Caterpillar
A caterpillar chain (also known as a caterpillar chain , caterpillar or caterpillar belt ) is a central component of a chain drive . The closed chain is used to drive and steer tracked vehicles . It enables higher traction and, with a given vehicle mass, reduces the specific ground pressure with its large contact area . Since the weight is distributed over a larger area, sinking of the vehicle is reduced, especially on soft ground.
history
The invention of the crawler belt can be traced back to an idea by the English author and inventor Richard Lovell Edgeworth from around 1770. In 1826, the British engineer was George Cayley its universal railway ( Engl. Universal railway) patented.
In 1837 the Russian inventor Dmitri Sagrjaschski (Дмитрий Андреевич Загряжский) invented a carriage with mobile rails , which he patented in the same year. Due to a lack of financial resources, however, he was never able to build a working prototype, and his patent expired in 1839. A similar idea has the patent for the endless railway wheel ( Engl. Endless railway wheel) by British engineer James Boydell from 1846.
In 1901, Alvin Lombard invented the first commercially successful vehicle with a track chain as it is today, the Lombard Steam Log Hauler. On July 23, 1904 Richard Hornsby & Sons Ltd patented a similar system and installed it in a locomobile in 1905 . The chain links could only be angled in one direction, this resulted in a sort of rail (engl. Track ) on which then drove the vehicle. The patent was bought by the Holt Manufacturing Company . From 1906 the system was used by the British Army for artillery tractors. Due to the fact that the movement of the chain links of the soldiers as a caterpillar-movement (Engl. For caterpillar movement ) was referred to Holt secured the brand Caterpillar and his company eventually named in 1925 after a merger in Caterpillar Tractor Company to.
construction
Modern crawlers use modular links that form a closed chain. A basic distinction is made here between hinged chains and connector chains as well as between tensioned and non-tensioned chains.
use
Civil vehicles
Crawler tracks or caterpillar vehicles equipped with crawler tracks are used in numerous civil applications:
- Crawler tractor as a classic general area of application, v. a. (but not only) in agriculture and forestry , e.g. B. for wood harvesters :
- Snowmobiles and snow groomers : Particularly preferred here with slight rubber tracks :
- Mining , v. a. in opencast mining and especially in open-cast lignite mining with often gigantic bucket wheel excavators and conveyor bridges :
- Special vehicles: crawler tractors for launch ramps , such as that of the Kennedy Space Center Launch Complex 39 .
Military vehicles
An early use in military vehicles was the circular chain . Crawler drives are widely used in military vehicles. The caterpillar chain used there, the combat vehicle chain, is, in contrast to the chain used in construction machinery, a driving chain and not a pure transport chain and therefore differs considerably from this. The combat vehicle chain is designed for speed, greater smoothness and, to a certain extent, ergonomics with regard to the vehicle crew. This is not the case with the chains of construction machines, since the demands placed on them are of a completely different nature (better traction at lower speeds). According to the technical service regulations , crawler belt is also the official name of the Bundeswehr .
The number of links per chain in World War II tanks ranged from about 80 to 110 links. The crawler track of the Leopard 1 family consists of 88 chain links, each of which with the end connectors covers a length of 16 cm. This results in a total length of 14.08 meters. With use, the chain elongates and must be retightened. After a total elongation of 32 cm, the chain has reached the limit value and must be scrapped.
Types of chariot chains
The following types of chariot chains are used:
- Connector chains (tensioned chains)
- with solid rubber padding (chain pads are indispensable in the western sphere of influence to protect the streets)
- Combination chain with removable or exchangeable chain pads
- Hinge chains (tensioned or untensioned chains)
- Combination chain with removable or exchangeable chain pads
For both types of chain, battle chains can be kept, which - regardless of the ground to be driven on, simply because of the better grip - are only reinforced with steel bars.
The tensioned chains are referred to as "living chains", the unstretched chains as "dead chains".
Connector chain
The connector chain consists of
- the chain link with two rubber-mounted chain pins,
- the central guide tooth or chain guide tooth,
- the two end connectors,
- in the case of the combi chain, it also has one or two rubber pads.
The connector chain can be used with both front and rear drive. Their advantages are a high maximum speed, great smoothness, long service life and good lateral guidance on the drive (the chain is not thrown so quickly off-road). Disadvantages, in contrast to the hinge chain, are the more complex manufacturing process, the more complicated chain assembly due to the higher number of individual parts, and the manufacturing costs.
Another disadvantage is the possibility of padding in the drive wheel, for example on tough clay soil (but not with front-wheel drive). As a result, the chain lifts out of the guide and jumps off when the steering wheel is turned. To counteract this, the drive wheels were given the center guide ring, which acted on the center guide teeth and was intended to prevent them from migrating. However, this solution was not entirely satisfactory either, so that on the pioneer tank (which was extremely affected by chain throwing during work) a steel bar was attached diagonally over the drive wheel so that the chain could no longer wander.
