CW vs CCW

[hellogoose]

I've read the other threads on this but still don't understand:
I though CW and CCW was only for glow motors and you can change motor direction by switching 2 of the 3 wires?
Edit: It's the motor cap, not the motor, what is a CW or CCW motor cap(and what does the motor cap even do...)
And what about props, what is the difference between CW and CCW, does it really matter?
Thanks!!!

 

[quorneng]

There is no difference between a CW and CCW prop of the same pitch and diameter except for the direction of rotation they are designed for. The blades are twisted the opposite way.
The motor torque required to turn the prop can have a significant on how a plane flies so for some high powered twin engine designs one prop is CW and the other CCW so the torque effects are cancelled out but that assums both engines are running.

As you pointed out a brushless motor direction of rotation can be changed by changing over 2 of its three wires.
A brushed motor can be reversed by simply changing over its two wires but some brushed motors do have a "designed" rotation so there can be enhanced brush wear if set to run the wrong way.
"Motor cap" is not a phrase I recognise in relation to motor direction. Some brushed motor do have a capacitor added to reduce radio interference but it is normally a film type which works regardless of polarity.

Some 2 stroke IC engines (eg Cox) can run in either direction but the rotation of all 4 strokes is fixed by the timing of their valve gear.
I hope this helps

 

[LitterBug]

The threads on the top of the motor can have reversed threads. You should not be able to swap the prop nuts between a CW and CCW motor without cross-threading the nuts. The threads are chose based on the rotation of the motor so the prop nut will tighten under load. That is the main difference between the motors. As far as props go, If you spin them the wrong direction you will reverse the thrust and potentially have less thrust if you reverse the direction from what the prop was designed. Some models have a thrust angle built into the motor mount to compensate for the torque roll that the motor/prop create when running. If you use a setup that runs backwards from this, the torque roll can be exaggerated. On a two prop plane, running each side in the opposite direction will counter the toque roll effect.

On a Multirotor, the flight controller expects a certain direction for each corner so it can change the motor speeds to yaw the vehicle. If the direction isn't correct, the multirotor will be unflyable.

 

[Bricks]

Back when for reverse running a glow we would double nut the propeller nut to lock it in place. We have started to do this with four stroke glows as if run lean they back fire and will throw the prop, don`t be standing in front of it if this happens.

 

[Merv]

... what is the difference between CW and CCW, does it really matter?...

In quads, it matters a lot. It takes 2 CW & 2 CCW props for a quad. And it matters on which arm they are installed. Get them on the wrong arm and your quad will immediately flip uncontrollably.

In planes, it doesn't matter very much. Provided you make the prop spin the way it was intended. The numbers must always face the direction the plane is going. As LB said, if you use a prop backwards, you will only get about 40% of the expected thrust. In a twin motor plane, use a CW prop on one side and a CCW on the other.

 

[hellogoose]

Thanks!!!

The threads on the top of the motor can have reversed threads. You should not be able to swap the prop nuts between a CW and CCW motor without cross-threading the nuts. The threads are chose based on the rotation of the motor so the prop nut will tighten under load. That is the main difference between the motors. As far as props go, If you spin them the wrong direction you will reverse the thrust and potentially have less thrust if you reverse the direction from what the prop was designed. Some models have a thrust angle built into the motor mount to compensate for the torque roll that the motor/prop create when running. If you use a setup that runs backwards from this, the torque roll can be exaggerated. On a two prop plane, running each side in the opposite direction will counter the toque roll effect.

On a Multirotor, the flight controller expects a certain direction for each corner so it can change the motor speeds to yaw the vehicle. If the direction isn't correct, the multirotor will be unflyable.

What is the point of different diffraction threads?

 

[LitterBug]

Thanks!!!

What is the point of different diffraction threads?

If done right, the prop nut will self tighten by the rotation of the motor and prop.

 

[hellogoose]

Ohhhhh!!
Does that mean that if I have a reversed thread, the nut will untighten with time?

 

[quorneng]

Yes. A conventional prop adapter is meant for use with a CCW prop. This ensures the nut will self tighten.
Quad motors do not use prop adaptors but have threaded shafts with the thread reversed where CW props are required. They have an appropriate nut supplied.
If you use a motor and prop adapter in a pusher configuration and reverse the motor to use a conventional CCW prop then it will likely undo the nut sooner or later. The more powerful the motor the quicker that is likely to happen.
The simple solution is to use a CW prop in a pusher lay out meaning the motor does not have to be reversed so the nut will self tighten.
If you have to use a CCW prop in a pusher then a double nut can be used.

Once the first nut is suitably tight on the prop then by using two spanners the second nut can be tightened without over loading the plastic of the prop hub. The twin nuts are thus locked together so are not loosened by the motor rotation.

 

[LitterBug]

Yes. A conventional prop adapter is meant for use with a CCW prop. This ensures the nut will self tighten.
Quad motors do not use prop adaptors but have threaded shafts with the thread reversed where CW props are required. They have an appropriate nut supplied.
If you use a motor and prop adapter in a pusher configuration and reverse the motor to use a conventional CCW prop then it will likely undo the nut sooner or later. The more powerful the motor the quicker that is likely to happen.
The simple solution is to use a CW prop in a pusher lay out meaning the motor does not have to be reversed so the nut will self tighten.
If you have to use a CCW prop in a pusher then a double nut can be used.
View attachment 255001
Once the first nut is suitably tight on the prop then by using two spanners the second nut can be tightened without over loading the plastic of the prop hub. The twin nuts are thus locked together so are not loosened by the motor rotation.

I'm curious to see the rest of this plane.

 

[quorneng]

The picture of the locking nuts dates from 2018.
It was my first attempt to create big printed parts for a plane. A big(ish) simple pylon pusher with a built up Depron wing and tail well suited for flying on my rough grass field. A 3000mAh 3s in the nose gave substantial endurance.

It still flies with a new stronger wing and a 6000mAh 3s in the nose.

At 853g (30oz) but is powerful and heavy enough to handle quite windy conditions. It can also stay up for over an hour if required.

 

[Bricks]

In quads, it matters a lot. It takes 2 CW & 2 CCW props for a quad. And it matters on which arm they are installed. Get them on the wrong arm and your quad will immediately flip uncontrollably.

In planes, it doesn't matter very much. Provided you make the prop spin the way it was intended. The numbers must always face the direction the plane is going. As LB said, if you use a prop backwards, you will only get about 40% of the expected thrust. In a twin motor plane, use a CW prop on one side and a CCW on the other.

It can matter on planes as many balsa builds have an added right thrust to compensate for prop thrust.