Crash Channels Record Newtons, Protocols Quote Kilonewtons
A frontal impact lasts about 120 milliseconds and produces a wall of data: load cells in the dummy's femurs, neck, tibiae and pelvis, plus belt tension transducers, all sampling thousands of times a second and all writing raw newtons. The rating protocol that decides whether the car scores well is written the other way round — in tidy kilonewton thresholds. Somewhere between the acquisition file and the assessment sheet, every peak has to be divided by a thousand.
Why the Numbers Get So Large So Quickly
Deceleration multiplies everything
Only the peak becomes a score
Two families of number in one report
A restraint is tuned, not maximised
Working a Channel Peak Into a Report Line
The conversion sits between reading the trace and writing the assessment, so it happens dozens of times per test.
Paste the peak value in newtons
Type or paste a figure such as 3 812 into the left field; the kilonewton value appears immediately. Spaces inside the number are ignored and a comma is accepted as the decimal mark, so exports from either locale drop straight in.
Reverse it to check against a protocol threshold
Protocol tables give kilonewtons. Hit the swap button (↔), enter 3.8, and you get the 3 800 N the acquisition system would have logged — the form the raw channel is in.
Reach for other units when the source is imperial
US test reports and older supplier data sometimes carry pound-force. Both dropdowns are searchable and list every force unit the app knows, so a newton figure can be read out as lbf without leaving the page.
Copy the plain value into the sheet
The copy button hands over the bare number with no unit attached, which is what a results spreadsheet or a homologation form wants in the cell. Ctrl + C in a field does the same thing.
Frontal-Impact Force Values in Both Units
Representative figures from occupant-protection work, shown as the channel records them and as the protocol writes them. Exact values differ between test houses, protocol versions and dummy sizes.
| Measurement or test | Newtons | Kilonewtons | What it represents |
|---|---|---|---|
| Tibia axial compression, good performance | 2 000 N | 2 kN | Lower-leg loading a footwell should stay under |
| Neck axial tension, upper boundary | 3 300 N | 3.3 kN | Where neck tension stops counting as acceptable |
| Femur axial compression, good performance | 3 800 N | 3.8 kN | Knee-thigh-hip loading target in assessment |
| Belt load limiter, first stage | 4 000 N | 4 kN | Plateau the shoulder belt pays out at |
| Belt load limiter, stiffer setting | 6 000 N | 6 kN | Used for larger occupants or a second stage |
| ISOFIX low anchorage, static pull | 8 000 N | 8 kN | Forward force the child-seat anchorage must hold |
| Femur axial compression, capping value | 9 070 N | 9.07 kN | Beyond this the score is capped regardless of the rest |
| Femur limit, US federal rule | 10 000 N | 10 kN | Pass/fail ceiling for the mid-size male dummy |
| Belt anchorage, body-block test | 13 500 N | 13.5 kN | Static load the anchorage and its surroundings must take |
The spread across the table is the interesting part. Everything the occupant experiences sits between 2 and 10 kN, while the structure behind them is proved at 13.5 kN and more — the seat, the pillar and the floor are made deliberately stronger than anything a body could survive, so that failure never happens on that side of the system.
What Makes This Practical in a Test Lab
Channel peaks convert as fast as you can paste
Both fields update live, so a run of femur, tibia and neck peaks can be worked through one after another without a single click.
Small values keep their resolution
Results carry up to eight decimals, so a 312 N pre-tensioner reading does not collapse to 0.3 kN when you need 0.312.
Threshold-to-channel direction in one press
Swap turns a protocol limit written in kilonewtons back into the newton value you would look for on the trace.
Clean cells for the results sheet
Copy yields the number alone, so nothing has to be stripped out before it lands in a spreadsheet column or a report template.
Restraint and Injury-Load Questions
What is a seat belt load limiter actually limiting?
The tension in the shoulder belt, and with it the force pressed into the chest. Inside the retractor sits a torsion bar that twists once the belt load reaches a set value — often around 4 000 N — letting webbing pay out at a roughly constant force instead of holding rigidly. The occupant travels a little further forward, but the load curve flattens into a plateau rather than spiking. On a trace it is unmistakable: a rise, then a long flat section sitting almost exactly on the design figure. Two-stage designs hold high briefly, then drop to a lower plateau once the airbag is available to share the job.
Why is the anchorage test load so much larger than the load a belt puts on a person?
Because the two numbers answer different questions. The 13 500 N body-block pull is a proof test of the structure: it has to cover the heaviest occupant, the most severe crash the rule contemplates, manufacturing variation and years of service, and it is applied slowly through a rigid block rather than dynamically through a chest. The 4 000 N a limiter allows into a real occupant is a tuned figure aimed at the least injury. Structure is deliberately over-specified relative to the body, so if anything gives way it is the deformable parts, never the anchorage.
Why do the raw channels stay in newtons if everything is reported in kilonewtons?
Because that is the unit the instrumentation standards define and the acquisition chain carries end to end. A load cell has a sensitivity in millivolts per newton, its calibration certificate is in newtons, and the channel is stored in newtons so the file is unambiguous whoever opens it. Kilonewtons only appear at the last step, where humans read the result and a four-figure number becomes an easier one-decimal figure. Keeping the raw data in the smaller unit also avoids rounding: 3 812 N is exact, while 3.8 kN has already thrown away twelve newtons.
Why are the left and right femur recorded as separate channels?
Because a frontal crash is rarely symmetrical, and the assessment takes the worse of the two. The steering column, the pedal box, the footwell intrusion and the knee-airbag coverage are all different on each side, so one leg can meet the dash squarely while the other slides. It is common to see several thousand newtons of difference between the two channels in the same test. Reporting only an average would hide exactly the loading a knee bolster is meant to prevent, so both are logged, converted and scored, and the higher figure drives the result.
What is the difference between a performance limit and a capping limit?
A performance limit is where full points stop: stay under roughly 3.8 kN of femur compression and that body region scores everything available, and points are then lost progressively as the value climbs. A capping limit is a hard ceiling with a different consequence — exceed it, around 9.07 kN on the same channel, and the score for that part of the assessment is cut regardless of how well every other measurement went. The gap between the two is the sliding scale, so a value of 6 000 N is neither a pass nor a failure but a partial score, which is why the exact converted figure matters rather than a rounded one.
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