Clutch system

[gyaniv]

Does anyone know if a 12v clutch is allowed on the robot?
or even 5-6v if the is one that exist.

[Mark McLeod]

No other electrically operated motor or actuator, than what's called out explictly by the rules, is allowed.

So, no.

[MrForbes]

I expect he is asking about an electromagnetic clutch? of the type used on air conditioning compressors in cars. If so it would likely fall into the "electromechanical actuator" category and be illegal. Or not....

[Vikesrock]

Here is the appropriate Q&A:
http://forums.usfirst.org/showthread.php?t=13981

[Tanner]

Originally Posted by Vikesrock

Here is the appropriate Q&A:
http://forums.usfirst.org/showthread.php?t=13981

I don't really think that this answers all the questions. Why? Cause my team is trying to figure out if we can use a clutch that we used in 2008 for our catapault and we're not getting any specific answers yet.

http://forums.usfirst.org/showthread.php?t=13980

I'm not psychic GDC, just give me a straight answer. I can't determine if x part is legal if I don't know what the official definition of this is.

-Tanner *confused*

[Alan Anderson]

Originally Posted by Tanner

http://forums.usfirst.org/showthread.php?t=13980

I'm not psychic GDC, just give me a straight answer. I can't determine if x part is legal if I don't know what the official definition of this is.

The web page pointed to in that Q&A specifically describes an electric solenoid valve actuator. It has components that aren't part of a generic solenoid.

The "official definition" of an electric solenoid actuator is pretty simple and reasonably obvious. A solenoid consists of an electromagnet and an armature that moves to provide a mechanical output when the electromagnet is energized.

If you tell us what "x" is, many of us will be able to tell you why it is or is not legal according to the robot rules.

[Al Skierkiewicz]

Tanner,
This is the section that applies to your answer...
<R53> Items specifically PROHIBITED from use on the ROBOT include:
A. Electric motors and/or servos different from, or in addition to, those in the KOP, with the exception of those specifically permitted by Rule <R52>.
B. Electric solenoid actuators (note: electric solenoid actuators are NOT the same as pneumatic solenoid valves – the latter are permitted, the former are not).

If you had an electric clutch that used a moving part that was attracted by a magnetic field, then this rule would have applied in 2008 and would (should) have been deemed illegal as it is in 2010. The same language existed in the rules then as now. If you would like to PM me with the part you are considering I can give you an opinion from an inspector point of view. The definitive answer still comes from the GDC via the Q&A and has been answered.

[Tristan Lall]

Originally Posted by Alan Anderson

The "official definition" of an electric solenoid actuator is pretty simple and reasonably obvious. A solenoid consists of an electromagnet and an armature that moves to provide a mechanical output when the electromagnet is energized.

Doesn't the definition of "solenoid" also necessarily specify that the electromagnetic coil produces a reasonably uniform magnetic field in the centre of the coil, and that the armature is located there? (Otherwise, there would be no distinction between a run-of-the-mill electromagnet, and a solenoid.)

Considering that distinction, I'm not convinced that an electromagnetic clutch is always illegal—it would depend on what's inside. Given this question and its response, I think the GDC is agreeing in general terms with that proposition.

[MrForbes]

If there is an armature that moves in response to the electromagnet being energized, it's probably a solenoid and illegal. If nothing moves as a result of the electromagnet being energized, it's probably just an electromagnet and legal.

We still haven't seen pictures of the device in question, so it's pretty hard to say.

An electromagnetic clutch used in an automotive air conditioning compressor has a part that moves as a result of energizing the electromagnet, so it's probably a solenoid.

If there is some other type of electromagnetic clutch, I'd like to see it.

[Tristan Lall]

Originally Posted by squirrel

If there is an armature that moves in response to the electromagnet being energized, it's probably a solenoid and illegal. If nothing moves as a result of the electromagnet being energized, it's probably just an electromagnet and legal.

Just for the sake of discussion, is this electromagnetic bell a prohibited solenoid actuator? (I would say no, because its geometry is inconsistent with a solenoid.)


From Wikimedia Commons

[Alan Anderson]

Originally Posted by squirrel

If there is some other type of electromagnetic clutch, I'd like to see it.

There are clutches that use a magnetorheological fluid which changes its viscosity based on an applied magnetic field.

[Alan Anderson]

Originally Posted by Tristan Lall

Just for the sake of discussion, is this electromagnetic bell a prohibited solenoid actuator? (I would say no, because its geometry is inconsistent with a solenoid.)

I would expect the GDC to rule it illegal. The geometry might be inconsistent with the typical electric solenoid actuator, but the action is close enough that I think it meets the intent of the prohibition.

[Daniel_LaFleur]

Originally Posted by Alan Anderson

There are clutches that use a magnetorheological fluid which changes its viscosity based on an applied magnetic field.

There are clutches that work off of magneto-strictive (sp?) materials like Terfenol-D

[martin417]

Originally Posted by Tanner

I don't really think that this answers all the questions. Why? Cause my team is trying to figure out if we can use a clutch that we used in 2008 for our catapault and we're not getting any specific answers yet.

http://forums.usfirst.org/showthread.php?t=13980

I'm not psychic GDC, just give me a straight answer. I can't determine if x part is legal if I don't know what the official definition of this is.

-Tanner *confused*

Tanner,

After examining your 2008 bot at GA Tech at the control system demo last year, several of us spent much discussion on your clutch, and the legality thereof. We came to the conclusion that the inspectors overlooked an apparent violation. This was just our opinion, we have no line into the mysterious hive mind of the GDC.

I agree that the Q&A answers have been vague, but it looks to me like they are saying that if something moves by electromagnetism, and it's not part of a solenoid valve, or a motor provided in the kit, then it is illegal. I realize that the movement in the clutch is very small, but if they intended to allow some movement, they would have specified a maximum. By not doing so, they specified a maximum of zero inches.

All of the above is my opinion, and has no real meaning in the greater scheme of FIRST.

[MrForbes]

Originally Posted by Alan Anderson

There are clutches that use a magnetorheological fluid which changes its viscosity based on an applied magnetic field.

This type of clutch would probably be prohibited too, as it contains a liquid.