Tow hitch

A trailer hitch or a towing device is a device with which a vehicle - for example, cars, trucks or bicycle ( see bike trailer ) - is connected to a trailer. Depending on the type of the tractor and the trailer you will find four types:

• The bolt coupling, common in the agriculture and forestry
• The ball coupling, common in older cars and bicycle trailers with high pedestrian
• Foot clutch for trucks and tractors
• The fifth wheel for tractor-trailers.

Less common are types in which coupling hooks are used with corresponding eyes. The consistently applied in the European Union, arrangements are summarized in the EC Directive 94/20 of 30 May 1994.

• 3.1 tractor with fifth wheel 3.1.1 D- value

• 3.2.1 Dc - value
• 3.2.2 V- value

• 6.1 General provisions
• 6.2 Notes to the towing 6.2.1 Permissible total weight of the train

History

First detachable towbars are known from 1904, a " trailer industry," but was only from 1912 In the 1920s, different coupling systems were used. ; Only in 1925 were counted 17 different bolt couplings. In agriculture, forestry and construction site work simple bolt couplings are still used for unbraked trailers.

The manufacturer Rockinger 1927 developed an automatic jaw coupling, for which he received a U.S. patent in 1932. A similar product has been producing in 1923 the manufacturer from Krefeld ring spring for railway applications. These systems of the automatic closing process implemented worldwide by the commercial vehicle sector.

For the semi-trailer with a fifth wheel king pin is required. The first patents were issued in 1932 a detachable trailer, but already in the 1920s, was presented with the " Economist large-area car", the first tractor.

Detachable ball - snap closures were offered in the early 1930s when motorcycle with sidecar. Franz Knöbel received on March 14, 1934, a patent on the ball coupling. The manufacturer Westfalia gained worldwide notoriety with this invention. The then diameter of the sphere of 50 mm is still the norm today. For light trailers (without / with overrun brake ) the ball coupling is today's standard clutch. The not " automatic " ball coupling is allowed for trailer in agriculture and forestry, as well as for trailer weights below 3,500 kg.

Mulberry clutch

Fifth wheel

Ball coupling

Car

For cars, the ball head coupling is employed. When towing hitch is a bracket with a standardized ball of 50 mm diameter. The trailer is as a counterpart to the drawbar a ball socket at back closure. It can be opened by lifting a lever. Are both coupled together, the ball socket is rotatably mounted on the sphere and is secured against lifting off. This may be followed by the tractor articulated trailer. Furthermore, the tow bar can serve as a bike carrier, for example as a basis for other transportation devices. An important criterion for the load capacity is the permissible maximum load, which is usually at 75 kg.

D- value

The fatigue strength against force effects by the driving operation between the tractor and the trailer at the intermediate trailer hitch design is called D- value and given in kilo Newton ( kN). The value is given in accordance with the nameplate. This value of a given trailer hitch is together with the mass of the towing vehicle as well as a possibly specified in the registration papers or on the nameplate team - total mass, the basis for calculating the permissible trailer load. The D-value is uniquely determined on the basis of an appropriate design and tested and remains unchangeable.

With the introduction of the D- value is omitted on the type plate of the trailer hitch until then usual indication of the trailer weight (GA ) and the maximum authorized mass ( GF). To ensure that only the D value and the allowable bearing load is given. The total weight of the towing vehicle and the trailer load variable values ​​, bearing in mind that the chassis manufacturers and their peripherals limit the total weight of a train.

The required D value according to Directive 94/20/EC or according to ECE -R 55 can be constructed pursuant to

Determine.

The D value of the trailer coupling must always be above the required D- value. Calculation of the maximum permissible trailer load on a trailer coupling with given D value according to Directive 94/20/EC

The trailer load should be below the permissible trailer load.

Detachable towbars

In addition to the rigid towbars there are also versions with detachable ball neck, then this interferes not when operating without a trailer. A detachable ball neck is according to EU Directive EC Directive 94/20 of 30 May 1994, Annex VII, Section 2.1.4 then mandatory equipment as soon as the flag or the space provided space is covered by the ball neck.

