Bicycle Frame Bottom Bracket Pedaling Fatigue Test Machine (FH-CJ2010)

Simulating a lifetime of pedaling forces — in one controlled test.

The FH-CJ2010 applies cyclic pedaling loads to bicycle frames at the bottom bracket, replicating the alternating left-right crank forces that accumulate into fatigue stress at the bottom bracket shell, chainstay welds, and seat tube junction over a frame's service life. Two independent 5,000N disc-type servo cylinders apply opposing sinusoidal forces through 175mm replacement cranks set at 45° — exactly as specified in ISO 4210-6.4.3 — with closed-loop force control, real-time dual-channel curve display, and automatic stop on specimen failure or out-of-spec load.

Quick Specs

• Standards: ISO 4210-6.4.3, EN 15194, EN 14764, EN 14766, EN 14781, CNS, JIS, DIN, NF, CPSC, CSA, AS, BS

• Force sensors: 2 × 5,000N disc-type (resolution 1/10,000)

• Actuator: Dual electric servo cylinders, closed-loop force control

• Stroke: ±75mm (150mm total)

• Waveform: Sinusoidal

• Frequency: 0–5Hz

• Test cycles: 0–999,999 (freely settable); standard requirement: 100,000

• Force acquisition rate: >200kHz

• Optional fixtures: Frame pedaling / front fork / handlebar / saddle fatigue

• Power: AC 220V, 2.5kW, 12A

• Bench dimensions: 1280 × 1830 × 2100mm

 Table of Contents

1. Why Bottom Bracket Pedaling Fatigue Testing Is a Mandatory Frame Test

2. Overview of the FH-CJ2010 Test Machine

3. Standards Covered: ISO 4210-6.4.3, EN 15194 and Nine National Standards

4. Test Methods, Force Values, and Setup Geometry

5. Design Features of the FH-CJ2010

6. Technical Specifications

7. How the FH-CJ2010 Testing Process Works

8. Benefits for Frame Manufacturers and Testing Labs

9. Choosing the Right Bottom Bracket Pedaling Fatigue Tester

10. Real-World Application Scenarios

11. FAQs for the FH-CJ2010

12. Related Testing Equipment

13. Get a Quote from Feihong Machine

Why Bottom Bracket Pedaling Fatigue Testing Is a Mandatory Frame Test

The bottom bracket is the highest-stress junction in a bicycle frame. Every pedal stroke transmits a bending moment into the bottom bracket shell — one side in compression, the other in tension — alternating left and right with every rotation. Over a typical riding life, this produces millions of load reversals at the very point where multiple structural tubes converge: the chainstays, seat tube, and down tube all meet at the bottom bracket shell, making this junction the most geometrically complex weld region in the frame and the location most susceptible to fatigue crack initiation under cyclic pedaling loads.

ISO 4210-6 addresses this with a dedicated test clause — clause 6.4.3, the bottom bracket pedaling fatigue test — that is separate from both the vertical seat tube test (6.4.5) and the horizontal dropout test (6.4.4). All three tests are required for full frame type approval; none substitutes for the others, because each loads the frame in a fundamentally different stress distribution.

The pedaling fatigue test is distinctive in its loading geometry: two replacement cranks set at 45° to each other transmit opposing vertical forces to the bottom bracket in a pattern that replicates the phase relationship of real pedaling — one crank pushing down while the other pulls up — at the 1,000N to 1,200N force levels specified per bicycle category. This is not a simple push-pull test on a single point; it is a dual-actuator, phase-controlled simulation of the actual pedaling load cycle applied through the standard crank geometry.

Overview of the FH-CJ2010 Test Machine

The FH-CJ2010 is a dual-servo-cylinder bottom bracket pedaling fatigue tester for bicycle frames, built to execute ISO 4210-6.4.3 and the equivalent clauses in EN 15194 and the European category standards (EN 14764, EN 14766, EN 14781) as well as nine national standards including JIS, CPSC, and DIN.

Two 5,000N disc-type force sensors with independent electric servo cylinders apply opposing sinusoidal forces through 175mm replacement cranks. The cranks are set at 45° to each other (±2° tolerance) in the horizontal plane — the geometry specified in ISO 4210-6.4.3 — so that when one crank arm is loaded downward, the opposing crank is simultaneously unloaded, replicating the phase-offset of real left-right pedaling. The vertical position of each crank load application point is 75mm from the bottom bracket spindle center (Rc), with horizontal offset 50mm from the frame centerline to the rear axle spindle connection.

