BendyTech Excavator - No DLC, No Mods

[Servo]

Full Stock Excavator

Four degrees of freedom, just like the real thing. All hinges utilize bending parts to create hinges and servos

I feel like my reputation comes mainly from my stock replica planes, but mechanical builds of all kinds were my first love. Recently, I've been developing a new method of creating stock hinges that we're calling BendyTech. It's kinda a big deal (it even has its own forum thread)

To show off the power of this new tech, I decided to make the most ridiculous thing I could think of. So I built an excavator.

 

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User Manual

Download Link: Download link: https://kerbalx.com/servo/Excavator

Controls are as follows: 

Quote

GEAR - Enable Hinges, decouple support structure

WASD - Drive

BRAKE/0 - Brake/Parking Brake

AG 1 - Step Waist Rotation 22.5 Degrees
AG 2 - Reverse Waist Rotation Direction

H/N - Shoulder Rotation Out/Back
J/L - Elbow Rotation Out/Back (touchy)
I/K - Wrist Out/Back (slow, low motion)

Each of the hinges behaves a little differently, so take a little time getting used to the responsiveness of each. The servo can be rotated fluidly if you time it right, but each of the other joints are somewhat slow to respond, due to the limited actuation speed of the control surfaces. This is only a real problem on the elbow, which can easily clip into the arm. Fortunately, this doesn't break anything, and can easily be reversed.

If anything breaks out of its hinge, return each of the arm joints to neutral and then use time warp (if able) to reset the joints.

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Under the Hood

Waist Rotation

Originally, when I was first conceptualizing uses of BendyTech, I didn’t imagine that it would be possible to exceed the rotation range of a single part, much less be able to create controlled 360 degree rotation. But, through a clever arrangement of elevons and choreographed toggling of Same Vessel Interaction, each RCS ball can be passed forwards to the next elevon in the ladder, allowing 22.5 degree actuation precision. Adding a second set of RCS balls strengthens the hinge and locks it into a single position, instead of flopping across the 22.5 degree range.

Interestingly, this drive abuses the way that KSP’s physics engine calculates bending to allow for unlimited rotation with a finite spring. The core theory of computational structural analysis is Strain Energy Minimization, which tries to find the arrangement of parts which are the least stretched. Once the craft has rotated 360 degrees, there are two possible arrangements for the spring: rotated 360 degrees, and rotated 0 degrees. Because the game doesn’t have code to account for people bending something 360 degrees without breaking it, the physics engine simply takes the less stretched position, and the parts snap into place, ready for another rotation. I wish I could say that I planned for this to happen, but it was just a lucky accident.

Video below:

Spoiler

Servo download: https://kerbalx.com/servo/Servos-Servo-Servo

 

Shoulder/Wrist Rotation

Each of these joints is the simplest form of bendy tech, using elevons to push smaller parts, similar to what is shown to the right. Each is strengthened by a thermometer hinge, which helps redirect the motion into rotation.

Elbow Rotation

Another very basic BendyTech technique here, albeit one that abuses a current bug in 1.8/9 where adjusting the Airbrake deploy angle using axis groups can extend it far past the intended limits, in both directions. It’s a cheap, dirty, way to get a large rotation angle in a small package.

This element takes full advantage of the single-craft nature of BendyTech, since the best way I found for the airbrake to be set up was attached to the rotating element. Just another way that BendyTech represents a major upgrade over classic stock tech

Video Below: 

Spoiler

 

 

Craft Download:

https://kerbalx.com/servo/Excavator