Features and investigating possibilities with the "Hydro - Prop"
The operating principle of the "Hydro Prop" Mk 1,2 & 3 is simple reliable and accurate. The impeller is moved along a brass studding by the velocity of the water for a pre determined length. This travel is accurately timed on a stopwatch and the result tabulated and ckecked against a calibration graph provided. By applying this principle to a section of river the "Hydro Prop" can be used to measure the velocity at any pre determined depth. This is achieved by moving the head clamp block along the graduated stem. From these measurements, a velocity vertical and cross-sectional profile, for a small stream may be calculated, thus illistrating the effect of of bed and bank friction. Comparisons can also be made as to the location of maximum velocity volume in conjunction with the cross-sectional area to calculate the rate of discharge.
All the parts are interchangeable except for the Mk1 - 350, thus the wading rods can be extended and extra heads fitted as required for each investigating task. For example as seen below a standard Mk2 -900E in use horizontally to demonstrate variation in velocity below the surface. Note the variation in impeller travel. The same arrangement for normal vertical use would illustrate a vertical velocity profile from the stream bed to the surface.
To use the instrument the impeller is wound to the start position by pointing down stream. The head is set at 0.6 depth below the surface, in order to give an average velocity reading. Stand downstream of the meter while timing the impeller. A second person can be helpful to do the timing. The meter operator tells the timmer when to start and stop recording.
SAFETY WARNING - Never enter a river or stream unless you can swim or if you are uncertain of the depth or strength of the flow.