The machine uses closed-loop force control — both channels monitored independently in real time and servo-adjusted to maintain the programmed sinusoidal force amplitude throughout the test. The proprietary Feihong software displays force-time and displacement-time curves for both channels simultaneously, with real-time peak force, displacement amplitude, cycle count, standard deviation, and average value readouts visible during the run.

One run encompasses 100,000 cycles, where each cycle consists of two force applications — one per crank — giving a total of 200,000 individual force events per test. Maximum frequency is 0–5Hz per ISO 4210-6 clause 4.5.

Standards Covered: ISO 4210-6.4.3, EN 15194 and Nine National Standards

Primary International and European Standards

National Standards Coverage

Force Values by Bicycle Category (ISO 4210-3:2014, Table 3)

Per Table 3 — Forces applied to pedals (ISO 4210-3:2014, clause 4.5):

Note on EPAC: EN 15194 references ISO 4210-6 for pedaling fatigue, and the applicable force value depends on the bicycle base category (city, mountain, etc.) the EPAC is derived from. For most EPAC city models, F1 = 1,000N; for mountain EPAC, F1 = 1,200N.

The FH-CJ2010's 5,000N sensor capacity and closed-loop control system cover all four force levels — from 1,000N city/children's frames to 1,200N mountain bike frames — on the same machine without reconfiguration.

Test Methods, Force Values, and Setup Geometry

Crank Replacement and Mounting (ISO 4210-6.4.3)

Two 175mm replacement cranks are installed in the bottom bracket in place of the production crankset. The cranks are adjusted front-to-back so that they are at 45° to each other in the horizontal plane (tolerance ±2°). This offset angle reproduces the phase relationship of actual pedaling — the two cranks are not 180° opposed (as in a normal crankset) but set at the 45° angle specified in the standard, producing a different bending moment distribution at the bottom bracket shell.

The vertical load application point on each crank is at Rc = 75mm from the bottom bracket spindle center. The horizontal offset from the frame centerline to the rear axle spindle connection is 50mm. The rear axle spindle is connected to the rear axle base at right angles to the vertical line — matching the fixture geometry in the ISO 4210-6 test diagram.

Frame Mounting

The frame is fixed with:

• Front axle (point A): Pinned to the bench — allows rotation but not translation

• Rear axle (point B, point 1): Fixed to the rigid rear support — Rw reaction

• Head tube area (point C): Constrained vertically at the top of the test diagram

The front and rear axle supports provide the Rw reaction forces shown in the test diagram, while the bottom bracket receives the cyclic F1 load through the replacement cranks.

Load Application and Waveform

Forces are applied as a sinusoidal waveform — not a square wave or triangular wave. Sinusoidal loading is specified in ISO 4210-6 because it most closely replicates the smooth force variation of actual pedaling and avoids the high-frequency harmonic content of non-sinusoidal waveforms that could introduce non-standard fatigue damage mechanisms.

The two servo channels operate in dual-channel reverse mode — when Channel 1 (left crank) is at its positive force peak, Channel 2 (right crank) is at or near its negative (unloaded) position, replicating the phase relationship of alternating left-right pedaling. As visible in the software screenshot, the two force curves are approximately sinusoidal and phase-offset, maintaining stable amplitudes throughout the run.

Test Cycle Count

100,000 cycles total. One cycle consists of two force applications — one per crank arm. The machine runs to 100,000 cycles (200,000 individual force events) or stops automatically on specimen failure or out-of-spec load condition.

Pass Criteria

No fracture, crack, or permanent deformation at the bottom bracket shell, chainstay welds, seat tube junction, or any other frame structural location after the full 100,000-cycle count.

Design Features of the FH-CJ2010

Dual 5,000N Disc-Type Force Sensors — 1/10,000 Resolution

Two independent 5,000N disc-type load cells monitor the applied force on each crank channel simultaneously. At 1/10,000 resolution, force measurement increments are 0.5N at full scale — providing the measurement granularity needed to detect load drift or waveform distortion during long fatigue runs, not just at the beginning of the test.

