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 ...
lock
Lock(s) or Locked 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 entertainme ...
designed to determine the weight of
barge
A barge is typically a flat-bottomed boat, flat-bottomed vessel which does not have its own means of mechanical propulsion. Original use was on inland waterways, while modern use is on both inland and ocean, marine water environments. The firs ...
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 a quantity associated with the gravitational force exerted on the object by other objects in its environment, although there is some variation and debate as to the exact definition.
Some st ...
. 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).
Ety ...
(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