STEM 10 Portfolio -KidWind TurbinesBY HARRY EVANSCL ICK P ICTURES OR ON SL IDES TO NAV IGATE

STEM 10 Portfolio

Rhino 3D Wind Turbines

Finish Presentation

Rhinoceros 3D Work w/ Mr Moore.

2D & 3D Drawing

BACK

Finish Presentation

Blade Creation Finishing & Printing

Accurate 2D Drawing

Our first task with Mr Moore was to run through a tutorial on the basics of Rhino 2D drawing - http://www.aversis.be/tutorials/rhinoceros/rhino_2d_drawing.htm. Although I had used Rhino previously it was good to pick up a few tricks and refresh my memory on what I’d covered two years earlier.

Accurate 2D Drawing

The tutorial showed us how easy it is to create organic, detailed 2D shapes. To start with we used a range of tools, shapes, lines and arrays to create a shape that resembled a sign for a nuclear power plant (see right).

Accurate 2D Drawing

From that point we started adding more detail on the inside. Again using shape and line tools we created the inner “cut-outs” and the centre piece. The final job was to round off all of the harsh corners with the fillet curves tool. The resulting image was this tri-pronged fan (see right).

Accurate 2D Drawing

After a little bit of experimentation I was able to create and extrude the surface of the fan and create this 3D model. To do this I used the Planar Curves and Extrude Planar Curves tools.The screenshot on the right was taken in a rendered perspective view.

SUPASPANNA CreationOur second task on Rhino 3D, was to go through another tutorial, this time made by Mr Moore. The objective was to create a 3D spanner, or in Mr Moore’s words, SUPASPANNA.

Multiple people in the class however, including myself, had done this tutorial in previous years, so were told to see what we could do without the tutorial. We were set a harder construction goal: a ring spanner (see right).

SUPASPANNA Creation

Figure 1: Ring Spanner Head

Figure 2: Spanner Head

After I got an idea for what a ring spanner was, I started constructing it in Rhino. I planned to do it in two different stages – first make the spanner heads and then the shaft.

I made the Spanner Head easily, by trimming a circle and set of lines. The Ring Spanner Head was a little harder to do, requiring me to trim two overlapping hexagons. This created the teeth that would grip a bolt

SUPASPANNA CreationHaving created the shapes of the spanner heads, I moved onto making the shaft. This would usually be quite easy, but the hook in it made quite difficult.In the end, I decide to build the side profile in front view and extrude out rather than up. I connected three 2.5 radius circles with the tangent to 2 curves tool, which gave me a nice round shape (see right)

Shaft Seen From Front View

SUPASPANNA CreationThe last part was to create and extrude the heads and shaft, and add finishing touches. Again using the Planar Curves & Extrude Planar Curves tools, I made it 3D and then filleted all of the corners with Fillet Edges. For aesthetical purposes, I also indented the handle using the Boolean Split tool.

This completed the SUPASPANA. I enjoyed creating it and found it more entertaining to do it without following a tutorial.

Finished SUPASPANA / RINGSPANA

Turbine Blade Creation

Sweep 2 Rails & Lofting Creations

During the middle weeks of Term 1, I begun working on creating my own blades for the kidwind kits. Mr Moore showed me a few tricks for making polysurfaces and I fiddled around trying to make a sword for practice. Using both the sweep 2 rails and loft tools I was quickly able to create quite detailed and well shaped blades.

With a little more effort I added a hilt, hand guard, and even a made shield! (see right)

Turbine Blade Creation

Base Shape & Rails

With these tools I was able to play around with creating an actual blade. My first idea was to use sweep 2 rails along an angling and shrink blade. Using OSNAP End and Rotate this idea was quickly arranged and just needed a base shape to extrude along the side rails. Creating a simple aerofoil shape with two curved lines, I was a able to make my first prototype for a blade.

Turbine Blade Creation

Blade Prototype I & Boss

With use of Polar Array I was able to create another 2 blades, 120° apart. I did this thinking that I would be a able to add a boss on the end and get it 3D printed. However there were two things wring with this idea:

1. The blades and Boss would be too big to print as one

2. I had no idea of any dimensions of the kidwind gear, so attaching it would have been inaccurate.

Turbine Blade Creation

Cross-Sections lined up along a curve.

