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Basic Belt Drive Design

Basic Belt Drive Design. Size. Center Distance. (center shaft to center shaft). Shaft Size. Take-up/Installation Allowance. Belt Drive Basics. DRIVER (R). DRIVEN (N) . Size. Rated HP Speed Efficiency. Motor Nameplate. 4”. Speed-Down. N. 10”. R. 1750 rpm. 10”. R.

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Basic Belt Drive Design

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  1. Basic Belt Drive Design

  2. Size Center Distance (center shaft to center shaft) Shaft Size Take-up/Installation Allowance Belt Drive Basics DRIVER (R) DRIVEN (N) Size Rated HP Speed Efficiency Motor Nameplate

  3. 4” Speed-Down N 10” R 1750 rpm 10” R Speed-Up N 4” Belt Drive Basics Speed Ratio = 2.5 1750/2.5 = 700 rpm 1750 x 2.5 = 4375 rpm NOTE: Ratio is always specified as a number greater than 1

  4. Belt Drive Terms • Pitch Length -Total length in mm as measured along the pitch line • Tooth Pitch-Distance in mm between two adjacent tooth centers as measured along pitch line of belt • Pitch line-Section of belt between teeth and backing • Pitch Diameter-Imaginary line on sprocket just above the teeth, where pitch line of belt rides • Bore-Size of hole in bushing • Bushing-Sprockets come with pilot holes, bushings connect sprocket to shaft through pilot hole. • Minimum Plain Bore-No bushing needed, bored to size, or bore yourself • Bushing styles-TaperLock, narrow like roller chain, QD has shoulder

  5. Effect of Variable Drive Loading Mathematics and Testing Confirm That -- • Belt Drives Exert Belt Pull Equivalent to Belt Installation Tension --- Continuously • Roller Chain Drives Exert Belt Pull Proportional to Torque Loads --- Effective Pull • Belt Pull Remains Constant Under Variable Loads – Until Belt Lift Occurs

  6. Drive Designed for Reduced Belt Pull • Drives Designed & Tensioned for Peak Loads Exert Peak Belt Pull Continuously • Apply Reduced Design Service Factor to Peak Load for Reduced Belt Pull • Drive Design Load Should Meet or Exceed Intermittent Peak Load -- At Least 1.0 Service Factor • Belt Pull From Reduced Design Loads Will Still Remain Constant

  7. C A S H Drive Design Example enter distance 28 in. Fan, 24 hr/day pplication data peed / size / ratio 2.5 : 1 10 hp @ 1750 rpm orsepower

  8. Drive Design Steps • Determine service factor, design HP • Estimate pitch required / select belt type • Find ratio(s) in table • Select appropriate combo (c.d., belt length.) • Select width (check HP ratings, apply factors) • Check dimensional restrictions • Re-iterate if necessary

  9. We see, For a 10 HP motor, running a fan 24 hours a day, SERVICE FACTOR = 1.7 Thus the DESIGN HORSEPOWER = 10 x 1.7 = 17 H.P.

  10. Drive Design Steps • Determine service factor, design HP • Estimate pitch required / select belt type • Find ratio(s) in table • Select appropriate combo (c.d., belt lgth.) • Select width (check HP ratings, apply factors) • Check dimensional restrictions • Re-iterate if necessary

  11. We see, For a DESIGN HORSEPOWER HP running a fan at 1750 RPM, the Belt Pitch falls in the 8mm region. So we select a 8mm pitch Belt.

  12. Drive Design Steps • Determine service factor, design HP • Estimate pitch required / select belt type • Find ratio(s) in table • Select appropriate combo (c.d., belt lgth.) • Select width (check HP ratings, apply factors) • Check dimensional restrictions • Re-iterate if necessary

  13. R = 8M - 56 - ?? N = 8M - 140 - ?? Belt = 8M - 2240 - ??

  14. Drive Design Steps • Determine service factor, design HP • Estimate pitch required / select belt type • Find ratio(s) in table • Select appropriate combo (c.d., belt length.) • Select width (check HP ratings, apply factors) • Check dimensional restrictions • Re-iterate if necessary

  15. 15.4 + 0.58 = 15.98

  16. 15.98x1.26 = 20.1 HP 8M - 56S - 12 driveR 8M - 140S - 12 driveN 8M - 2240 - 12 Belt

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