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#16
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Re: pic: Drivetrain Prototype
I would say for a team that is designing everything in CAD and understands the need for tensioning, 25 chain should absolutely be used. We have only ever used 25 chain and this past year used timing belt. The belt worked flawlessly but does require even more planning beforehand. I would definitely put emphasis on really determining what size of belt you need for the given power. All things considered, 25 chain isnt much heavier than belt and probably easier for you guys so I'd say stick with that but move to direct driving one of the wheels and a spur gear transmission ala toughbox
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#17
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Re: pic: Drivetrain Prototype
If you're using 1/8" aluminum without flanges, you might as well leave it unpocketed.
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#18
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Re: pic: Drivetrain Prototype
Hold the phone here. Why are you using 4 CIMs? I can see using 4 CIMs for Mecanum wheel, besides you have to use 1 CIM per mecanum wheel. This years limit on CIM Motors was only 5. You are using up most of them and not leaving yourself more for other things. If you used only 2 CIM Motors, one for each side, you would give yourself 3 CIM Motors to play around with on the rest of the robot.
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#19
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Re: pic: Drivetrain Prototype
Quote:
In 2009, the FRP flooring and acetal wheels had a much lower coefficient of friction, thus making a 2-CIM drivetrain not only feasible, but much better than a 4-CIM drivetrain at maximizing the potential use of each motor. Edit: If you really want to have three CIMs for elsewhere on the robot, use CIM+FP combo for each gearbox. It'll provide better performance than a lone CIM would, and depending on how it's utilized (here's where math comes back in) might just very well be able to pull off a friction limited drivetrain, especially if it's use in conjunction with a shifting transmission. Last edited by artdutra04 : 19-05-2010 at 08:59. |
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#20
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Re: pic: Drivetrain Prototype
As 254's 2004 & 2010 robots and 1114's 2010 robot (among others) demonstrated, just because there are 4 CIMs in the drivetrain doesn't necessarily mean that they can't *also* be used for other functions...
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#21
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Re: pic: Drivetrain Prototype
Quote:
You might be interested in the discussion going on here: http://www.chiefdelphi.com/forums/sh...ad.php?t=85837 (mixing Victor and Jag controllers for 2 CIMs on one toughbox) ~ |
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#22
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Re: pic: Drivetrain Prototype
Quote:
Op, my only suggestion to you is to use the Toughboxes in the KOP. Not knocking the P80s at all but why spend money when you don't have to? Also, a word of caution, a wide stance bot like this will be susceptible to tipping if your CG is too high. In a game where you have to have a large arm lifting a heavy object (2008, 2005) I would be cautious about using a wide stance bot like this without outriggers (see 118 in 2005 or 33 in 2008 for a good example). |
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#23
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Re: pic: Drivetrain Prototype
Quote:
I'll echo what Akash said. If you aren't going to flange the metal, don't put holes in it. You need that strength. (If you don't know what flanges are, I'll be more than happy to explain. Also, your bars going all the way across. You really only need them to be 1/8" wall. I would put three on top, two one bottom. Or even two on two, and two on bottom. I would also only take them across the center of the chassis and then use stand-offs to support the outer cover, done right you will be plenty strong enough. My $0.02 -Rion |
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#24
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Re: pic: Drivetrain Prototype
Looks good, but here's a suggestion: Your front-to-back wheelbase dimension looks pretty short. Looks to be quite unstable in terms of tipping forward or backward. For any wide format chassis, this is always an issue, and the wheel centers usually need to be pushed as far apart as the frame design allows. Most FRC games require the robot CG to be high enough that tipping can be a problem if the wheelbase gets too short. Perhaps you are trying to shorten this distance to enhance turning. That is a factor, but is usually not as important as staying upright.
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#25
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Re: pic: Drivetrain Prototype
Now that I think about it, you're right. this years robot had many issues with 35 chain, but the 25 chain never failed.
but still, if you take the time to tension the sprockets properly, timing belt is another option |
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#26
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Re: pic: Drivetrain Prototype
There is no question that 35 chain is more forgiving than 25. It allows for much more carelessness in design and misalignment albeit at a huge weight penalty. I would look at the systems in question on your design and try to identify the cause of the failure as it is not from the chain itself but rather the implementation.
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#27
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Re: pic: Drivetrain Prototype
Quote:
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#28
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Re: pic: Drivetrain Prototype
My team has used drivetrains that use only two CIMs for as long as I can remember (exception 2004 when we used four gearboxes) and we know that being torque limited is a major problem. In general our only problem was overheating. In the past we dealt with this by making heatsinks for the CIMs so as to prevent them from over heating. In my opinion how you choose to distribute you CIMs really dependes on the challenge.
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#29
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Re: pic: Drivetrain Prototype
Quote:
(double sprocket on tough-box to double sprocket on bearing blocks to wheel to wheel [times 2]) + (double sprocket on tough-box to wheel to wheel [times 2]) {we had a double sided drive-train and needed to get power to both sides.} |
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