26
Chain drive
Assembly and operating instructions
ELTRAL K35 | ELTRAL K35 Synchro
6 Calculating the opening and closing force
NOTE
With the formulae indicated below it is possible to determine the approxi-
mate force required to open or close a (smooth-running) window.
The windows are assumed to be smooth-running. Possible snow loads are to
be considered.
NOTE
The application formula can be used for bottom-hung windows, top-hung
windows, and skylights only.
The permissible drive force is specified in the technical data in section
Technical data (1 motor)“ on page 24.
If the values you calculated exceed the max. allowed force, please contact
Gretsch-Unitas GmbH Baubeschläge
º
º
For roof-lights
Calculating the drive force depending on the sash weight
P
F = 5.4 x P
For vertically installed bottom-hung or top-hung windows
Calculating the drive force depending on the sash weight
P
F
g
= 5.4 x P x C / H
Calculating the drive force depending on the wind load F
W
F
K
= F
W
x A / 2
Calculating the drive force depending on sash weight and wind load
F= F
g
+ F
K
Wind loads depending on the
building height
Height
F
w
0 - 8 m
500 N/m²
8 - 20 m
800 N/m²
20 - 100 m
1100 N/m²
> 100 m
1300 N/m²
F, F
g
, F
K
= opening/closing force [N]
P
= sash weight [kg]
A
= window area [m²]
H
= sash height [mm]
C
= opening width of sash [mm]
F
w
= wind load [—]
5.4
= constant calculated in advance [—]
m
s²
N
m²
