Restoration of a Radiguet & Massiot quadruple Bonetti machine
Introduction:
In June, 1999, my university received a donation of old medical equipment, that belonged to Dr. Rubens Ferreira (1901 - 1972), that used it for medical purposes and research on electrotherapeutic techniques, starting in the 1920's. Among the items was a big quadruple Bonetti electrostatic machine. The machine was an enclosed classic Bonetti machine (sectorless Wimshurst) with neutralizers made of sets of three brushes, and electric motor drive, very similar to this one, but with 8 disks. The machine had a small label attached to the top of the case, almost unreadable, saying: RADIGUET & MASSIOT, constructeurs, PARIS, 15 Bard des Filles du Calvaire, 15. This company apparently existed with this name from 1899 to the 1930's (exact dates to confirm).
Original state:
The machine was received partially disassembled, almost complete. The support with the eight 55 cm ebonite disks and the glass bars that support the charge collectors were in place. The other parts were disassembled. Three extra disks can be seen on top of the machine.
The wooden box and support were in reasonably good state, requiring only some cleaning and varnishing (but I would like to remove an ugly green paint that was under the varnish). The motor (not the one in the picture) was an old Siemens type, requiring only some cleaning, painting, and adjustments too. The disks were in reasonable shape, but showing some wear marks from friction with the brushes, some warping, and some of them were with a brown color, indicating deterioration of the ebonite. The disks were of two different thicknesses (~2.5 mm, ~4 mm) and the thicker ones had three fixation holes, not used in the machine, indicating that some of them were reused from another machine, probably the same from where the extra disks come, as they are of the same size and have identical boss marks and fixation holes, with the central holes enlarged in the disks mounted in the machine. With the machine were received also several broken disks, that appear to be the originals of this machine, and some brush supports that appear to have belonged to other machine.
The charge collectors, neutralizers, and other brass metallic parts were all very oxidized and dirty, with the original nickel plating mostly gone. Several screws in the neutralizer assemblies were missing, or replaced by inadequate substitutes. One of the charge collector main conductors was damaged, with the output tube broken, and repaired by nailing it back to the wooden block that fills the conductor tube. This wood there was deteriorated, and all the assembly was loose. The bars holding the neutralizer brushes were of two different thicknesses, with the brush assemblies correspondingly different. Another indication that this machine possibly contains parts of two machines.
The charge collectors were connected to the output terminals of the machine through two holes in the glass plates of the box that encloses the machine. Two lengths of flexible metallic tube and two balls made the connection between the main conductors and tubes that support the terminals. Protecting the holes in the glass were two ebonite structures consisting of a threaded tube with two rings, that pressed against the glass from both sides. Between the glass and the rings there were several paper rings as spacers. It was interesting to see the several of the rings were made from a Brazilian calendar from 1928.
Restoration:
I started the restoration by cleaning
the collector and neutralizer assemblies. I disassembled the
broken collector, removing its tubes and the internal wood block.
I removed also the old corroded thin metal (copper) blades that
formed the charge collectors facing the disks, The supports of
the upper neutralizers had cracks, that I soldered, and a
broken end, that I replaced. After the cleaning, with soap and
water, diluted muriatic acid, and steel wool, I reassembled the
systems partially and took these pictures, of the charge collectors, upper
neutralizers, and lower neutralizers.
I had the nickel plating of all parts redone in a plating shop, with reasonable results only, since some parts were pitted by corrosion and had cracks. I added new screws to replace the missing ones in the neutralizer assemblies. I replaced the two balls holding the two outer neutralizers of the lower assembly, that were different from the others, with holes of wrong sizes, almost certainly not original.
I replaced the rotten wood block at the center of the damaged charge collector by a new one, and fixed the broken end piece by essentially the same method previously used, using two small screws. The other charge collector had to be disassembled, with the tubes removed, for the plating process. The wooden center could not be removed, and I left it as it was, a bit rotten too. I reassembled the collectors, with a light glue to fix the parts together, making easy some future disassembly. I could clean, straighten, lacquer, and reuse most of the copper blades that face the disks. I made a few new ones (four) to replace the most badly damaged.
The disks were supported by a heavy cast iron structure consisting of two supports with the shape of an "A" with two horizontal bars and a rectangular base with rounded corners and a rectangular hole at the center. These parts were interconnected by 8 screws and nuts. They were originally (?) painted with a dark green color, and were very dirty. I scrapped away the dirt and loose paint, sanded the surfaces, and repainted everything in a similar (lighter) color. The original painting had apparently a rough, textured, surface, that I didn't try to reproduce.
The lower axle required a lot of work, as I decided to disassemble it (a bad idea...). The five brass pulleys there were firmly attached to the steel axle by four steel screws each. Most of the screws were impossible to remove with a screwdriver, and I had to remove them using an extractor tool and other radical methods, that destroyed them. I could, fortunately, make identical screws to replace them. I cleaned everything, repainted the pulleys and reassembled the axle. At the back side of the axle, there was a small gear (with some broken teeth), that was once attached to a larger gear with a crank, allowing the manual operation of the machine. The crank, large gear, and support structure for it were missing. At the same side, at the end of the axle there was a large wooden pulley, mounted in a threaded brass support (the thread was inverted), used to drive the machine using the motor. The lower axle was made of steel, and run on two simple bearings in the "A" frames, lubricated by two grease boxes mounted above the bearings. The axle was very worn at the areas of the bearings specially at the back side. I added a layer of aluminum foil cut from a can there, with good results, at least for some time. The grease boxes were cleaned, replated, and filled with new grease.