Closed-Loop Force Control on Both Channels

Both servo channels operate in full closed-loop force control — the commanded force setpoint is compared to the actual load cell output at >200kHz acquisition rate, and the servo cylinder command is adjusted in real time to maintain the sinusoidal waveform at the programmed amplitude. This is the critical feature that distinguishes a force-controlled fatigue machine from a displacement-controlled one: the actual stress applied to the frame matches the standard specification regardless of frame stiffness, joint compliance, or thermal effects over the 100,000-cycle run.

>200kHz Force Acquisition Rate

The high-speed data acquisition card samples both force channels at greater than 200kHz — more than 40,000 samples per waveform cycle at 5Hz, and over 4 million samples per waveform at 0.05Hz for low-frequency runs. This acquisition rate ensures that peak force values and waveform distortion are captured accurately, not smoothed over by undersampling.

Sinusoidal Force Waveform

The standard specifies sinusoidal loading. The FH-CJ2010's servo control system generates a sinusoidal force command — not a displacement-controlled approximation — using the load cell feedback to maintain waveform fidelity throughout the test run. The software screenshot shows the characteristic smooth, stable sinusoidal curves on both channels across the full cycle range.

Automatic Stop on Out-of-Spec Load or Specimen Failure

Two automatic stop conditions protect both the machine and the test integrity:

• Load falls below setpoint: Indicates specimen fracture or fixture loosening — machine stops and records the cycle count at failure

• Load cannot be reached: Indicates actuator saturation or mechanical anomaly — machine stops before the test produces non-standard results

Proprietary Feihong Test Software

The FH-CJ2010 runs Feihong's own test software — not a third-party system. The software provides:

• Real-time force vs. time curves for both channels (sinusoidal display)

• Real-time displacement vs. time curves for both channels

• Real-time peak force and displacement amplitude readouts

• Force vs. cycle count and displacement vs. cycle count trend charts

• Cycle counter with elapsed percentage display

• Standard deviation and average value calculation

• Test result report generation and export

As visible in the software screenshot: Channel 1 Force = 473N, Displacement = 1.98mm; Channel 2 Force = 389N, Displacement = 1.45mm — dual-channel reverse sinusoidal waveforms running stably at 383 completed cycles in the screenshotted run.

Optional Fixture Set — Four Test Configurations

The FH-CJ2010 can be configured for four different fatigue test types by changing the fixture:

1. Frame bottom bracket pedaling fatigue fixture — the standard configuration for ISO 4210-6.4.3

2. Front fork fatigue fixture — front fork bending and impact fatigue tests

3. Handlebar fatigue fixture — handlebar and stem fatigue per ISO 4210-5

4. Saddle fatigue fixture — saddle and seatpost fatigue testing

This fixture optionality means a lab investing in the FH-CJ2010 can use the same servo actuation platform and control system for multiple component fatigue test types — reducing total equipment cost compared to purchasing separate machines for each fixture type.

Technical Specifications of the FH-CJ2010

Test Parameters

Servo and Sensor System

Crank Geometry (ISO 4210-6.4.3)

Physical

Why These Specifications Matter

• Dual 5,000N sensors at 1/10,000 resolution give 0.5N measurement increments on a 1,000–1,200N test load — sufficient to detect a 0.05% force deviation from setpoint. For fatigue testing where the standard specifies exact force values, this resolution ensures that the actual applied load is documentably within specification, not just nominally correct.

• >200kHz acquisition rate means even at 5Hz test frequency, each sinusoidal waveform cycle is sampled over 40,000 times. Waveform distortions (clipping, harmonics, phase error) that would indicate actuator saturation or control instability are detected immediately — not after a completed test run.

• ±75mm stroke covers the deflection range of frames at 1,200N mountain bike load without reaching actuator end-of-travel. Stroke saturation clips the sinusoidal waveform and turns it into a square-wave-approximating load — non-standard and mechanically more damaging than the specified sinusoidal profile.

• 175mm crank / 45° angle are not arbitrary design choices — they are the exact values in ISO 4210-6.4.3. Using standard-length replacement cranks at the standard angle ensures the bending moment applied to the bottom bracket shell matches the standard specification. Non-standard crank lengths or angles change the moment arm and produce non-representative fatigue loading.

How the FH-CJ2010 Testing Process Works

Step 1: Frame Mounting

The frame is mounted in the fixture with front axle pinned at point A, rear axle fixed at point B/1 (Rw supports), and the head tube area constrained at point C. The rear axle spindle is connected at right angles to the vertical line.

