GB/T 20456-2023 Portable chain-saws - Non-manually actuated chain brake performance
1 Scope
This document specifies the performance requirements and test method of the non-manually actuated chain brake on an electric or gasoline engine powered, portable hand-held chain-saw.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 6531 Machinery for forestry - Portable chain-saws -Vocabulary
Note: GB/T 18960-2023 Potable china-saws - Vocabulary (ISO 6531 : 2017, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 6531 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
- ISO Online browsing platform: available at https://www.iso.org/obp
- IEC Electropedia : available at http://www.electropedia.org/
4 Performance requirements
The non-manually actuated chain brake function shall be checked on a new normal production saw equipped with the shortest and longest guide bars specified in the instruction handbook, but no longer than 500 mm. If the guide bar is not less than 500 mm, only the specified shortest guide bar shall be used for testing. Battery-powered chain saws with several recommended battery pack options shall be checked according to the lightest battery pack and the shortest guide bar, the heaviest battery pack and the longest guide bar configuration.
When tested in accordance with Clause 8, the performance of the actuation function of a non-manually actuated chain brake is considered acceptable if each of the horizontal and vertical acceleration levels (ax and ay) at which the chain brake actuates is below the appropriate threshold level as shown in Figure 1 a), b) or c) for different chain-saw types and sizes.
5 Principle
The chain-saw shall be mounted on a test rig as shown in Figure 3. The drop mass falls from a defined height on the rocker and accelerates the chain-saw on the opposite side. The drop height shall be increased until the actuation of the non-manually actuated chain-brake occurs.
6 Test equipment
6.1 Acceleration measuring equipment
The total mass of the accelerometer(s) shall be as low as possible and shall not, in anycase, exceed 50 g, including the mounting, but excluding the cables.
The signal from the accelerometer(s) shall be processed by a low-pass filter having characteristics in accordance with Annex A.
Care shall be taken when mounting the accelerometer(s) so that the transfer function is flat up to 300 Hz in both measuring directions. For general considerations concerning accelerometer mounting, see ISO 5348. The transfer function may be considered flat if an addition of mass to the accelerometer, equal to that of the accelerometer itself, does not have any significant influence on ax and ay. This additional mass shall be placed between the accelerometer and its mounting if the mass is of metal, or around the accelerometer if the mass consists of materials such as clay or wax.
The accuracy of the measuring equipment, excluding accelerometer mounting and filter, shall be ±5% of the registered value in the frequency range from 0 Hz to 300Hz. See ISO 16063-1 for calibration methods.
6.2 Test rig
The design principles of the test rig shall be as shown in Figure 3.
The test rig shall be mounted solidly to the floor and designed so that deflection of the drop mass guide rod is restricted, e.g. by fixing both ends.
The guide rod shall be vertical within 2°.
The top surface of the steel spacer shall be horizontal within 1° in the lateral direction.
Both the length of the test rig cord and the longitudinal and lateral positioning of the pivoting pulley for the cord shall be adjustable.
The test rig rocker shall be made of rectangular hollow section steel, 80 mm×40 mm×4 mm, and shall have a mass of 6700g ± 300 g and a moment of inertia of 0.45 kg·m2±0.02 kg·m2.
The drop weight device shall have a drop mass of 15000 g ± 20 g. It shall be possible to select drop heights in steps of 10 mm or less, at least for drop heights between 200 mm and 1400 mm. The accuracy of the drop height shall be ±2 mm.
The dimensions of the spring between the drop weight and the rocker arm shall be such that a pulse length (ty) of 11 ms ± 2 ms is achieved.
ty shall be measured as the time of positive acceleration ay of the initial pulse, i.e. from the moment when ay increases from zero to the first time ay returns to zero. See example in Figure 2.
The spring defines the length and the characteristic of the impulse.
Note: The specified pulse length can be achieved by using seven conical disc springs (45 mm × 22.4 mm × 1.75 mm), with a characteristic of 640 N/mm ± 20 N/mm, each having an adverse orientation in relation to the next one.
If conical disc springs are used, they should be positioned and guided as precisely as possible. The diametrical play between the drop mass guide rod and the inner diameter of the conical disc springs should be 0.4 mm to 0.8 mm.
7 Preparation
Prepare the chain-saw for testing as follows.
a) Check that the chain-saw is in accordance with the product specification.
b) Precondition the saw by actuating the non-manually actuated chain brake ten times —for example, by dropping the saw while holding the rear handle, so that the bar tip hits a rigid, wooden surface.
c) Mount a saw-chain suitable for the guide bar and cut softwood for the time it takes to use one tank full of fuel at approximately maximum power speed (gasoline engine powered chain-saws) or for the time it takes to use one tank full of chain oil (electric-powered chain-saws). The chain brake shall not be activated during this cutting. Do not clean the chain-saw after cutting. Remove the chain with minimum disassembly and disturbance. The guide bar used for the cutting may also be, with minimum disturbance, replaced by a comparable, unused, guide bar having the same characteristics (i.e. length, bar nose radius, gauge).
d) Set the chain tension adjuster to its middle position and move the guide bar to its uppermost position, in order to eliminate play. Fasten the guide bar on the saw. The saw chain shall not be installed and the tanks shall be empty. The throttle trigger or power switch (for electric-powered chain-saws) shall be set to its fully activated position.
