Funny you should ask. I just re-ran the calculations on our CIM powered winch for 2013 and have them right here.
90.6:1 gear reduction. Three stages of spur gear reduction and one of chain reduction. 77% efficiency total for four stages.
The first two stages are through a Toughbox Mini, third and forth stages are custom.
The leading issue was trying to fit it on our robot .
With just a Drill/Mill to work with, we had to use .25" aluminum plate without much work done to lighten it.
Our team has used a CIM outside of the drivetrain in 2009,2010 and 2011.
In 2009 used 1 CIM for our eall polycord elevator and 1 CIM for our dumper roller. For this we used a 16:1 banebot planetary with another chain reduction that i don’t remember. For the dumper we geared the direct output of the CIM down 3:1 i think. I was not part of the team that year, so I dont know why those were the choices made but they worked well.
In 2010 we used a CIM to power our kicker. We used a 128:1 Banebot planetary which was attached to a cable spool to pull the kicker back. In theory this worked well. In execution it did not, and we did not kick a ball at all in 2010.
In 2011 we used a CIM to power our arm mechanism. The CIM was attached to a 64:1 Banebot, which then had a 4:1 reduction going up to the arm. The hard part of this design was finding a big enough sprocket to give us this reduction. The only problem this system had in execution is that during championships we blew out the final stage of the gearbox because our arm had a major shock load every time autonomous happened.
2006 - Shooter wheels for FRC176 1:1 with 4" Skyway wheels
2009 - FRC229 Custom single reduction spur gearbox for lift/shooter geared together
2010 - Winch for FRC229 Telescoping Lift ~16:1 BB Planetary with drum
2013 - FRC2168 Shooter wheel 1:1 with timing belt pulleys
No real issues with 1:1, just required custom adapters or pulleys. In 2009 it was either a single or double reduction using COTS AndyMark gears just packaged into custom plates. The planetary gearbox always worried me from a durability standpoint, I always feel safer using spur gears (even if they are designed to handle the load).
If the trend continues and we are allowed to keep using CIMS like this year I’m sure they will make their way into more of our mechanism, however I am still a big fan of all of the 500 series motors and the new BAG motor.
2006: CIM powered shooter. Two CIMs, each driving a shooter wheel directly. The shooter was plagued with issues, most of which stemmed from our inability to build something that was both lightweight and robust enough to handle the loading from big pneumatic wheels and 5+lbs of motors. Also, if memory serves me correctly, adapting to the CIM proved to be a nightmare and we ended up ruining a motor or two from improperly secured wheels.
2009: CIM powered offload belt. Single CIM through at Banebots 12:1 P80 Planetary, followed by a 1:2 Reduction (sped up). The setup worked really well considering that it was a last minute modification prior to ship. It gave us enough power to offload our maximum capacity in just under 2 seconds and was robust enough to handle system jams and constant stopping and starting.
2010: CIM powered inversion joint on a hanging mechanism. Single CIM through a 256:1 Banebot P80, followed by a 3:1 Sprocket Reduction. The setup never made it past the testing stage since it broke during the first series of tests. We found that the P80 was the weak link (of course) and would destroy itself if driven against a hard stop. Had we had the ability to design a custom spur box back then, that would have been the route to go.
2009 – 2 on the Drivetrain and 1 to run our poly-cord rollers
2010 – 4 on the Drivetrain only (Didn’t hang)
2011 – 4 on the Drivetrain only (BaneBots RS550s for our shoulder)
2012 – 4 on the Drivetrain only (AndyMark motors for our mechanical catapult)
2013 – 4 on the Drivetrain (Other uses to be disclosed after ship day, lets just leave it at we are big fans of the BAG motor so far)
2009 (1714): One CIM on the shooter, run through an AM Planetary after the first event to lower range and increase consistency. One CIM through a standard Toughbox and belt reduction for the elevator. No problems that I know of.
2010 (2791): One CIM operated a hanging winch. COTS options for high reductions were scarce, so we ran the CIM through an AM Planetary and the Toughbox Nano, with a very small diameter winch at the end. Needed a steel output shaft.
2013 (2791): One CIM through a ~900:1 reduction, another CIM is direct driving a 4 7/8" wheel. Will update with results once these mechanisms move. The 900:1 gearbox is TB3 internals followed by two VexPro custom reductions - PM for details. I think it is five stages.
High reduction gearboxes are a general challenge in FRC. In 2011 in particular, finding a COTS solution for an arm that didn’t involve a Window motor was extra tricky. For our final event, we ran a 775 through a CIMulator through an AM Planetary through a Toughbox Nano and chain reduction. Craziest COTS gearbox ever made.
CIM through custom spur gear setup to run a 4-bar in 2003. Not sure of reduction, but fairly large.
Big CIM powering a shooter wheel in 2006. Smallish reduction.
CIM-powered leadscrew in 2010 for lifting the robot off the floor.
I personally think this thread would be more interesting with motors that have more power i.e banebots or fisher price motors(which are the best motors ever imo).
2013: cim with custom 4:1 gearbox for polycord rollers/frisbee intake
2012: cim with custom 4:1 gearbox for polycord rollers/ball intake mechanism
2009: cim with custom 3:1 gearbox for polycord rollers/orbit ball intake; cim with custom 2:1 gearbox for ball dumper
all single stage
The same problem occurs with every reduction calculation…how much? Figuring this problem out, at least in our case, was relatively easy because we used the motor in similar applications, which took out most of the guess work.
Sidenote: Ask this same question with fisher price motors instead of cims. That’s where the real creativity in design will come into play because the available power in those motors. CIMS are already pretty fat motors for our applications.
You do realize that the CIM is the most powerful (and robust) motor in the kit, right? the FP and RS-550 aren’t even that close. The CIM’s peak mechanical power is 337 watts compared to 245 watts for the RS-550. The “2011 FP” is the closest at 289 watts but it was only legal for two years.
The thread is a little empty mainly because 4 CIMs has usually been the limit and most teams throw them all in the drivetrain.
2006 - Direct drive approx 5" wheel for Shooter
2009 - Direct drive 10" Fans
2010 - Approx 1:4 increase (belt drive) to power shop-vac internals
2011 - 12:56 CIMple Box to 20 tooth sprocket to power elevator
2013 - 12:18 to 10tpi leadscrew to lift robot
*For arms etc what rpm did you typically gear down to? FP, BB, etc?
if you could pick a reduction for a CIM, what would it be?*
a) We have used pneumatics for arms and arm-like mechanisms.
b) Do you mean an integral reduction? It’s so easy to interface a CIM, I would not want an integrated gearbox, especially if it is a planetary.
However, I’d love to get a bag motor with an integral 20:1 planetary (700 rpm) in the KOP each year.