And the beat goes on.

The wire’s coming up fast.My summer internship with iLolbot ends this Friday. After that, I have a solid week where the only damn thing I’m going to do is plug on ‘clocker day and night. In precisely two weeks time, I’ll have to have everything wrapped up and shipped down to Atlanta. Lack of 24/7 tool access means that the state of the robot as of midnight on September 1st is pretty much going to have to be final.

At this point, I doubt I’ll have time to get to Pop Quiz at all. I thought Nuclear Kitten had required only a re-magneting, but it turns out the motor needs a total rework. Additionally, I need to reconsider the drive motors, since I went through two gearboxes last year and do not have any spares at the moment.

The insect status for Dragon Con is therefore tenuous.  NK is a second priority after Überclocker, and only if I think the design is going to be solid. Two events of last-minute rushing have sent me the message that last-minute rushing makes robots not fun.

Hell, if Überclocker doesn’t make it, I’m just going to D*C for the sake of going to D*C. Maybe I can actually take some pics this time.

Überclocker Remix

The build has pretty much reached the point where I’m the only bottleneck. That is, I have to fab all the rest of the part, and I’m slow compared to a CNC anything.

Yeah, I consider that “slow” now.

It’s time to start filling in the pretend-o-bot!

The “shocks” for the springy front legs. These are, like on Überclocker 1, post-op’d waterjet parts. I actually had to rework this design on the fly because I ordered the wrong kind of shoulder screws – 5/16″ diameter instead of 1/4″. The problem was that my springs had a 1/4″ rod-fit size.

Ever machine a spring? It’s not pretty, but a 5/16″ carbide endmill chucked in a lathe tailstock made pretty short work of it. I was expecting some epic disaster with the spring unwinding or just exploding out of the chuck.

This is the leg arrangement with the ‘shocks’ in place. I thought 100 pound/inch springs were going to be too stiff, but the high lever arm ratio of the linkage means the whole thing is still pretty bouncy.

More little shiny round things are now appearing around the robot. These are the drive “standoffs”, which function as dead axles. I formerly made these part of the robot structure, but it was an epic pain undoing the screws which held the body rail/panel to the standoff. Therefore, I just made a shoulder which sits in a bore on the outside walls of the robot. It’s not entirely structural, but will resist cave-ins (from impacts) to a degree.

I did end up putting a threaded hole on the outside end just in case I changed my mind.

The standoffs were made from 12L14 steel, which is something like two beans and a lollipop per six foot rod on McMaster. I have a new appreciation for this stuff – it’s like… steel, but it machines like aluminum.

Then again, how much should I be trusting steel which machines like fucking aluminum?

Hubs!

Well, these are actually functional prototypes of hubs. It was easier to pop four off in one cycle than to switch back and forth between machines, completing one at a time.

Completed hubs, with sprockets. Remember those sprockets with the weird double-D shaped bore? Now you know why.

Simple retainment and power transmission with the aid of the DD and a snap ring. I used to hate retaining rings (snap rings, C-clips, etc…) with a flaming magnesium passion. But after getting a set of snap ring pliers I realized they were the most compact and cheapest way to keep something axially where it should be.

So now I love snap rings. The cool thing is that the sprockets are easily removable, so I can press the wheel on later. This was just an assembly test.

… but wait, what do you mean the chain doesn’t go in my sprocket teeth?

I highly doubted it was a pitch/scaling issue, since some times the chain was able to wrap all the way around and other times not. I suspected that it was more a building up of small incremental errors made by the waterjet as the c hain went around the circle.

The solution was as simple as giving each tooth a really quick flick over the open section of a belt sander. After that, it was still sort of rough, so…

… this is TOTALLY LEGIT GUYS I PROMISE.

I am under no circumstances endorsing this kind of behavior.

Yeah. Right. Anyways, chuck one hub in a powered spindle of some sort (I had a convenient one 10 feet away), and put the other hub on a little axle that you can grab onto.Link the chain between the two sprockets and power the machine on.

