Motors: Past and Future

[AllenGregoryIV]

Originally Posted by JALV

I was looking through some Chief Delphi threads for history on how the FRC technology has developed over the years and I noticed that the motors have not changed much in recent time.

How long has the CIM ben around?
I noticed that there was a Bosch drill motor from years ago, why did they discontinue it in FRC?
Do you think there is room for a new company to develop motors and improve upon what has already been proven over the years?

Just last season (2013) we added the BAG motor and MiniCIM which were huge improvements. I'm pretty sure we have all the motors we need now. I haven't see to many robots that use all of the 200+W motors that are legal (6 CIMs, 4 MiniCIMS, 4 BB775/550s). Unless they decide to change a lot of the rules to allow stepper motors or brushless motors, I'm pretty satisfied with the brushed motor options available to teams.

[R.C.]

Personally I wish the motor rules were:

6 - Cims
4 - MiniCims
Unlimited Bags!

No need for any new motors.

[AdamHeard]

Originally Posted by R.C.

Personally I wish the motor rules were:

6 - Cims
4 - MiniCims
Unlimited Bags!

No need for any new motors.

I do like having 500 sized motors.

They're more power dense, which can be utilized if teams understand the failure mode from heat.

They're good for high bursts of power (like a 2013 shooter spinning up) with intermittent low load between.

[Gregor]

Originally Posted by R.C.

Personally I wish the motor rules were:

6 - Cims
4 - MiniCims
Unlimited Bags!

No need for any new motors.

That would be pretty expensive for teams.

[R.C.]

Originally Posted by Gregor

That would be pretty expensive for teams.

Vs Buying 550's? Eh, I wouldn't mind the $15-20 dollar difference for a better motor. We use the 775's over the 550's currently so its not a big difference in what we spend currently.

[AllenGregoryIV]

Originally Posted by R.C.

Vs Buying 550's? Eh, I wouldn't mind the $15-20 dollar difference for a better motor. We use the 775's over the 550's currently so its not a big difference in what we spend currently.

We're in the same boat, I'd be fine with just CIMs, MiniCIMs, BAGs, and 775s though most of the time we use 775s because we already used 4 MiniCIMs/Bags.

The 550s were useful in 2013 when we needed a lot of speed.

[Gregor]

Originally Posted by R.C.

Vs Buying 550's?

Yes. The only thing that steers me away from BAGs is their relative price. That being said, my robot this year consisted of 5 CIMs and a 775.

Using 8 BAGs vs. 8 550s (4 competition bot + 4 practice bot) is a difference of $148.

[Jared]

I'd like to see a motor that was a little more powerful than the 775 but packaged the same way, so that it could be used instead of the CIMs for drive. The reliability of the CIMs is great, but they're really heavy compared to a 775, and not that much more powerful.

[Lil' Lavery]

Originally Posted by Jared

I'd like to see a motor that was a little more powerful than the 775 but packaged the same way, so that it could be used instead of the CIMs for drive. The reliability of the CIMs is great, but they're really heavy compared to a 775, and not that much more powerful.

One crucial difference between a 775 and a CIM is how they're cooled. The 775s (along with 550s, AM9015s, FPs, Bosch drill motors, etc) are cooled via convection encouraged via the fan at the tail end of their shaft. That's why you don't want to stall these motors, since they need to be spinning at a relatively high speed to draw enough air to avoid overheating under load. The CIMs (along with MiniCIMs and BAG motors) are not cooled by fans, and instead rely on having a larger thermal mass to "absorb" the heat and prevent the motor from overheating. The heat is eventually dispersed via convection, conduction, and/or radiation away from the exposed surfaces of the motor (so having a larger surface area is important as well).

Since drivetrains often experience stall or near-stall conditions, it's important to have a motor that can survive stall or near-stall heating. Fan cooled motors are a poor choice for this (thus why so many Bosch drill motors failed back in the day). As a result, you need the additional mass to help these motors survive in a drivetrain. Of course, if you were to install some other cooling system this could be worked around, but I'd venture that the additional mass and space of the cooling system would outweigh the benefits.

I don't think you're going to get your wish.

[BBray_T1296]

The only improvement I could scrounge up about the CIM that would be quite beneficial was improving the heat release (body conducted heat away from the brushes faster/possibly incorporated a better heat sink, to make the motor more than just a 10% On 90% Off, perhaps up to a 50/50 or continuous duty without aftermarket passive or active cooling

[EricH]

My "dream" lineup for motors, current and past:

--CIMs (and variants--big, mini, bag), any combination but no more than 6 (Awright, quit complainin', 7).
--775s, 550s and the old FP motors (which were very similar), no more than 2 (maybe 4).
--Up to two Globe motors (need to specify allowed configurations, but those were very nice motors for light duty that was tough).
--Window and van door motors, no more than 4 total. For the right applications...
--Unlimited servos and VEX motors/servos (increase power on servos, though!)

--Additions: 2x brushless motors with speed controllers (restricted power/size, though, at least at first). The big thing here is that brushless motors are also known for not liking stalling, which would probably need to be pointed out to the teams.

[Richard Wallace]

Originally Posted by Lil' Lavery

One crucial difference ...

I don't think you're going to get your wish.

Sean has this exactly right. I am becoming more confident that he will be able to keep the Martian colony infrastructure operating smoothly, when the old timers of my generation are in our rocking chairs.

Just one point to add: power available from a motor falls off rapidly as the internal parts (i.e., brushes, armature windings, and magnets) get hot. This happens faster if the motor is smaller -- so even if a fan-cooled (e.g., 775) motor is nominally rated for more peak power than a totally enclosed non-ventilated (TENV) motor like a CIM, the TENV motor will deliver more power in all but the most intermittent of applications. Bottom line: stick to CIMs for your FRC drivetrain (duh).

[magnets]

Originally Posted by Richard Wallace

Sean has this exactly right. I am becoming more confident that he will be able to keep the Martian colony infrastructure operating smoothly, when the old timers of my generation are in our rocking chairs.

Just one point to add: power available from a motor falls off rapidly as the internal parts (i.e., brushes, armature windings, and magnets) get hot. This happens faster if the motor is smaller -- so even if a fan-cooled (e.g., 775) motor is nominally rated for more peak power than a totally enclosed non-ventilated (TENV) motor like a CIM, the TENV motor will deliver more power in all but the most intermittent of applications. Bottom line: stick to CIMs for your FRC drivetrain (duh).

I wouldn't say that as a blanket statement. Teams have been using 775's/FP's in drives for a long time. In 2003 and past, several of the Einstein teams, like 111, used non CIM's in drive, as you could only have two that year. Pretty much every team with swerve did the same Plenty of teams have also ran 2 CIM + 1 775 drives, like 254 and 118, which are both very successful teams.

With the available current monitoring feature on next year's PDB, stalled motors can easily be detected. It is true that a 775 will burn up quickly when stalled at 12V, but it can last a significant amount of time at 6V.

A minicim weighs 1.5 lbs more than a 775, and is less powerful. Given 1.5 lbs, I could add a decent heatsink and fan to a 775 for roughly the same total cost, and have more power.

Also, a more powerful 775 would be really useful in climbers/hangars, where you (ideally) never stall.

[asid61]

I like the way things are now. The only improvement I could see would be to use SSS-5940 10kw brushless motors in place of cims (they are the same size).
Oh, and raise the main breaker limit to like 600 amps.

[fb39ca4]

I'd love to see brushless motors.