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Re: pic: Team 148 - 2011 - Raptor
Awesome robot, 'Ranglers. Can't wait to see it in person next week!!!
We will be up against a Raptor and a Dragon...and we look like a duck...a mighty duck... |
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http://blog.iamjvn.com/2011/02/insid...st-joints.html -John |
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The manner y'all use to extend the upper part of your four-bar is exactly like something I'd conceptualized a few years ago after I was unhappy with the telescoping mechanism on our 2005 robot. It's awesome to see that someone else had a similar idea and even better to see it implemented so well. |
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http://blog.iamjvn.com/2011/02/insid...ate-gears.html -John |
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I'm curious how you avoid misalignment of the teeth relative to each plate after assembly. Do you bolt both plates together and then cut the teeth? Do you use pins to align them and then clamp them with bolts? is it just "good enough" that you can bolt them together without any alignment aids? |
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I'm curious as to why you chose to stack plates instead of just cutting a thicker plate? I can understand if it was really thick for cost purposes, like over a half an inch, but wouldn't it be easier for a 3/8 piece to just cut one from a thicker piece of metal? I suppose if you're laser cutting then thicker aluminum isn't an option on all lasers because of aluminum's reflective properties.
I've also always been curious, are your parts lasered of waterjetted? |
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We align the plates (using a mating gear + eyeballs) and then clamp them with c-clamps before riveting. These are aluminum gears, and we figured they'd wear in happy. Again -- we were surprised how well this worked. We were expecting more hassle... but... it just works. -John |
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1. The laser does have some "blow out" which will affect the tooth profile in thicker materials. 2. Our shop stocks 1/8" 6061 aluminum, so we can get it without a special order. When I'm trying to get 24 hours turns, I try not to make our shop do anything they don't normally do for production. -John |
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Cool stuff, John!
Maybe you guys need to start up a Robowranglers R&D division to test more neat ideas like this... you can attempt all kinds of weird projects that would normally be foolish to try during a build season*. Though it sounds like your offseason work already accomplishes this. :) *cough* walking robot *cough* *cough* |
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We dislike chains that we need to worry about. This low-load application is pretty happy the way it is. |
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We've used laser cut gears in manipulators before when a small range of motion was desired but Ive never thought about using them in a drive application. Be sure to post up at the end of the season about any wear issues you encountered because otherwise it is a very simple solution to custom gears. I'll be sure to check them out at alamo.
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I wonder if there is any maximum allowance of people/teams per pit. Looks like 148 is going have a crowd. Non-stop. :) Again.
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How do you generate the tooth profiles? Does IFI just have a piece of software that spits it out, do you do it by hand :ahh: , or is there a handy SW feature that I've missed that does it for you?
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1. Pull out your handy Machinist's Handbook and sketch the tooth profile by hand. 2. Buy one of those gear profile generation programs and get it to spit it out for you. 3. Download the gear from somewhere online. bostongear.com has all their gears available online. For this year's robot we used option 3. I downloaded the gear I wanted from Boston gear, then traced over the tooth in Solidworks (eliminating splines with simple arcs, so it would import cleaner into our laser cutter's NC program). I grabbed this sketch, dropped it into a new sheetmetal part and away we went... -John |
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*Does anyone even use that term anymore? |
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http://blog.iamjvn.com/2011/02/insid...ve-module.html -John |
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Nice drive module!
for making that strange gear for the arm lifter....you could also get the arm gear from a door window regulator from a car, and trace it onto the aluminum ![]() |
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Why did you decide to ditch the drop down perpendicular omni wheel this year? I would think strafing would be the only upside to this whole switching drivetrain
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if im mistaken and it does not have a 5th omni to go side to side... here it shows the robot "auto magically" lining up to the pole. |
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There are plenty of advantages to this system. I really like this system and hope to develop something similar in the off-season. -Tim |
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I really like how the traction wheels are geared differently than the omni wheels. Simpler than shifting indeed! |
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@ Chris, you do bring bring up a valid point. However, the omni-wheels will allow for a more maneuverable robot. This is what I was trying to say. Thanks for catching that
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I can imagine that the all-omni wheel drivetrain would create a nice "drift" effect when turning around during high-speed motion, a maneuver that can be seen at about 1:44 in their video. I can imagine that this will come in handy, due to the "back and forth" nature of driving in this game, and that this may have actually been hampered by the kicker wheel.
