Dynohub

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Version vom 13. März 2018, 15:35 Uhr von Bikegeissel (Diskussion | Beiträge) (Weiter übersetzt und Struktur...)

Dynohubs sind elegante elektrische Generatoren, die sich in speziellen Naben befinden. Sie wurden über Jahrzehnte von Sturmey-Archer in England hergestellt und es gibt inzwischen neuere Varianten von Sturmey-Archer aus Taiwan. Nabendynamos werden auch von Schmidt, Shutter Precision, Shimano und anderen hergestellt. Diese sind allerdings keine "Dynohubs", weil das eine Handelsmarke von Sturmey-Archer ist.

Nabendynamos sind ziemlich schwer. Moderne Varianten wiegen Dank Seltene-Erden-Magneten und Aluminiumhüllen weniger. Alle Varianten sind jedoch absolut still und haben keine beweglichen Teile, die zusätzliche Reibung erzeugen würden. Sie funktionieren durch das Umkreisen eines ringförmigen mehrpoligen Magnets, der im Inneren eines übergroßen Nabenkörpers angebracht ist, um eine stationäre Spule, die mit der Achse verbunden ist.

Fortschritte bei der Magnettechnologie haben Nabendynamos deutlich leichter und leistungsfähiger gemacht als die originalen Dynohubs. Die Beleuchtungen sind Dank des Einsatzes von Halogen- und LED-Leuchten wesentlich stromsparender und können ein vielfaches an Lichtausbeute erzeugen als klassische Dynohub-Systeme. Die originalen Dynohub Systeme erzeugten eine Leistung von rund 1,8 Watt bei 6 Volt. Die meisten anderen Systeme erzeugen zwischen 2,4 und 3,6 Watt. Die Frontleuchten, die mit den Dynohubs ausgeliefert wurden, waren darauf abgestimmt, mit dieser geringen Leistung möglichst viel Licht zu erzeugen.

Ein originaler Dynohub liefert gleichwohl ausreichend Spannung für moderne LED Beleuchtungssysteme. Es existieren inzwischen sogar LED Birnchen, die in die Original-Raleigh-Leuchten passen. Die originalen Birnchen liefern nicht nur weniger Licht, sie sind inzwischen sogar sehr selten geworden. Von Zeit zu Zeit findet man die originalen Raleigh Dynohubs noch bei schweren Stahllaufrädern von Raleigh-Industries Drei-Gang-Fahrrädern. Üblich waren früher 32-Speichen Vorderrad-Laufräder mit dem GH6-Dynohub oder 40-Speichen Hinterrad-Laufräder mit der AG Drei-Gang-Nabe. Ein guter Funktionstest ist es, einen Schlüssel über die beiden Ausgänge zu halten und das Laufrad zu drehen. Wenn der Dynohub noch in Ordnung ist, fliegen Funken.

Dynohubs erzeugen Wechselstrom. Nabendynamos können im Gegensatz zu Felgendynamos vernünftige Lichtausbeute auch bei niedrigen Geschwindigkeiten erzeugen, weil die Wechselstromfrequenz niedrig ist. Die Birne leuchtet am Strompulshöhepunkt auf. Bei niedrigen Geschwindigkeiten pulsiert das Licht sichtbar, währen das Licht eines Felfgendynamos einfach dunkler wird.

Je höher die Geschwindigkeit des Dynamos wird, desto höher wird die Wechselstromfrequenz. Das ist praktisch, weil die Spule des Generators den Wechseltrom weniger effektiv weitergibt, je höher die Frequenz wird. So wird die Tendenz, immer mehr Spannung bei höheren Geschwindigkeiten zu erzeugen, effektiv ausgebremst. Der induktive Effekt lässt den Nabendynamo bei einer großen Geschwindigkeitsbandbreite einsetzbar bleiben.

Wie auch andere Dynamos kann der Dynohub Glühbirnen durchbrennen lassen, wenn man zu schnell fährt. Fahrradfahrer, die oft sehr schnell fahren, sollten deswegen auf der Hut sein, wenn sie kein modernes Lichtsystem mit Spannungsregulator einsetzen. Ein Nabendynamo erzeugt bei kleinen Laufrädern mehr Strom schon bei geringen Geschwindigkeiten und hier läuft man Gefahr sehr schnell viele Glühbirnen zu verbrennen. Moderene Nabendynamos sind für kleinere Laufräder ausgelegt und dieser Effekt tritt nicht mehr auf.

