[FTC]: FTC vexmetal

[paragon571]

See in the rules about vex motors. Double checking can we use the metal and wheels from the old vex kits also this year. Especially since they said something about predrilled metal

[DavisDad]

Originally Posted by paragon571

See in the rules about vex motors. Double checking can we use the metal and wheels from the old vex kits also this year. Especially since they said something about predrilled metal

There are no limits to what wheels we can use, except that the wheels and robot must fit into 18" cube, and must not damage the floor tiles. See Link to Robot Inspection and Build Rules - Mechanical - Answer Thread

[paragon571]

we were wondering if we could use the actual metal not just the wheels.

[DavisDad]

Originally Posted by paragon571

we were wondering if we could use the actual metal not just the wheels.

My understanding is that all materials, even "post processed" are OK, as long as available to all teams. They do limit assemblies to "one degree of freedom". They want teams to build their own devices and not buy them.

[pilum40]

Am I correct then when I read your answer above that we can use Vex chassis parts, motors, gears and wheels in lieu of Tetrix? If so, that will allow us to build an affordable competition robot using the FTC control system/phon es, electricals versus a purchase of over $1000. total for control system andTetrix kit(s). We've got a large amount of Vex parts and metal for our classroom robotics STEM program. Being able to use this makes gives me less heartburn as I jockey very limited funds for both FTC and FRC this year. I just can't see not using what we have on hand before expending a lot of money on duplicate (style) parts.
Your thoughts please?

Thanks!

Steve Miller
Coach FIRST Robotics Challenge Team 3355
Coach FIRST Tech Challenge (multidigit number waiting on team confirmation)

[JimInNJ]

Yep, all COTS parts, both raw and post processed, are legal this year, as long as they have only one degree of freedom (Game Manual I, Section 5.3.2).

Good Luck!

[pilum40]

Sorry to be stupid but how do I determine degrees of freedom? I'm a history teacher by trade and coach robotics because I really love the technologies involved. I've never had any exposure to engineering principles. How should I convey this concept to my team (freshmen and sophomores)?

Again, sorry to be ignorant...My flame suit is on. Y'all can have a big laugh at my expense. LOL

[pilum40]

so, a Vex motor cannot be used since it can go foward and reverse (two degrees of freedom?), a linear slide cannot be used since it goes up and down, or an arm built with Vex parts because it can extend and retract? Am I on the right track? Again....I'm not an engineer....just have to explain this to young people.

[DavisDad]

Originally Posted by pilum40

so, a Vex motor cannot be used since it can go foward and reverse (two degrees of freedom?), a linear slide cannot be used since it goes up and down, or an arm built with Vex parts because it can extend and retract? Am I on the right track? Again....I'm not an engineer....just have to explain this to young people.

FTC has always listed legal motors. This year the "VEX EDR 393 DC Motor (with a single VEX Motor Controller 29 per 393 motor)" is legal. See here for listing of legal motors (p 32): Game Manual Part I

The single degree of freedom applies to "consumer off the shelf" (COTS) components not explicitly listed, or exempted (like gears), in the Game Manual.

[M. Mellott]

Steve,

Per Wikipedia...Six degrees of freedom (6DoF) refers to the freedom of movement of a rigid body in three-dimensional space. Specifically, the body is free to change position as forward/backward, up/down, left/right translation in three perpendicular axes [X, Y, and Z], combined with changes in orientation through rotation about those same three perpendicular axes, often termed pitch, yaw, and roll.

Using your examples...a motor has one degree of freedom (rotation about the output axle), so it would be legal--going forwards or backwards is still rotation about one axis, i.e. positive/negative direction. However, as mentioned above, there is a specific list of motors that are legal to use. With your linear slide...a linear slide goes back and forth along a straight line (it doesn't go side-to-side, or rotate), so it too is legal to purchase.

Now, here's that key: if you purchased that linear slide with a gripper already attached to the slide, or if the linear slide was on rollers (wheels turning about their axles move the slide back-and-forth)...those are more than one degree of freedom, so they would be illegal to purchase. BUT, if you buy a simple linear slide, you buy a legal motor and rollers, and then build your own motorized slide--now that is legal.

As mentioned above, they want you to build your devices, not buy a pre-engineered kit or pre-assembled unit that you just wire up to your robot and go without any effort.

[JohnMMcD]

Another take on this is that a single-degree-of-freedom mechanism can have its movement described by one number. That number might refer to translation or rotation, and the number could be positive or negative, but it must be a single number. The mechanism can consist of more than one moving part. See the picture of the four bar linkage at http://www.learnengineering.org/2013...mechanics.html , for example.

If there is a more complicated part that your team wishes to use, I suggest posting in the official forum. You don't want a hardware inspector to rule that a part is illegal when you get to an event.

[pilum40]

Thank you for the replies. i truly was clueless about the definition until now. I do appreciate the patience shown by everyone. I'll hit the motor list and see if we still have any Tetrix parts in a "use them someday for something" bin we keep in my classroom closets. lol This is a bit different than FRC