Assuming you haven’t been sucked into the spindle yet, pull on the axle, hard.

This sort of grinds the chain into the sprocket teeth and forces it to round out imperfections just by virtue of being under balltastic tention. I was only limited in the pull force by the fear of the whole lathe rolling over onto me.

The sprockets ended up pretty smooth.

So I take back every mean thing I have ever said about 4 jaw chucks. They are wonderful, wonderful creations of man. More epic than the discovery of naturally-occuring sliced bread and the invention of the solar system.

But they’re still a bitch to use. However, it’s totally worth it for some situations.

Such as when you want to square off a section of barstock and insert a symmetrically-located circular feature in one setup! In fact, for situations (not speaking from personal experience at all) where your choice of barstock-portioning implement somehow makes an angled cut in two axes at the same time on both sides, the easiest way to get a known square end might be to cram it in a 4-jaw using the flat sides of the barstock and perform facing cuts.

I was only able to find tutorials on how to center round things online, but not square ones, so I had to invent my own little method first. Essentially it boils down to comparing the minimum deflection of a dial indicator on opposite sides and adjusting the jaws associated with those sides until they are the same. “Minimum deflection” refers to the location where the indicator tip is exactly perpendicular to the surface of the part. Any rotation would cause it to extend more.

…did I mention that 4-jaw chucks are a bitch to use?

Here are the results of a night bitching around with Bitch Chucks. These are embryonic drive gearboxes – more or less repackaged drill motors.

I discovered an annoying feature of one of my digital calipers which caused bore measurements to be .007″ under what they actually are. Imagine my surprise when I discover that a 0.944″ OD bearing passes through a 0.936″ hole.

It turns out the ID-measuring points were bent inwards such that they overlapped slightly.For future measurements I’m reverting back to an older (but less grunged) set.

This probably happened that one time they fell off a moving bike. Don’t ask why I have digital calipers mounted on a bike.

This is technically the sixth update of the bot overall, but only the second one in which I’ve actually built anything worthwhile, so it’s okay, right?

Look! It’s a bitch chuck!

Also known as a 4-jaw chuck, but I call it the Bitch Chuck since it’s a total bitch to use. It was determined that we could afford to spend some club money on replacing sketchy equipment, so I hopped on eBay and lassoed in some new 6 inch chucks, in 3 and 4 jaw form.

In testing and installing the new chucks, I discovered that the machine does indeed have a collet mode. My next step in shopbuilding is to get a wider variety of 5C collets.

The cool thing about Bitch Chucks is the ability to use the 4 jaws as the axes of your own coordinate system. This means you can, with enough jiggling of a dial indicator, center just about anything. It’s most often used for machining round features in substantially non-round objects.

Such as my leadscrew actuator anchors, above.

Bored out pieces. These were waterjet-cut first, which leaves a rather raggedy bore, necessitating secondary operations.

More actuator parts. The piece on the left was also waterjetted, then secondarily operated upon. The part on the right was milled from a block of aluminum.

These two pieces bolt together and trap an Acme-threaded nut between them. When the nut is spun, the whole assembly travels up and down a leadscrew.

Pretend-o-actuator. A 28mm Banebots gearmotor (I’M SORRY IT WAS THE ONLY THING THAT WOULD FIT THE DESIGN) drives the leadscrew nut through a 1.5:1 additional reduction.

Fr0k main shaft, made of hard-anodized 6061 rod. The flat is for the fr0k hub to grip onto using a line of Giant Set Screws. It is otherwise smooth for the clutch connection with the fr0k gear.

BEARINGS!

All the important bits (gearbox outputs) on Überclocker will be ball-bearing supported. Ball bearings, especially small and metric ones, are not cheap. That said, I got these from VXB, which…hey, sells cheap, small, metric bearings.

They are of dubious origin, devoid of manufacturer labels. But everyone knows that renowned ball bearing manufacturers have cool 3-letter company names, so they must be totally legit, right?

