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#16
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Re: FIRST provided transmissions survey
Our team has gone for designing our own transmissions for the last three years. The first was a Crab Drive, so we didn't really have a choice about using the kit tranny. The second was using the 3 inch CIM with belts attached, and was a 2 speed ball lock. The third was this year's 2 speed dog shifter, with 2 small CIMs.
I'd say that this year was our most successful year, and here's why: We spent a lot of time simplifying the game. We realized that you'd need to get tubes from A to B, and built the simplest possible system of doing so. We also realized that in order to maintain a competitive edge, we'd need the shifting capability. As for the resource issues, here's my suggestion: The only drivetrain useable machine tool that 114 has is a Mill with a DRO. However, we end up with nice welded frame bots, with CNC'd drive systems, and very advanced parts. How do we do that? We go around to local shops, ask them if they can help us, either by cutting cost, or donating machine time. It's a bit of work, but in the end it pays off wonderfully. |
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#17
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Re: FIRST provided transmissions survey
By the way, the BaneBots transmissions this year (before the issues were resolved) were close to the worst ever, second only to the drill motor trannies used pre-2005 (if not worse). The 2005-2006 trannies were really good, and were almost exactly like the AM single-speed. (Hey, I'm biased--we won the championship with one set of KOP trannies that year.) This year, my team just used AM 2-speed pneumatic trannies. Our driver seemed to like them better than the single-speed ones, and the robot performed just as well.
However, I'll echo what others have said: it depends on the game whether or not your new tranny design is actually used. Suggestion: use an old robot/Kitbot, build a mockup with the new design, and put it through the mill before or after the season if at all possible. This will help determine what the tranny can and can't do. Then, figure out what you want the drive to do during the design time, and match a drivetrain to that. |
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#18
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Re: FRIST provided transmissions survey
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But if you have the capability to make those carrier plates (try cutting that double-D hole with a CNC) then you have the capability to make your own transmission. Between the 2007 provided transmissions and designign your own, I'd definately say design your own. Those 56mm Banebots transmissions didn't cut it. The smaller ones worked great, we've been using them since build season throughout all of our competitions without problems. 2005 and 2006 kit transmissions were fantastic and I'd say go with them if you didn't decide that a shifting transmission was necessary. However, that's not an option anymore. And everyone else has already said what needs to be said about buying transmissions. |
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#19
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Re: FRIST provided transmissions survey
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One thing I forgot to mention earlier that I tell my team; In the recent years robots are either playing defense, or being defended. It's best to build a nice base that can play defense even if you plan on being an offensive robot because; a) If you've got a powerful base w/ nice traction, it will be harder to defend you. b) If your manipulator breaks or playing defense fits your alliance better, you can play defense. That was our philosphy for this year. We could put 5-6 tubes in a good match (after we redid the arm, and good matches didn't come often ), but we fould ourselves playing defense much more. |
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#20
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Re: FRIST provided transmissions survey
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You don't need a shifting transmission to play defense. Simply getting in between an opponent and their target is enough to keep that opponent from scoring. Also, a good clip on the corner can knock an opponent off target for a little bit. A lot of the time, I see wheels spinning against the carpet, meaning teams have too much torque and not enough traction. So, that extra torque from low gear isn't being put to any use. I'd say it's best to be quick and use momentum to knock opponents around. I'm not saying that ramming is the best way, even bumping starting from a couple feet away is adequate. |
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#21
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Re: FIRST provided transmissions survey
I love the first transmissions because they never break, have good power and speed, and gives team that build there own a chance to build something better then what the mass amount of teams use. The last thing i want to see is a round of 6 robots not moving because they can't build a gearbox. No one wants to win a game because of a broken robot. Not even in the finals
Edit i showed this post to a teammate that reminded me that we should go back to the old trans this years banebot tran was not up to the task like years prior Last edited by nuggetsyl : 27-08-2007 at 23:45. |
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#22
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Re: FIRST provided transmissions survey
You need to match your transmission to your strategy. Whether you use a multi-speed transmission or a single speed KOP transmission, you need to know the strengths and weaknesses of your choices and match that up against your needs for your strategy.
