This Instructable will explain how I've built my own pedicab, as well as provide guidance for others who want to build a better one. Total cost was ~$300 + my own labor, and this is close to the equivalent of a model commercially available for $1995.

I currently use my pedicab in Austin, Texas. As of 9/8/08, it's fully licensed by the city of Austin. Woohoo!

Before we get started, let's define pedicab:
-Check out the Wikipedia articlefor an overview
-Look at Pedaltek's tow-behindfor a good example of the trailer type I built
-Read the comments on my Make posts describing the experience so far (hereas well as here) to hear engineering concerns commenters more intelligent than I have raised

Step 1: Plan and Experience

I learned from experience that this project is a bit too large to tackle without planning. So, start by sorting out exactly what you want to build. Be sure and ask yourself these and other questions:
-What requirements (insurance, permit, etc.) does your local government impose for pedicab companies?
-What's the terrain like in the area you'd like to serve? If there's a mega-hill separating the only 2 popular bars in town, that could be a problem...
-What should you learn before undertaking a project of this size? How much easier would welding skills, etc. make your project?
-Do you have the time and energy to invest in building this?
-Are you confident enough in your abilities at making things to strap unsuspecting bystanders onto your creation before darting into traffic?

And, it's a very good idea to consider gaining some riding experience for another pedicab service before endeavoring to create your own. This isn't like normal biking, no matter how quick you might be on your chosen style of cycle...

Step 2: Design, Plan, and Then Keep Designing and Planning

After you've decided on the style of pedicab you'd like and the general building style, get to work creating a model. Here's a fly-around of an earlier version of my pedicab, sans wheels:

You can download the SketchUp model here.

Key considerations to think about:
-Weight distribution, in front of and behind the wheels
-Strength of tongue (connection between pedicab and bike)
-Passenger comfort
-Aesthetics
-Most importantly: stopping ability!

Again, it really helps to ride for another service or otherwise establish an intimate familiarity with existing pedicab designs before jumping into this.

Step 3: Make Mistakes, and Learn From Them

Now, I didn't create the model in the last step right away. In fact, it was a matter of several drafts before I took modeling beyond pen and paper. I won't say this is the only way to do it, but really getting my hands on and making (low-cost, often reversible) mistakes was what worked for me.

Check out the pictures and comments to learn from my design flaws...

Step 4: My Specifics: the Parts

Now, I'll dive into specifics of my design. Again, not the only way to build a pedicab and not the best. But, I am pretty happy with the results:)

Here's what I used to make this monstrosity:
-50-some feet Telespar (perforated galvanized steel tubing). You can read about its structural properties here.
-~12 feet 1.75" Telespar, to reinforce the Telespar between the pedicab and the bike
-60-odd bolts, mostly grade 5. ~45 of length 5", 5 @ 2.5", and ~10 at 7". Diameter 3/8", except for 2 9/16" grade 8 bolts used on connection to pedicab
-60-odd locknuts, same diameters as bolts
-~150 flat washers, 3/8"
-3/4" plywood
-bright orange paint
-bright green duct tape
-bright blue pool wacky foam float things
-zip ties, for securing pool things
-female rod end, for pivot point between bike and trailer. I used this one(if link doesn't work, type in 'tf7' to load the product info page)
-high-visibility red blink lights
-screws, staples (size unimportant; use washers with screws to prevent from screwing through hole)
-outdoor fabric, a couple yards
-mildew-resistant stuffing, 2" thickness, couple yards
-spray paint, old molding (kind you'd put along a floor), and stencil (to create dirtnail sign)
-overly-priced non-slip tape (city regulation, for the floor)
-slow-moving vehicle sign (ditto)

And, I suppose wheels are helpful:) If you don't have bureaucracy to navigate in your metropolis, scavenge some strong wheels from a BMX bike. After getting shot down trying to get Craigslist wheels to pass inspection, I found the bike shop at which another local pedicab company buys wheels and ordered the same ones. At ~$130, the wheels were the most expensive part of this project.

I sourced the Telespar from a local safety sign company for ~$1/foot, and everything else is available between hardware stores, megamarts, and fabric shops.

Step 5: My Specifics: the Tools

The main tools I needed for this project were:
-Various metal grinding wheels. The most useful was the 10" one that worked with my cut-off saw. Careful with the sparks!
-A mask and an outdoor work environment. Breathing vaporized zinc, a product of cutting or welding galvanized steel, is a really bad idea. After reading this account, I particularly realize I should have worn a real tiny-particulate-filtering mask.
-Various vice grips and wrenches, mainly 3/8" and 9/16"
-drill with various bits, sized from below diameter of smallest screw to slightly larger than diameter of 3/8" bolt head

Step 6: My Specifics: Making the Structure

This style of building is called grid beam; you can learn more about it here.

Instead of welding, I basically just had to cut my Telespar to desired sizes and then use 2-3 bolts (with locknuts and washers) per intersection to create stable joints. To make this process doable, don't tighten any of the nuts until you've got all the bolts and nuts of an intersection inserted.

For sizes, open the Sketchup model from step 2. Note that this version allowed an unacceptable amount of bending between the cab and the bike, so I revised this tongue in the final version.

Step 7: My Specifics: Notes on Tongue Design

The area of the pedicab in front of the footrest gets a LOT of force applied to it: it's the end of a lever with your passengers at the other end.

My first designs bent so much that one actually bottomed out when I tried to brake, which would not have made for a very customer-friendly experience or me-friendly tip.

So, to arrive at the final product pictured, I found a couple of books on car trailer design (specifically, volumes 1 & 2 of M. M. Smith's "Trailers: How To Design & Build"). You can also check out what trailer hitches look like or just reason through some of the key points:
-load is spread between multiple attachment points to trailer
-tubing that bears the full weight of the pedicab is reinforced
-multiple grade 5 bolts secure each part of the tongue

Experiment with design on this part, and let me know what you come up with!

Step 8: My Specifics: Attachment to Bike

My system of attaching the trailer to the bike basically relies on the female rod end to pull the full trailer's load via its attachment to my bike. There are definitely many other ways to do this; I want to adapt this to include redundant attachment between bike and trailer for a future version (ie 2 bolts instead of 1)...

Step 9: My Specifics: Aesthetics

Love or hate the look I've arrived at, here are the basics of how I achieved it:
-3/4" plywood painted with exterior latex paint is more than strong enough for the floor, seat, and back surfaces
-outdoor fabric is stapled to the board on one side, stuffed with 2" thick mildew-resistant foam, and then stapled to the other 3 sides. pull the fabric taut around the foam to give this a nice overstuffed look
-zip ties with bits of pool foam covered the ends of the metal well enough for the city of austin's standards
-green neon duct tape makes the design louder and covers the edges of the plywood