Depending on the direction from which the removable part is attached to the vehicle, vertical, inclined and horizontal variants are distinguished. These are also usually lockable, so that they can not accidentally be removed by unauthorized loosen itself or by external influences as well.

In some embodiments, still stands out while off- ball -socket device under the bumper, while others can be the socket pivot upward. The view of the rear of the vehicle is no longer disturbed by the recordings. There are also devices with electrically retractable trailer hitch.

In some states, such as in Slovakia, it is mandatory that each removable clutch is actually remove when not in use, although this is not explicitly named in accordance with EC Directive 94/20. Background of this provision lies rather in the general duty to minimize damages of each individual. The above trailer couplings provide a latent danger to pedestrians and cause injury when passing through of parking spaces represents the Slovak regulation is therefore redundant.

Impact protection

The use of an impact protection (APS ) of rubber reduces the risk of damage to the towing vehicle during coupling.

Electrical

Still belongs to the complete coupling an outlet for the vehicle lighting of the trailer, as the lights must be lit with those of the towing vehicle in accordance with the Road Traffic Act. There are standard 7-pin connectors according to ISO 1724 or 13-pin connectors according to ISO 11446th The 13-pin Jaeger system was introduced in the late 1980s. There are adapters to connect the two mutually incompatible mechanical systems.

Mechanical design

The 7-pin plug connection to ISO 1724 as well as the 7 6 pin connector according to MultiCon be disengaged by pressure in the direction of a contact pin and by train. As protection against loosening of the rotating spring loaded socket lid, whose molded prongs engage behind the plug is. The 7-pin contacts are large format with slotted pins. The housing can be made of glass fiber reinforced plastic and in die cast metal.

The 13-pin plug connection to ISO 11446 is, however, a plug and unplug a quarter turn by a bayonet lock. As protection against loosening serves as the rotating spring loaded socket lid, but without prongs. The cover can be opened here on the molded Ronde of the plug and prevents twisting. The housing consists of glass fiber reinforced plastic.

Trailer sockets and pin assignment

The assignment of individual contacts is covered by the standards and must not be changed (except for the not occupied at the 13-pin connectors). The assignment of the contacts 1-7 are valid for 7-pin as well as 13-pin connectors. The cable colors are observed in accordance with Directive if possible. This can have the consequence that in some cases may also exist other colors or other use of available colors.

Partly different:

There are three ways in which the electronics detect in the towing vehicle, a trailer is connected:

- In the socket, a switch that turns off in the towing vehicle, the line of the rear fog lamp, disadvantage: A 13- to -7 -pin adapter is already recognized as infected Trailer

- Contact 12 is to be connected as a pendant 11446 self recognition in the trailer with contact 3 according to ISO, a control unit evaluates these

- A control unit in the tractor measures when the ignition, whether connected to the terminals of the socket bulbs are (filament cold - monitoring). Are indicators, reversing lights and rear fog lights and white reverse light at the socket is connected, the control unit reports towing a trailer to the CAN bus. The disadvantage is that mandatory rear lights with bulbs should be used, because LEDs require resistors in parallel.

The trailer control unit or relay switches off the fog lamp and, where appropriate, the reversing sensors of the towing vehicle when the trailer is coupled. The turn of the trailer shall be monitored either by a special flasher relay or the trailer control unit.

The ground contact No. 3 is exclusively responsible for the taillights and must not be connected to the other ground connections on the trailer.

Should the rest of the contact assignment differ in older vehicles, a repair is recommended.

The continuous voltage or the load line as far as could drain the battery of the tractor that the engine from starting is not possible unless there is a specific cut-off relay used.

Adapter

To use seven pin connectors to thirteen pin connectors, adapters are commercially available. It is sufficient, has to connect the two connectors when the same occupied systems contacts 1-7. In the 13 -pin connector, or adapter 7 - pin socket of the trailer detection Contact No. 12 may be connected to the ground contact number 3. This can be achieved by disabling the built on the towing vehicle distance warning when reversing and fog light shot. These adapters are also called " short adapter ".

