I have access to a CNC waterjet via The Foundery, a community makerspace in Baltimore MD, so I thought it'd be awesome to design some kind of go-cart that uses the waterjet to cut all the parts from a single sheet of 16 gage steel. I used the waterjet to cut perforation lines in the steel so that the whole frame could be folded up to create the chassis like a pizza box using just a couple adjustable wrenches.

Parts List with costs:

4'x8' 16 gauge steel sheet ($60) King's Architectural Metals
Rear Axle kit ($284) http://www.bmikarts.com/Drift-Trike-Axle-Kit-with...
Head Tube Bearing Kit ($13) https://www.amazon.com/gp/product/B003J7XCRO/ref=...
Front Fork ($50) https://www.amazon.com/gp/product/B00J3VSDQA/ref=...
Twist Throttle ($33) https://www.amazon.com/gp/product/B0062PNBTE/ref=...
26" x 4" front mountain bike wheel
Front Hangle Bar ($20) https://www.amazon.com/gp/product/B00M9MGY6G/ref=...
Handlebar stem ($8) https://www.amazon.com/gp/product/B017YRH88S/ref=...
Hydraulic Brake Kit ($35) https://www.amazon.com/gp/product/B01MQO6LDL/ref=...
6.5 hp engine ($119) https://www.harborfreight.com/65-hp-212cc-ohv-hor...

Step 1: Drink Some Coffee and Put on Some Music

It's like Thomas Edison once said "anything worth doing, starts with caffeine and Beastie Boys". As much as I love the Beasties, there are a few music options that are close in work performance facilitating, which include but are not limited to:

Dropkick Murphy's
The Dirty Heads
Sublime
Flogging Molly
Ted Nugent's "Stranglehold" (the only song worth listening to by Mr. Nugent...but it's super long and will almost get you through this entire build.

*Thomas Edison may or may not have been the originator of that quote...it may have actually just come from myself.

Step 2: Cut Out the 4 Frame Components

OK, this is it! This is the most important section of this instructable. All my hours spent designing this trike frame, free for anyone to build their own!

Using either a CNC plasma cutter, waterjet or laser; cut each of these 4 parts out of the steel sheet. You could break these up and cut all the parts from two 4'x4' sheets of 16 gage steel.

Once you cut them out, clean all the parts with acetone or alcohol. DO NOT clean the parts with brake cleaner! In case you did not know, welding steel parts that have been cleaned in brake cleaner or any thing chlorinated creates a phosgene gas (a very toxic gas) that can kill you at very low levels of exposure! You're welcome ;)

Step 3: Bend Up the Frame Parts!

Bend up the frame components as shown. Be careful to bend them in the correct direction, if you bend them wrong and bend them back you'll most likely fatigue the parts and split the seam.

Step 4: Assemble and Weld the Trike Frame Components

Now you're getting to the fun parts! The parts should fit together like the birds and bees!...I think that's how that analogy works ;)

The two largest parts fit together to create the main chassis while the smaller parts form the neck. Once the two sub-assemblies are welded the neck tube can be welded upright. make sure the base of the neck tube is flush and parallel with the chassis' bottom surface.

When welding, you can stitch weld 1" on, 1" off to create more than enough shear strength to hold everything together. I used a millermatic 211 MIG welder set to voltage level 4 and a wire feed of 40. Wear a respirator even if you're welding in a well ventilated area. Don't take any health risks.

Step 5: Weld on the Head Tube

I turned my head tube from a piece of 1.5" round tubing to create the right inside diameter from my neck bearing kit. You can buy 8" neck tubes already for welding on to your frame from a local bike shop for online stores that sell parts for building your own bicycles.

Step 6: Paint Your Frame

The Foundery has a powder coating station, so I'm spoiled. Spray painting the frame will be just as good. Take your time here, because after assembly things will be very difficult to touch up.

Step 7: Assemble the Trike!

Assembling the trike was my favorite part of the build. My son, Aidan, helped me assemble it and it was awesome. Things went together pretty smooth. Here's the order at witch i assembled it:

Front fork and wheel
Front brakes
Rear axle
Engine and centrifugal clutch
Rear wheels/tires
Handle bars
Twist Throttle

Step 8: Take It for a Spin!

OK, I lied...and I feel bad about that. Taking the trike for it's first ride was definitely my favorite part of this project. This thing had me grinning from ear-to-ear. It's just a blast to ride!

I hope you enjoyed this Instructable! Let me know if you have any questions.

-Corey