Commercial Off The Shelf Components

[Billie Jean]

Answers to questions about Commercial Off The Shelf Components.

[Broadway Joe]

Linear Actuators

Q: Can students build their own linear actuator from kits or individual parts again this year?

A: Yes, providing it does not violate any other rule.

[Air Jordan]

Subject: <RM02> Commercial Off-The-Shelf Parts - Linear Slide

Questioin: According to Rule <RM02>, commercial off-the-shelf parts are allowed if they do not violate the single degree of freedom rule. This rule allows linear sliders, but we're unclear on a specific type of linear slide: the Cascading X-Rail Slide Kit from ServoCity. Is this part allowed?

https://www.servocity.com/cascading-x-rail-slide-kit

Thanks.

Answer: Yes, the Servocity Cascading X-Rail Slide Kit is an allowed linear slide.

[Broadway Joe]

GoBilda Chassis Kit

IQ: s the Gobilda Strafer Chassis Kit legal? It appears to consist of legal parts, so am I required to buy the parts separately from the BOM, or can I just buy the kit?

https://www.gobilda.com/strafer-chassis-kit-no-wheels/

A: Yes, you may just buy the kit.

[Broadway Joe]

Karlsson Vacuum Pump

Q1: Is the Karlsson Vacuum Pump, part # ROB-10398 a legal part as long as we change out the motor to an approved motor.

Q2: Also, can a valve be used to release the pressure on the suction cup?

A1: Without knowing the internal construction of the vacuum pump it is impossible to give a definitive yes or no on this device. Any team using this pump will have to demonstrate to the Robot Inspector that it contains only one degree of freedom (and remember, that if it contains valves, each valve counts as one degree of freedom) and that there is no possible way for there to be pressure buildup on the exhaust side of the pump.

A2: Yes, teams may use a valve to restore ambient pressure to the suction cup.

[Broadway Joe]

Ratchets

Q1: Section <RM02> of Game Manual 1 says that ratchet wrenches aren't allowed because they have more than one degree of freedom, however if you detach the handle of a ratchet and use the rotating head of the ratchet is that illegal and if so why?

Q2: Secondly, are single direction bearings illegal?

A1: Ratchets are illegal because they contain two degrees of freedom, the Gear and the Pawl each have their own separate degree of rotation. Removing the handle does not change this.

A2: Single Direction Bearings are designed to take axial load in only one direction, they are legal. Based on your question you may be referring to One Way Bearings in which the bearing transmits torque between the housing and the shaft in one direction while allowing free motion in the opposite direction. These are legal.

[Broadway Joe]

Universal Joint

Q: We are designing an intake system for our robot and would like to put a 45 degree joint in the axles that rotate our intake wheels. We were thinking about using the universal joints sold by GoBILDA to accomplish this task, but we are not sure if it is considered a legal part since it technically has two rotational degrees of freedom, which potentially violates rule <RM02>. The axles themselves, however, will be in a fixed position and will only have a single degree of freedom. The piece is not all that complex, and we do not believe it violates the intent of rule <RM02>, which is to encourage teams to design their own mechanisms. Given the situation, can we use the GoBILDA Universal Joint on our robot?

A: Yes, universal joints are legal. Since one of the axis of rotation is coupled to the other, like gears in a gear train, this is considered a single degree of freedom mechanism.

[Broadway Joe]

Vex Claw

Q: In the illegal parts list there are two Tetrix grippers; however, the VEX claw (https://www.vexrobotics.com/276-2212.html) is not listed specifically to be illegal. May we assume it is legal?
Thank you.

A: Yes, this is an illegal COTS part.

[Broadway Joe]

Modified Gripper Parts

Q: Would a modified VEX Gripper Claw on which the Gears, and linkage arms were redesigned, and 3D printed be allowed? Would the redesign and exchange of parts meet RM02, RM04 and the answer #2 of Rover Ruckus Build and Inspection Commercial off the Shelf Components #2 Answer 2: In general, it is legal to remove a single degree of freedom part from a commercial off the shelf multiple degree of freedom mechanism and use the single degree of freedom part in a Robot.

It is legal to use the servo bracket (flat plate with through-holes) from the ServoCity gripper kit in a Robot. It is also legal to add Team designed and fabricated parts to the servo bracket to build a gripper or other mechanism. However, it is against the spirit of rule <RM02> to use the servo bracket and make copies or slightly modified versions of the remaining unused gripper kit parts and build a gripper for the Robot.

A: It is against the rules to use an illegal mechanism. Making minor modifications to improve performance or to get around the restriction is against the spirit of the rules.

[Broadway Joe]

Tape Measure

Q: Is it legal for robots to use an off the shelf tape measure to extend during navigating/parking. I found two old forum posts that seem to contradict each other.
"No, the steel rule in the tape measure is a COTS and is not a legal part."
https://ftcforum.firstinspires.org/f...2095#post12095

"Yes, a tape measure is essentially a torsional spring and is allowed."
https://ftcforum.firstinspires.org/f...4326#post14326

If a tape measure has both a spring and a lock it seems that would be two degrees of freedom, and therefore illegal. If a tape measure does not have a locking mechanism, but only a spring, then I am guessing that is legal. I am also guessing that it is illegal to modify a tape measure that has two degrees of freedom by removing the lock, since modifying an illegal part does not make it legal. Please straighten me out

A: Tape measures are a legal COTS for Skystone.