2 cim vs 1 cim

[efoote868]

Originally Posted by cj3958

The downside is that they COULD overheat, but they probably wont.

In a drivetrain, a 775pro WILL overheat.
Stall them for more than 3 seconds, and they're no longer motors. Run them for more than 90 seconds at peak power, and they're no longer motors.

See actual test results here: http://motors.vex.com/775pro

[Joe Johnson]

Originally Posted by efoote868

In a drivetrain, a 775pro WILL overheat.
Stall them for more than 3 seconds, and they're no longer motors. Run them for more than 90 seconds at peak power, and they're no longer motors.

See actual test results here: http://motors.vex.com/775pro

I am not so sure about the statement above that I have put in bold.

The facts you refenced are sound but it doesn't follow that 775Pros are the wrong answer.

I believe a lot of top level teams will have great success this year using the 775Pros in their drivetrain. This year weight is probably not the huge driver that it is in many years so I don't suppose it will be as common as it would have been if teams were fighting for every gram.

Even so, I would not make blanket statements predicting failure when I don't think the data necessarily support this conclusion.

FWIW, you will have much less margin for error when it comes to overheating your drive motors but that does not mean that good teams with sound engineering can't find a way to make it work.

Dr. Joe J.

[waialua359]

Originally Posted by Joe Johnson

I am not so sure about the statement above that I have put in bold.

The facts you refenced are sound but it doesn't follow that 775Pros are the wrong answer.

I believe a lot of top level teams will have great success this year using the 775Pros in their drivetrain. This year weight is probably not the huge driver that it is in many years so I don't suppose it will be as common as it would have been if teams were fighting for every gram.

Even so, I would not make blanket statements predicting failure when I don't think the data necessarily support this conclusion.

FWIW, you will have much less margin for error when it comes to overheating your drive motors but that does not mean that good teams with sound engineering can't find a way to make it work.

Dr. Joe J.

Our team has used the 1 775 and 2 CIM setup per side for several years now, where recently we've swapped out the 775 for the Pro version.
We actually have an AM Supershifter setup where we modified one side of the transmission plates to add the 775pro.
In the past we've gotten away with the 1 AM Planetary 1 CIM setup and it was fine also, back when the no. of CIMS that could be used were much less and we needed them for other functions of our robot.
We have tried running 775-550 with Planetary combo before. That didnt turn out well. The drive sounded nice, but stalled out very quickly.

[remulasce]

Originally Posted by Joe Johnson

I believe a lot of top level teams will have great success this year using the 775Pros in their drivetrain.

Dr. Joe J.

Yes, and very few teams are top-level. Top level teams know how to handle the tradeoffs of the various motors. Mid-level teams can experiment in the offseason.

Most teams are lower-level and have plenty enough on their plate just to get a robot functional. For those teams, an all-CIM drivetrain is dead simple obvious, and is the correct solution for 99.5% of the time. It's appropriate to make blanket statements for the benefit of those teams, rather than to make every single team do a detailed analysis.

[efoote868]

Originally Posted by Joe Johnson

I am not so sure about the statement above that I have put in bold.

The facts you refenced are sound but it doesn't follow that 775Pros are the wrong answer.

I believe a lot of top level teams will have great success this year using the 775Pros in their drivetrain. This year weight is probably not the huge driver that it is in many years so I don't suppose it will be as common as it would have been if teams were fighting for every gram.

Even so, I would not make blanket statements predicting failure when I don't think the data necessarily support this conclusion.

FWIW, you will have much less margin for error when it comes to overheating your drive motors but that does not mean that good teams with sound engineering can't find a way to make it work.

Dr. Joe J.

The OP is from an inexperienced team asking if they could use 1 cim in their drivetrain for weight savings. Teams using 775Pros in their drivetrain should know enough that 1 cim isn't a good idea, and will likely be aware of all the 775pro dangers.

I suppose I could've included all those caveats, but the last thing I want is a young team smoking motors on the field.

[NoshBrooks]

Originally Posted by efoote868

In a drivetrain, a 775pro WILL overheat.
Stall them for more than 3 seconds, and they're no longer motors. Run them for more than 90 seconds at peak power, and they're no longer motors.

See actual test results here: http://motors.vex.com/775pro

I see you haven't seen Bomb Squad's 2016 drivetrain. If i recall correctly they ran dual 775 pros per wheel.

[efoote868]

Originally Posted by NoshBrooks

I see you haven't seen Bomb Squad's 2016 drivetrain. If i recall correctly they ran dual 775 pros per wheel.

Maybe someone from Bomb Squad would care to comment on their drive train from 2016. Did you run with all 775 pros, how many and did you burn any of them out?

But as far as drive trains go, Bomb Squad's are about 12 years experience more advanced than the majority of teams, and I'm consistently amazed at their level of performance on the field.


I'll modify my original statement:
Without CAREFUL consideration, using a 775pro in your drivetrain is VERY LIKELY to overheat and become a fancy paperweight. I STRONGLY urge you to stick with cims and mini cims.

[Jefferson]

We just had one per wheel. Committing 10 motors (4 drive, 4 steer, 2 tank) to the drive train is a lot to begin with. We would have been ALL drive train if we went for 2 775s per wheel.

We lost a few (<5 between practice and competition robots according to my memory). We theorize it had more to do with the impact from the defenses than stalling. The brush holders were breaking rather than melting/disintegrating. Just a theory, though.

And thanks for the kind words. We sure like our swerves here in Mountain Home.