Using the other method, loft, I made a much more detailed blade. Because loft uses cross-sections you can make each individual one a different shape, size and or rotation. The only negative about this is how tedious it is to create and align all of the cross-sections. After the best part of an hour I’d arranged multiple aerofoil shapes in a line ready for connecting (see right)

Turbine Blade Creation

Cross-Sections lined up along a curve.

The reason I used aerofoil shapes was to supposedly generate some lift which would help drive the turbine around. I also knew that they would cut through the quite smoothly especially with the curved trailing edge. Also I saw that the proper large scale turbine blades used aerofoil shapes.

Turbine Blade Creation

Finished Blade Prototype II

With the cross-sections lined up, shaped and sized appropriately, I created the lofted surface. With the help of Mr Moore I solidified it using a new tool; cap planar holes. This filled in the hollow shell that I’d created, making it a solid structure.

Using planar curves and extrude I added a 6mm rod, coming from the base of the blade. This finished my blade. With a little fiddling and cross-section angling it would be ready to be 3D printed.

Finishing & Printing

From my second prototype, I angle the cross-sections, so that as the blade swept along the curve, the pitch decreased.I also used 1D scaling to make the cross-sections get flatter. I didn’t like the equal thickness that ran down my old blade, and making it flatten out fixed that issue.

Angled Cross-Sections of Blade Prototype III.

Finishing & PrintingThe reason for the rotation and thinning of the cross-sections, was to prevent any unnecessary drag as the blade went out. When a blade spins, the far tip is travelling much faster than the inside base; this means that the to keep drag to a minimum, I needed to reduce the area of the blade leading into the wind. I did this by making the tip smaller, swept back and with a reduced angle of attack

Angled Cross-Sections of Blade Prototype III.

Finishing & PrintingWith the shaped finally ready, I lofted the surface, used cap planar holes to plug the ends, and again added a 6mm rod from the end. (see right)The next step was to export the rhino creation as a .stl file, allowing to go into the printer program. Sadly the MakerWare software on my computer was outdated so I wasn’t able to play around with the final printing preparations.

Finishing & PrintingAfter a disappointing result with our previous blades we came back to the drawing board for second attempt at creating good working blades. We had found that the blades created so far were not efficient at all, and needed to have a much higher surface area for the wind to catch. So we set about creating some new blades (see right) that should perform much better than the original creations.

Finishing & PrintingWhat I created was a large sail-like blade that was shaped less like an aerofoil. I thought that having a relatively flat blade that funnelled the wind out the back of it would create a very efficient blade. AS it turned the blades worked extremely well, but I definitely a result of the shape change as there were multiple other factors changed, such as overall surface area.

In Class Theory w/ Mr Crofts

BACK

Finish Presentation

Turbine Construction Blade Testing Efficiency Calculations

Turbine Building

In our second theory lesson with Mr Crofts we began work on our main project – testing and creating our own wind turbines. We used kits from the kidwind challenge to build and begin testing of different factors in the efficiency of wind turbines and propellers.

Turbine Building

The construction involved attaching a clamp to a wooden pole and tri-legged base. In that clamp we placed a small High Torque B1 Generator with 15mm cog attached (see Figure 1). Through the top of the clamp we ran an axel and “locked” it on either side with the larger 105mm cog and “stopper” (see Figure 2)

Figure 2: axel setup

Figure 1: cog setup

Turbine Building

The final step in construction was to attach the blades to the axel and then complete some basic testing. We took down notes of the variables in our experiment – blade length, distance from fan, angle of the blade – and conducted a control test. We found that our wind turbine gave an output of 0.0175V, with a resistance of 20 Ohms

Blade TestingOver the next 3 weeks we were limited in our testing due to long weekends, leaving only two afternoons. The first lesson, my group of Juke, James and myself began to test some more in-depth things, such as blade size and number of blades.

With the use of an anemometer we found that the wind was strongest in 250mm radius circle from the middle. This was very useful, but was expected as fan itself had a radius of about 250mm

Blade TestingOnce we knew where the strongest wind was, we decided to compare reducing the size our blades. We cut down our original Corflute blades to a length of 250mm. We found that this greatly improved the results (see below) and decided to leave all of our blades at that length.