GB/T 20456-2023 Portable chain-saws - Non-manually actuated chain brake performance
1 Scope
This document specifies the performance requirements and test method of the non-manually actuated chain brake on an electric or gasoline engine powered, portable hand-held chain-saw.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 6531 Machinery for forestry - Portable chain-saws -Vocabulary
Note: GB/T 18960-2023 Potable china-saws - Vocabulary (ISO 6531 : 2017, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 6531 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
- ISO Online browsing platform: available at https://www.iso.org/obp
- IEC Electropedia : available at http://www.electropedia.org/
4 Performance requirements
The non-manually actuated chain brake function shall be checked on a new normal production saw equipped with the shortest and longest guide bars specified in the instruction handbook, but no longer than 500 mm. If the guide bar is not less than 500 mm, only the specified shortest guide bar shall be used for testing. Battery-powered chain saws with several recommended battery pack options shall be checked according to the lightest battery pack and the shortest guide bar, the heaviest battery pack and the longest guide bar configuration.
When tested in accordance with Clause 8, the performance of the actuation function of a non-manually actuated chain brake is considered acceptable if each of the horizontal and vertical acceleration levels (ax and ay) at which the chain brake actuates is below the appropriate threshold level as shown in Figure 1 a), b) or c) for different chain-saw types and sizes.
5 Principle
The chain-saw shall be mounted on a test rig as shown in Figure 3. The drop mass falls from a defined height on the rocker and accelerates the chain-saw on the opposite side. The drop height shall be increased until the actuation of the non-manually actuated chain-brake occurs.
6 Test equipment
6.1 Acceleration measuring equipment
The total mass of the accelerometer(s) shall be as low as possible and shall not, in anycase, exceed 50 g, including the mounting, but excluding the cables.
The signal from the accelerometer(s) shall be processed by a low-pass filter having characteristics in accordance with Annex A.
Care shall be taken when mounting the accelerometer(s) so that the transfer function is flat up to 300 Hz in both measuring directions. For general considerations concerning accelerometer mounting, see ISO 5348. The transfer function may be considered flat if an addition of mass to the accelerometer, equal to that of the accelerometer itself, does not have any significant influence on ax and ay. This additional mass shall be placed between the accelerometer and its mounting if the mass is of metal, or around the accelerometer if the mass consists of materials such as clay or wax.
The accuracy of the measuring equipment, excluding accelerometer mounting and filter, shall be ±5% of the registered value in the frequency range from 0 Hz to 300Hz. See ISO 16063-1 for calibration methods.
6.2 Test rig
The design principles of the test rig shall be as shown in Figure 3.
The test rig shall be mounted solidly to the floor and designed so that deflection of the drop mass guide rod is restricted, e.g. by fixing both ends.
The guide rod shall be vertical within 2°.
The top surface of the steel spacer shall be horizontal within 1° in the lateral direction.
Both the length of the test rig cord and the longitudinal and lateral positioning of the pivoting pulley for the cord shall be adjustable.
The test rig rocker shall be made of rectangular hollow section steel, 80 mm×40 mm×4 mm, and shall have a mass of 6700g ± 300 g and a moment of inertia of 0.45 kg·m2±0.02 kg·m2.
The drop weight device shall have a drop mass of 15000 g ± 20 g. It shall be possible to select drop heights in steps of 10 mm or less, at least for drop heights between 200 mm and 1400 mm. The accuracy of the drop height shall be ±2 mm.
The dimensions of the spring between the drop weight and the rocker arm shall be such that a pulse length (ty) of 11 ms ± 2 ms is achieved.
ty shall be measured as the time of positive acceleration ay of the initial pulse, i.e. from the moment when ay increases from zero to the first time ay returns to zero. See example in Figure 2.
The spring defines the length and the characteristic of the impulse.
Note: The specified pulse length can be achieved by using seven conical disc springs (45 mm × 22.4 mm × 1.75 mm), with a characteristic of 640 N/mm ± 20 N/mm, each having an adverse orientation in relation to the next one.
If conical disc springs are used, they should be positioned and guided as precisely as possible. The diametrical play between the drop mass guide rod and the inner diameter of the conical disc springs should be 0.4 mm to 0.8 mm.
7 Preparation
Prepare the chain-saw for testing as follows.
a) Check that the chain-saw is in accordance with the product specification.
b) Precondition the saw by actuating the non-manually actuated chain brake ten times —for example, by dropping the saw while holding the rear handle, so that the bar tip hits a rigid, wooden surface.
c) Mount a saw-chain suitable for the guide bar and cut softwood for the time it takes to use one tank full of fuel at approximately maximum power speed (gasoline engine powered chain-saws) or for the time it takes to use one tank full of chain oil (electric-powered chain-saws). The chain brake shall not be activated during this cutting. Do not clean the chain-saw after cutting. Remove the chain with minimum disassembly and disturbance. The guide bar used for the cutting may also be, with minimum disturbance, replaced by a comparable, unused, guide bar having the same characteristics (i.e. length, bar nose radius, gauge).
d) Set the chain tension adjuster to its middle position and move the guide bar to its uppermost position, in order to eliminate play. Fasten the guide bar on the saw. The saw chain shall not be installed and the tanks shall be empty. The throttle trigger or power switch (for electric-powered chain-saws) shall be set to its fully activated position.