Truck

On the truck there is a so-called coupling mouth with a bolt. The counterpart to the drawbar of the trailer coupling means eye or eyelet. The drawbar is inserted into the coupling jaw, the bolt will automatically lock and the clutch is connected. By pressing turning the operating lever ( right above the mouth ), the bolt may be snapped highly leveraged without tools by hand and eventually lifted in order to uncouple or in the sequence.

In addition, again comes the plug for the electrical supply. In addition, the connections for the brake are required. There is an older introductory and a more modern dual-line brake system.

The older towbars were not automatic, but it was simply a bolt from the top through the mouth and through the eyelet inserted and secured down with a cotter pin. In many cases, this type is still used on tractors or in the front of the truck.

Trucks have often for reasons of legal rules about towing devices also forward a regular hitch so you can tow it smoother. In addition, it is easier to maneuver a trailer if it is attached directly to the steering axle of the truck. The front coupling is often covered by a cover.

In the truck there are two different kinds of trailers. It is between supporters with height movable drawbar that do not transmit vertical forces, and rigid followers that transmit vertical forces, distinguished. First mentioned are generally called turntable trailers and the latter as central axle or axle trailer.

Tractor with fifth wheel

D- value

The D -value at turntable is just like the car in the 94/20/EC or ECE - R 55 is calculated as follows:

Abbreviations:

The D value of the coupling must be greater than or equal to the calculated value for the train combination.

Tractor with center-

Dc - value

The Dc value is the pendant to the D - value for center. The Dc value is in accordance with the 94/20/EC or ECE - R 55

Determined.

The Dc value of the coupling must be greater than or equal to the calculated value for the train combination.

V value

The V value is the theoretical reference value of the vertical force amplitude exerted by the center- with a technically permissible maximum mass exceeding 3.5 tonnes on the clutch. The V value is used in the dynamic tests for determination of the vertical forces. It is usually given in kilo Newton.

The V value is the theoretical vertical drawbar force exerted by the center- with a technically permissible maximum mass exceeding 3.5 tonnes on the clutch. The V value is used in the dynamic tests for determination of the vertical forces. Calculates the value in accordance with ECE R55:

Note: ( a value of less than 1.0 Makes then is to use the value 1.0. )

The V value of the coupling must be greater than or equal to the calculated V- value.

Towing

With the tow truck can via a towbar other commercial vehicles (trucks, buses, etc. ) towing, the tow bar at the two ends each having an eyelet. At the front end of the bolt locks into the hitch of the towing truck, the rear end of the tow bar is connected to a towing device of the defective commercial vehicle.

NATO clutch

Another form of trailer hitch is the hook or NATO clutch. This type of trailer hitches are prohibited in the civilian public roads since the late 1970s in Austria. In Germany, the auto-closing hook couplings, which were introduced in the 1970s, fully approvable because they have a national approval mark consisting of wavy line and manufacturer number. Due to the larger diameter of the hook compared to bolt the clutch only civilian trailer can be attached with an appropriate towing eye. Keep it constantly rumors about a ban on the pintle hook. However, these are mainly based on two points that have been long since improved. In the early days, even during the Second World War, the towing eye was bent from a pipe that broke at high loads. Modern drawbar eyes are massive forgings of steel. Also, prior hook couplings were not automatically closing, which precluded their use on public roads. The Americans have a good ten years later separated from the pintle hook. However, in the military, this type finds further use. One reason for this is the availability in the field. By construction, it is possible to still pull a trailer in difficult terrain.

Bikes

In two-wheelers, there are two different variants to couple a trailer. Firstly, a system similar to the car with a smaller (Ø = 25 mm) coupling ball on the towing vehicle. This is mounted on bicycles usually directly behind or under the saddle, with mopeds or scooters to the rear rack. With this system, single-axis handcarts can be coupled with high drawbar. A hemispherical shell only to the drawbar is thereby pressed by a pressing block with a recess on the hitch ball. Other systems work with eyelet and pin.

