Motors and Servos - Answer Thread

[Administrator]

Answers to questions posted pertaining to Motors and Servos.

[Sheldon]

Hi, we'd like to upgrade the karbonite gears in our sail winch quarter scale servos to metal gears. There is no direct replacement and slight modifications are necessary as described here. http://ftcforum.usfirst.org/showthre...l-Gear-Upgrade. Is this modification/replacement allowed as described? Thank you

A: Yes, teams may replace the gears in their servos with metal gears.

[Sheldon]

The rules state that legal motors include the am-3102 motor (20:1 gearbox), the am-3103 motor (60:1 gearbox), and the am-3104 motor which is a motor with no gearbox. So, removing the gearbox and changing gear ratio is similar to using an am-3104 with a custom gearbox (hence, not modifying the motor). Is this gearbox modification legal?

A: Yes, this is legal.

[Sheldon]

Are we allowed to remove the encoder on the Andymark NeverRest Series? (AM-2964, AM-2964a, AM-3102, AM-3103, AM-3104)

We just need to shorten the overall length.

Thank you!

A: Yes, teams may remove the encoder from the NeverRest motors.

[Sheldon]

Are the EV3 motors and sensors legal?

A1: Only the motors listed in rule <RE09> are allowed. No other DC motors are allowed.

A2: EV3 sensors are allowed provided they meet the restrictions listed in Rule <RE11>.

[Sheldon]

Are we able to modify a 90 or 180 degree servo to make it continuous rotation servo? Specifically the Hi-Tec Servo Model HS-485HB which list Specifications as 360 degree Modifiable. http://www.andymark.com/product-p/am-2543.htm

A: Because the modification involves changing or modifying the gears and does not involve the electronics or wiring this modification is allowed.

[Sheldon]

Hi there! We just went through an inspection before our league meet and the inspector told us that we needed to have the servo movement stickers next to EACH servo that was on our robot, not just a single one to alert folks that the servos might move. In the past we only needed one and it's not exactly convenient for us to have a place to put those near every servo. Do we really need multiple stickers, or will one do for the entire robot?

A: Rule <RG03b> requires just one warning label located near the Main Power switch.

[Wil Wheaton]

Are we able to use these actuators on the robot?

Zowaysoon 12V Electric Linear Actuator 100m/4inch Stroke 1500N DC Motor Linear Motion Controller with Limit Switch

Stroke length:100mm(4inch)
• Voltage: 12VDC** Noise Value: >65dB
• Load/Thrust/Force Capacity:1500N =150kg(330Ib)
• Speed:5.7mm/s
• Duty Cycle: 25%** Protection class:IP54

Answer: No. The above linear actuator is not an allowed DC motor nor an allowed servo and falls under the <RE17> Additional Electronics rule

[Wil Wheaton]

Are linear servos allowed? There is no notion that they are, or are not. It is just the rotational ones that are allowed. Assuming the connection to the servo controller is the same, can a linear servo be used?

Answer: <RE10> does not constrain the nature of the output of a servo. For a servo to be legal, it must:

• be marketed/sold as a servo
• be electrically compatible with allowed Servo Controllers (6v and within the current limit for the controller)
• be controlled/powered by an allowed Servo Controller

Team using "unusual" servos should be prepared to support the legality of their servos by bringing documentation for the servo (specifications, etc)

[Raj]

My team and I were wondering whether it is legal per rule RG01J to remove air from a funnel using a vacuum pump. We are not compressing or storing air and there are no pistons or valves involved in the design. The vacuum pump is from Amazon: https://www.amazon.com/Karlsson-Robo.../dp/B00DYA21PU. We are not using the motor that comes with the pump. We are converting it to an AndyMark NeverRest motor. Inside the pump is a piece that spins. This pieces turns at an offset and makes the rubber part on the outside pump out the air from the funnel. There is only one degree of freedom in this design. Thanks so much!

A: We found out that it is a diaphragm pump. Our ruling is that as long as the outport port of the pump is not blocked or sent through a hose, the pump should not build up any pressure. If those constraints are followed, then this would be considered a legal part.