Power Bumpers

[ubermeister]

Would it be legal to move the bumpers in and out on the robot to provide propulsion off walls and other robots? The robot would have to be built slightly smaller so that they do not extend outside the box, but as long as they are properly and securly supported they seem legal.

<R08>
P. BUMPERS must be mounted to the ROBOT within the BUMPER ZONE, and must remain there. The BUMPERS must not be articulated or designed to move outside of the BUMPER ZONE.

This clause of <R08> is vague, and I interpret it meaning that you can articulate your bumpers, so long as they remain inside the bumper zone. The bumper zone can be determined with the bumpers fully extended, and they can be retracted during competition.

This definitely needs to be clarified in Q&A, unless I am missing other rules or teams have asked this question in the past. Otherwise, it seems power bumpers (especially precharged pneumatics) would provide a good amount of force. Has anybody tried this or thought about it before?

[EricH]

Originally Posted by ubermeister

Would it be legal to move the bumpers in and out on the robot to provide propulsion off walls and other robots? The robot would have to be built slightly smaller so that they do not extend outside the box, but as long as they are properly and securly supported they seem legal.

<R08>
P. BUMPERS must be mounted to the ROBOT within the BUMPER ZONE, and must remain there. The BUMPERS must not be articulated or designed to move outside of the BUMPER ZONE.

This clause of <R08> is vague, and I interpret it meaning that you can articulate your bumpers, so long as they remain inside the bumper zone. The bumper zone can be determined with the bumpers fully extended, and they can be retracted during competition.

This definitely needs to be clarified in Q&A, unless I am missing other rules or teams have asked this question in the past. Otherwise, it seems power bumpers (especially precharged pneumatics) would provide a good amount of force. Has anybody tried this or thought about it before?

Try parts M and N of that rule, taken together or separately. (Part N limits the extension of the bumpers to very little room; Part M specifies that the robot frame must be supporting the bumper backing.)

Also see Part L and the parts governing attachment and weight.

[JesseK]

I don't have access to the '09 manual right now, but here's a thread from 2008 referring to your question:
http://forums.usfirst.org/showthread...ht=bumper+zone

If the game manual does not specifically define BUMPER ZONE, then I would suggest you pose the question on the official Q&A before you decide to really do this. In 2008, bumper articulation wasn't allowed due to that Q&A thread, and I'd imagine there will be something similar in 2009 (though you have to ask for it to be official). It's a gray area, and you'd rather ask ahead of time and be told 'no' rather than be told 'no' by the head ref at a competition.

[ubermeister]

Originally Posted by EricH

Try parts M and N of that rule, taken together or separately. (Part N limits the extension of the bumpers to very little room; Part M specifies that the robot frame must be supporting the bumper backing.)

Also see Part L and the parts governing attachment and weight.

To be legal as per N, you can start the bumpers extended and have that be the normal configuration and definition of the bumper zone. During the match you can retract them. And, the robot frame can support the bumpers. It's just the whole robot frame will be articulated. The bumpers will be attached to an articulating part of the robot frame.

As a side note, to get more normal force for friction, it is now advantageous to make your bumpers as heavy as possible.

[EricH]

Originally Posted by JesseK

If the game manual does not specifically define BUMPER ZONE, then I would suggest you pose the question on the official Q&A before you decide to really do this.

It's defined as the volume between two horizontal planes at 1 and 7 inches from the floor by Section 8.2.

[Mike Betts]

Originally Posted by ubermeister

To be legal as per N, you can start the bumpers extended and have that be the normal configuration and definition of the bumper zone. During the match you can retract them. And, the robot frame can support the bumpers. It's just the whole robot frame will be articulated. The bumpers will be attached to an articulating part of the robot frame.

I do not think that most robot inspectors would consider an articulating member part of the robot frame.

Originally Posted by ubermeister

As a side note, to get more normal force for friction, it is now advantageous to make your bumpers as heavy as possible.

<R08> E: BUMPERS (including any fasteners and/or structures that attach them to the ROBOT) must weigh no more than 18 pounds.

I would definitely get confirmation from the FIRST Q&A before designing this in...

[Mike Betts]

Originally Posted by ubermeister

...Otherwise, it seems power bumpers (especially precharged pneumatics) would provide a good amount of force...

Most robot inspectors will disallow a pneumatic system which does not have a relief valve (et cetera).

A "precharged" piston could increase it's pressure beyond the safe limit set by FIRST when the piston rod is hit.

[Mr. Freeman]

Originally Posted by Mike Betts

A "precharged" piston could increase it's pressure beyond the safe limit set by FIRST when the piston rod is hit.

I think all the regulators vent if the pressure in the downstream line increases above whatever they're set to. This should prevent the pressure in any pistons from increasing above the safe limit.

[Matt H.]

Originally Posted by Mr. Freeman

I think all the regulators vent if the pressure in the downstream line increases above whatever they're set to. This should prevent the pressure in any pistons from increasing above the safe limit.

This may be correct however pressure changes are not instantaneous. If a cylinder is impacted there will be a local increase in pressure within the cylinder meaning the cylinder will be exposed to high pressures before the regulator can vent the pressure.
Consider the traditional bike pump (which is just a cylinder). Even when pumping nothing (i.e. moving air around) a local pressure region developes inside the pump making pumping more difficult--If you were to hit the handle with a hammer a very high pressure region would develope before it could be vented by the nozzle.

[Al Skierkiewicz]

Taggin along on Mike's post, ask the Q&A as their answer is the only official one. However, bumpers mounted on parts of the robot that move must still be within the size limits at it's maximum size. If the robot is less that 28x38x60 and the bumper is firmly attached to a robot that grows in size but does not exceed the stated dimensions, it is possible that such a robot might be legal. Of course everything is subject to the inspection process as pointed out. Of particular note, is that any contact with the bumpers must occur in the bumper zone and
<R06>
ROBOTs must use ROVER WHEELS (as supplied in the 2009 Kit Of Parts and/or their equivalent as provided by the supplying vendor) to provide traction between the ROBOT and the ARENA.
(emphasis is mine)

[Nate Laverdure]

Originally Posted by Mike Betts

Most robot inspectors will disallow a pneumatic system which does not have a relief valve (et cetera).

Not true in all cases-- closed-loop pneumatic shocks are expressly allowed. See <R71> part I:

<R71>
In addition to the items included in the Kit Of Parts, pneumatic system items specifically permitted on 2009 FRC ROBOTS include the following items. All included items must be “off the shelf” pneumatic devices rated by their manufacturers for pressure of at least 125psi, and used in their original, unaltered condition (except as required for assembly with other components).
...
I. For the purposes of the FIRST competition, closed-loop pneumatic (gas) shocks are not considered pneumatic devices, and are permitted additions to the ROBOT.

[Mike Betts]

Originally Posted by Nate Laverdure

Not true in all cases-- closed-loop pneumatic shocks are expressly allowed. See <R71> part I:

Nate,

Yes they are and they are designed for that purpose. However, I have seen teams show up with charged, dead-ended Bimba Cylinders and try to argue that they are not part of the pneumatic system.

Regards,

Mike

[Tottanka]

i got an answer from GDC about that, and it seems OK as long as you are moving the bumper along with it's chassis part, and are in the dimensions and safety rules.