In this series I will be exploring some different robot parts that are commercially available to teams. The hope is that this will help determine which components you’ll want to use on your robot. Today I’ll be looking at motors. since this article is about helping you make motor selections for next year, I’ll be sticking to motors that were legal for Recycle Rush. All prices are as of July 2015.
- Price- $28.00
- Maximum Power-337 W
- Free Speed-5,310 rpm
- Stall Torque-2.42 N-m
- Weight-2.82 lbs
The CIM is the most widely used motor in FRC, and for good reason. It is an extremely reliable motor, it comes in the KOP, and has more power than any other motor. Most teams will use CIMs for their drivetrain, but they are very useful for other functions as well. While it is the largest and heaviest of the motors, you won’t be disappointed with its performance.
- Maximum Power-230 W
- Free Speed-6,200 rpm
- Stall Torque-1.4 N-m
- Weight-2.16 lbs
The Mini-CIM is exactly what the name implies. It has about 2/3 the power of a CIM, while also being smaller and lighter. It has a lower power-weight ratio than a CIM, but it is still a very durable motor that can be used very easily. Since it has the same mounting setup as a CIM, it can also be mounted to any of the gearboxes designed for a CIM. Teams will often use these motors in place of CIMs when they are trying to save weight or save their CIMs for other mechanisms.
- Maximum Power-147 W
- Free Speed-14,000 rpm
- Stall Torque-.4 N-m
- Weight-.71 lb
The BAG is designed to pack some power into a small package. While it’s power to weight ratio is better than most, it pretty much requires a gearbox for most usable functions. The addition of a gearbox can ratchet up the price for using this motor, especially since it has less power than the Mini-CIM (which costs the same).
- Maximum Power-273 W
- Free Speed-19,500 rpm
- Stall Torque-1.175 N-m
- Weight-.74 lb
The RS-775 might be the most valuable motor in your arsenal. It’s cheap, It’s light and it’s incredibly powerful. It has the best of power to weight ratio of all of the legal FRC motors, and is very easy to use. You will need a gearbox of some sort to make this motor usable for most applications, but this motor is very valuable in the battle against weight and space. Teams will often use larger motors in places they don’t need to, since the 775 is a powerful motor in an incredibly small package.
Note: This is the 18V version of the 775. the 12V version is basically the same except it has a lot less power. I highly suggest getting the 18V version.
- Maximum Power-253 W
- Free Speed-19,300 rpm
- Stall Torque-.486 N-m
- Weight-.48 lb
The RS-550 is the smallest motor you have but it still has a large amount of power. At less than half a pound, this motor is great for applications where you don’t need to use anything larger. 550s are very usable for intake wheels of many varieties, and if you gear it down enough they can be used on other manipulators such as arms. Banebots sells P60 gearboxes for the 775 and 550, which are great for making them usable in many applications.
An important thing to note about the RS-550 is that its production has been discontinued, making it likely that it will no longer be legal for FRC in the near future. There are plenty of alternatives out there to make up for the loss of a great motor. AndyMark sells lots of gearmotors for the 775 and 9015 that are very use to use. Since the 550 was a happy medium between the 775 and the 9015, teams are going to have to decide if they need more power or not, and which motor makes sense for them to use. BAG motors with a versaplanetary gearbox could also be a good substitute.
- Maximum Power-179 W
- Free Speed-16,000 rpm
- Stall Torque-.428 N-m
- Weight-.5 lb
The AM-9015 is very comparable to the 550 in terms of weight, size, and price, but has less power. While still a good motor, the AM9015 just doesn’t quite match up to the 550.
Snow Blower Motor:
- Maximum Power-20W
- Free Speed-100rpm
- Stall Torque-7.9 N-m
- Weight-1.1 lbs
The Snow Blower motor comes with an added worm gearbox built in that makes it a slow, high torque option. While it can be a little difficult to mount due to it’s obscure shape, it is a great option for a ready-made slow and powerful motor, instead of having to buy a separate motor and a gearbox.
Note: Window motors and door motors are very similar to the snow blower motor, so I’m not going to list them.
Here’s all of the above information in a convenient table:
|Motor||Price||Max Power||Free Speed||Stall Torque||Weight|
|CIM||$28||337 W||5,310 rpm||2.42 N-m||2.82 lbs|
|Mini-CIM||$25||230 W||6,200 rpm||1.4 N-m||2.16 lbs|
|BAG||$25||147 W||14,000 rpm||.4 N-m||.71 lb|
|RS-775||$18||273 W||19,500 rpm||1.175 N-m||.74 lb|
|RS-550||$7.25||253 W||19,300 rpm||.486 N-m||.48 lb|
|AM-9015||$7||179 W||16,000 rpm||.428 N-m||.5 lb|
|Snow Blower Motor||$39||20 W||100 rpm||7.9 N-m||1.1 lbs|
Hopefully this will help you in the future when deciding on motor usage. Being smart about your motors can help in the battle against weight and space. Stay tuned to this series for the next segment: wheels.