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Building a Scrap Slide Guitar

I was inspired recently by some videos online and on TV of some country/folk musicians that have a remarkable talent when it comes to making musical instruments from disused household objects. Some examples include an old shovel, a cigar box and even two car hubcaps all used to create very clean and unique sounds. Having developed my interest in electronics from an amateur interest in music, building a homemade instrument sounded like a perfect project.

Having already completed my slide guitar, I decided to document and share my experience on DesignSpark, which can be found below.

Materials

  • A length of 1000x100x20mm scrap pallet wood
  • Block of random scrap wood 100x50x20mm
  • <1mm mild-steel offcuts around 80x100mm
  • A pack of 6 guitar string tensioners with self-tapping screws.
  • M8x80 screws x 2
  • M8x30 screws x 6
  • M6x30 screws x 2
  • M8 nyloc hex nuts
  • M6 nyloc hex nuts
  • M8 plain nuts
  • M8 penny-washers
  • M6 plain washers
  • Two humbucker pickup assemblies
  • SPDT toggle switch
  • 3mm mono-jack
  • Ernie Ball “Power” guitar strings

 

Instrument Body

My instrument of choice was ideally a guitar but I wanted to stick with the disused object theme so I decided to make a very simple slide guitar out of the wood from an old pallet, which turned out to be the perfect thickness for body strength and ergonomic usability. By removing the nails from the pallet and cutting the nail-holes off each end, I had a perfect length piece of rough looking material to base my rough looking instrument on. Engineering precision is out the window on this project I’m afraid!

String Tensioners

I decided to drill the holes for the string tensioning mechanisms first as the wood was the perfect thickness for the tensioning components to fit through. I drilled six holes for each sting tensioner, three on each side, 15mm from the edge, with 30mm spacing, enough for the winding heads to operate side by side. Each mechanism was then secured to the body with two small self-tapping screws.

String Spacing

The guitar “nut” or what could be called the "string spacer" was again made out of a miscellaneous piece of scrap wood, by using a thick handsaw to create six grooves, the strings can be held at the correct spacing. Each groove was 10mm apart and around 3mm deep. The spacer was held in place by two long M8x80 screws that I had lying about, secured to the instrument body with nyloc hex nuts and M8 penny-washers with plain nuts added to easily raise and lower the height of the wooden spacer which in my specific case turned out to be around 40mm from the body.

String Anchors and the Knife-Edge

In sticking with the improvised aesthetic, I decided to use some rusty scrap steel at the opposite end of the instrument body to make the string-holding “bridge”. By drilling a set of six 10mm spaced, 2mm pitch holes, offsetting them 10mm from the top of a square off-cut, I was able to hold the strings in place with each strings’ respective “ball-end”. Measuring 20mm from the top of the steel workpiece, the bridge was then bent to around 45 degrees using a bench vice, some muscle and the liberal use of a hammer. This bend will make sure the stings will not rub against the edge of the holes under tension.

The same vice technique was used to create the knife-edge by bending the steel over 180 degrees to create a rounded end that would not cut the string under tension. The steel was bent 90 degrees in the vice then softly hammered further into 180 degrees. This component is used to give the correct string height, at 30mm, needed to place the pickups underneath. It also allows the strings to resonate cleanly at the correct pitch with minimal acoustic damping.

Both metal offcuts were drilled and secured crudely by M8x30 screws, fastening the components tightly to the instrument body with M8 nyloc nuts and some squarely drilled 8mm holes. The final “bridge” assembly as a whole measured at 110mm in length. As a keynote, excuse the pun, the playable region of the guitar should aim to be around 650mm, knife-edge to knife-edge, which is the vague point of reference that I derived from my existing Stratocaster style guitar.

Electronic Elements

For the electronic elements of the project, two pickups were used to passively capture the resonation of the strings. Much like a normal electric guitar, the positioning of the pickups was intended to change the instrument’s tonality (timbre) upon individual selection with the toggle switch. Each pickup had two threaded mounting points and were supplied with two long mounting screws that could be used to mount the pickup to the wooden body by drilling small holes squarely through it.

Each pickup can be exclusively selected for output through a standard 6.3mm mono-jack using an SPDT toggle switch which is mounted on a 90-degree bracket. The bracket was made from another steel off-cut of around 60x90mm and again bent by hand in a vice to give two 30x90mm faces. Each bracket face used two 30mm spaced holes, one for the panel mounted components and the other for two M6 screws to fasten the bracket to the instrument body, using M6 washers for strength.

The components were then soldered together, with the non-common contacts of the toggle-switch soldered to each pickup respectively and the common contact going to the output channel of the mono-jack. As the pickups are passive inductors there is no polarity to worry about when connecting them up. All other loose-ends were soldered to the ground contact of the mono-jack.

Strings etc.

The last step of the build was to add the strings. I used standard guitar strings which can be found at most music stores. As this guitar is “fret-less” you will also need to buy or make a slide tool to actually play the instrument which gives it a Hawaiian or American-south sound. You will also need a good ear for finding the notes in a key which makes it easier to play as part of a band or with a backing loop. In terms of sound quality, it is actually very clean, with no buzzing or excessive damping and is very fun to play and experiment with.

The overall cost of the project was around £10.

A keen electronic engineer with a passion for automotive systems and autonomous robotics. A progressive love of cars, engines and classic mechanics. Advocate for clean energy, transport and alternative fuels. Compulsive tea drinker. BrightSpark 2017. BEng MIET

17 Apr 2018, 10:53

Comments

April 30, 2018 11:20

It would be very interesting to see your creation in action. How about a YouTube video link here?

May 1, 2018 07:59

@ellisjr Thanks for your interest. I have been meaning to do this provided I can get some reasonable quality video recording equipment. :)

April 17, 2018 15:24

Just bought an Ibanez S670QM for £530, was expecting it to be £550, so with extra £20 saved, I could get two of these for that Hawaiian sound. Nice one Josh, love it.

April 18, 2018 11:21

@GreigRS Thanks for that, I'm glad you like it. It certainly is a good addition to my instrument collection and I have created some interesting soundscapes using my looper. Doing this project has made me think a lot about how to create music using engineering and it definitely won’t be the last time I do so…