dynaload - design, construction, use and maintenance

Dynaload Publication/Version 1.2 – Oct 2005 1

PNEUROP Publication DYNALOAD - design, construction, use and maintenance.

Contents Foreword ............................................................................................................................................................2 0 Introduction ...........................................................................................................................................2 1 Scope .....................................................................................................................................................3 2 General ..................................................................................................................................................3 3 Relationship with standards...................................................................................................................4 4 Design....................................................................................................................................................4

4.1 Preferred sizes ..........................................................................................................................4 4.2 Anvil and Test tool ...................................................................................................................4

5 Performance/Power measurements .......................................................................................................6 6 Operational features...............................................................................................................................6 7 Maintenance ..........................................................................................................................................6 8 Construction ..........................................................................................................................................7

Table 1 – Identity of component parts as shown on diagrams in Annex A, B, C and D.......................7 Annex A Type 1 - Single piece square-end Dynaload .......................................................................................8 Annex B Type 2 - Single piece taper-fit Dynaload ............................................................................................9 Annex C Type 3 - Cup/Ball-end Dynaload ......................................................................................................10 Annex D Type 4 - Needle scaler variant Dynaload..........................................................................................11 Annex E Design and Constructional Details ....................................................................................................12

Table 2 – Bottom plate specifications .................................................................................................12 Table 3 – Cylinder specifications ........................................................................................................13 Table 4 – Stud specifications...............................................................................................................14 Table 5 – Anvil specifications.............................................................................................................15 Table 6 – Bush clamp plate specifications ..........................................................................................16 Table 7 – Flange specifications ...........................................................................................................17 Table 8 – Guide bush specifications....................................................................................................18 Table 9 – Steel ball reaction plate specifications ................................................................................19 Table 10 – Steel ball specifications .....................................................................................................20 Table 11 – Type 1 toolpiece specifications .........................................................................................21 Table 12 – Type 2 toolpiece specifications .........................................................................................22 Table 13 – Type 3 toolpiece specifications .........................................................................................23

Annex F Recoil spring......................................................................................................................................24 Table 14 – Recoil spring specifications...............................................................................................24

Bibliography.....................................................................................................................................................25


DYNALOAD - test device for percussive tools - design, construction. Foreword This publication was produced by a working group of the PNEUROP Tools Committee. The information provided is primarily intended to instruct and supplement guidance given in standards for the measurement of noise, vibration and performance of percussive hand-held power tools.

At the time of publication of this guidance document, dynamic loading devices, such as the ones described herein, had been used for many years in conjunction with the testing of percussive power tools. In particular, the vibration test codes, ISO 8662 parts 2, 3, 5 and 14, all specified the use of such loading devices for testing a range of power tools, including chipping hammers, rock drills, concrete breakers and needle scalers. However, since none of the published standards specified the design of the loading device in detail, there were inevitably many small differences between the loading devices which were manufactured. The question then arose as to whether these differences affected the measured results of the tests, for which the loading devices were used.

In preparation for producing this document, a PNEUROP working group performed a series of tests to investigate the effects, on the results of vibration tests on concrete breakers, of varying the detailed design of the loading device. The tests, which used different sizes of concrete breakers (non of which incorporated vibration damping features), were conducted using the largest size of loading device (60 mm internal diameter). ISO 8662-5: 1992 and EN 28662-5:1994/A1 were the reference standards applied. The test series was designed to investigate whether varying the designs of the tool piece and anvil affected the results. Particular attention was, however, also paid to evaluating the effects of varying the clearances between moving parts and to checking measurement repeatability throughout the working day and from one day to another.

The investigation by the PNEUROP working group indicated that the loading devices presented in this document are of a rugged design, permitting good repeatability of measurements, and that their performance is insensitive to small dimensional changes or usage rate. Repeatability throughout the working day and from one day to the next was found to be very good. The repeatability of measurements obtained for each individual operator was also found to be good, with the result that mean results from three operators gave good repeatability, despite significant variations between individual operators. For non-vibration damped breakers, the choice of tool piece and anvil (either Type 1, 2 or 3 in this document) did not have a significant effect upon the vibration, when measured according to the standards used.

In this guidance document, the PNEUROP Tools Committee offers a family of designs for dynamic loading devices, for reference by committees charged with developing standards for the measurement of noise, vibration or performance of percussive power tools. When selecting and, if necessary, adapting a loading device for a specific standard, it is expected that the responsible committee will perform tests to verify its suitability for their purpose. The PNEUROP Tools Committee would be grateful to receive any information resulting from such tests, in order that this guidance document may be revised and improved as more knowledge is acquired.

