Motors: Past and Future

[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.

[R.C.]

Originally Posted by Gregor

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

That's a fair comparison, we won't consider using the 550 over the 775 in the current motor allotment so for us its a $74 difference. Either way its just a personal preference, I tend to spend more .

[caboosev11]

Snow blower motors. We all should clearly absolutely totally use those.

[Ragingmain]

First Post
Ok, so I have gone through the search for over 20 mins and have also read last years rules and I cannot find where it prohibits using a DC/DC converter to raise the voltage to 18vdc to run a RS-775-18 at 18vdc. Wouldn't this be covered under custom circuits?

Whether or not that would be advisable is a different question.

Thanks in advance for your patience

[BBray_T1296]

Originally Posted by Ragingmain

First Post
Ok, so I have gone through the search for over 20 mins and have also read last years rules and I cannot find where it prohibits using a DC/DC converter to raise the voltage to 18vdc to run a RS-775-18 at 18vdc. Wouldn't this be covered under custom circuits?

Whether or not that would be advisable is a different question.

Thanks in advance for your patience

I don't know why this would even matter.

The PDB will only supply 40A (at 12 volts) to a motor, or the individual breaker will reset.

That means that only 480 electrical watts can run through your motor anyways.

Stepping up the voltage to 18V drops your maximum amperage to just 26.6 amps.

I haven't looked at the specific motor torque/rpm/current curves, but barring inefficiency, they can only operate at the same maximum power

[Ether]

Originally Posted by BBray_T1296

I don't know why this would even matter.

It matters a lot. See below.

The PDB will only supply 40A (at 12 volts) to a motor, or the individual breaker will reset.

The breaker doesn't reset instantaneously.

Stepping up the voltage to 18V drops your maximum amperage to just 26.6 amps.

I haven't looked at the specific motor torque/rpm/current curves, but barring inefficiency, they can only operate at the same maximum power

The power you are referring to above is the input electrical power.

Operating at higher voltage makes the motor much more efficient. The output shaft mechanical power at 18 volts and 26.6 amps is much greater than the power at 12 volts and 40 amps.

[Lil' Lavery]

Originally Posted by R.C.

Personally I wish the motor rules were:

6 - Cims
4 - MiniCims
Unlimited Bags!

No need for any new motors.

As a mentor of a team that frequently uses the AM9015, PG-series, and window motors, I'm glad this isn't the case.