Give me a big enough lever...

The real servos finally arrived! here is the Hi-Tech HS-805BB Mega Giant Scale Servo being tested. I simply attached one of the many great horns and plates that it comes with to my fish-line spool, using its own screw and voilà! 19.8 / 24.7 kg*cm (4.8V/6V) of torque! It is temporarily held in place with straps as you can see because as you can imagine the square holes of the Vex plates don't line up with anything but their own stuff (I promised I would stop bitching about it!)

For the rest of the controls I am using the HS-645MG UltraTorque Metal Gear Servos that have 7.7 / 9.6 kg*cm (4.8V/6V) of torque, very much on the safe side.

On the left of the picture you see Vex's red optical encoder which I planned to use to determine the position of the continuous rotation motors that lift the arms, but again, not even the extremely versatile Make controller could recognize the simple signal. I am sure it can be done but why waste time. I ordered a set of high-res 10 turn potentiometers that are not only more precise but can "hold" the last position even when the power is turned off.

Divide and conquer?

That seems to be the design philosophy of the VEX guys. I promise (well, a weak promise) that I won't waste more time bitching about their horrible "close source" design decisions. But someone has to say something. Of course I used their stuff to prototype my project since I had bought 5 or 6 kits with the hope of actually using them for the final project. Now, to be fair, their nuts and screws are first rate and I have no complaints, as well as their cute chain transports if you use their square shafts of course, but the rest...


It was obvious pretty soon that the electronic/hardware side would not work due to their very flimsy nature and weak linkage (or lack of it). Take their servo for example. Not only is it far from standard, so that you cannot mix with any other brand, but it lacks fundamental elements like a horn or attachment plate of some sort so that you can drive something more than their absurd square shafts. Guess what, you cannot even screw anything to it, you can only use their "clutch" (the small cylinder with a short square stub) to attach another square shaft to drive any square holed device! BTW the clutch and therefore anything attached to it, will simply fall off if you turn it upside down. Am I missing a screw here?

You cannot see it in this next picture, but those arms or extensions that I need to drive the limbs of the marionette with have as much strength and stability as an apple stuck on the tip of a drinking straw and balanced on the edge of a glass, can you picture that? perhaps David Copperfield could use such a trick. The main reason being that as I explained, the servos connect to anything else through the wimpy clutch mechanism that cannot stand any side pressure, only direct transmission to a wheel at the most.


To be fair, after a great deal of literally hacking away with a saw, drilling and cutting and bending, I was able to put together a somewhat functional scaffolding for the stage. If I had the money I would simply make everything from scratch out of aluminum and some steel pieces. And, yes, chuck those servos away. I opened one to convert it, I was so shocked by the poor craftsmanship inside, probably built on a Chinese sweatshop (badly soldered by hand), that I just closed it and proceeded to order a set of excellent Hi-Tech servos.

Snap to grid

Serious construction begins. This has to be, want it or not, the last stretch of the building process for the Creator stage.

But before I begin this section I want to share a tip that I take for granted, but friends that see it are always amused by it. You know that when you work on a project involving dozens or hundreds of small pieces, screws, washers and what not, things like to go amiss. Lost socks pale in comparison, specially when you lose a servo screw that you won't find in any hardware store (unless you live in the Bay Area, how I miss that!). And ordering a screw or two online just does not cut it.

So, I use a big magnet block (which I don't remember where I got) and simply and literally throw all those little pieces at it, even from quite a distance and it just snaps them as they try to go by. Sometimes I am working on an odd position, (upside down ?) and as I disassemble something, which happens more and more often as I try to refine my design, I start collecting all these little pieces in my hand and mouth that are eager to disappear in the cracks of the floor or my stomach. Well, just toss'em up like a chef flipping pancakes towards the magnetic field and , snap! they are not going anywhere.

Now, mind you that this is not a very powerful magnet, like those neodymium or ceramic magnets that you find in hard drives otherwise getting a washer back would probably be impossible, but it is strong enough to hold quite a bit of stuff. Sometimes you cannot even see the magnet anymore, just a weird nut screwy sculpture. I'll add a pic like that so you can see it.