2015-08-21
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h=h1×h2×….×h n,
where h1,h2,….hn are efficiencies of all kinematic pairs and links where the input power is lost.
For our case
h = h c × h hsg × h cd ×h b 3,
where h c is the efficiency of the coupling;
h hsg is the efficiency of helical spur gears;
h cd is the efficiency of the chain drive;
h b takes into account losses in one pair of bearings.
The magnitudes of all efficiencies are given in table 1.1.
The following components are recommended to use for mechanical drives being analyzed:
- belt drive with flat belt;
- chain drive with roller chain;
- rolling bearings;
- coupling with rubber bushed studs;
Table 1.1
The magnitudes of efficiencies of the drives
| Name | Efficiency | |
| Closed drive | Opened drive | |
| Gearings: - straight spur gears - helical spur gears - bevel gears Worm gearing: -one thread worm -two thread worm -four thread worm Belt drives: - flat belt drive - V-belt drive - toothed belt drive Chain drives: - roller chain - toothed chain Couplings: - with rubber bushed studs - flexible coupling - rigid coupling Bearings: - rolling bearings - sliding bearings | 0.98 - 0.99 0.97 - 0.98 0.96 - 0.98 0.7 - 0.75 0.75 - 0.82 0.82 - 0.92 0.996 0.985 - 0.995 0.99 - 0.995 0.98 - 0.985 | 0.94 - 0.96 0.94 - 0.95 0.92 - 0.94 0.96 - 0.98 0.95 - 0.97 0.94 - 0.97 0.94 - 0.96 0.96 - 0.97 |
Let us assume that h c = 0.996, h hsg = 0.97,
h cd = 0.94, h b = 0.99. Then
h= 0.996 × 0.97 × 0.94 × 0.993 = 0.881.
Pay attention that the magnitude of the total efficiency must be rounded off to thousandth or ten thousandth.
1.3. Determine the input power
