General Motor Rules

[jman4747]

So I've been in the stepper thread and it brought back a sentiment that MAYBE we could open up the general motor rules such that you can use any 12V motor you can find so long as it satisfies a wattage limit (and a few other rules).

For example:

#1 No more than:
4x 340W-300W (CIM's)

6x <300W-200W (rs-775-18's & Mini CIM's)

4x <200W-50W (AM 9015's, RS-775-12, & BAG's)

4x <50W (AM PG motor & window motors)

#2 Stall current max: 140 amps.

#3 Must be COTS

#4 Must provide a data sheet (to prove the above)

#5 Must have P/N visible (to prove that #4 is not fake if necessary)

#6 Must be < $400 (2015 single part allowance)

#7 If it's on the allowed list (anything allowed in the 2012-2015 rules?) you can just use it.

Anything I missed?

Obviously inspection can take longer for any team using a lot of different motors but you could subvert this by placing an absolute maximum on non-standard motors. There is also the possibility that someone just fabricates a datasheet but at the end of the day we do trust everyone to bag and tag on their own.

Also please don't assume that the above rules are what I think will absolutely work, it is just an example.

[AdamHeard]

It'd be simpler to limit motors by form factor, with the two obvious choices to expand being the 500 and 700 sized motors. As in, any 500 or 700 sized brushed motor you can obtain as a COTS item is legal.

Both of which are inherently power limited by their size, and provide a wide range of existing COTS products to interface with.

[Michael Hill]

Originally Posted by AdamHeard

It'd be simpler to limit motors by form factor, with the two obvious choices to expand being the 500 and 700 sized motors. As in, any 500 or 700 sized brushed motor you can obtain as a COTS item is legal.

Both of which are inherently power limited by their size, and provide a wide range of existing COTS products to interface with.

I'm curious, is there some written standard for 500/700 series motors? All I've found are actual Mabuchi part numbers as well as other motors claiming to be 500/700 series motors for RC toys. (Or did Mabuchi just set the standard?)

[Chris is me]

Is 6 cims, unlimited quantities of half a dozen other motors really not enough variety? We have cheap motors, durable motors, equivalent motors from multiple suppliers, and different size / power motors available; plenty of options. I really think at this point opening up the motor rules further is solving a problem that doesn't exist.

If they are opened up, being able to choose any 500 / 700 series motor seems like the logical next step, but other than that, I'd rather not have teams get competitive advantages from being able to source some super obscure motor that no one else has in stock / knows about.

[EricH]

Originally Posted by Chris is me

Is 6 cims, unlimited quantities of half a dozen other motors really not enough variety? We have cheap motors, durable motors, equivalent motors from multiple suppliers, and different size / power motors available; plenty of options. I really think at this point opening up the motor rules further is solving a problem that doesn't exist.

DITTO.

[geezer]You young whippersnappers don't know how good y'all have itI Back in my day, we only got 2 drill motors (there's the drivetrain!), a couple o' window motors, a van door motor, pair of Fischer-Price motors (something like a 700-series motor would be about right powerwise), maybe a CIM or two, and who knows you might get a seat motor or two if you was lucky. We only had them motors to power the whole robot! And we liked it--them being delivered in the kit saved us from walking uphill in the snow both ways to get 'em from the post office! Then some wiseacre dropped the drill motors for two more CIMS, canyoubelieveit. And we liked it more! And you're complaining that 6 CIMS and all these other really really nice motors ain't enough???? Why I oughtta get out o' this here rocker and come show you how it's done! Open up the motor rules? They already been opened up![/geezer]

Seriously, folks. If the motor selection currently available doesn't fit your needs, you may want to reconsider how you're doing things. Try pneumatics.


Now, speaking as an inspector: If teams can't even get the numbers right (you'd think that black with a white background, with a given size, spelled out quite clearly in the manual, would be really easy to do), and a missing BOM is a common reason for not being able to pass on the first day of inspection, do you really think they'll remember to bring their datasheets? (For that matter, it seems like every year somebody pulls out a Globe motor, asking what it is--and has to be told it's illegal. At least a lot of them do it on CD before bag day so it can be swapped out.) I really can't say that this is a great idea...


I think someone is missing part of the point of the motor rules. The point of the motor rules is to give every robot the same available maximum power (well... OK, it used to be, until certain motors were classed as unlimited). It also ensures that everybody is using the same motor types--sure makes troubleshooting and spares a lot easier when you can ask a neighboring team and get a motor/help, rather than having to phone the home shop for your spare motors that you forgot.


Rather than loosening the motor rules...

