This small clearance assures a positive reaction on the bridge balance 
of the electronic component. 
The operation of the wide-vane rotor in the summer of 1953 showed 
that the pivots to which Stoody #6 hardfacing had been applied seemed 
to wear faster than those used in the rotor with narrower vanes. Later 
examination by means of hardness tests revealed that the facilities for 
applying the hardfacing to a stainless steel pivot body did not permit 
the necessary degree of temperature control. As a result the pivot 
often had a hardness lower than either the stainless steel body or the 
hardfacing. This would account for one set of pivots exhibiting a 
reasonable wear record while a following set would fail in a very short 
time. The most satisfactory pivot at the present time is one with a 
stainless steel body and a point of Stoody #6 hardfacing set into the 
body. This unit is used in combination with the pivot ball bearing 
units. 
Changes in the electronic recording circuits were necessitated 
when it was found that the meter was sensitive to the amount of total 
dissolved solids present in the water. Revised circuits are shown in 
Figure 3. The form now in use cannot be moved from one location of a 
certain dissolved solids concentration to another of different concen= 
tration without making considerable adjustments. If the new dissolved 
solids count were many times that of the original station some alteration 
of the circuits might be required. 
Experiments are now being carried on to eliminate the sensitivity 
to dissolved solids. Progress thus far has shown that use of electromag= 
nets as electrodes and vane feet of nonmagnetic metal can probably be 
developed to a satisfactory standard. It is hoped that with a few minor 
changes in the counter circuit meter, registration will no longer be in- 
fluenced by variation in total dissolved solids content of the water in 
which it is used. If present experiments prove this to be the case the 
meter will be suitable for wider application. Figures ) through 8 are 
calibration curves for all meter assemblies rated to date by the Bureau 
of Reclamation. 
Figure ) is the calibration curve for the original Bureau-designed 
meter (Figure 1). This meter would not operate consistently for velocities 
under 0.1) of a foot per second. The curve is linear as was the case for 
the Pegram meter, and for all other assemblies tested. No attempt was 
made to rate the meter above 5.5 feet per second, Pivot ball bearing units 
were used for all tests as well as for the period of use in the cross 
channel. The pivots were well worn after five weeks in the cross channel, 
yet a recalibration showed the angular shift in the rating curve slope to 
be very slight. It would seem, therefore, that so long as the pivot can 
still turn freely in the bearings without danger of dropping free of them, 
the condition of the pivot is not a critical factor. It is believed by 
Bureau engineers that hardfacing the entire pivot point will permit al- 
most indefinite use because wear should proceed only until the groove in 
the point is of sufficient area to carry the maximum thrust encountered. 
