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-   -   Did I read <R32> Correctly? Six CIMs? (http://www.chiefdelphi.com/forums/showthread.php?t=110503)

DonRotolo 05-01-2013 21:50

Did I read <R32> Correctly? Six CIMs?
 
It seems we can now use six CIMs, or am I reading something incorrectly?
Quote:

The only motors and actuators permitted on 2013 FRC ROBOTS include the following:
Table 4-1: Legal Motors
Code:

Motor Name Part Numbers Available Max Qty Allowed
CIM        FR801-001                  6
          M4-R0062-12
          AM802-001A
<snip>



Gregor 05-01-2013 21:51

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by DonRotolo (Post 1208421)
It seems we can now use six CIMs, or am I reading something incorrectly?

Yes, 6 CIMs and up to 4 of the smaller CIM motors, an example of each is found in the black VexPro box accompanying your tote in the KoP.

Jim Wilks 05-01-2013 21:51

Re: Did I read <R32> Correctly? Six CIMs?
 
I had trouble believing that as well. Awesome!

Steven Donow 05-01-2013 21:53

Re: Did I read <R32> Correctly? Six CIMs?
 
Unless there was a typo, and until an update comes out, there are 6 CIMs usable, as well as 4 Bag CIMs or MiniCIMs!

Al Skierkiewicz 05-01-2013 22:43

Re: Did I read <R32> Correctly? Six CIMs?
 
Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

cadandcookies 05-01-2013 23:38

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1208508)
Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

Some testing may be in order...

cgmv123 06-01-2013 00:08

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1208508)
Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

17.2/(133*6) = 0.0215538847117794 hours or 1.293233082706767 minutes or 77.59398496240602 seconds. (You're welcome to dispute my math.)

And that's not including any of the 24 other motors you're allowed to use.

Raul 06-01-2013 00:21

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1208508)
Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

It is not that simple.
For example, 6 CIM motors on the drive train gives you more torque at your disposal, thus reducing the risk of stalling them. Each team has to do the math to determine what it optimal for their design.

DampRobot 06-01-2013 01:15

Re: Did I read <R32> Correctly? Six CIMs?
 
For Al (and all you electrician magician), does appying the same torque to two CIMs or three CIMs draw more current? Although three CIMs would distribute the current over more breakers, I suspect they would draw more current over all. If teams are going to be traction limited in low gear anyway, is it worth it to go with three CIMs in the drive?

Racer26 06-01-2013 03:20

Re: Did I read <R32> Correctly? Six CIMs?
 
My suspicion: You'll see a bunch of designed-for-6 motor drives, with 4 motors populated by the competition as teams need the weight and energy elsewhere .

Anupam Goli 06-01-2013 05:45

Re: Did I read <R32> Correctly? Six CIMs?
 
I'm suspecting that Banebots' 256:1 CIM gearboxes may become popular in a day or two.

Nemo 06-01-2013 13:07

Re: Did I read <R32> Correctly? Six CIMs?
 
I have an earnest desire to estimate how much our battery's voltage will drop as a result of a given amount of demand by the motors. How does one do that?

martin417 06-01-2013 13:13

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1208508)
Please read the blue box following the motor list very carefully. Running many high current motors is a risky choice. CIM motors stall at 133 amps.

CIM motors stall at at 133 amps, PROVIDED that the battery can provide 133 amps. We discovered in 2010, when we had two CIMs and one FP in each transmission, that under load, the battery sags way down, and cannot provide more than about 95 amps. With a fully charged, brand new battery, we could, on very rare occasions, blow the breaker, but once a battery had a few charge/discharge cycles, it wouldn't provide enough current to blow the breaker, even with all drive motors stalled. We actually got more torque by removing the FP from the drivetrain because the battery didn't sag as much.

apalrd 06-01-2013 13:23

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Wing (Post 1208739)
I'm suspecting that Banebots' 256:1 CIM gearboxes may become popular in a day or two.

I suspect there would be many destroyed 256:1 CIM gearboxes if that was true. The stall torque at the end of the gearbox would be ~560 newton meters.

