08/10/2020 at 15:12 •
I posted some information about the development and the build of the mechanical brake in the project log of the Nerdiskerator. Because it's also one of the main security features of winDIY i think its worth mentioning here. (I do not want to post the same content in two project logs) You can find the full log here: https://hackaday.io/project/172445/log/182044-brake-actuator-next-try
Here is some (teaser) content: :)
08/06/2020 at 17:54 •
It has been a little quieter here lately. But that wasn't because I was idling. :D In the meantime, the pitch actuator has gone through three iterations. But more on that later.
The last few weeks I've mainly worked on the pitch actuator but also on the wind vane. I have finished a draft for the wind vane and have already partially assembled it. More about this in a separate log. :)
In addition to the (hopefully final) design for the pitch actuator, I also worked on the brake actuator for the Nerdiskerator. I will post more on the nerdiskerator's project log soon. (Link: https://hackaday.io/project/172445-nerdiskerator-a-3d-printed-disk-generator)
The first design for the Pitch Actuator worked, but it took far too long to adjust the blades. The stepper motor needed almost ten minutes for a complete journey from end position to end position.
Clearly too slow to be able to react quickly to a rotation-speed change.
Pitch actuator Mark 2
So I thought I would just replace the stepper motor with a small DC motor. On the search for a motor I oriented myself more towards what I had available at home than what was needed for this purpose. Spoiler: I should have looked at the data sheet.
As you can see, the motor has enough speed for a quick adjustment. Unfortunately, a lot of torque was sacrificed to reach more speed. In addition, the motor draws almost 5A when it is blocked. Clearly too much. I have to admit that I chose the engine somewhat naively according to the motto "it will fit".
Pitch actuator Mark 3
So I went to the next draft. And with it to the next proof that before I start an additional printing process I should really check first that everything will fit. :D
In this design I used the same gear motor that I use for the brake actuator of the Nerdiskerator. This already has a reduction of 1:48 integrated into the housing. The motor pulls 500mA when blocked. That fits perfectly with the I2C motor driver DRV8830 that I want to use for control.
In the picture you can see that I did not notice that the vertically aligned motor would collide with the threaded rod when it was moved.
Pitch actuator Mark 4
For the Pitch Actuator Mark 4, I basically just turned the gear motor by 90 degrees. Photos and videos will follow. :)
07/20/2020 at 13:48 •
Yesterday I started designing the board for the Nerdiskerator-controller (See my thoughts about that here: https://hackaday.io/project/172445/log/181068-start-of-development-of-the-nerdiskerator-controller).
During this I also provided a slot for a micro SD card, for example to be able to save log files on it. It occurred to me that it is somehow a shame to use this SD card only to stuff it with .csv files. Especially if the development of WinDIY is largely completed, this SD card slot would be largely useless.
So I got the idea that WinDIY could not only be used to provide energy.
With the help of the SD card slot, WinDIY could also be used to provide information locally and independently of other infrastructure.
Since I plan to use an ESP32 as the heart of the controller, WiFi functionality is already available anyway.
It would therefore be easy to install a web portal in the controller firmware that enables information to be uploaded and downloaded to the built-in SD card via WiFi.
Because the wind turbine should be installed at a high location/pile, WiFi reception would be good.
A couple of usecases I have in mind are the following:
- If WinDIY is used in disaster regions where communication has broken down, information could be disseminated in this way. For example, rules of conduct, survival tips, repair instructions and more.
- In isolated regions, information could be provided in this way that enables orientation. A WinDIY in Alaska could, for example, supply hikers who have strayed from the path with maps. Plus electricity for the possibly empty GPS or cell phone batteries. The information on the WinDIY hotspot could also include building instructions for a shelter or instructions for obtaining/treating drinking water. Also an overview of which local plants are edible (or not edible) would be helpful. Possibilities for making an emergency call could also be saved on it. If available, an emergency call via a Lora (relay) network could also be made in this way.
- In developing countries, the "WinDIY hotspot" (this could be the name of the function) could contain teaching materials that make teaching possible/easier for the people living around it. In this way information could be distributed free of charge (and internet connection).
- Of course, all information such as instructions, material lists and STL files would be included on the SD card in order to repair/maintain WinDIY or clone it.
