Tow hitch: Difference between revisions

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A tow hitch (or tow bar or recovery point) is a device attached to the chassis of a vehicle for towing or a towbar to an aircraft nose gear, or paired main gears.

It can take the form of a tow-ball to allow swivelling and articulation of a trailer, or a tow pin and jaw with a trailer loop - often used for large or agricultural vehicles where slack in the pivot pin allows the same movements. Another category is the towing pintle used on military vehicles worldwide.

In the US the vehicle attachment is known as the tow-hitch. It is the receiver which bolts to the chassis of the vehicle. In the US there are a few common classes: I, II, III and IV that are defined by the SAE. Class I (to 2000 lbs / 909.1 kg) and II (to 3500 lbs / 1591 kg) are for light loads, and the receiver is a square hole 1.25 inch / 31.7 mm x 1.25 inch. Class III (to 5000 lbs / 2272.7 kg) and IV (to 10,000 lbs / 4545.5 kg) can accommodate much larger trailers such as campers, boats, etc. A Class III/IV receiver is 2 inches / 50.1 mm square and in some cases 2 1/2inch / 63.5 mm.

The trailer tongue [US] or coupling [non US] slips over a tow-ball. Tow-balls come in various sizes (1 7/8 in / 47.6 mm, 50 mm / 1.97 in, 2 in / 50.1 mm and 2 5/16 in / 58.7 mm), depending on the load they carry and the country of operation.

Outside the US the vehicle mounting for the tow-ball is called the tow-bracket. The mounting points for all recent passenger vehicles are defined by the vehicle manufacturer and the tow-bracket manufacturer must use these mount points and prove the efficacy of their bracket for each vehicle by a full rig-based fatigue test.

In order to tow safely the correct combination of vehicle and trailer must be combined with correct loading horizontally and vertically on the tow-ball. Advice should be taken [see references] to avoid problems.

In North America the ball attaches to a ballmount. The ballmount must match the US hitch class. The ballmount is a rectangular bar that fits into a receiver attached to the vehicle. It may drop down to get the ball closer to the ground so the trailer will ride level.

In the European Union, towbars must be a type approved to European Union directive 94/20/EC to be fitted to automobiles first registered on or after 1st August 1998.

The ISO standard tow-ball is 50mm in diameter and conforms to a standard BS AU 113b. The ISO standard has been adopted in most of the world outside North America.

There are two main categories of ISO tow-ball - the flange fitting and the swan-neck which has an extended neck fitting into the tow-bracket. Swan-neck tow-balls are often removable to avoid the inconvenience of a tow-ball protruding from the vehicle when not required. Some manufacturers are introducing retractable tow-balls as an option.

Across Europe around 25% of the vehicle park have tow-balls fitted - but there are distinct regional variations with Benelux and Scandinavia having 70 to 90% of vehicles with tow-balls.

Trailer Tow hitch

Cars can include trailer tow hitch with a removable tow ball.

Weight Distributing Hitch

A weight distributing hitch is a "load leveling" hitch. It is a hitch setup mounted on the tow vehicle that uses spring bars under tension to distribute part of the trailer's hitch weight to the towing vehicle's front axle. It can help reduce trailer sway and hop. Trailer hop can jerk the tow vehicle. Trailer sway is sometimes called "fish tailing". At high speeds, trailer sway can become dangerous. Most vehicle manufactures will only allow a maximum trailer capacity of 5000#'s and 500#'s of tongue weight without using a weight distributing hitch. Tow vehicles often have square receiver sockets to accept weight distributing hitches.

Lunette Ring

A Lunette ring is a type of trailer hitch that works in combination with a pintle hook on the tow vehicle. A pintle hook and lunette ring makes a more secure coupling, desirable on rough terrain, compared to ball-type trailer hitches.

References

External links

Longhorn Motors, Ltd. Definitions of North American towing terms

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+[[Image:Kombi anhængertræk med stik.JPG|Towball on car|thumb]]
 A '''tow hitch''' (or '''tow bar''' or '''recovery point''') is a device attached to the [[chassis]] of a vehicle for [[towing]] or a towbar to an [[aircraft]] nose gear, or paired main gears.