Now that Volume 1 is in its second printing and MRRF 2019 is over, I’m jumping back into Volume 2. Some of you may recall that I originally wrote one giant book, but split it into three volumes when I realized it was going to be about a thousand pages long. So Volumes 2 and 3 are already drafted, albeit as a series of chapters in a long book, not necessarily coherent standalone works.
At minimum, I have to write new introduction chapters for Vol 2 and Vol 3. Then illustrate, tech review, etc. But there’s quite a bit of editorial work I want to do now that I have Volume 1 published. Getting the first book through technical review, editing, and reader feedback has given me a better understanding of what people find useful as well as more of a vision for how to tie all the book content together into one big arc. So Volume 2 is getting a major re-org and a lot of new connecting matter to tie it all together. The basic “belts, screws, deltas” content won’t change though.
Here’s a stab at a new book outline that I put together on the plane flights to/from MRRF. It’s a draft more or less off the top of my head, don’t be surprised if the final book doesn’t follow this. Just sharing for people who find the writing process interesting.
- Foreword
- 1 – Intro
- Purpose of book
- Place in series
- Systems approach — understanding design drivers and integrating parts
- Overview of drivetrain design process
- Option 1: pick something popular and empirically tune for performance
- Pick drivetrain type (belt/screw/whatever) based on architecture
- Option 2: Understand performance requirements
- Select a target transmission ratio
- Fit a drivetrain to the target
- Preload out backlash
- Refresher of key Vol1 concepts
- Machine architecture, series, parallel hybrid series/parallel
- Coordinates, axis vs joint?
- Structural loop and structural stiffness?
- DOF vs constraints?
- Key drivetrain concepts
- Terminology – drivetrain, transmission, direct-drive vs geared, gearbox
- Resolution
- Loads – friction, gravity, accel, jump
- Power = force * speed etc
- Power conversion – rotary-rotary, rotary-linear, linear-linear, linkage
- Transmission ratio
- Actuator stiffness
- Backlash
- How to change transmission ratio
- In the rotary-linear conversion: pulley size, rack pinion tooth count, screw lead, crank arm length for linkages (sidebar why racks are not covered)
- Gearboxes (rotary-rotary)
- Compound pulleys (linear-linear)
- Linkage (any input to non-linear)
- 2 – Gearboxes
- Gearbox basics (input shaft, output shaft, ratio calc)
- Types
- Simple
- Compound
- Planetary
- worm drive
- Spur
- Helical
- Harmonic
- synchronous belt/chain
- Spur gear design well-covered by other sources such as…
- Ratio selection
- power curve
- inertia matching,
- etc (check V3C05)
- Conclusion
- 3 – Line Drive Principles
- Introduction – spinning shaft pulls a line, sometimes linear actuator pulls a line
- Define “Line drives” and types: belts, cables, chains, rope. Why chain & v-belt isn’t popular
- Traction types:
- Friction / capstan
- Anchored (sidebar: screw pulls line)
- synchronous/toothed
- Principles
- Line pull, net force in loop
- Line Path – line of action parallelism, deflection equation, pitch diameter
- Preload / tensioning
- Pulleys/spools – arc of contact, shaft loads
- Rotary-rotary pulley / drive types (endless loop gearbox)
- Simple
- Compound
- Differential
- Linear Line Drive Types
- Winch
- Split-loop (as opposed to endless loop)
- Half-loop / omega (sidebar: servobelt belt)
- Compound winch (block and tackle)
- Compound loop
- Special Line Drives
- Rotated / hybrid – corexy
- Coupled joint – rhombus, Helios SCARA
- Multiplexed
- Conclusion
- 4 – Timing Belts
- Introduction
- Timing Belts
- Construction
- Types – tooth shapes, history
- Timing belt simple & compound gearboxes
- Practical engineering
- End-terminations
- Center-center distance & loop length
- Tensioners
- Back-bending, twisting
- Toothed vs smooth idlers
- noise
- Teeth in mesh
- Tooth jumping
- 5 – Cables
- Wire rope
- Construction, torque balancing, dyform/compacted
- Coatings, materials
- Fatigue
- Polymer fishing line
- Materials – aramid, spectra, vectran
- Creep / set
- Anisotropic thermal expansion
- Spool behavior
- capstan effect
- Tracking
- Grooved spools
- Multi-drum traction winches
- Preload options (gravity pole etc)
- End terminations (knots, crimps, clamps)
- Conclusion
- Wire rope
- 6 – Screw Principles
- Introduction
- Terminology
- Pitch, lead, flank angle, etc
- Principles
- Backlash
- Whipping
- Mounting, end fixity, tension vs compression
- Efficiency / friction
- Back-driving
- Lead selection
- Conclusion
- 7 – Screw Drive Construction
- Introduction
- Types of screws (sidebar: cd drive junkstrap)
- Coupling options
- Screw drive configuration, arrangement options
- Interesting stuff: rotating nut, slide nut on rod, screw as linear rod, differential screws, screw as helical DOF
- Conclusion
- 8 – Delta Principles
- Introduction
- terminology
- Kinematics, virtual geometry
- Dynamics, constraints, DOFs, transmission ratios
- 9 – Delta Construction
- Introduction
- Arm/effector physical geometry
- Joints
- Sources of error
- Calibration
- Conclusion
- Book closing — tie drivetrains to motors in Vol3