<BalMec>


<Prop1>, <Prop2>, <Prop3> :three remote controlled large airplane propellers

<Bello>: remote controlled industrial electric bells

<Balsi>: motor driven siren

for Ballet Mecanique , George Antheil

by

Godfried-Willem Raes

in part commissioned by the Ictus ensemble

2014-2017


George Antheil (08.07.1900 - 12.02.1959) was a great admiror of the futurists ideas. Hence he introduced quite a variety of industrial noises in his orchestral music. The ballet mecanique, a ballet for machines,  prescribes no less than three airplane propellers on stage together with a battery of seven industrial electric bells, some 16 player pianos, a siren and percussion. It was written between 1923 and 1924.   All too often, orchestras performing this music fake these essential components either by subsituting them with percussion instruments, or even worse, by sampled sounds reproduced on loudspeaker channels. Needless to say that this goes against the composers original intentions, although during his entire lifetime he never got these components working as conceived.  Just like Igor Strawinsky in his original version of Les Noces, he even never got the player piano's to play in sync... Nowadays it ought to become possible to realize all those ancient dreams, even though the composer during his lifetime has compromised his own ideas on many occasions.  In some performances of the Ballet, large fans have been used and -as these devices are pretty noiseless- the composer had the players hold sticks against the blades... This clearly doesn't lead to anything like an airplane sound  However, having working real airplane propellers on stage was and still is, not a trivial undertaking. The construction of these elements, such that they can safely be used in performances, was confined to us as a collaborative project with the Ictus ensemble.

Propellers:

We started off by tracing suitable real airplane propellers -not fan blades- and studying the mathematics and physics of their behavior, as obviously having them rotate at the normal speed as on an airplane would entail very high thrust forces to be developed. Prohibitively dangerous. Hence we designed the motors such that all forces developed are in a safe range. Also we designed the structures such that they produced blowing wind, instead of sucking wind as in aircraft. Doing so, the forces are always developped backwards. The artistic problem is that at too low speeds, the propellers do not make the airplane noise requested and wanted by the composer. This lead us into researching the shaping of the blades such as to make them produce more noise. Another research topic was to consider the possibility to let the fan blades closely cross the edge of low pitched resonator tubes, thus provoking the typical low frequency noise of an aircraft propeller. This also makes possible the rhythmic notation used in the score. On propeller 1 such a resonator was build. The result is very convincing. A similar design on the large propellers was impractical as the resonators would become physically to large. Maybe Helmholtz resonators could be applied here.

Propeller 1:

This is a rather small propeller, span 660 mm (26"), carved from wood. The motor used here is a DC motor, making precise control relatively easy. The motor rotation is transmitted to the propeller axle with a V-belt. The gear ratio can be changed by mounting different pulleys. An adaptor piece was turned on the lathe to make the propellers central hole fit the axle. This was fabricated from a piece of nylon, outer diameter 30.0 mm, inner diameter 14.5 mm, length 45 mm. The propeller axle is mounted on a steel holder made from a piece of HEA 100 x 100 profile. The axle is mounted on this part with four M10 x 35 bolts. The motor base -in construction steel as well- is cut out from a 450 mm long piece of 100 x 50 x 4 rectangular profile, also serving as a resonator. At the back end of this tubing, we constructed an acoustic horn to amplify the sound in the 80Hz to 130Hz range.  The horn is folded, with the opening pointing to the audience.  This yields a quite convincing airplane sound, although below the sound pressure level of a real prop-engine.The motor power was calculated to stay below 10% of the nominal power required for use on an airplane (estimated at some 5 to 8 kW). The whole structure was firmly welded together.

