Unfortunately I did not take pictures of the process of building my wheelbarrow bass, but I will try to describe the process as best I can by focusing on each part of the instrument, and including rough diagrams. I did as best as I could to describe what I did, but it has been awhile since I finished this project so I'm probably glossing over a great deal...
**I must admit the idea to use a wheelbarrow is not completely original, as I have seen at least one video of an upright made from a wheelbarrow online...but oh well here is my take on the concept!
Step 1: An Overview...
For the tuning pegs, I just used standard Fender electric bass tuners. The strings are actual upright bass strings, but they were super cheap (I ordered a couple sets from China for about $20 a set). As an alternative, you can use weed whacker line for the strings, as it comes in the correct gauges as bass strings! The weed whacker line gives the bass a nice "gut" tone.
I used a heavy application of black stain for all the wooden parts but I used lighter stain for the fretboard and bridge, and for the body I used black spray paint.
For some perspective on its size, I included a picture of me playing it, and the upright next to a standard size electric bass. Also pictured is a diagram (not to scale) showing some of the approximate dimensions of the bass.
Step 2: The Body...
I used the wooden handle that came with the wheelbarrow as a support to attach the neck pieces to. The wooden handle is screwed in at the bottom of the wheelbarrow, and it comes up through the top of the wheelbarrow through a rectangular hole I cut. You can just barely see the wooden handle support through the soundhole.
After doing a little (emphasize little) research on the parts of an upright bass, I made a bass bar and a sound post. The bass bar is attached to the underside of the face, roughly going along below the E string. It is about a 2 ft strip of wood 3/4" wide, tapered so it that goes from about 1/2" high on either side to about 1 1/2" in the middle. I used a wood rasp to round the top of the bass bar. The sound post is a 1/2" wooden dowel that runs from the underside of the face near G string to the back of the wheelbarrow.
The face was attached to the body using screws. I drilled holes in the face and through the lip of the wheelbarrow. After the face was screwed on, I cut the screws down to size and used rounded plastic screw covers to cover them up.
Step 3: The Neck...
I glued the left and right neck pieces to the sides of the exposed wooden handle coming out of the top of the wheelbarrow. Then I glued the middle pieces in between. I also glued a wooden block to the face and glued the neck pieces to that for further support. The diagram "Attaching the Neck" shows how I affixed the neck pieces.
After the neck pieces were glued together and attached to the body, I glued two small round wooden pieces to either side of the headstock. I used a load of wood putty to smooth over the seams in the neck pieces and where the neck was attached to the body.
Additionally, at this point the fretboard was glued to the neck. The fretboard is a piece of maple that I spent many hours rounding the edges and sanding smooth.
Step 4: The Headstock...
I harvested the tuners from my electric bass.
Step 5: Finishing up...Bridges, Strings, and Foot!
The bridge was cut out of maple. In order to attach the strings, I drilled holes into the lip of the wheelbarrow at the bottom, and I cut grooves in the wooden face. The nut is a simple small piece of wood with grooves for the strings to rest in. As I mentioned earlier, I was able to get decent upright bass strings online for very cheap (they can run in the $100s!), but weed whacker line would work as well.
For the foot, I was lucky enough to be working at a machine shop that summer so I was able to secure a small metal block with a threaded hole in it, and a large screw that fit the hole. Before I had attached the face, I glued the metal block into the bottom of the bass, and cut an appropriate sized hole so that the foot could be screwed in. I put a tennis ball on the bottom of the "foot" screw so that it would not destroy my floor!
I included some pictures here of the upright bass (affectionately called "Black Betty") in action! So thats about it. I apologize if this is not all inclusive, but if anybody is willing to try something similar contact me and I will try to provide more details! Thanks for checking it out :-)