Ein Selbstbau-Gleichrichter

Sheldon Browns Artikel stammt aus der Jahrtausendwende. Im folgenden beschriebt er einen primitiven Spannungsregulator, den er ein paar Jahre früher gebaut hat. Wenn man diesen Nachbauen möchte, sollte man beachten, dass der vom Dynohub erzeugte Strom von 0,3 Ampere einen NiCad oder Nickel-Eisen-Hybrid Akku mit einer Kapazität von 10 Ah benötigt, um ein überladen in der "Tag"-Stellung zu vermeiden.

A nickel-cadmium or nickel-metal hydride battery can also over-discharge, suffering permanent damage as the stronger cells drive power backwards through the weaker ones ("polarity reversal"). A "smart" system shuts off charging when the battery is full, and stops discharge at a safe level. Modern generator systems with a stay-on when stopped ("standlight") feature use an LED with a capacitor for storage, to avoid all these issues.

Front- and side-facing reflectors are nearly useless when the bicycle is moving, but they are effective when it is stopped, and are another effective backup to a generator system -- John Allen]

I used to have a Dynohub on a tandem, and the bulb consumption was unacceptable. I solved the problem (and some others) by running the Dyno's output through a full-wave bridge rectifier and then hooking the DC in parallel with a 6 volt (5 x 1.2v cell) nickel cadmium battery. This not only provided light when I was stopped, the Dyno would re-charge the nicads, and, when we went so fast that the voltage rose above 6 volts, the low internal resistance of the nicads sucked up the excess, gaining a bit of extra charge and saving the bulb.

The rectified output of the Dynohub was always connected to the lights. There was no way to turn the light off while in motion. It would have been easy enough to rig a switch for that purpose, but I didn't see the need. The Dynohub has _very_ low drag. [The drag appears greater when the wheel is off the ground, because of original Dynohub had ow drag. The Schmidt generator has the lowest of all current models, and the new Dynohub, the highest. Still, you are unlikely to notice it while riding. -- John Allen]

I had a three way switch connecting the battery pack to the lights. In the "night" position, the nicads were in parallel with the rectified output of the Dynohub, as described above.

In the "day" position, the nicads were connected to the lights and Dyno through a diode (rectifier). This would allow the Dyno to charge the battery when it was going fast enough, but would not pass electricity the other way, so that the battery would not drain running the lights.

The "park" position completely disconnected the battery, because diodes are not perfect, and there is a slight drain that would discharge the nicads over a period of time.

Dynohubs are suitable for this type of set up because they do not use the bicycle frame as a ground. If you use a full-wave rectifier, you must keep the AC circuit separated from the DC circuit. Since most bicycle generator setups are made to use the frame as one of the wires in the circuit, this is a problem. To use full-wave rectification, either the generator or the lamps must be kept insulated from the frame. [The original] Dynohubs are already insulated from the frame, that is why they have two screw terminals and use twin-lead wiring. [This is true of some but not all new hub generators.] About rectifiers:

A "rectifier" is a device for converting AC (Alternating Current) into DC (Direct Current). The simplest kind of rectifier is a "diode", sort of a one-way valve for electricity. If you hook up a diode in series (as part of the circuit wire) with an AC source, it will only pass current half the time, when the AC is in its compatible direction. What comes through is pulsating DC. The problem with using a simple diode is that you are throwing away half of the electricity.

There is a simple circuit using four diodes, called a "bridge rectifier" that gets around this. It effectively flips the polarity around every half-cycle (an oversimplification, I know) and turns the AC into DC with negligible loss. You could solder four diodes together in the proper configuration, as I did, but these days you can just buy a ready-made "full-wave bridge rectifier". [Considering that the Dynohub operates at low voltages, the loss is significant when using silicon diodes -- 1.4 volts. If you use germanium diodes, it is only 0.4 volts. Fancier circuitry can get the loss much lower yet, but this is only a do-it-yourself project for a serious electronics hacker. -- John Allen.]

