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Re: Be afraid... Be VERY Afraid
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Re: Be afraid... Be VERY Afraid
I'm quite ticked off by the OP. I hate to criticize a first day poster, but this is clearly a post designed only to call attention to his brilliance.
OP, here's my advice for you. Take a large helping of humble pie. There are lots of brilliant engineers and students who have been plugging away at the problem of drivetrains for over twenty years. If your "revolutionary" device is truly significant outside of FRC, that takes into account hundreds of times as many engineers for scores of times as long. I hate to break it to you, but someone has almost certainly come up with something very similar if not the same as your design. In any case, showing us only 30% of the mechanism is no way to display your innovation, real or not. Call it a teaser if you want, but do not use it to parade your supposed superiority when we really do not have any chance to guess at whatever you have CADed. Finally, in the unlikely event that you actually have come up with something brilliant, you should take heed to RC's comment. Unless you truly believe that you can pull this off during the season, don't. It sucks to have a stationary robot on the field, and this could well cause just that. I know that I'm going to get some flack (read: negrep) for this post, but I feel like it is spot on. A good designer is not arrogant. In winning designs, egos take a back seat. |
Re: Be afraid... Be VERY Afraid
What are the wheels contacting when they're not contacting the floor?
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Take a step back and relax folks. I've gotten the OP to post what he has been working on.
I have not seen what it is, so I am just as hopeful that he won't have his foot in his mouth as you are. Should be up soon. Again, ease up on the kid, he did not mean to troll, he is just new to CD. |
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The central pivoting shaft is coaxial with the second stage idler pulley, and based on the bearing locations it looks like that shaft rotates with the pulleys. It's a self-destructing mechanism! :)
I'll be interested to see what the rest of the mechanism looks like, but from the renders we can only really tell that there are two wheels that go different speeds. Keep in mind that if these are indeed wheels for driving the robot, then the mechanism will have to be supporting a lot of weight. Make sure your parts are sized appropriately! |
Re: Be afraid... Be VERY Afraid
Hey everyone, I'm really sorry for what this turned into. It wasn't my intention to seem like I'm trolling you guys. I'm completely new to this community; I made an account just to post the render. I wasn't even aware that it was so populated here at this time of year... Thankfully, Akash Rastogi found me on facebook and explained why this post was so controversial. Again, I didn't really know how things worked here at CD until Akash and others who posted here cleared it up for me.
I was hesitant to post the actual thing because we wanted it to be a surprise during the season, if the game even accommodates this drive, that is... But anyway, here's something to clear things up. Sorry about all this. I hope you guys can forgive me! ![]() |
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Re: Be afraid... Be VERY Afraid
What advantage does this have over swerve?
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First off, thank you!
Second off, sweet CAD! Third, questions/constructive criticism (see how we can do that now? :p ) It appears that there is nothing that retains the ball vertically other than the robot's weight. I can assure you that even with a level field, you'll want to address this. The robot can be lifted up in collisions (not to mention carrying it on and off the field). If this is simply not yet modeled, disregard this comment. What kind of bearings will you be using to support module rotation? What kind of traction material will you use on the ball, and ball/roller interface? Fears of slip/low traction have always deterred me from ball drive. The idea of shifting roller sizes on a ball drive for shifting is very cool, though I agree that as modeled, I don't see the advantage over a swerve with traditional dog sifters. I feel like this may have the potential to be more compact though, maybe by shifting the CIM down low, behind the ball. If there's an advantage I'm missing, please enlighten me though! The initial module you posted looked like it had a lot of promise as a traditional wheel-switching shifting design. While not totally original, your design work was sound and compact. Maybe pursue this as well. |
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Unfortunately I have to hit the sack because I have to wake up early tomorrow, but I'll back tomorrow to talk about the mechanism... |
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How big each of the modules, and how many of these modules are you planing to have, 3 or 4? Do you think that there will be enough room for the full size of the swerves plus their turning motors/gears/belts? Another possibility is to use a mouseball kind of thing with omnis, this would also allow for strafing.