CAD drawings that flash by all feature a kicker wheel, as well as many practice bot pictures. But all footage of the final robot seems to place the battery in the center of the robot, in place of the mass of sheet metal that (presumably) supported the sideways wheel. Also, John mentions a major change to subsystem 1 (the drivetrain) here. Coincidence? Or iterative design? |
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The original drivetrain was a full Nonadrive system, but we ended up removing the sideways wheels around Day 31 (see the blog post linked above). After a week of practice we decided it wasn't necessary. In my mind, all our work and testing since that point has confirmed we made the right decision. When we removed the middle wheel our original plan was to swap out the 4 primary omni wheels with 6" traction wheels, however... well... we were impressed with what our driver Connor can do with it. We call this configuration "Butterfly Drive." Which is a joke in reference to how this robot can be pushed sideways while on all omni wheels (obviously when we drop the traction wheels she stops floating like a butterfly and stings like a... you know.) I don't think all of it's virtues are readily apparent. I assure you there are more reasons to do an articulating drive than moving sideways. Though I realize most other teams may not value the same things we do, and as such may not make the same tradeoffs we did. We love "traction mode" and it's virtues in autonomous and driver control. We love the simplicity and modularity of this module design. We love how the drivetrain performs on all omni-wheels (super efficient geartrain + 4 omni wheels = smooth like butter). We're very happy with what we ended up with... -John |
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I remember way back to 2003, team 980 had a similar drive system in which they raised or lowered two different sets of wheels to essentially have two different final drive speeds/ratios.
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While I think its cool shifting wheels instead of shifting gears, I don't really see how it is simpler at all. A transmission is quite compact and requires a small amount of force to shift versus needing enough force to lift the robot to drop down the traction wheels. The only potential benefit I see of this system without the perpendicular omni wheel is the ability to change the center of rotation although the benefit of that wouldn't necessarily be worth the added weight of the system.
JVN given that you ended up taking out the 5th omni wheel would you stick with this drive if you could do it over or go with a more conventional 6 or 8wd with shifting transmission? |
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Utlizing COTS gearboxes and wheels, a team with a drill press (or even a hand drill), could make such a drivetrain. |
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By the way, the above blog post refers to large performance gains with the removal of the 5th wheel. What are those gains? |
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Unless, of course, you've put the CIM on the module... like 148 does... |
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This layout comes with its own set of challenges and constraints, but we like it a lot more. -John |
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![]() Side loading is not a problem, as the traction wheels are mounted conventionally with a bearing on both sides of shaft, and the mecanums are braced with sideplates/slides. Obviously not all is shown in this rendering. |
Re: pic: Team 148 - 2011 - Raptor
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http://blog.iamjvn.com/2011/02/insid...retainers.html Want to retain a flanged bearing? Drill some holes and rivet a washer over the flange. -John |
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haha fusion answered the call for awsome funchional leds check it out at the bayou regional ladies and gentlemen
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How often do you guys swap out rollers ? Did you notice any difference between riveting omnis instead of screws ? |
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On the topic of plate gears, I remembered that 1771 had plate gears integrated into their turreted shooter's hood. The entire thing was also turreted on a huge laser cut sprocket. Guess they should've published some documentation on their robots! What a dominant machine they had that year.
