# Horsepower needed to lift 600 lb load, w/8 motors

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1. Mar 3, 2015

### mootz

Good day Geniuses.

im building a drone prototype for an agricultural project.
approx. weight will be 600 lbs, using my own 8 rotor design.

trying to determine rotor size and motor power required to fly such a device at 30 feet.

would also be interested to determine an approximate wind speed and volume of air being moved, under the craft.

motor cost and size changes dramatically at a point, so 8 brush-less motors will be used.

2. Mar 3, 2015

### julianwitkowski

My first thought is that it sounds pretty heavy for an "agricultural project".
Does it HAVE to be 270 kg for a payload capacity?

I'm picturing something similar to a crop duster.
Have you built a smaller drone before?
You'll need to build some smaller RC planes to get your ideas down.

To find the answers to your questions you will have to be more specific about what you want.

Generally, everything you need for this is in Newtons 3 Laws...You might need to work with these laws using some light calculus, but that shouldn't be a problem.

Here is a good link that has lots of information about how Newton's laws apply to flying.
https://howthingsfly.si.edu/flight-dynamics/newton’s-laws-motion

Start here and work your way out... When you run into a road block, form it into a homework style question and ask in the general physics category, or dare I suggest the homework category. The template is great because it helps you organize your thoughts while you pose a question to the community.

Let me warn you, this isn't the type of place where people are dying to solve your math questions for you, the experts here are even greater than that and they will help you learn how to find the answers yourself if you're motivated to do so.

They really like to go by the old "Teach a man to fish" routine,

Last edited: Mar 3, 2015
3. Mar 4, 2015

### Staff: Mentor

There are generally two approaches to the problem, both of which require you to assume rotor diameter up-front. The first is to use Bernoulli's equation to find the velocity of the downwash from pressure and area of the rotors. The second is to use the definition of momentum change to find the force from the velocity. Either of which can then be converted to power using the definition of work.