Start by quartering a 48 inch long piece of pipe around its circumference and cutting it lengthwise into four pieces. You can check the post on How To Cut The Blades for this.

This will end up being a wind generator blade assembly of just over 8 feet in diameter. Adjust your lengths according to your own preferences.

Remember that you will need a blade diameter of approximately 8 feet to achieve an output of 1000 watts with a 20 mile per hour wind speed. A couple things you should remember though. The most important is the tremendous force the wind can place on your equipment if your blades are too big. Let’s assume a wind speed of 55 miles per hour, that’s really a common speed out there. If your wind generator blade assembly has a diameter of 3 feet the force on the blades is approximately 115 pounds. But, if you up that blade diameter to the 8 feet (we recommend for most projects) the force of the wind on your wind generator at a wind speed of 55 miles per hour is an incredible 840 pounds of force.

Now, your blades are not catching all of that force of course, but they are catching a great deal of it. We design our wind generators to handle these forces. Design your tower, blade and hub assembly with that in mind. Light is good for spinning, but strong is better. It is sometimes hard to strike the right balance, but new materials and sometimes some surprisingly old materials make the choices easier.

Attaching the blades to the hub

The pulley that makes up the central part of your hub assembly must fit tightly on the shaft of the DC motor. The hub assembly must spin the DC motor in order to produce power.

We usually drill a hole through the pulley and shaft and insert a small one eight of an inch bolt and nut to hold the two together.

On the pulley (hub) you will have to measure the circumference, or distance around the outside of the pulley. For a three blade assembly you will divide this number by 3 to give you the distance between the blade mounting pieces of steel.

The following diagram shows the placement of the steel on the hub for use with PVC blades.

Note: when using wooden blades make sure to use 1 inch angle iron so that the blades are mounted at an angle to the wind. We have found 1 inch by 2 inch works about the best. The blades should be mounted at an angle of about 10 degrees to the wind.

The steel should be drilled with a one quarter inch drill bit at the same position on the hub for each piece. This will vary depending on the hub material used. The above diagram gives you a good idea of how to do it. Keep the holes at least one inch in from the outside if possible for strength and they should just meet at the centre of the hub. Take your time during this process and you will have a wind generator that is well balanced and spins well. You will be glad you did.

Mounting the Blade Assembly on the DC motor

First we need to do a bit of testing to see if your blade assembly is balanced. Just place the whole thing on a shaft of similar size and give it a few spins.

Make a note of the place it stops each time. If you notice that the same blade is always facing down at the end of each spin, then it is a wee bit heavier. Just give it a quick trim until none of the blades consistently stops at the bottom.

You can now do a test mount of the blade assembly on the shaft of the DC motor.

In our next post we will cover how to build a mount for the DC motor. Stay tuned

This is a walk trough to build a blade for your home made wind generator.

Your choice of blade design and material greatly affects your home made wind generator’s overall efficiency and performance. Most modern factory produced wind energy blades feature a 3 blade design with very slender blades made from space age materials mostly. Three blades work best to avoid vibration.

Those slender blades catch every bit of wind energy coming by too. You would think that the blades would have to be large in order to do this. But the most important aspect of blade design is how big of a diameter they form.

You will need a blade with outside diameter, measured to the tips, of at least 8 feet in order to achieve about 1000 watts of power production. If you don’t feel comfortable with this big of a machine then scale it back accordingly. Read more…

A 3 blade design can capture up to 8 horsepower of energy while many of the old bladed design will have a hard time producing 2 horsepower! All those blades get in the way of the wind moving through the blades and actually slow down the spin. This is what we regard as turbine efficiency.

Thankfully, the new materials and new blade design are available for us to take advantage from. These modern designs feature a high tip- speed ratio.

What is Tip-Speed Ratio?

Simply put, this is a comparison between angular velocity of the tip of wind generator blade and the wind speed.

Tip-Speed Ratio = Tip Speed / Wind Speed

Most of the newer models available today have a tip speed ratio of between 5:1 and 8:1. That is really moving. In other words, modern blades can rotate faster at lower wind velocities. The larger the number, the better efficiency in capturing wind energy.

This compares to the old slow moving water pumping windmills that used to dot the landscape with a tip speed ratio of around 1:1.

The old style windmills were designed to pump water, and although less efficient, they provided higher torque (because of the large blade outside diameter) and better performance at low wind speeds which gave them a steadier pumping action (more water delivered) in low wind situations. They had to start pumping immediately so they had to catch the wind at the start very effectively.

Home made wind turbine

If you think of your wind generator blades as aircraft propellers you will gain a new appreciation for the intricate designs necessary to achieve this high overall efficiency at tip speeds that approach 125 miles per hour.

You do not need to replicate these technical advances to have an efficient machine. Just follow the simple directions for a smooth operating homemade wind generator.

Note that the most efficient aircraft propeller design is not the best design for a wind generator blade. The propeller is designed to move air, while the wind generator blade is designed to be moved by the air. Subtle differences exist which we will explain further.