Jackscrews

ERDC TN-DOER-T3

January 2001

There shall be a covered manhole in the platform to allow access to the interior of the weir

when it is fully raised.

A ladder shall extend from the lower end of the framework to the platform. The ladder shall be

strong enough to support one end of an aluminum catwalk of up to 40 ft in length and a mini-

mum weight of 800 pounds, plus an additional weight of 1,000 pounds for personnel and

equipment.

The platform shall include handrails adjacent to the top of the ladder to protect personnel

standing on the platform.

Jackscrews. The jackscrews shall be a set of three Acme screw assemblies, sufficient in length to

reach from the framework platform to the top of the weir crest sections when fully retracted. Each

screw shall be mounted to operate as a translational actuator (no rotation of the screw). Each screw

passes vertically through a worm gear drive on the drive mechanism platform; the three actuators

shall be mechanically coupled so that the screws are drawn up in unison to hold the weir crest level

throughout its travel. One jackscrew shall be fitted with an electrical limit switch, set to stop weir

travel 1 in. short of the mechanical stops. Each screw shall be protected from sediment and debris by

a bellows-type boot that prevents sediments from being carried into the actuator drive as the screw

passes through. The boot may be permeable to water; however, the actuator shall be of bronze con-

struction to protect it from corrosion. System backlash due to construction and monitoring of the

jackscrews shall not result in an out-of-level condition at the weir crest in excess of 0.25 in.

Motor and Gear Mechanism. There shall be a d-c gear motor, rated at not less than 1/3 horse-

power. Batteries that are recharged by a solar cell array so that they can automatically renew their

charge after any adjustment of the weir shall power it. The motor speed shall be geared down to de-

liver a linear actuation force to the jackscrews of not less than 10,000 lbf total, and a linear velocity at

the weir crest of not less than 2 in. per minute.

Controls. The controls shall be divided into three classes:

Local controls.

Remote controls.

Manual controls.

The local and remote controls are essentially the same and provide manual operation of the weir

height adjustment. The difference is that the remote controls allow weir adjustment by hand-held

control from up to 100 ft away while the local controls are located on the weir platform.

Battery Power. Conventional 12-volt automobile storage batteries shall be used, carrying a charge

sufficient to operate the weir through a full cycle of extension and retraction.

Solar Panel. A solar panel shall be provided having sufficient capacity to fully recharge the system

batteries within 5 days of average weather conditions after they have been discharged by operating

the weir through a full extend and retract cycle. It shall be mounted on a mast that allows it to be

aimed in the direction and azimuth best suited to the latitude at the weir site.