Pitched Percussion Robot

<Tubo>

 

Godfried-Willem RAES

2019 / 2020

[Nederlandstalige versie]

 

<Tubo>

Aluminum tubes were used in earlier robots such as <Tubi>, a quartertone instrument. In 2019, we did build the Plus-Minus project, using aluminum tube of greater thickness. Extending the register on the low side, appeared impossible using the same type of tube. When the tubes are made longer, the second overtone becomes dominant. Hence the idea to apply mensuring on the proportions. Thus this instrument uses aluminum pipes of different diameters. The tube lenghts can be calculated using following formula, valid as long as the tube length is at least 10 times larger than the diameter. The frequency for the first overtone, given by Olson as 2.758 times the fundamental frequency, after our measurements, it ought to be 2.705 times the fundamental. This is the pitch perceived on the attack of the tube. It can be measured exactly by suspending the tube exactly in the centre, the first overtone having a node there.

Note that the modulus of elasticity (Youngs modulus) is temperature dependent. This curve illustrates this dependency for aluminum: The variation is quite small, but when tuning, one had to be carefull to cool the tubes to ambient temperature before checking the pitch. Grinding and sanding makes the tubes very hot...

The alloy used for the tubes is AlMgSi 0.5 F22 (Werkstof nummer: 3.3206, International 6063)

The composition is: 0.3-0.6% Si , 0.1-0.3% Fe, 0.1% Cu, 0.1% Mn, 0.35-0.6% Mg, 0.05% Cr, 0.15% Zn, 0.15% Ti, 0.15% other elements, saldo to make 100% is Al

An alternative alloy is AlMgSi 1 (Werkstof nummer: 3.2315, international 6082)

Composition: 0.7-1.3% Si , 0.5% Fe, 0.1% Cu, 0.4-1% Mn, 0.6-1.2% Mg, 0.05% Cr, 0.25% Zn, 0.1% Ti, 0.15% other elements, saldo to make 100% is Al. However this alloy is only available in tubes 57/47. Nevertheless, we couldn't obtain this alloy as it appears not to be a stock item.

Tube sizing:

60mm / 50mm tube: (2.331 kg/m)

midi note frequency (Hz) length (mm) suspension m constant weigth kg
48 130.8 1627.5 365 1.1172  
49 138.6 1581 354.5 1.1169  
50 146.8 1536 344 1.1169  
51 155.6 1491 334 1.115  
52 164.8 1449 325 1.1157  
53 174.6 1407 315.5 1.1145  

55mm / 45mm tube: (2.200 kg/m)

midi note frequency (Hz) length (mm) suspension m constant weigth kg
54 184 1298 291 1.1045  
55 195 1261 283 1.1044  
56 207.6 1225 274.5 1.1033  
57 220 1190 267 1.104  
58 233.1 1156 259 1.1037  
59 246.9 1123 252 1.1036  

50mm / 40mm tube: (1.908 kg/m)

midi note frequency (Hz) length (mm) suspension m constant weigth kg
60 261.6 1040 233 1.1129 1.955
61 277 1010 226.5 1.112 1.906
62 293 980 220 1.1092 1.848
63 311 952 213.5 1.1089 1.801
64 329 925 207 1.1092 1.746
65 349 898 201 1.1075 1.698

40mm / 30mm tube: (1.484 kg/m)

midi note frequency (Hz) length (mm) suspension m constant weigth kg
66 369 773 173 1.1135 1.136
67 391 751.5 168.5 1.115 1.108
68 415 730 163.7 1.1146 1.076
69 440 709 159 1.1139 1.048
70 466 689 154.5 1.1145 1.018
71 493 668.5 150 1.1116 0.988

35mm / 25mm tube: (1.272 kg/m)
midi note frequency (Hz) length (mm) suspension m constant weigth kg
72 523 602.5 135 1.1121 0.765
73 554 585 131 1.1107 0.743
74 587 567 127 1.1055 0.721
75 622 551 123.5 1.106 0.701
76 659 535 120 1.1047 0.680
77 698 519 116 1.1015 0.660

