Principle

The computer pendulum friction coefficient tester is a dynamic pendulum impact type instrument. It is developed based on the fundamental principle that "the potential energy loss of the pendulum equals the work done to overcome the friction of the road surface by the rubber sheet sliding on the road surface at the end of the pendulum arm."

Structure

1. Base: Composed of T-shaped legs (cast), leveling screws, and a spirit level bubble, serving to level and support the instrument.
2. Upright column: Consists of the column, lifting mechanism, guide rod, and instrument handle, used for raising, lowering, and fixing the position of the pendulum head.
3. Release switch: Installed on the cantilever, used to hold the pendulum rod in a horizontal position and release it to fall.
4. Steering system: Includes tightening handle, pendulum shaft, steering knuckle, and bearings, which connect the pendulum, fix its position, and ensure free swinging within the pendulum plane.
5. Indication system: The LCD screen directly displays the pendulum value.
6. Pendulum: Composed of upper and lower joints, pendulum rod, lifting handle, hammer shell, sliding block, and rubber sheet (76.2*25.4*6.35±0.5mm or 31.75*25.4*6.35±0.5mm). It applies a specified torque to the pendulum center and a specified pressure on the road surface. The torque at the front and rear, left and right of the pendulum head is balanced, serving as the technical basis for measuring the road surface friction coefficient.

Main Technical Parameters

1. Pendulum mass: 1500±30g; pendulum center of gravity distance: 410±5mm (distance from pendulum center of swing).
2. Normal static pressure of the rubber sheet on the road surface: 2263g±50g (22.2N±0.5N).
3. Rubber sheet specifications: 76.2*25.4*6.35±0.5mm
(or 31.75*25.4*6.35±0.5mm optional).
4. Distance from the outer edge of the rubber sheet to the pendulum center of swing: 510±2mm.
5. Total instrument mass: approximately 16KG.
6. Pendulum value accuracy: 0.1 BPN, pendulum value range: 0-150 BPN.
7. Charging power supply: DC 12V, 500mA.
8. Temperature measurement accuracy: 0.1℃, measurement range: 0-100℃.
9. Computer pendulum instrument battery life: can continuously work for more than 35 hours on a full charge.
10. Chinese LCD screen: 3.3 inches, displaying working status, pendulum value, temperature, power, and test data parameters all synchronously in Chinese.
11. Operating temperature of the computer pendulum instrument: -15 to 65 degrees Celsius.
12. Dimensions of the computer pendulum instrument (L*W*H): 600mm*450mm*600mm.
13. Pendulum torque: 61500 gram-millimeters.

Usage Method

1. Point selection: On the test road section, along the left wheel track in the driving direction, select five representative test points, each about 5-10 meters apart.
2. Instrument leveling
Place the instrument at the test point and align the pendulum swing direction with the driving direction. Adjust the leveling screws to center the spirit level bubble.
3. Zero adjustment
A. Allow the pendulum to swing freely without the rubber sheet touching the road surface, then tighten the fixing handle.
B. Turn on the pendulum instrument power.
C. Move the pendulum rod to the right, use your right hand to lift the pendulum rod to the switch body position, so that the positioning snap ring on the pendulum rod enters the release switch slot. When you hear a "click," release your hand. At this time, the pendulum rod is in the horizontal release position.
D. After the system enters standby mode, press the road surface key once, and the computer enters the friction coefficient measurement state. Then press the release switch button to let the pendulum fall to the lower left. When the pendulum falls from the highest left position, be sure to catch the pendulum rod by hand. Repeat this operation in sequence. If most pendulum values exceed 2, press and hold the zero mark key for 5 seconds until the screen displays "OK." The previous values have been automatically corrected by the integrated computer and stored in the computer chip, and will not disappear when powered off.
4. Calibrate sliding length