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From the 2012 Manual, section 4.1.4. Quote:
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The Technokats did a ball drive in 2003, and I think Andy Baker went on to patent the idea. There's a thread on it somewhere around here.
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As awesome as this is, I would be interested in a breakdown of the pros/cons of choosing something like this versus a well-implemented swerve (a la 1717, 973, etc.). I'm not seeing any benefits, but I have only a cursory understanding of drivetrains at the moment. |
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Let me start by saying that I have also spoke to Daniel about etiquette on the forms and am happy to see his attempt at rectifying the situation. With that being said this design is by no means a finished product. We are still hard at work picking out all the little details so that we can have a smooth running drive-train for this year. In addition to that, we are not yet certain if this will even be the drive-train system that we will be using for this years game, considering we know very little to nothing about what it really is. Finally, as much as I did not want to disclose so much detail on the design we have so far this early on I suppose the design is now up for discussion. The other half of the magic is in the programming anyways ;) So have at it!!!
I'm excited to see everyone at kick-off, see you then! |
Re: Be afraid... Be VERY Afraid
I'll try to limit it to 5 questions:
1. What's the advantage of this versus standard swerve? 2. What language are you programming in, and how far have you gotten? 3. What cylinder are you using, and how is it mounted? What's the normal force between the rollers and the ball, and what're the CoFs? 4. What's the total module weight and how does the chassis interface work? 5. What experience will you have with this by kickoff? As it stands, I have to echo R.C.'s comment. I've known--and have been--a first-year swerve team. In all honesty, it looks like you're setting yourself and your alliances up for trouble jumping in on January 5th. Good luck either way, though. |
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This past summer I revived team 45's ball drive and it has seemingly lack-luster results. While it is much simpler than your current design it still doesn't perform as well as some swerve drives I've seen and driven. If you can get it working more power to you. If you want, PM me and I can send you more pictures of our 2003 ball drive robot and give you a good list of pros and cons.
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1. There are two advantages that we have seen so far. The first is a serious weight reduction as we don't need AM shifters. Also the ball will be made of carbon fiber wrapped in some undecided traction material. We also get a bit more friction if we were lets say trying to be pushed by another robot. This is due to the fact that we can put the driving wheels perpendicular to the incoming force, thus allowing the friction between the ground and the ball as well as the driving wheel and the ball. The second advantage is that we can easily disengauge the ball completely and use it as a "castor wheel".
2. LabVIEW. We have written some preliminary algorithms for the basic driving. We are now working on automating some maneuvers. 3.We still haven't decided on the exact cylinder, but will most likely use the tiny cylinder in the KOP (I can't remember the bore size). It will be mounted on a pivot point at an angle from the floor to the right of the big drive wheel. 4. We are aiming at less than 3 lbs (without including the CIM). This will depend on what materials we use (carbon fiber, aluminum, titanium). It will be a modular plugin to the chassis. 5. I have taken this into consideration, so in response, we will only be using this system if it is successfully running in a fair amount of time. |
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It looks like this ball is only powered on one axis. In that case, why a ball and not a wheel?
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Cool! Thanks. Followups:
1A. I'm missing how you get "more friction". Isn't the first place you slip the only one that matters? I guess I'm not understanding what you intend to do (in part because of Chris's question). 1B. What's the benefit of turning it into an caster wheel in this setup? 4. Wow, 3 pounds? Keeping that in-cost is definitely impressive. What's the ball diameter? |
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Again due to the weight reduction advantage. The module its self is able to rotate 360 degrees to give the swerve effect. Also this whole project is a way for us to satisfy our engineering curiosity and out of the box thinking.
