics are very simple too. Two 3S 3Ah LiPo battery packs, that will be connected in series to give 22.2V to the DeWalts. Two Victor 883 drive ESCs to control the drive, a 40V Battery Eliminator, Receiver, and MS05 Power Switch.

Here are all the components inside the unibody. I'm quite proud of myself for remember to cut channels in the block for wiring - usually the wires are an after-thought when I'm designing a 'bot, but I had to make sure there was a way of routing everything for this 'bot.

Here we are all buttoned up. 28-ish pounds of 20mph indestructability! In theory, any way ...

Using the Tentacle Drive calculator, this should be a seriously fast, pushy 'bot, so the sooner Scott and Kyle get it built, the longer they'll have to LTFD it :-)

Without the weight of bolts, wire, chain, or sprockets, they still have almost two pounds available, so no worries there.

Having spent a bit of time contemplating the Sportsman idea, we need to spend a serious amount of time with Rhino3D to see if the design in our heads has even the slightest chance of being build-able. We've already started messing around with the legs, so here's some work on another part of the 'bot: the tail! Scorpions have a sting in their tail, and this 'bot - despite being Cyber - should do the same ... Hit Back after viewing an image.

Using what we learned last time we tried to design a hinged joint, we were pretty quickly able to throw together this structure for the tail. It's not entirely finished, as you can see there are parts that still project into each other, but that's because we want to mock up the joint in the garage Build Space and see what the easiest way is of limiting the range of motion of each joint to 30 degrees.

Here we've straightened out the tail and installed double-sprockets on the hinge axles. These are nylon 16-tooth #25 sprockets that will be bored to 'float' on the axles and are pinned together. The idea is to power the bottom (far-right) pair from a motor, and have the movement be transmitted to the end of the tail (bottom-left). Granted, there will be some losses, but this way we can allow the tail to articulate without having chain slopping everywhere.

Okay - here's the 'sting': a 12" SystiMatic Demolition blade! Long-time readers may remember that we used these on our very first 'bot ever, way back when. Whew! That brings back some memories!

As far as the articulation goes, to make the tail bend, we will run some thin steel cable from a fixed point at the sting-end of the tail through eyelets mounted on the underside, all the way back to the base of the tail, where the cable will be wound by a drill motor. The easiest thing to do here is to leave the clutch on the drill motor, so that when the cable is fully tightened and the tail is fully arched, the drill will simply slip the clutch. To straighten the tail, there will be springs mounted to the upper-side of each segment, so as the drill unspools the cable, the springs contract, pulling the tail straight. Well ... that's the theory anyhow.

Finally for now, a quick render with the legs and the tail together. Well ... I say quick - it took my machine eight minutes to produce this render! And no guarantees that this will be the final layout - we haven't even started calculating how much just the pieces you see here weigh ... there is a slight possibility that this is an impossible task, even with the 100% weight bonus for a walker, but it's definitely worth investigating ...

As we continue to unpack from the last Motorama, we're checking out the remains of the 'bots we took, and looking to see what's salvageable and what needs to be reworked. Tonight it's the turn of the beetleweight we took: Didactic Duelist 1.0. Hit Back after viewing an image.

There were some obvious wounds, courtesy of Jim Iocca's Mr. Croup. The sides are cracked and bent, and obviously it's missing a weapon disk that came off in a match.

Close-up of the back-left corner. A multitude of things wrong here, including the weapon motor pulley came off, and the drive motor fell off the gearbox! And the general mess inside there, presumably from the floor of the arena.

On the other hand, having powered up the 'bot, you can see the orange receiver light and two green drive ESC lights, so the electronics are good - we were able to run the drive and weapon motors just fine, so that's a plus. It seems what we need at this point is a fresh chassis to put the pieces back into.

Starting with the frame, and we need to keep the dimensions the same as the first version, because we want to be able to re-use the titanium plates we had cut. Instead of 100% polycarbonate, the outer side walls and rear wall will be 1/4" 6061 aluminium.

Adding the 1/8" polycarbonate baseplate and the 1000rpm Hobby Motors for drive, with the aluminium axle 'enhancers'. Note there's no center wall this time around.

We've moved the motors closer to the rear wall than they were in the first version to the BaneBots ESCs (red boxes) need to sit in front of the motors rather than behind. The wheels are going from 1.5" diameter to 1.75" diameter, and with that they protrude past the back wall and top plate, so hopefully we'll be a little more invertable.

The rest of the components are the same: battery, receiver, weapon motor and ESC, and powerswitch. This time, though, we're putting the pulley on the end of the weapon shaft, as the teeth will be welded on this time.

And there you have it! Albeit without the purple paint on the titanium front plate. At present we're estimating a whole three ounces available for wiring and screws, so we may make a couple of posts for the top panel to truly make it invertible.