Trent B 06-01-2013 13:27

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by apalrd (Post 1208970)
I suspect there would be many destroyed 256:1 CIM gearboxes if that was true. The stall torque at the end of the gearbox would be ~560 newton meters.

Not to mention Banebots puts a max torque spec of 85 lb-ft or 115.2 N-m of torque on their P80 gearboxes.

As for the 2 vs 3 CIM Motors, correct me if I am wrong, but based off of this http://content.vexrobotics.com/docs/...otor-specs.pdf

2 Motors at 300oz-in each will draw about 115 amps a piece. 230 amps total.
3 Motors at 200oz-in each will draw about 75 amps a piece for 225 amps total.

Because the curves are linear, total current draw shouldn't matter on number of motors. However, the motors will be rotating faster on the 3 motor setup at ~2200rpm compared to around ~700rpm because each motor has to put out less torque.

theprgramerdude 06-01-2013 14:04

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Trent B (Post 1208973)
Not to mention Banebots puts a max torque spec of 85 lb-ft or 115.2 N-m of torque on their P80 gearboxes.

As for the 2 vs 3 CIM Motors, correct me if I am wrong, but based off of this http://content.vexrobotics.com/docs/...otor-specs.pdf

2 Motors at 300oz-in each will draw about 115 amps a piece. 230 amps total.
3 Motors at 200oz-in each will draw about 75 amps a piece for 225 amps total.

Because the curves are linear, total current draw shouldn't matter on number of motors. However, the motors will be rotating faster on the 3 motor setup at ~2200rpm compared to around ~700rpm because each motor has to put out less torque.

The motors will heat up extremely quickly at those current levels, too. I wouldn't be surprised if some team that doesn't think too deeply into current levels runs a dual or even single CIM setup at 115 amps enough to effectively ruin the entire motor (demagnetization, something melting, etc.)

aldaeron 06-01-2013 14:28

Re: Did I read <R32> Correctly? Six CIMs?
 
2 questions related to the number of motors allowed

1) Do you think the rules would be changed to allow a large capacitor across the inputs to the Power Distribution Board to regulate voltage levels? Look at Figure 4-7 in the rules - the capacitor would be hooked across the wires where the text "Power Distribution Board" appears

2) Do you think in the future that they will allow two 12V batteries or larger 12V batteries (automotive instead of motorcycle) to allow for more powered motors?

Cheers!

-matto-

Racer26 06-01-2013 14:30

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by aldaeron (Post 1209029)
2 questions related to the number of motors allowed

1) Do you think the rules would be changed to allow a large capacitor across the inputs to the Power Distribution Board to regulate voltage levels? Look at Figure 4-7 in the rules - the capacitor would be hooked across the wires where the text "Power Distribution Board" appears

2) Do you think in the future that they will allow two 12V batteries or larger 12V batteries (automotive instead of motorcycle) to allow for more powered motors?

Cheers!

-matto-

Not likely on both cases. 1 12V 18AH battery has been plenty for all FRC applications when designed properly. You don't need more than one.

AhAhPatel 06-01-2013 14:39

Re: Did I read <R32> Correctly? Six CIMs?
 
how much weight can a CIM pull? just a quick question..

slijin 06-01-2013 14:41

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by AhAhPatel (Post 1209043)
how much weight can a CIM pull? just a quick question..

A better question is how much torque or how much power can it generate. See here.

ttldomination 06-01-2013 14:41

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by AhAhPatel (Post 1209043)
how much weight can a CIM pull? just a quick question..

This is dependent on a number of factors, including but not limited to gear ratios, lever length, and the method of lift.

- Sunny G.

Trent B 06-01-2013 14:46

Quote:

Originally Posted by theprgramerdude (Post 1209008)
The motors will heat up extremely quickly at those current levels, too. I wouldn't be surprised if some team that doesn't think too deeply into current levels runs a dual or even single CIM setup at 115 amps enough to effectively ruin the entire motor (demagnetization, something melting, etc.)

Yeah, someone was just asking the difference between 2 and 3. For the same torque output you will have same current consumption but 3 motors will run at higher rpm.