I might suggest limiting the motors to 4 CIMs, 2 Mini-CIMs, 6 775s, 550s, and/or BAG motors (any combination), 3 PG-71s, and unlimited "automotive" motors (window, seat, door). Servos and electric solenoid actuators remain unlimited. Plenty of power in that batch...

[jman4747]

Originally Posted by EricH

DITTO.

[geezer]You young whippersnappers don't know how good y'all have itI Back in my day, we only got 2 drill motors (there's the drivetrain!), a couple o' window motors, a van door motor, pair of Fischer-Price motors (something like a 700-series motor would be about right powerwise), maybe a CIM or two, and who knows you might get a seat motor or two if you was lucky. We only had them motors to power the whole robot! And we liked it--them being delivered in the kit saved us from walking uphill in the snow both ways to get 'em from the post office! Then some wiseacre dropped the drill motors for two more CIMS, canyoubelieveit. And we liked it more! And you're complaining that 6 CIMS and all these other really really nice motors ain't enough???? Why I oughtta get out o' this here rocker and come show you how it's done! Open up the motor rules? They already been opened up![/geezer]

Seriously, folks. If the motor selection currently available doesn't fit your needs, you may want to reconsider how you're doing things. Try pneumatics.


Now, speaking as an inspector: If teams can't even get the numbers right (you'd think that black with a white background, with a given size, spelled out quite clearly in the manual, would be really easy to do), and a missing BOM is a common reason for not being able to pass on the first day of inspection, do you really think they'll remember to bring their datasheets? (For that matter, it seems like every year somebody pulls out a Globe motor, asking what it is--and has to be told it's illegal. At least a lot of them do it on CD before bag day so it can be swapped out.) I really can't say that this is a great idea...


I think someone is missing part of the point of the motor rules. The point of the motor rules is to give every robot the same available maximum power (well... OK, it used to be, until certain motors were classed as unlimited). It also ensures that everybody is using the same motor types--sure makes troubleshooting and spares a lot easier when you can ask a neighboring team and get a motor/help, rather than having to phone the home shop for your spare motors that you forgot.


Rather than loosening the motor rules...

I might suggest limiting the motors to 4 CIMs, 2 Mini-CIMs, 6 775s, 550s, and/or BAG motors (any combination), 3 PG-71s, and unlimited "automotive" motors (window, seat, door). Servos and electric solenoid actuators remain unlimited. Plenty of power in that batch...

The problem isn't lack of options or power it's that the rule is based on P/N not power limitations. I wish I could use dill motors or FP's or any of the 500 & 700 series motors I could find but I can't because they aren't a specified part number.

As others hint the actual limiting factors include the PDP ports, snap action breakers, main breaker, battery, robot weight, motor controller specs, the fact that it must be a brushed DC permanent magnet motor, and physical size of the motor. The amount of power available is already limited. I found an old drill with an "FRS-550" in it and even found a data sheet to prove its similarity to the BB RS-550 but I still couldn't use it. Why? Because it's not that one part number. It doesn't really make sense.

The point is to limit DC brushed motors by voltage, power, and or current not P/N. Just look at how the CIM has to have 9 different P/N's in the 2015 rule book.

[IndySam]

Originally Posted by EricH

I might suggest limiting the motors to 4 CIMs, 2 Mini-CIMs, 6 775s, 550s, and/or BAG motors (any combination), 3 PG-71s, and unlimited "automotive" motors (window, seat, door). Servos and electric solenoid actuators remain unlimited. Plenty of power in that batch...

Amen, teams have way to many powerful motors now. We need to get back to the days of having to make decisions about where to use the most powerful motors. I miss this design challenge.

[Gregor]

I don't mind the 2015 motor rules, but I would like to see some sort of limit in drive motors in contact games, as the drivetrain arms race is not fun.

[Kevin Leonard]

Originally Posted by Gregor

I don't mind the 2015 motor rules, but I would like to see some sort of limit in drive motors in contact games, as the drivetrain arms race is not fun.

+1
All that a drive motor arms race does is reward teams with more resources. Increased motors can be helpful for doing things like climbing the pyramid in 2013 in a reasonable amount of time, but in 2015 we had to make a total of zero trade-offs when it came to alotting motors. 20's elevator had 4 motors on it, for example.

[Knufire]

Originally Posted by Kevin Leonard

...but in 2015 we had to make a total of zero trade-offs when it came to alotting motors. 20's elevator had 4 motors on it, for example.

Exactly why I agree with EricH about having stricter motor limits. Having to make significant tradeoffs in how much power to allocate to what mechanism is a fun part of design and encourages creative solutions vs. lets just throw more motors on it until it does what we want.