30mm / 20mm tube: (1.060 kg/m)

midi note frequency (Hz) length (mm) suspension m constant weigth kg
78 739.99 466.5 104.6 1.1247  
79 783.99 453.6 101.7 1.1266  
80 830.61 440 98.65 1.1231  
81 880 426.5 95.6 1.118  
82 932.33 414.5 92.93 1.1187  
83 987.77 402 90.13 1.1149  
84 1046.5 391.5 87.77 1.1203  
85 1108.7 380 85.2 1.1182  
86 1174.66 369 82.7 1.1171  
87 1244.51 357 80 1.1078  
88 1318.5 347.5 77.9 1.112  
89 1396.9 336 75.3 1.1014  
90 1479
91 1567
92 1661
93 1760
94 1864
95 1975
96 2093 272.3 61 1.0839

 

The tubes have individual felt covered rubber beaters driven by solenoids as well as individual dampers. Musical dynamics are implemented by applying pulse width modulation techniques in the driver circuits both for the beaters and for the dampers. For the lowest octave the weight of the beaters has to be ca. 1/5th of the weight of the tube to be struck. The beaters have to be covered with a layer of felt. This condition necessitated the use of strong bidirectional solenoids for the beaters. In organ windchests these solenoids are always wired as: If the left winding gets current, the anchor moves to the left, with the right coil powered, the anchor moves to the right side. If both coils are activated, the magnetic fields cancel each other and no force is available from the anchor. If we use this type of solenoid in the following configuration, however: operation is quite different. When only one coil is activated, it will behave as before, but when both coils are activated, the anchor will move to he center and force will be available the keep it there, as both magnetic fields will reinforce each other. By controlling the current over both coils independently, we can make the coil operate as a linear motor.

It is important to build the instrument such that the beaters strike the tubes exactly at the point halfway their length, thus eliminating as much as possible the sounding of the first (inharmonic) overtone, having at nodal point at that place.

The dampers make this robot very different than the <Tubi> robot, where we did not use any kind of damping. With the dampers -the damping force can be controlled by the users- the robot becomes a valid alternative for our <Vibi> robot, an automated vibraphone. In <Tubo> open pipe resonators are coupled to all tubes up to note 86. This highly reinforces the fundamental pitch of the tubes. Due to the high mass of the tubes, the sustain of the tones is very long. However, <Tubo> has no vibrato mechanism (as <Vibi> has) and neither can it play quartertone music (as <Tubi> can). In orchestrations for the logos robotorchestra of orchestral music, <Tubo> makes a better alternative for the celesta.

As this robot uses many and heavy solenoids, it became a pretty expensive robot to construct.

 

Mapping:

Midi note range: 48-89

Note Off commands with release are required to activate the dampers. Velocity is implemented and has a wide controll range.

Midi controller 66 is used to switch the solenoid power on or off. It will also release all dampers.

The midi listen channel can be selected using the DIP-switches on the midi-input board. The setting is only read after a cold boot. of the microprocessor. The default midi channel is 15.

Techical specifications:

Design and construction: dr.Godfried-Willem Raes

Collaborators on the construction of this robot:

 

 

Music composed for <Tubo>:

 

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Nederlands:

<Tubo>

 

Bouwdagboek:

Omdat ons vaak wordt gevraagd hoeveel werk en tijd kruipt in, en nodig is voor, het bouwen van een muzikale robot, hebben we ook voor <Tubo> een beknopt bouw- en onderhoudsdagboek bijgehouden:

Afmetingen & andere technische specifikaties:

Belangrijke nota voor gebruikers:

Design en konstruktie: dr.Godfried-Willem Raes

 


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Tentatieve begroting:

Aluminium: 200 kg     1200.-
Sleeplade magneten 25 150 3750,-  
Kuhnke magneten HD8286-R-F 18     4134,-
Kuhnke magneten HD6286-R-F 6   96,- 576,-
Blauwe magneten 25 75,- 1875,-  

Tubular solenoids

Tremba ZMF-3865d-15.002 - 24V

50 64,-   3200,-
Inox       1000,-
Wielen en lagers       500,-
PVC (resonatoren)       500,-
Vibrato motor or solenoids 1     250,-
Vilt en rubber       200,-
Hasberg reflektor       100,-
Hub PCB       500,-
Mosfet driver PCB's       2000,-
Power supplies       1500,-
         
         
         

Arbeid:

geschat op 6 maand FT. (ca. 25.000 Euro)

Last update: 2019-07-16 by Godfried-Willem Raes