Center guide tooth or chain guide tooth
The central guide or chain guide tooth is located on the inside of the chain; he provides her guidance and prevents her from falling away. A row of teeth in the middle is sufficient for trolleys with double rollers, which are common today. In the case of trolleys with simple rollers, for example the M3 , a double row of teeth on the outside of the rollers provides the necessary guidance. The guide teeth can be firmly connected to the chain link (one-piece chain link) or two chain links can also be connected in a clamp-like manner (two-part chain link).
End connector
The two end connectors are pushed onto the chain pins on the left and right and fixed. In addition, they are used to engage the drive sprocket.
Hinge chain
The hinged chain consists of:
- the chain link
- the chain pin
- the removable or replaceable chain pad.
When joining the chain links, the bolt is simply pushed through the fitting holes of the chain links and fixed on both sides. In the case of the hinge chains of the Soviet T-34 , the round-headed chain pins were only pushed in from the inside. At the rear of the vehicle pan there was a curved stripping plate that pushed the slipped bolts all the way back into the chain with each cycle of the chain.
A hinged chain can be used tensioned and untensioned.
The advantage of this chain lies in its simple design, the simple chain assembly and the relatively low procurement costs. Disadvantages are the high level of wear, the low level of driving comfort and the high risk of being thrown off-road. The hinged chain is used as a war chain or as a combination chain, with screw bolts generally being used as a fastening for the rubber cushions. In the case of the hinge chain, the central guide tooth is firmly connected to the chain link.
The high risk of being thrown off-road was counteracted by moving the drive wheel forward or by designing it as a disc-shaped gearwheel, which prevented the chain from being padded and thrown from it.
Connector chain with firm rubber padding
With the introduction of the M1 Combat Car in 1937, the United States Armed Forces already used a rubber-padded track. For this purpose, the one-piece support surface of the chain link was provided with a rubber plate (vulcanized or screwed on). This type of chain was also used on the M4 Sherman . The chain with solid rubber padding and split chain links was first used on the American M26 Pershing battle tank . The rubber base plate was provided with a rubber bar about 4 cm high. This was the chain with the highest running comfort, which was still used by the Bundeswehr up to the Leopard 1A1. One disadvantage of the firm rubber padding was that the chain could not hold on to snow-slick or icy roads, another was that it wore out quickly on rocky or very stony terrain. It then had to be completely replaced, even if the other limit values had not yet been reached.
Another disadvantage was that the grip in the terrain was not up to the demands of a combat mission and therefore a so-called combat chain had to be kept for each vehicle.
Combination chain or chain with replaceable chain pads
The combination chain was introduced because the previously common practice of two types of chain (solid rubber padding and war chain) had proven to be ineffective. The chain was now designed in such a way that it could be equipped with removable rubber pads and / or snow grippers . The chain pads are pushed in from the side and fixed with a spring nose (for example in the Leopard family) or with the help of threaded bolts and nuts (as in the armored personnel carrier short ).
In the German Wehrmacht , at least at the beginning of the Second World War, half-track vehicles (for example the Sd.Kfz. 251 armored personnel carrier ) were equipped with replaceable rubber pads.
See also
swell
- Tanks and other combat vehicles from 1916 to the present day. Buch und Zeit Verlagsgesellschaft, Cologne 1977.
- Technical service regulation of the Bundeswehr 2350 / 051-12 Dachs pioneer tank
- Paul-Werner Krapke: Leopard 2 its development and its performance. Gleiskette Leopard 2, Books on Demand GmbH, Norderstedt ISBN 3-8334-1425-1 , pp. 72, 73.
literature
- Wolfgang Merhof: Driving mechanics of tracked vehicles . Ed .: Ernst-Michael Hackbarth. 2015, ISBN 978-3-943207-13-2 ( link to PDF document [accessed March 11, 2020]).
- Peter Schwarzmann: Panzerketten - The tracks of the German tracked vehicles of the Second World War , Brandenburg publishing house, ISBN 978-3-943883-00-8
Web links
Individual evidence
- ↑ Lombard Steam Log Hauler (English)
- ↑ David Roberts: Tractor Pioneer Extraordinary (English)
- ↑ ASTRUM - Tank Tracks and Armor Whitepaper (English)
- ↑ 40 years of caterpillar tractors , raumfahrer.net
- ↑ Number of chain links per track on German tanks
- ^ Matthew Hughes, Chris Mann: T-34 tanks. Karl Müller Verlag, Erlangen.
Web links
- The drive of the T-72 ( Memento from January 30, 2009 in the Internet Archive )
- Track link types for VVSS Pictures and description of chain links for the M4 Sherman with VVSS chassis