Step 2: Crank Installation and Angular Alignment

175mm replacement cranks are inserted into the bottom bracket and adjusted to the 45° relative angle (±2° tolerance). The vertical force application point is set at Rc = 75mm from the spindle center. The horizontal offset to the rear axle spindle connection is confirmed at 50mm from the frame centerline.

Step 3: Test Parameter Entry

Force setpoint (1,000 / 1,100 / 1,200N per bicycle category), frequency (0–5Hz), cycle count (standard: 100,000), and waveform (sinusoidal) are entered. Both servo channels are confirmed in closed-loop force control mode, dual-channel reverse phase.

Step 4: Test Execution and Real-Time Monitoring

The test begins. The software displays real-time force-time and displacement-time curves for both channels — sinusoidal waveforms running in reverse phase. Peak force, displacement amplitude, and cycle count are updated continuously. Force vs. cycle trend and displacement vs. cycle trend charts update throughout the run.

Step 5: Automatic Stop and Inspection

The machine stops automatically at the programmed cycle count or on load drop-out indicating specimen failure. All data is auto-saved. The frame is inspected at the bottom bracket shell, chainstay welds, seat tube junction, and surrounding regions for fracture, crack, or permanent deformation.

Step 6: Report Generation

Test results — force curves, cycle count, peak values, standard deviation, average — are compiled into a report in the operator-configured format and saved for QC documentation or certification submission.

Benefits for Frame Manufacturers and Testing Labs

Third Test Axis for Complete ISO 4210-6 Frame Compliance

ISO 4210-6 requires three independent frame fatigue tests — horizontal dropout (6.4.4), vertical seat tube (6.4.5), and bottom bracket pedaling (6.4.3). The FH-CJ2010 completes the third test axis that the FH-CJ052 does not cover, giving manufacturers the full three-test suite needed for type approval.

Closed-Loop Force Data for Certification Documentation

Multi-Fixture Platform — Four Test Types on One Machine

Laboratories running frame, fork, handlebar, and saddle fatigue tests can configure the FH-CJ2010 for all four by changing the fixture — using the same servo platform, control system, and software interface. This is more capital-efficient than purchasing four separate single-function machines.

Category-Specific Force Configurations — No Recalibration Between Categories

Switching from a 1,000N city-bike test to a 1,200N mountain-bike test requires only changing the force setpoint in software — not replacing sensors, actuators, or fixtures. The 5,000N sensor capacity covers all four force values with ample headroom, and closed-loop control adjusts the servo output automatically to the new setpoint.

Choosing the Right Bottom Bracket Pedaling Fatigue Tester

Dual-Channel vs. Single-Channel Actuation

ISO 4210-6.4.3 specifies two cranks at 45° phase offset, with forces applied to both simultaneously in reverse phase. A single-actuator machine cannot reproduce this — it can only apply force at one crank at a time, producing a different bottom bracket stress distribution that does not match the standard loading condition. Confirm that any machine considered for ISO 4210-6.4.3 compliance has two independent servo channels operating in reverse-phase mode.

Force Control: Closed-Loop vs. Displacement Control

As with all ISO 4210-6 frame fatigue tests, the standard specifies force, not displacement. A displacement-controlled machine estimates the applied force from a spring-stiffness model of the frame — an approximation that degrades as frame compliance changes with temperature, fatigue damage progression, or joint relaxation over 100,000 cycles. Closed-loop force control eliminates this uncertainty.

Acquisition Rate and Waveform Fidelity

At 5Hz test frequency, a 1kHz acquisition rate gives only 200 samples per waveform cycle — insufficient to detect clipping or harmonic distortion. The FH-CJ2010's >200kHz rate provides >40,000 samples per cycle, ensuring waveform quality is monitored continuously.

Crank Geometry Compliance

Verify that the replacement cranks are exactly 175mm in length and that the fixture achieves the 45° ±2° crank angle specified in ISO 4210-6.4.3. Non-standard crank geometry changes the applied bending moment and produces non-representative fatigue loading, regardless of how accurate the force control is.

Real-World Application Scenarios

A mountain bike frame manufacturer testing a new hydroformed bottom bracket design ran ISO 4210-6.4.3 pedaling fatigue tests at 1,200N on both the new design and the previous forged shell design. The dual-channel real-time curves revealed an asymmetric displacement response in the new design — indicating torsional stiffness difference between left and right chainstay welds — that was not visible in static load tests. The weld bead profile was adjusted before certification submission.