1950er Werbematerial

From a 1952 History of Sturmey Archer:

The Sturmey-Archer Dynohub is truly named:- "THE WORLD'S FINEST CYCLE LIGHT" dynohead The headlamp is of modern design and is the only cycle headlamp fitted with external screw-focusing. The front is securely fixed and is proof against rattle or detachment through vibration. A 3-inch diameter accurately made and highly polished parabolic reflector ensures a light of exceptional brilliance. The switch is placed below the lamp for weather protection and the connections are neatly made inside the lamp, thereby avoiding unsightly external terminals. The rear lamp is entirely sealed against moisture and its plastic red dome is visible at all angles from the rear, the bulb being of sufficient brilliance to be seen at a considerable distance. [The headlamp produced, a narrow but rather bright beam., though the nickel-plated reflector needed polishing occasionally. The taillamp has no focusing reflector and is feeble, even compared with more-modern ones that use the same0.6 watt incandescent bulb.-- John Allen]

The ultra - modern generator, which is covered by world patents, has no mechanical losses whatever and electrically is highly efficient, giving an output of 2 watts at 6 volts. [The bulbs used were rated at 1.8 watts -- John Allen] Using the existing wheel bearings and having no troublesome contact brushes it is entirely without mechanical friction or wearing parts, so that the effort to propel it is negligible. Being gearless it is absolutely silent, and its position in the hub protects it from damage. Voltage regulation is remarkably good, giving a good light at low speeds without an undue rise in voltage at the higher speeds, so guarding against the burning-out of bulbs. dynos

Wartung eines GH-6 Vorderrad-Dynohubs

Chris Hayes was kind enough to type up the instructions for dismantling and re-assembly of GH6 Dynohub from "The Secret is Fully Enclosed" the Sturmey Archer Catalogue for 1956.

[The Dynohub's bearing cups are integral with the hub shell, and can't be replaced. The bearing cones look like those for the AW hub, but they are not the same, as the axle diameter is smaller -- John Allen]

Zerlegen

Note: these instructions must be followed carefully. Separating the armature from the magnet will permanently weaken the magnet. -- John Allen]

Proceed as follows:

  1. Remove the dynamo-side locknut and washers, making a note of their arrangement so that they can be replaced in their original positions.
  2. Remove the four magnet-fixing nuts and lock washers from the back of the hub drum, and then remove the four magnet-fixing screws.
  3. Hold the wheel, with the dynamo downwards, just above the work-bench. A few light taps with a mallet on the end of the spindle will cause the dynamo unit to drop out complete.
  4. The magnet spacing ring can now be lifted out of the hub drum.
  5. Unless it is essential to do so, the armature and magnet should never be separated. If they are to be separated, a keeper ring is absolutely necessary, because the magnet will lose some of its magnetism unless there is always iron inside it. Even a moment's separation will cause loss of magnetism, and a spanner placed across the magnet is useless as a substitute for a keeper ring. To separate the magnet and the armature, hold the dynamo unit in the left hand, with the terminal plate against the palm. Then fit a keeper over the armature and lightly tap the keeper with the palm of the right hand. The magnet will slide off the armature and on to the keeper. At this stage it is wise to test the armature with a test meter. If there is no reading on the test meter there is a break in the winding. If a test meter is not available, a battery and bulb may be connected as shown in the diagram, and if the bulb does not light a break in the armature winding is indicated. A second test is to disconnect the lead from one of the armature terminals and touch the outer edges of the armature with the bare lead. If the bulb lights, this indicates a short circuit.
  6. Remove the cone locknut on the left-hand side and unscrew the left-hand cone.
  7. The channel-section dust cap is just a press-in fit and can be prised out with a wide screwdriver (to avoid damage). The ball cage may be lifted out for examination of the hub bearing surface. If a new ball retainer and balls have to be fitted, it is usually best to fit a new dust cap as well. Both hub cups are part of the hub shell and if either is worn a complete new shell must be fitted.
  8. The spindle may now be pulled out from the dynamo side,together with the right-hand cone. If the bearing surface is in good condition and the spindle threads are sound, there is no need to remove the cone.
  9. The ball cage may be lifted out for examination of the hub bearing surface.