0 Introduction The measurement of physical parameters such as noise and vibration from hand-held tools has been the subject of investigation for many years. The means by which these parameters can be obtained have resulted in a number of devices to provide for a "working load" for the tool being investigated.

The resulting data can provide the customer with relevant information by the use of a well-defined method that is both repeatable and reproducible. The last two issues, repeatability and reproducibility, are vital where the data obtained is required to demonstrate compliance with legislative requirements.

The equipment used to provide a "load" against which the hand-held power tool can "work" should be easily constructed from common materials and provide for ease of maintenance. This publication is intended to provide the specifications and guidance for such a loading device.

1 Scope To provide a specification on design and construction and guidance on use and maintenance of a dynamic loading device for the following categories of hand-held power tools;

percussive;

rotary-percussive.

The device may be used when measurements are being made for either vibration, noise or performance, including when required for specification in test standards.

2 General The dynamic loading device is given the common name of DYNALOAD. The device consists of a metallic cylinder filled with steel balls on which the hand-held power tool is brought to bear and which absorbs the energy transmitted by the tool. The device can either be fixed to a surface or buried below the working floor level.

Tool piece

Guide bush

Anvil

Cylinder

Steel plate

Steel balls

Figure 1 - Basic elements

Free length

‘h’

The diagram in Figure 1 identifies the essential items making up a Dynaload. The specification of each item is identified later in this publication.

The Dynaload device absorbs the blow energy from the power tool. Much of the shock wave is absorbed by the steel balls, however some 15% to 20% is reflected back to the power tool, as would be the case in a normal working situation.


The diagram in Figure 2 shows a typical construction of an assembly, which holds a Dynaload below ground. This would be utilised with concrete breakers, as it would afford a convenient location for the operator during testing conditions.

Sound absorbingmaterial (e.g. sand)

Sound absorbing material (e.g. sand)

Gap filling material Screening slab

(Top surface level with ground)

Hole in ground

Hole in round

Free length

‘h’

ounting

g

Figure 2 - Below ground m

3 Relationship with standards This standard only specifies the Dynaload device and it is the responsibility of experts on international and other standards committees and users of this specification to:

select the appropriate size and type of Dynaload test rig for the particular tool being tested, such as noise, vibration or performance testing

specify any additional requirements needed for the purpose of the test, such as mounting blocks, screening slabs, etc.

specify the loading and operating conditions for the tool under test.

When selecting or referring to a particular type of Dynaload test rig, the following format shall be used:

Size / Type, e.g. “60 mm / Type 1 Dynaload”,

where “Size” refers to the internal diameter of the cylinder (see 4.1) and “Type” refers to the design of test tool and anvil (see 4.2)

4 Design

4.1 Preferred sizes The Dynaload should be constructed to be of an appropriate size depending on the hand-held power tools to be tested. Three preferred sizes are in use, i.e. cylinder diameters of 20mm, 40mm and 60mm, these sizes relate to the requirement for absorbed power capabilities.

4.2 Anvil and Test tool 4.2.1 Type 1: 1 piece - solid formed tool piece and anvil

(See Annex A) Split guide bush

The diagram in Figure 3 identifies the form of a one-part tool/anvil. This may be considered to be superior to the two-part construction where the measurement of noise is concerned. A unitary construction reduces the possible sources of unwanted noise.

This type of construction is more costly than a two-part assembly. A two-part assembly can utilise the actual tool steel used by the hand tool. Where the tool steel is used it must be of circular cross section and dimensioned to pass through the bush.

Tool and anvil as unitary

assemblyCylinder

Split g e bushuid

Figure 3 - One-part tool

Recoil springThe diagram in Figure 3a shows a spring, which is utilised when the

effects of recoil from certain types of percussive power tool being tested may have an adverse effect on the Dynaload assembly and consequently any readings being taken. The spring is an optional item and should be used only when required. As in

Figure 3

Figure 3a - Recoil spring


4.2.2 Type 2: 2 piece - tapered end tool piece with a mating anvil

(See Annex B) Tool piece with taper fit end Guide bush

The diagram in Figure 4 identifies an alternative approach to the construction of the tool piece and the anvil. Although in separate parts in-use they act as a one-part tool.

This construction allows for a simple design for the guide bush as a one-part construction rather than that identified in Figure 3.

Anvil with taper fit hole

A standard tool steel can be modified to provide the necessary taper fit. Where the tool steel is used it must be of circular cross section and dimensioned to pass through the bush.

Cylinde

Figure 4 - Taper fit tool piece

4.2.3 Type 3: 2 piece - ball-ended tool-piece with a mating anvil

(See Annex C) Tool piece

Guide bush

Anvil

Cylinder

Figure 5 - Two part test tool

The diagram in Figure 5 identifies the construction of the tool and anvil as separate parts.