A. Use a rubber brush to remove loose particles and debris from the road surface within the test range.
B. Let the pendulum hang freely, align the middle of the ruler with the pendulum rod, and make the sliding ruler parallel to the test direction and close to the rubber sheet.
C. Loosen the fixing handle, turn the lifting handle to let the pendulum slowly descend, and simultaneously lift the lifting handle with your right hand to move the pendulum to the right. Place the sliding block at the right end of the ruler so that it contacts the road surface and aligns with the ruler scale.
Then lift the lifting handle to move the pendulum to the left, place the sliding block at the left end of the ruler so that it contacts the road surface and aligns with the left scale mark of the ruler. Tighten the fixing handle and recheck the sliding length. During this process, the leveling screws can be used to fine-tune the sliding length to accurately 126±1mm (76mm when measuring polished values), but note that the spirit level bubble should remain centered during fine adjustments.
5. Measurement: Sprinkle water on the road surface and use a rubber brush to scrub and wash away the mud. Then sprinkle water again, press the test button on the panel (road surface or polishing), and press the release switch button to slide the pendulum over the road surface. The LCD screen will display the pendulum value of the road surface. Be sure to hold the pendulum rod with your left hand and lift the handle with your right hand to raise the sliding block so that the pendulum head can pass over the road surface and move to the right. Use your right hand to lift the pendulum rod to a horizontal position, allowing the positioning clip on the pendulum rod to enter the release switch slot. When you hear a "click" sound, release your hand. At this time, the pendulum head is again in the horizontal release position. Repeat steps 1-5 and measure five times (water should be sprinkled each time). The difference between the five values should not exceed three units. If the difference is greater than three units, check the cause.
Note: Do not turn off the power during the test. The measured data will be automatically recorded in the computer, with a maximum of 60 records. If a printer is connected, press the print button to print all test results. (If there is no printer, do not press the print button. If accidentally pressed, the device must be turned off and restarted to function normally.)
Repeat the above operations until the specified requirements are met.
6. Measurement Results
A. The average of five readings at each measurement point represents the pendulum value of that point, and the average of five measurement points represents the pendulum value of the measured road section.
B. The measured reading (referred to as "pendulum value") divided by 100 is the friction coefficient of the road surface. For example: a pendulum value of 33 corresponds to a friction coefficient of 0.33.
7. Precautions
A. Since the friction coefficient of the road surface is affected by season and temperature, the test date and wet road temperature should be recorded. We have equipped an electronic thermometer with an original American sensor to ensure measurement accuracy and precision.
B. The test road section should describe the road surface structure type, appearance, and years of use.
C. When the pendulum head is released from the release switch for testing or inspection, the pendulum rod must be caught with the left hand during the downward swing to avoid damaging the instrument.
D. There should be no significant convex or concave shapes within the effective sliding range of the rubber sheet on the sliding block to avoid affecting the measurement values.
E. When calibrating the sliding length, it should be based on the rubber sheet just touching the road surface. Do not use the pendulum's force to slide forward to avoid calibrating an excessively long sliding length.
F. The road surface friction coefficient varies across the highway cross-section, usually smaller in the middle and larger at the edges. To reflect the most unfavorable condition of the test section, choose the position with the smallest friction coefficient and more frequent braking, i.e., the left wheel track along the driving direction.
G. When using new rubber sheets on the sliding block, test 10 times on a dry road surface first, then 20 times on a wet road surface before use. The wear on the long edge of the rubber sheet must not exceed 3.2mm, and the short edge must not exceed 1.6mm. Otherwise, replace with a new rubber sheet. Also, rubber sheets contaminated by oil cannot be used. The effective service life of the rubber sheet is one year. After one year, regardless of use, it must not be used for measurement because rubber ages, and its elasticity and hardness change, affecting test results. (Remove the old rubber sheet from the sliding block and clean the flat surface of the sliding block. Use adhesive to bond the new rubber sheet to the new sliding block and use after curing for a period.)
H. The positioning screw on the pendulum head must not be turned after calibration and during use (adjust only during calibration), otherwise it will affect the pressure value.
8. Description of components on the control panel;
A. Road Surface Button: Press this button once, then press the release switch button once to enter the friction coefficient test.
B. Zeroing Button: If the instrument does not zero, press and hold this button for 5 seconds, and the system will automatically calibrate. See zeroing operation steps.
C. Print Button: After obtaining test results, connect a printer and press this button to print all test results (only operable with optional integrated printer or external SC5890).
D. Exit Button: Regardless of the working state, pressing this button once will return the working state to standby.
E. Query Button: Press this button once to display pendulum values and serial numbers one by one upwards.
F. Power: Power switch.
G. Polishing Button: Press this button once, then press the release switch button once to enter the polishing value test.
H. LCD Screen: Displays Chinese serial numbers, pendulum values, temperature, battery level, working status, and various parameters.
9. Description of components on the rear panel
A. Temperature Sensor: Can measure surface temperature and ambient temperature;
B. DC12V Power Socket: Input port for charging the internal battery, 12V 500mA;
C. Printer: Parallel port printer output, compatible with printer model SC-5890;
D. Angle Sensor: High-precision angle sensor input.

Maintenance, Storage, and Transportation of the Instrument

1. The computer pendulum-type friction coefficient tester is a precision instrument. Care must be taken to protect its components to avoid affecting test accuracy. If unfamiliar with the instrument's mechanisms, carefully read the user manual before use and understand the structure, function, and operation methods of each part. Except for permitted movable parts or allowed removal of the pendulum head for calibration, do not disassemble the instrument casually.

2. After use, wipe all parts clean and store them in the case. The instrument should be kept in a dry, ventilated room free of acidic and corrosive vapors.

3. Except during testing or other special circumstances, the instrument should be placed and moved inside the packaging box.

4. During long-distance transportation, the instrument should be packed in a transport case and should not be subjected to sudden impacts or excessive vibrations during loading and transportation (pack according to the original box position).

Calibration of the electronic part of the computer pendulum instrument

If there is a difference between the data read by the computer pendulum instrument and the verification data, you can use a flathead screwdriver to adjust the adjustable resistor on the back cover of the electrical box (on the right side). The specific method is as follows:
1. Move the pendulum arm to the upper right slot; at this time, the lower right corner of the screen displays and records a four-digit number A.
2. Then release the pendulum arm and move it to the left horizontal position and hold it; record the four-digit number B displayed at the lower right corner of the screen.
3. B - A = C; then divide the standard value by C and multiply by B to get D.
4. Use a flathead screwdriver to adjust the adjustable resistor on the back cover until the four-digit number B at the lower right corner of the LCD screen changes to D. Press the exit key to move the pendulum arm back into the slot, swing it empty a few times, then press and hold the zeroing key. The instrument can then be used normally.
5. If there is still a difference, steps 1 to 4 can be repeated.

Calibration of the pendulum instrument

The pendulum instrument should be calibrated at least once a year. Please pack the instrument and return it to the factory for calibration.

Packing list

1. Main unit: one set 2. Manual: one copy (including certificate of conformity)
3. Rubber sheet: one piece (random) 4. Scale ruler: one piece
5. Rubber scraper: one piece 6. Water spray bottle: one piece
7. Temperature sensor: one set (random) 8. 12V DC power supply: one unit