Re: 2012 motors?
 

CIMs can get closer to stall conditions multiple times before burning out. We've had BB550's & 775's smoke after a few iterations of running them around 30-35 amps for prototype lifts. I'm a bit smarter now than I was then so I can calculate for some safety margins, but for a drive train I don't think there's enough safety margin for these motors.

I think, iirc, 25 tried 2 BB550's + 2 CIMs in '08, and said they had to replace the 550's a couple of times. I think they wound up going down to 2 CIMs only in Atlanta? I could be mistaken.

Of course, I could totally be missing something; I wasn't around for the drill motors of '04 so I don't know how many of those burned out on field.

Re: 2012 motors?
 

Smaller motors , by nature, have issues dissipating heat. CIMS, due to their large size, can be run closer to stall because they can dissipate the associated heat.

A non-defective 775 should be better at running at or near stall for limited periods of time, unlike the 500 series, since, once again, its larger size can dissipate the heat that results from inefficient operation, but if there is an internal short, the resistance is less than it would normally be and the current can exceed the rated stall current producing more heat faster than the motor can dissipate it which eventually breaks down the enamel insulation on the wires and causes more shorts which causes more heating and, if it allowed to continue, the motor could potentially catch on fire.

500 series motors are much more susceptible to overheating. Their small size prevents them from dissipating much heat at all passively. Instead, they rely on internal fans to actively cool the armature. 500 series motors, as a result, will overheat if they even get close to stalling. It is best to allow 500 series motors run fast and gear them to the desired speed.

Re: 2012 motors?
 

What motors did you dislike last year?

The RS775-18 was an awesome motor, and with the ability to use 4 of them there was plenty of power on tap for many applications, including stalled-motor setups. We had two 775s on our arm (see pic below) that routinely stalled and were fine. It only took a few watts at stall for each motor to maintain position, FWIW.

Re: 2012 motors?
 

I don't understand this. If power consumption is linearly related to volume then maximum heat production increases in a cubic curve, while maximum heat dissipation is quadratic, thus a larger motor actually has a harder time dissipating heat.
What makes larger motors better at dissipating heat?

Re: 2012 motors?
 

I think he's making the case where the motors are the same power, but only differ size. Which was pretty true when comparing the 550/775 and FP this year.

Re: 2012 motors?
 

The virtue of the CIM is it's tremendous thermal inertia. It weighs about 2.8lbs whereas the next largest motor (RS775-18) is about 0.7lbs. This allows the CIM to absorb much more heat than any other motor in the kit. In a 2m:15s match it can usually get by no problem.

It also has an aluminum case that probably helps conduct heat away quite nicely, better than the steel cases on most of the smaller motors anyway. They're also bolted to other big pieces of aluminum (tough boxes for one) that are great heat-sinks.

On our arm, there were two RS775-18s, one in a dewalt transmission (plastic) one in a bane-bots transmission (aluminum and steel). The one in the bane-bots transmission ran noticably cooler because it dissipated heat through the transmission well. We did thermographics to confirm:

Re: 2012 motors?
 

Or they could write the game in such a way that such behavior is naturally discouraged. In a perfect world defense would not be a viable strategy due to multiple methods of scoring being more valuable (RP/QP/Score etc) without having to rely on clunky penalties to enforce gameplay.

Al, I also have to ask: Does anyone know if the GDC and the KOP Engineers coordinate to make sure that the game is tailored to what motors we have available and vice versa?

Re: 2012 motors?
 

I have heard talk of removing the CIM motor from the KOP in 2012 - which may be why AM has them on sale. I'm not sure whether or not this is true, but I've been playing with some other ideas for power since I've heard this.

I would say that Window Motors are almost definitely a guarantee, along with some sort of 500-series or 700-series Mabuchi/Banebots motor.

Re: 2012 motors?
 

Perfect... every year my dream of 6 hamster powered robots on a field comes closer to reality! Imagine the overwhelming cuteness!

Re: 2012 motors?
 

Talk from who?

Re: 2012 motors?
 

The larger motor casing works better as a heat sink.

Re: 2012 motors?
 

I can say for certain that the KoP team is aware of the GDC musings.

Re: 2012 motors?
 

Andrew,
Not to my knowledge. If you take a long look back at previous games, none depended on a specific motor for play. If you check (I have, obviously) you will see many winning robots over the years that had only a few of the available motors. I think one year, a robot had only three motors total. While I have several favorites that are no longer part of the KOP, there other ways to skin a cat.

I can tell you this, the KOP engineers work for Bill and Bill is part of the GDC. Kate is a KOP engineer and on the GDC. You can draw your own conclusions on the discussions across lunch and coffee in the office. I don't know how the GDC operates during game design but I would expect them at some point to build a couple of prototypes to see if their ideas actually work in practice. We really haven't had a game that couldn't be played yet so they must be doing something right.

All we really have to know is that all teams get the chance to use the same subset of motors each year. As to the rumor about the CIMs being dropped, I won't get excited until that Saturday afternoon after New Years. Remember that even if I did know the real answer I can't and wouldn't tell you. The same for the folks at AndyMark. We play by the same rules.

As to the other discussion, you need to keep in mind the power curves, operating choices and peak efficiencies. You can obviously make an FP work efficiently and make more power than a CIM run way off the curve and heating up. Remember too, the motor windings is where the I^2 * R losses mount. In every motor we use, the path for that heat is through the shaft and bearings or through radiation across the gap to the magnet structure. In some of the smaller motors, a fan moves air through the gap/armature and carries away some heat. In the CIM the case is sealed so no air moves to pull heat out of the case.

Re: 2012 motors?
 

I asked the AndyMark rep at IRI if they were discounting them in anticipation of no longer being FRC-legal. He said they were simply trying to move inventory.

If AM knew that they weren't going to be provided in the KOP for 2012 (but still FRC-legal), then the *last* thing they would do (from a for-profit business perspective) would be to put them on sale in the preceding off-season.

I'm betting/hoping that they will be legal in 2012, and still in the KOP.

Re: 2012 motors?
 

What else is the AM rep going to say? I doubt confidential knowledge goes that deep, and even if he did know they were going to be removed from the kit he couldn't exactly tell you