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-   -   Limiting Drivetrain Motors (http://www.chiefdelphi.com/forums/showthread.php?t=129864)

Billfred 23-06-2014 21:44
Re: Limiting Drivetrain Motors
 
I don't think the kitbot is obsolete by the available power, but it does require a little work to tap the power. We did switch in the AndyMark 3CIM4U gearboxes ($150 for the pair, if I recall) and ran our underweight robot just fine all season. Total BOM on the change would probably be around $260 with the two extra CIMs and a pair of speed controllers (which IFI has a PDV for if you want to split hairs). If a sub-$300 parts order is causing major insomnia, I'd question whether the team was really prepared to compete in FRC.

The other notion: 6-CIM setups have fewer parts (and fewer small moving parts) compared to a shifting design. Could this be FIRST's subtle helping hand to ensure drivetrains stay mobile?

That said, if FIRST was worried about it I say limit teams to five CIMs. Teams will either do without, shift gears, or learn a thing or two about matching motors to party like it's 2004.

AllenGregoryIV 23-06-2014 22:30
Re: Limiting Drivetrain Motors
 
Quote:
Originally Posted by Billfred (Post 1390879)

The other notion: 6-CIM setups have fewer parts (and fewer small moving parts) compared to a shifting design. Could this be FIRST's subtle helping hand to ensure drivetrains stay mobile?
I don't think this is FIRST's plan but I do think it is an advantage. I've never been on a team that has used shifting gearboxes in competition. Our setup this year shifted the wheels to get speed reductions but we haven't used something that can fail in the same way as your standard two speed gearbox.

colin340 24-06-2014 09:49
Re: Limiting Drivetrain Motors
 
I would hate to see the arms race end, fast robots and harder hit are way more fun for all parties, other then rookies.

Andrew Schreiber 24-06-2014 10:02
Re: Limiting Drivetrain Motors
 
Quote:
Originally Posted by colin340 (Post 1390929)
I would hate to see the arms race end, fast robots and harder hit are way more fun for all parties, other then rookies.
And anyone trying to actually play the game. It gets old going out and spending most of the match being smashed into by teams that are incapable of playing the game.

colin340 24-06-2014 10:27
Re: Limiting Drivetrain Motors
 
Quote:
Originally Posted by Andrew Schreiber (Post 1390931)
And anyone trying to actually play the game. It gets old going out and spending most of the match being smashed into by teams that are incapable of playing the game.
Fair point, but this year we got called for hitting the defense bots back too hard. Teams that are blockading / pinning a partner should design for 13 fps hits or get out the way.

i'm sick of playing tea party games / soccer.

BBray_T1296 24-06-2014 11:05
Re: Limiting Drivetrain Motors
 
IMHO, it was very obvious day one that high speed defense would be prevalent.

adciv 24-06-2014 11:17
Re: Limiting Drivetrain Motors
 
I see more than 4 cims being necessary as it limited the arm/endeffector designs. If there needs to be a limit on the drive systems, this could be accomplished by limiting the drive system to four CIMs.

That said, our main issue this year was teams entering our frame perimiter. We have some gashes (1ft above the bumpers) in our 1/8th(?) aluminum from other robots.

Orion.DeYoe 24-06-2014 12:08
Re: Limiting Drivetrain Motors
 
Quote:
Originally Posted by Tom Line (Post 1390832)
I don't think that anyone can deny that FRC in general is in a bit of drive train war right now. The latitude we've been given in the last few years in motor choice and availability have made 6 cim drive trains increasingly common, with some few teams even moving to an 8 motor drive train.

That isn't a bad thing from an engineering standpoint.

Drive trains area already limited by the 120 amp breaker. Assuming the new CrossTheRoad PDB and current monitoring does what we hope it will, teams should be able to ride 'upper limit' of power while not popping their breaker.

I have to wonder, though, if we would be better served in FRC by limiting the total power output of the drivetrain. There is an argument to be made about the increasing price of multi-cim multi-speed gearboxes. A reasonable argument can also be made that the kitbot drive train has been rendered obsolete. This year, we saw an extremely brutal game. This made partially possible by the wide open field, but the high acceleration and high top-end speed that our drivetrains delivered were also responsible. A lot of robots left the field in pieces: even those of multiple-time world champions.

