Archive for the 'Chuckranoplan' Category

 

All Good (And Poorly-Maintained) Things Must Come To An End: The Great Project Purge of 2012

Jun 26, 2012 in Chuckranoplan, Cold Arbor, Nuclear Kitten 5, Project Build Reports, RazEr rEVolution, Test Bot 4.5 SP1

i swear to god i will fix this later

At some point, I need to stop telling myself that. It’s well known that my stuff isn’t exactly world-class in terms of reliability and Six Sigma class in quality, but even I can get sick enough of it to declare it a loss and start over. Over the past few months (and years) of neglect, quite a few of the robots and silly vehicles have become damaged and non-operational. I kept Swearing That I’ll Fix It Soon, Guys, but my shelf of stuff is long past overflowing with parts and project detritus and some of them contain good parts that I don’t want to keep buying. With my general shift of operations towards the newly opened IDC space just up the Z-axis from MITERS, tearing down some of the old derelicts and returning their parts to the Earth (/my storage bins) became more appealing – especially as I started collecting more stuff, most of it landing on my fresh new corner desk.

So it is with great sadness (and hidden catharsis) that I must announce the decomissioning of…

Cold Arbor

Cold Arbor never really worked – the frame was too flexible to accommodate the huge teeth of the saw. After Motorama 2010 and Dragon*Con’s Robot Battles ’10, CA pretty much only ventured off my shelf for the occasional demo – it illustrated, visually, what a “combat robot” was very well. Pretty much everyone’s first reaction at the word “Battlebot” is “You should put a saw on it to cut through the other robot!”, and CA is…. well, pretty much a saw. It never really stopped driving, but then the saw actuator broke so it couldn’t do the extending thing any more. Arbor, being the biggest lead weight I had on my shelf, was therefore the first to go.

But before I tore it totally down, I decided to use it still-functional and very smooth drive base as a test dummy.

Last year in the Austrailian robot fighting circle (did you know that Australia has a very active robot combat scene too?), one of the builders began to modify Hobbyking brushless controllers to act as H-bridges for DC drive motors, utilizing 2 of the 3 half-bridges available on the average BLDC controller. I’ve been advocating something like this for a while – use the cheap hardware base that is Chinese brushless motor controllers instead of custom-developing an expensive niche robot controller solution. The choices in robot controllers these days are either said niche and expensive but generally reliable controllers, or these one-tiny-FET-per-leg overfeatured doodads that I’ve literally had zero success rate with. Or you straight build your own and have them work, but I’ve also not successfully managed that yet. There’s nothing on the market right now which is just a bucket of large FETs like the old Victor 883s (which you can still buy, but they’re now a design so old it can almost drive).

That aside, I have also never bothered to schematic-trace the brushless ESC boards or learn & put up with enough raw Atmel C to reflash the microcontrollers (though I suppose I could have flashed Arduino onto them…). So, a ton of hot air rage on my end, but lots of action in the 40+page thread over on the Robowars forum, which has seen all of the cheap common ESCs reverse engineered and firmware implemented for – up to and including its own confusing beepy configuration menu.

They’ve now started selling them (when I say ‘they’, I really mean like one dude), and I took the chance to get some modified “85A” units based off this Hobbyking ESC.

First, I had to remove most of Arbor’s existing electronics. Okay, so my success rate with the Sabertooth controllers isn’t zero – Arbor runs two of the closely related SyRen controllers, but $75 for 25 amps is stupid these days, and I’m also royally undersizing their loads – one is running a little Speed 400 class motor and the other is running a drill type 550 motor which sees about a 10% duty cycle on raising and lowering the saw.

Way cleaner wiring and layout with the ESCheap85 in – I could easily see a robot with a whole rack of these next to eachother. The massive spam of SMT FETs technique used to great success by cheap Chinese controllers is an acceptable compromise, in  my opinion, between one-tiny-SMT-FET per leg used by the Sabertooth and Roboclaw and other most-likely-designed-by-newly-graduated-college-students controllers, and the one-huge-nice-FET approach I usually take. It keeps the board size down, too.

After hooking this up, Arbor was taken on several somewhat strenuous (and absurd) test drives.

None of it was very scientific, nor was there really enough space to seriously stress the bot out. I’m going to have to use these in battle myself before I’m fully sold on the idea, but based on the reports of the substantial number of Australian users, they’re pretty bulletproof, and a few American users have already run 18v DeWalt drills in drivetrains using them (the same motors that Clocker uses). The 85A type has been praised as a “Victor replacement”, but its more limited voltage range (30V fets and 35v capacitors) doesn’t quite convince me it can be swapped directly into a native 24v (up to 28v fully charged and more during dynamic braking) system. I fully agree with the concept, though, and for about $1 per amp I don’t have any complaints past my own reservations.

