Introduction: How to Create a Smoothie Making Human Powered Bike Blender for Less Than $25

About: I'm a mechanical engineering student at the University of Minnesota. Sometimes I climb trees. Sometimes I study. Tree climbing is more fun.

I love biking. I also love smoothies. That's why I was really excited when I read about the B3 mini from rock the bike in Make 11. However, upon visiting their site I was dismayed at the cost of the blender, about $250. Thus, not knowing if it would work, or if it was even legal (patent infringement and such) I set of to create my own bike blender.
This instructable documents how to create your own inexpensive, energy conserving, bike powered blender. Since appliances account for over 20% of your electric bill, this is one less energy consuming machine in your house. And making a fruit smoothie is twice as good for you as before; both in nutritional value, and also in the exercise you get. It isn't an incredibly difficult build, and even the most inexperienced Maker should be able to complete it in less than 3 hours (not counting glue drying time).

Step 1: Necessary Materials

Materials needed:

Blender: Theoretically, any blender would do. I'm using a Hamilton Beach personal blender that was practically made for this project. The two key things needed are that:

1) The blender jar locks in place
2) There is a transmission disk, instead of the motor connecting directly to the blades

A M4-.70, 19cm long bolt: In a perfect world, a bolt of this size would exist, but the longest I could find was a 7 cm. If you can find one, great, otherwise you need: 3- 7 cm, M4-.70 bolts and 2 coupling nuts of the same size.

Old bicycle inner tube

1x8 board

3x4 metal plate

2- 1.5 in. diameter wooden wheels

4- 2 inch bolts of any size, and 4 matching nuts

2- 1 inch wood screws

2- M4-.70 Tee nuts

Bicycle rear rack: any rack should do.

Step 2: Tools Needed

Tools needed:

Wood saw

Hack saw and table top vise (only if you need to make the 19cm bolt)

wood glue

Drill and drill bits

Tape measure




medium clamp


2 1/4 inch hole saw

Step 3: Void Blender Warranty

Once you have your blender, the first step is to remove all the useless, power-draining junk.
For the blender I used, the process went like this:

Remove bottom plate, cut the power cord, then remove the second bottom. Now you should have full access to all the guts. By gripping the motor with a pliers and holding on to the transmission wheel with your other hand you should be able to unscrew the motor from the wheel.

Throw out (or better, save for a later project) the motor , two bottom plates, and power cords. All you need is the base, the transmission wheel, and the little black rubber piece in the hole.

Step 4: Make Inner Wooden Supports

Using the hole saw, cut 3-2 1/4 inch rings out of the 1x8 board. Glue them together in a stack using wood glue, clamp, and allow to dry.

Once dry, use the saw and file to cut 2 notches on opposite sides of the cylinder. These notches will allow the cylinder to fit between the two columns in he base for the original screws.

Step 5: If Necessary, Construct the Long Bolt

I couldn't find a at least 19 cm, M4-.70 bolt. If you were lucky, or just more skilled than myself, you can skip this step. For the rest of you, this piece must be constructed.

First, cut the heads off 2 of the 7cm bolts using the hack saw and vise. If you don't know how to do this, there's a good tutorial here: quick bolt shortening tutorial.

Then cut a 4 cm piece out of the 3rd bolt. Thread all the pieces together using the coupling nuts, with the order long, short, long.

Step 6: Construct the Base

Cut a 8 inch piece off the 1x8. This will form the base of the blender. Next, drill a hole wide enough for the long bolt to fit through about three inches from the shorter side (the cut edge), and centered between the two longer sides (the 8 inch edges).

Line up the hole in the cylinder left from the hole saw with the hole in the base and screw it into position with the two screws. Now you have finished the base assembly.

Step 7: Attach Blender

Slide the blender bottom over the cylinder on the base assembly, making sure that the grooves line up.

Then insert the long bolt through the hole in the base and out through the top of the blender bottom.

Screw the transmission wheel on the long bolt.

Step 8: Attach Friction Wheel.

Using the hammer, pound the 2 tee nuts into the 2 1.5 in wheels. Then thread them onto the long bolt.
It is important to thread them so that the tee nuts are on the outside, not in between the 2 wheels. Otherwise the wheels could fall of, even though the nuts stayed in place.

Next cut a 1inch piece of the old bike inner tube. Slip this over the wheel assembly.

Now you have finished the bike blender. All that is left is to install it.

Step 9: Fit the Blender to the Rack

Set the blender assembly on your bike rack so that the friction wheel sits on the left side of the tire. If you put it on the right side, the blender will spin counter-clockwise and unscrew itself.

Now you need to adjust the friction wheel so that it sits on the back tire correctly. Optimally, both 1.5" wheels should be touching the tire at all times (see photo).

Step 10: Attach Metal Plate

This step is best accomplished with the bike upside down. Once the bike is flipped, align the blender assembly in the same position you had it in step 9.

Then place the metal plate on the bottom of the bike rack. Make 4 marks where the corner holes line up with the wooden base.

Drill out these holes so that they fit the 4 bolts you have.

Then, with the bike still upside down, push the bolts through the plate, through the bike rack, and out through the wooden base. Lightly twist on the nuts so that the base can still be adjusted.

Then flip the bike back over.

Adjust the base of the blender so that the friction wheel sits against the back tire, and then tighten down the remaining nuts.

Step 11: Use It

This blender can be used for anything you would use a normal blender for. Simply add the ingredients and bike. However, here are a few hints to optimize use:

1) Use a bike trainer so that you don't have to go around the block to make a smoothie. New ones from the store can be expensive, but you can find several on Craigslist or Ebay. You'd be surprised how many people bought them to exercise, but never used them.

2) For really hard things such as ice, it is best to start moving before adding the ice, otherwise the blender just jams. Again, this works best with a trainer.

3) Check the parts regularly for wear and tear, especially the rubber ring. A blender breaking can ruin a good smoothie.

Also, here are good Smoothie recipes.

Step 12: Future Additions.

For this blender to truly be mobile, the ingredients need to become mobile to. But on a hot summer day, when I really want a smoothie, the ingredients can go bad pretty quickly. At the moment, all I have is an inefficient, heavy ice cooler. As the ice melts, it fills with water and sloshes around. Here are my brainstormed solutions to the problem, please comment and offer suggestions, as ideas are needed.

1) Replace the ice with gel based ice packs to remove the weight.

2) Attempt to build a mini-refrigerator for the back of my bike, but this will be difficult.

3) Use a highly endothermic reaction to cool the ingredients. A possibility is the reaction between Ammonium nitrate and water. Ammonium nitrate is a common fertilizer. The heat of solution of this reaction is -25.69 kJ per mol, easily enough to cool the ingredients while blending, or in some sort of cooler.

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