SPECIAL NOTE. - GH6 hubs prior to 1952 had the adjusting cone on the dynamo side. This cone is extended to pass through the armature body and is flatted at the outer end to take (K428) notched adjuster washer, by means of which the cone may be turned. Dismantling instructions from 1 to 5 remain exactly the same as for the current model. For paragraph 6 read 'Unscrew the dynamo-side cone and lift the ball cage out of the hub shell. The spindle may now be pulled out from the other side, together with the fixed cone.' All further comments apply equally to all GH6 hubs.

Zusammenbau

Proceed as follows (see notes at end if hub was supplied before April 1952):

  1. Fit the ball cage with the ball-retainer ring facing outwards, into the cup on the left-hand (the smaller) end of the hub shell. If a new ball-retainer is being fitted, the dust cap also should be new.
  2. Fit the dust cap, with the channel facing outwards, and press it home (or tap lightly with a hammer).
  3. If the dynamo-side cone has been removed from the spindle, replace it (LB357AZ) on the spindle and screw it up tight against the shoulder on the spindle.
  4. Fit the ball cage, with the ball retainer ring facing outwards, into the cup on the dynamo-side of the hub shell.
  5. Insert the spindle into the hub shell from the dynamo-side.
  6. Fit the left-hand cone and adjust the hub bearings as described in The Fitting and Adjustment of Sturmey-Archer Hubs. (A correctly adjusted wheel must have a slight trace of play at the rim.)
  7. Fit the cone locknut and screw it up tight against the left-hand cone.
  8. If the magnet and armature have been separated, take the magnet and keeper ring in the left hand and, with the right hand, lay the armature alongside it.
  9. While holding the magnet with the chamfer facing outwards, push the armature and the keeper through so that the magnet slides from the keeper on to the armature.
  10. Fit the card disc (carrying patent numbers) inside the cover plate, with Its notches opposite the magnet notches.
  11. Fit the cover plate over the magnet, chamfer inwards, making sure that the four holes in the cover plate are in line with the notches in the card and the magnet.
  12. Fit the metal spacing ring into the hub shell.
  13. Fit the shim washer over the cone.
  14. Push the complete dynamo unit into the hub shell, making sure that the holes in the cover plate are in line with those in the hub shell.
  15. Fit the magnet fixing screws, washers and nuts.
  16. Fit the spacing cup, washer (if any) and dynamo cone locknut in the arrangement noted when dismantling.

Ersatzteile sind nicht mehr verfügbar

No replacement parts are available for GH6 Dynohubs. Please do not write to me asking for Dynohubs or parts; I don't have any, and I don't know where you can find any. [If you want to rebuild one, have a spare on hand for parts. -- John Allen]

Werbung:

Siehe auch

The Sturmey-Archer AG 3-speed rear Dynohub Reflectalite is a supplier of replacement lamps/bulbs for Dynohubs. Interested in making a Dynohub-based windmill generator? Click here for Gotwind.org!

Schmidt and Shimano Generator Hubs from Harris Cyclery Current Sturmey-Archer Dynohubs Peter White Cycles lighting pages NiceLite LED replacements for incandescent bulbs Intelligent Design Cycles, bicycle lighting and generators Compass Cycles bicycle lighting page English 3-Speeds Retro Raleighs Raleigh Parts Threading/Interchangeability Three-Speed Parts from Harris Cyclery Sturmey-Archer Hubs Sturmey-Archer Brochures 1935-38 You'll need a fast connection for this. Sturmey-Archer 1902-1952 Evolution of the Raleigh Sports The Raleigh Twenty Some of My Raleighs: Competition | International | Robin Hood | Superbe Roadster New! Sturmey-Archer Heritage Site Martin Hanczyc's roadster pages. Tony Hadland's Sturmey-Archer Pages Tony Hadland on the history of Raleigh



Quelle

Dieser Artikel basiert auf dem Artikel Dynohub von der Website Sheldon Browns. Originalautor des Artikels ist Sheldon Brown.



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