That doesn’t mean I’m no longer going to attempt my own controllers – I have yet to successfully execute a small current-controlled vehicle H-bridge, of which robot controller is a simpler subset. But that’s for another post.

At the end of it all, here’s Arbor mid-scrapping:

Scrapping is such a negative word. It took me a while to crack open that weapon drive gearbox, since I sealed it up so well at the start – and some of the bolts were bent.

Here’s everything I ended up keeping from Arbor. All of the motors, pretty much all of the drive mechanics (especially those delicious custom gearboxes, which were one of my first good ones), and of course the saw and worm drive in case I rebuild it all. The VictorHVs and Sabertooth controllers were also kept and filed in my robot controllers bin.

prospect for rebuilding: slim

Arbor was a very complicated robot with lots of moving parts – it’s something which is more difficult to get right, and it’s usually more disappointing (to watch as well as to operate) when it doesn’t work. Arbor’s build was rather rushed and many details weren’t completely thought out. I’m more likely to build a 30lb bot that is either more plainly functional or spend alot more time to build a complex but well-designed and tested robot before trying to compete with it.

Going down the line, next I pulled out…

nuclear kitten 5

NK5 was heavily damaged last Robot Battles, and ever since then has been sitting on the shelf. However, the disc motor still works great – and I can make spare discs, so that’s definitely being reused on something. The controllers and motors were also potential salvage items.

NK5 was the last robot I built before I converted fully over to “T-nut” style construction, visible in pretty much all my stuff from 2009 onwards. The design actually dates from late 2008 – my first major t-nutted endeavor was the ill-fated 2.007 robot. The frame has these wonderful corner bars that I machined for this application, but it seems like now you can buy everywhere. I really liked these, so I went ahead and saved them. Tapping into real metal is way better than t-nuts at any rate.

Here’s NK’s remnants pile. The frame materials were just not worth keeping, but I kept the motors – the gearboxes are not stripped, but one of the pinions fell off (but is intact). They might become donor parts for future gearboxes. I am a fan of these little 25mm metal gearboxen: while they are not planetary, they’re big and chunky inside to make up for it, and fairly cheap at $10-15 each.

prospect for rebuilding: hell yeah

I can’t guarantee when, but D*C 2012 is likely because I pretty much have everything-minus-frame. The disc is up for some revision, though. Big tall vertical disc spinners are no longer in vogue, being replaced by small, low bricky drum things with built-in motors (of which there are now like 50).

Next up is my pride and joy,

test bot 4.5 MCE

Really? The bot that made it to real-deal-Battlebots-IQ, then Motorama 2008 and back? The first thing I ever worked on at MITERS? Yep, since its default parking spot since Moto 2008 has been in Clocker’s lifter when it’s not doing other things.

TB certainly has the most grime of any of the bots, and the lifter was pretty much utterly trashed – it took a direct from the vertical disc bot Igoo at Motorama 2008 (that video is slightly painful to watch).

This is one of my first drill motor hacks. I did a few in 2006 for the original TB version 4, but they were either terrible or dismantled very quickly. This thing predates my entire website, pretty much. The extension shaft with the pinion was added when I redesigned the lifter for Moto 2008. It had an additional outboard support, but since it was made of UHMW, the whole gearbox still flexed too much to keep the gears in mesh, and so the pinion stripped very quickly in battle.

After I took the damaged arm parts off, I realized that TB’s drive base was actually in very good mechanical shape. I still love those gearboxes, too: they are super special 12:1 drill box hacks that I made with mating the salvaged 18 tooth planet gear and 9 tooth pinion gear of the first stage of a drill motor with an intact output stage. Coupled with the extremely overvolted 9.6v drill motors, this made the bot have a rather zippy top speed of 14mph. The first version of this gearbox predates the website (again) – this version at least had the luck of being milled, so things actually lined up!

I briefly entertained throwing the BotBitz ESCs in the frame just to drive it around again, but decided against it for the time being. It’s sure been a long time since I’ve had a 4WD drill-powered box.

