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pic: New Drive System for 703
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How much does that weigh?
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That is nuts. Can you give us anything about it, how it works. That is somethin else.
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very nice, i like the design, im assuming the bottom wheel is offset?, and do i spy geardrive?, my team was contemplating doing something similar, kudos to making it work
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very nice, good work
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It looks promising, or maybe you have already tested it alot. How much does each wheel weight?
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And it turns well enough?
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It does weigh quite a bit so far, we're working on ways to bring the weight down (Cheesing the wheels, and gears and such). I couldn't tell you how much each wheel weighs right off hand but they're not too bad.
We haven't hooked up the motors yet but just from pushing it around we find that it seems to work better than our previous tread designs. More grip, it moves more freely and turns on a dime! It's nearly impossible to push sideways (a problem we had with treads) and the gearbox should provide the speed and pushing power we're looking for. The center wheel does have an offset and yes, it is gear driven, no chains or belts! :D |
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HoLy Canoli ! fourteen wheel drive? idler gears!! Expensive!! who's sponsoring you guys?
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Well Delphi sponsors us thankfully. :)
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:ahh:
I think "Holy moly!!" about sums it up. Do update and tells us how it drives once you hook it up. Also, once you figure out all of the numbers, could you tell me how much more it would weigh than your tread drive train? That's really something. |
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i am very impressed and that does not happen often. One way i have noticed to drastically reduce weight is to go lexan wheels. Get a big block of it and make the wheels, 1126 has been doing that for a few years and the base gets better and better every year.
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Won’t the wheels take more power?
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This is made of win. :D
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:yikes: :eek: :ahh: WOW...
and I loved your drive system last year, the 6 motor drive tank drive was really nice. But this is just WOW, I hope it works well for you guys this year, my only concern is the weight of 14 wheels. Great work once again from the 703 folks. |
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Niiiiiicccee... :yikes: :cool:
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What was your reasoning for the extra wheels besides being cool?
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Reminds me of 1057's 12 wheel drive from last year.
http://invisiblerobot.com/robotics/r.../p3187037.html http://invisiblerobot.com/robotics/r.../p3187045.html |
Re: pic: New Drive System for 703
wow! that looks nice:)
what motor combinations have you tested/are planing to use with it? |
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Almost as much grip as tracks minus the breaking of belts. I think it's a new record for FIRST as in most drive wheels on a robot.
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Fantastic job, I'm awe struck and I can't wait to see it drive.
A few questions:
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I must say, we done did good! lol i'm proud of my team! :D
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Re: pic: New Drive System for 703
Well. I can explain the "Why 14 wheels question" the others I'll have to get back with you on.
Basically with 14 wheels we can gear them all together, keep about the same size profile for our chassis as previous years, and having 7 wheels on each side gives us one in the middle we can use for a pivot point to help with turning (very common with good tread designs). We've actually found that this has more traction than our tracks in previous years. I'll post more info as soon as I can get it. :D For more pictures of our robot and other stuff we're up to, please visit our website at: http://www.team703.com |
Re: pic: New Drive System for 703
That looks like a tank...without the tread...(in long drawn-out voice) AWESOME...
Now if only you had done that last year with a shooter...that would have been cool... (in excited little kid voice) and then you coulda made it fire really fast, and made it fire at people, and made it into a little box, that looks like a real tank- MOMMY I WANT ONE!!!!! Awesome guys. That'll be cool to watch drive around. The "turn on a dime" might be useful depending on your strategy in the game... it's like having a mecanum drive, without having a mecanum drive... :D |
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This is definately something new. If it proves itself on the game field then their will be a new class of robots to talk about, the superdrive class.
This is really novel, since teams don't usually attempt to go beyond eight wheels and after that they go with treads. If I see it in action then I will definately consider it for next year.:cool: |
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I think that might be a record for most wheels on a drive, though I could be wrong.
That's awesome, I can't wait to see how this actually performs. Way to do something besides the norm :) How do you guys plan on driving these wheels? I'm looking at the picture and I have to say it's making me highly interested with no motors or any of that at this point. |
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My honest opinion is that looks way cool. Judging by the picture it looks relatively light - did you guys weigh that assy. to see how much weight you have left to play with. Looks like its about 20 - 30lbs. Do you plan on having all the wheels be driven by a motor on each side or only half of the wheels gonna be driven.