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Siri,
1. You are correct in that the first place that you lose friction is the only one that matters, but since there are multiple contact points, each one adds to the total friction available. Lets suppose you see an incoming robot front the right of our robot, we would turn the wheels so that they face front to back (perpendicular to the incoming force). 2. It would simply be used as a built-in neutral position which may or not help with this years game. 3. I believe the diameter is about 4 inches. |
Re: Be afraid... Be VERY Afraid
Maybe I'm a cynic, but until this design gets the Aren Hill Seal of Approval (or at least his thoughts), I dunno that I'd put it on the field during the season. Aren has more experience with different/non-standard swerve designs than any single person on these forums. OP, I'd message him specifically if I were you.
Also, post the overarching design as a Photo to get more/better feedback -- the veterans on these forums tend to write these types of threads off as more chatter when sifting through the noise. "Be VERY Afraid" will not get you a whole lot of constructive feedback on a technical design. Presentation aside, it definitely looks interesting. |
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Beautiful CAD! But the concept I'm a bit skeptical about. What happens if your robot is hit really hard? Can the ball become dislodged? It looks like you are relying on gravity and the wieght of the robot to actually hold it onto the ball. What if your Robot CG is higher and your drive ball becomes a part of the field accidentally?
Thats what I see. - Andrew |
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1) I can see a couple of problems here. First of all I'm not sure you can get as much traction on that ball as you would wish. The common matertial that I would think of using to cover the ball is roughtop. However roughtop's performance on carbet is directly related to how much tread is touching the carpet. Second the locking system that you described can be done with a regular swerve. However with a regular swerve it is mechanically impossible for the wheel to roll, so you will have a greater resistance to being pushed. Also this whole setup is less efficient. Lastly you usually don't want castor wheels. In this setup specifically you will lose motor power. However I could see them being useful maybe on the bridge this past year.
4) A pound or two more it seems like you could do mini modules like 1625 did. This setup would be much more efficient than your current one, and for the performance gain it would probably be worth the weight. Try getting modules as small as possible. I have done it and it is a very interesting design challenge. |
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I believe I understand what you are saying, that by moving the wheels perpendicular to the incoming force, you are using the traction of the ball and floor as your traction limit as opposed to the traction limit on the wheels against the ball. What is hanging me up is the part where you say "each one adds to the total friction available". This is not a summation, your maximum theoretical resistance to pushing (or traction) will be limited by the ball's traction with the floor. -Brando |
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Doesn't a sphere give you a disadvantage as far as friction is concerned?
In a perfect spere only one point would be tangent to the ground. In a wheel, the entire width of the tread is touching the ground. Am I missing something? |
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I would not have guessed this... thought it was a re-imagining of the Nonadrive corner module... though, I'm a pretend engineer and THAT'S my excuse...
QUESTION: I don't see anything that leads to structure that holds the chassis up? Where's the shaft that this spins around on that will support the weight of the robot? I'm assuming the shaft will be on the top-side of what's shown so far... or, are you going with a "Lazy Susan" on top with this fastened underneath and attached with standoffs (like the large gear below)? |
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Hrmp. My delete button is broken.
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And listen to Jesse; you really want to talk to Aren. Tom: secret's out. OP should probably edit the original post. |
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These threads are interesting -- and we don't see many of them around anymore, unfortunately -- because they document someone's effort to make a better mousetrap. What becomes clear as the discussion progresses is that there are still lots of folks that still have a lot to learn about the forces at work and considerations we face while making decisions about how a mechanism will work. I might've appreciated this a bit more if there were not 6+ pages of attention-seeking.
As shown, this almost absolutely will not work. It appears to offer no advantage over swerve drive but has several disadvantages that swerve does not suffer. I'd like to see some math justifying ANY of the claims y'all have made re: friction, pneumatic cylinder size, etc. |
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I'm curious what particular product or material he intends to use for the ball.