So I closed it right back up again. Only the damaged arm and wedge parts were scrapped – otherwise, I think I can put something interesting in this bot again, or at least give it a better sendoff at a serious combat event later on, as the most honorable fate for a combat bot is still, in my opinion, being thoroughly vaporized into a cloud of small particles.

prospect for rebuilding: not for Robot Battles

TB4′s design was optimized for “arena” combat which has more guaranteed smooth floors and a more pressing need for huge, thick angled armor. The RB stage is purposefully left fallow to discourage pure wedges – a passive aggressive attempt at encouraging more robot creativity, which I contend has been successful in the past few years even though it kind of locks me out from competing in 12lbers again there with this design. Maybe Motorama 2013….

Finally, a project that I hate to see get tossed so early, but…

razer revolution

It’s lived a decadent life of being a demo attention whore as well as occasionally coming in handy when Melonscooter was on blocks, and has seen 4 different motor controllers (Double DEC’er, Melontroller, Tinytroller, and Jasontroller!), but recently RazEr Rev has become kind of a wreck.

I donated the front end to another MITERS scooter effort after the new battery got 2 dead cells after only a few weeks – definitely a case of bad initial conditions. Since then, it’s been sort of chilling in a corner, slowly being eroded away by the tides of cruft and dead power supplies that ebbs and floes around the shop.

The Jasontroller works great, the battery can be surgically corrected (I’m literally going to scalpel/X-acto knife the dead cells out and make it into a 10S pack), and the Dual Non-Interleaved Razermotor is a little rattly in the bearings but otherwise functional.

So that’s pretty much all I kept. Oh, and the extra heavy duty generation 2 Razor handlebar, after they moved away from welded-to-frame folding joint but before cost cutting made the joint like 24 gauge steel. This front hinge is massive – the steel is something like 0.13″ thick.

The reason I decided to scrap RREV now is because I’ve become dissatisfied with the frame design. It uses a design which I now consider inferior to other similar scooters in the way it’s put together. Starting over with the frame will be a great way to optimize the design towards less material use (like giant plates of 1/4″ aluminum) and make it simpler to assemble in addition to making dedicated space for the battery and Jasontroller, both of which were “aftermarket” additions. It should end up lighter for the same performance, but I don’t see it getting any smaller. Sorry Jamo, but Razor Wind is a little on the small side for my tastes now.

All this talk of what I’m gonna do means the

prospect for rebuilding: immediate

I already ordered some more giant aluminum plates (…sigh) and will probably be redesigning the frame this week. I’ve already got the changes planned out – they’ll just need execution. Like NK5, it will just be a matter of moving old parts over to a new chassis – there’s otherwise not much about RREV that I’m unhappy about. It’s definitely going to get a stock fender.

other stuff

I didn’t take any pictures, but all the Chuckranoplans have been parted out and recycled too. I’m probably not going to be touching this for a while until I stop being afraid of foam so I can build meaningful scale models. 3D printer models were fun for design practice, but are too heavy to work.

Alright, now that I’ve eaten half my offspring, I can start considering rebirthing them again!

Chuckranoplan 0004: So it begins

May 27, 2011 in Chuckranoplan, Project Build Reports

Hi, I built a hot-wire foam cutter.

I’ve been spending a little bit of time thinking about how I wanted to approach a hot wire cutter. There were several designs available – hand-held, portable (but large framed) like this, horizontal, and vertical, like what I ended up doing, and plenty of plans and advice from people who have built them were on the Internet. I was also playing around with a few different methods of keeping the wire tensioned. An initial tension set by an adjustable screw or something isn’t enough, since the wire relaxes when hot, so it needed to be some sort of spring loaded tensioner. And of course I was also investigating what materials I could make the structure out of – wood was easy and cheap, 80/20 was more legit and potentially lighter, and in either case MITERS had plenty lying around.

Then I was told I was acting too much like a grad student.

Enraged, I beasted the above product in 2 hours without thinking about it, and it works great. There’s just something about academia that makes you stop and think about things too much.

I could use a little (read: tons) more wire tension, since I bought 22 gauge Nichrome wire, which really should be under something like 50 pounds or more of tension here. A little extension spring provides maybe 10 pounds, but that’s enough to get good results if I cut slowly.

So what’s next after this?

I’ve been waiting for a foamcutting solution before I started on Chuckranoplan 0004, since it was going to be, you know, made of foam and all.  With the hot wire cutter done, I made templates that represented the body sections. They are to be glued to the ends of a piece of foam to act as a wire guide. The templates above are made from 1/8″ MDF (or some equivalent particleboard… it was found in a pile). The laser did a pretty good job on them, leaving a good clean edge finish, so I’ll probably keep using the stuff in the future.

There was plenty of pink foam scrap stored at MITERS, so I found some that still had square edges and trimmed the pieces square on the vertical bandsaw using a blade guide. I must say, foam kind of machines like really dense air.

