A recumbent bike with a very comfy seat.
It's a 35 pound leather executive office chair connected to a 16" (little girl's) Princess bike re-welded into a recumbent (recliner bike) and using a piece of another donor bike frame.
I built it in honor of "Bike to Work Day".

If you like fun/unusual home built bikes... check out my hobby site Woodenbikes.com

Step 1: Design Your Bike Using a CAD System (Cardboard Aided Design)

Make a cardboard cutout of your lower leg (with foot and pedal), thigh, torso, and straight arm (to a distance 2" back from your wrist). Use it to look for good riding position and clearances for knees to bars, heels to wheels etc. Use the CAD system to layout the riding position, cranks, wheels etc with attention for locating your hands, shoulder, seatback angle, butt, knees and feet. Also look for ways to arrange a straight chain line (at least for the tight side) by raising the Bottom Bracket (BB)(main crank bearing).
For detailed instruction on designing a sweet handling recumbent visit www.bikesmithdesign.com

Step 2: Cut and Miter the Bike Tubes for Joints

Use a hole saw (toothed cylindrical drill bit) to simultaneously cut and miter the donor bike's former downtube to become a boom tube out to the Donor bike's BB. Carefully eyeball the angle but always wear eye protection when eyeballing.

Step 3: Clamp or Strap Tubes Together for Welding

During and after filing the donor tube's mitered end, the joint is assembled and checked for correct angle, centeredness (meditation could help here) and plumbness (allignment by eyeball). When it all looks straightish, it is clamped or straped together to be tack welded.

Tack welds are small to avoid melting too much of the nylon strap.

Step 4: Weld It Together

I use a little 110 volt MIG* welder. It is the red box. The weld is finished in this picture.

*MIG = Metal, Inert Gas sheilded welding. however I use a cheaper flux cored feed wire instead of gas sheilding. It helps keep my weld quality low so I won't obsess as much.

Step 5: Reinforce the Seatpost

It looks so much more business-like after painting over the "Little Princess" motif.
I added internal steel tubing reinforcement to strengthen the seat post since I weigh more than most little princesses and the office chair lets me put lots of leverage (bending moment) on the seat post.

I split the office chair's own seat post and inserted the bike's reinfored post into the chair's seat post. I welded the split back together.

Step 6: Install Chain Roller

After assembling enough chain in the length needed, hold a jockey wheel from a derailuer up to the frame with the chain on the jokey to see where you can position the jockey to take up slack and lift the chain over the front wheel. Mark that spot and drill a hole for a hardened bolt that will act as an axel for the jockey wheel to spin on. Assemble and lubricate jockey wheel and bolt passing through hole in frame boom. Use a large washer or a n orange juice can lid to guide chain and prevent it from falling off jockey wheel. I added an instructable all about using a chain tool to make long chain : https://www.instructables.com/id/EQWN3LZF4NIBB0H/

Step 7: Reposition the Chair

I had to reposition the chair lower and further forward so my toes could reach the ground.
The plywood board has holes for mounting to the chair and to the chair post platform.
The old brake cable wire in front is holding the front of the chair down and to keep it from rotating around the seat post since there is a lot of twisting leverage from the wide butt in the wide chair.

Step 8: Riding the Office Chair (AKA Loose Nut Behind the Handle Bars)

Here it is on its maiden voyage. I still need to lower the seat further so my feet can securely reach the ground given the chair's long seat pan extending forward under rider's knees and holding them up.

That little tail sticking out in back is a side view of a 3 foot long 1x10 wooden board between the chair and chair mounting bracket on the seat post. It allowed the chair to be offset from the post about 5 inches forward leaving a back shelf for storage.

Woodenbikes.com disclaimer: None of my 15 home built bikes (to date) are made from 100% wood. Wood is not my religion. Wood is a conveneint and entertaining construction material for some parts of my bikes. Your Apple computer may not be made of 100% apples either. Open it up if you don't believe me.

Step 9: Where Do We Get the Supplies?

"Sustainable shopping" is my new hobby.
Dumpster Dipping (no diving allowed, you could hurt yourself) is the way to go.
Sometimes I feel like "Dumpstermiah Johnson" while I'm "trolling the suburban trap-line". That's where I found the 35 pound leather executive chair, and the Princess bike, donor bike and paint and extra bike chains joined together to reach everything.