The electric control of the propeller is not as easy as it might seem. As long as we only have to cope with very slow changes of rotation speed, we can live with just variable voltage control on the motor. However, if we want relatively fast braking, we have to deal with the problem that the motor -due to the inertia of the propeller- will become generative. This imposes the use of braking resistors and precise electronic control. Hence the PIC microprocessor (an 18F2525) needs two PWM controlled output channels: one for speed control, one for braking. Also the analog input channels can be used to monitor motor -and thus propeller- behaviour at all times. This is the circuit we designed for the MIDI control of the propeller:

As we anticipate that in practical use, the distance between the different components of the setup might become relatively large, possibly exceeding the 5 to 10 meter limit for MIDI cabling, we provided in differential line drivers on all MIDI boards. With these, cables up to 100 meter in length can be used. For reliable performance, screened twisted pair cable should be used. DMX cable, properly terminated works very well.

The firmware for the 18F2525 microprocessor can be found here: Propeller1.bas

Midi implementation:

  • Channel 13
  • The propeller is mapped on note 40
  • Note-off stops the propeller. The release byte controlls the braking force.
  • Note-on with velo = 0 turns the propeller off without braking.
  • Note-on with velo> 0 makes the propeller rotate at a speed proportional to the velocity value.
  • Notes 120 and 121 are mapped on red LED spot lights, flashing speed being a function of the velocity byte. Flashing speed can be controlled with the key pressure command.
  • Controller 66: enables (>0) or disables (=0) propeller operations
  • Controller 123: all notes off, stops the propeller, stops the lights.

Warning:

This machine is potentially very dangerous. It should be set up at least 1.5 meters above where people can be. Make sure there are no loose objects behind the propeller as it would suck them forward. The wind production of this machine can be considerable. When not in use, the machine should be fully switched off with a remote switch. We did mount a switch on the machine but using this for turning off the propeller involves a serious danger for the operator. Also we assume no responsibility for accidents as a result of using the machine with other midi sequences than those we provide.

Propeller 2:

This propeller is also made of wood, but coated with polyester and carefully balanced in the Hofman propeller factory. The wind span is 1890 mm. Size of the axle mounting hole: 58 mm, provisions made for flange mounting with 6  M12 bolts.propeller 2
The motor used to drive it is a GPM90, 0.75kW DC motor designed for 180 V DC operation at 1500 rpm. This motor is powered from the mains single side rectified voltage directly. This is the circuit for the control:

And, this the PCB for the above circuit. As we did not find enough space on the board to accomodate a 2.2mF / 450V electrolytic as originally foreseen in the schematic, we mounted a 470uF/400V type. If a larger value is required it will have to be added off-board. The motor brake relay as well as the braking resistor (or light bulb) should be mounted on the motor itself. As parts of the PCB are directly coupled to the mains voltage a word of warning may not be misplaced here: this board does carry high voltages! Do not touch. There is galvanic isolation between input and output, so using the circuit involves no danger. The steel structure itself is properly grounded.There are two automatic fuses on the machine making it possible to cut all power, however these fuses should not be used as a switch taking into account that being in such close proximity to the propeller entails a danger in its own, For safety reasons we advise users to use a switch in the power wire at least 5 meters away from the engine.

The motor for this propeller is a flanged type, so it was a lot of work to construct a well fitting flange to fit the motor on the HEA220 profile base. The center hole has to be 130 mm diameter and the M12 mounting bolts have to be countersunk types.

When braking, the motor becomes a generator. To make reasonably fast braking possible we provided a braking resistor switched over the motor windings on a stop command. In fact this resistor is a 205 W halogen bulb (Osram). The normal resistance would be 258 Ohms, but when cold this value is down to 25 Ohms. It is absolutely normal that this lamp will never glow in this application.

These are pictures of the left and right side of the circuitry for propeller 2:

The firmware for the PIC microprocessor can be found here.

Midi implementation:

  • Channel 13
  • The propeller is mapped on note 38
  • Note-off with a release value makes the release value control the braking force.
  • Note-on with velo = 0 turns the propeller off and uses default braking
  • Note-on with velo> 0 makes the propeller rotate at a speed proportional to the velo value.
  • The two red lights are mapped op notes 122 and 123. The velocity byte steers the flashing speed.
  • Controller 66: enables (>0) or disables (=0) propeller operations
  • Controller 123: all notes off, stops the propeller.