Many people here are against the Banebots transmissions because of the carrier plate and carrier pin issues. Fact is (like any transmission you use) you need to understand the forces being put on to the transmissions. Last year, with 4 Banebots 56mm gearboxes, 16:1 modification, 4WD, 1.2 CoF 7-1/2" pneumatic tires, we were able to successfully defend the rack against even the most potent scorers. We didn't go with the AM Single speed (only ones in our price range) because we couldn't get the 16:1 ratio we wanted and the motors would have stalled before the tires broke free. With the banebot 16:1s we only broke free at stall torque. As I said, match your parts to your strategy (or your strategy to your available parts). |
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#23
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Re: FIRST provided transmissions survey
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#24
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Re: FIRST provided transmissions survey
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It does not need to be the fastest or the most efficient or the most powerful, it just needs to be reliable. My hope is that FIRST and Banebots learn from this past years experiances and make that transmission more robust. I believe that last years transmissions were good, but FIRST teams tend to push things beyond their tolerances ... probably because we have been spoiled by having large safety margins on the mechanical parts supplied in the KOP and therefore didn't look at the material strength. |
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#25
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Re: FRIST provided transmissions survey
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The corner clip works much better, but is still risky if there are multiple targets and doesn't work nearly as well if a turret is involved. Single-speed defense, played well, can be a real pain. Played poorly, it's a minor annoyance. (These are from the team being defended's perspective.) |
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#26
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Re: FIRST provided transmissions survey
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It's kind of absurd to rank the two on reduction.... The additional reduction needed could most likely have been done in sprockets (Or did you direct drive the wheels?) |
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#27
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Re: FIRST provided transmissions survey
We used direct drive on all 4 wheels and while we could have reduced the AMs further, that would have had to have been a secondary operation (and another thing that could break).
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#28
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Re: FIRST provided transmissions survey
Teams with non-mech. experts can put together some parts in CAD to get the basic concepts down. Unfortunately the base unmodified parts also usually make your transmission heavier than the stock KOP transmission. So it's really it becomes a time trade off for me personally, since right now I lack the knowledge (and time to learn) making custom/fancy parts in CAD for a CNC. For this year I'm simply trying to figure gearing arrangements for a simple shifting transmission. I doubt we'll have a use for it in the build season since not only is it heavier than we typically desire, we can also modify the strategy during the game to make up for lack of speed (most of the mentors here seem to be better tacticians than builders, myself included).
On another note, it's a bummer to have unit-vector based algorithms for a driver-centric holonomic drive figured out (and a possible student who's interested in learning them) only to (currently) lack the necessary mechanical expertise to make it a reality -- that's why unless things change I am still comfortable sticking with inexpensive, reliable stock transmissions -- the modified banebots did very well for us this year. Plus it allows for more time on the other important parts of the robot if we decide to do an omni drive. Eventually, if they stick with FIRST long enough, mentors learn enough about every part of the robot that it becomes easier and easier to bring students up to speed each year, thereby advancing the complexity/reliability of everything. So in essence, it really boils down to the people you have that make up your team as to whether you should put the time into a custom transmission. |
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#29
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Re: FIRST provided transmissions survey
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for the shifter you're talking about, try to make a 2-speed derivation of team 33's. they made it comlpetely on a lathe and a drill press with an x-y. There isn't that much lathework, so I'm sure you could ask around to get it done if you don't have a lathe. "lack the necessary mechanical expertise to make it a reality" And for this one... that's where off the shelf can be a life saver! AndyMark.biz, ifirobotics.com (heck, even robotmarketplace), etc... all have mechanical products that can be very useful. |
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#30
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Re: FIRST provided transmissions survey
FIRST should try to continue to provide kit transmissions, trannies are expensive, time consuming and maufacturing intensive. Not all teams have the ablity to make one I think it is a great idea to provide a KOP transmission and it should be continued. Honestly with the way Andymark is going no one is going to have to make there own custom transmissions for the price, reliablity and features you can't beat them. Teams that want to make there own custom transmissions are going to make them. FIRST is always trying to improve the overall excitement and competitiveness of the events, therefore it is a good idea to provide transmissions for rookie and inexperienced teams.
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