Saturday, April 4, 2020

SBS - Six Leg Robot - Installment 2

Six Leg Robot / Walker Step – by – step (Installment 2)

The Build
I used two part epoxy resin glue to secure the pins and legs.  To help hide the joints between the legs and body I used two part putty ("green stuff", more on that later) and sculpted “fabric” dust covers around the joints.  Using a toothpick, hobby knife, and other small sculpting implements, I added wrinkles and folds to simulate a flexible cover.
fig.4: "Green Stuff" putty sculpted into flexible dust covers for the joints.
            Another advantage of this kit is that scale is entirely up to the modeler.  There are really no cast details that define a specific scale.  I had played around with many back stories to this build and tested the model against many differently scaled models.  This kit looked great no matter what I had it posed against.  In the end, I settled on 1/100th scale.  That little human figure (“scale-guy”) in fig.3 above, is 1/100th scale.  Determining scale will help during the build-up and painting phase by informing us of the sizes of details we need to keep to.
Adding Details

I knew that I wanted to add an extra level of detail to the model.  I added hydraulic actuators and hoses, just to provide a little more visual interest and movement to the piece.  Before attaching the legs I pre-drilled holes that I would later fit telescoping aluminum tubing and wires into.  These would give some purpose to the many cylinders and shapes cast on the legs.  You can buy lengths of aluminum tubing in various sizes and I was provided a few lengths to play with.  If you want to do this, you'll need to drop by your friendly neighborhood hobby shop / train store (FNHS), and pick up some extruded metal tubes.  You can usually find such items by K&S Precision Metals. Each tube fit nicely into the other so, by cutting off measured lengths, I could create the hydraulic actuators at many of the leg joints.  I also added lengths of wire to replicate pneumatic or hydraulic hoses.  These were lengths of different diameter wire glued into more pre-drilled holes.
I used a small-ish diameter insulated electrical wire for the thin hoses.  The larger hoses were cut from a roll of 16 awg Primary Electrical Wire that came in a 24ft roll from Home Depot.  24ft will last you for a few models!  I found that this wire had a multi-strand copper wire core which made it very "rubbery" so it wouldn’t hold its shape very well.  To solve this problem, I pulled out the multi-strand copper wire core which left me with the plastic insulation tube. I then threaded a single length of thinner wire (the same wire I used for thinner hoses) through.  The thinner wire had a single copper wire core and was much better at holding whatever shape I bent it into.  I used cyanoacrylate glue (think Krazy glue) to secure all the wires into pre-drilled holes.  Once dry, I could bend and shape the hoses into nicely draped forms.
fig.5: Pulling out the multi-strand cores of the 16awg Primary Electrical Wire
fig.6: Replacing the core with a thinner but stiffer single core wire
fig.7: Plugging the hoses into my pre-drilled holes in the legs
Here’s some hints for applying cyanoacrylate glue.  I first put a few drops of the glue on to wax paper...the stuff you find in your well stocked kitchen.  The glue will bead up on the wax paper and stay viscous and usable for much longer.  I have an applicator that I made from a sewing needle.  I cut the end off the needle’s eye leaving a small “U” shape.  I ground down sharp edges and polished the “U”.  Chuck the needle into a pin vise and, by dipping the “U” into the CA glue bead, you can transfer very precise drops of glue to your work.  I use thin CA glue and it works great.
fig.8: CA glue applicator made from the end of a standard sewing needle chucked into a pin vise.

That's all for today.  More to follow soon.