8 MINI-CIM SWERVE

[Kevin Ainsworth]

Would any one else like to see (8) MINI-CIM motors allowed so the swerves can be on par with the (6) CIM tank drives?

Looks like an 8 MINI-CIM motor swerve drive would be very close to power and weight of 6 CIM motor 6WD/8WD.

POWER
CIM 6 x 337 watts = 2022 watts total power
MINI-CIM 8 x 230 watts = 1840 watts total power
Within 10% instead of down 50%.

WEIGHT
CIM 6 x 2.80 lbs = 16.8 lbs
MINI-CIM 8 x 2.16 lbs = 17.28 lbs

Seems like the current rules favor a 6 CIM tank over a 4 CIM swerve for acceleration and top speed. I personally would like to see this somehow corrected. Maybe separating BAG motors from the MINI-CIM motors and a allowing 8 MINI-CIM motors?

This could be calculated by adding the watts of all motors used with a not to exceed. Or even more simply a CIM=1 and a MINI-CIM=.66 or .75 and a maximum of 6 when added up.

What's your thoughts?

[nuclearnerd]

I'm not averse to the rule change, especially if limiting total power is the aim of the rules. 8 mini cims ~= 6 cims.

The performance gain might not meet your expectations though. A tank drive will be better at putting that power to the ground (in a straight line anyway). When accelerating or pushing, the bot will "squat" toward the back wheels. As the weight comes off the front wheels, the force they can apply may become traction-limited, rather than power-limited. In a tank drive the front wheels and back wheels are chained together, so the weight distribution doesn't matter, but in a swerve drive, those front motors may spin uselessly.

The math on how big an effect this is is left as an exercise for the reader

[Nuttyman54]

I disagree 100% that there needs to be any rules allowing 8 Mini-CIM motors.

For one, there's already an incredible amount of power in the kit. The more motors, the more opportunity teams have to overload the system.

Part of the FIRST challenge is choosing how to allocate resources and weigh different design options. There's no requirement that any teams use a swerve vs 6wd vs mecanum vs ball drive vs walker. Each team must make a choice based on what their objectives are. Nobody's arguing that a walking robot should have special rules to allow them more motors so they can perform equivalently to a 6wd, or that a ball drive should be allowed 20 extra pounds because it's heavy. It's a design consideration that comes with choosing a swerve drive, you are probably trading some drive power to get the extra maneuverability. If you think 6wd has an advantage over swerve because it has much better acceleration, make a 6wd.

Lastly, it is possible to get 6 CIM power with swerve-style drive, but you can't do it with a module swerve. Concentric swerves that distribut power from two (or even one) gearbox to multiple swerve wheels but are steered independently is a way to do it.

[Aren Siekmeier]

Why does the number of motors need to be divisible by 4?

These types of drive are already very common. I think there's more room for creativity when you are forced to distribute 6 motors evenly, or use 3/4 motors more efficiently. And Z₃ symmetry presents another challenge compared to Z₄, since there are no proper subgroups.

Also 8 MiniCIMs would leave no room for additional 40A circuits, which wouldn't be fantastic if we need to do any heavy-lifting outside the drivetrain.

[Lil' Lavery]

Where's the option for "No, the motor allowances are already overkill"

[Jon Stratis]

We already have more power available than needed. Allowing even more would just serve to make things hit that much harder, break that much quicker, and overall decrease our purpose here. I'd rather we saw less motor power and fewer things breaking from impacts!

[nuclearnerd]

Originally Posted by Jon Stratis

We already have more power available than needed. Allowing even more would just serve to make things hit that much harder, break that much quicker, and overall decrease our purpose here. I'd rather we saw less motor power and fewer things breaking from impacts!

I'm not against this idea either, but the problem as stated is that the rules give hard numbers for each type of motor, regardless of application. You could theoretically have a 6-Cim + 2 mini-cim drive which would be completely legal, but cause far more of the impacts you're afraid of. What's being proposed here is a more nuanced application of the rules to allow teams more flexibility in choice of motor, without increasing the maximum power output. That sounds sensible to me!

[nuclearnerd]

Originally Posted by Kevin Ainsworth

This could be calculated by adding the watts of all motors used with a not to exceed. Or even more simply a CIM=1 and a MINI-CIM=.66 or .75 and a maximum of 6 when added up.

This kind of formula would even allow the GDC to dial back the maximum total power equivalent (TPE) if they wanted to (as some commenters propose). Hypothetically backing down the limit from 6, to say, 5, would result in *less powerful bots*, but still allow teams to use the following combinations (for example):

4-Cim (divisible by 2 and 4, TPE = 4)
6-Mini-Cim (divisible by 2, 3 and 6, TPE = 4.5)
2-Cim + 4 Mini-Cim (divisible evenly by 2 only, TPE=5)
8-9015 motors (divisible by 2, 4, and 8, TPE=~4.8)

[Oblarg]

Originally Posted by compwiztobe

And Z₃ symmetry presents another challenge compared to Z₄, since there are no proper subgroups.

I chuckled.

Of all the things to describe with group theory, I must confess drive base configurations hadn't occurred to me.

[Max Boord]

Originally Posted by Lil' Lavery

Where's the option for "No, the motor allowances are already overkill"

Overkill is underrated.

The robot I drove in season had a 6 cim powered shooter (flingapult) 4 mini cim mecanum drive and 3 banebots to pickup. 8 mini cim drive would have been truly awsome.

8 mini cims would allow all 6 cims to be used on mechanisms and still be able to have a strong omni drive. 6 cim + mini cim tank drives would be breaker trippers in most cases.

[nuclearnerd]

Originally Posted by Max Boord

6 cim + mini cim tank drives would be breaker trippers in most cases.

Not with this year's PD board, and the ability to do closed-loop current monitoring

[Max Boord]

Originally Posted by nuclearnerd

Not with this year's PD board, and the ability to do closed-loop current monitoring

Good point. Although something tells me figuring out the exact tripping curve of a given main breaker at a given temperature would make a closed loop system very complex. Also, if your are limiting power on your 6 cim+ 2 mini cim drive why wouldn't you go with a simple 6 cim (and software limiters)? With 6 cims only providing a 20-30% acceleration boost over 4 cims, i can't really see how adding mini cims would be much of a gain in top speed or acceleration, not to mention the added complexity of custom or additional COTS gearboxes.

[Electronica1]

Originally Posted by Kevin Ainsworth

Would any one else like to see (8) MINI-CIM motors allowed so the swerves can be on par with the (6) CIM tank drives?

Looks like an 8 MINI-CIM motor swerve drive would be very close to power and weight of 6 CIM motor 6WD/8WD.

How would you fit two motors inside a wheel?

[EricH]

Originally Posted by Electronica1

How would you fit two motors inside a wheel?

You'd use one to drive the wheel and one to turn the module.

[Electronica1]

Originally Posted by EricH

You'd use one to drive the wheel and one to turn the module.

But that would not allow you to have similar power to a 6 cim tank drive, which is the point of the 8 mini-cim argument right? (I might be missing something) You could have more than 4 modules in order to match the 6 cim power I guess.