You might be interested in this: http://www.autoblog.com/2012/09/19/s...eering-studen/ |
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Hey there,
I see that this idea/module was pretty much completely picked apart and shown to be a horrible idea so I won't bother with telling you any of that. Hopefully, you’re not too disappointed that the module/idea that you probably spent a long time designing isn't as great as you thought it was. I just wanted to take a second to encourage you to continue thinking, inventing, and innovating. The people on this forum just want your team to be successful. Posting your designs on the forum is a gutsy move as any new design will be dismembered by many smart people. It is also one of the best things you can do as you get free constructive criticism from a bunch of smart people that have collective experience beyond what you could ever hope to gather by yourself. Anyways, I hope you can take this away as a positive experience. If you hadn't posted on here and instead just went ahead and built your drivetrain for the 2013 season you would almost certainly be fighting your design the entire season and had a not-fun-at-all experience as a result. Good Luck in your 2013 season and your future design endeavors. Kind Regards, Bryan |
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Wow I was not expecting to see that when I logged in today! :ahh:
I do agree that this drive isn't the best choice for FRC application unless the game changed to limit robot to robot contact and it wasn't so complex. Every drive has its weaknesses. I do want to congratulate you for thinking outside the box. Too many of us get caught up in trying to keep up with the elite teams by making swerves, WCDs, octocanums, etc without really trying to come up with the something new or reinvent the wheel er... ball! Great model and design! Keep it up! :) I would encourage to keep working on this model. Maybe you could build one as an off-season/fun build project! You could even rework your wheel choice and have a sweet module for octocanum by switching one wheel for a mecanum! To everyone else. Is the design far fetched? Maybe. Are there some problems in the design? Possibly. But let's keep this as a positive discussion. Someone put a lot of time and effort into designing and modeling something cool and by keeping positive discussions going we encourage more designs to come forth instead of lurking on members' desktops in fear that we will tear it apart in our posts. Every year I dream of 8wd WCD swerves! :rolleyes: Nice work and good luck in your future designs! Brendan |
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I would say that if the module were used in FRC competition, you'd probably run into some difficulties in steering and traction, as noted already. (Aside from the potential for terrain popping the ball out if there wasn't a retaining device--I didn't see one in the model.)
But... I would suggest building one as an offseason project if you don't do it in season. Build a T-shirt cannon (or other promo device) on top of it. Offseason demobots need a "COOL!" factor, which I think this has--especially if it works as advertised. |
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I spend my free time making crazy designs like this in CAD, as such I enjoy seeing these designs whenever I get the chance.
From my personal experience. It always sucks when people criticize a design a lot. I would advise you to hear it as trying to help, rather than that the design is bad or not worth pursuing. You should still listen to most of what has been said, but I think giving up on this design would be a real shame. I know of at least one instance where a company shot down an idea in a brainstorming session, and a number of years later made that one idea the most important distinguishing feature of their technology (and it still is to this day). In my opinion FIRST would be much cooler if more teams were trying these crazy new designs, rather than just making another WCD and doing stuff purely because "its what the Einstein teams do". I hate hearing people say that a team shouldn't do something because no teams on Einstein used it. Reasons a team should use or not use those designs would be that they are what works for that team and because they would be the most effective for that challenge, not because some other really good team has done it or, the other extreme, no one else has done it. These types of out-of-the-box designs are always fun/inspirational to design and look at. I found this design inspirational and it is a beautiful CAD model. |
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Innovative is also not synonymous with good, or indicative of sound engineering. Both are important. |
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Also to the original poster of the other quote, these teams aren't doing crazy designs because of their limitations and just the amount of work and effort required to realistically do some of them. Even though the crazy and novel ideas are very cool, they usually aren't the best practical ideas that you would like to go with. |
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Okay, I have a bit more time now that I'm not at work and can list some of the questions I have about how this would work and what the benefits are.
