Muscles vs. Motors: Force vs. Speed

Nature loves Linear Motion.

• Your Bicep contracts (pulls). Your arm enters.
• Your Quadricep contracts. Your leg extends. Biology is built on fibers shortening.

Robotics (and all Human engineering) is built on Rotational Motion.

• Motors spin.
• Wheels spin.
• Gears spin. Nature never invented the wheel (at a macro scale). So, if we want to build a humanoid robot (or just an FTC robot that lifts vertically), we have to translate Spin into Line.

Method 1: The Spool (Tendons)

We wind a string around a spool. As the motor spins, the string shortens, pulling a mechanism up. This is exactly how your tendons work. Your muscle (Motor) pulls on a tendon (String) which pulls a bone (Slide).

• FTC Application: Viper Slides. We use cascading string lines to extend a lift 5 feet in the air.
• Pros: Fast. Light.
• Cons: If the string snaps, gravity wins perfectly.

Method 2: The Rack and Pinion (Cartiladge)

Imagine a gear rolling along a flat stick with teeth. As the gear spins, it pushes the stick forward.

• FTC Application: Linear Actuators. We use these for “Pushing” mechanisms or very rigid lifts.
• Pros: extremely rigid. No string to snap.
• Cons: Heavy. Slow.

Method 3: The Lead Screw (Ant Strength)

Spin a nut on a bolt. It moves up and down. If you spin the bolt with a motor, the nut travels.

• FTC Application: Climbing mechanisms.
• Pros: Infinite strength. A lead screw converts speed into massive force. It is self-locking (won’t fall back down).
• Cons: Incredibly slow.

Conclusion

We are still trying to catch up to nature. New tech like Artificial Muscles (Shape Memory Alloys) attempts to contract like biology, but for now, the electric motor is King. Being a Mechanical Engineer is often just figuring out the most efficient way to turn a “Circle” into a “Line.”