Theoretically a belt drive system should be a good way to power a pedal blender.
This project is my third pedal blender. I combines three basic design points:
-The drive system uses a large surface area maximize power transmission.
-Almost everything is recycled/reclaimed material thus reducing the cost to about $0.
-The business end is a food processor NOT a blender. See the next step for an explanation.
***Update*** My engineering prof. just told me today never to design anything with a three dimensional belt system like this. I told him "Too late". Ha!
Here's a video of the first blender table I made.
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Step 1: Materials
You will need:
2 dead bicycles. One with a functional drive system. We will only take the front hub and forks from the second bike.
2 front wheel hubs from a bicycle.
1 inner tube.
1 rat trap or other rear rack thingy for a bicycle.
6 tire patches (real ones, not the crappy glueless kind) and a patch kit.
1 food processor.
1 wide skateboard wheel or similar wide roller.
wood (or a table)
wood screws (long and short)
Bike Orgy image from http://www.flickr.com/photos/clickykbd/33589383/
Step 2: Practical Design Philosophy
This topic covers the reasons why I wanted to use a food processor instead of a blender and a belt drive rather than a skateboard wheel or similar friction device pressed against the side of the bike wheel.
Why a food processor and not a blender? Well a review of basic physics will show us that longer blades will have greater velocity than shorter blades at any given RPM. Everybody gets confused whenever I try to explain this . Sorry...
Physics: But wouldn't short blades spin more easily? Yes BUT: In this case the maximum RPM is dictated by the bicycle and the person pedaling and not the length of the blades. Unfortunately, the RPM of bicycles is almost insufficient to run a blender properly. This means you pedal as fast as your legs will go but the short blender blades move too slowly to puree an orange. The solution: use a food processor; it has longer blades so they move faster than a blender.
Jamming:Also many blenders are not round cylinders but rather rounded squares. So when your human legs pedal a margarita the result is an ice jam. Again a food processor to the rescue. The food processor's smooth, circular walls never jam.
Why a belt drive? When I first made one of these, the thing would always slip when over-strained or when the frame twisted a bit due to pedaling. The friction wheel always needed to press hard up against the bike wheel and in my case this required lots of complex over-engineering.
What seems like a much better solution is to use a belt that touches most of the rim. This is much less prone to slipping.
Step 3: The Belt
About it: The belt-drive system uses a round belt. You might be able to use another type of belt but this rope-like belt works and is cheap.
The belt is round because it must travel around curves in three dimensions. A flat belt doesn't like to bend sideways whereas a round belt doesn't care which way it bends. (Note: I have seen flat belts used in a twisted application on an antique drill press in Austria)
Make rope: My dad taught me to make rope the way he used to do it as a child in rural, post-war Japan.
-Cut a bicycle inner tube into three strips lengthwise.
-Twist the strips so they change from flat strips to tubular coils. Twist each strand separately but in a consistent direction.
-Twist two of the strand together in the opposite direction.
-Finally twist the third strand in with the first two.
There is something called a rope making machine but this rope is so short you can make it by hand easily.
It probably is better to make the rope-belt as smooth and even as possible. This should help the mixer run smoother.
Step 4: Make a Loop
Make a loop by using a Long Splice to join the two ends of your rope.
These people are better at explaining how to long splice than I am.
Abut the Strands
This may be unnecessary but I used a tire patch on each side of each strand as a bridge to join each strand to it's abutting strand. This helps keep each strand from unraveling out of the rope-belt.
Step 5: Final Thoughts and Backstory
This pedal powered food processor was motivated by two things.
First, I offered to try and make one for my friend who lives on solar power. Due to the constraints of her particular system can only use her food processor when the sun shines. Drag! I figured she would be the most likely person to make real use of a pedal powered appliance like this.
Second, the Mud Girls gave an inspiring presentation about their method of trading labor for skills. Inspired, I invited all present at this meeting to learn how to make a blender bike. After all, seeing as I already planned on making the thing it would be great to have more people on board with their own skills to contribute. It's like a skillshare potluck.
Each time I make one of these I try something new so it ends up taking a long time to solve problems. That said I learned a lot this time so it was well worth the time.