TechnicBrickPower

Hi Everyone, I have just created a video about my dual function gearbox allowing you to remotely drive and change gears using just one motor - i.e. the one motor implements two functions. The gearbox implements two functions at once by exploiting the direction of rotation of the driving motor and implementing one function (driving) for the forward direction and gear changing in the reverse direction.

Hi all, This 2 speed automatic gearbox implements it's second gear by using a two degrees of freedom configuration and blocking and unblocking the lower gearing ratio path by using a switch and rotary catch. The rotary catch is driven by a torque detector and once enough load is detected at the output it is rotated 90 degrees to unblock the low gearing ratio path. Upon the path being unblocked it becomes the path of least resistance and the output gearing ratio is reduced to give a higher output torque. Alternative lower gearing ratios can be implemented in this by changing out the lower gearing path gears. This gearbox operates in a bi-directional manner - meaning the input motor can rotate either way and the automatic gearbox still functions.

Here's my 3 speed automatic gearbox using a servo motor to drive the gear change mechanism. The servo motor is activated by an electric switch which in turn is driven by a torque detector using a differential at the output. The automatic gearbox will switch to a lower gears automatically as load is detected on the output of the gearbox allowing it to generate more torque to overcome the load.

This video shows the design and demonstration of an 8 speed manual gearbox inspired by the Lego Ferrari 488 GTE model that has come out in 2021. The gearbox gearing ratios closely approximate the gearing ratios of the real Ferrari 488 GTE gearbox except that I have implemented it as a manual 8 speed gearbox instead of an automatic gearbox. Hope you like it.

An improved version of my RC 3 speed gearbox is implemented into a remote control car. This video shows three main improvements over the previous gearbox design. The first is an improvement is to replace the 90 degree bugatti stepper with a PF servo motor reducing the gearbox complexity. The 2nd improvement is to use a gear rack to replace the liftarm lever mechanism for converting angle to linear displacements. And finally the third improvement to change from using a 2 lego unit axle offset to a 2+1 offset to allow bevel gears to mesh with regular gears for the gear switch mechanism, and thereby eliminating one row of gears. The final gearbox is implemented into a basic lego technic 3 speed remote controlled car that can be driven backward and forwards and steered remotely, as well as remote gear changing between 3 different speeds.

Here I've created my first attempt at a RC 3 speed gearbox allows you to change gears up and down using a power functions remote control. The gear changing mechanism is implemented using two parallel axles each with gears arranged in such a way that shifting one of the axles to one of three possible positions meshes the gears with 3 different gearing ratios. The gearing ratios implemented are 3:5, 1:1 and 5:3. The gear shifting axle is controlled by a lever mechanism driven by the 4 state stepper from the bugatti chiron set. This mechanism in turn is driven by a medium power functions motor activated by the remote control. Hope you like it.

Thanks everyone for their encouraging comments. Hope to keep ideas flowing!

My 2 speed automatic gearbox is put to the test by incorporating it into a 2 speed automatic car. This gearbox implements a number of design principles aimed at improving the gearbox performance - namely of placing the torque detector on a separate path to the main gearing power path to reduce torque and power losses in the gearbox, and using gear disengagement to switch gears instead of gear engagement. A simple derivation is presented of the physics involved in driving up a ramp in order to determine the amount of additional torque required at the motor output to be able to overcome the gravity and the corresponding potential energy. The torque of a large power function motor is measured by measuring the output axle speed using a laser tachometer and relating that to the linear torque/speed relationship of the motor. These measurements are demonstrated for the car without any loading and with simple horizontal motion. Finally the car is put to the test by attempting to drive up a 40 degree ramp.

Hi I knew you'd like this one better ;) LOL. As you know most of my builds are just proof of concept ideas. Once I have settled on something that works well I'd look at laying it out for a specific purpose - e.g. vehicle etc. No it doesn't work in reverse - most cars only go forwards LOL! The new differential has 28 teeth on the housing - it's pretty much a regular 28 tooth bevel gear. It gives another design option which is what I like about it.

This 2 speed automatic gearbox design uses a worm gear for torque detection and gear switching combined. Some of my previous 2 speed automatic gearboxes have used a differential for torque detection to drive an orange rotary catch to switch gears using a switch component. The worm gear switches gears by disengaging one path to the input differential, thereby reducing the overall gearing ratio. In this 2 speed gearbox design the output gearing ratio is halved when switching from gear 1 to gear 2. By disengaging the 2nd path, the efficiency of the lower gear is improved due to the simplification of the gear train reducing the friction and power losses in that path. The overall power of the Lego technic automatic gearbox is demonstrated by testing it against a ten level torque generation device, as well as using a rubber band pulling instrument to measure the output pulling force for both gears. Hope you like it.

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.

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.

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.

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

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.

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.

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.

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.

Hi 2GodBDGlory! I did see your worm gear idea...so 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.

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.

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.

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".

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.

Yes here they are! https://rebrickable.com/mocs/MOC-51409/TechnicBrickPower/8-speed-geabox-using-just-2-levers

Hi for those interested I have put the build instructions for my "smoothly switching automatic 2 speed gearbox" on rebrickable: https://rebrickable.com/mocs/MOC-51030/TechnicBrickPower/smoothly-switching-2-speed-automatic-geabrbox/ Here's the video about it: