Rod drive (railway)
The rod drive is a form of power transmission from the driving element such as the cylinder in steam-powered traction vehicles or the driving elements in electric or thermal traction vehicles.
With classic piston steam locomotives , the aim is to convert the back and forth movement of the piston in the cylinder into a rotary movement of the drive wheels.
In electric or thermal traction vehicles, the rod drive has the task of transmitting the tractive force from the spring-mounted traction motors to the drive wheel sets and of decoupling the two from one another in order to improve the running properties. Other possibilities for this are single-axle drives in the form of hollow shaft drives and, because of the smaller masses of the three-phase motors with the same power , more and more used - modified and spring-loaded on the bogie - spar bearing drives .
In addition to the power transmission, the rod drive was also used to distribute the tractive force to groups of driving wheel sets in order to prevent individual wheel sets from skidding (even in relatively modern vehicles such as e.g. B. SBB Ee 3/3 IV , SJ Dm3 ).
Explanation of terms
- Connecting rod
- The drive rod (CH: drive rod) connects the driving element such as the piston of a steam locomotive with the drive wheel set or a jackshaft. The back and forth movement is converted into a rotary movement.
In a locomotive , the rotary movement of the driving element, such as. B. the engine or a turbine in a more or less synchronous rotary movement of a drive wheel set or a jackshaft.
- Coupling rod
- The coupling rod can be attached to the crank pin of the drive shaft or the jackshaft and drives the coupling axles . Coupling rods can also be attached to the connecting rod.
The exception is the Winterthur helical rod drive, where the connecting rod is attached to the coupling rod (see below ).
- Driving wheel set or driving axle
- In the case of steam locomotives in particular, the wheel set primarily driven by the drive rods is referred to as the drive wheel set, also known as the drive wheel set in Switzerland. In three- and four-cylinder machines there are also two-axis drives, where outer and inner cylinders act on different wheel sets. The designation is also used in diesel and electric locomotives with rod drive for the wheelset, which is connected directly to the jackshaft or comparable equipment via the connecting rods. A drive wheel set is usually noticeable because of the significantly more massive and sometimes longer drive pins that have to transmit the entire drive power. The balancing masses in the wheel spiders are also larger because of the mass of the massive connecting rods that also have to be balanced.
- Coupled wheel set or coupled axle
- Coupled wheel sets are those wheel sets that are driven by the drive wheel set via the coupling rods. The drive axle can also be a jackshaft.
- Jackshaft
- Additional drive shaft mounted in the frame or compensating or rod guide shaft that does not have any wheel disks with track contact. A jackshaft usually belongs to the sprung mass
- Countershaft
- The countershaft transfers the power of the drive motor or motors to the drive rod. In most cases, a gear (= countershaft ) arranged between the countershaft and the travel motor has the task of reducing the speed of the high-speed motors.
- Mass balancing
- See: mass balancing . In rod-driven diesel and electric locomotives with only revolving movement of the engine parts, mass balancing can be achieved almost completely by balancing weights on shafts and wheels, whereas in steam locomotives with two-cylinder engines and the reciprocating masses of pistons and piston rods, it is only possible to a certain extent.
Crank offset
A disadvantage of the rod drive is that drive rods and coupling rods can only transmit forces in their longitudinal direction and in a position outside the dead center position . In the case of steam locomotives, there is also the fact that a piston steam engine cannot start up in a defined direction from a position close to dead center. This is why the wheelsets as well as the dummy, countershaft and motor shafts have a crank offset of typically 90 ° between the two sides of the vehicle. This means that one drive side is always able to absorb and transmit the drive forces, because even when one side is in the dead center position, the opposite crank is inevitably close to the kinematically favorable right angle . This offset is only deviated from in the case of three-cylinder steam locomotives. There it is about 120 ° because of the desired uniform torque curve, whereby there are mostly deviations of a few degrees because of the inner cylinder often lying at a different angle to the drive axis.
Steam locomotives and steam railcars
With rare exceptions, drive rods and coupling rods are always used for power transmission in steam locomotives, the rod drive is practically standard here. For more details, see Steam Locomotive . The development of single-axle drives came too late for steam locomotives; only a few prototypes were equipped with them.
Electric and thermal locomotives and railcars
The first larger locomotives powered by diesel or electric motors usually had a linkage, usually one or more drive and coupling rods , to transmit power from the traction motor to the drive wheel sets and to compensate for the spring play . With the advent of hydraulic and electrical power transmissions, the locomotives with rod drives were also referred to as rod locomotives to distinguish them from the concept .
Helical rod drives
Helical rod drive with a high motor
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The first powerful electric locomotives (especially with alternating current ) had slow-running repulsion motors . Due to their size, these took up almost the entire cross-section of the locomotive body . For the transmission of the driving force, drive rods arranged at an angle of approximately 45 ° were often attached. But there were also locomotives with almost vertical connecting rods.
In most cases, the connecting rods transmitted the force to a jackshaft , from which the force was transmitted to the neighboring wheel sets by means of coupling rods . Examples are the DR series E 52 or the Ge 2/4 (before conversion) of the RhB .
Flat helical rod drive
This drive is also a drive with two fixed points, but they are almost completely horizontal. The countershaft drives the drive axle without an intermediate element. Examples are Fb 2x2 / 3 11302 of the SBB , Be 4/6 12303-12342 of the SBB and the steam turbine locomotive DR class T 18.10 .
Winterthur helical rod drive
The Winterthur helical rod drive or Winterthur helical rod drive is a simple drive. The drive is based on a countershaft that is slightly upwards. This drives a simple drive rod that is connected to a triangular coupling rod. The entire geometry of the drive can be created vertically in one plane. The arrangement in one plane means that the connecting rods cannot be articulated to the crank pin of the primary drive wheel set, but eccentrically to the triangular coupling rods, which leads to additional mechanical stresses on the coupling rod and the crank pins of the wheel sets driven by the coupling rod. This is manifested by a noise in the turning points. Nonetheless, because of its simplicity, the drive was the most popular rod drive for electric locomotives.
A very early example was the BLS Ce 6/6 121 , a unique piece from 1910 . It had a very high installed power of 1470 kW (2000 hp) for the time. Further examples are SBB Ce 6/8 I , SBB Ce 6/8 III , various SBB Ee 3/3 , RhB Ge 6/6 I or DR series E 60 , E 63 , E 75 , E 77 and E 91 .
Slot drive rods
A slot drive rod connects three crank pins. On the outer crank pin, the rod, which is generally triangular, is mounted immovably. In the ideal position of the two outer crank pins, the middle drive pin is mounted vertically displaceably in a slot-shaped recess to compensate for the spring play. In addition to small vertical forces transmitted by the friction in the crank pin bearing of the slot or by an inclined position of the slot depending on the track position, only horizontal forces are transmitted. The disadvantage of the slotted rod is its larger volume and thus its greater mass compared to a drive rod supported at two points. Another disadvantage is the higher maintenance costs.
Due to the voluminous design of the drive rod, coupling rods for other driven axles are always hinged to the rod and not to the respective crank pin.
Ideally, the coupling rod is arranged vertically on the ideal position of the crank pin (that is, in the position with a level track position) of the axis driven by the slot drive rod.
Slot drive rod on two sets of drive wheels
In this type, the crank pins of two drive wheel sets take over the function of the fixed bearings. The slot-shaped bearing is transferred to the crank pin of the countershaft. Depending on the track position, this results in a deflection from the vertical position of the slot with respect to the drive, which is fixedly mounted in the frame. This type of drive was z. B. used in the Prussian EG 511 to EG 537 , the Bavarian EG 2 , in the prototype Fb 2x2 / 3 11301 of the SBB or in the Ce 4/6 of the BLS and some railcars such as the Prussian ET 831 to ET 842 .
Slot drive rod on drive wheel set and jackshaft
This type was used in the Ce 6/8 II locomotive of the SBB . One fixed point was taken over by the countershaft, the other by a jackshaft, which was initially even rotatable horizontally with respect to the frame. In this application, too, the vertical position of the slot in relation to the track was almost always guaranteed. This drive was the industry's answer to the unsatisfactory kinematic behavior of the Winterthur helical rod drive assumed by the SBB , which was used in the Ce 6/8 I of the SBB . In fact , this meant that before the Ce 6/8 I went into operation, these doubts were already there. In fact, this type of drive turned out to be very smooth-running.
Slot drive rod on a drive axis
Since the motors and countershafts fixedly mounted in the locomotive frame drive both fixed crank pins of the drive rod, the vertical position of the slot with respect to the locomotive is always vertical here.
This type was used in locomotives that had two countershafts in the same drive unit. The slot is here at the crank pin of the drive axle.
An early example was the Fb 5/7 (later renamed Be 5/7) of the BLS from 1913 . The installed capacity of 1840, which was large for the time kW (~ 2500 The horsepower was distributed over two motors, which - as described above - drove two countershafts via pinions and large gears, which jointly drove the middle drive gear set through an open, forged triangular drive rod. The vibrations that occurred in the process led to these connecting rods bending over and over again. Only the use of a reinforced triangular frame created a solution.
In the case of motor vehicles for higher speeds, the pinions on the drive motor shafts were also cushioned.
Other examples are the Fb locomotives 3/5 11201 and Ae 3/6 II of the SBB.
Kandó drive
The patented Kandó drive , which went back to the Ganz company and its designer Kálmán Kandó , was a similar construction, but without a slotted crank.
To compensate for the height between the traction motors and axles, Kandó used a link frame connected to the jackshafts of the motors; the connection to the drive wheels was made by the so-called Kando triangle . The advantage of this design was that the copious lubrication of the backdrop could be minimized.
The system for the first time in the applied three-phase - electric locomotives of the FS , Series E 552 . The company Ganz carried out the electrification work for the electrification of the Northern Italian Ferrovia Alta Valtellina . In Hungary this system appeared later due to the delayed completion of the MÁV series V50 . Other well-known locomotives with this drive are the MÁV series V40 and the MÁV series V60 .
Articulated drive according to Bianchi
With the Bianchi articulated drive, a lever system also provided height compensation between the motor and drive axles. Instead of the Kandó triangle, the connection between the lever system and the drive axis consisted of a lever system made up of three articulated levers. These three levers encompassed the driving pin of the drive wheel with six pressure points and prevented the introduction of vertical force components. Here, too, the lubrication could be significantly reduced compared to a drive with a gate.
This system was used for the first time in 1927 in the electric three-phase locomotives of the FS , class E 554 , which were produced in large numbers. The rod drive developed by Giuseppe Bianchi was not only intended for the slow-moving freight locomotives, which were approved for only 50 km / h, but also the express train locomotives of the E 432 series , which were approved for a top speed of 100 km / h, had this multi-part drive design.
This gear construction has reliably performed its tasks for more than four decades. It only ended in 1976 with the end of the three-phase system at Ferrovia Alta Valtellina in Northern Italy .
swell
- ↑ Notes: the term ... locomotive used below also applies to railcars . The term locomotive is used below for traction vehicles in which one rotary movement is converted into another rotary movement. In this case, this also applies to a thermal drive element that does not have to convert a one-dimensional movement directly into a rotary movement (classic steam locomotive).
- ^ Photo of the FS E552 ( Memento from December 20, 2005 in the Internet Archive )
- ^ Photo of a model of the FS E.552
- ↑ Sketch of the FS E552 ( Memento from January 26, 2017 in the Internet Archive )
- Hans Schneeberger: The electric and diesel traction vehicles of the SBB, Volume I: years of construction 1904–1955; Minirex AG, Lucerne; 1995; ISBN 3-907014-07-3 .
literature
- Claude Jeanmaire: The electric and diesel locomotives of the Swiss railways, The locomotives of the Swiss Federal Railways (SBB)
- Wolfgang Messerschmidt: Locomotive technology in the picture - steam, diesel and electric locomotives . Motorbuchverlag Stuttgart, 1991 ISBN 3-613-01384-3 ; Pp. 71-74.
