A swingletree or singletree (North America) is a wooden or metal bar used to balance the pull of a draught horse

Draft horse

A draft horse , draught horse or dray horse , less often called a work horse or heavy horse, is a large horse bred for hard, heavy tasks such as ploughing and farm labour...

 or other draught animal when pulling a vehicle

Horse-drawn vehicle

A horse-drawn vehicle is a mechanized piece of equipment pulled by one horse or by a team of horses. These vehicles typically had two or four wheels and were used to carry passengers and/or a load...

. It is a kind of whippletree

Whippletree (mechanism)

A whippletree or whiffletree is a mechanism to distribute force evenly through linkages. The mechanism may also be referred to as an equalizer, leader bar or double tree. It consists of a bar pivoted at or near the centre, with force applied from one direction to the pivot, and from the other...

, and the term is also used sometimes for other whippletrees.

It is a horizontal bar, attached or suspended in the middle, and able to hinge

Hinge

A hinge is a type of bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation. Hinges may be made of flexible material or of moving components...

 fore-and-aft in a horizontal plane. The traces

Trace (tack)

In transport, a trace is one of two, or more, straps, ropes or chains by which a carriage or wagon, or the like, is drawn by a harness horse or other draught animal. The once popular idiom: "kick over the traces" comes from a frisky animal kicking one or both feet outside a trace...

 (the straps by which the animal pulls) attach to its ends, and the vehicle is pulled from its middle.

The centre of the swingletree may be bolted directly to the body of the vehicle, this bolt pulling the vehicle along. Alternatively it may hang loosely by a chain or strap from the body of the vehicle, and in this case the pull is taken by chains from the centre of the bar to the ends of the axle.

The action of a swingletree is to balance the pull from alternate shoulders as the animal walks. It is used especially when the animal is in a breastcollar harness, because this can easily rub the shoulders if the pull is uneven. It is needed less for an animal in a horse collar

Horse collar

A horse collar is a part of a horse harness device used to distribute load around a horse's neck and shoulders when pulling a wagon or plow. The collar often supports and pads a pair of curved metal or wood pieces, called hames, to which the traces of the harness are attached...

, as the pull does not pass over the shoulders in the same way. For this reason heavier vehicles may have no swingletree, as they are normally pulled with a horse collar.

See also

• Horse collar
  Horse collar
  A horse collar is a part of a horse harness device used to distribute load around a horse's neck and shoulders when pulling a wagon or plow. The collar often supports and pads a pair of curved metal or wood pieces, called hames, to which the traces of the harness are attached...
  
  
• Breastcollar
• Horse-drawn vehicles
• Horse harness
  Horse harness
  A horse harness is a type of horse tack that allows a horse or other equine to pull various horse-drawn vehicles such as a carriage, wagon or sleigh. Harnesses may also be used to hitch animals to other loads such as a plow or canal boat....
  
  
• Draft horse
  Draft horse
  A draft horse , draught horse or dray horse , less often called a work horse or heavy horse, is a large horse bred for hard, heavy tasks such as ploughing and farm labour...
  
  
• Draught animal