In order to make it easier to read all this information, a manual consisting of pictograms and / or QR codes would be included at the base of WinDIY, which uses pictures to explain which information can be found here and, above all, how to get there.
What do you think about that? :)
07/13/2020 at 12:41 •
While I'm working on the adjustments for the pitch actuator, I thought it would be time to present how I imagine the coupling between the main shaft and the generator.
In principle, I didn't invent anything new here and was mostly inspired by the principle of well-known shaft couplings.
You can see the well-known principle in the following picture:
It consists of two parts that are firmly mounted on the respective shaft part and are inserted into each other. A rubber buffer inserted between them dampens any vibrations that may occur.And here is my version of this type of coupling. I used cut pieces of a rubber mat as a damper. Unfortunately, it is very stiff. Maybe I will exchange this for a softer material. Otherwise, so far this principle seems to work well. :)
07/05/2020 at 14:04 •
So, I successfully tested that the current design for the pitch actuator was a failure. :D
The pitch actuator is the part that moves the threaded rod back and forth, which in turn adjusts the angle of attack of the wing.
The construction itself works exactly as I hoped (see video). Unfortunately, the stepper motor used (the well known 5V stepper 28BYJ-48) is clearly too slow to allow a quick adjustment of the angle. At first I thought "Oh it's not that bad" because it wasn't really meant to have to quickly adjust the angle of attack anyway. After the first complete test run, however, I noticed that a complete trip from end position to end position takes almost ten minutes.
That is a little too long for me. :)
But I already have an idea for improvement. At the beginning I had planned to install only two limit switches for the respective end positions and to determine the position in between by counting the step motor steps relative to the end positions. (Similar to the system used on 3D printers) In the meantime, however, I had the idea of making it possible to query the current position of the threaded rod using a sliding resistor.
This has the practical advantage that I can also use a normal DC motor (probably a "Reely R140") instead of the stepper motor. This creates a significantly higher speed (14000 rpm) and thus higher adjustment speeds. At the same time, the current position can be tracked using the sliding resistor. :)
Now that I know that the design works in principle, I just have to change the motor bracket a bit. :)
Please note that the video below is 20x faster than the original.
07/02/2020 at 15:07 •
In the last few days, I have completed a first design for the actuator, which will be used to control the pitch/angle of attack of the wings.
Since I recently found some cool tools for designing gears (https://hackaday.io/project/172445/log/180101-test-stand-for-the-nerdiskerator) I was able to use them here too.
A small gear is mounted on the axis of the 28BYJ-48 stepper motor. This then drives the larger gear which is firmly seated on the M6 threaded rod.
Since the threaded rod is mounted in a nut, which in turn is permanently installed in the holder of the stepper motor, a rotation of the threaded rod will hopefully result in a forward or backward movement of the threaded rod.
Hopefully this should adjust the disc in the hub of the rotor and thus the pitch of the blades. :)
So that the current position of the M6 rod can be measured, I have installed a sliding resistor so that it is taken along by the back and forth movement of the gear/rod. So you would have to be able to use an ADC later to measure the position of the M6 rod.
Everything a little difficult to describe. So here are a few photos. As soon as I have a complete set up, I will also post a video. :)
06/24/2020 at 13:53 •
The last two weeks I have been working on redesigning the main axis of WinDIY. The old axis worked, but had two problems.
The first thing, it was/is quite loud. I used angular ball bearings because they are actually perfect for absorbing forces in the axial and radial direction. Conveniently/unfortunately, the gap (between the bearing components) is adjustable with these. That means you can decide by the dimensions of the housing parts how close together the individual bearing parts are.
Unfortunately I never managed to set these properly. (Maybe I also lack the experience with these kind of bearings.) Also in order to not make the structure even more complicated, I decided to replace the angular ball bearings with radial bearings. These can take about 10% of the radial load in the axial direction. So if you install a radial bearing that is oversized accordingly, it should also fit with the forces in the axial direction. :)
(And I am sure that I will find another use for the - now remaining - angular ball bearings.: D)
The second problem is that the old connection between the shaft mount and the rest of WinDIY consists of 3D printed parts. I suspect that this will not last in the long run because this point is exposed to changing forces from the front (due to wind pressure) and the weight of the wings and hub.