When I need a thick section of material to fasten a larger T-nut, but the rest of the part is thinner plate, it’s handy to use a screwed-in thickness buffer. Here are two quarter inch plates combined to make a single half-inch fastening location.

Mockup of the fr0kshaft. The three aluminum donuts with Giant Set Screws are the fr0k shaft hubs. A long shoulder bolt passes through a two-hole pattern in the side (barely visible). The left fr0k tine is a clearance, the right one a tapped hole. The entire assembly binds together, then is Giant Set Screwed down.

Alright, back to the upper fr0k actuator. The motor pinion bore is 5/16″ and the motor shaft is 6mm. That’s a space too wide for even the thickest Loctites to bridge.

So a spacer is warranted. Here, I turned down a random steel rod to press fit into the gear’s stock bore. Then I pushed the gear onto the future spacer by locking down the tailstock and using the quill to apply a force to the gear.

Yeah, that’s right, I used a metal lathe as an arbor press. I hope the shop instructors aren’t reading this.

Drilled, tapped, and mounted. Conveniently enough, the Banebots motor has a keyway in the shaft which seats a #6 set screw very well.

Here’s the fr0k base in mockup configuration. Eventually, the Integrated Dual Frakenb0xen will go in the middle, secured by the four mounting holes.

Secondary operations on the fr0k base parts. I center-found one hole, then referenced the rest from there. This is to avoid Waterjet Weirdness creeping too much into the parts. If I had centered and bored each hole individually, they would be in 3 different incorrect places. At least with the former method, they may all be off by a hair, but it’ll be in the same direction, so things still go together.

These ring bearings will support the hubs of the Frakenb0xen pinions.

Leadscrew anchor block. This was originally going to be a waterjetted-then-machined part, but I found the most conveniently placed block of 1″ x 1.5″ x .75″ aluminum ever, so I just fabbed it in a few minutes.

The radius was smoothed on the belt sander after I made 3 45-degree angle cuts to approximate it.

This anchor looks kind of like the previous one which failed miserably, but is actually much improved because the set screws reside in deep-cut flats on the leadscrew. I would have to shear the set screws, strip the leadscrew, or just plain rip the leadscrew anchor ears right out of the fr0k assembly.

i.e. It takes alot more force to fail, but will fail irrepairably and probably inopportunely.

Great.

Testing the actuator! The banebots motor is _fast_. Ridiculously fast. The arm hits physical travel limits within maybe one second. This is so fast that I think I should have picked a finer leadscrew or something.

Or it could arise from the fact that I’ m triple-overvolting the BB motor, meaning it will also not last very long. This is one candidate for a high voltage motor swap. Regardless, it will need a limit switch or sensing element of some sort, because in the heat of battle I’m probably going to just jam on the throttle stick with reckless abandon.

The upper fr0k in its lowest position can actually hit the ground below the bot. I’m not sure if this is a good or bad thing yet. Again, an argument for travel limiters.

The whole arrangement sort of reminds me of cantilever-style C-clamps.

HEY!

It’s time for an episode of PRETEND-O-BOT! In this episode, Charles wonders where the fuck all of summer has gone and why only 3 weeks remain before tools have to be down.

The fr0k in its maximum opening position can grab objects roughly 10 inches tall. This is good enough – few robots are entirely that large. If I wanted to, I could cut out a portion of the truss that binds the top fr0k sides together and get another inch or so of rise. However, then I start risking running the motor into things.

• Make the drive gearboxen and hubs, including
  • Cut out the drive gears
• Make the Integrated Dual Frankenb0xen
• Finish the leadscrew actuator
• Design the electronics enclosure
• Make the electronics enclosure
• Design the top and bottom plates
• …make the top and bottom plates
• Panic
• Panic
• Panic
• Panic
• Panic
• Panic
• Panic
• Panic
• Panic
• Panic
• Panic