TOLERANCES FOR THE MANUFACTURE OF PROPELLERS |
|
It’s for that reason that a classification of propeller’s exists that determine the tolerances that it should have a propeller, according to the necessities of a craft. The ISO 484/ 2-1981 Norm establishes the tolerances for the production of propeller’s in all their geometric dimension. And divide them in the following classes |
Desde el escritorio de
Manuel Paez Coronado |
This norm contemplates all the dimensions of the propeller’s like they are: Pitch, Diameter, Chord Length, Rake, Tickness and separation between blades The norm requests that they are revised the
dimensions of certain radios, this according to the type of propeller that
is manufactured.
|
Class |
Ratio |
S
& I |
Close
to the hub 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95 |
II |
Close
to the hub 0.5, 0.7, 0.9 |
III |
Close
to the hub 0.5, 0.7, 0.9 |
The tolerances in pitch vary between the several
classes how it show the following chart. |
PITCH |
S |
I |
II |
III |
Local pitch |
±
1.5% |
±
2% |
±
3% |
--- |
Prom. pitch for ratio |
±
1% |
±
1.5% |
±
2% |
±
5% |
Prom. pitch for blade |
±
0.75% |
±
1% |
±
1.5% |
±
4% |
Prom. pitch for propeller |
±
0.5% |
±
0.75% |
±
1% |
±
3% |
The
tolerances for the angular deviation between two serial blades are given
according to the following chart.
|
Class |
Angular Tol. |
S y I |
±
1º |
II
y III |
±
2º |
TOLERANCES ON TICKNESS |
Clase |
S |
I |
II |
III |
Max. Tol. with a minimum of |
+2% 2mm |
+
2.5% 2.5mm |
+4% 4mm |
+6% 6mm |
Min. Tol. with a minimum of |
-1% -1mm |
-1.5% -1.5mm |
-2% -2mm |
-4% -4mm |
TOLERANCES ON RAKE |
Class |
S |
I |
II |
III |
Tolerance |
±
0.5% |
±
1% |
±
1.5% |
±
3% |
NOTE: Rake is expressed like a percentage of the diameter of the propeller. TOLERANCES ON THE LENGTH OF THE BLADE SECTIONS |
Class |
S |
I |
II |
III |
Tolerance with a minimum of |
±
1.5% 7mm |
±
2% 10mm |
±
3% 13mm |
±
5% 15mm |
TOLERANCES IN DIAMETER |
Class |
S |
I |
II |
III |
Tolerance |
±
0.2% |
±
0.3% |
±
0.4% |
±0.5% |
All
the previous tolerances define the geometry of a propeller in accordance
with the ISO 484/ 2-1981 Norm.
This contains specified the dimensions of the most common
standard bores, the same as the dimensions of the keyway.
These tolerances are those that they are considered in the production
of any RICE propeller. If you have any suggestions or questions regarding these technical issues, or if you know someone who's willing to receive these technical letters, or if you wish to be removed from our mailing list, please send an e-mail to: technicalletter@ricepropulsion.com |