MANUAL ON THE DELFT WIRE LACING TOOL

Transcription

1 1 MANUAL ON THE DELFT WIRE LACING TOOL By Dr. Pieter Huybers May, 1999 Building Technology Group Faculty of Civil Engineering Delft University of Technology 1, Stevinweg 2628 CN DELFT, The Netherlands Tel: Fax:

2 2 The wire lacing tool

3 Introduction 3 The Delft wire lacing tool is operated by hand and is used for binding and connecting roundwood by tightening a steel wire around it. It weights about 2.8 kg and serves to make lacings with 2 to 5 mm galvanised steel wire. It can be used for lacings around any object, but mainly around bamboo pipes and timber connections. The reference list on page 23 mentions a few publications dealing with possible applications. The present manual is meant to explain its working and to give instructions for proper use. The tool basically consists of a vice that grips the wire. It is manipulated with a fixed and a hinged handle, that are opened and closed to tighten the wire. The wire ends are then twisted to secure them and finally cut at a certain length (usually 30 mm). The process passes two distinct phases: Phase 1 - The stretching of the wire in order to tighten the lacing Phase 2 - The fixing of the wire lacing by twisting its ends together

4 4 Description of the tool (See fig. 2) The tool has a hollow cylindrical base (1) in which a smaller cylinder (2), with a small central opening (11), rotates. On this base a handle (3) consisting of two parallel bars is welded at an angle. Between the bars a rotating wheel (8) and a hinged (5) bent lever, provided with sawteeth (6), are positioned. The fixed handle has a hinged grip (4), that can be moved down to turn the tool easily. The solid inner cylinder of the cutting device (2) is symmetrical so that it can be reversed after some time to reduce the wear on the cylinder. The lever is connected to the wheel by a knee hinge (12), rotating the wheel when the lever is pulled towards the fixed handle. At the same time the saw-teeth grip the wire, pressing it firmly against the wheel. With each pull the wire is stretched a bit more over the wheel, the saw-teeth preventing it from slipping back. The numbers indicate: 1. hollow cylinder 2. rotating solid cylinder with vertical hole (11) 3. inclined, fixed handle 4. movable polypropylene grip 5. main part of lever 6. hardened saw-teeth 7. smallest part of lever 8. wheel 9. adjustable, fixed part of cutting device 10. sliding cutter plate 11. hole in rotating solid cylinder 12. knee hinge in pre-tensioning handle 13. bolt acting as the axis of wheel (8), see also fig. 9

5 Construction of the tool 5

6 6 The cutting device Between the wheel and the base there is a cutting device, consisting of two hardened steel plates (9 & 10). The first plate (9) can be adjusted in fixed position with two screws, the sliding plate (10) can be moved towards the other with a lever. Fig. 3 shows the tool from below. These plates indent the wires when the thicker, twined section moves up between them, breaking them when the turning continues. During the twisting, the four bolts on the bottom keep the inner cylinder from rotating by getting stuck behind the lacing.

7 Adjusting the width of the cutting device 7 Before using the tool it has to be adapted to the wire diameter that is being used. This is done by adjusting the beak opening of the cutting, device. The opening should be slightly bigger than the wire thickness. The cutting device consists of a sliding plate (10) and of an adjustable plate (9). The adjustable plate can be brought to the desired position by tightening or loosening two screws (17). The two bolts (16) on top of the cutting device keep the plate from displacing spontaneously. The sliding plate can be closed with a lever (14). The two plates should leave a margin of about 0.5 mm in closed position.

8 8 Preparing the binding A piece of wire is cut to the correct length (approx x Diam cm), bent in an appropriate shape and placed around the specimen. If the thread is too thick to be bent by hand, a steel pipe of the appropriate length and diameter may be used as an auxiliary means.

9 Placing the tool 9 The tool is now placed over the thread ends, which then are inserted in opening (11). Make sure the lever is, as shown in the fig. 4A, in open position and the cutting device is opened, so that the thread ends can pass easily through the device.

10 10 Tightening the wire The wire is tightened by pulling the lever towards the fixed handle. This is repeatedly done - with each repetition stretching the wires a bit further - until the thread is stretched as tight as possible around the timber. After the last stroke the handles should be kept closed.

11 11 Now the wire lies tightly around the object. The amount of the induced stress is left to the judgement of the operator. He will have to learn this by experience. If he stresses the wire too much, it may break prematurely somewhere in the middle of the thread. This should of course be avoided.

12 12 End of the stretching process The wire ends have followed the wheel in its circular movement and protrude at the back.

13 Twisting the wire 13 The lacing is now secured by twisting the wire ends together over a length of about 3cm. The hinged polypropylene grip (item 4 in Fig. 2) on the fixed handle (3) is first turned horizontal and then the twisting is done by holding the wire ends gripped by the tool and rotating the whole machine around a hypothetical vertical axis: the solid cylinder (2). The twisting length of the thread ends is defined by the length of this cylinder. The cutting device (9) and (10) on top of the cylinder prevents progression of the twisting beyond this point.