This type of construction lends itself to the testing of rotating tools.

The mating joint between the anvil and tool should be a close fit, as should the tool and guide bush.

A standard tool piece can be utilised with a modified end to fit the anvil. Where the tool steel is used it must be of circular cross section in the vicinity of the guide bush and dimensioned to pass through it.

4.2.4 Type 4 Needle scaler type

(See Annex D)

Needle scaler

Figure 6 - Needle scaler

Modified anvil

Needles

The diagram in Figure 6 shows the arrangement to be adopted when using the Dynaload with needle scalers. The guide bush is removed and the clamp plate is retained through which the needles of the needle scaler pass and then rest directly on to a modified anvil having a small recess to secure the needles and avoid contact with the cylinder wall.


5 Performance/Power measurements

Thermocouple mounting point

Coolant inlet

Figure 7 - Power measurement

When the Dynaload is used for performance or power measurements then provision for cooling as well as the measurement of temperature should be included.

The diagram in Figure 7 identifies the basic requirements for the measurement of power or performance. Where the Dynaload is to be used for extended periods of time then cooling is required. This may be water, oil or air depending on conditions of the test and whether the coolant is to be used as the source of heat for calculation purposes.

6 Operational features Before operating the Dynaload device the Dynaload should be checked that all parts are within the dimensional specifications set out in this document.

If the condition of the steel balls has deteriorated then the entire charge should be replaced. The steel balls will during use be compressed and become fragmented therefore the decision to replace the charge of steel balls will depend very much on experience. As a guide to the decision making process when the surface layers have become fragmented then this can be taken as the time for the change. It is false economy to salvage balls from an exhausted batch since they are an unknown quantity and may lead to premature deterioration of steels balls in a new batch.

The Dynaload is specified in three sizes according to the power and size of the hand tool. The specified lengths of the tool piece should not be exceeded since this will lead to undue flexing of the tool piece and breakage, and may affect the noise and vibration readings.

Before any measurements are undertaken when a new charge of steel balls is introduced the equipment should be run for a period of 15 to 30 minutes to allow the column of steel balls to settle. In the new condition the point contact on each surface leads to a rapid deterioration of the surface of the balls that is quickly nullified by the running in procedure.

7 Maintenance The Dynaload being of simple construction requires little maintenance. Since the device is constructed from steel the main problem will be rusting, especially where it is used with water as a coolant or air that has not been dried. Also where the device is used outside and underground regular inspection of the steel balls and the main tube is essential.

When stored for long periods the steel balls should be removed and packed separately. The main construction should be stored in a dry area or be coated with a layer of grease or oil. The internal surface of the Dynaload should be inspected for wear. The Dynaload has been found to have a long service life with little deterioration of the main cylinder. However it has been found that for approximately 40mm from the top surface of the steel balls the cylinder wall becomes grooved. This is the area, which absorbs the majority of the blow energy.



8 Construction All Dynaload variations may have the items identified in the table below. Their actual construction will depend on the type chosen for a particular application or preference on the part of the user. The construction of the Dynaload does not require any special engineering practices and can be successfully produced by any general engineering facility.

Table 1 – Identity of component parts as shown on diagrams in Annex A, B, C and D Diagram Ref. number

Quantity Description Note

1. 1 Bottom plate 2. 1 Cylinder 3. 4 Stud 4. 1 Type 1 anvil Identified in Annex A 4a 1 Type 2 anvil Identified in Annex B 4b 1 Type 3 anvil Identified in Annex C 4c 1 Type 4 anvil Identified in Annex D 5. 1 Bush Clamp plate for item 7 6. 1 Flange 7. 1 Guide Bush 8. 1 Steel ball reaction plate 9. 1 O-ring Cylinder seal this is optional and only required if a coolant

is to be used during testing 10. 1 O-ring Sited in a groove in the o.d. of item 7 11. 4 Nut For item 3 of size M16 to secure item 6 12. 4 Screw M10 bolt to secure item 5 13. As required Steel balls For endurance tests it may be more practical to use large

diameter steel balls, e.g. 6mm. 14. 1 O-ring Sited in a groove in the i.d. of item 7 15. 1 Type 1 toolpiece Identified in Annex A 15a 1 Type 2 toolpiece Identified in Annex B 15b 1 Type 3 toolpiece Identified in Annex C 15c 1 Type 4 toolpiece Identified in Annex D

Note 1: Tolerances The components in Table 1 are shown graphically in various Annexes, where required or known tolerances are given which are in accordance with ISO 286-2. Where no tolerance is shown but would be desirable then the method for allocating such a tolerance should be done in accordance with ISO 1829 and ISO 2768-1.