Years ago, I was able to receive a lot of fantastic feedback from engineers on this site, so there's definitely merit to posting ideas and soliciting feedback. That should continue, but a bit of humility goes a long way. Questions/Concerns -- 0. What problems were you trying to solve when making this design? What were the criteria you used to guide your decision making process and how did each of this model's elements satisfy that criteria? 1. Do you intend for the sphere to slip sideways against either driving roller? If not, no part of the sphere that isn't touched by a roller will ever contact the ground, so why use a sphere at all? If yes, the maximum possible force of friction between the sphere and the driving rollers must be less than the maximum force of friction between the roller and the carpet; this sacrifices available pushing force, putting your robot at a disadvantage in pushing matches. 2. The sphere is driven by a roller using friction. The available force of friction will be determined by the pneumatic cylinder pushing the roller against the sphere. You can use leverage here to make a smaller cylinder provide force that nears or exceeds your practical maximum possible friction force as determined by the coefficient of friction between your roller and sphere/sphere and carpet, but in all cases, the maximum friction force the robot can exert on the ground will be dictated by the sphere/carpet interaction. 3. When a roller is being pressed onto the surface of the sphere, because there is currently nothing shown to retain the ball from moving away from the drive rollers and ball casters, your mechanism will push the robot away from the sphere, unseating it from within the four ball casters. You will now be riding only on the thin interface between your drive roller and the sphere. Driving forward or backward will cause the sphere to shift in the opposite direction. Any sideways motion will cause the sphere to slide sideways off the driven roller and, for lack of a better explanation, wedge itself into place between the drive rollers and two of the ball casters. You may not be able to recover from this condition except by going to a middle position that removes both rollers. The condition will repeat anytime you try to drive, however. You absolutely have to capture the sphere so that it cannot move vertically independently of the rest of the module for this to have ANY shot at working at all. There are a lot of problems here and I think that, if you worked through them, you'd end up at a swerve module. |
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First off, awesome concept. I really can't believe that I just spent 30 minutes reading through all of this, but it is a fantastic concept. Your presentation of it leaves much to be desired ;) but it's forgiven (imho).
Secondly, I have a question about the maintenance of it. If you have the balls held in place by something other than the weight of the robot (which I heavily advise!) replacing a ball will be difficult. Hopefully you will never need to actually replace one, but just in case.... Also, the actual balls you will use will possibly be carbon fiber? Carbon fiber is cool, that is not deniable. However, how will you make them to resist impact. I am no expert on carbon fiber by any stretch of the imagination, but I do know that it is fragile. In addition, your wheels are what takes the most weight on the robot. I understand that a sphere is ideal for force distribution, but I still would be worried about damage to your balls. Lastly, if you get this to work in any way at all, please put up some sort of video of it driving. This would be amazing to see work, even if it was not in a competition. Please keep us updated! |
Re: Be afraid... Be VERY Afraid
it looks like the small one could be a build up wheel to the big one which then shoots a foam basketball.
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Read through the thread, Redleader. The final design was released a long yime ago.
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Just wanted to say that I read every thread in this post for the past half hour, and I'm unequivocally impressed with both the innovative design efforts of the students and mentors in FRC, as well as the level of technical expertise and quality discussion on CD.
Daniel and the rest of Team 714, I think the design is impressive, the modeling is fantastic, and overall you deserve a ton of credit for presenting your idea and working through the constructive criticism on this board. Regardless or whether this is the most efficient design out there or not specifically for the application of an FRC drivetrain, I truly hope to see you follow through and make a finished product out of it (and post videos!!) ... because this is what innovation is all about. After all, FRC is the best place to innovate -- you may not get as many opportunities to do so in the workforce (in the corporate world, time is money, and innovation is time consuming). FIRST is awesome! |
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It looks like it can either be a duel powered wheel assembly either used for stabilization or for use as a shooter to regulate the distance the projectile will travel?
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That is beautiful! You'll have to let us know how well it works. And tell your programmers I'm praying for them... :yikes:
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Is this wheel device for driving over a Frisbee? One wheel up off the ground to get over the Frisbee and a second wheel to stay on the ground.
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Might a mod change the thread title or close it? This seems to be happening a lot... |
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I think it's a bluff
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