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OMG! What the...
For those that ask why: Why not? But seriously.. what the heck are you thinking? :eek: You are definately not in the running to be forklifted for extra points in the end of the match (no clearance at all under that chassis), so unless that's your main purpose of the missing components (making a ramp out of yourself or something) again I have to ask why??? |
Re: pic: New Drive System for 703
Here, have this piece of chalk. There's the drawing board. Use it.
How inefficient! Get rid of half those wheels; you ain't getting any better friction than you would with six wheels! The normal force is distributed more evenly with your design, and you end up with a sliding... brick. Sorry if I'm blunt, but that's how I roll. |
Re: pic: New Drive System for 703
I've been sitting here looking at this picture, and I've been reading through the responses, and thinking hard. And I still can not find any reasonable explanation for the massive quantity of wheels. While Jak's post may not have been delightfully articulated, what he said is basically true. You're not really gaining anything here, except for a lot of un-necessary weight and more failure points.
If there is some big concept I'm missing here, please enlighten me. |
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1) Spur gear drives have been proven to be quite effective in past FRC competitions, both in reliability, serviceability, and performance. (25's been doing it for years, although they choose ginormous wheels instead of 703's smaller wheels, which means they can get away with fewer intermediate gears and wheels.) 2) If they are choosing to climb other teams' ramps, there's functionally no way they'll be able to bottom out even on the steepest of ramps. Combined with those relatively short overhangs and the end patterns, I foresee them climbing anybody they want. 3) They've been drawing a lot of tread comparisons in their posts; if you want wheels to emulate treads, particularly on non-uniform terrain, this is probably the way to go. Now, there's a possibility that it is entirely far too much weight and so on, but I'm willing to give 'em a shot. (And besides, they could go "normal" 6WD if they wanted by dropping out a few wheels and bolting up some sprockets. I, for one, hope they don't have to do it, but flexibility wins.) |
Re: pic: New Drive System for 703
Billfred is right on track. 703 has not used chain or belt in our main drive system since 2003. We love the reliability and ease of maintainance that comes with an all gear drivetrain. Could we have done the same with a 6WD and got most of the benefit? Sure. But then we would have needed a whole bunch of idler gears to get the power from the gearbox to the front and back wheels. Besides, we wanted to keep all of the charactoristics of our treads but not have any broken belts. This does that. And it is cool.
The weight is a little more than our previous system. We figure that the running chassis with all the motors, wiring, controls, and battery will be about 52lbs before we add any game playing features. We're not worried about it for this year's game. The cost is actually less that the breco-flex belt system we have used in the past. The gears are cut from pinnion stock, and we make all the wheels in our school shop. Matt B. |
Re: pic: New Drive System for 703
Very Nice, Very Nice.
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At least with chain, if you chain each wheel indiviualy then if one chain breaks you still have the use of some of your wheels. But still great work, We wil have to take a better look at the design, during the off season. |
Re: pic: New Drive System for 703
If the center wheel is offset, then you have a really complex six-wheel drive. making 8 of the wheels either not touching the ground or not effectively getting traction. If they are getting traction then turning will become pretty tough depending on the amount of motors your using and then battery use comes into play. ignoring what I just said I really think it's a neat drive system.
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This looks really cool and I really want to see it drive. But just some quick questions.
How many motors are you using to power either side? Can it climb a ramp efficiently? How easiley repaired is it if a gear or wheel breaks or becomes unalinged? Otherwise SWEEEEEEEET:D |
Re: pic: New Drive System for 703
You have the problem of something breaking or falling off with any drive system, last year it was treads, this year wheels but we think that we have taken necessary precautions to eliminate, or at least minimize the chances of that happening.
