Hi. I'm new here but I've been lurking a bit and now I've decided to make a post. I've built a large biped, through multiple iterations in the last 7-8 years. It's a decent build but I've decided I'd like to rebuild it with linear actuators as opposed to all of the current gearing used. Just like I read another poster say in some other thread here, moving the black part of the turn table while keeping the grey part stationary will add a ton of friction. This unit works pretty good, I had it posted on the lego mindstorms site before it shutdown. I also posted it to bricklink as well. I still think it would benefit from LA's, I think there would be less friction and better overall efficiency as opposed to the current 6 turntables driven by one motor.
Bricklink Destructor Page
I'd like to post pictures and such here but apparently I'm limited to 102.4kb of upload on this post. Please take a look at my post at bricklink and give me some input. There is a .io to take a look at the model.
I've also changed the zamor launcher I'm using since I built the digital model. I'm using a standard hailstorm configuration with standard magazines, I've found them to be much more reliable than the design I was using when I build the .io. I've considered building an "agitator" into the zamor mag to prevent ball jams, but the rebuild of the Destructor is priority.
Current biped info:
Walking: This is achieved by one motor mounted on the bottom center of the biped. It has an 8 tooth gear driving the turntable, which in turn drives another turn table above it and attached to it. The top turntable pulls the legs forward by about 4 studs. The turntable attached to it is responsible for driving the gear inside each leg, which changes the angle of the foot to take the weight while stepping forward. Obviously the legs are synchronized by the motor, as synchronization is very important for this model.
Turning: This is achieved by driving a turn table with a worm gear attached to a NXT motor. The is a touch sensor located by a tab in the leg attached to a gear. This is synchronized with when the foot has the weight on it, allowing the sensor to indicate when the foot will be active. At the same time we also know the other foot can rotate back to its original state if it is still in a turned state.
Weight: Probably around 1-1.5 kilo
Speed: About 40 cm /minute
Zamor launchers: Typical hailstorm style launchers. May come back to them once I can work out a way to use linear actuators for the walking portion of the biped.
What I was thinking for this build: (Starting from feet up in terms of mechanical workings)
First a rough motor idea, I'm using an EV3 to control the machine.
Motor 1: Walking/Turning
Motor 2: Gear switcher for walking/turning
Motor 3: Zamor launchers
Motor 4: Maybe instead of switching I could use this motor for turning?? Not sure yet....
Feet: This is where my current turning mechanism is. For a LA driven biped, I was thinking a possible gear switch mechanism to change from walking mode to turn feet mode for turning. Still deciding whether a LA or gear is the better for this. I'm kind of leaning towards gears due to the rotation forces needed for turning the foot. And the difficulty of getting rotational force through the leg down to the foot, while maintaining minimum torque/slop.
Walking: I still think one motor driving both legs is best due to the absolute synchronization required. One thing I am considering Is sending two rotational forces through the leg, (if feasible) one to control walking and a gearbox to switch to feet rotation. The second rotation force will operate the gearbox for walking or turning the feet. Possibly I could use the second rotation to send through the leg, knee and down to the foot. Now that I think of it maybe CV joint could do this.
Zamor launchers: Maybe they would even benefit from the LA treatment? To be looked into at a later date....
Appreciate any input anyone has. If the link doesn't work the biped is named Destructor. It's on the Bricklink Studio page. Thanks.
Edit: For whatever reason the studio page takes forever to load. It eventually does though.