CIM Drive Train motors

[merybar]

Has anybody ever compared 2 v 4 CIM moters for the drive train and how much power you lose?
Thanks
MAtt
894

[MrForbes]

You lose half of the power by having half as many motors.

[merybar]

What about speed?

[AndyB]

Speed will go up slightly, because you are decreasing the amount of speed lost due to friction. It will NOT double.

Torque will double though so if you want twice the speed, then gear it up more.

[MrForbes]

Maximum top speed you can get should be higher with two motors, since you have twice the power available, but teams usually set up the gearing to limit top speed. There are several reasons for this, including being able to control the robot, and having enough pushing power at low speeds (which you lose when you gear the robot to go faster). A good compromise might be to have a two speed transmission, so you can have good pushing power and still have the robot geared for a fast top speed.

Getting up to top speed will be faster (quicker acceleration) with 4 motors.

[kramarczyk]

JVN has an excel(lent) speed modeler in this white paper. http://www.chiefdelphi.com/media/papers/1676
With it you can change the motor inputs, gearing, weight, etc. and it will generate displacement, velocity, acceleration, and current plots.

He removed it from his recent update, so you'll have to go old school and get the old one.

Ken Patton has a similar spreadsheet, but I don't have a location to direct people to.

[merybar]

Ok thanks for the input. In previous years we are all about power and defense. This year we think its more about speed and the reason for not using 4 drive train CIM's is we think we are going to use one some where else.
Thanks for the help!

[Mike Hendricks]

Originally Posted by merybar

Ok thanks for the input. In previous years we are all about power and defense. This year we think its more about speed and the reason for not using 4 drive train CIM's is we think we are going to use one some where else.
Thanks for the help!

Also remember that if you have double (or triple) the motors on your drivetrain, you're going to drain your power much faster. If you get into a pushing match with a robot that has 2 or 3 motors on each side of its drivetrain and you're running single motors, then you MIGHT actually have the extra voltage in your battery to hold your own.

Food for thought.

[popo308]

Originally Posted by PhatMike

Also remember that if you have double (or triple) the motors on your drivetrain, you're going to drain your power much faster. If you get into a pushing match with a robot that has 2 or 3 motors on each side of its drivetrain and you're running single motors, then you MIGHT actually have the extra voltage in your battery to hold your own.

Food for thought.

not necessarily.... When thoose CIM motors stall they hog power.

our 2006 robot had 1 CIM on each side and they hauled all 120lbs around and after 2 minutes you could tell the battery was getting low.... plus with the other attachments on there the battery drained very fast.

[Mike Hendricks]

Originally Posted by popo308

not necessarily.... When thoose CIM motors stall they hog power.

our 2006 robot had 1 CIM on each side and they hauled all 120lbs around and after 2 minutes you could tell the battery was getting low.... plus with the other attachments on there the battery drained very fast.

Hence the "MIGHT". A number of factors go into how fast your battery drains, but the more motors you have running, the faster it'll drain. The compressor running all the time will kill you also.