Twin motor plane - CW/CCW motor questions

[DbleDuce]

Greetings all!

I am in the process of building another mini guinea (actually 3 of them). I have a set of MT1806/2280KV motors (a basic CW/CCW setup) for only one of the planes.

Two of the new planes will be using the new FT 1806/2280KV motors but they are not available in a CW/CCW versions.

1) Setting up each plane with differential thrust, will having both FT motors spinning in the same direction impact the flight characteristics?
2) At this scale, does having counter rotating motors make a difference?

Thanks!

 

[Piotrsko]

Well you can use a pusher prop on one motor and change rotation via the motor wires, either brushed or brushless. Just make sure the prop nut is tight and check often. Might be a wee bit less efficient, but well within the trim range.

P factor is a function of prop size and speed. A 6" diameter prop has less torque steer than an 10"

 

[Monte.C]

Another similar answer:
You never have a need to run both motors in the same direction. Just switch wires on one; it's that easy. For props, there are so many more prop options available for quads, that include both CW and CCW in the package. Running both in the same direction is nonintuitive.

The thread on one of the motors will be the wrong way, but the locknuts we use hold just fine.

 

[quorneng]

DbleDuce
The other factor to consider is model planes are considerably over powered compared to full size, they have to be because the aerodynamics don't scale. The very highest power full size twins nearly always use counter rotating props so it is relevant to fit counter rotating on a model particularly with electric where full torque is produced at very low revs.
Of course models tend not to fly so near the stall where the prop torque really upsets things but with counter rotating you can snap open the throttle safe in the knowledge nothing will happen, except the plane will speed up.
Now if for some reason in a low slow full power situation one motor does not work then you are in real trouble just as you were in high power full size.

 

[Merv]

...Two of the new planes will be using the new FT 1806/2280KV motors but they are not available in a CW/CCW versions....

In a quad, using motors of the correct rotation is necessary, in planes not so much. The difference, in quads the motor is starting and stopping many times per second, these "adjustments" allow the quad to remain stable. It's this starting and stopping that cause the prop to loosen. Running a motor, the opposite direction that the threads were indented, greatly enhances this process. It's only the direction of the threads that determines if a motor is CW or CCW. In planes, the motor runs more or less at the same speed, the direction of the threads is far less critical.

Go-ahead and run your motors in a counter rotation setup. Just give the prop nut a good snug with a wrench or plies and you will be fine. This is just not the issue it is in quads.

FYI, the prop coming loose is as a problem with glow engines. With a glow engine the prop is used as a fly wheel, the momentum from the prop is used to rotate the motor past the compression stage. When the engine fires, the prop speeds up, until the next compression stroke. This constant change is speed WILL loosen the prop nut, similar to a quad.

 

[DbleDuce]

Thanks everyone,

My biggest concern was a prop coming loose but all your information was very helpful.