[Thad House]

I think requiring 12V motors isn't a good idea. The RS-775 everyone uses is an 18V motor, and it runs great, partially because its never running more then 66% of what its rated for. I think the watt and amp limits need to be counted at 12V, but if you want to use a motor rated for higher voltage you should be able to do so. The battery already limits to 12V.

[Scott Kozutsky]

Originally Posted by EricH

Seriously, folks. If the motor selection currently available doesn't fit your needs, you may want to reconsider how you're doing things. Try pneumatics.

Originally Posted by IndySam

Amen, teams have way to many powerful motors now. We need to get back to the days of having to make decisions about where to use the most powerful motors. I miss this design challenge.

I couldn't agree more. My personal preference would be 5 CIM motors (can be freely downgraded to minis), 3 minis (plus downgraded full ones), 5 combined RS/bag/PG motors and unlimited auto motors.

It would also be interesting to see a year with a very strict motor allowance. 3 cims, 4 minis, 4 combined RS/bag/PG motors and unlimited auto motors for example.

What I really think we need is a CHEAP motor controller for the smaller motors. You don't need to withstand 100+ amps of surge current for a window motor. It would also give some much needed utility to these motors.

I inspected a team which used 1 speed controller for 2 cims. It was a bad mistake but it just goes to show that we don't need more complex rules. On that note: open up the servo restrictions.

[EricH]

Originally Posted by Scott Kozutsky

On that note: open up the servo restrictions.

THAT one, I'll go for. 4W is pretty weak.

I'd say to allow all micro-servos, and any hobby servos up to some reasonable wattage (10W, maybe? 20? Just throwing some numbers out here...), but nothing that isn't a hobby servo (AKA, nothing industrial).

[jman4747]

Originally Posted by Scott Kozutsky

I couldn't agree more. My personal preference would be 5 CIM motors (can be freely downgraded to minis), 3 minis (plus downgraded full ones), 5 combined RS/bag/PG motors and unlimited auto motors.

It would also be interesting to see a year with a very strict motor allowance. 3 cims, 4 minis, 4 combined RS/bag/PG motors and unlimited auto motors for example.

What I really think we need is a CHEAP motor controller for the smaller motors. You don't need to withstand 100+ amps of surge current for a window motor. It would also give some much needed utility to these motors.

I inspected a team which used 1 speed controller for 2 cims. It was a bad mistake but it just goes to show that we don't need more complex rules. On that note: open up the servo restrictions.

The point was not to increase the arbitrary power limit but to limit the power by setting a direct limit on power. Right now the limit is indirectly set by specifying how many of each specific motor a robot can have. I am proposing that either it be set by a total watt limit, a categorical watt limit (see op), or similar method. The limits in the first post can simply be reduced to satisfy a reduced power allowance.

In short the point was to increase the number of different motors we could use not the total wattage of what can legally be attached to the robot.

Edit: I too would like to see an increase in both the servo and solenoid wattage limits.

[EricH]

Originally Posted by jman4747

The point was not to increase the arbitrary power limit but to limit the power by setting a direct limit on power. Right now the limit is indirectly set by specifying how many of each specific motor a robot can have. I am proposing that either it be set by a total watt limit, a categorical watt limit (see op), or similar method. The limits in the first post can simply be reduced to satisfy a reduced power allowance.

Why? Really simply, why? What exactly is the current motor restriction not allowing you to do that you need to do?


Is it just that you want to use a different motor? OK, submit the idea to FIRST to see if they can get the company interested in supplying 3K motor "sets" (a set being anywhere from 1 to infinity motors). A different type of motor altogether? In that case, I ask why you really need that functionality, and look for workarounds. Or is there something I'm not seeing? (I honestly don't see any application for stepper or brushless motors that can't be handled with an additional sensor on the robot and careful motor selection.)


In the real world, the customer doesn't relax requirements just because "it should be this way". The customer only relaxes the requirements if it can be conclusively shown to their satisfaction that the requirements must be relaxed in order to meet other requirements--and usually, that can't be shown! Again, FIRST imitates life...



Now, I bet someone is going to come back with "well why do you favor the servo limits increasing?" And my answer is that it is nearly impossible for teams that don't want to use pneumatics to have multiple speed drivetrains with the servos we have. I've seen teams gang servos to get the required power for some relatively minor jobs. I've very, very rarely seen a servo used on a robot--a "gate latch" a few years ago being one of the cases. Plain and simple, there just isn't enough power available in that group.