I tried to show what I suspect in the picture. The whole 3D printed structure will experience forces in the direction of the arrows. Plus vibrations from the components, which may not be perfectly balanced. All of these forces are ultimately dissipated into the rest of Windiy 's structure via the spot marked with the flash.
Therefore the flash marks the point where I assume that this structure will not last very long.
That's why I decided on a redesign, which you can see below. :)
The new design
The new design of the main shaft bracket actually consists of two parts. (this is also a relief compared to the six parts in the previous design). In addition to the screws, these two parts are connected to each other by two aluminum profiles on the side of the bracket. In addition, these profiles extend into the holder on the base of WinDIY. There, this can be connected again with a long screw with the aluminum profile in the base.
The pictures below show the mount from different sides. To give you a better orientation here a picture of the mounted main shaft mount in WinDIY: (Note: The improved mount for the alumnium profile in the base of WinDIY is missing on the picture)
06/19/2020 at 15:06 •
Here is just a small update about the actual state of WinDIY
On the pictures you can see the ball bearing that i plan to use for the turret. (Banana for scale) It is actually a radial ball bearing and is therefore only suitable to a limited extent for absorbing axial forces. Since the ball bearing is mercilessly overdimensioned (compared to the low weight of WinDIY), this should work without problems. :)
In addition to that, I have completely revised the mount of the main axis. I will go into this in an extra log entry.
Short story: I think that the old storage would not have lasted long. In the newly designed version, the main axis is held by two radial ball bearings. I call this technique (which is certainly not new) "Aluminum profile reinforced 3D print". :D Please also see the pictures in case of upcomming curiosity. :)
That being said: The past few days I've been thinking more and more about the wind vane for WinDIY. This is the last big and important part of the wind turbine that I haven't worked on yet. A first (rough) sketch of the structure and a photo of the STL file for the first draft can be seen in the photos.
Little cliffhanger: I stopped printing the first draft after half an hour. More on this also in another log entry. :)
With all of these parts, I largely assembled WinDIY for the first time last weekend. I think now you can slowly see how it should look. :)
New main shaft design:
Rough look including wind vane:
06/19/2020 at 14:16 •
As you may have noticed, I am also trying to equip WinDIY with a few (in my opinion) important security systems. I planned a mechanical brake and the possibility to adjust the angel of attack on the wings.
In addition, I would always want to keep the generator in a certain load state via an artificial load.
Because what naturally always brakes a wind turbine is the load on the connected generator. You already know this from a small bike generator: as soon as the bike light is switched on, you have to push the pedal harder. What you can also notice (admittedly with a little sensitivity in the legs) is that the resistance of the dynamo increases with higher speed.
The principle is also clear for the wind turbine: the more load connected to it, the more the wind has to exert itself to accelerate the turbine. To a certain extent, when the wind is constant, you can also regulate the speed by regulating the load.
This means that by controlling the energy drawn from the generator, you can also control the braking effect on the wind turbine and thus protect it from excessive speeds. But what to do if the load connected to the wind turbine is not large enough?
If, for example, a connected battery is already fully charged, there is no way to load the generator of the wind turbine. There is simply no way to get rid of the produced energy.
In this case, the load on the generator would decrease, which in turn would reduce the braking effect. If strong winds occur now, this can lead to dangerous speeds of the wind turbine.
In order to have a "reserve load" available in this case, I planned to mount load resistors on a heat sink and attach them to the boom of the wind turbine. This additional load can easily be switched on if required. The heat generated can then be released into the ambient air via the connected heat sink.
Here a photo of the heat sink and the resistors i received and plan to integrate soon into winDIY.
06/14/2020 at 12:34 •
The WinDIY hub is literally at the forefront. In addition to the many forces that it has to endure, it also includes mechanics that are quite important for the function of WinDIY.
In addition, most of the mechanical parts come from the 3D printer and (of course depending on the material) are sensitive to weather influences such as UV light.
To protect the mechanics and the general structures of WinDIY at least somewhat from the weather, it is of course also provided with a hood. After assembling the hub, this is simply attached from the outside with three screws. :)