Bevel Gear Forces
1. **Problem Statement:**
We have a bevel gearset with shaft AB rotating at 600 rev/min transmitting 10 hp, and gears with a 20° pressure angle. We need to find:
(a) The bevel angle $\gamma$ for the gear on shaft AB.
(b) The pitch-line velocity.
(c) The tangential, radial, and axial forces acting on the pinion.
2. **Given Data:**
- Speed of shaft AB, $N_1 = 600$ rev/min
- Power transmitted, $P = 10$ hp
- Pressure angle, $\phi = 20^\circ$
- Dimensions from the figure (in inches):
- Shaft D length segments: 6.50 in total, with 2.50 in and 3.63 in distances to gear center E
- Shaft AB length segments: 3.88 in and 3 in
- Diameters: 1.13 in (shaft D bottom), 0.88 in (shaft AB)
3. **Step (a): Determine bevel angle $\gamma$ for gear on shaft AB**
- The bevel angle $\gamma$ is the angle between the gear face and the shaft axis.
- For bevel gears, $\tan \gamma = \frac{r_2}{r_1}$ where $r_1$ and $r_2$ are pitch radii of the two gears.
- From the drawing, the shafts are at right angles, so the bevel angle for shaft AB gear is the angle between shaft AB and the gear face.
- Using the given distances, the bevel angle $\gamma$ can be found by geometry:
$$\gamma = \tan^{-1}\left(\frac{3.63}{3.88 + 3}\right) = \tan^{-1}\left(\frac{3.63}{6.88}\right)$$
Calculate:
$$\gamma = \tan^{-1}(0.5279) \approx 27.8^\circ$$
4. **Step (b): Determine pitch-line velocity $v$**
- Power $P$ in hp can be converted to watts: $P = 10 \times 745.7 = 7457$ W
- Speed $N_1 = 600$ rev/min
- Torque $T$ on shaft AB:
$$T = \frac{P \times 60}{2 \pi N_1} = \frac{7457 \times 60}{2 \pi \times 600}$$
Calculate:
$$T = \frac{447420}{3769.91} \approx 118.7 \text{ Nm}$$
- Pitch diameter $d_1$ of pinion (shaft AB gear) is approximately the diameter at gear center, say $d_1 = 2 \times r_1$.
- From figure, approximate pitch radius $r_1 = 3.88 + 3 = 6.88$ in = $6.88 \times 0.0254 = 0.1747$ m
- So pitch diameter $d_1 = 2 \times 0.1747 = 0.3494$ m
- Pitch line velocity:
$$v = \pi d_1 N_1 / 60 = \pi \times 0.3494 \times 600 / 60 = \pi \times 0.3494 \times 10 = 10.97 \text{ m/s}$$
5. **Step (c): Determine tangential, radial, and axial forces on pinion**
- Tangential force $F_t$:
$$F_t = \frac{2T}{d_1} = \frac{2 \times 118.7}{0.3494} = 679.8 \text{ N}$$
- Radial force $F_r$:
$$F_r = F_t \tan \phi = 679.8 \times \tan 20^\circ = 679.8 \times 0.3640 = 247.4 \text{ N}$$
- Axial force $F_a$:
$$F_a = F_t \tan \gamma = 679.8 \times \tan 27.8^\circ = 679.8 \times 0.5279 = 358.6 \text{ N}$$
**Final answers:**
- (a) Bevel angle $\gamma \approx 27.8^\circ$
- (b) Pitch-line velocity $v \approx 10.97$ m/s
- (c) Forces on pinion:
- Tangential force $F_t \approx 680$ N
- Radial force $F_r \approx 247$ N
- Axial force $F_a \approx 359$ N
These calculations assume approximate pitch radius from given dimensions and standard unit conversions.