RopeComb Launcher: A new catapult / trebuchet / mechanical launcher concept with +70% efficiency and a constant output force
Most mechanical catapults suffer from severe initial jerk followed by exponential force decay, requiring massive structure to survive peak loads while underutilizing the rest of the stroke.
I recently published an open-source passive transmission called RopeComb that addresses this by dynamically altering mechanical advantage throughout the stroke using a counter-folding pulley array.
The paper preprint is on engrXiv (https://doi.org/10.31224/7913), and the interactive kinematic solver + open CAD files are available at ropecomb.com.
https://i.redd.it/pgtu01mt3akh1.gif
Key takeaways from the kinematic model:
- Near-constant acceleration profile: Flattens the peak-to-average force ratio, maximizing velocity gain over shorter rail lengths.
- High energy transfer efficiency ($>70\%$): Converts heavy carriage momentum directly into projectile exit velocity without onboard motors or high-pressure gas.
- High-modulus line utilization: Leverages modern UHMWPE (Dyneema) lines to scale exit speeds past standard mechanical limits purely passively.
Can this be the new king of mechanical launchers ? ... I'd love to get feedback from anyone working on high-speed mechanical linkages or dynamic line systems regarding real-world friction and line-dynamics bottlenecks.
[Patent pending — US provisional application 64/124,997]