14 14 Closing the cutting device Before the twisting starts the cutting device should be closed. By turning the handle (12) the sliding- plate of the cutting device is brought to a more narrow position.

15 The lacing tool seen from below 15 During the stretching process the cutting device is kept in an open position (handle at left) in order to provide an unobstructed passage of the wire in the initial stage of the procedure. Four small bolt heads protrude from the bottom of the rotating cylinder; they keep it in place as the bolts get suck behind the wire whereas the tool is rotated around it.

16 16 The cutting device is narrowed to the wire diameter (handle at right). Note the two screws (17) with which the clearance can be adapted.

17 17 After two or three turns the rotation of the tool meets some kind of resistance as the wire refuses to twist further. Now the cutting blades come into action: they cause an indentation in the twisted wire and- if the twisting is continued - finally breaking it. Now the tool can be lifted off from the twisted lacing.

18 18 The remaining wire ends have to be removed. For this purpose the cutting device should be opened again to achieve maximum clearance.

19 Securing of the twisted joint 19 The twisted ends are sharp and may be dangerous in some circumstances. They can therefore be hammered flat and fixed to the wood with staple nails or similar means of fastening.

20 20 The compacting of elastic bundles The lacings are normally applied around sturdy materials such as single roundwood poles. Thicker, and particularly elastic packages (e.g. overlapping joints of poles or bundles of branches) that require a greater pull on the wire to achieve compression, may cause the wires slip through the cutting device after each stroke of the movable lever (item 5 in Fig. 2) as soon as this lever is loosened. The deformation stress of the wire in this case is not high enough to withstand the required pre-tensioning force that would keep the bundle tightly together. This problem can be solved by having two operators with tools acting in unison (Fig.17). Two separate lacings are laid around the bundle, and the two tools are placed as before, opposed to each other on both wire ends. One stroke is given by the first operator with the movable lever of his tool and this lever is then kept under stress. Then the second person gives one stroke with the lever of his tool and also keeps this under stress. Now the first person can loosen his grip, make a second stroke, and keep it taut. This can be repeated until the compaction of the bundle is reached.

21 21

22 22 Length of the twined part The solid inner cylinder of the cutting device (item 2 in Fig. 2) is symmetrical so that it can be reversed after some time to reduce the wear on the cylinder. The length of the twisted part of the lacing is dependant on the length of this cylinder and is thus normally kept at 30 mm. An extra cylinder of 19 mm length (item A in Fig. 18) is supplied, together with the necessary bolts, as an accessory that must be screwed upon the other cylinder in order to increase the twining length to 50 mm

23 References Farm building structures of roundwood timber. International Conference on Timber Constructions for Farm Buildings, Ronneby Brunn, Sweden, May, 1984, Ch. 2:5, p Timber pole space frames, Space Structures 2 (1986/7), p The use of timber poles for agricultural building structures, Seminar on Wooden Buildings in Agriculture, Nov. 1988, Vaksjö, Sweden, p. 6:1-6: Thin poles of roundwood for structural applications in building, Structural Engineering Review. 1990, No. 2, p Roundwood poles in spatial structural arrangements, Proceedings of the Int. Conf. On Lightweight Structures in Civil Engineering, Warsaw, Sept. 1995, p The use of roundwood and bamboo for structural building applications, Proceedings of the Int. IASS Conf. on Spatial Structures: Heritage, Present and Future, Milan, 5-9 June, 1995, p The structural application of thin roundwood poles in building, Final report for Project FAIR- CT , task 2A, September 1996, 122 pp. 8. Roundwood poles in spatial configurations, Structural Engineers World Congress, July, 1998, San Francisco, USA, Proceedings on CD-Rom, Paper ref.: T135-3, pp.8, Abstracts volume, p. 650.

24 24 Acknowledgements This manual has been composed as task 1f in the context of the European project FAIR-CT It replaces the manual of an earlier version of the tool, that proved its suitability in a number of roundwood building projects but which had a few parts that were not standard and were difficult to produce. Therefore a simplified version had been developed. The original tool had been designed by Jaap Lanser and was further developed with the assistance of Sier Th. van der Reijken in collaboration with the author. The latter also made the hand sketches in this manual. Figs. No. 2, 3, 4, 12 and 13 are based on technical drawings, made by Jan J. Rodoe. No part of this publication may be reproduced in any form without proper reference and no commercial use is allowed without written permission of the author. This manual has been printed by the Delft University Printing Office.

25 25 STEEL WIRE LACINGS MAYBE USED TO CONNECT STRUCTURAL MEMBERS OF ROUNDWOOD OR MAY REPLACE CONVENTIONAL MEANS OF REINFORCING BAMBOO OR WOOD STAVE PIPES AND TANKS. THIS MANUAL DESCRIBES THE CONSTRUCTION AND THE WORKING OF A MANUALLY OPERATED TOOL, WHICH HAS BEEN DEVELOPED AT THE DELFT UNIVERSITY OF TECHNOLOGY IN THE NETHERLANDS.