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…
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
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.
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.
We really couldn’t tell, mainly because 2 of our 4 motors were spares left over from last year!
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.
We found that CIMs that have repeatedly been overheated get significantly weaker and slower.
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…
Fun fact: The only difference between the motors is the serial number. We ran both on a bench test, and both were within acceptable factory variations. I don’t understand this rule, but it IS the rule, so you SHOULD follow it.
Well, unless you honestly don’t know which one’s a 2008, 2007, 2006 because they all came out of the jumble in the cardboard box in the shop marked CIMs. :ahh:
-q
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.
Yes, when motors do get hot, they lose a little bit of their magnetic force. Thereby losing power.
<R58> Motors, pumps, and, Robot Controllers from previous robots shall not be used in addition to those provided in the 2008 Kit Of Parts. **They may be used as direct one-to-one SPARE PARTS **for those provided if the provided part fails or is damaged. They can only be used if they are identical to the part being replaced.
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.