Coal Breaker Pulley

This is the pulley on the Coal Breaker itself. I am designing for the larger breaker which requires 45 hp. I have a page on crushers down to 10 hp on my Coal Breaker page. You can the assortment of breakers from 10 HP with a 10 ton per hour capacity up to the 45 HP breaker with a 83 ton per hour capacity.

The pulley is 64″ in diameter with a 12-1/2″ face for a 10″ belt. It has five arms and an opening for a 3″ shaft. I changed the opening to 6″ to match the shafting on my Coal Breaker. This was calculated as you can see below.

3D printing : I am putting progress on this on the bottom of the page.

Data

  • \textbf{HP=45}
  • \textbf{Pulley Diameter = D}
    • D = 64"
    • D = 33.87\text{ mm - O scale}
  • \textbf{Pulley Circumference = C}
    • C=16.755'
  • \textbf{100 RPM}
  • \textbf{Pulley Circumferential Velocity} v_{m} (Pulley Circumference in Feet x RPM)
    • v_{m}=C_f*RPM
    • v_{m}=1689 \text{ FPM}
  • \textbf{Pulley Power = P}
    • P = \frac{33000*H}{v_m}
    • P = \frac{33000*45}{1689}
    • P = 879
  • \textbf{Shaft Diameter = d}
    • d = 6"
    • d = 3.18\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{6}{6} + \frac{32}{50}
    • w = 2.2"
    • w=1.17 \text{ mm - O scale}
  • \textbf{Pulley Nave Length = L}
    • L = 2.5w
    • L = 5.5"
    • L=2.92 \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 = 4.1
    • 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{32}{10*5}
    • h=0.24+2.5+.64
    • h=3.54"
    • h=1.88 \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

  • Plan: These calculations were generated for a “Real-World” pulley. To 3D print these in 1:48 requires some modifications. The Rim Edge Thickness is shown as .205″ which scales to 0.11 mm .. way too thin. I increased 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.
  • Results – Test Print #1: The first test print actually went pretty well. I printed it flat without any tilt .. sometimes you CAN break the rules. I did not want any support scars on the face of the pulley.
    • There was sag between the supports as I had too few spaced too far apart. You can see on the far side where the print pulled away from supports. The hole in the center was a tight fit on a 1/8″ rod .. looking at the CAD I found I had forgotten to pad that hole a bit so for the next print I enlarged it to 0.128″ dia.
    • I added the supports manually for this test. The next one I will use Chitubox to add supports
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