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About TechnicBrickPower

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    Rough Terrain Crane

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    New Zealand
  • Interests
    Lego Technic, Lego Technic MOC, Lego Technic Cranes


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    New Zealand

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  1. TechnicBrickPower

    Improved theory automatic gearbox

    HI Woodpecker. Yes good question - I didn't explain that very well in the video. The reason is that the center of the differential rotates at the average speed of the two side inputs. So mathematically we have C = (A+B) / 2. Now because I drive the center C in my layout the equation becomes A = 2C -B. So the 2 in the 2C is where the factor of 2 comes from. Hope that makes sense.
  2. Hi All, This video demonstrates an improved design of a 2 speed automatic gearbox based on a theoretical approach. Typically a Lego automatic gearbox consists of two stages namely a gear selector and a torque detector. In this video, both of these components are improved upon. The gear selector gear count has been reduced from 13 gears down to just 9 gears and a torque improvement of 40% is demonstrated via pulling on rubber bands and measuring the force using luggage scales. The torque detector is analyzed mathematically and the equations determining it's gear ratio behaviour are presented. Finally the overall improved automatic gearbox is tested and demonstrated to have a powerful second gear.
  3. This video applies gearbox, torque, and gearing ratio theory to design a prototype 2 speed automatic gearbox. First I describe the main components of an automatic gearbox, namely a gearing ratio selector and a torque detector. The ideal gear switch over torque point is described in terms of the PF motor torque and speed operating point, as well as the ideal gear switching ratio for the 2nd gear of the automatic gearbox. A technique for creating the 2nd gear is described by either adding to a differential by engaging a gear, or by subtracting by disengaging the gear. Issues around torque friction making it difficult to disengage a gear are mitigated by speeding up the gear switching axle to reduce torque. A torque detection method is shown using a differential for torque detection and driving a rotary catch back to the gear selector to change gears. A strategy is shown to reduce the torque and power loss due to the torque detector by placing it on a secondary path from the main power path. Finally an actual implementation of a 2 speed automatic gearbox is demonstrated and tested using a configurable torque generation mechanism using a series of clutch gears.
  4. TechnicBrickPower

    Torque in Practice

    Hi Horologist. Thanks for sending that link! That's an awesome looking device by Nico71 - I think I am going to try to build the tachometers - very clever.
  5. TechnicBrickPower

    Torque in Practice

    Hi all, here's a video I did where I use a 10 level torque gadget I created to run some torque experiments to help improve my automatic gearbox designs. Hope you find it interesting.
  6. Hi All, Here's a video I did on optimal gear switching ratios for PF motors. A formula presented relating the power operating point as a percentage of peak power. From this an operational power range band is defined based on maintaining a power efficiency of at least E percent. From this, optimal switching points relative to the motor torque are derived and the correct gear switching ratio determined. These are presented as formulas and graphs. The peak torque and power points are shown for Lego technic PF medium motors, Lego Techinc PF Large Motors and Lego Technic PF XL Motors.
  7. Hi all, I have created a video of some generic torque and power insights in relation to trying to create a high performing 2 speed automatic gearbox for a vehicle. The most interesting insight for me was the realization of an optimal operating point for electric motors to achieve maximum output power from the motor. I also derive the power distribution of a split path torque transfer design, and demostrate some experimental results using it. Hope you find it interesting.
  8. This video is about putting a 2 speed automatic gearbox in a test car and seeing if it will go up a steep ramp. I am not a car designer so very minimal detailing.
  9. Hi 2GodBDGlory! I did see your worm gear yes that did make me think about them for this purpose! I think you could extend the length of the wormgear and get more speeds in there. However the slow transition speed is a big issue unfortunately. Oops bad measuring on my part ;) Yeah rubber bands always slow things down a bit too.
  10. This video present a 2 speed automatic gearbox based on using a worm gear for torque detection. The 2 speed gearbox works by using the linear counter-action force on the worm gear to connect a gear to create a second speed. This 2nd speed is added to the main drive path using a differential after being passed through a worm gear to prevent back rotation when the gear is disconnected.
  11. This video presents a 3 speed automatic gearbox design that failed to work as expected. This design is based on an earlier design of a 2 speed smoothly switching automatic gearbox that worked very well. That gearbox was extended by adding another speed to the rotary catch selector however something happened I didn't expect.
  12. Thanks Emiel! My Lego Technic experience doesn't go back that far. That looks interesting - I will have to study it more to understand how it works! All I can say is "oops".
  13. Hi All, I have created a new design for a 2 speed automatic gearbox that is both smoothly switching and compact. The best of both worlds. I don't know if my new (for me) technique has been used before so welcome your feedback.
  14. TechnicBrickPower

    8 Speed Gearbox using just two levers/selectors - for @SNIPE

    Yes here they are!
  15. Hi for those interested I have put the build instructions for my "smoothly switching automatic 2 speed gearbox" on rebrickable: Here's the video about it: