Figure 10. — Washington Model 608A yarder. 



The yarder (fig. 10) was built by Vvashington Iron Works for the balloon logging 

 system. Aero Yarder, Model 608A, has hydraulic interlocking drums with a mainline ca- 

 pacit>'of 5,500 ft (1,676 m) and haulback capacity of 7,000 ft (2,134 m) with 1-inch 

 (2.54-cm) cable. The weight of the yarder is approximately 160,000 lb (72,575 kg) 

 with a tracked undercarriage. Hydraulic problems and planetary gear problems occurred 

 during the first year's operation, but the newly designed yarder performed satisfactoril 

 during most of the last two logging seasons. An HD-21 tractor equipped with a large 

 capacity hydraulic winch was used for transporting the balloon. T!ie balloon was teth- 

 ered to this tractor during maintenance and moving operations. 



A schematic of a typical yarding layout for the sale is shounn in figure 11. The 

 figure illustrates tlie continuous cable system with the balloon providing a lifting 

 force to fly logs from the stum.p to the landing. Location of the 5/16-inch (0.79-cm) 

 strawline used for restringing tlie mainline is also shown. Figure 12 shows the opera- 

 tions schematic for a typical yarding turn. 



Th.e yarding turn starts witli the balloon leaving the landing area unloaded. The 

 balloon's buo>'ant force provides a portion of the power to move the system out to the 

 felled logs. When tlie balloon is over the logs, tension is applied to the mainline 

 and haulback to pull the balloon down so the tagline can be reached by the choker 

 setters (fig. 12A) . The chokers have been preset on the load of logs so that the 

 load can be quickly hooked to the tagline and the men can move clear of the area. The 

 choker setters then radio the machine operator that the load is hooked and ready to yard 

 The lines are slacked so the balloon rises nearly vertically to clear the understory and 

 the yarder begins pulling in the mainline while simultaneously slacking the haulback 

 (fig. 12B) . As tlie logs approacli the landing area, the rate of travel is slowed to min- 

 imize swinging of tlic load and the lines are tensioned in order to set the logs on the 

 landing area (fig. 12C). The chokers are unhooked from the logs and flovvn back to the 

 choker setter as the cycle starts again. 



