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Building A Modified 5 Octave Marimba in North America

By Jim McCarthy | September 24, 2011

Hi all

Well the American Summer of 2011 saw me spend about five months in Saskatchewan, Canada. And as I now plan on doing this on a regular basis, it seemed only natural that I needed to make a marimba for use here – certainly you can’t just pop a five octave marimba in your suitcase every trip! So I started building one using my P524 design in the last couple of months – just in a slow way in spare time. Unfortunately I had to get on a plane and head back home to Australia before had a chance to finish, but I will finish the instrument right away when I return in 2012.

In the meantime – here are a couple of blog posts to show some of the modifications I decided to use. Some of these are just because they are a little better or simpler in some way, and others are because the materials readily available in North America differ just a little from those “back home” in Australia. This never really presents any big problems – just means a few alternatives had to be used.

modified marimba frame design

This first picture shows the most fundamental modification, which is the lower support and diagonal structure of the frame. You can see that in this version of the P524, have replaced the diagonals that went from the middle area of the horizontal struts to the lower parts of the end sections…. with this – an added lower horizontal strut with diagonals going the other way – ie from the UPPER part of the end sections to the middle area of this new horizontal lower strut. This method is not structurally a whole lot stronger or anything like that – it may be a fraction more simple in the dismantling and set up though and has less risk of breaking the diagonal structures whilst setting up. The original design was fine when bolted together but was a tiny bit at risk when dismantled. THE MAIN reason for this modification though was actually to provide a bit more room for the resonators at the big end as they bend at the bottom. You will see more about this in the next post… but I realized that the bends I had available in the PVC pipe were bigger than the ones in OZ, and took more room!

frame diagonal detail 1frame big end section modification

These two pics show the detail of the diagonal at the big end. Note how an extra bit of timber is positioned between the two middle verticals – this is where the top of the diagonal is bolted.

frame diagonal detail 2Here you can see how at the low end the diagonal is simply bolted to a fitted piece on the lower horizontal. It was tempting to just bolt right onto the side of the horizontal itself… but doing it this way meant the lower horizontal and the diagonal could both be perfectly in line and on the exact centre line of the instrument frame.

resonator support bracket mountingThis photo shows the slightly wider timber blocks I’m using on the bar support struts that the aluminium resonator support pieces are bolted to. This method was not the one originally outlined in the P524 building guide, but the guide did suggest it as an alternative. I decided to use it here. It looks a fraction chunkier, but it DOES have a couple of advantages. Firstly it only requires a SINGLE timber block on each of the outer strut connection points rather than two – and secondly it allows the use of standard imperial bolts with wing nuts which are cheaper and easier to use than the allan key bolts.

frame big end section modificationAt the big end of the frame, I’ve replaced the fully height adjustable mechanism for the lower resonators with the tried and trued slots. You can see I’ve used two different depth of slot calculated carefully to cater for the likely variations in playing temperature. SO The low resonators can sit at TWO different distances from the bars… but this method is a lot faster and simpler to make, and is much less prone to creating phantom creaks and movement in the resonators!

small end section frame detailAt the top end of the frame, the design is really the same… but you can see from the picture that rather than have a block of timber between the horizontal struts, then ANOTHER smaller block to go between the resonator struts…. I’ve made it all from a single piece. It just looks a little neater and leaves less screw holes to fill!

This whole frame is made of nice hard oak – a great frame timber as it tends to resist and suppress vibration – it sucks for bars but that is perfect for a frame! Compared to similar timbers in Australia this was actually pretty inexpensive and all easily available from the local Home Depot store. Some of the sizes are a little different from the original spec – but there was little thinking involved as the guide had allowed for this, So I could just follow my own advice and instructions from the guide on these modifications! So all in all this frame building was a pretty quick process!


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