The charge collectors were supported each by two glass columns ending in nickel-plated brass pieces. One of them was broken at the base and joined back with an excessive amount of epoxy glue, and one of the brass bases was bent. I disassembled everything, removing the end pieces from the glass bars by simply applying some heat, as the original glue was just sealing wax (I found pieces of paper with words in French inside some parts). The damaged column I could glue more properly, and then remount it backwards, leaving the broken area protected inside the top end piece instead of exposed at the base. I corrected the shape of the bent base by hammering with a wood block, and had the metal parts nickel-plated before reassembling everything.
The disks were mounted in five brass bosses. The two outermost disks were mounted in bosses with one pulley, and the other six in three bosses with a central pulley with one disk at each side. The disks were fixed to the bosses by flat brass disks with threads running over projections of the bosses, passing through holes at the centers of the disks. These brass disks had two holes, where a special tool could be applied to turn them, pressing the disks between then and the bosses. The pulley assemblies were originally nickel-plated, and I had the plating redone. These pulleys ran over a steel tube, that was filled with grease, with a grease box screwed at each end, and with small holes, one under each pulley, for lubrication. The axle with the disks could be easily removed from the top of the "A" support frames, where it was fixed at the bottom of curved slots at the tops of the frames by pressure of two large manual nuts. Two screws with nuts supported the axle from below, allowing adjustment of its height and of the tension in the belts. I had the bosses and assessories replated.
I cleaned the disks using a furniture maintenance product based on carnauba wax and silicone, that I found excellent for use in electrostatic machines. As I didn't repolish the disks to remove the brown decayed ebonite in some of them, I mounted the disks with these sides at the inner side of the disk pairs. The four original thinner disks I mounted at the center, and the four thicker disks at the outer sides. These thicker disks didn't fit well in the bosses, with the round plates that fix the disks not screwing completely in the projections of some bosses. This caused some extra spacing between the bosses, and one of two rings that fit between the outer bosses and the structure was, at some time in the past, reduced in length to account for this. The thinner disks were somewhat warped, but not enough to impede the operation of the machine.
The brushes were made of many thin metal foil strips, some looking as bronze, others as silver. Along with the machine come several boxes full of extra brushes. I saved the original brushes, still usable but dirty, and installed those.
The motor was an old Siemens three-phases motor, and had a control unit with a triple switch, three fuses, and a resistance box attached to a speed control rheostat. There were also another switch and a fuse, probably for the heating lamps. The AC power (220 V) was applied to the switch, passing through the fuses to a connector at the side of the motor. At the other side, the three stator windings were interconnected. The rotor was connected to the resistance box through a set of three slip rings attached to the motor's axle. The motor was working, and I just cleaned and repainted it, disassembling only the ring assembly. The screws fixing the bearings were impossible to remove, and I couldn't open the motor. The control panel was rather worn, but still functional, requiring only some cleaning and varnishing. All the wiring had to be replaced. The motor was turning the machine through a leather flat belt. The belt could be reused after some adjustments in the clamp that closes it. Along with the machine come several extra belts and a box of belt clamps. The round leather cords connecting the upper and lower pulleys were in bad shape, and the replacements were too rigid and tending to break. I preferred to use new, thinner, cords, joined by metal clamps that come with the material. I had to true the wooden pulley in the lathe, as it was too irregular and causing strong vibrations.
The machine come with two sets of Leyden jars. One set was well built and in reasonable shape, but requiring cleaning, repainting, and the replacement of the metal plates (tin), that were corroded. Each jar was sealed by a well-made assembly composed of a screw, an ebonite plate, a cork, an ebonite washer, and a nut. A terminal ended in a hook and a ball was screwed at the rounded top of the screw, and a thinner bar at the inner side. This bar ended in two disks of metalized cardboard holding between them a disk of thin metal foil, with many strips cut at the edge, contacting the inner metal plate of the jar. The outer plate was embraced by a metal strap, closed by two balls fixed to a threaded bar, holding a connection chain. The border of the glass tube was painted brown Restored jars. I replaced the metal plates by aluminum, and had also to replace the corks, that I had to break to open the tubes. This set, however, isn't capable of operation on very high voltage, as the glass has some bubbles and one of the jars is cracked at the bottom (there is an evident leakage of charge there, and I will have to find a way to repair the crack or replace the glass tube), Their capacitance is 55 pF. The other set of jars was more simply made, with thicker glass, closed with a simple cork, with a bundle of bronze wires for the internal connection, and no trace of the outer plate connections. One of the jars was broken at the top, but I could cut out the broken part and will try to restore it as a shorter jar.
The machine could be reassembled for initial tests by the end of September 1999:
The complete machine, ready for initial tests, seen from the right, left, front, and back
sides. Below can be seen fur pads, probably used to excite the
machine by friction (I consider this almost impossible), and two
wood bars covered by cloth, used to remove dust from the disks.
Excited by a Voss
machine through the terminals, it quickly starts, and produce
a torrent of long sparks in the
terminals of the small machine.
Sparks at the machine's terminals: short,
without Leyden jars, longer, and
long, with Leyden jars. More than this
would require stronger Leyden jars (my plastic jars ended perforated).
The original jars were still in restoration.
More details from the machine:
A heating lamp. This is not one of the
originals, that were smaller. These lamps are more beautiful, also old (1936)
and come along with the machine. They are not necessary for startup in
the restored machine, with excitation by another machine.
Disks and brushes, seen through an
open side door. Other side.
Flexible connection from one of the
charge collectors to the corresponding terminal.
See also the restoration of a Ducretet & Roger Wimshurst machine.
Created: October 1999
Last update: 19 January 2000
Antonio Carlos M. de Queiroz
http://www.coe.ufrj.br/~acmq
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