The 20 amps is just above the max burst for the motor but, how would these two setups differ in the real world? Which would provide more thrust?

Since the 11x7E is pulling less amps the watts are lower but that doesn't mean it's a less powerful setup, right? Being that both are x7 props with the SF just having more prop area I'm assuming the 11x7E would be faster and provide more thrust since it is turning at a higher RPM. Is that right?

I though I read somewhere that you could calculate thrust based on several parameters, including RPM, but I can't find it anywhere. Anyone know how to do this?

The other way is for me to check my spreadsheet with 8500 entries for motor/prop/rpm/thrust etc and match your rpm for each of those props.

Back in a minute!

11x7 APC E: My measurement from my thrust stand: 7770rpm = 1374g/48.52oz

From badcock - his figures tend to be just a fraction low: 7800rpm = 1334g/47.00oz

10x7 APC SF: I've never dared take one that high - safe rpm limit for that prop (as listed by the manufacturer) is only 6500rpm; from badcock: 7300rpm = 1268g/44.65oz

The 20 amps is just above the max burst for the motor but, how would these two setups differ in the real world? Which would provide more thrust?

Since the 11x7E is pulling less amps the watts are lower but that doesn't mean it's a less powerful setup, right? Being that both are x7 props with the SF just having more prop area I'm assuming the 11x7E would be faster and provide more thrust since it is turning at a higher RPM. Is that right?

I though I read somewhere that you could calculate thrust based on several parameters, including RPM, but I can't find it anywhere. Anyone know how to do this?

This illustrates one other thing - diameter is king when it comes to thrust.

Even tho the 10x4.7 prop had more power and was turning at a significantly higher rpm, it developed less thrust than the 11" prop.

Thrust is a function of two things - prop diameter and prop rpm.

Thrust goes up as the 3rd power of RPM but it goes up as the 4th power of diameter. In other words - if you double the rpm you get 8 times the thrust 2x2x2=8. But if you double the diameter you get 16 times the thrust 2x2x2x2=16.

So if all your concerned about is thrust - larger props are your friend

Hello frnds!
I am making a Quadcopter. I need to knw hw to calculate the thrust produced by the motor..
Motor : Park 250 Brushless Outrunner Motor 2200Kv
ESC : 10-Amp Pro Brushless ESC
Propeler : Slow Flyer Propeller, 8*6, SF
Battery : 3200mAh 2s 7.4v 20c

As noted in posts above, there is no simple way to calculate thrust. best way is to build a threust test rig and measure thrust, next best option is to use one of the online calculator tools to estimate thrust. for instance e-calc

I'm not sure that a 8x6 prop would be good for a quadcopter, you would normally be looking to have as large a diameter and as low a pitch as possible for a helicopter or quad.

As stated above, proper thrust is not easily calculated with only motor, esc, battery and prop info...particularly for copters!
The prop size you've given appears to have more pitch than what is generally used on any type of vertical lift craft......the size of the frame (dimensions), balance, weight, and vertical height from ground floor to blade are very important as well (info not provided).....

Thumb through these web sites (forum) and see what examples fit your application:

Yeah, the whole spec looks to be all screwed up. It's far too big a prop for a 2200kv motor and 10A ESC limit. The motor would want to pull 30-40 Amps with that prop!

Yeah, the whole spec looks to be all screwed up. It's far too big a prop for a 2200kv motor and 10A ESC limit. The motor would want to pull 30-40 Amps with that prop!

Do I smell burning?

Shhhh! No such thing as too many 'ESC burst into flames during the maiden' threads!

Ask me why your DX5e is doomed... and how to fix it.

Yeah, the whole spec looks to be all screwed up. It's far too big a prop for a 2200kv motor and 10A ESC limit. The motor would want to pull 30-40 Amps with that prop!

Do I smell burning?

According to eCalc that setup would pull 12 amps. I would change to a 20 amp esc and go with it.

Trying to equate watts to thrust has given people headaches ever since we started trying to put electric motors into models.

Change from an APC E series prop to a Xoar wood electric prop, keeping the same dia and pitch and you will change RPM, thrust AND watts.
(and demonstrate that the APC is more efficient) Then change to the APC SF series, again at the same dia and pitch (if within its RPM limits) and you'll get another set of numbers...

So... until you learn from experience you have to trust a calculator and/or the experience of others.

So keep "playing with" that logger... and writing down results.

And tie a fish scale to the tail for thrust at rpm, watts, volts A X B prop and Brand X "XXXXX" motor.

Turn in your data to the motocalc site. They like having actual numbers to compare with their calculations.

The data you log might help someone else some day.

According to eCalc that setup would pull 12 amps. I would change to a 20 amp esc and go with it.

Mike

E-calc said 16.5A when i just tried it (see attached)

The reason i was so far out on my estimate is that the motor efficiency drops though the floor and the watts go into heating the motor rather than spinning the prop. I assumed 75% efficiency which is a reasonable number for a motor within it's normal working range, but with that prop e-calc predicts only 42%

But end result is the same, it's FAR too much prop for the motor it can hardly turn it all all, motor overheats and dies!

The prop is also stalled making it an extraordinarily bad choice for a quad.

Trying to equate watts to thrust has given people headaches ever since we started trying to put electric motors into models.

Change from an APC E series prop to a Xoar wood electric prop, keeping the same dia and pitch and you will change RPM, thrust AND watts.
(and demonstrate that the APC is more efficient) Then change to the APC SF series, again at the same dia and pitch (if within its RPM limits) and you'll get another set of numbers...

So... until you learn from experience you have to trust a calculator and/or the experience of others.

So keep "playing with" that logger... and writing down results.

And tie a fish scale to the tail for thrust at rpm, watts, volts A X B prop and Brand X "XXXXX" motor.

Turn in your data to the motocalc site. They like having actual numbers to compare with their calculations.

The data you log might help someone else some day.

One thing to keep in mind, those prop thrust figures don't allow for the net prop thrust, where you've got to subtract the effects of the prop blast hitting the wings, landing gear, fuse and so on. That effect can be substantial.

DennyV
Retired and the days are just too short, busier than ever!

E-calc said 16.5A when i just tried it (see attached)

The reason i was so far out on my estimate is that the motor efficiency drops though the floor and the watts go into heating the motor rather than spinning the prop. I assumed 75% efficiency which is a reasonable number for a motor within it's normal working range, but with that prop e-calc predicts only 42%

But end result is the same, it's FAR too much prop for the motor it can hardly turn it all all, motor overheats and dies!

The prop is also stalled making it an extraordinarily bad choice for a quad.

one reason I like heads up. no guess work and you know exactly how it will perform first time, every time, awas well as thrust numbers, even on different props and cells if the motor is rated for a highere cell count