Warning:

This machine is potentially very dangerous. It should be set up at least 2 meters above where people can be and securely bolted or clamped to the holding structure. Make sure there are no loose objects behind the propeller as it would suck them forward. The wind production of this machine can be considerable. When not in use, the machine should be fully switched off with a remote switch. We did not mount a switch on the machine as doing so would involve a serious danger for the operator. Also we assume no responsibility for accidents as a result of using the machine with other midi sequences than those we provide.

Propeller 3:

This is a heavy duty propellor made in metal, presumably a magnesium-aluminium-titanium alloy. The wing span is 1740 mm and the axle hole is 58 mm. As on propeller 2, it is also designed to be mounted on a six hole flange.propeller 3
The motor used to drive it is a GPM90, 1.3kW DC motor designed for 180 V DC operation at 1500 rpm. The circuit for the control is almost identical to the circuit used for propeller 2, but here we used a separation transformer avoiding the trouble we had with a first version using single side rectified mains voltage directly. Thus many improvements were added to the PCB design as well..

This is the circuit drawing:

And, the version 3 PCB design looks like this:

The power relays, the fuse holder and the SMPS 12V power supply found a place on another printed circuit board: Making this board made final wiring a lot more transparant than was the case for propeller 2.

These are pictures of the left and right side of the circuitry for propeller3:

 

As it is the case with the notation in the score for the siren, it is unclear at what speed the propellers are supposed to sound. It is technically impossible to start/stop propellers fast. We found a solution by providing a switchable resonator for the propellers that can switched on very fast. Thus it would no longer be required to have the propellers themselves to change speed rapidly. As yet, this feature is under study.

The firmware for the PIC microcontroller can be found here.

Midi implementation:

Technical specifications:

Warning:

This machine is potentially very dangerous. It should be set up at least 2 meters above where people can be and securely bolted or clamped to the holding structure. Make sure there are no loose objects behind the propeller as it would suck them forward. The wind production of this machine can be considerable. When not in use, the machine should be fully switched off with a remote switch. We did not mount a switch on the machine as doing so would involve a serious danger for the operator. Also we assume no responsibility for accidents as a result of using the machine with other midi sequences than those we provide.



Electric bells <Bello>:

See separate page with details on this robot.


 

<Balsi>: Large motor driven siren

The instructions in the score render it impossible to use a standard crank driven siren, as it is detrimental to the gears in these devices to be started and stopped fast. So an electrically driven mechanical siren with safe braking possibilities or fast sound control has to be designed. The score is very unclear as to the pitches the sirens are supposed to sound. In the score they appear notated as percussion instruments. We made already a few siren driven robots: <Sire> , a robot using 24 small sirens as well as the large siren integrated in <Springers>.

The documentation for <Balsi> is on a separate webpage. Click here.



Player Pianos:

The original score requires 16 player piano's, although there are only four autonomous tracks. The reason behind this, is that on traditional piano rolls, it is impossible to have that amount of notes as the paper would fall into pieces. Obviously electrically driven automated pianos do not have this restriction making performances using just 4 player pianos perfectly possible. All performances so far if using player pianos (and not sample-based midi keyboards with their uggly sound...) at all, suffered from the problems associated with commercially available midi controlled pianos: latency (500ms),  lack of polyphony, weak dynamic possibilities.  This is the case for the Yamaha Disklavier, the Q&R vorsetzers etc...  The player pianos as we designed and build do not have any of these problems. Detailed descriptions and comments on our Player Piano's can be found on this website. The only problem is that at the time of this writing (2015) we made only two copies. So either we have to make two more vorsetzers, or rearrange the score to get it played on the two pianos we already have.

