Sunday, 14 June 2015

Elbows; Would sir like two or four with his hunch?

I've caught up with machining all the 3D parts I had prepared. While the 3D model has been made solid and the major joints to the torso have been done, I still need to work out how the Hunch joins to the rest of the model (so far it proving a major headache if I want to make it 'hot swapable') and allow space for the shoulder to still rotate (in the game it clips). Plus all the details at are lacking in the model but are in the texture.

But for now I'm going to let that percolate while I get on with the arms since everything in the arms are mirrored it's a two for one win but also means long runs on the MDX40a so knocking them out is a priority.

With that I've finally arrive at the tile of my post (for some semi rhetorical brainstorming). So the HBK elbows are very slick dog leg design that allows for a stubby arm but still lots of reach (kudos to Alex/Flyingdebris)

I can offer some insight of the design consideration process that happens for most parts. This comes down to a heart vs head choice vs compromise;

  • My head says stick with a simple single balanced joint because of the limitations of resin. Resin is a soft material that wears easily and prone to snap. Getting the joint to articulate in 2 positions is a novelty but keeping that joint tight isn't going to last long. Doing it might result (over time) in dangling arms. The down side of the single joint is restriction in range of movement. Space is tight and probably only allows for a few degrees of movement that would translate to about 6 or 8mm traverse at the hand which with the shoulder rotation is passable.
  • My heart says make it at a doglegged because its a nice detail. It would be very simple to design and would make it much easier to machine since the forearm wouldn't have to be a clam shell. I could use magnets to lock the arm into couched position and still allow it to flex. This is all great for me since I only display my models and I'm careful when handling them.
  • The third option is to make the joint but with a tab on the rear joint that locks the elbow to the forearm in the couched position and should be glued. But for those that want too it can be removed to allow free movement. This has the befit of both worlds but would be weaker than option 2 snapping from heavy handling or inattentive assembly are the risks.

I'd probably go option one if it was just me but, I have to consider how others might treat the model (say in an office environment) and their ability to repair should it break. Option 3 seems most logical choice.

And here's the detailed arm with various aids for modelling attached
  • the cylinder represents the arc the shoulder rotates through (the hunches will have to at least this much clearance)
  • The thingy in front of the cylinder is used as reference in rotating the arm when looking from inside the torso so I can see if there's any collision
  • Spare elbow for trying out different variations.
 Anyway enough time spent yakking to you lot time for some more eblow grease!