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200px, A weigh lock on the Lehigh Canal around 1873 A weigh lock is a specialized
canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface f ...
lock Lock(s) may refer to: Common meanings *Lock and key, a mechanical device used to secure items of importance *Lock (water navigation), a device for boats to transit between different levels of water, as in a canal Arts and entertainment * ''Lock ...
designed to determine the weight of
barge Barge nowadays generally refers to a flat-bottomed inland waterway vessel which does not have its own means of mechanical propulsion. The first modern barges were pulled by tugs, but nowadays most are pushed by pusher boats, or other vessels. ...
s in order to assess toll payments based upon the weight and value of the cargo carried. This requires that the unladen weight of the barge be known. A barge to be weighed was brought into a supporting cradle connected by levers to a weighing mechanism. The water was then drained and the scale balance adjusted to determine the barge
gross weight In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a vector quantity, the gravitational force acting on the object. Others define weight as a scalar qua ...
. Subtracting the
tare weight Tare weight , sometimes called unladen weight, is the weight of an empty vehicle or container. By subtracting tare weight from gross weight (laden weight), one can determine the weight of the goods carried or contained (the net weight). Etymolo ...
(the weight of the barge when empty) would give the cargo weight. Originally weighlocks measured the weight of the barge, initially by measuring the displacement of water from the lock by collecting the liquid in a separate measuring chamber after the barge had entered. This method also requires that the unladen weight of the barge be known.


See also

* Weigh bridge, a device for weighing trucks and railcars.


References

{{Reflist


External links


Erie Canal — The Weigh Lock
Locks (water navigation) Weighing instruments