### Coal Breaker Drive Pulley

The Crusher Drive Pulley is mounted on the Jackshaft for power from the engine and in turn provides power to the Crusher Pulley. The pulley is 80″ diameter with a 12-1/2″ face for a 10″ belt. It has 5 arms with an opening for a 3″ shaft.

### Data

This pulley rides the ‘Jackshaft’ which is the main power take-off from the steam engine with the RPM reduced from 250 RPM to 80.65 RPM.

• $\textbf{HP=45}$
• $\textbf{Pulley Diameter = D}$
• $D = 80"$
• $D = 42.33\text{ mm - O scale}$
• $\textbf{Pulley Circumference = C}$
• $C=20.94'$
• $\textbf{80.65 RPM}$
• $\textbf{Pulley Circumferential Velocity}$ $v_{m}$ (Pulley Circumference in Feet x RPM)
• $v_{m}=C_f*RPM$
• $v_{m}=1690 \text{ FPM}$
• $\textbf{Pulley Power = P}$
• $P = \frac{33000*H}{v_m}$
• $P = \frac{33000*45}{1689}$
• $P = 879$
• $\textbf{Shaft Diameter = d}$
• $d = 3"$
• $d = 1.6\text{ mm - O scale}$
• $\textbf{Belt width = b}$
• $b=10"$
• $b=5.29"\text{ mm - O scale}$
• $\textbf{Face Width = B}$
• $B = \frac{5}{4}b$
• $B = 12\frac{1}{2}"$
• $B=6.61\text{ mm - O scale}$
• $\textbf{Rounding of Pulley Face = s}$
• $s=\frac{1}{20}*b$
• $s=\frac{1}{20}*10$
• $s=.5"$
• $s=..265\text{ mm - O scale}$
• $\textbf{Rim Edge Thickness = k}$
• $k = 0.08 + \frac{B}{100}$
• $k = 0.08 + \frac{12.5}{100}$
• $k=.205"$
• $k=.11 \text{ mm - O scale}$
• $\textbf{Pulley Nave Width = w}$
• $w = 0.4 + \frac{d}{6} + \frac{R}{50}$
• $w = 0.4 + \frac{3}{6} + \frac{32}{50}$
• $w = 1.7"$
• $w=.9 \text{ mm - O scale}$
• $\textbf{Pulley Nave Length = L}$
• $L = 2.5w$
• $L = 4.25"$
• $L=2.25 \text{ mm - O scale}$
• $\textbf{Number of Arms = N}$
• $N = \frac{1}{2} (5+\frac{R}{b})$
• $N = \frac{1}{2} (5+\frac{32}{10})$
• $N = 4.5$
• $N=\text{5 - Rounding up}$
• $\textbf{Arm Width at Nave = h}$
• $h=0.24+\frac{b}{4}+\frac{R}{10*N}$
• $h=0.24+\frac{10}{4}+\frac{40}{10*5}$
• $h=0.24+2.5+.8$
• $h=3.54"$
• $h=1.87 \text{ mm - O scale}$
• $\textbf{Arm Width at Rim = }h_1$
• $h_1=\frac{2}{3}*h$
• $h_1=\frac{2}{3}*3.38$
• $h_1=2.36"$
• $h_1=1.25 \text{ mm - O scale}$

### 3D Printing

Note: These calculations were generated for a “Real-World” pulley. To 3D print these in 1:48 requires some modifications. The Rim Edge Thickness was calculated as .205″ which scales to 0.11 mm .. way too thin. I increase this to 0.3 mm .. which should be ok. The same with the arms .. except I will just say .. “may” be ok. If there are problems .. which would be related to simply the thickness of the parts I will enlarge them until the pulley prints without problems.