Musicians parts:

The score calls furthermore for three xylophones, two grand pianos, a tamtam, four bass drums. It is perfectly possible to also confine these parts to real musical robots. Our <Xy> robot can take care of the xylophone parts. Automating the bass drums and a tamtam would be pretty straightforward...


Midi Implementation for all components of <Balmec>

The Balmec project was conceived to work like all other musical robots we have built. Hence it makes use of one unique midi-channel and all components of the project are mapped on midi notes and controllers.

Midi channel: 13 (counting from 0) for all modules.

Note On/Off mapping:

Note 24: Siren. The maximum speed is controlled by controller #24. Note-On commands let the siren speak freely, Note-Off commands mute the siren. To stop the siren motor, controller 24 must be set to zero.

Note 36: propeller 3 (large metal propeller). The speed of rotation is controlled by the velocity byte
Note 38: propeller 2 (large wood propeller). The speed of rotation is controlled by the velocity byte
Note 40: propeller 1 (small propeller). The speed of rotation is controlled by the velocity byte

Notes 51 - 93: Electric bells on <Bello>.  The velocity byte steers the loudness (the force of the stroke) and repetition rate can be controlled with the key pressure command. The repetition speed set with the key pressure command is 'sticky', so users do not have to send it again for every note. The key pressure command can also be sent when no notes are playing. If the repetition rates are set high, low velocity values ought to be used.

Note 119: switch on/off the red LED bottom lights on <Bello>. The velocity steers the brightness of the light.

Notes 120 and 121 switch on/off the red LED spotlights on propeller 1. The velocity steers the speed of the flashing. Keypressure can be used to further modulate the flashing speed.

Notes 122 and 123 switch on/off the red LED spotlights on propeller 2. The velocity steers the speed of the flashing. Keypressure can be used to further modulate the flashing speed.

Notes 124 and 125 switch on/off the red LED spotlights on propeller 3. The velocity steers the speed of the flashing. Keypressure can be used to further modulate the flashing speed.

Notes 126 and 127 switch on/off the red LED spotlights on <Bello>. The velocity steers the speed of the flashing. Keypressure can be used to further modulate the flashing speed.

Controller 66: Switches off all components when the data byte is zero. If a non-zero value is sent, the components are powered on. Controller 66 with value zero also resets all controllers to their default startup values.It also resets the note-repetion rates on <Bello>.

Controller 123: All notes off, without affecting any controllers nor key-pressure settings.

Prof.dr.Godfried-Willem Raes

Collaborators on this project:

 


Cost calculation:

Propeller 1:

Materials:

Thomson DC motor 700W  
600
Propeller
150
Transportation propellers
152
Ball beared axle, cast iron
240
Steel profiles and plate material
80
Welding materials
40
Bolts and nuts
40
V-belts QPIII XPZ
20
MIDI control board
220
M10 stainless steel bolts
26
500 VA transformer 2 x 40V
135
10000uF/200V cap
85
Power rectifier
4
Red copper, 1kg, nose piece
13
Polyurethane varnish
5
Steel plate 3mm thick
 10
 ZnO steel painting
 2
 Grinding and cutting disks
 20
LED spotlites
45
sum
1887


Labor:

Welding and metal works 2 days
700
Lathe works 0.5 day
175
Painting and assembly 1 day
350
Testing 0.5 day
175
Circuit & PCB design 1 day
350
 Horn construction  3 days
1050  
 PCB production and soldering  1 day
 350
Firmware development and writing of testcode under GMT  1 day
350  
Final assembly 0.5 day
175
Mounting of LED spotlites 0.5 day
175
     
sum  
3850

End sum:                                  5737

TO DO:


Propeller 2:

Materials:

DC-Motor GPM90 0.75kW  
1038
Propeller
200
Axle adaptor (lathe work)
273
PCB motor control + components and microcontroller
250
HEA220 profile
80
Steel plate material
50
50 mm x 50 mm x 4 mm profile (legs) ( 3 m)
70
Bolts and nuts
40
Grinding and cutting disks
40
Welding materials
35
Mains power entry plug CEE 16A/230V
20
LED light clusters (Kingbright)
22
18 Ohm power resistors on lugs
10
12 V power supply
50
Mains fuses and socket
30
Power relays and IRF540 MOSFET
58
Braking resistor
10
Polycarbonate plate
90
sum
2366


