GN 248 Levelling feet with vibration dampening

Photo

ELESA original design
code: LW.A.

Product description

Information

Levelling feet GN 248 with dampening element made of rubber are used to dampen vibrations (oscillations) and shock movements.

This has a positive influence on the life of a machine and helps to abate noise.

Using the details on the maximum static load F, the maximum permissible compression and the resulting stiffness, the achievable degree of insulation can be determined with the help of the method shown on page 921.

The details relating to the load bearing capacity are non-binding recommended values and rule out any liability. They constitute no general warranty of quality and condition. The user must determine from case to case whether a product is suitable for the intended use.

Specification

Vibration dampening element
Natural rubber NR
  • Hardness 80 Shore A
  • black

Reinforcing plate
Spindle head
Support plate
Steel zinc plated, blue passivated

Adjustable spindle
Steel zinc plated, blue passivated
  • Tensile strength class 5.8

Hexagon nut ISO 4032
Steel zinc plated

RoHS

Technical drawing

3D
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GN 248 Levelling feet with vibration dampening element sketch

Article options / Table

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d1d2l1d3d4l2
min.

max.
l3l4s
Square
Static load
in N
Stiffness
in N/mm
max. compression
in mm
80M 12 x 1,251346072385035107500025002
120M 16 x 1,5150801094558411091000040002,5
160M 20 x 1,519210015055704810122000090002,2
200M 20 x 1,5206130186658060101240000150002,7

Build & Price

Foot diameter d1
Thread d2
Thread length l1

Degree of isulation

Degree of isulation chart

Interference frequency [Hz]:
is the frequency emanating from a machine,
e.g. from the machine main shaft speed [rpm].

Static load F [N]:
is the load acting on each vibration-dampening element (levelling foot).

Degree of insulation [%]:
measure for absorbing the interference frequency (dampening)

Compression s [mm]:
is the change in the height of the dampening element (spring excursion).

Stiffness R [N/mm]:
is the load causing the dampening element to be compressed by 1 mm (spring rate).

Determining the suitable levelling foot and the achievable degree of insulation

The first step is to determine the static load F for each levelling foot. With favourably arranged levelling feet and therefore an evenly distributed load F, this value is calculated using the following equation:


Force due to weight of the machine [N] / Number of levelling feet

= static load F [N] for each levelling foot


Use the calculated static load F to select a levelling foot from the table, making sure that the static load F lies as close as possible to the static load capacity without exceeding it. The associated stiffness R of the selected levelling foot is also taken from the table.
The actual compression is then calculated using the equation below:


Static load F [N] per levelling foot /
Stiffness R [N/mm]

= actual compression s [mm]

Starting from the calculated actual compression s, the achievable degree of insulation as factor of the interference frequency can now be taken from the graph shown above.
To optimise the achievable degree of insulation, the number of levelling feet may be changed such that the static load F for each foot is as close as possible below a load capacity value given in the table.
This will increase the compression s which, in turn, results in a higher degree of insulation.
In general it can be said that medium to high frequencies can be very well insulated with sufficient compression.

Example

Static load F (machine weight) = 48,000 N, number of feet = 4, ergo: static load per foot = 12,000 N
Selected foot: d1 = 160, static load capacity 20,000 N, R = 9,000 N/mm
Resulting in an actual compression s of:

12,000 N (static load/foot) /
9,000 N / mm (stiffness R)

= 1.3 mm


With an interference frequency of 20 Hz (1,200 rpm), the above graph delivers a degree of insulation of only about 20 %.

To optimise, the number of feet may be increased to 5, resulting in a static load per foot of 9,600 N. A levelling foot whose static load capacity is closer to the new result may now be selected.
Newly selected foot: d1 = 120, static load capacity 10,000 N, R = 4,000 N/mm
This results in an actual compression s of:

9,600 (static load/foot) /
4,000 N/mm (stiffness R)

= 2.4 mm


With the same interference frequency of 20 Hz (1,200 rpm), the above graph now delivers a degree of insulation of approx. 75 %.

Selected Part (How to order)

Total (net)
35,34
plus VAT 6,71 €
gross 42,05 €
In stock
Weight: 0,500 kg
If this article is new in our product range, it may happen that details concerning weight are as yet not listed.
If you do need weight details, please contact our Sales Department!
Phone+49 7723 6507 - 0
RoHS: Yes
This article is RoHS-compliant in application of Annex III., which means it complies with EU Directive 2011/65/EU, including extension (2015/863/EU), for restricting the use of certain hazardous substances in electrical and electronic devices. The Directive regulates the use of hazardous substances in devices and components. The implementation in national law is summarily described with RoHS(Restriction of (the use of certain) hazardous substances)).
Please note our quantity discounts.
With a total value (net) per order:
from 175,00 Euro -> 10 % discount
from 275,00 Euro -> 20 % discount
from 375,00 Euro -> 30 % discount
With a total value (net) per order:
All prices in accordance with our price list No. 52, valid from 1 May 2019, plus VAT only valid for Germany.

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