In the last episode, our heroes were…

… wait, wrong show. Anyways, I said I’d decide between TIG welding and using zinc–aluminum brazing alloy on the frame. I’ve decided to go out on the proverbial limb and put together the entire robot frame using said brazing alloy, due to the fact that getting the MITERS TIG unit up and running in a timely fashion is now impractical.

While other TIG welders exist on campus, I also don’t feel like fucking up someone elses’ machine trying to weld aluminum, something which I have only done on accident with large batteries, and only once with a TIG torch. That was more making a molten puddle of metal than anything else.

I want to investigate how legitimate the alloys are. They’re usually advertised as STRONGER THAN MILD STEEL!!!! or STRONGER THAN THE PARENT METAL!!!! which smell of marketing hype. In other words, if Cold Arbor holds together in the arena, or only falls apart under extraordinary circumstances, then I’ll probably be buying alot more of the stuff.

Alright, here’s Real Production Part #1!

I forgot to take a “before” picture, but imagine the piece with bulging, ugly round corners where I applied the alloy. Result: Not bad for the first shot. There are areas where I didn’t fill as much as I could, and an area where I parked the torch too long – oops.

Aluminum doesn’t change colors before it liquefies, unlike steel. Instead, the surface just becomes a bit darker. Then suddenly your metal starts sagging.

Mild color differences between the 6061 plates and the 95/5 Zn/Al alloy can be seen on the corners.

Another view. You can barely see where the tab-and-slot edges are any more, which is an indication of good fill. Before I applied the alloy, I sanded chamfers into all coincident edges such that each edge was a tiny V joint.

Here’s a shot of the inside edges. Inner corners are the most difficult to do properly, it seems, because you can’t get an abrasive brush into them. I only had “toothbrush” style stainless wire brushes – I’d need a “pencil” brush to get it right.

The brush is what breaks up the surface gunk on aluminum in lieu of a flux. The brazing products are all advertised as being fluxless.

In other words, you apply a large puddle to the workpiece then brush it around to wet the metal.

To hold these T-nutless assemblies together while I held them to the flames, I used center punch dimples to “flare” the tabs inside their slots by punching right on the seam.

This worked amazingly well. Almost to the point where I had a hard time taking the front frame rail assembly apart after discovering I put something in backwards.

Let’s try for something BIG, like the side rails. Click the midsize image to see my unparalleled metal joinery skills up close!

And try not to vomit. The front piece is absolutely horrifying. The problem with using a very temperature-dependent process is that your whole piece practically has to be at the working temperature of the alloy in order for it to flow. Armed with only a propane bottle torch, it was hard for me to keep the alloy molten over distances greater than 3 or 4 inches. By the time I finished one fillet, the other side of the piece has already cooled below 750°F.

Those middle two sections are probably great examples for “How NOT to use Durafix” videos. I could not get in there with a brush at all, so had to resort to prodding the surface with a (melting) rod of alloy, or using a piece of frayed stainless steel aircraft cable. Neither of which worked very well. Thus, the Epic Glob. Areas which I could access with the wire brush, such as the front and back “compartments”, especially on the second piece, were successes.

I am contemplating investing in a cheap toaster oven and modifying it to sustain high temperatures.

Alright, that’s enough for tonight. Both side rails and “intermediate framelets” are complete.

While the aluminum cooled off, I reverted back to working on the drivetrain.

Clockerb0xen cases! They are slightly modified versions of the gearboxes used in Überclocker. They are side mounted, not face mounted. Otherwise, the dimensions are the same – two inches square and about 1.5″ thick.

The stock was roughed out and circular features machine on the lathe, and the mounting holes finished off on the mill.

The nice thing about notebook computers is that they can travel anywhere. The not-so-nice thing about notebook computers is… well, they can travel anywhere.

I got lazy and didn’t print any paper drawings. Instead, I just pulled up the drawing files on the screen while the machine parked on the bandsaw. It’s far enough away from the mill that I’m confident my prized mobile computing implement won’t get showered by slivers of metal.

(Nobody turn the bandsaw on, please…)

Here’s whats inside the gearboxes.

Observe the protruding bearings. This is what happens when you forget that 6901 ball bearings are in fact 6mm wide, not 5. That’s a 6801. The net result is a little bit of bearing overflow – 2mm to be precise, since I used two bearings per gearbox.

A bonehead error but it does not affect the rest of the robot.

The pinions get shoved onto the 750-size drive motors.

I don’t have another set of 14.4 or 18 volt DeWalt motors kicking around, unfortunately, and they’re a bit on the expensive side to actually buy new. I’ll see how far I get with these things.

