Hello all, I need to know how to lift up a plexiglas box with the dimensions 30cm x 30cm x 30cm. The box has no top or bottom so I am thinking of sliding something underneath the box and using a servo to tilt it up. That is an OK idea but I don’t think I will be able to move the robot around too much because the box might have trouble turning. Moving forward and backwards would be fine though.
However, I am trying to think of ways on how I can life the box off the ground and freely drive the robot wherever I want. I like this idea better because I would be able to turn the robot without having to worry about the box tipping over or anything. It seems like a quite simple task, but I have two main problems. First, the robot has to be able fit inside of the box, so it can’t be more than 30cm wide. I am guessing I could use a servo or two to make a grabber sort of thing that has the following shape:
It would be narrower at the end so it can fit on the robot, but wider at the front end so it can grab the sides of the box.
The second problem is grabbing and lifting the box. I want this grabber to be as short as possible, I don’t want to make it so it can reach the other side of the box as there will be a huge size issue. (The robot has to fit inside of a 30cm cube)
I am thinking of using suction cups but I am not sure if that will hold the box. I need a really strong grip on the box without having to reach out too much.
well you can’t be dong this for first competition because you thought of using suction cups. so i saw your picture. seems like a good idea but one problem what are you going to do about the back of the box? I would think that maybe you could use a servo on both sides to slap a suction cup to the box but then you would have to hold it’s position and then use a screw actuator…(custom made part) to lift the servo platforma few inches. this could be done using only 2 channels. but the problem is going to be what about removing the suction cups from the plexi glass? But what about a lift plate grind the edge down nice and smooth with a slight angle…( custom ) and mabe have it on a sissor type action. then you would need to be able to raise the platform again to lift. this could be interresting.
but i have to know why do you want to keep the box with you?
I really don’t want to have to use more parts than I really have to, so I was thinking of useing servos or motors to turn the servo arm platforms… This way, the whole box would tilt up. Instead of suction cups, which I don’t know if they will work or not because I would need the servo to be really fast and powerful to press them against the box, I am thinking of just using duct tape. Again, I don’t want to make it too complicated or anything, I just want to be able to pick up the box so I don’t know if the screw actuator would be the best way to do this.
I also have an extendable arm with two joints. (one at the bottom where it connects to robot and one elbow joint) It can be used to stop the box from tipping over if needed because it can go over the box, fold, and have the other part inside of the box.
I assume you start outside the box, otherwise you could just drive around inside it and push it as you go.
I assume you can extend the size of your robot outside the 30cm boundary once you start operating. If not you could still scoop under the edge and pinch the bottom edge to lift it.
It might be easiest to scoop one blade under the front edge, and use a linkage to lift another hook over the top edge and pull it back to lift.
With the correct 4 bar linkages, one motor (geared down) can likely do both actions (scoop-lift ; top hook pullback). google for 3bar.cdy to see a Java simulator that can help you visualize and design a linkage.
Self-awareness: I keep noticing new solutions by thinking about constraints:
With a sufficently low fast heavy 'bot, you could ram into the side of the box fast enough to tip it over onto the bot, ie drive under it and carry it on your back. Think about how you personally would handle a refrigerator box that was bigger than you are: side grip, top/bottom grip, push only, bottom edge lift and drag, dynamic motion…etc
You really don’t have to be able to get under the box- I think you mentioned something similar, but just in case…
Have maybe a triangle-ish shape on an arm. Think at the top of the triangle a hook (not motorized), each bottom corner have a rubber non-stick pad on there. If you hooked the top hook over the top of the box, and tilted the whole thing back, you’d pick up the box without needing to get under it. If you’re having trouble visualizing this, imagine taking a coathanger, bending the hook to the side, and then bending the corners on the bottom inward on the same side as the hook. Add rubber to those corners, and there ya go. Hook the top over the side of a box, then tilt back and pick up. The friction on the rubber parts hold the box and keep it from sliding, and the hook on top keeps it from pivoting over the rubber parts and falling off.
ahhh…another science olympiad competitor. It’s a shame…last year we gave up on trying to lift the box because in the directions, the fiberglass was specified to be something like a full inch thick on each side. We built a replica of the box that was supposed to be used and realized it was heavy for us to pick up…and there was no way the robot was going to be able to do it. We got to the competition…and low and behold, they had a box made out of 4 pizza boxes cut down to 30x30. If the judges in your competition are hardcore and you think they’ll bring the real fiberglass box, i highly recommend you avoid that route and work to drop things INTO the box as oppose to lifting the box and placing the objects inside. you would need multiple vex servos to lift that sort of weight, and even then, I bet the robot would have trouble…possibly getting stuck in an endo position with the front two wheels on the ground and the back two in the air. If that happens and the robot gets pinned under the weight of the box, your round may as well be over. Robots containing arms with an “elbow” generally prove to be the most effective in olympiad. Hope I could help!!!
