![](\"images\/test_caps_for_40mm_tubes.jpg\")
The top two octaves of a five octave marimba use 1 \u00bd inch pipe. The metric standard is 40mm \u2013 and both are available generally in North America but only in that thicker pipe. The solution here is simply to not use standard caps for this pipe, but to use instead the thin plastic \u201ctest caps\u201d. These work just fine and in fact look even better than normal thin wall caps when painted up nicely. Because the plastic is so thin though, it can be tough to accurately produce a tone by striking these on the end of the higher tubes though. This means that a few more than usual need to be \u201cpassively tuned\u201d \u2013 ie tested for good resonance under the finished bar, rather than tested with a tuner or stroboscope. The photo here shows some high resonators using these test caps \u2013 sometimes they come in orange colour also.\n
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\nThis photo here, basically shows the next two octaves down C#3 to C5 use 2 inch pipe. Here\u2019s the super easy solution! You CAN GET THIN WALL PIPE IN 2\u201d!! Even in a basic hardware store like Home Depot thin wall pipe is readily available with perfect end caps to suit. BUT don\u2019t lok for it in the plumbing section. Look for it in the section that deals with ducted vacuuming systems \u2013 that\u2019s what this type of pipe is used for in America and Canada. Using this solves the space problem, and is a whole lot cheaper and lighter to boot!
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\nShown here are two specific problem notes… C3 and B2. On this marimba they are on the end of the middle row of resonators. In Australia I simply use a 60mm PVC pipe for this which Is a medium wall thickness, and although not as common as others \u2013 still reasonably available and inexpensive. In the small city I was building in though in Canada… I could find virtually NOTHING between 2 inches and 3 inches that would do the job. Now actually you could get away with using just the same 2inch vacuum pipe for these two notes, but the bars ARE just a bit too wide and I like to match things up properly. SO I found this solution here… which is a 60mm electrical conduit. I could not find caps to suit, so for these two tubes I will have to make internal plugs \u2013 a pain \u2013 but it means the pipe is well matched. As this pipe has a thick wall, caps would likely take up too much space anyway.<\/p>\n
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This photo here shows the bottom row of resonators \u2013 the big ones! The highest of these was no major problem. In Australia we have a very common and cheap PVC pipe that is 75mm (3 inches) in diameter. It is used for stormwater and is very thin wall and the 90 degree fittings are very tight turns. Now mostly in North America, the black ABS is standard for 3inch pipe BUT you can get a thinner wall white PVC. It is even labelled with the metric 75mm! Admittedly I could only find this pipe in one of the major stores in the city I was in… but I have seen it in other American cities a fair bit. The Home depot stores I looked at had the fittings for the PVC pipe… but not the pipe!! Crazy!![](\"images\/low_resonators_03.jpg\")
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The bottom resonator on the prototype was a 4inch (100mm) pipe \u2013 and this pipe is available in both ABS and PVC generally. As it is just the bottom note you have a little flexibility in room because you can always shift things over a little \u2013 so it doesn\u2019t matter much what you use. Actually I ended up using this pipe for the bottom tube on the other row also \u2013 the C#2 \u2013 as it helped solve an issue there which I\u2019ll write about below. The bends on this pipe were not very tight either, so I repeated my trick of sawing away some of the join area. Even so though, there was no way I was going to be able to neatly fit this tube with the bend going inwards… so for this bottom resonator I went towards the player instead, and angled just a little outwards \u2013 it comes just inside the frame so I\u2019m happy. The C# is not fitted yet, but I anticipate it fitting ok with the bend going the normal way because there is a little more room to twist it towards the frame end \u2013 it does after all start half a bar width further up!![](\"images\/flanged_resonators.jpg\")
This left still a couple of resonators in the middle of this bank that would normally be made with 90mm pipe. In Australia, 90mm is another stormwater grade so cheap and easy and tight bends. I could not find ANY pipe though that would really do this job \u2013 what is needed is something in between the 4 inch and the 3 inch pipe. There just wasn\u2019t any where I was buying! My solution was to use the 3 inch pipe which at least fit.. BUT I made sure that the mouth end of the tubes under the bars.. was the flanged bits that come at the end of a whole length of tube. You can see in this photo here that the top sections of two tubes are wider. This is not ideal, but it does at least correctly match the impedance of the tube mouth to the bar \u2013 and with the thicker wall tube, it does not look silly making a one inch jump in diameter for the last note on the row.![](\"images\/replacing_rivet_with_screws.jpg\")