hey robot fans welcome back to the build today we're gonna take a break from
choppers head and take a look at his feet and see if we can get them
motorized and driving around diving right in I did a rough model of the foot
shape choppers foot is pretty basic compared to r2d2 s foot which is really
nice on the 3d modeling side of things as far as where I came up with the
dimensions for the foot here I just hacked off the front and back of this
little foot skirt here and made the rest of the length 290 millimeters which is
the exact length I need to safely print it in one piece on my print bed with a
couple support disks I'm designing this whole foot from scratch but the basic
idea behind how it works is nothing new especially in the astromech community i
roughly placed a scooter motor which will drive a wheel in the front and an
omni wheel will be trailing in the back with the main shapes in place I kind of
subtracted out a structure for the main drive mechanism which will sit inside of
an outer skin from there I really just build out the main structures and
started placing the components more realistically and the final step of this
was just making it more functional and making all the parts work the way they
should I added in axles and mounting screws and spacers and bearings and all
kinds of hardware I also removed a lot of dead weight from the frame this is
still gonna be a big old honking foot but I reduced a lot of the mass to make
the printing process a little easier all the pieces are printed and now I can
start assembling I screwed together the frame first that helped hold everything
together tight as I start inserting the individual drive components before the
last side of the frame goes on the omnidirectional wheel and motor get put
into place for the omni wheel I'm using a three and a half inch wheel purchased
from mcmaster-carr for those unfamiliar with Omni wheels
they spin like a regular wheel but in addition to that they can also move
horizontally thanks to the rim of the wheel being made of even smaller wheels
I'm also using sleeve bearings for spacers on the front and back axles so
for the omni wheel installation the spacer goes on first followed by the
rear axle then the omni wheel and another matching sleeve the motor I'm
using is a Currie technologies 24 volt 135 watt scooter motor with an HT d3m
pulley attached this may be a little bit
overkill but I'm really not sure how heavy this droid is going to be in the
end so I want to be ready for anything the wire for the motor gets routed
through the top of the foot so it can enter up into the ankle and then the
whole motor slides into its base on top of that goes the last piece of the frame
to hold the motor and omni wheel nice and snug with everything secured I can
unscrew the hub cap to expose the motor pulley and the front axle area the drive
wheel is entirely 3d printed it consists of a tyre printed in semi flex filament
two hubs and the drive pulley the hubs are keyed in four places to match the
interior of the tyre to keep the tire from independently rotating around the
hub these just get sandwiched into place and screw together on top of that goes a
printed HT d3m pulley to match the motor the setup goes exactly the same as the
omni wheel with a spacer installed on each side of the drive wheel an HT d3m
timing belt gets placed on the two pulleys and is tensioned when the hub
cap gets reinstalled an m8 nut locks the axle in place and our foot is ready
okay ready to do our first motor test here I have the motor plugged into a DC
power source here I have it currently set at 12 volts it's a 24 volt motor so
we'll just run it at half voltage for now so that's it at 12 and let's see if
we slowly increase it here that is 18
and there's ice at 24 volts just about yeah that's running pretty smooth I'm
pretty happy with that let's see what happens if we put it on the floor so you
having this on the floor even with 12 volts is just it just skids out Oh ran a
little bit but yeah it's just it's just spinning its wheels down there so I'm
gonna have to put some weight on this to do a real test since we're doing a real
test here we should really do a real test I printed the other foot which is
really just a mirror image of the original foot I'm attaching an m12 axial
between the two of them with 30 pounds of weight on it so we can actually drive
I purchased a 2 by 12 saber toothed motor controller these are widely used
in the r2d2 builder's club to give you the smart tank style control we want I
rigged up the saber tooth to an Arduino mega and attach that to the top of one
of the feet and on the other feet I have a battery holder everything is all wired
up and I'm ready to give it its first real Drive I'm only running this at 12
volts at the moment it seems to have no problem moving smoothly with 30 pounds
on it even at the 12 volts so that gives me a pretty good feeling about the final
Droid being quick even with all of its weight as far as code I'm literally just
running the r2d2 shadow code that's been developed since it's only the feet at
this point there's really no difference between chopper and r2 and everything is
running off of the ps3 controllers just like we did with the head tilt a big
thanks to James Van Dusen for giving me that code to work with I got to say I'm
totally sold on this saber toothed motor controller it's really maneuverable
there's none of that annoying PWM sound and
the voltage is just really smooth it speeds up nice and slows down nice no
suddenly jerkiness are stopping I really really really like this motor controller
I think that's gonna do it for this video in the next video we're going to
keep moving up the leg and hopefully see if we can get these feet at least close
to attach to the body I'm still working on the head as well I figured it might
be more efficient to split this build into two parts and work on them in
parallel whichever video finishes first will get posted first the final order of
this may be a little disjointed but at least there won't be huge gaps in the
videos while I try to figure something out on one end of things or the other so
yeah that's all for now and I will see you next time