 

…oh wait.

 

The trimmed pieces were bonded with some foam-safe CA glue I bought a while back, in the absence of the classic solution 3M 77 adhesive. I’ll need to run to a hardware store to get some of that later. They were then sanded slightly so the ends were squared up.

I then glued the templates on the end. This piece looks like it’s a little short to catch the tip of the V there, so that tells me I’ll need a stack of three in the future.

A few minutes of wiggling a chunk of foam around a hot wire later, he result is…

I NEED MORE PRACTICE.

Overall, I can’t say it turned out bad. In fact, it was much better than I had expected. As a confirmation of the general rule of thumb I seem to see everywhere, a slow and steady cut is better than beasting it.

What I did observe, and which warrants the most practice, is making sure I end the cut at the vertices of the cross section simultaneously. In other words, making sure the wire is taking the shortest possible path between the two points. Otherwise, this happens:

If I slip one corner first by accident, it makes a hyperboloid-like surface. In the aeromodelling world, I think that’s called an oops.

It’s just like a real-life loft operation!

I made a test print of a new nosecone design that is substantially smaller than the last one. The ducted fans were going to be mounted on the nosecone portion, but I decided that it was perhaps not a good idea to hang some screaming EDFs off a thin section of printed plastic. So, the foam body section has been made longer in order to mount the fans, and the nosecone got correspondingly shorter. This also made it easier to print – the large cross section at the back was having trouble with splitting and cracking. This new nose should be completely hollow, nonstructural, and easily replaceable when I inevitably faceplant 0004 into something.

This is also a two-layered (1mm wall) print. The weight of the nosecone should be about 1.75 ounces…. meaning I don’t have a scale precise enough to actually weigh it.

The real part will be made from white ABS so it can be painted easily if necessary. I’m almost out of white ABS, but still have plenty of black left over, so this test piece is in black ABS.

Besides the wire slips, the test fit looks pretty good. There will be a total of 3 foam body segments and two wing sections, along with two wingtip pontoons. Looks like there’s alot laser cutting in my future.

When Building Russian-inspired Machinery, Do as the Russians Do

Apr 24, 2011 in Chuckranoplan, Project Build Reports

Some time in 1962, Soviet Union…

“Hey, does this thing work?”

“Yeah, why?”

“Okay, let’s build a HUGE one.”

With this, I present the end result of another completely unproductive day:

Paper-chuckranoplan grew! It was a carefully tuned process of feeding and watering, as well as exposure to the proper amount of cosmic radiation.

Or carving foamcore. Whichever one you think would work.

Paper-chuckranoplan 0002 (the last effort, while nicknamed 0004-FML, has now been given its official designation) is about 1.25 meters long (45″) and has a .6 meter (24″) wingspan. The tail span is 18″. This took about 7 sheets of foamcore and like two whole hot glue sticks to finish.

A view from the front. I built this frame double-walled since a single-wall one would just look silly at this scale. In this picture, I’ve also added the roll control winglets, which are 7″ span (each) and 4.5″ long at the root.

Being double-walled and large, I might actually commit some of my recently purchased modeling components to it. In other words, it might get flight electronics. I actually ended up using two 3S/1.3Ah packs as nose ballast (in lieu of finding a large enough nut).

So how well did it do?

MIT Tech TV

Like awesome. Walker Memorial’s first floor is about 100 feet along the diagonal where I did most of the flights. I estimate PC0002 was able to glide about 80% of that if I gave it a good shove. I’d say that’s legit, and totally waiting for a set of ducted fans. I was constantly shifting the CG aroud during the tests, which is why some of the flights look a little shaky. The CG really is crucial in these things – too far back and it never picks the tail off the ground (or just straight pitches up and then falls over), and too far forward and it just drags the nose the whole thing.

 

Paper Chuckranoplan!

Apr 21, 2011 in Chuckranoplan, Project Build Reports

I officially renounce any claim I might ever have possessed to being an engineer.

I just straight give up. There’s no point in continuing.

…because look at this thing!! Isn’t it SOO CUUUTE? And adorable and foamcore-y and completely undesigned and unplanned and made in 20 minutes while I was supposed to be tutoring 2.007?

And it works exactly like it should. Of course it does… I didn’t think about it too hard beforehand.

Anyways, meet Chuckranoplan 0004FML, where the FML is for for “foamcore, medium length”, I swear. 0004FML is about 30″ long and made from 5.5-6mm foamcore, the kind you put bad science fair posters on.  With the Nut of CoG Shifting, it weighs a bit under one pound. The wingspan is roughly 18″ (just one entire foamcore sheet), and the little winglets take it to about 30″ wide.