An EPAC manufacturer preparing EN 15194 certification used the FH-CJ2010 with the frame pedaling fixture for the ISO 4210-6.4.3 test and then reconfigured the same machine with the handlebar fixture to run the handlebar fatigue test in the same week — using a single machine for two of the required certification tests, reducing the certification preparation timeline.

A testing laboratory serving multiple small-volume frame brands used the four optional fixtures to qualify frames, front forks, handlebars, and saddle posts on a single machine, reducing equipment investment while maintaining coverage across all major ISO 4210-6 component fatigue test requirements.

FAQs for the FH-CJ2010 Bottom Bracket Fatigue Tester

Why are two servo cylinders needed for the bottom bracket fatigue test?

ISO 4210-6.4.3 specifies two replacement cranks set at 45° to each other, with forces applied to both in reverse phase — when one crank is loaded, the other is simultaneously at its unloaded position. This requires two independent actuators operating in synchronized reverse-phase mode. A single actuator cannot replicate this loading geometry.

What does "one cycle consists of two force applications" mean?

Each cycle in ISO 4210-6.4.3 includes one downward force application via the left crank and one via the right crank. The 100,000-cycle count therefore represents 200,000 individual force events — 100,000 on each side — replicating what happens during 100,000 complete pedaling rotations.

Why are the cranks set at 45° and not 180° like a normal crankset?

ISO 4210-6.4.3 specifies 45° specifically because this angle produces a different — and more conservative — bending moment distribution at the bottom bracket shell than the standard 180° riding position. The 45° configuration was derived from analysis of the force distribution that produces the highest stress at the critical weld locations.

What force values apply for EPAC frames?

EN 15194 references ISO 4210-6 for pedaling fatigue. The applicable force depends on the base bicycle category: city EPAC = 1,000N; mountain EPAC = 1,200N. Confirm the specific category classification with your certification body.

Can the machine test front forks, handlebars, and saddles as well?

Yes, with optional fixture changes. The FH-CJ2010 base machine (servo platform, control system, software) supports four test configurations: frame bottom bracket pedaling, front fork fatigue, handlebar fatigue, and saddle fatigue.

What does the automatic stop function do?

Two conditions trigger automatic stop: (1) measured force drops below the setpoint — indicating specimen fracture or fixture failure; (2) force cannot reach the setpoint — indicating actuator saturation or mechanical anomaly. Both conditions stop the machine immediately and record the cycle count at the stop event.

How is the test frequency related to the cycle count?

Test frequency (0–5Hz) is the number of complete force cycles per second. At 5Hz, 100,000 cycles completes in approximately 5.6 hours; at 3Hz it takes approximately 9.3 hours. The frequency selection is constrained by ISO 4210-6 (maximum 5Hz per clause 4.5) and by the requirement that the servo system maintain accurate sinusoidal force control throughout — higher frequency requires more servo bandwidth and typically produces slightly higher force error.

Related Testing Equipment

• Bicycle Frame Vertical & Horizontal Fatigue Test Machine (FH-CJ052) — covers ISO 4210-6.4.4 (horizontal dropout, 600N / 100,000 cycles) and ISO 4210-6.4.5 (vertical seat tube, 1,100N / 50,000 cycles); complements the FH-CJ2010 to complete the full ISO 4210-6 three-test frame fatigue suite

• Bicycle Frame Vertical Vibration Test Machine (FH-S2989) — vertical vibration fatigue per ISO 4210-6, JIS D9401, GB 17761; 6–10Hz, 85kg load

• Bicycle Fork Impact Test Machine — drop-weight front fork impact testing per ISO 4210-6

• Electric Bicycle Comprehensive Test Machine (FH-ZD2988) — performance, speed, and braking testing per EN 15194, ISO 4210, GB 17761

Get a Quote from Feihong Machine

Feihong Machine (Dongguan Feihong Instrument and Equipment Co., Ltd.) designs and manufactures bicycle frame and component fatigue testing equipment for manufacturers and testing laboratories worldwide.

To get started:

• Request a Quote — share your frame category, target force value, and standards required

• Request Technical Datasheet — full dimensional drawings, sensor calibration data, and software manual

• Schedule a Demo — see the FH-CJ2010 run a live ISO 4210-6.4.3 pedaling fatigue test with dual-channel real-time curve display

Request a Quote →