Whippletree (mechanism)
（重定向自Leader bar）
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 direction to the tips. Several whippletrees may be used in series to distribute the force further, such as to simulate pressure over an area as when applying loading to test plane wings. Whippletrees may be used either in compression or tension. Whippletrees were also used for subtraction and addition calculations in mechanical computers. Tension whippletrees are used in artful hung mobiles.
![A set of whippletrees or leader-bars for the two leaders of a four-horse team.](/Images/godic/202501/23/Leader_bars3548.jpg")
![A single horse ploughing – the whippletree is the horizontal wooden bar just in front of the plough.](/Images/godic/202501/23/Schnitterfest3548.JPG")
![A set of whippletrees for a three-animal team.](/Images/godic/202501/23/Triple_whippletree_set.svg3548.png")
![A standard automobile windscreen wiper uses whippletrees to distribute the force of the wiper arm evenly across the blade.](/Images/godic/202501/23/Heckscheibenwischer_kl3548.jpg")