# Why does arducopter use motor A, B, C, D as well as 1, 2, 3, 4?

To me, it’s SUPER confusing to see docs showing motors as 1, 2, 3, 4, etc, and Mission Planner say A, B, C, D.

Ughh…

There’s probably a good (controversial?) reason, but WHY does arducopter use two different methods to indicate which motor is which?

Especially when motor order/direction is SO important to flight safety.

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So when Motors are tested regardless of the frame type they run in the same order. That’s all you need to know when you run Motor Test to determined if you screwed up the Motor Order (as so many do). You could randomly connect the ESC’s to outputs, run Motor Test and re-order them knowing nothing else.

This is the logic, it’s good logic.

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ABCD is the motor order relative to the FC orientation. Take quadcopter X as an example, motor A would ALWAYS be the front right, motor B - rear right, etc.
1234 are the ESC outputs to which your motors are connected. You can assign the motor on the channel 4 to be motor B (Quad X) or you can assign the motor on the channel 2 to be motor B (Betaflight X), etc.
Why? To allow cleaner wiring and save you from the hassle of re-soldering motors to the correct pads since you can re-assign them programmatically instead.

Most of our frame classes also have a “CW X” frame type. Quad for example:

Hex:

ect.

They make it all very easy by having the lettering match the numbering. The wacky ordering as just a left over from before it was possible to reassign output functions to different pins but were stuck with it now as so many vehicles are flying with that configuration.

This is exactly why we have the A, B, C I do not need to know the configured frame type to know if the motor ordering is correct, front right is always A ect.

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OK - thanks very much guys. Yeah I figured I missed something in the logic. And not the first time.

One more question - Is a tricopter motors A, B, and C? Or is it A, B, and D?

Or maybe A, C, D?

Thanks…

Based on that question you have missed the point of the letter designations. Go here ESC and Motors
page down to " Checking the motor numbering with the Mission Planner Motor test", read what it says and then apply that to the Tricopter Frame type shown in the same link.

Note: The tail servo will move during the Motor Test also. Kind of a special case.
So starting from the front right and going clockwise (the key to the whole thing):
A-Front right
B-Rear
C-Tail Servo
D-Front Left.

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Thanks Dave -

Yeah I figured it’s A, B, C - but then on the other hand, a tripcopter is the only frame that skips a motor number (1, 2, 4), AND I have been having a heck of a time getting the motor settings correct.

Plus almost no one, apparently, builds tricopers anymore, so there’s not much current searchable information, so, I thought I’d ask.

But thanks again for pointing me in the right direction.

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After reading your post again you essentially got it right with A,B,D. Nowhere to my knowledge does it say which button activates the tail servo. I confirmed it in the simulator.
So, sorry for not acknowledging that you actually did have it right with published info!

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That’s too funny Dave - in my misunderstanding, I came around full circle to kinda getting it right.

Yeah I still have to figure out the tail servo (and am instead thinking about doing a Y4 or Y6 - after building a few quads, I’m just curious to watch a tricopter fly, and perhaps enjoy the redundancy of a Y6).

Thanks again for all your help.

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@wsalopek all you have to do is look at this code file for the translation between Motor number and A, B, C, D. Starting from this line, look at the MotorDef statements. The first one shows – in this order – 2, 4, 1, 3. That is the ABCD order.

how can I figure out which hexa I have, cw x or x?

You look at the motor order illustrations and set the order and direction accordingly. You determine how it’s configured and which Frame Type to use.

This thread really doesn’t need reviving…

I don’t understand your question. If you want Hexa CW-X set Frame Class to Hex and Frame Type to ClockwiseX

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cw this is ClockwiseX Thank you!!!