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#16
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Re: Design Help for offseason bot
Coming in a bit late to the party, but I'll try to check everything:
From OP, for future reference, in lengths more than about four inches, bar stock should only be used for tension elements. If the item will be under any sort of compression or torsion, go with angle or channel (or, though I've not designed with it, sheet metal with appropriate bends). I'm not entirely sure where the "initial robot" ends and the "new robot" begins. For sanity's sake I'll assume everything after "We are using a spare chassi[s]" is all about the new robot. You refer to rotating the mecanum wheels sideways, and Kevin Leonard advised negatively. Unfortunately, the graphics provided do not really provide any idea as to how the wheels/gearboxes/bearings were attached to the frame in the first place, nor how they are mounted now. Perhaps he has more info. 3946 used Mecanums for Aerial Assist (we vastly underestimated defense!), and the key elements to make mecanum work from my experience are:
I can't figure out this quote - the bottom line is that bar stock cannot support compression or torsion, only extension. If the concept of swapping out the bar stock with cable gives you the creeps, bar stock is probably not the right answer. Quote:
What do you mean by "webbing"? 3946 used chain, as we did not have ready access to long loops of timing belt, but we knew that we could extend 10' lengths of chain with master links as long as we needed. We used two chains to provide torsion control in the "roll" dimension. With sufficiently robust rollers to handle this torque, this would not be necessary. We did not trust our ability to make such a system, and decided to use two chains. Sorry, but the Ri3ds seem like years ago now. Even after I went back, I'm not sure exactly what you're talking about with Ri3d Indiana. Last edited by GeeTwo : 07-05-2015 at 14:35. |
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#17
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Re: Design Help for offseason bot
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20 used the VexPro Clamping Gearboxes with the Mecanum wheels in a WCD-style setup. Personally, if I were to design a simple off-season robot this year, I would use the KOP chassis, an elevator with Ri3d Indiana tabs and a 1325-style tote-catcher or a ramp. Super-simple, and very effective. Good luck, and if you have any questions about our drivetrain setup, I can try to answer them, or I can ask someone who knows more about it than I do. |
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#18
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Re: Design Help for offseason bot
The biggest draw back to a tethered ramp to me is it removes your ability to help out in the can wars. There were several times this seasons that we thought of going to that solution but we rejected it every time because we knew the can grab was going to be important at championship.
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#19
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Re: Design Help for offseason bot
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#20
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Re: Design Help for offseason bot
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#21
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Re: Design Help for offseason bot
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#22
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Re: Design Help for offseason bot
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There is a lot of focus on making sure rollers are tightly toleranced in elevator design, but don't forget to make your structure tightly toleranced as well. Our structure was a little bit out of square and it caused a lot of flexing and bending. |
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#23
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*deleted
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#24
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#25
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Re: Design Help for offseason bot
In addition to the videos that Todd linked to, you may want to study the "Strategic Design" YouTube video posted by Karthik before you really get started. It may also be of benefit to study game videos and compare the driving characteristics of robots with long chassis vs. that of robots with wide chassis, especially when traversing the scoring platforms at an angle. You may also notice that many of the fast HP stackers (i.e. the Einstein winning alliance) did not need ramps tethered to their robot (or a third robot).
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http://www.chiefdelphi.com/forums/sh...d.php?t=136979 Quote:
The reliability that you are after has as much to do with the quality of construction as the design of the robot. Your team may want to look at the construction practices (mechanical and electrical) in the off season and make any necessary improvements in the off-season. Your off-season robot can be the final test for any training you do. Monochron's comments about the lift are spot on. Or lift mechanism was built crooked and when it was first installed, there was so much friction it had to be forced up and down. I highly recommend the "Electronics Tutorial" videos published by Code Orange. We had ZERO electrical problems this year through two Regionals and Champs. http://www.teamcodeorange.com/tutorials-electronics.php Last edited by philso : 07-05-2015 at 18:21. |
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#26
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Me and a few other students analyzed this game quite a bit. Ill definitely watch those videos though. Thanks for the help just a quick question. Best way of setting up chain to work with this system. The middle is off limits due to it being part of the ramp so we would have to have chains at the corners. Do we need it on both sides how would we set up the shaft running through the top. Is back drive a big issue and should we plan on having to set something like a bike brake. And since we never have done chain any tools we need to buy. Thanks |
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#27
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Re: Design Help for offseason bot
hello everyone,
so we have ordered all of our parts and I have a few questions but first what we ordered Vex $125 Flanged Bearing - 13.73mm (1/2" Tight Press ThunderHex) x 1.125in x 0.313in (11-pack) 1/2" ThunderHex Stock (3 feet) x2 #25 Sprocket w/ Hub - 16t - 1/2" Round ID x6 Clamping Shaft Collar - 1/2" Hex ID x4 #25 Heavy Duty Master Link x10 Competition robot parts $50.00 $50 dollar version including rollers and roller hardware Pitsco Tetrix .25 chain Tetrix max chain breaker tool Andymark $430.00 Planetary GearMotor Bracket (am-2197) x2 PWM Connector Kit (am-2817) Logitech Extreme 3D Pro USB Joystick (am-2237) Assorted Heat Shrink Tubing Kit, Red, 127 Pieces (am-2861) REV Robotics 1" Extrusion, 6ft (am-2901) x3 Assorted Rev Extrusion Brackets x36 REV, 3/8" bore V-groove Ball Bearing (am-2914) x4 #25 Connecting Link for Roller Chain (am-0371) x10 040.5-DP Bimba Air Cylinder w/ nut (am-0292) Grainger $800 I dont have the full list but it included 1x2 aluminum tubing 6ft x6 1x1 aluninum tubing 6ft x4 1/4 inch rivets lazy tong rivet tool and a crap ton of heavy duty steel corner braces for structure. is all that good enough to build the robot specifically the chain parts as we dont have many parts spare in the shop. I saw screws that went through chain to connect it to the elevtor what is that called. We are trying to something similar to team 3940. thanks |
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#28
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Re: Design Help for offseason bot
If you're using #25 chain, buy the Dark Soul chain tool from team 221. It allows you to break and reconnent #25 chain without using hardware.
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#29
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It's out of stock which is why we bought the other chain tool.
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