While the Loctite set on the motors, I turned my attention to the wheels. I noticed McMaster had added some “super soft” rubber wheels to their selection, with a 40A durometer tread. They were cheap, so I snagged 4 for engineering samples.

These things really are soft. Substantially softer than Colsons, and grippy like nothing else I’ve seen. With luck, Arbor will have more pushing power than Clocker.

I had to bore out the axle hole to make the wheels compatible with the robot. This was kind of a hairy operation, because all you have to fixture to is gumball-stiff rubber.

…but it all worked out in the end. The polypropylene hub machines like dense air.

The culmination of all of the day’s effort is PRETEND-O-BOT #1!

Fine, so it’s still more of a pile of parts than anything else. To go: All the wheel hubs, some more missing frame pieces, the structure of the saw itself, all the mechanical parts of the saw, both linear actuators, and the clamp linkage.

And that’s just the mechanicals. One month.

Unlike most of my other robots, Cold Arbor doesn’t really have a cohesive manufacturing plan, mostly because I’m waiting on too many shipments. So I’m hitting the machines as components tickle my fancy – not necessarily working on the same assembly until completion.

This has led to the robot table becoming a hopelessly cluttered mess, but at least things are getting done. One month and a week to Motorama – it’s time for SRS BIDNESS.

I managed to mechanically complete Deathrunner as well as start on the drive motors and the frame.

I put in the radially symmetric features of Deathrunner using my haute usinage utility, a rotary indexing head. It’s like my very own 4th axis, if I had a CNC mill where the “C” didn’t stand for “Charles”. Here’s the set screw holes on the motor hub being power-threaded.

The Petri Dish of Motor Mounting (+6) has a slot cut into it in order to pass wires. How did I drill those cool elliptical holes in the center?

Unfortunately not with a rotary broach. I drilled once and discovered that I had transposed two numbers in my dimensions – 0.695 instead of 0.659.

Oops. So I went back over them with a carbide endmill. The extra-large clearance holes won’t affect stator mounting.

All the parts of Deathrunner are prepared. The endcap is my favorite piece of machine work so far.

Look! An assembled Deathrunner!

No windings yet, nor any case screws, just a proof of concept. The case runs true and everything is smooth.

Let’s move on to the drivetrain. Remember when I said I couldn’t find any more 24:1 drills?

Reading back through old Überclocker build reports of 2008, I remembered that I had purchased two additional 24:1 geared drills for spare parts, but they were never used.

They had to be around somewhere. A bit of excavation in Überclocker’s parts box revealed the gears of that drill pretty evenly distributed across the bottom.

So here’s the spare 24:1 first stage that I’ll be incorporating into Arbor. That means the fancy  2 speed drill hack has been ditched, and I’ll just be making two more Clockerboxes.

Every build report of mine seems to have at least one picture of a pile of drill parts. Here’s this one.

I began parting out the Handiworks gearboxes to use the ring gears and spindles. While I have a reserve of spare drill parts, I decided to use Handis anyway because their parts matched. There’s no guarantee that any two drills spindles I take out of the pile are actually the same size.

In a moment of inspiration, I used the chain tool as an improvised gear puller. This worked great for the 700 size motors that came with the Amazon drills.

Protoforms for the gearboxen emerge. I popped these off using the Bitch Chuck and some 2″ square aluminum barstock.

The Handiworks ring gears turned out to be different sizes by a matter of thousandths – one was 1.493″ diameter, the other 1.497″. That much difference is enough to throw off a press fit, however, so I actually had to make two different parts. They are paired with their respective ring gears.

Both bearing and ring gear will be secured using the freeze-and-burn method.

… and here we have it, Round 1 of waterjetting for the frame!

Arbor’s frame is all 1/8″ aluminum plate with selective 1/4″ reinforcements. This time, the tab and slot puzzle doesn’t have T-nuts.

I’m dead set on either zinc-aluminum brazing or real, legit TIG welding the frame together.

How am I going to TIG weld the frame? With the NEW MITERS TIG WELDER!!!!!

…

Okay, so it needs some love. As in, it needs a correctly fitting torch, a gas supply, electrodes, rods, and a 230 volt plug of a type that exists in the build space. As usual with Harbor Freight, the fittings and connections seem to be all proprietary, or extremely rare. The cheap torch we purchased turns out to use a different style of weird proprietary fitting.

Since the unit IS cheap and Chinese, I have no qualms about hard-wiring things or chopping something togethe, and that might just happen with our cheap replacement torch.

We’ll see where this goes…