Intro: Mobile Bicycle Powered Air Compressor
This eye catching addition to any bicycle allows the user to continuously compress air while riding. The power from the bike wheel is converted into air pressure by using an off-the-shelf car tire compressor and a fun amount of 3D printing and Laser Cutting. You ask, "Well dude, why would I want to compress air while I'm riding my bike?"
Here you go-
Applications of Having Compressed Air on a Bike:
-Storage in a tank for use inflating bike tires
-Running some sort of electric turbine(very inefficiently)
-Powering a misting system to keep you cool
-Pumping up a water gun
-Inflating party balloons while you ride your bike to a birthday party
-Running an air brush so that you can simultaneously paint and ride
The list goes on and on.
The project was completed in the University of Texas Maker Studio using the Makerbot 3D printers and the Full Spectrum Professional Laser Cutter.
Step 1: Air Compressor
This air compressor model and other similar ones can be purchased cheaply online. I ordered mine from Amazon for $15. The compressor comes out of the box with a plastic shroud, which you should remove. Once inside, the electric motor needs to be removed. A few simple screws and you should be down to the bare minimum air compressor; just a mechanical piston driven by a nylon gear(which used to be connected to the motor shaft)
Notice how the device was mounted on the inside of the shroud, because this will help you later when designing the new mount.
Step 2: Designing and Printing the Mechanism
There are many ways to design this section of the unit. I constructed the design by 3D printing a few parts designed in SolidWorks.
To connect the flywheel to the gear face I designed a small part that screws onto the gear face. I figured that this would be more reliable than trying to build a gear to mate to the existing one, and since I was impatient and cheap, I didn't want to order gears online. This solution ended up working out quite nicely. This part extends through the ball bearing and to the flywheel.
In order to connect the mounting brackets to the seat post we also need to print two pieces that can join those.
The flywheel was constructed with a combination of laser cut and 3D printed parts. If you don't have access to a laser cutter, you could definitely complete this with any other circular object such as the bottom of a bucket or a coffee tin lid. Basically the flywheel has to be both of a reasonable diameter for the area that you're working with behind the bike seat, and sturdy enough to undergo the damage of road wear. I used two laser cut circles(made from 1/4'' acrylic and connected them with 3D printed spacers. The flywheel was connected to the assembly with a 3D printed faceplate, but this could be easily done with the right hardware.
Step 3: Laser Cutting the Flywheel and Mounting Bracket
I used a Full Spectrum 20x12 Professional laser for this project. The same result can be accomplished with most other lasers. Cutting acrylic does produce harmful fumes so make sure that your filter device is operating when you do this.
I designed the laser cut pieces in a program called Inkscape. This is a design program that draws lines in vectors. This data type allows the laser cutters to follow the path of your designs instead of just the image, which is necessary for laser cutting. Inkscape can be downloaded at https://inkscape.org/en/download/
The flywheel was an 8" diameter circle cut from 1/4" clear acrylic sheet as detailed in the previous step.
The mounting bracket is made from the same material. The bracket connects to the seat post. It extends out over the tire and gives the mechanism clearance to pivot. The rest of the mechanism pivots around a screw that stretches between the two acrylic sheets.
Step 4: Main Assembly
The whole thing was assembled using off the shelf hardware, mainly small nuts and bolts.
Assembly happens as follows:
1) The bearing is inserted into the throw arm and over the shaft of the gear face mount
2) The the long 1/4" bolt is inserted into the center of the assembly
3) The flywheel mating face is fit over the 1/4" bolt
4) The flywheel(assembled) is inserted on the same bolt
5) A lock washer and nut tighten the whole thing down(I found that lock washers were good to use with the acrylic as they sort of sink into the material)
6) The compressor mechanism is first bolted into place on the throw arm
7) The face of the compressor's gear is then connected to the gear face shaft with a few teenie weenie bolts
After all of the pieces were assembled the next thing to do was to mount it.
8) Run some 1/4" bolts through the mounting brackets and 3D printed post mount and secure.
I decided to have some fun with a Dremel cutting tool and cut down all of the protruding bolts so that the whole thing would be safer. Its also fun to make sparks cutting metal sometimes.
Step 5: Brake System Assembly
The whole mechanism moves up and down about the pin at the ends of the brackets. This is achieved with a spring and a cheap brake lever that I bought at a local bike shop, Clown Dog Bikes. The guys at the shop sold me a used handle and cut me the wire and housing that I needed. This helped me out a ton.
1) To make the whole thing springey, I put a bolt through from the mounting brackets to the throw arm. Then I put a little spring over that bolt. This makes it so the device returns to its home after each pull of the lever.
1) The handle/lever is mounted on my handlebar in a position that wouldn't get in the way of the brakes.
2) The wire is fed through the housing
3) The housing is brought back to the mounting bracket where it is mounted with a small 3D printed part(orange in the pictures)
4) The wire needs to be connected to the mechanism. I used an electrical terminal clip to connect the wire to the unit. A bolt needs to be placed in the back of the mechanism where the wire runs past. The little electrical clip then fits right onto that bolt and can be tightened down with a nut. This was a surprisingly secure and easy way to connect my bike wire.
5) The excess wire coming out the bottom is snipped off
Step 6: Add Tubing
I purchased some pressure tubing from a local hardware store that had the same inside diameter as the compressor output. I clipped off compressor nozzle head and then connected the tubes together with a little nylon fitting. Before inserting the fittings I heated up the tubes with a heat gun.
Now the compressor is connected to a longer hose that can reach anywhere on the bike, from the back to pump up a tank all the way to the front to fill up a handlebar mounted water gun:)
Step 7: Have Fun
Take your new air compressing bike for a spin!