C.5.2 Handlines, Hangers, and Weights
The handline (Figure C-29) provides a simple and effective method for suspending a meter and weight assembly and is an alternative to the bridge rod. The handline requires hangers and weights to counteract the effects of moving water.
The handline is lightweight, compact, and easy to operate. These features make it particularly useful for obtaining measurements in winter when roads are impassable by a vehicle and it is necessary to walk a long distance to reach a metering section. The technician normally uses the handline to meter from footbridges and on ice cover. However, the handline is also a useful substitute when regular equipment malfunctions. The factors that limit its use in some cases are high velocities, excessive depths, and heavy weights.
Most current meter suppliers offer handline kits for use with the type of meter specified. The kits supplied for use with propeller meters usually include a weight of about 5-10 kg with matching hanger and pins. The meter calibration characteristics are usually identical to those of a rod-mounted meter. Price AA current meter kits can be combined with any standard Columbus weight (Figure C-30).
Figure C-29. Handline.
Figure C-30. Columbus weights.
A handline can be made from 15 m or less of 16-gauge cab tire electrical cord. The handline has a Cinch-Jones plug at one end and a cable thimble at the other. A clevis-type connector is fitted to the thimble. The cord is marked at 0.1-m intervals with strips of adhesive tape. The markings can be accomplished in the following manner: one strip for 0.1-m marks, two strips for 0.5-m marks and three strips to denote 1-m intervals.
Another way to make a handline is to spiral wrap a length of 1/16 inch galvanised aircraft cable with 16- or 18-gauge insulated automotive wire. The spiral wrap ensures that the aircraft cable carries the full load of the meter and weight assembly. The entire length of the wire and cable is then double-wrapped with a cloth type friction tape. The aircraft cable is secured to a clevis-type connector and the automotive wire is joined to the meter lead. The weight hanger and galvanised cable function as the return conductor.
A handline can also be made using Kevlar line instead of aircraft cable. However, because Kevlar is a non-conductor, two-conductor automotive wire must be used to transmit the electrical signal.
The American-made A55 sounding reel and a similar Australian model (Figure C-31) are light-duty sounding reels with a maximum load capacity of 45 kg. The reels are well suited for use in streams of low-to-moderate water velocity where cable length need not exceed 24 m. Reels can be utilized in a variety of situations such as bridge and boat boards, bridge cranes, and cable cars. The meter pulses are transmitted by the two conductor Ellsworth suspension cable through an electrical brush arrangement to the reel terminals. A two-position handle provides sufficient leverage for handling loads up to 45 kg, and the spring ratchet stop provides positive locking of the reel at any desired depth. Digital or analogue depth counters display depth.
Figure C-31. San sounding reel, made in Australia.
Associated Equipment. Three-wheeled bridge cranes, and bridge and boat boards can be purchased from suppliers. A combined bridge/boat board can be fabricated using a 3-m length of 50x150-mm (2x6-inch) fir as the jib on which an alloy plate fitted to accept the reel mounting studs is fixed. The outer end of the jib should be fitted with a 10- to 15-cm v-belt pulley.