The center wheel is offset but only VERY slightly, the other wheels still grip the carpet (though, granted not as well). We have done the same thing with all of our tread drives in the past so there really isn't much difference in terms of functionality. We're using 4 CIM motors to power it (2 on each side) as well as a two-speed transmission that we've cooked up especially for it. It should be able to climb a ramp as well as any other robot with tank treads (Assuming their ramp isn't made with slippery lexan or something; then it might be a bit more difficult). If a wheel breaks, it is VERY easy to pull off and replace (takes about 20 seconds), the gears are a bit harder and require pulling off the side panel but it's no more complicated than replacing a tread on one of our previous robots. Some time within the next week we hope to have it wired and running, if and when that happens I'll post a video of it for you all to see. |
Re: pic: New Drive System for 703
I have to say that even if this doesn't turn out to give any real advantage, it will still look impressive just having that many wheel on one robot.
I just hope it doesn't weigh too much for you guys. |
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you have got to be kidding me.that cannot work well. i doubt it will even turn that well-you might want to modify that design quite a bit- maybe take out a few dozen wheels.
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That looks quite cool. One thing I thought about when I saw your design is that your wheels might be in some sort of V with a very big angle, such that at each point in time either the front eight, the middle two, or the back eight wheels touch the ground.
All in all, that looks like a really cool replacement for tank-treads. -Guy |
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Upon looking at the design again (I still love it), my only concern is the side panels, are they lexan? I'm just worried abotu a side hard impact shattering them and leaving gears all over the field. But good luck to you guys!
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That's a problem easily negated by bumpers.
-Guy |
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Do you guys have a CAD team? I feel bad for whoever has to make that. Design Accelerator FTW.
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Re: pic: New Drive System for 703
So many people have asked why, and I'll try and elaborate on what Billfred and the members of 703 have said.
This design effectively emulates many positive features of a treaded drive system, as well as eliminates some of the negatives of chain and belt driven drives. The close proximity of the wheels allows for the robot to have a very, very, low ground clearance and still have the ability to climb ramps, steps, and platforms without bottoming out or high centering. The greater quantity of wheels creates more contact area with the ground, which in turn allows for a more even distribution of weight (although, still not nearly as well as a tread in this respect). The fact that all 14 wheels are driven allows for any wheels to lose contact with the ground (such as when traveling up an incline) and for the robot to still have the ability to drive. The use of intermediate idler gears instead of chain or belting eliminates the risk of the chain/belting popping off or slipping. It also may have actually saved weight depending on the size of the sprocket/pulleys and the chain run (if they would have chosen a "staggered" chain run, so that a single chain failure doesn't result in the failure of the whole side of the drive, it probably would have weighed much more than the gears). There are some cons to this drive system as well. Spur gears are slightly less efficient than chain (not by much though), but so many gears magnifies that slightly. Additionally, while failures should be far less often, if/when they do occur, it is likely to be far more spectacular and require probably a more complex fix than if they had used chain or belting (although, once again, this design was chosen to try and make sure failures wouldn't occur). Additionally, the 14 wheels themselves are far heavier than the 4 or 6 pulleys they would have likely used in a tread drive. |
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I will just add though, we figure if a single wheel came off, we have each wheel independently connected to the chassis using easy to remove pins, so if something happened to one wheel, all we have to do is pop another one in. Now if something major did happen and we lost a whole side it probably wouldn't be any harder than replacing a tread as it would require nearly the same actions to do. Every year we get progressively better at making the robot fast to repair, this year will probably see fastest repairs we've made yet. :D |
Re: pic: New Drive System for 703
A good bit of the discussion seems centered on how effective the design is in getting all of those wheels to work (e.g. no chains, etc). The real question it seems is, why have all of those wheels? The only effective answer I have seen so far is to avoid "high centering" when going up ramps.
The common response to all of those wheels is "they would give lots of traction". But will this approach be more effective in doing so than one with fewer wheels? The simple model of friction (which is what traction really is) states that maximum friction force is the coefficient of friction multiplied by the normal force (i.e. the weight pushing down on the wheels). The coefficient is a function of the material of the wheel and the carpet. Assuming that there is a given weight for the robot, this weight would be distributed over the wheels, and if there were more wheels, there is less weight per wheel. The short story is that adding more wheels in this case does not add more traction. The fallacy that it would comes from the "outdoor scenario", where terrain may have low coefficients of friction (e.g. snow). The idea here is that more drive wheels can avoid the situation where wheels slip, and the friction coefficient lessens (going from static to kinetic friction). Wikipedia has more info for those interested. http://en.wikipedia.org/wiki/Friction |
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