I'm hoping 1477 and 2415 also have some cool integrated components in the coming seasons. For anyone interested, it was a simple but pretty cool application. |
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The adjustable length four bar link is a really slick trick. I've had that sketched out in my engineering notebook since the first time I ever saw that done back in 2008 at FLR. They had an adjustable lower link to stay within the sizing rules and to tilt the gripper up, whereas you adjust your upperlink to actuate your wrist. Also I believe theirs may have been passive (gas shock) where your is pnuematically adjusted.
FRC67 - HOT from 2008 http://www.chiefdelphi.com/media/photos/30680 |
Re: pic: Team 148 - 2011 - Raptor
This robot is awesome. My first year of FRC was last year, and I remember being very frightened after seeing your promo video last year. I can't wait to see how you guys do at Alamo this weekend. Good luck this season 148, 2949 can't wait to see you guys perform at Worlds!
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You guys always impress.
Are you not worried with getting pushed too easily from the side when your traction wheels are up? How well does the robot turn when the traction wheels are down? I wish I could see your robot in person. |
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Raptor's adjustable arm is much more elegant and functional than that HOT '08 adjustable arm ever dreamed of being. |
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http://blog.iamjvn.com/2011/03/insid...ntiometer.html Our programmers accuse me of having a mental block which keeps me from designing sensors into the robot. To them I say: "BAGH!" Good Luck to everyone who competes in week 1! Raptor has one more big surprise up her sleeve which is ready to go. See you on the field ;) -John |
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Hmm. More compactness (potentially):
1. Fix 2 long VEX metal pieces to the dead axle of the arm such that one of the square holes is concentric with the axle. The hole will have to be enlarged of course. The two pieces of metal should be far enough apart that the slop is minimized, regardless of whether the potentiometer gear is cantilevered or dual-supported. 2. Attach the VEX gear to the arm, as shown. 3. Attach the potentiometer and the potentiometer gear to the VEX metal using appropriate spacing for the chosen gears. The spacing is built-in since it's VEX. 4. Profit. We've always had issues with potentiometers since we can't seem to keep them from slipping in the shafts we directly mount them to (thus needing to recalibrate them). Or the rubber band / polycord belts we make slip. It results in a bad calibration. Maybe we can try VEX this off season. Right now we use limit switches with encoders -- not too bad coding-wise, but man that's a lot of little wires to run. |
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Cross-drill a hole through the pot shaft and the mechanism shaft, and secure with a cotter pin or other suitable clip, bolt, whatever. |
Re: pic: Team 148 - 2011 - Raptor
148 just scored 2 uber tubes BY THEMSELVES in autonomous during match number 55 at Alamo! Now folks, THAT defines just how uber cool 148 are!
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Nice job!
That's two teams now that can score 2 in auto. The other being that one Michigan team that posted a video of it.:rolleyes: |
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Hey John that's a pretty cool piece of SOFTWARE you've got there. ;)
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Some video of Raptor in the elimination rounds of the 2011 Alamo Regional:
http://blog.iamjvn.com/2011/03/san-a...011-video.html Check out Final 1 for a glimpse of the week 1 national high score, and our 2 tube autonomous mode. |
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The 2012 release should be in the near future.
Correction, the much anticipated 2012 release should be in the near future, and I can't wait. |
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Aww. Got me excited over last year's robot. :(
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Replay of the last few moments: :eek: 148 released their robot already?? :confused: *reads thread* :mad: I got played. |
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I almost mistook it for the Raptor when I first saw it, becuase of the triangular frame. I wonder how it looks...:confused: |
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Sorry for the false hope guys. It is not unusual for 148 to release their robot soon after the ship/bag&tag deadline.
I will agree that it does appear to be a wide based robot. However, I would not put it past JVN and Greg to have placed a 'fake' robot in the back corner to create discussion... I am just waiting on how simple their design will be (as always, simple, clean, and effective). |
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It looks as if they have a tall bridge lowering arm or ball manipulator running up the front, then a shooter tower behind it. The image is too fuzzy to make out anything from there.
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Would it upset you all if I mentioned that this is their 2011 robot?
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