"El Toro" is a much-loved heavyweight battle bot.  

Here is a video showing "El Toro" in battle with Lancelot and Empire Builder:

As you can see, "El Toro's" main weapon is the dual lifting forks.  Speed and power of the forks is essential for effective battle.  Recently, I've been upgrading their power, and have added elastics to the back side of the gear tracks.  The elastics store power on the downward return cycle for added flipping power. 

However, they easily exceed the resistance of the two XL motors, and the forks drift up off the floor.  I need some kind of braking mechanism that holds the forks in place when the XL motors stop moving.  What ideas do the experts on Eurobricks have?

 

Edited January 10, 20187 yr by TimberBrick

Hi, what about using a trigger-like mechanism driven by another motor, imagine it as a crossbow or a catapult, when the system is fully charged engage the trigger motor to lock the forks and when they need to be activated, just unlock or disengage the trigger motor to be able to move the forks, is a rough idea that i have so far, maybe if you could share more detailed pictures i could be able to make a digital design for such triggering mechanism, i also hope to see more about this cool creation, it looks really cool.

Thanks for engaging in my design problem.  My initial effort was to actuate a catch with a medium motor.  It was unsuccessful in the implementation shown below:

The cross block slips too easily on the pin x 3 long axel connected to the medium motor.  It was at that point that I thought to tap the wealth of experience on the Eurobrick forum.

Here is a look across the front:

There could be access to the pair of 16 t gears in the middle for a braking mechanism if the space around the 20 t bevel gear on the left is too limiting.

 

Edited January 10, 20187 yr by TimberBrick

Hi, I have tested your design for that catch mechanism and got the same problem, after making some tests i found a much more effective design, the larger crossblock, here are some pictures of the digital prototype:

As you can see, it has a gear reduction, this will also help the motor to unlock the mechanism when needed and with more torque; important note, this catching mechanism might require the motor to apply force to lock the system too, which means that both locking and unlocking are made actively by the motor, this could be seen as a disadvantage, but it could help to make continued fork movements without the need to unlock the system, i hope this works for you, i will also try to make improved systems if you need them.

Hi Imanol,

Thanks for your ideas.  I build it and discovered some interesting things.  When the catch loads the medium motor, it coils the motor gear train like a spring.  When the motor turns off, the catch releases.  I replaced the 24 t gear with a white clutch gear, and it worked.  However, the load of the elastics was too much for the catch geometry, and it would slip.  I worked out better catch geometry, and then discovered that I needed more torque that the clutch gear could provide.  Really what I needed was a smaller clutch gear so that I could multiply torque on the output end.  Ultimately, I made this gear by drilling out a 12 t gear until an axel shaft would slip with torque just under the stall torque of the medium motor.  

 

The current assembly allows me to use elastics about 3x stronger that I started with.  There is surely more development to be done.

 

 

Edited January 13, 20187 yr by TimberBrick