Slide Rule Vibrating Reed Tachometer: A Versatile Tool for Measuring Speed or Frequency

By Jason Witte

 

A vibrating reed tachometer provides a simple, mechanical way to measure rotational speed and vibration frequency without requiring power or complex setup.

In the world of maintenance and repair, measurement of speed can be essential for optimizing the performance of various machines and equipment, making a vibrating reed tachometer the perfect solution for the job.

One crucial aspect of measurement is determining the speed and frequency of rotating equipment like rotary vibrators, compactors, power tools, motors, and pumps. For this purpose, Slide Rule Vibrating Reed Tachometers have proven to be versatile and reliable devices.

This article explains the working principles and applications of slide rule vibrating reed tachometers in measuring the speed and frequency of vibrators, power tools, and other rotating equipment.

Understanding Reed Tachometers

A vibrating reed tachometer, also known as a contact tachometer or resonant reed tachometer, is a handheld instrument that measures the rotational speed of a rotating shaft. It consists of a reed contained in a thin metal pointer. The bullet nose tip of the pointer is placed in close proximity to the target object being measured. When the target object rotates, it causes the reed to vibrate from side to side (throw), creating pulses. These pulses can then be converted into readable measurements of speed or frequency by adjusting the reed to its maximum throw using the pointer’s slide mechanism.

Working Principle of Slide Rule Vibrating Reed Tachometers

This type of Vibrating Reed Tachometer is inexpensive to purchase and simple to use:

1. Press the reed tachometer’s bullet-nose tip against the rotating or vibrating object.
   • When checking air and electric vibrators, tools, or electric motors, the instrument is direct-read in Revolutions per Minute (RPM) or Vibrations per Minute (VPM).
   • On power tools, electric vibrators, and engines on mowers, boats, model planes, etc., press the Bullet Nose against an area where vibration can be felt with fingers.
   • On air vibrators, press the Bullet Nose against the air supply hose about 4" from the vibrator’s inlet.
      
2. Move the reed tachometer’s tuning slide up or down until the reed reaches maximum throw.
   • For most accurate results, average 3 readings.
      
3. For the STD-TAK model (for equipment operating in the 2,000 to 21,000 RPM range): multiply the reading by 1,000 for Vibrator VPM, or shaft RPM.
    
4. For the SLO-TAK model (for equipment operating in the 200 to 2,000 RPM range): multiply each reading by 100 for Vibrator VPM, or shaft RPM.
    
5. The reed’s throw is in direct proportion to speed and amplitude.
   • Each 1/2" of throw equals .001" amplitude.
      
6. For internal combustion engines, the reed tachometer will give a direct read of the crank-shaft speed for 1 and 2 cylinder, 4-cycle engines.
   • To check the RPM of internal combustion engines, note that the slide rule reed tachometer gives the number of power impulses. Therefore, to measure power RPM on:
     • A 2-Cycle Engine: Divide the reading by the number of cylinders.
     • A 4-Cycle Engine: Divide the reading by 1/2 the number of cylinders.

What are the Applications of Reed Tachometers?

• Vibrators and Vibratory Equipment:
  In industries such as manufacturing, mining, agriculture, and construction, vibrators are used for prompting material flow from bins and hoppers, unloading railcars, compacting concrete, screening materials, and feeding bulk solids. Monitoring the rotational speed of these vibrators (Vibrations per Minute [VPM]) is crucial for maintaining operational efficiency and ensuring safety.
   
• Power Tools:
  Slide rule reed tachometers are indispensable tools for maintaining power tools, such as drills, grinders, and saws. By measuring their rotational speed, technicians can verify if the tools are operating within safe limits and troubleshoot any performance issues.
   
• Rotating Machinery:
  In industrial settings, various rotating machinery like motors, pumps, and turbines play a vital role in production processes. Using reed tachometers to measure their speed and frequency aids in preventive maintenance and minimizes downtime.
   
• Automotive Industry:
  In the automotive sector, reed tachometers help mechanics check engine RPM, diagnose engine problems, and ensure optimal performance.
   
• Marine Applications:
  Reed tachometers are used in the marine industry for measuring the speed of boat propellers, which impacts fuel efficiency and overall performance.

What are the Advantages of Slide Rule Vibrating Reed Tachometers?

Vibrating Reed tachometers offer several advantages over alternative measurement methods:

• Versatility: These instruments can be used for a wide range of rotating objects, making them highly versatile in various industries.​​​​​​
   
• Accuracy: When calibrated and used properly, Vibrating Reed Tachometers provide precise and reliable measurements of rotational speed and frequency.
   
• Portability: Handheld Vibrating Reed Tachometers are compact and lightweight, allowing for easy portability and on-the-spot measurements.
   
• Simple Operation: Vibrating Reed Tachometers are user-friendly, requiring minimal training for accurate readings.
   
• No power required: Can be used in hazardous areas.
   
• Maintenance efficiency: With accurate speed reading, maintenance can swiftly identify and address performance irregularities.
   
• No Load Imposed: Impose no load on equipment being tested.

Why Vibrating Reed Tachometers Matter in Industrial Applications

Slide Rule Vibrating Reed Tachometers have proven to be invaluable tools for measuring the speed and frequency of vibrators, power tools, and other rotating objects. Their simple yet effective working principles, coupled with versatility, accuracy and low cost, make them indispensable in a range of industries. Whether it's in construction, manufacturing, automotive, or marine applications, reed tachometers play a vital role in maintaining efficiency, safety, and optimal performance of rotating machinery.

Jason Witte is Service Shop Manager at AIRMATIC and has over 18 years of experience in overseeing the daily repair operation that quickly and consistently brings Customers’ tools and equipment back to new tool standards.

Thanks for reading our post. If you’d like to learn about the importance of monitoring and maintaining proper vibrator speed, please contact one of our experts at +215-333-5600 or at infocenter@airmatic.com.

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