Nord-Lock: The simple way to make wheels safe
Why Wheels Loosen
The driver is usually not the problem
Conventional wheel nuts do not have a locking feature and can therefore rotate loose. However, the blame for wheel nut loosening and wheel detachments is normally - and unfairly - placed on the driver and/or the vehicle owner.
Main reason for wheel nut loosening
Wheel nut loosening is caused by one or more of the following factors:
- Poor road conditions
- Vibration
- Poor tightening technique or tools
- Joint relaxation
- Braking and accelaration
- Human errors during assembly
- Thermal expansion and contraction of wheel studs
- Unbalanced wheels
- Increased vehicle speed and capacity
- Oil leakage from axel onto wheel nuts without locking function
Safe wheel assemblies rely on high clamp load. Loss of clamp load leads to movement between the clamped parts in the joint, and causes rotation of the wheel nut. The Nord-Lock wheel nut safely secures wheels on heavy vehicles by mainatining high clamping force even under extreme operating conditions.
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A Widespread Problem
On road
In the United Kingdom alone there are up to 400 wheel detachments from heavy trucks every year. Of these, on average, there are 134 accidents involving vehicle/property damage, 27 injuries and up to 7 fatalities. So states a 2006 report commissioned by the United Kingdom Department for Transport. In the United States of America, the National Transportation Saftey Board reports that wheel detachments occur at an estimated rate of 1,000 per year - almost three a day - resulting in about 20 accidents per week. In other countries, wheel loss occurs at comparable rates.
Off road
Statistics for off-road vehicles tell a similar story. Off-road accidents involving dislodged wheels result in damaging of indutrial equipment, personal injuries and, even worse, fatalities. According to a 2008 report from the U.S. Bureau of Labor Statistics, entitled Census of Fatal Occupational Injuries, 2,053 workers died in vehicle-related crashes and transportation incidents. According to their earlier reports, wheels and tyre rims caused fatalities to 85 workers from 1992 to 2002, an average of 8.5 such fatalaties per year over that period. Wheel detachment is one of the possible causes of such accidents.
Main cause of wheel detachment
Loose wheel nuts are the primary cause of wheel detachment from heavy vehicles. This puts safety at risk as a dislodged wheel barreling down the highway strikes with a devastating force. See actual footage of this safety problem.
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Consequences
Wheel nut loosening is caused by one or more of the following factors:
- Dislodged wheels
- Accidents resulting in property damage and personal injury
- Jeopardized productivity and delivery precision due to:
- Greater risk of unplanned stops
- Greater retightening demands
- Increased costs due to the effects of unbalanced wheel
- Higher fuel consumption
- Increased tyre wear
- Higher spare parts costs, due to increased wear on the wheel assembly
- Increase operational costs from damage repair and possible fines or insurance claims
- Negative company publicity resulting from poor safety record and performance below expectations
The Nord-Lock wheel nut offers a safe-locking, which makes it possible to avoid the above listed consequences of loosening wheel nuts.
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The Nord-Lock Wheel Nut
How does it work?
The Nord-Lock wheel nut safely secures wheels by maintaining high clamping force even under extreme operating conditions. Each nut incorporates a pair of captivated washers with cam faces on one side, with a cam angle ''a'' greater than the thread pitch ''ß''. On the opposite side there are radial teeth. When the nut is tightened, the teeth of the Nord-Lock washers grip and lock the mating surfaces, allowing movement only across the cam faces. Any rotation of the wheel nut is blocked by the wedge effect of the cams.
The Nord-Lock wheel nut is based on Nord-Lock''s unique wedge-locking technology, which uses tension instead of friction to secure bolted joints. The system has been used for over 25 years to ensure the structural security of bolted applications exposed to strong vibrations and high dynamic loads.
Safe wheels save lives and keep heavy vehicles at work
Heavy vehicles are all around us. From the commercial bus or truck delivering people or valuable goods, to the tractor preparing earth to grow new crops, and to industrial vehicles operating on infrastructure projects. It is important that every aspect of a heavy vehicle is totally safe and reliable. By eliminating unintentional wheel nut loosening, it enables vehicle operators to:
- Improve safety:
- Once tightened it can''t be loosened
- Prevents accidents normally caused by loosening wheel nuts
- Makes streets, highways and work sites safer
- Secure productivity:
- Decreases need for retightening and, the risk of unplanned stops
- Increases efficiency of on-road vehicles (e.g. reduced delivery time)
- Increases onsite productivity (e.g. reduced maintenance downtime)
- Improve profitability:
- Decreases premature wear of tyre and wheel assemblies
- Decreases fuel consumption caused by unbalanced wheels
- Increases cost efficiency of operations (e.g. reduced spending on spare parts, fines and insurance claims)
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Proven in Tests
The performance of the Nord-Lock wheel nut has been proven in a rigorous three step test program:
1. Laboratory testing (Independent comparative testing)
At the IMA independent facitility for engineering service is Dresden, Germany, the Nord-Lock wheel nut was subjected to severe vibration testing according to the DIN 651 51 standard (Junkers test). The testing also compared the funstion of the Nord-Lock wheel nut against other wheel nut products. The test results clearly show its superior safety. The Nord-Lock wheel nut performed flawlessly even after being reused multiple times.
The graphs display the products tightened to 200 kN and the change in clamp load during 1000 load cycles. The conventional wheel nut rotated and lost most of its initial clamp load in the joint. The Nord-Lock wheel nut safely secured the wheel joint and maintained the clamp load. Only initial settlements are indicated in the graph.
