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pic: 4242 Preliminary CAD 1
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I really like the ramp idea. How much have you prototyped that/ how well does it work?
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Have you done a stress analysis of this yet? I don't know the material used, but looking at the design, the thought that when you try to lift a stack of totes, your elevator at the top might begin to bend depending on a few factors. I'm a programmer, though. Take this with a grain of salt.
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I'd suggest making your elevator car a little taller to space the carrier wheels out further. This will decrease the chances of having any sag in your manipulator when you have a full stack.
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It would all depend on the material being used, and the orientation it was being used in. Also, how high the support from the back is up the side rails would be important. I did some calculations with an engineer, and we figured it out that the maximum load the robot (assuming 6 tote or 5 tote bucket and noodle capabilities) would be holding, cantilevered at 6' in the air, would be ~400 foot pounds... Make sure your material is all good and the supports will hold it and you should be set. :yikes: |
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That was really my only fear for robots this year as far as damage; could they handle the torque of picking up a stack of n totes + the bin and not get deformed over the course of the season?
Side note: I think demos of robots this year will actually be pretty cool if they can either lift a lot of weight, or stack autonomously, or both. There is also the concern of center of gravity, as eddie12390 has pointed out. I haven't been around frc long enough to see robots fall over because of game piece weight, if it has even ever happened. |
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For totes cantalievered like 14" out from the front of the robot, I only get arounf 70ft-lbs for a 60lb load. I though you were only supposed to consider the X-distance, not the Y height for torque caused by gravity. Could you please share your calculations? |
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Thanks for all the replies! |
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The load is not cantilevered the height of the elevator. The number you should be using for your moment arm is the horizontal distance from the center of the carriage to the COG of the load (something like 12-16 inches). Multiply that distance by the weight of the load (60 lbs we'll say) and you get something like 720 - 960 in*lbs (60 - 80 ft*lbs). It appears everything is made from 1x1 8020 extrusion. It's pretty beefy stuff and the elevator appears well-supported. I wouldn't anticipate anything horrible happening to it. I probably would make the carriage taller though (as someone else mentioned). |
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I have realized my mistake... ::ouch:: I was assuming the wire would be pulling from the back of the robot, and the bottom tote would be at the top of the "pillars". I was calculating the wrong Moment of Inertia and wrong placement... I'll redo that. ::rtm:: Sorry for the confusion. :confused: |
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Second, I would put a cross support. Doesn't have to be directly on uppers but maybe on the angled back support braces. Lastly, I love the ramp idea. I would look into seeing how you can stack them quick from the human loader station. Maybe by having a ramp with pistons on bottom that let one slide to floor then it raises up enough to clear first tote and slides the second tote right on top. I know our team will be looking for those robots that can make quick pre stacks. -Ronnie |
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Roller Chain Tensioners on our carriage to tenison it. One or both of the lift axles are going to be on adjustable flange bearings on the tslot. Do you think this will be sufficient to tension the chains? RE the ramp - Right now, this ramp would only be able to make 1-stacks oriented in a consistent way for others to pick up (basically removing the inconsistencies of the chute). Although, one of our original designs was an articulating conveyor that would make quick 2 and 3-stacks from the tote chute but we nixed it because we didn't have a strong way to drive the cantilevered conveyor and grip was an issue. |
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is that a two or three stage lift, and what the goal for stacking, due you really need to go up past the secound level with two totes?
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-Ronnie |
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Is polycarbonate (Lexan) not available for you? It will not shatter or crack.
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