400mm Blades

250mm Blades

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

Generator Output (V)

Blade TestingWe also tested how the amount of blades affects the speed. We started at 2 and worked our way up to 6. However we didn’t conduct a test with five blades, as the blade holder only has 12 slots and the blades wouldn’t be evenly spread out. From those tests we gathered the following results:

A good thing to note is the fact that we remove the drive cog in the generator rig. We thought that its instability was causing the mild fluctuations in our results. It made it more stable but the only gave about 1/10th of the output.

Blade Length

Blade Width

Blade angle

Number of blades Output (V)

250 77 30 2 0.08250 77 30 3 0.08250 77 30 4 0.08250 77 30 6 0.04

Blade Testing

We were able to determine that having 6 blades made the rig too heavy, which greatly affected the output. However the other three were approximately the same, so we decided to just continue using 3 as that is what our online research suggested.

Two

Three

Four

Six

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

Generator Output (V)

Blade TestingIn the second lesson we decided to test different shaped blades. By cutting a curved along a piece of balsa wood, I created a nice shape, then when attached it to a 6mm dowel. I then used electrical tape to tighten it , creating a curved aerofoil shape. Again, much like the 250mm blade test, we had massive increases in the voltage output (see below), reaching up to 1 volt. This is most likely due to the much smaller weight of the balsa blades as well as their additional shape. We also put the drive cog back in so we didn’t have to worry about our much smaller output results.

Corflute Blades0 0.2 0.4 0.6 0.8 1 1.2

Generator Output (V)

Blade Testing

We also tested the angle of attack or pitch of the blades, which is a blade’s angle across the wind. This means that 0° is perpendicular to the wind and 90° is parallel to it. We tested from 10° up to 50° where we stopped, seeing an evident trend in the results.

Blade Length (mm) Blade Width (mm) Angle of Attack No. of blades Voltage Output (V)250 77 10 3 1.65250 77 20 3 1.25250 77 30 3 1.05250 77 40 3 0.85250 77 50 3 0.67

10°

20°

30°

40°

50°

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Generator Output

An

gle

of

Att

ack

Blade Testing It is fairly clear to see that there is a trend in the results. The lower the angle of attack the faster the turbine spun. However what also occurred was that lower pitched blades took much more wind to get going; we nearly had to push the 10° one to get it to spin. Much lower than that and the fan most likely wouldn’t have been able to get the turbine going.

10°

20°

30°

40°

50°

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Generator Output

An

gle

of

Att

ack

Blade TestingWhen we got our blades they didn’t work very well and had multiple problems with them:• Firstly they were far too small and

didn’t have the surface area to catch all of the wind• Secondly when the blades were

printed some of the apparent 6mm dowels were too small, causing some blades to fly out and break.

Blade Testing

When we first tested my blades, 2 of the 4, flung out of the clamp and broke at the base of the dowel. This meant that I wasn’t able test with them and couldn’t to gather results. However it was very clear that they were nowhere near as efficient as the other blades we’d managed to create, even the original corflute ones.

Blade Testing These tests gave us multiple indications of what good blades would need. These are:◦ Not too much length as to reach out of the regions with the strongest wind◦ Lighter if possible◦ A swept back tip ◦ An angle of attack that is enough to get it going but also gets plenty of drive

With this I set about creating a second set of blades

Blade Testing When this new set turned up they looked much better than the other original ones I created, having a much better shape and far larger surface area.

The real shock came when we started up the fan. The blades started off slowly, then rapidly started speeding up, before we stopped the fan, fearful that they may again fly off. With the application of much tape we were able to gather results.

Blade TestingBlade Type No. blades Voltage Output Wind Speed () Efficiency

Printed Blades no. 2 3 2.95 3.5 10.58Printed Blades no. 2 4 4.6 3.5 20.57

Generator Output (V)

Efficiency

0 5 10 15 20 25

Four Blades Three Blades

Efficiency Calculations The blades that I had created turned out to be extremely efficient. When we put the data into the KidWind website to find the efficiency, we thought we must’ve put some of the data in wrong. We re-checked the wind speed, getting the same 3.5, and still got the same efficiency of 20.44%.

From there we went onto the KidWind website and realised that my blades would have been the highest score ever recorded on the site.

Efficiency Calculations We found that the second set of printed blades I’d made would have beaten every other submission on the website.

The other blades that we’d created gathered relatively low scores, as shown:

Balsa Blades Corflute BladesBest Voltage 1.65 0.18Efficiency 2.63% 0.03%

Thanks For Watching!HARRY EVANS