Page 366 - Robot Builder's Bonanza

CREATING X- Y SERVO JOINTS 335

In lieu of standoffs you can construct your own risers using a suitably long machine
screw, some aquarium tubing, and a couple of nuts. Start by drilling matching holes in
the Hex3Bot base and the second deck. For whatever riser length you want, add 3/4″
to accommodate the thickness of the base and deck, plus extra for securing a nut on
top. In the case of a 1- 3/4″ riser, select a 2- 1/2″ screw, and cut the aquarium tubing
to 1- 3/4″.

Creating X- Y Servo Joints

With two servos (any size) and some basic parts, you can construct an articulated X- Y joint for
use in multilegged robots, as well as servo turrets, gripper arms and wrists, and a variety of
other mechanisms.
There are literally hundreds of ways to construct an X- Y joint using R/C servos. The one
outlined here (maybe it’s #113, who knows?) is designed to be easy to construct using ordi-
nary shop tools. It lacks some features such as supporting shafts on the side opposite the
servo, which is useful when lifting heavier weight.
But given the typical robotic application, you’ll probably find this method more than ade-
quate. (Of course, feel free to modify the design to incorporate any improvements you see fit.
A couple of suggestions follow the how- to construction guide.

CUTTING THE PARTS

G The sizing dimensions that follow assume you’re using standard- size servos. If you’re using
larger or smaller servos, you’ll want to adjust the dimensions accordingly.

Using 6mm expanded PVC sheet or 1/4″ aircraft plywood, begin by cutting a strip mea-
suring 2- 1/2″ 6- 1/2″. This is enough to construct a pair of X- Y joints. If you need six
pairs— you’re building a six- legged hexapod, for example— cut three of these strips.
As shown in Figure 27- 20, next cut up the strip into four 1- 1/2″ segments. Depending on
the kerf width of your saw, the last segment may be wider than 1- 1/2″; just cut it to the
proper size. You will end up with:
• Two servo mounts. You’ll mount the servos to these.
• Two solid plates. You’ll mount servo horns to these.

6-1/2"

2-1/2"
Figure 27- 20 Cutting guide for
making the X- Y joint bracket pieces.
Use a piece of 1/4″-thick wood or
1-1/2"
plastic that’s 2- 1/2″ wide, and cut
Cut into 1- 1/2″ slices.

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