RS775 In Drivetrain?

[gpetilli]

Originally Posted by stinglikeabee

The RS series motors need active cooling to keep the enamel on the commutator shaft from melting. This is achieved in stock form by an internal fan and air ducts at the front and rear of the housing. The RS series motors are intended for power tools and R/C cars where they have plenty of air movement and are typically driven in one direction for a continuous period of time (not fast forward-reverse motion like the FRC robot).

I do not recommend using an RS motor for a critical, high load (high current) application such as the drivetrain.

I believe the 775 has a bad reputation because many teams block the air input vents. This is largely because many of the gearboxes (banebots and AndyMark CIM-Sim) cover the input air vents and the motors overheat. One year we used the banebots gearbox and ultimately machined channels in the gearbox mounting face (look at the VersaPlanetary mounting plates) and that made a HUGE difference in the temperature of the 775 motors.

If you do use the 775 in your drivetrain (or anywhere else) absolutely make sure it is well ventilated. If you use the CIM-Sim at least drill some holes in the plate where the motor mounts to allow air to enter the input vents.

That said, the drivetrain is arguably the most important subsystem on your robot. Do a risk/reward analysis before moving from the miniCIM to the 775. Is there anyplace else you can save a few pounds?

[JamesCH95]

Originally Posted by gpetilli

I believe the 775 has a bad reputation because many teams block the air input vents. This is largely because many of the gearboxes (banebots and AndyMark CIM-Sim) cover the input air vents and the motors overheat. One year we used the banebots gearbox and ultimately machined channels in the gearbox mounting face (look at the VersaPlanetary mounting plates) and that made a HUGE difference in the temperature of the 775 motors.

If you do use the 775 in your drivetrain (or anywhere else) absolutely make sure it is well ventilated. If you use the CIM-Sim at least drill some holes in the plate where the motor mounts to allow air to enter the input vents.

That said, the drivetrain is arguably the most important subsystem on your robot. Do a risk/reward analysis before moving from the miniCIM to the 775. Is there anyplace else you can save a few pounds?

Winner winner, chicken dinner.

As a team that has successfully used the 775 in numerous applications with no failures (arm motors in 2011, stalled to hold arm position; shooter motors in 2012; climbing motor in 2013; intake motors in 2014) ventilation in continuous-use applications is strongly recommended. Make sure you're operating in the higher-half of the RPM range too, they tend to heat up otherwise.

IMO 775s would do fine in a drive-train that was driven at high speeds and would not do well in a drive-train that was mostly driven at low-throttle values. This is entirely based on the heating/efficiency of the motor - look at the motor curve and seriously consider where on that curve the motor will generally be operating. For this game, with lots of low-speeds and fine-positioning moves, it might not be a well-suited motor.

Also bear in mind that drive-train weight is generally low in the robot. Removing mass from components higher off of the ground than the drive-train will have a larger positive impact on the robots overall dynamic performance.

[Tom Line]

Originally Posted by gpetilli

I believe the 775 has a bad reputation because many teams block the air input vents. This is largely because many of the gearboxes (banebots and AndyMark CIM-Sim) cover the input air vents and the motors overheat. One year we used the banebots gearbox and ultimately machined channels in the gearbox mounting face (look at the VersaPlanetary mounting plates) and that made a HUGE difference in the temperature of the 775 motors.

If you do use the 775 in your drivetrain (or anywhere else) absolutely make sure it is well ventilated. If you use the CIM-Sim at least drill some holes in the plate where the motor mounts to allow air to enter the input vents.

That said, the drivetrain is arguably the most important subsystem on your robot. Do a risk/reward analysis before moving from the miniCIM to the 775. Is there anyplace else you can save a few pounds?

775's have another black mark against them - that's the shorting issue teams had when they were first released. There's nothing more frustrating than having to repeatedly change out 775 motors during inspection because of internal debris causing shorts that ground your PD board.

We haven't used them since that year. Fool me once, etc. Many other teams have used them since then.

We used 550's very successfully on our drivetrain in 2008. That year, however, you were generally trying to drive at full speed. This year, there is a lot of slower-motion movement aligning, adjusting, and setting things down. That means that any low mass air-cooled motor is not going to be terribly happy. Active cooling on the motor (a fan) will help tremendously.

[protoserge]

Originally Posted by Tom Line

775's have another black mark against them - that's the shorting issue teams had when they were first released. There's nothing more frustrating than having to repeatedly change out 775 motors during inspection because of internal debris causing shorts that ground your PD board.

We haven't used them since that year. Fool me once, etc. Many other teams have used them since then.

We used 550's very successfully on our drivetrain in 2008. That year, however, you were generally trying to drive at full speed. This year, there is a lot of slower-motion movement aligning, adjusting, and setting things down. That means that any low mass air-cooled motor is not going to be terribly happy. Active cooling on the motor (a fan) will help tremendously.

This is absolutely a huge issue. Case shorting is directly attributed to overheating the enamel on the commutator shaft. The BaneBot transmissions that blocked the air intake vent were the leading cause of failure when this issue was present in 2010-2012. Many of the newer transmissions I've seen have this air intake slot already machined into the transmission.

If you have a transmission without an air intake slot, it would be best to mill a slot for air intake.