Vibrostop DGC

The DGC style mount provides dual vibration and shock control functionality and is an evolution of the AVAUD where performance has been enhanced by removing size constraints to focus emphasis on the result in terms of shock mitigation. This enhanced shock performance is combined with excellent cut-off of the entire vibrational disturbance band. This is achieved by applying a double winding of wire rope, which makes it possible to integrate the vibration-damping function (defined for short travel) with the shock-proofing function (defined for long travel). In particular, the characteristic vibrational frequency is identical to that under shock (a characteristic that cannot be achieved with simple windings such as in the HP and AVAU lines).

As with the AVAUD, the inner toroidal structure initially provides vibration isolation, but both toroids function to control the movement under shock loading.

Models and Dimensions – DGC

Table DGC

Code number

Load

max travel

fnv

fnu

Dimensions (mm)

Kg

mm

Hz

Hz

H*

D*

L

I

d1

d2

DGC 1 S

10-15

70

7

7

145

200

90

75

9

M10

DGC 2 S

15-20

70

7

7

145

200

90

75

9

M10

DGC 3 M

20-35

70

7

7

150

210

125

105

11

M12

DGC 4 M

30-45

70

7

7

150

210

125

105

11

M12

DGC 5 L

45-80

70

7

7

155

285

180

155

13

M14

DGC 6 L

65-140

70

7

7

155

285

180

155

13

M14

Shock Deflection and Output Shock

The following graph shows the relationship between Drop Height (or input shock in g.m/s), Deflection and Shock Natural Frequency fn_u.

For shock specified as a drop height, the energy depends on the falling height.

Under normal gravitational forces, the instantaneous velocity at the point of impact is specified as ∆V. The output acceleration and the deflection of the isolator depend on the velocity, ∆V and the Shock Natural Frequency (fn_u) of the system.

In all cases, the graph should be used as follows:

Follow the curved line from the drop height H on the left hand acceleration axis down to the intersection with the fn_u value of the system shown on the bottom scale. A horizontal line traced from this intersection point across to the right hand axis will provide the mount deflection in mm.

To determine the output acceleration of the shock mount, follow the straight green line from the right hand deflection axis from the drop height down to the intersection with the fn_u value on the bottom scale and read off the deflection across on the left hand axis.

For example, for a shock mount with a Shock Natural Frequency of 7Hz – for a 50g x 11ms semi-sinusoidal shock, follow the straight green line from the right hand axis from the 50gx11ms mark down to the intersection with a vertical line drawn from the bottom fn_u scale at the 7Hz estimated point. From this intersection, the output acceleration is read off on the left hand scale i.e. approx 15g in this example.

Using the left hand axis, by following the red curve from the 50g x 11ms point, again down to the intersection with the 7Hz fnu value, the displacement is read off on the right hand axis – in this case approx 80mm.

If a higher shock natural frequency is used such as 14Hz, the figures change to 32g output acceleration and 40mm deflection.

Note: different curves and lines are shown for the 50g x 11ms shock depending on the form of the shock – i.e. semi-sinusoidal or triangular impulse. The semi-sinusoidal form represents greater energy than the triangular impulse form and so a larger deflection is required to dissipate this energy.

In the graph it will be seen that reduced values of fnu result in increased deflection and larger reduction in output acceleration whilst higher fnu values result in reduced deflection and smaller reduction in output acceleration.