DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 5-6/1964 str. 50 <-- 50 --> PDF |
1. Visina manje bočne stranice (hi) u praksi je uvijek veća nego što je postavlja standard. Taj zahtjev se prema tome može ispuniti. Ipak kod obračuna kubature pragova treba uzeti u obzir visinu, koja se postiže kod tesanja odnosno piljenja pragova iz trupaca minimalnih dimenzija. 2. Novi standard za pragove traži manji procenat crvenog srca na čelu praga, a prema tome i na čelu trupčića nego što je to dozvoljavao bivši standard. To se naročito opaža kod normalnih pragova samaca I. klase, koji se mogu izraditi samo iz trupaca, kod kojih učešće crvenog srca ne prelazi preko 24j% promjera. Budući da se u praksi pretežno izrađuju pragovi samci trupaca za izradu takovih pragova će se u našim šumama vrlo malo naći. Pa i kod dupljaka učešće crvenog srca u promjeru trupca za normalne pragove se kreće oko 46,5´% tj. manje nego što se to traži za pilanske trupce II. klase. Obzirom na to smatramo da je taj uslov standarda praktički neodrživ i da će dovesti do smanjenja proizvodnje bukovih pragova. LITERATURA 1. BENIĆ R., Razmatranje o iskorišćenju oblovine kod izrade pragova, Š. L. 1955, str 621—634; 2. BE.NIĆ R., Ekonomičnost kod izrade željezničkih pragova, Drv. Ind. 1956, str. 2—16; 3. BENIĆ R., Minimalni promjer trupca i maksimalno učešće srca kod bukove pragovske oblovine, Drv. ind. 1958, str. 34—40; 4. BRE2NJ.A1K M., Piljenje pragova i vlaličiina nepirave srži bukove ipragovđke oblovine, Drv. ind. 1963, sitr. 105—112; 5. Jugoslav, standard — JUS D.D1.020-1955. god.; 6. Jugoslav, standard — JUS D.D1020-1962. god. MINIMAL DIAMETERS OF ROUNDWOOD AND MAXIMAL PROPORTION OF RED HEART IN BEECHWOOD RAILWAY SLEEPERS (An analysis of the new standard specifications JUS D.D1020-XII 1962.) Summary The author analyses the regulation of the new Yugoslav standard concerning railway sleepers manufacture (JUS D.D1020-XII 1962.), from which he draws the following conclusions: 1. The yield in the production of hetwn sleepers of the normal dimension (250— and 260— cm. lengths) ranges from 52.3 to 58.4% for single sleepers and from 66.4 to 68.9% for double sleepers. Hence the average yield in single sleepers and double sleepers of 53% and 67.3´% respectively. When roundwood is hewn into narrow-gauge sleeppers the output is somewhat higher, i. e. from 54.8% (for 160-Qm. sleeper lenght) to 66.9% (for 120- 180-cm. sleeper length) in double sleepers. 2. The maximal allowable proportion of red heart on sleeper frontal area ranges in single sleepers class I from 3.7 to 10.3% while in class II from 9.9 to 53.6% (see table 5). In doufoile sleepers it varies from 28.7 (to 33.4% for class I, and from 59.7 to 67.5 for class II. In Consideration of this in the manufacture of single sleepers (250- and 260-cm. lengths) class I used for standard-gauge railway the maximal proportion of red heart may cover ibötween 22.8 and 24.1% of roundwood diameter at the thinneir end, while in class II between 52.0 and 63.3% of minimal roundwood diameter. When working up of double sileepers of class I it can range between 46.3 and 46.5, while in class II between 65.0 and 68.2%. Similar proportions are to foe found when narrow- gauge sleepers (see tables 5 and 6) are produced. 3. From the above dit is visible that the new standard specifications impose more severe conditions as to the quality of Beechwood to be converted into sleepers, which is likely to influence the supply of the market with sleepers. 212 |