Wheel (10-pitch), 200 teeth; pinion, 25 teeth;
axles equal, effective circumference of
each being 2"·87; oiled brass bearings;
velocity ratio, 8; mechanical efficiency,
4·1; useful effect, 51 per cent.; formula,
_P_ = 2·46 + 0·21 _R_.
+-----------+---------+---------+-----------+---------------+
| | | | P. | Difference of |
| Number of | R. |Observed |Calculated | the observed |
|Experiment.| Load | power | power |and calculated |
| | in lbs. | in lbs. | in lbs. | powers. |
+-----------+---------+---------+-----------+---------------+
| 1 | 14 | 5·4 | 5·4 | 0·0 |
| 2 | 28 | 8·7 | 8·3 | - 0·4 |
| 3 | 42 | 11·0 | 11·3 | + 0·3 |
| 4 | 56 | 13·7 | 14·2 | + 0·5 |
| 5 | 70 | 17·5 | 17·2 | - 0·3 |
| 6 | 84 | 20·0 | 20·1 | + 0·1 |
| 7 | 98 | 23·0 | 23·0 | 0·0 |
| 8 | 112 | 26·0 | 26·0 | 0·0 |
+-----------+---------+---------+-----------+---------------+
330. The large amount of friction present in this contrivance is the
consequence of winding the rope directly upon the axle instead of upon
a barrel, as already pointed out in Art. 319. We might place barrels
upon these axles and demonstrate the truth of this statement; but we
need not delay to do so, as we use the barrel in the machines which we
shall next describe.