Donut 06-01-2013 18:11

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Trent B (Post 1208973)
Not to mention Banebots puts a max torque spec of 85 lb-ft or 115.2 N-m of torque on their P80 gearboxes.

As for the 2 vs 3 CIM Motors, correct me if I am wrong, but based off of this http://content.vexrobotics.com/docs/...otor-specs.pdf

2 Motors at 300oz-in each will draw about 115 amps a piece. 230 amps total.
3 Motors at 200oz-in each will draw about 75 amps a piece for 225 amps total.

Because the curves are linear, total current draw shouldn't matter on number of motors. However, the motors will be rotating faster on the 3 motor setup at ~2200rpm compared to around ~700rpm because each motor has to put out less torque.

Although this specific example is not advised (75 amps still blows the breakers!) what you're saying is correct. If you drive the same load at the same speed with 2 or 3 motors, then the total power used will be roughly the same. Each motor individually will draw less power in a 3 motor configuration but you still need the same total power to move the load (power = torque * angular velocity, none of which are motor dependent). There will be a slight difference in total power due to where the motors are running in their efficiency curve but I think it would be negligible for most applications.

Adding extra motors can be a benefit if you need more torque than was available with the previous CIM limit, but as Al mentioned you might not have enough power available to power that many CIMs anyway. Additional CIMs don't change how much power you can draw from the battery at one time.

PayneTrain 07-01-2013 00:15

Re: Did I read <R32> Correctly? Six CIMs?
 
Also on the subject of reading it correctly, are Fisher Price motors in the doghouse this year?

z_beeblebrox 07-01-2013 00:18

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by PayneTrain (Post 1209579)
Also on the subject of reading it correctly, are Fisher Price motors in the doghouse this year?

Yes, but the smaller CIM derivatives are pretty close to them in power.

apalrd 07-01-2013 00:24

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by z_beeblebrox (Post 1209582)
Yes, but the smaller CIM derivatives are pretty close to them in power.

CIM (real) - 340w
CIM (mini) - 230w
CIM (BAG) - 145w
RS-550 - 250w
RS-775 at 12v - 260w
FP 9015 - 190w
FP 0673 - 290w
Andyprice - 190w
And I think that's all the large motors. The FP 0673 is incredibly power dense. The less dense motors are theoretically much harder to smoke (unless you short several through their cases and the frame).

AlexH 07-01-2013 01:06

Re: Did I read <R32> Correctly? Six CIMs?
 
anyone thinking 6 cim and 4 shorty cim drivetrain geared for ~15mph?

Chris is me 07-01-2013 01:08

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by AlexH (Post 1209627)
anyone thinking 6 cim and 4 shorty cim drivetrain geared for ~15mph?

A 10 motor drivetrain would destroy your battery and end up probably moving less well than a four or six motor drivetrain.

Leav 07-01-2013 01:11

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Trent B (Post 1209056)
Yeah, someone was just asking the difference between 2 and 3. For the same torque output you will have same current consumption but 3 motors will run at higher rpm.

Just to slightly elaborate on this:

The current of DC motors is approximatley linearly related to the torque applied to the shaft, and is usually assumed to of the form I=k*T.

where I the the current and T is the applied torque and k is the "motor constant" (that's what we call it in hebrew, I imagine the name is similar in english).

so no matter how you split the torque between any number of motors, the current draw will be roughly the same (if you neglect friction, which isn't always a wise thing to do).

If i'm not mistaken, the motor's speed is also approximately linearly related to the torque, but it reduces, for example: w=3000-a*T

where w is the rotational velocity. so just like Trent said, reducing the torque on each motor would increase their rotation speed.

-Leav

Al Skierkiewicz 07-01-2013 07:53

Re: Did I read <R32> Correctly? Six CIMs?
 
