Calculator Inputs
Use metric or imperial inputs. The page stays single column, while the input area shifts to three, two, or one field columns by screen size.
Example Data Table
These sample rows are calculated from the same equations used in the form.
| Case | Driver RPM | Driver Diameter (m) | Belt Length (m) | Slip (%) | BPF (Hz) | Driven RPM | Span Natural Frequency (Hz) |
|---|---|---|---|---|---|---|---|
| Drive A | 148 | 0.18 | 2.4 | 1.2 | 5.742 | 731.12 | 23.616 |
| Drive B | 96 | 0.22 | 3.1 | 0.5 | 3.549 | 955.2 | 17.604 |
| Drive C | 1775 | 0.14 | 1.95 | 2.2 | 6.526 | 867.98 | 28.478 |
Formula Used
The calculator first converts all inputs into consistent units. Slip reduces the theoretical belt speed, which gives a more realistic value for field work.
This frequency is the number of complete belt loops passing one fixed point each second. It is usually reported in hertz and cycles per minute.
This estimates the driven pulley speed after slip. It helps compare theoretical ratio behavior with actual operating conditions.
Here, L is span length, T is belt tension, and μ is mass per unit length. This string-style estimate helps flag resonance risk between belt harmonics and span vibration.
Higher harmonics often appear in vibration spectra. Comparing them with measured peaks helps identify whether the belt is a likely excitation source.
How to Use This Calculator
- Select metric or imperial units first.
- Enter driver RPM and both pulley diameters.
- Provide total belt length, slip percentage, and span length.
- Enter belt tension and belt mass per unit length.
- Choose how many harmonics you want listed.
- Add a measured peak frequency if you have spectrum data.
- Click the calculate button and review the result section above the form.
- Use the graph, harmonic table, and export buttons for reporting.
Key Output Meanings
BPF Harmonics Slip Effect Span Resonance Measured MatchTreat belt pass frequency as one clue, not the only clue. Strong diagnosis usually combines speed data, pulley condition, tension, alignment, spectrum peaks, and visual inspection.
Frequently Asked Questions
1. What is belt pass frequency?
It is the rate at which one full belt loop passes a fixed reference point. In vibration work, it often appears as a repeating spectral component tied to belt motion.
2. Why do harmonics matter?
Real belt systems rarely vibrate at only one frequency. Multiples of belt pass frequency can appear in spectra, especially when tension, wear, slip, or surface defects distort the motion.
3. Does slip change the result much?
Yes. Even modest slip lowers belt speed, belt pass frequency, and driven speed. If slip is ignored, calculated frequencies can drift away from measured vibration peaks.
4. Why compare with span natural frequency?
When a harmonic sits near the span natural frequency, vibration amplitude can rise sharply. That does not prove failure, but it helps explain noisy or unstable belt behavior.
5. What happens if both pulleys are the same size?
The speed ratio becomes roughly one-to-one. Driven RPM then stays near driver RPM, apart from slip and real-world losses in the belt system.
6. Can I use imperial inputs?
Yes. The calculator converts inches, feet, lbf, and lb/ft into consistent internal units, then returns the same physics outputs without changing the method.
7. How should I use measured peak frequency?
Enter a spectrum peak in hertz. The tool compares it with the predicted harmonics and reports the closest match, which helps screen likely belt-related peaks.
8. Is this enough to confirm a belt fault?
No. It is a screening and analysis tool. Final diagnosis should also include alignment checks, tension verification, pulley inspection, operating load, and measured vibration evidence.