Note 2: Materials Material specifications given in this publication are those which have been successfully used, however they are not exclusive and alternatives may be employed provided that the material is able to fulfil the functional requirements.

Annex A Type 1 - Single piece square-end Dynaload


Annex B Type 2 - Single piece taper-fit Dynaload


Annex C Type 3 - Cup/Ball-end Dynaload


Annex D Type 4 - Needle scaler variant Dynaload

.


Annex E Design and Constructional Details

Note: The Item numbers in this Annex follow the numbering system in Table 1 and Annexes A, B, C and D.

1a Bottom plate 1b Bottom plate regulated coolant supply

Where a regulated coolant supply may be required then the following dimensional details are identified as a practical alternative to that shown for a plain connection at the bottom of this page.


All dimensions are as given on the diagram.

Dynaload Size

Dimension 20 40 60 A 039.0

050+ 046.0070+ 054.0

090+ B 160.0

035+ 190,0055+ 190,0

075+ C 27 47 67 D 6 10 10 O-ring Diagram ref. 9 fits in groove formed

by dimensions ‘B’ and ‘C’ Mild steel

Material AISI 1020 SS 2172

Hardening Not required

Table 2 – Bottom plate specifications

Annex E continued2. Cylinder


Dynaload Size Notes

Dimension 20 40 60

A 060.0134.050−

−060.0134.070−

−060.0134.090−

− This dimension may be as shown on the diagram or it may represent the outside dimension of the whole tube length. The only proviso is that it should fit the allocation in the bottom plate

B 052.0020+ 62.0

040+ 074.0060+

C 165 200 250 D G¼ G½ G½ or

G⅜ This dimension is given where a coolant outlet is to be provided, this is an optional item and only required where the Dynaload is used for extended operation such as for power measurement characteristics. These port sizes are not critical any convenient fitting may be used.

Additional Specifications

Material AISI 8620 SS 2172 BS970 805M20

Hardening depth DC 1 ± 0,1 Surface hardness RC 62 ± 2 Hardness relates to the finished part

Table 3 – Cylinder specifications

Annex E continued3. Stud


Dynaload Size Dimension 20 40 60 L 210 270 330 Additional specification

Material AISI 4340

SS 2225-05 BS970 817M40

Nut Diagram ref. 11

Table 4 – Stud specifications

Annex E continued 4. Anvils

4a – Type 2 Anvil

4c - Type 4 anvil


4b – Type 3 Anvil

Dynaload Size

Dimensions 20 40 60 A Deleted for

this size 30 45

D 01,06,19 −

01,06,39 −

01,06,59 −

R 5,005+ 5,0

09+ 5,0015+

RS 1 2 2 L 25 35 35

Additional specifications Material SS 2090 Surface hardness Rc Type 2: 59 ±1

Type 3 & 4: 55 ± 2 Hardening depth All types: 0 3,0

05, +

M6 tapped holes To assist in the removal of anvil

Table 5 – Anvil specifications

Annex E continued 5. Bush clamp plate

Dynaload Size Dimension 20 40 60

D 30 30 50 Additional specifications

Mild steel Material AISI 1020

SS 2172

Table 6 – Bush clamp plate specifications


Annex E continued 6. Flange

Dynaload Size Dimensions 20 40 60 A 40,5 50,5 70,5 B 20,5 40,5 60,5 C 039.0

050+ 074.0070+ 087.0

090+

Additional Specifications Mild steel

Material AISI 1020 SS 2172

Table 7 – Flange specifications


Annex E continued 7. Guide Bush

The diagram shows the dimensioning for the application of the bush as either in solid form or as a split bush. The splitting process is achieved by applying a cut of dimension as shown in the diagram on the right. The width of the cut applies to all sizes of dynaload

Dynaload Size Dimensions 20 40 60 A 036,0

010+ 043,0018+ 052,0

030+ B 0

110,04,16 − 0160,02,35 − 0

190,02,55 −

C 040,0073,020−

− 050,0089,040−

− 060.0106,060−

−

D


110,007,13 + 130,0

07,21 + 160,008,34

E 60 60 60 F 40 50 70

Additional specification Material type

Bronze: ASTM B139 Alloy 524000

Clearance A clearance of 1mm on the diameter of the hole should be maintained between the bush and the inserted tool piece.