Nemo,
Here are a few items for your calculations. The internal impedance of the battery is 0.011 ohms fully charged. The #6 wire is 0.0005 ohms per foot, #10 is 0.001 ohms per foot. I am trying to remember, I think Jaguars are 0.004 ohms, Victors are 0.006 ohms. So all you need to do is add up the losses and solve for Ohm's Law. Al's Rule of the Wire Foot (WF) states 100 amps in one foot of #10 or two feet of #6 equals 0.1 volt drop per foot. Starting six CIM motors would max out the current handling of the battery at 600 amps. With a typical FRC robot the wire/foot losses would be 11 (battery resistance) + 2 (four feet of #6)= 13 WF. 13 * 6 (for max battery current) would result in 7.8 volts of drop in the path to the PD. Since the power supply for the Crio drops out at 4.5 volts, this would produce a sufficient drop to reboot the Crio each time the robot started. Predictably, the 120 amp main breaker may or may not trip at this initial start but the temperature in the breaker is certain to rise at that demand. Now all things being equal, the losses in the remainder of the wiring feeding the speed controllers and the motors would prevent maximum stall currents to be reached. However, it is still likely that six CIM motors could under certain circumstance max out the current ability of the battery and main breaker. Teams did report main breaker trips last year with additional motors. My recommendation is to monitor your currents and adjust your design appropriately.

Nemo 07-01-2013 07:59

Re: Did I read <R32> Correctly? Six CIMs?
 
Al,

That's very helpful - thanks very much for posting.

Jim Wilks 07-01-2013 08:39

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by aldaeron (Post 1209029)
1) Do you think the rules would be changed to allow a large capacitor across the inputs to the Power Distribution Board to regulate voltage levels? Look at Figure 4-7 in the rules - the capacitor would be hooked across the wires where the text "Power Distribution Board" appears

No currently made capacitor is at all near large enough (in terms of energy storage) to do this.

Al Skierkiewicz 07-01-2013 09:01

Re: Did I read <R32> Correctly? Six CIMs?
 
Aldaeron,
It is unlikely that two batteries will be allowed. Batteries are not happy when connected in parallel when they don't match in characteristics. The manufacturers frown on this practice unless the batteries have been installed together and charged together from the beginning. Systems that use batteries in parallel often use Schottky diodes to isolate the batteries. However, we would need two 600 amp diodes at $100 each. The diodes would drop about 1 volt. Let us not forget that adding an additional 12 pounds is significant in our competition as well. Teams are already struggling with the 150 pounds most robots achieve. I fear we are stressing our participants with lifting these weights throughout the season.

gyroscopeRaptor 07-01-2013 09:13

Re: Did I read <R32> Correctly? Six CIMs?
 
Last year, I said "22 motors? Challenge Accepted."

30 motors? Not even going to try.

Ether 07-01-2013 10:06

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Jim Wilks (Post 1209715)
No currently made capacitor is at all near large enough (in terms of energy storage) to do this.

They exist, but would be prohibitively expensive.

Carbon aerogel super/ultracapacitors.

Also, these things are dangerous.



DonRotolo 07-01-2013 11:59

Re: Did I read <R32> Correctly? Six CIMs?
 
I was not thinking of a six motor drivetrain, but a four motor drivetrain and a CIM for the disk launcher.

The sixth CIM? I dunno, maybe a big defense fan? :rolleyes:

Al Skierkiewicz 07-01-2013 14:25

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by DonRotolo (Post 1209817)

The sixth CIM? I dunno, maybe a big defense fan? :rolleyes:

Or hover?????

Dad1279 07-01-2013 15:45

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by DonRotolo (Post 1209817)
I was not thinking of a six motor drivetrain, but a four motor drivetrain and a CIM for the disk launcher.

The sixth CIM? I dunno, maybe a big defense fan? :rolleyes:

Save a few CIMS for climbing the tower?

Herbie_3633 12-01-2013 11:08

Re: Did I read <R32> Correctly? Six CIMs?
 
I didnt read most of the posts but is there a limit of how many motors or motor controllers a bot can have this year.

Thanks team 3633

DonRotolo 12-01-2013 19:25

Re: Did I read <R32> Correctly? Six CIMs?
 
Quote:

Originally Posted by Herbie_3633 (Post 1213603)
I didnt read most of the posts but is there a limit of how many motors or motor controllers a bot can have this year.

Thanks team 3633

Goodness, YES. Please get a copy of the rules. It explains a lot, and if your robot does NOT follow the rules, you will not be allowed to compete. Really, it is very important.


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