Tubular Bass

Making a bass out of a length of exhaust pipe is tricky to imagine in detail. The compromise between fboard radius and a tube that I could hold and potentially reach the strings was a bit of inspired guesswork. I eventually settled on a 1.2m length of 50mm diameter stainless steel pipe to be the basis of this creation. It has a 1.5mm wall thickness and weighs around 4kg. 

To get an idea of how it would perform under stress (probably much better than I do 😮), a piece of 25mm x 50mm (1mm thick) 1m steel box section was tried. A couple of strings were fastened to it and it was tuned up. Under tension, the box section did not bend or warp any measurable amount, so the stainless tube is expected to shrug off the string tension easily without even breaking a sweat. 

Incorporating the tuners was the next hurdle. The tuners have to be fitted on the outside of the tube so they can be adjusted. That implies that the strings will need to be inside at that point to wrap around the peg part of the tuners. A cutout will be required for the strings to pass through, with enough finger space to allow strings to be changed. Fellow band-mates will tell you that I only change strings once every 20 years, but they exaggerate. It's probably more like 17 or 18...

Creating an opening for the strings that can be made with an angle grinder is one thing, but working out how everything will fit was seriously testing my sketching and trigonometry skills. It was time to go down the 3D CAD route just to try and visualise the thing as a whole. After a bit of mouse-clicking I chose a package called FreeCAD which uses the make-a-2D-shape-and-extrude-it concept (amongst others). After running through a tutorial I was ready to do some virtual work.

The headstock cutout developed into two matched cutouts allowing string access from above and below. The large holes are where the tuners will be fitted. I'm not modelling the tuners in 3D CAD! The tuners will need some sort of flat-curved washer system so that they can be clamped either side of the tube. 

A round aluminium disc will be mounted inside the tube by the tuner cutout. Another offset disc functioning as an adjustable nut is fastened to this and will stick out of the cutout by a few mm to support the strings. 

I then turned my attention to some dodgy 3D bridge scribbles I made earlier.  

The bridge also requires a cutout and inspiration came from the whistles in Steamboat Willie. The strings are not wrapped around anything at the bridge end, so it can be a smaller opening.

The bridge is also based on a set of aluminium discs. The bridge takes more string load than the nut so two static discs, followed by three other offset, er, shapes to create anchor points and a saddle area. 

What about the pickups?

The cutouts are mostly filled with aluminium and are physically positioned at the ends of the strings. Introducing a third cutout to house a pickup was considered, but would introduce an unnecessary weak point in the middle of the tube as well as making it look too conventional! Having a set of split P-bass pickups sitting in the middle of the tubular bass would give its purpose away too quickly.

A small piezo pickup designed to go under an acoustic saddle is going to be used to convert strings into signals. The piezo device is around 50mm x 1mm x 3mm and is unlikely to add anything significant to the weight of the instrument 😉.

Well, that's the theory. It remains to be seen how much of this is successful...

Goodwood or Good Wood

Last year I went to a Basschat event. We turn up at a school that's borrowed for the day and it gives a chance to exchange ideas and drool over exotica that is beyond normal means. It's much like going to a car show, where I need to see the orange Lamborghini and study it from different angles, talk about how VW is the sensible option and then buy some fluffy dice and go home.

During the 2019 Basschat meeting we had a great guest speaker (Pete Stroud) who took some time explaining why he made his own guitars, and the attention to detail that makes the difference between a good bass and a great one. He is a very unassuming and competent chap, and it was interesting to hear his reasoning for various design decisions. 

One thing that Pete was quite certain on was the influence of the wood on the sound. Although other parts like pickups also affect the sound, over the years he had noticed that whilst certain woods gave excellent tonal quality, others did not.

I have heard similar anecdotal evidence over the years and I believe that choice of wood definitely has an effect, but I'm not convinced it is the main factor to a solid body bass. Unfortunately that got me thinking - what would a bass sound like without the magic sonic benefits of wood? I couldn't quite imagine a completely non-wood instrument at the time and decided it required some further consideration.

Re-thinking the basic operation of a stringed instrument, it mostly boils down to providing a structure that can support both ends of a piece of stretched string so that it can be struck and resonate at a known frequency. The structure needs to be sufficiently rigid so it does not 'suck-out' particular frequencies, which is where the wood could add its sonic flavour. After that, the rest is just adding convenience, ergonomics and a bit of window-dressing.

In a cross-sectional view of a conventional guitar neck, a D-shaped back is typically mated to a larger radius curved f-board. Both the front and back surfaces are curved. Arguably guitars are easier to play with a smaller f-board radius and seem unnatural when it is too flat. 

Inspiration came from daydreaming about orange Lamborghinis again. Round tubing is used for various chassis members, spaceframes and exhausts for cars and bikes as it has a good strength to weight ratio. Lengths of stainless steel pipe are readily available and could be used as a basis for a string support system. The tubing inherently offers a generous f-board radius as standard and a rounded back that should fit the hand nicely. 

The downsides? All standard hardware (tuners, nut, frets, bridge & pickups) are designed to fit on a conventional guitar that is predominantly flat. Each of these items will have to be tailored to suit life on a tubular bass. This has the greatest possibility of a completely different sonic signature - it may sound awesome, or terrible, or just plain average. I need to find out if wood is good or steel is surreal!