JAHRGANG 47, AUSGABE 1/2006

The use of new technologies in the wood processing industry (e.g. X-ray scanning equipment) allows reliable detection and elimination of defects in timber. In order to benefit from these improvements is an industrial setting, the development of longitudinal joints in timber has to be advanced as well. This investigation compared a modified finger joint profile with industrially applied finger joint profiles. Tension tests were carried out at finger jointed lamellas for glulam and bending tests were carried out on structural finger jointed timber. The results showed increased bending strength of finger jointed structural timber and no improved tensile strength for finger jointed lamellas for glulam.

Gas boronizing is a promising way for increasing the performance of woodworking tools. Using boronizing very hard and wear-resistant surface zones can be produced. Three commercial hard metal grades with different cobalt contents between 2 % and 10 % and wedge angles of 45° and 55° were used. Gas boronizing was performed using a wide area of process parameters. Temperature , total pressure, BCl3-concentration and boronizing time were varied systematically. Properties and wear behaviour of boronized inserts were investigated. In case of milling melamine-laminated particle boards the working distance increased 40 % and 400 % at all hard metal grades using optimized process conditions. However the boronizing procedure has to be adjusted for every hard metal grade and geometry. Inserts with wedge angle 45° require a lower boronizing depth than 55° tools for achieving a higher performance.

The renovation under the aspect of fire safety is often problematic when it comes to wooden stairs cases in multistorey building. If the height of a building exceeds 7 m the Master Building Code demands the use of non-combustible materials for the construction of stairs. Especially in 4 or 5 storey buildings which were erected at the beginning of the last century one founds often wooden stair cases. As matters stand the wooden stair case has to be replaced or covered by gypsum card boards if the building is rededicated. Both solutions change the character of a building sustainable and are not able to meet aesthetic requirements. In joint projects four R&D-Institutes developed in conjunction with 8 small and medium sized enterprises new innovative high-performance fire protective coatings for wood and woodbased materials were developed based on high temperature insulating materials used in space technology. This new technology offers for the first time the possibility to renovate existing wooden stairs fire-safe, economical and aesthetic.

The shearing resistance of spruce wood samples glued with PUR, PVAc and MUF was tested for varying air moisture and temperature. Moreover the tensile strength in proximity to the bond line was tested on microtome slices. An increase in air moisture led to a decreasing shearing resistance. The tested samples showed for all adhesives mostly predominantly wood failure. The stiffness of the specimens glued with PVAc and PUR sunk noticeable with increasing temperature, the ratio of bond failure rose. Whereas samples glued with MUF showed only marginal diminution. A soli- dification of wood in proximity to the glue line due to the penetrating adhesives could not be ascertained.

The construction o light transport vehicles is an important aim o the producers. There ore, materials with low weighti- ness should be used or each part o a vehicle. The loors o transport vehicles are o ten composed o wood and wood based panels (e. g. birch or beech plywood). The IHD developed a wood based panel with textile rein orcement. The middle layers o the new panels are composed o veneer with lower green density and the external layers are made rom wood with higher green density. The properties o material sur aces are increased, or instance the sur ace resi- stance.

Double resonance effect is a problem when manufacturing percussion instruments like xylophone or marimba. Bending and torsional vibrations are both present when hitting a tone bar. When these two vibration frequencies are close to one another, double resonance occurs that significantly dete- riorates the quality of the instrument. The author presents a simple method for predicting the likelihood of double resonance in a material of a certain length, and verifies the accuracy of the method through experimental results. The efficiency of the method is also demonstrated by a top quality xylophone manufactured from black locust wood.

The Institute for Research and Development of Musical Instruments, adjacent Institute of Dresden University of Technology, and the chair for Wood and Fibrous Materials Tech-nology of Dresden University of Technology worked on a research project on the application of thermally modified wood in musical instruments. The goal of this project was to analyse the changed physical, anatomical and chemical characteristics of modified woods and to compare them to characteristics being relevant for musical instruments. Conclusions on the possible use of these woods in musical instruments were drawn. In part 1 of this publication (Holztechnologie issue 4/2005, p. 36-42) selected anatomical and physical characteristics are described, which appear relevant for the use in musical instruments. Part 2 is concerned with technological characteristics and the production and examination of parts of musical instruments.

One of the most important works of Polish historical literature is "The Polish Architect" by Solski from 1690, which contains an overview of the state of mechanics and hydromechanics at that time, the theory and practice of tools and engines, and the author's own thoughts on the subject. Its value lies in the description of the construction and the effect of simple devices to reduce the weight of various lifting trees, rollers, pile drivers, winches, as well as in the description of water, horse and ox mills, windmills and sawmills. Among the machines described are the water-driven gates. Solski distinguished two types: simple gates and gates with gears. Kinematic diagrams of such gates and details of the drive are shown, technical data are described. The exact dimensions of the individual parts enable a kinematic analysis of all the gate mechanisms.