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Repurposing a Used Endoskeleton

A project log for My Advanced Realistic Humanoid Robots Project

Building bio inspired realistic looking humanoid robots to do chores and sports and stuff.

larryLarry 10/12/2024 at 04:210 Comments

So today I went ahead and extracted this metal skeleton from a male love doll I had bought some months back to use as a base form from which to sculpt the appearance of another robot.  Just to clarify upfront, this was never purchased for any sexual purposes—strictly for its materials.  I bought it mainly wanting the already decent human appearance it offers in the TPE body and face that can act as a starting point for sculpting a robot. This is better than having to begin sculpting from scratch in clay and making a mold or w/e. Just a shortcut for me. I bought a decent used male love doll for a few hundred dollars which was a bargain to say the least. The shipping alone had to be close to $200+ so it was priced WAY below the cost of the raw materials if I were to try to buy 50lb of TPE rubber. I intended to melt down the massive amount of TPE rubber once done using it to assist in the sculpt of another robot and use that melted down rubber to create the skin for a robot. So those ideas were I had planned for this doll. However, now that I have decided to use the skeleton for a robot build - now I'm REALLY maximizing that little investment! So after 4-5 hours of carefully removing the skin from the frame, I have it all off. I made a few tears here and there in the doll from rough handling during the skinning process and the lack of experience at this, but it went well overall. It was a very physically demanding job to separate the skin from the frame since you had to pry at it, cut it, and peel it and the whole time it fights you wanting to snap back to its original shape. I am quite sore but glad I got it done in a single day.

Here's a photo of the skeleton I just extracted and will be modding and using for Dinah:

Now, having gotten the skeleton out and analyzed it carefully, I noticed it does not have the ability to shrug, so I'll have to add a hinge on both sides to enable that movement. Also, its bar where the tibia and fibia would be is not proportional in length to the bar that acts as the femur. I can see that they made the doll taller by just adding length to the tibia/fibia bar rather than proportionally adding height throughout the robot. So its proportions are off due to their laziness or oversight. In any case, I have to modify ALL the proportions some I think to match the proportions of my Eve base mesh sculpt. The neck is also quite hard to bend so I might have to add a couple hinges to it. All the nuts for every hinge on it are welded into place to prevent them backing out so I will have to grind off all these welds so I can loosen the nuts to disable posing and instead have all joints freely moving to reduce friction. I will have to add proper fingers and a palm. I will 3d print these bones for the fingers.



TheRobotStudio is using Feetech SC0009 servos for the fingers. I'm planning to substitute in three N20 66rpm motors in place of each Feettech SC0009 servo. By combining three of these N20 motors, I am able to surpass the total torque of the SC0009 servo but after factoring in the size of our respective output winches, mine will be about 13% slower than his. This is fine by me because his robot hand designs are always extremely fast in finger speed and I can get by 13% slower than this. The purpose of swapping in N20 66rpm motors for the Feetech SC0009 motors is to cut costs and I just have a ton of them already and have been itching to use them. The Feetech SC0009 servo is around $11 and my N20 66rpm motors are only around $0.80 so 3 of them is $2.40. So that's $8.60 saved ever time I do this part alternative strategy. Well the savings is a bit less since I then have to supply my own motor controller H-bridge chip and potentiometer to read joint angle. So maybe only $8 saved. However, from what I gather, the Feetech SC0009 requires a serial adapter board to run it and doesn't use PWM but uses serial. I do NOT like this AT ALL in terms of my preferences and the adapter boards were $13 each and only serve 4 servos. That will add up quickly. So I'm actually saving that cost too. I prefer my microcontrollers to pwm directly to the h-bridge with no middle man software whatsoever to maximize my control.

TheRobotStudio is using 3 different sizes of Feetech servos in his approach. You can see the wrist servo is much bigger in his CAD model. I am operating under the assumption I can cram TONS of these little N20 66rpm motors and use more than one of them per joint. So I can use as many as I need to get to the torque I require. I will use L298N motor driver h-bridge chips with these N20 66rpm motors to drive them. This chip can safely power 2 N20 motors per channel and has two channels. It's VERY cheap maybe like $0.15 per chip I think - don't remember. I'll use Arduino mega to send out the pwm. I'll use 10k ohm 3 pin wheeled potentiometers to read the joint angles and these will be coupled to the joints by fishing line which will translate the joint angles over to the potentiometers whose values will be read in by the Arduino Megas. So a lot of my own designs for control and sensory input I'm sticking with for this project but using various elements of Hope-Light for a hybrid approach and swapping in different actuators whenever I feel inclined.

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