Increasingly for bicycle trailer is a coupling system distribution, at which the clutch sits (usually left) side near the rear axle of the towing vehicle, either with a side stand on chains and side strut ( frame tubes ) or with the axle nut clamped to the axis. The clutch can be re- articulated by a ball. If it is, however, more form-fitting, running obliquely backwards tiller has forward integrated into a relatively rigid helical spring as the joint. By shaft height in less than half as high initiation of " force of inertia " of the trailer when braking (only ) of the towing bicycle is this less " dug " ( relief of the rear axle). Also Supporter rolling forces transverse to the direction act on such shorter lever less on the bike. Both effects it can drive more safely, good standing and pedaling. However, driving on narrow right-handers is hampered because the rear abuts the drawbar.

Wheel trailer, whether for bicycles or motorized vehicles need some sort of hitch and shaft, the torsion- connect the trailer to the towing vehicle and thus with this - maintains - with respect to its longitudinal axis. However, coupling and drawbar have to be articulated for tops and cornering two kink directions. To form two pins ( approximately ) in the extension of a rear wheel axle of the bicycle (dotted ) the horizontal pivot axis. Front bears the trailer a joint with also about 15 cm long, vertical pivot axis. Both form two edges of a stretched tetrahedron whose four more edges by four slender tubes of a three-dimensional tongue ( usually foldable and easily degradable) are formed. Narrow, low-profile design allows for loading and saddle, the one-wheeled trailer tilts with in each corner and follows exactly in the track.

Special Vehicles

Historically other hitch systems for special vehicles are known. It was used by the Wehrmacht for light trailer loads of swank unit hooks on motorcycle sidecars as Zündapp KS 750 and Kettenkrädern. Also the connection of multiple trailer was used in a similar way for the infantry carts IF8 with teams of horses. At 1.5 - ton truck such as Steyr 1500 A partially a swank hook was used. For omnibus trailer a backlash-free double-bolt coupling was used.

Terms of Use

General provisions

In Germany, a coupling device is on multilane motor vehicles prescribed and regulated along with trailer couplings in § 43 traffic regulations " means for connection of vehicles " (excerpt):

• Couplings must act automatically
• However, non -automatic trailer couplings are allowed

• Motorway vehicles with more than one axle must have a front towing device

Information for trailer operation

Permissible total weight of the train

In vehicle title / voucher may under 33 (Remarks ) the term ' ZUL.GES.-GEW.D. TRAIN MAX ......... KG be noted ". This makes the maximum total weight of the train ( combination vehicle and trailer) is defined. This limitation has to be considered by the vehicle owner / leader.

Regulatory Information

In Germany you have a subsequently mounted trailer hitch that does not have EU approval, are reviewed and approved by an officially recognized expert.

Is the certificate part 1 under item 22 ( Remarks and Exceptions ) ww. AHK recorded according EGTG / ABE, ( official abbreviation for optional trailer hitch according to EC type-approval or national type approval ) the vehicle is intended for the cultivation of a decrease free trailer coupling with EU approval.

The conditions for a decrease free cultivation of the AHK according to § 19 paragraph 3 traffic regulations are detailed in Germany as follows:

• The tow bar has received EU approval feature ( mark with e beginning ). The E-mark indicates that the corresponding technical component is approved within the EU, a further examination of the cultivation is not then required.

• Facilities without EU approval or E-mark must be tested according to cultivation by a monitoring organization ( UEO how FKÜ, CTW, GTÜ ) or technical inspection (TP as DEKRA or safety ). Here, the correct installation of parts and compliance so that any conditions attached to a certificate of conformity (TGA ) is controlled and after passing the examination created.

• If the device has not been registered with the help of the general operating, the EC type-approval, the certificate of conformity by the approval authorities in the vehicle documents, the document during the driving or driving the car or Krads must be carried.
• The permissible trailer load should be assessed against the so-called D- value of the trailer hitch.

In Austria, the approval is dependent on whether a device is already registered in the homologation certificate. Only if none is available, it must be reviewed and registered by the review panel of the respective state government.