Here’s the planform overall. This was certainly the quickest build I’ve ever pulled off. There was a little bit of precognition here, since Shane and I have been meaning to just pick up a pile of foamcore and go for it, since there’s a large supply for the 2.007 class. The joinery was with pretty standard hot glue, and there’s no other materials used in construction, excluding the nut of course.

Here’s a front lower view showing the air pocket space under the wing and the orientation of the tail.

While it did work somewhat at first, only after adding the dihedral winglets did it actually achieve meaningful roll and lateral stability. So it seems that these little winglets do play a pretty significant role in the dynamics of the vehicle after all. And it does make sense – the winglets contribute to the stabilizing dihedral effect while the main wings provide most of the lift. The technique is known already to GEV designers and is called a “composite” wing.

0004FML will not get any flight electronics, but it was a good geometry study for 0004 proper. And it looks like I’ll definitely be considering those winglets more seriously.

Here’s some shove testing video!

Doesn’t that work so awesome!?

A bit of sporadic Chuckranoplan 0004 work

Apr 18, 2011 in Chuckranoplan, Project Build Reports

You know how said I’d never 3d-print Chuckranoplan again?

Well, technically I didn’t say that; I just said I’d never print a whole model except for geometry studies and laughs. However, I still intend to use the capabilities of MaB where it would make things convenient. Some of those Areas of Convenience include the front and back of the fuselage. Planes and ships alike are usually pointy, but that implies curved surfaces that I don’t really have the patience to carve by hand.

So here’s a picture of the biggest thing by enclosed volume that MaB has ever printed.

The hull of 0004 is about 4 inches square. The tapered portion of the nose is 7.5 inches long by itself, and that’s just a bit under my 200mm maximum Z axis travel limit. The above print is just a raw single shell export of the nose, with no internal ribbing features. And it definitely shows in the wobbly, bowed sides and corner splits. This was mostly a quick test to see if MaB would even be able to pull it off.

The answer: Yes, but just barely.

This revision has lots of internal ribbing added to keep the sides stable as the whole thing is built up. Those indents in the back are eventually where I’ll mount the pivot hinges for the ducted fans. The total weight of this thing is about 1.8 ounces.

What this view doesn’t show is some of the back corner lifting that occured. When you’re building a part this huge without surround-heating, inevitably the thermal stresses in the plastic rise above what the masking tape interface can handle.

It seems like the largest parts I can realistically make without that warping are about 3″ x 3″, or something like 50% of the way up this part. So I might actually not print off the entire nose of 0004 at once. I might take another cross section at said 50% mark and make the back 50% from foam. It’s probably better off that way, since I don’t particularly trust a thin wall plastic part to hold onto a pair of screaming ducted fans. The result would be that only the tip of the nose, about 3-4″, will be hollow ABS.

So what’s this thing going to be made of anyway? I spent a bit of time splitting the parts up into their different anticipated materials to get a better weight estimate:

I swear that is not the final color scheme…

Most of this thing is going to be chunks of blue Home Depot XPS insulation foam (or pink – it could end up pink, depending on which one I see first!). The tailplane is “wing stock” EPP foam, shown here in white, and the vertical stab is balsa. The balsa tail is surrounded by two hollow shell prints that round out the stern area. I’ve also thrown in 4 A123 cells for kicks, though realistically I might use a 4S / 3Ah lithium polymer pack for maximum energy density. The A123 cells are easily available, but not that energy dense. The little HK939MG servos I got were also meticulously modeled and inserted.

I also modeled the HK3720B 70mm EDFs. I got a chance to actually spin one up…. and it’s beastly. A pack of them can probably take on Fankart, and I’m tempted to buy like 10 more because why the hell not. I definitely got one up to almost a kilogram of thrust, and I was running into the power supply current limit.

The calculated weight of everything shown is about 2.5 pounds, with slightly low estimates for foam density. If I assume the foam is closer to 1.3 lb/ft^3, the weight increases to about 2.8 lb. The two EDFs by themselves outweigh the entire superstructure. I still find it mildly wrong to think about something 1.2 meters long only weighing 3 pounds.

But, in other words, 0004 will have a greater than unity thrust to weight ratio with both fans installed. If it still fails to do anything, I’m going to commit a very slow and ritualistic suicide somehow involving a waterjet (because that would be the best way for someone like me to go, right?!). This thing better hang itself in the air for absolutely no reason.

Still looking for feedback from real Crazy R/C Airplane People… I know at least one of you read this site!