Help! Electric motor power

[makem&breakem]

Hi guys just went flying with a twin flying machine but the two motors I had knocking about did not want lift the plane off the ground the two motors are unmarked so I do not no the rating so just remind me does more revolutions produce more thrust or what?

 

[quorneng]

Foe a particular prop more revolutions (within reason) does give more thrust but a lot depends on how you achieve the extra revolutions.
Any motor has a maximum power rating measured in amps. Increasing the battery voltage will raise the revolutions but it also increases the amps the motor draws which may then go over the maximum the motor can handle without over heating.. The ESC and even the battery have a maximum amp limits too.

The power required to fly a plane is directly proportional to its weight so if it wont fly then either increase its power or reduce its weight and preferably both as the same time!

If you can post a picture of the motor and details of the prop you are using someone here may be able to recognise the motor and advise on what is possible.

 

[Merv]

...but the two motors I had knocking about did not want lift the plane off the ground...just remind me does more revolutions produce more thrust or what?

Knocking inside a motor is not good, it's hard to tell the cause. It could be some kind of sand, grit or loose metal inside the motor. It could be the motor is not perfectly round any longer.

With an single prop, the faster you spin it the more thrust it will produce & the harder it will pull on the motor. If the prop is pulling the motor too much, the motor will overheat & burn out. You will need a smaller prop or less RPM's to prevent burn out. That is, lower battery voltage or a lower Kv motor.

The Kv of a motor is how many rpm’s per volt. The higher the Kv the faster it will spin, likewise the higher the voltage the faster it will spin.
When we talk about Kv and prop size, think transmission. High Kv motors (2200) need smaller props and are similar to high gear in a transmission, little lugging power but goes fast. A lower Kv motor (1200) will swing a larger prop and is similar to low gear in a transmission, lots of lugging power but limited speed. A tractor and a race car may both have the same horsepower, one is built for speed and the other for pulling large loads. With electric motors, the power is measured in watts, more watts is more power. Kv, is what speed do you want the power, high Kv motors are for flying fast, low Kv motors are for lifting heavy loads.

 

[makem&breakem]

Knocking inside a motor is not good, it's hard to tell the cause. It could be some kind of sand, grit or loose metal inside the motor. It could be the motor is not perfectly round any longer.

With an single prop, the faster you spin it the more thrust it will produce & the harder it will pull on the motor. If the prop is pulling the motor too much, the motor will overheat & burn out. You will need a smaller prop or less RPM's to prevent burn out. That is, lower battery voltage or a lower Kv motor.

The Kv of a motor is how many rpm’s per volt. The higher the Kv the faster it will spin, likewise the higher the voltage the faster it will spin.
When we talk about Kv and prop size, think transmission. High Kv motors (2200) need smaller props and are similar to high gear in a transmission, little lugging power but goes fast. A lower Kv motor (1200) will swing a larger prop and is similar to low gear in a transmission, lots of lugging power but limited speed. A tractor and a race car may both have the same horsepower, one is built for speed and the other for pulling large loads. With electric motors, the power is measured in watts, more watts is more power. Kv, is what speed do you want the power, high Kv motors are for flying fast, low Kv motors are for lifting heavy loads.

Hi thanks for that you have explained that very well.

 

[makem&breakem]

Foe a particular prop more revolutions (within reason) does give more thrust but a lot depends on how you achieve the extra revolutions.
Any motor has a maximum power rating measured in amps. Increasing the battery voltage will raise the revolutions but it also increases the amps the motor draws which may then go over the maximum the motor can handle without over heating.. The ESC and even the battery have a maximum amp limits too.

The power required to fly a plane is directly proportional to its weight so if it wont fly then either increase its power or reduce its weight and preferably both as the same time!

If you can post a picture of the motor and details of the prop you are using someone here may be able to recognise the motor and advise on what is possible.

Thanks for the info.

 

[Shurik-1960]

Each motor has its own characteristics. The wattmeter allows you to choose the screw for the motor most correctly. Any motor can be overloaded with a large screw and it can burn out. Without a wattmeter, I used my hand to determine the degree of heating of the motor when working for 3-4 minutes on the stand.A bicycle will never go faster than a motorcycle, even with huge wheels....Watmeter- regulator rescuers : a large screw- a large current consumption by the motor - the death of the regulator at critical currents.

 

[makem&breakem]

Each motor has its own characteristics. The wattmeter allows you to choose the screw for the motor most correctly. Any motor can be overloaded with a large screw and it can burn out. Without a wattmeter, I used my hand to determine the degree of heating of the motor when working for 3-4 minutes on the stand.A bicycle will never go faster than a motorcycle, even with huge wheels....Watmeter- regulator rescuers : a large screw- a large current consumption by the motor - the death of the regulator at critical currents.

Thanks for the info mate with electric power and no info on what is required on a scratch build plan it gets very complex and technical but trial and error should sort it out.