I think we've reached the point where it's time for FRC to consider reigning in the drive train power. I wouldn't be adverse to a max 6 cim, or even 4 cim and 2 mini-cim 'power' limit. I don't have my motor sheet in front of me to lay down the power numbers of those motors right now. What do other folks think?
Absolutely not.
This is an engineering competition. Teams try to find mechanism configurations that give them a competitive edge. If 6-CIMs are "breaking the game" then it's because too many teams are holding to the old 4-CIM way. Stronger drivetrains encourage more robust designs which teaches better engineering practices.
That being said, for the past two years we stuck with 4 CIMs on our drivetrain and never had a problem with being pushed around by stronger drivetrains.

FrankJ 24-06-2014 12:30
Re: Limiting Drivetrain Motors
 
Realize it an engineering design competition with limits. You don't get to choose your battery. You have a weight limit. Limiting drive motors would just be another limit. I am sort of for it. Or maybe we could go back to regolith? Traction limited drive systems: Oh yeah.

adciv 24-06-2014 12:35
Re: Limiting Drivetrain Motors
 
Quote:
Originally Posted by Orion.DeYoe (Post 1390971)
If 6-CIMs are "breaking the game" then it's because too many teams are holding to the old 4-CIM way. Stronger drivetrains encourage more robust designs which teaches better engineering practices.
Other possibility: The game becomes about who has the strongest drivetrain to the exclusion of all else.

To use the 2011-2012 FTC game Bowled Over for similarity, the game became all about one aspect: Putting one ball in a crate and lifting it as high as possible. This was not the intent of the game. The GDC did not realize FTC robots would be able to go over seven feet high, much less seventeen feet.

It is possible for changes in the rules to "break the game" by making it all about one aspect. You can't teach better engineering practices by removing the tradeoffs that come with balance. And "robust designs" is a different issue entirely. Robots getting damaged/destroyed is not the intent. FIRST is not supposed to be Battle Bots.

magnets 24-06-2014 13:04
Re: Limiting Drivetrain Motors
 
Quote:
Originally Posted by adciv (Post 1390983)
To use the 2011-2012 FTC game Bowled Over for similarity, the game became all about one aspect: Putting one ball in a crate and lifting it as high as possible. This was not the intent of the game. The GDC did not realize FTC robots would be able to go over seven feet high, much less seventeen feet.
Do you have a video of a high lifter? I can't find many FTC videos on the internet

pntbll1313 24-06-2014 13:30
Re: Limiting Drivetrain Motors
 
Quote:
Originally Posted by magnets (Post 1390990)
Do you have a video of a high lifter? I can't find many FTC videos on the internet
Here's a pretty cool match with high lifters:
http://www.youtube.com/watch?v=imuLGW4Wf9s

adciv 24-06-2014 13:42
Re: Limiting Drivetrain Motors
 
Here's a picture of the two robots that started the Arms Race. The taller of the two (on the left) was merely 9ft tall. The US was sold out of 1" square tubing before the end of that qualifier.

RyanShoff 24-06-2014 15:24
Re: Limiting Drivetrain Motors
 
A modern swerve drive takes 8 motors just for the drivetrain. I would be extremely disappointed if rule changes killed a whole class of drivetrain.

Last year we had 13 motors and a compressor. More motors are more inspirational.

Lil' Lavery 24-06-2014 15:49
Re: Limiting Drivetrain Motors
 
Quote:
Originally Posted by Max Boord (Post 1390862)
I see this as limiting innovation. I can guarentee teams are working hard right now to create 6 cim swerve and tex-coast drives wich would likley never be created if there was a rule created banning 6 cim drives.
Do you not think innovation can be accomplished with fewer motors, as well? Are the only innovations left in FRC drivetrains more powerful or refined versions of what has come before?

Quote:
Originally Posted by RyanShoff (Post 1391013)
A modern swerve drive takes 8 motors just for the drivetrain. I would be extremely disappointed if rule changes killed a whole class of drivetrain.
I doubt there would be any limitations on motors used to steer, or that otherwise don't actually provide any power to the wheels. Also, there have been plenty of swerve variants that have used fewer than 8 motors.

Quote:
Originally Posted by RyanShoff (Post 1391013)
Last year we had 13 motors and a compressor. More motors are more inspirational.
Why are more motors more inspirational? Isn't finding a way to accomplish a task despite limitations also an inspirational activity?


Note: I don't necessarily want a restriction on drive power, I just find some of the arguments being used against it to be rather peculiar.


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