LinkJac Shafting

ActionJac™ LinkJac™ Line Shafting is used to interconnect the input shafts of Nook ActionJac™ Worm Gear Screw Jacks and Electric Cylinders used in a multiple arrangement (Image 1 in Figure 1 Below). The shafts transfer the torque from the motor to the jack or from jack to jack/electric cylinder or from cylinder to cylinder. LinkJac™ is available in either steel Line Shafting available in standard lengths up to 144", or in aluminum Tubular Shafting with bonded journals of stainless steel available in lengths up to 196". Custom end machining and other diameters are available. Contact Nook Industries for information.

Selection:

There are two major concerns when selecting an interconnect shaft:

  • Critical Speed: How fast will the shaft be turning?
  • Torsional Twist: How much torque will the shafts be transmitting?

The two characteristics of a LinkJac™ Line Shaft or Tubular Shafting which can be varied to accommodate these requirements are:

  • Length of the shaft
  • Diameter of the shaft

When selecting a LinkJac™ Line Shaft or Tubular Shafting, use the largest diameter or shortest length which satisfies both Critical Speed and Torsional Twist equations.

Critical Speed:

The speed that excites the natural frequency of the screw is referred to as the critical speed.

Since the speed can also be affected by shaft straightness and assembly alignment, it is recommended that the maximum speed be limited to 80% of the calculated critical speed value. The theoretical formula to calculate critical speed in rpm is;

NSpeed = .6192 × ( π )2 × Cs
L

WHERE:

N = Critical Speed in revolutions per minute
L = Length of unsupported shaft in inches
Cs = Value list from table below

Torsional Twist:

The degree of twist experienced by LinkJac™ Line Shaft or Tubular Shafting when a given amount of torque is applied. To insure proper synchronization of cylinder motion, it is recommended not to exceed 1° of twist. The theoretical formula to calculate torsional twist in degrees is;

NTwist = T × L
Ct

WHERE:

N = Torsional Twist in degrees
L = Length of unsupported shaft in inches
Ct = Value list from table below
T = Torque

Design Information:

  • The length used in the previously listed formulas is the unsupported length of the shaft. If support bearings are used on the shaft, the length is the longest unsupported length between bearings.
  • The previously listed formulas give a theoretical value of critical speed and torsional twist. Alignment, straightness and stiffness of the system all contribute to determining the actual value.
  • The torque in the system is also limited by the torque capacity of the coupling.
  • Allow appropriate spacing between the electric cylinder input shaft and the LinkJac™ Line Shaft or Tubular Shafting inside the coupling.
  • For some combinations of couplings and electric cylinders, the radius of the suggested coupling is larger than the distance from the center of the worm shaft to the base.
  • Nook Industries offers a range of couplings for use with LinkJac™ Line Shaft or Tubular Shafting and Electric Cylinder products in both floating shaft and supported shaft applications. See pages 82-83 for more information.

Line Shafting

See Image 2 in Figure 1 Below for product diagram.

OD (in) Keyway (in) Keyway Length (in) A B Material Ct Cs Weight/in (lb)
LJ-8 12 - - - - Steel 1,235 3.895 x 105 0.056
LJ-12 34 - - - - Steel 6,250 5.851 x 105 0.125
LJ-16 1 - - - - Steel 19,500 1.168 x 106 0.223
LJ-24 112 - - - - Steel 95,000 1.169 x 106 0.502
LJK-8 12 18 x 116 Full Length - - Steel 1,235 3.895 x 105 0.056
LJK-12 34 316 x 332 Full Length - - Steel 6,250 5.851 x 105 0.125
LJK-16 1 14 x 18 Full Length - - Steel 19,500 1.168 x 106 0.223
LJK-24 112 38 x 316 Full Length - - Steel 95,000 1.169 x 106 0.502

* When adding modified keyways to standard LinkJac™ shafting, please contact Nook engineering.

Metrictubular Shafting

See Image 3 in Figure 1 Below for product diagram.

Metric Tubing OD (in [mm]) Keyway (mm) Keyway Length (mm) A (mm) B (mm) Material Ct Cs Weight/in (lb)
LJT-27 1.06 [27] 5 x 2.5 28 35 14h7 Aluminum 3,375 9.798 x 105 0.035
LJT-40 1.57 [40] 6 x 3 40 45 18h7 Aluminum 12,250 1.504 x 106 0.055
LJT-50 1.99 [50] 6 x 3 50 45 22h7 Aluminum 25,000 1.907 x 106 0.069
LJT-60 2.36 [60] 8 x 3.5 50 55 30h7 Aluminum 43,750 2.312 x 106 0.084
Figure 1