[DFTF] Motors... ...Drive Motors...

[Joe Johnson]

This is part of a series of posts called Drinking From The Firehose on getting Dr Joe back up to speed on All Things FIRST.

Today's topic:
Motors... ...Drive Motors...

Okay, so I am reading the rules minding my own business and BAM! I am hit with more Watts that any robot chassis has a right to expect.

In my day, there were two drills in the kit with about 200W of peak power apiece. After that, the motor power fell like a rock to the sub 30W range (window and seat adjusters motors mostly the Globes would come later...).

There was literally no reasonable option but to drive with the drill motors.

Fast forward to last year.

• 4 "Coke Cans" from CIM @ 340W each
• 2 550's from FP @ 290W each
• 4 775's from BB @ 270W each (the 18V version scaled to 12V)

That's a lot of Watts.


Sooo... ...I suppose that the most common drive system is still 2 CIM's per side (4 CIM total). Because they are awesome motors in so many ways, not the least of which is that their size allows them to get rid of a lot of heat fast (and we all know that we pour a lot of heat into them -- FYI a curling iron is typically about 20W!)


But it seems that there are enough high power motors in the kit that other options may make sense as well.


Are there folks that used the FP's for driving (either as a 3rd motor per side or to use a CIM somewhere else or to save weight or because your team just felt like it)? How'd that work out?



On thing that worries me about the FP is that they have a circuit breakers in them now a days (at least they did 2 years ago when I was helping a team in MD. That fuse caused my winch to wig out -- not a happy event when you are trying to hang). Did people who drove with the FP's have breakers trip (not the Power Distribution Breaker but the one in the motor itself).



Same questions about the 18V 775's from BB.

One thing I always say is if you don't move, you don't play after lunch on Saturday. To that end, I am very cautious about drive train failures. So... if the FP and BB motors are not up to the task, I want to know about it before we design our robot drive train around them.



Tell me what traps to avoid.


On a closely related topic, let me know if the CIMple Box trannies from AndyMark are as awesome as they look on paper (I love the name, I love the compactness, I love that they do exactly what they need to and no more -- looks pretty sweet to me... ...but if it turned out to be a trap it won't be the first time FIRST has shipped a rookie killer in every kit ;-)


The only thing that I get a little worried about is that output shaft and how it's supported. Can it really stand up to a 2 CIM motor stall with a #35 12T sprocket hanging out their on the end of the shaft? Andy and Mark are clever guys so I suppose it can, but I would like some testimonials if you have "FIRST hand" experience.



Before I go, I want to caution folks to be nice. Drive systems are a touchy subject. Let's not start unnecessary battles (for example the shifters vs non shifters - we can discuss it yes, but let's just agree that we are never going to reach total agreement. In any case, let's keep the flame wars to a minimum).


Joe J.