There is a problem about some instructables: it's easy to find the materials in some countries, but it can be hard (or expensive) to find them in another.
Frecuently, I've been asked about how to build some of my reuse projects because it's not easy to find stuff, as an example, oven knobs (those are good robot feet) or Atari joysticks (I used two damaged ones for "Rob Zombie" and the Atari Fans almost sacrificed me to the Space Invaders for destroying World Heritage) . That's the reason I always say "If you don't have it, replace it!". Replacing materials can take you to interesting new designs, some for better, some for worse.
To demonstrate this, I made the Walker, one of my favorites Randofo's projects. I love Simple Bots because you can build some pretty awesome robots without being a robotics genius (I wish I could be one, someday!). But I got problems with most of the materials, so I had to make some replacements (original Walker stuff is first in bold letter):
(x2) servos modified for direct drive: In Colombia, the servos are very expensive. So I used gearboxes from a small R/C toy car.
(x1) telephone handset: I fix the gearboxes using an iron angle. I made a "head" with a motion sensor plastic case (it houses the battery holder) with a red eye (plastic caps plus a red LED). The head is attached to the body thanks to a plastic bar.
(x1) 4 x AA battery holder: no problem with this but, thanks to the power of the gearboxes, I could make it works with only three batteries. So I had to hack the battery holder for completing the circuit.
(x1) DPDT lever switch: no problem with this.
(x2) CDs: I don't like to work with CDs, so I used black plastic bars. For the back disc (that moves the switch) I used a pentagon Transformers toy from a cereal box.
(x2) 6" bolts, (x2) 5" bolts, (x4) bolts, (x4) bolt covers: I wanted to try a flexible design, so I used copper wire covered with black rubber hoses.
(x2) thin 1" nut and bolt, (x1) a couple dozen assorted zip ties: I used a lot of nuts and bolts. I don't work so much with zip ties.
As you can see, the design varies a lot and it looks totally different to Randofo's Walker. Even the motion varies. I love the red eye because it looks more like an evil drone. An army of evil drones trying to take over the city would be great!
My next goal is, based on this design, to build a Lady Cassandra's Robot Spider (Doctor Who fans know what I'm talking about)