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#1
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2.5 inch cims of 2008
is it just me or were the cims from this year a little slower rpm then that of last year? we use a 12 to one ratio and it seemed like we were about 2 fps slower than our bot last year...
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#2
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Re: 2.5 inch cims of 2008
There are a lot of variables that factor into this. Did your drive train change at all? I didn't notice a huge difference. Maybe it was just a ratio difference between your drive sprocket and your wheel sprocket.
-Vivek |
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#3
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Re: 2.5 inch cims of 2008
I noticed my robot getting FASTER. But then again, I removed 5 pounds of rotational mass from each side....
Have you checked all the wiring to make sure you're not losing any current on the way to your motors? Long lengths really add up... Also, how heavy are all your moving parts? If it's lighter than last year, you should be faster. If heavier, then you'll be slower. |
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#4
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Re: 2.5 inch cims of 2008
well even just when we hooked up the cims to a battery they seemed slower. there were others on my team who think they noticed a change too. im just trying to figure out if i was imagining things... haha, i know that you couldn't use last years cims, they had a different number on them, but idk.
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#5
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Re: 2.5 inch cims of 2008
We really couldn't tell, mainly because 2 of our 4 motors were spares left over from last year!
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#6
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Re: 2.5 inch cims of 2008
Quote:
ya what do you mean we couldn't use CIM's from last year??? I've never heard of that... too late now either way i guess. |
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#7
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Re: 2.5 inch cims of 2008
We found that CIMs that have repeatedly been overheated get significantly weaker and slower.
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#8
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Re: 2.5 inch cims of 2008
they were telling teams at the Portland regional that had used their extra cims from last year to change them out for this years or they would be disqualified... it was the dumbest thing ever because multiple teams had used previous years motors... im not exactly sure what all happened, but thats what the inspectors were telling us...
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#9
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Re: 2.5 inch cims of 2008
Quote:
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#10
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Re: 2.5 inch cims of 2008
Quote:
-q |
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#11
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Re: 2.5 inch cims of 2008
This got me curious...so I looked it up...and it appears to me that <R58> implies that you can use spare motors you purchased the previous year, but you cannot use motors that were actually used on the previous year's robot.
Interesting. |
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#12
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Re: 2.5 inch cims of 2008
Yes, when motors do get hot, they lose a little bit of their magnetic force. Thereby losing power.
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#13
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Re: 2.5 inch cims of 2008
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So yes, the inspector was correct as Jim pointed out. Last year's motors, although identical, could only be used as spare parts replacments. GP dictates you follow the rule and inform the RI when asked. With the large influx of rookie teams and teams on a budget, we must maintain this type of rule. Teams were reporting to me a greater direction bias than we experienced in that past with these motor. Heat does change the power curve by either damaging the armature wiring (shorting some of the turns) or by altering the magnetic structure. Extreme heat may also damage the brush assy and warp the metal internal to the motor. Over time, an improperly supported shaft with significant side load, will also damage the bearings. CIM motors are not intended to have large side loads, the bearings are only bronze sleeve. |
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