O-ring Diagram ref. 10 fits in groove on outside diameter at the base of the bush

O-ring Diagram ref. 14 fits in groove on inside diameter at the top of the bush

Table 8 – Guide bush specifications

Annex E continued 8. Steel ball reaction plate

Dynaload Size Dimensions 20 40 60

D

0130,019−

0160,039−

0190,059−

R 2 4 4 Additional specification Material SS 2090 Surface hardness Rc 55 ± 2 Hardness depth mm

3,0

05,0 +

Table 9 – Steel ball reaction plate specifications

9. O-ring

See Item 1 and table for specifications. The O-ring material requires no specific characteristics so any standard type may be used.

10. O-ring


11. Nut

Specification as in Table 1

12. Screw

These screws to fix the bush clamp plate have no particular specification. General engineering quality screws may be used.


Annex E continued 13. Steel balls

Dynaload Size Dimensions 20 40 60 Metric (mm) 3.15 4 or 3.96

Imperial (inch) 81 325 (equiv 3.96 mm) Steel ball column height

inside cylinder (mm) 50 ± 5 100 ± 5 150 ± 5

Additional specification Material Steel Surface hardness Rc > 63

Table 10 – Steel ball specifications

14. O-ring




15. Type 1 toolpiece


TL Includes “L” & Manufacturer dimensions L See Note L D 05, 1,0−19 39 59 0

1,0−57, 064, 1,0− A 1,012+

0 0 0 1,024+ 1,038+ d 0

1,014−0

1,024−0

1,030− R 4 5 6

NOTE L This dimension incorporates a length which is supported within the dynaload and a “free” length between the “upper surface” of the dynaload and the base of the power tool where the inserted tool is held by a retainer. The “upper surface” of the dynaload may be considered as either the dynaload surface itself (See Figure 1) or any acoustic cover placed over the dynaload (See Figure 2). The dimensions given in this table are advisory but have been shown to give good results.

Additional specification Power tool type Dynaload Free length Material Steel 20 Surface hardness Rc 50/55 Riveting hammer 40 10 ± 4

20 40 ± 15 40 60 ± 20

Other percussive tools

60 80 ± 20

Table 11 – Type 1 toolpiece specifications

15a Type 2 toolpiece


TL Includes “L” & Manufacturer dimensions L See Note L



20 40 ± 15 40 60 ± 20


60 80 ± 20



15b Type 3 toolpiece


TL Includes “L” & Manufacturer dimensions L See Note L d 30 R 15 RT 5 ± 1 RZ 2



20 40 ± 15 40 60 ± 20


60 80 ± 20



Annex F Recoil spring

1) The end shall rest on the subsequent coil

2) Delete if not required


As given on diagram Spring Additional specification Material SS 1774-04 Shear modulus 78500 N/mm2 Total number of coils 4,5 Direction of winding Right Length at minimum force 25 mm Minimum force 438 N Shear stress at minimum force 150 N/mm2 Rate 215 N/mm

Table 14 – Recoil spring specifications



Bibliography

a) Standards that currently make reference to or use the dynaload

ISO 8662 Hand-held portable tools – Measurement of vibrations at the handle;

Part 2: Chipping hammers and riveting hammers (also as EN 28662-2)

Part 3: Rock drills and rotary hammers

Part 5: Pavement breakers and hammers for construction work (also as EN 28662-5)

Part 14: Stone working tools and needle scalers (also as EN 28662-14)

ISO 15744 Hand-held non-electric power tools – noise measurement code – Engineering method (Grade 2) (also EN 15744)

b) Standards referred to or are of use in the application of this publication

ISO 286-2 ISO system of limits and fits – Tables of standard tolerance grades and limit deviations for holes and shafts

ISO 2768-1 General tolerances for dimensions without tolerance indications – Tolerances for linear and angular dimensions

c) Material standards referenced in this publication

AISI 1020 is one of the very commonly used plain carbon steels. It has a nominal carbon content of (SAE J1397) 0.20% with approximately 0.50% manganese. It is a good combination of strength and ductility and may be hardened or carburized.

AISI 4340 is a heat treatable, low alloy steel containing nickel, chromium and molybdenum. It is known for its toughness and capability of developing high strength in the heat treated condition while retaining good fatigue strength.

AISI 8620 is a hardenable chromium, molybdenum, nickel low alloy steel often used for carburizing to develop a casehardened part. This casehardening will result in good wear characteristics.

ASTM B139 Bronze Alloy 524000

SS 1774-04

SS 2090

SS 2172

SS 2225-05

BS 970 Replaced by Parts 1 to 5 of BS EN 10277 and BS EN 10278:1999. Therefore the materials 805M20 and 817M40

NOTE: AISI – American Iron and Steel Institute

SAE – Society of Automobile Engineers (US)

SS – Swedish Steel

dynaload - design, construction, use and maintenance

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