Archive for December, 2007


TB4.5MCESP1 Update 4 and another vaporbot.

Dec 31, 2007 in Bots, Project Build Reports, Test Bot 4.5 SP1

New plan! Again!

Due to some unforeseen characteristics of the Banebots 12-45, my plan of adding thermal mass to the electronics bay won’t work out, at least not without more precision engineering than I am willing to put up with. This coupled with additional budgetary concerns means that I’m keeping the Victor 884s. There’s nothing wrong with them, and they are in fact very good controllers. However, the reason I wanted to move away from them was due to size issues – they’re not exactly compact.

But most of the time, big and beefy lasts the longest and is the most reliable. Here’s a temporary drawing of what the new internal arrangement will look like. I have yet to model the mounting plates.

This is roughly the same as in MCE – battery, power switch, and arm controller (the Syren 25 is staying) on the right side, and the drive controllers and receiver on the left. With increased space in the middle of the bot, I can mount the Victors longitudinally as shown, but there is really no advantage to it as the arm controller wouldn’t fit in the space between them and the drive belt. So to free up space for wiring, I might just keep the widthwise mounting of the 884s.

I hate scaling back the Grand Master Plan, because now there really is no upgrade besides a lithium power system and possibly higher grade alloys for the wedge and arm – “possibly” because higher grade alloys cost more, and so that planned upgrade might not happen either.
Whoopee. Now that SP1 is looking more like a bugpatch, I’ll unveil the latest Team Test Bot vapor design.

Trial Bot 1.0, way back in 2005, was my first attempt at building extremely low bots. It was an overhead horizontal kinetic weapon design, an inverted lawn mower design (even had a 22″ lawn mower blade). At the time, it had ground-to-blade height of 2.25 inches, which was obnoxiously flat, but suffered from a multitude of engineering problems: low ground clearance made worse by non-countersunk chassis bottom screws, an unreliable friction drive mechanism, and a tendency to become unbalanced and ping itself.

With the wide-scale commercialization of high-performance lithium polymer power systems and brushless motors, I can do much better.

Yes, that’s right, a ground-to-blade height of 1.6 inches, which, numerically, is smaller than most bots’ wheels and right around TB’s three-quarters mark. The chassis is 1.125″ thick, and was designed to be aluminum, since UHMW of this thickness would be unbearably floppy. This is only possible with customization of just about everything. The frame is thin enough to be made as one piece using an abrasive waterjet with draft compensation. Notice the ersatz-tank tread drivetrain, which gives the effect of “4 wheel drive” without needing a separate belt and pulley assembly. This will be accomplished using urethane round belt, like NK, or some really big o-rings. There are three on each side for redundancy, but I don’t doubt the bot can just take off and land somewhere using the blade if the drivetrain is disabled.

At the center of it all is a very large brushless outrunner motor, similar to Pop Quiz – in fact, PQ was built to test the viability of direct drive weapon motors in larger bots. As designed, this motor weighs almost 3 pounds and has alot of solid metal on it. The mount also attaches directly to the bot frame to make the whole assembly as stiff as possible. A copier motor will supply the stator, which will be 70mm in diameter by 20mm tall. Motors of this size are commonly used to fly model airplanes weighing 20 to 30 pounds.

Note the triangular cutout at the back. This is a by-product of designing the bot with a base size of 12 x 12 inches, common to all of my 12lbers. However, this leaves most of the interior empty because of more power-dense, hence smaller, components. The bot can be shrunk to 10 by 10 inches easily and make more efficient use of the space as well as free up weight (for a bigger blade!), but I’ll worry about it when I actually have the ability to build it.

It’s fun thinking about future designs, but 2008 is approaching and I need to get to work on SP1 – the parts pile is condensing from the bot-aether.

TB4.5MCESP1 Update 3

Dec 26, 2007 in Bots, Project Build Reports, Test Bot 4.5 SP1

It’s that time again where I need to mill down the corners on the build budget. The total cost to make the SP1 upgrades (granted it’s more of a complete rebuild) is over the $500 mark. That’s alot. That’s more than I care for, so some of the neat features have to be scaled back.

Yeah, because… I need to eat and buy textbooks too.

It looks like I’ll have to settle for a set of secondhand Banebots ESCs – this is a somewhat suboptimal setup, but I can, again, make provisions for extra cooling. The lithium battery pack is definitely staying – I’m not going to let batteries be the limiter of the bot’s potential again. The fancy charger I have currently lined up might also get downsized – even though it’s an investment I want to make since it can charge about any chemistry and balance lithium cells, and so will be usable for many projects.

Here’s a hypothetical situation using 3 Banebots ESCs. They fit in the same spot, and are more compact, but are rated for lower amps. Not out of the limits, but the overhead is lower than I’d like it to be.

Stay tuned for more! Maybe I’ll ditch the 2024 for the arm and wedge, because that stuff is ass-hell expensive!

Is it too late to ask for Christmas presents? Godspammit!

in suburbiā atlāntae

Dec 23, 2007 in Stuff

Well, I’m here. I’ve actually been here since yesterday, but nothing much happened and I was too tired to bother writing up a post anyway.

So anyway, the house is in a mild Idiocracy condition since I wasn’t around for 4 months to keep things in running order. I should have known as soon as I pulled up in front of the house -one of my large hard drives was propping up the garage door for cat entry.  My parents have a habit of going through my cruft piles to find large blocky metal things (of which there are plenty) which they then use for a variety of things – fish pond weights, doorstops, and apparently garage door spacers. I’m glad I didn’t have to dig out that drive (it’s an oooold 5.25″ full height drive) from the fish pond.

Some of my drill bits are also broken and I’m going to just take their word for it that the cordless drill battery hasn’t been charging for the past 3 months. My parents, although they are very well meaning people, aren’t exactly skilled in the industrial arts.

Some random appliances and household objects need servicing, which isn’t a problem.

The agenda now that I’m here is as follows, in no particular order and with no particular priority:

I also will be helping coach NGHS Robotics after the new year. That should be interesting!

Reporting from the airport…

Dec 21, 2007 in MIT, Bostoncaster, Cambridgeshire, Stuff

Since I’m at Logan International Airport, it’s obligatory that my post have some of these.

Merry Christmas.

It’s over.

Dec 20, 2007 in MIT, Bostoncaster, Cambridgeshire, Stuff

I’m done. And I think I managed to pass everything too!

You know what's SPAAAAAAAAARTAAAAAAAAAAAAA? Hardcore and militaristic, unlike Athens.

So I’ll be heading back to Atlanta tomorrow morning and spending the next 3 weeks there. I’ll be back January 16th, the middle of IAP season so I’ll still be able to catch some fun stuff.

Some of those 3 weeks will be spent helping to coach North Gwinnett High School Robotics. Looks like my progeny has grown far beyond what I expected even at the end of last year, so I guess I’m in for a fun time.

And off we go!