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2. Extreme operating conditions test
On Road
Extreme operating conditions tests involving an on-road vehicle were performed on track at RDW''s Test Center in Lelystad in The Netherlands. The tests involved the wheel joints of a 3-axle extended trailer being secured with Nord-Lock wheel nuts. The truck was driven in both directions on the tyest center''s oval track with concave, banked curves in order to exert the same stress on all wheel joints. The Nord-Lock wheel nuts were not retightened after 100km of driving in order to simulate human error in combination with a worst case driving scenario.
Test vehicle data:
|
|
| Trailer: |
NBT, 3-axel bogie by BPW, (adapted for forklift) |
| Truck: |
Scania R380 |
| Vehicle total weight: |
45 000 kg |
| Tires: |
Michelin
|
| Rims: |
Michelin steel rims
|
| Corner speed at test: |
86 km/h
|
Track specifications:
|
|
|
| Length of test track: |
2850 m
|
71/320/EEC
|
| Curve radius: |
160 m
|
ECE R13/R13H
|
| Curve gradients: |
5%, 30% and 60%
|
ECE R39
|
| Maximum axle load: |
15 000 kg
|
ECE R78
|
| Friction coefficient: |
|
|
| Longitudinal gradient: |
0%
|
|
Off Road
For the extreme operating conditions test involving an off-road vehicle, the wheel joints of an 8-wheeled truck were secured with Nord-Lock wheel nuts. During these tests, the following maneuvers were performed to maximize the load on the axles and wheel joints.
- Driving at accelerated speeds over boulders until failure of the vehicle or wheel nut loosening.
- Entire vehicle weight was carried by: the rear axle only, the front axle only, and each side.
- Vehicle slid down the hill repeatedly
Test vehicle data:
|
|
| Truck: |
Man TGS 35.480
|
| Power output: |
600 bhp
|
| Gears: |
32 gears
|
| Drive chain: |
8-wheel drive with all axles lockable
|
Results
There was no signs of wheel nut loosening. The Nord-Lock wheel nut safely secured the wheel joints even under severe on- and off-road conditions.
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3. Normal operating conditions test
On road
In order to definitvely determine the functionality of the Nord-Lock wheel nut, it was tested on real life vehicles in real life service. During the first 100km of driving and retightening a safety car followed the truck. In the on-road test the LCW truck tested at RDW in Lelystad was used for transport services for 7000 km without detecting any rotation of the wheel nuts. The vehicle was driven on an even mix of highway and urban roads.
Off road
The off road test was performed inolving a military vehicle in desert environment. The trailer was fitted with the Nord-Lock wheel nut on one side of the axles and regular wheel nuts on the other. The vehicle was driven fully loaded at maximum speed during a service period of three months. None of the Nord-Lock wheel nuts had rotated.
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Technical Specifications
| Thread |
Key width W
|
Diameter Ø
|
Height H
|
Tightening torque
|
Clamp load
|
M22x1.5
|
32 mm
|
46 mm
|
27 mm
|
600-650 Nm
(450-500 ftlb)
|
~200 kN
(~45000 lb)
|
For flat-faced steel rims
The Nord-Lock wheel nut is designed for use on flat-faced steel rims. Sliding always occurs between the nut and the upper washer during tightening, and between the cam faces during untightening. In this way, clear impression marks are created without scoring the contact surface. Upon reuse, the serrations find their way back into the previously created impressions.
Technical specifications:
|
|
| Surface coating: |
Basecoat Delta Protekt KL 100, Topcoat VH 302 GZ
|
| Corrosion resistance: |
600 hours according to ISO 9227
|
Thread tolerance
after coating: |
6H
|
| Lubrication: |
Anti-corrosive wax
|
| Property class: |
Grade 10
|
Premium quality
The Nord-Lock wheel nut is a Swedish product manufactured from high-quality steel. The product is prelubricated to ensure uniform friction and thereby accurate preload during tigtening. The lubrication also inhbits corrosion which facilitates disassembly and helps prolong the life of wheel studs. The Nord-Lock wheel nut is reusable and durable.
Full traceability and environmental compliance
Each Nord-Lock product is supplied with a control number, enabling full traceability. Nord-Lock is also a proud holder of the ISO 9001 and ISO 14001 certifications. The Nord-Lock wheel nut is in full compliance with EU directive 2000/53/EC on End of Life Vehicles (ELV) and EU directive 2002/95/EC on the Restriction of the use of certain Hazardous Substances in electrical and electronic equipment (RoHS).
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Assembly Instructions
Standard routines, simple installations
- Place the rim over the wheel hub. Endure the wheel studs are not damaged
- Fit and tighten the nuts with a calibrated torque wrench at the recommended torque, in the sequences illustrated here
- Retighten the nuts after 100km / 50 miles of driving
Easy maintenance
Before reuse, inspect the nuts and wheel studs to make sure that the threads are free from particles and are undamaged. Re-lubricate the nuts before reuse.
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About Nord-Lock
When safety really matters
Nord-Lock bolt securing systems are designed to secure fasteners in extreme conditions. Nord-Lock have over 25 years of experience of collaborating with our customers to achieve effective bolt security. We will help you optimize your bolted joints in order to minimize overall cost and maximize safety.
Nord-Lock''s premium bolt securing systems give effective security throughout an assembly''s lifetime, resulting in:
- No bolt loosening caused by vibration and dynamic loads
- Minimized cost of maintenance, repair and overhaul
- Significantly reduced risk of lost production or operation due to bolt failure
Go to the Nord-Lock microsite.
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