Labor:

Circuit & PCB design 2 days
700
 PCB production and soldering  1 day
350
Firmware development and writing of testcode under GMT  1 day
350 
Construction of the motor flange mount and cutting of the HEA220 beam 1 day
350
Welding of the tripod, cutting of the profiles, grinding and drilling 1 day
350
Wiring and electric mounting works 1 day
350
Painting with Zinc-oxyde gray paint 1/2 day
175
Final assembly, rail mount devices for safety and protection 1 day
350
Extensive hardware debug and fixes 1 day
350
Testing session. Final measurements and behavior evaluation. Final version of the firmware. Cutting, drilling and welding of the feet plates. 1/2 day
175
     
sum  
3400

End sum: 5766

TO DO:


Propeller 3:

Materials:

DC-Motor GPM90 1.3kW  
1334
Propeller
300
Axle adaptor (lathe work)
280
HEA220 profile
80
50mm x 50mm x 4 profile (legs) (3 m )
70
Motor control board with microprocessor, Version 1.0
380
12 mm thick steel plate, 10kg
30
LED light clusters (Kingbright)
22
Bulgin fuse holder with 6.3A fuses
12
Relay and SMPS board
150
Polycarbonate plates
90
Version 3.0 microcontroller board
380
Isolation transformer 1.6kW
250
sum
3366


Labor:

PCB production and soldering motor control board  1 day
 350
Firmware development and writing of testcode under GMT  1 day
350  
Technical drawing for axle construction on the lathe 1/2 day
175
Welding of the tripod, cutting of the profiles, grinding and drilling 2 days
700
PCB design relay, fuses and 12V power board 1 day
350
Painting with Zinc-oxyde gray paint 1/2 day
175
Safety screens made and mounted. Polycarbonate. Wiring finished 1 day
350
Testing session. Final measurements and behavior evaluation. Final version of the firmware. Cutting, drilling and welding of the feet plates. 1/2 day
175
Redesign of the processor board, soldering and making of a new board, mounting of the isolation transformer 2 days
700
sum  
3325

Endsum: 6691

TO DO:

  • design a Helmholtz resonator, if required.

TO DO:



Parts, technical specifications and maintenance notes:

Propeller 1:
The propeller assembly should only be used or powered, bolted with 8 M10 x 30 bolt and nuts to the stand. Letting the propeller run without the stand may let it slide over the surface, flip over and cause serious injury to people around. Even if properly mounted on the stand, people should be made to stay away at least 1.5 meter from the structure. In front of the propeller, a strong wind will be produced.

Motor specifications:

Our measurements, with the motor coupled to the propeller:

Motor voltage
Motor current
remarks
3.5 V
0.6 A
this is the minimum voltage required to cause the propeller to rotate
6 V 0.6 A  
10 V 0.78 A  
15 V 0.88 A  
20 V 1.1 A 22 W
24 V 1.29 A 31 W
30 V 1.6 A 48 W, at this voltage, the propeller starts to produce airplane sound
40 V 2.3 A 92 W
50 V 2.9 A 145 W
60 V 3 A 180 W
80 V 3.6 A 288 W
100 V 4 A 400 W. This should be considered the safety limit.

The propeller, made of wood, was coated with a polyurethane varnish. This varnish, sold under the name Debethane is made by Degryse n.v., Fabrieksweg 42 zone A2, 8480 Eernegem, Flanders.( www.degryseverf.be)

V-belt:XPZ617 / 3VX252

 

 


Logbook (for all modules and components in the Balmac project):


Order numbers spare parts and special (harder to find...) components:


Last update:2017-10-09