Field of invention
This innovation relates to a support fixture for impeller shafts of water jets where the
impeller shaft is overhung (cantilever type) and to enable easy and accurate alignment of
water jet impeller shaft on-board water jet class vessels particular for Rolls-Royce (Kamewa)
water jets of IPVs and FPV class of ships. All ships of the above class which were built before
did not have such provision to support the impeller shaft and the same was done through T
supports which needed regular checking of horizontal and vertical movement using dial
gauges. Hence, the challenge to design, develop and successfully implement a new simple,
sturdy and re-usable arrangement for supporting of impeller shaft for alignment on board
water jet class vessels during the construction stage was envisaged.
Background Art
For water jets with overhung type impeller shafts, after the installation of water jets
on- board vessels, the impeller shafts needed to be supported to avoid the overhung self-
weight of the impeller shaft causing any damage to the water jet marine bearings. This is
achieved by applying the specific load as specified by the water jet OEM and then supporting
the impeller shaft in the loaded condition. Traditionally the impeller shafts were supported
using wooden blocks or wedges or using 'Y' supports. But, these kind of supports were not
sturdy in nature which lead to change in position of the impeller shafts both vertically and
side wise. To ascertain the shaft remains in the loaded position, 02nos dial gauges were
used and were to be monitored for any corrective measures on a regular basis. These
monitoring and corrective measures needed to be done on a regular basis till the chock
fasting and installation of the support bearing inside the jet compartment is completed,
which lead to huge loss of manpower by forced idleness.

Object of invention
The objective of the present innovation is to reduce the time frame for impeller shaft
alignment by simplifying the whole process in-order to avoid forced idlness and loss of
manpower. Also, the present innovation is to be much more sturdy, easy to fabricate, easy
to use on-board ship, simple and re-usable.
Summary of invention
This innovation relates to a re-usable fixture which can be used to support the
impeller shafts of water jets to avoid the overhung self-weight of the impeller shaft causing
any damage to the water jet marine bearings.
1. After installation of water jets on-board vessels prior to launching, the impeller
shafts needed to be supported.
2. A support fixture is made with MS angles, MS/SS Hexagonal bolts (jacking
bolts) and Hexagonal nuts to support the impeller shaft after the loading of the shafts to the
requisite load as specified by the OEM.
3. A substantially rectangular fixture is made by welding the MS angles. Holes
are drilled in each MS angle for accommodating the Hex bolts and Hex nuts are welded on
top of each drilled hole to provide the thread for screwing of the bolts.
4. The fixture is welded to the bottom frame of the ship's hull based on the
location of the shaft and MS angles are used in the forward and aft side for providing
support to the fixture.

5. The main support fixture can be removed after the installation of the support
bearing inside the jet compartment and the same can be preserved for use in the next vessel
fo the same series or of the similar class of vessels where the impeller shaft and coupling
diameter is same or lesser size.
Brief Description of the Accompanying Drawings
Fig. 1 shows front view of an impeller shaft support arrangement in accordance with
the present invention.
Fig.2 shows side view of an impeller shaft support arrangement with additional
supports in accordance with the present invention.
Fig. 3 shows the cross sectional view of an impeller shaft support arrangement in
accordance with the present invention.
Detailed Description with Accompanying Drawings
After installation of water jets on-board vessels prior to launching, the impeller shafts
needed to be supported. Before supporting the impeller shafts the shafts needed to be
applied with the requisite load as specified by the OEM. Once the loading of shafts are
completed in the dry-dock, the shafts are to be secured at the loaded position untill the post
launch loading and chock-fasting of the support bearing at jet compartment is done.
Once the loading is done at dry-dock, the position of the shaft is marked with punch
marks made on the fixture w.r.to the shaft position in horizontal and vertical directions

and an "L" gauge is made to check the certified position as and when required. Corrective
measures, if required, can be done by adjusting the jacking bolts in both the horizontal and
vertical directions with reference to the punch marking measured by the previously certified
"L" gauge.
After launching of the vessel, the loading of the impeller shaft needed to be repeated
with the specified alignment load in floating condition and again the impeller shaft to be
secured in the newly loaded position using the support fixture. New punch marks will be
made to the measurement of a new "L" gauge and is certified which will be used to ascertain
the position of the shaft until the chock- fasting and installation of the support bearing
inside the jet compartment is completed. Once the chock-fasting and installation of the
support bearing is completed after alignment of the support bearing the "L" gauges are once
again finally verified to ascertain the position of the shaft in the previously loaded condition
and then the support fixture is removed and preserved for use in next vessel.
In an example, for a particular IPV/FPV class of vessels where the water jets from
M/s Kongsberg (formerly M/s Rolls Royce) this support fixture is made with the following
items.
a) 65mm MS angles, 900 mm long - 2 nos.
b) 65mm MS angles, 550 mm long - 2 nos.
c) 65mm MS angles, 700 mm long - 4 nos. (for additional supports)
d) M20 x 120mm long bolt - 04 nos.
e) M20 nuts-08 nos.
A substantially rectangular fixture is made by welding the 02 nos. MS angles of

900mm long and 02 nos MS angles of 550mm long. 22mm dia Holes are drilled in each MS
angle for accommodating the M20 Hex bolts and 04 nos. M20 Hex nuts are welded on top of
each drilled hole to provide the thread for screwing of the bolts. The said fixture is welded to
the bottom frame of the ship's hull based on the location of the shaft and MS angles are
used in the forward and aft side for providing support to the fixture. 04 nos. MS angles of
700mm long is used as additional supports for the fixture.

Advantages and Uses of Invention
1. The concept, design, fabrication and use of this impeller shaft support fixture
is a quantum leap in the process of alignment of impeller shaft resulting in simplification of
work, huge saving in Man-days by avoiding forced idlness. Ineffective and idle time has
been brought down to zero.
2. The chances of movement of impeller shafts, after securing using the support
fixture, is negligible as the fixture being sturdy in nature.
3. Continous monitoring of the dial gauges is not required to ascertain the position
of the shaft and thereby avoiding loss of manpower.

4. If any change occurs in the position of the shaft, the same can be verified by
using the "L" gauge and the corrective measure can be done very quickly and accurately by
adjusting the jacking screws and thereby saving time.
5. The fixture is easy to fabricate with very minimal components, ease of carrying
& can be removed and preserved for re-use in similar class of vessels.
6. The present invention has a wide range of Industrial application both for naval
ship and merchant vessel construction wherever water jets with overhung type impeller
shafts are being used.
Although the foregoing description of the present invention has been shown and
described with reference to particular embodiments and applications thereof, it has been
presented for purposes of illustration by way of examples and description and is not intended
to be exhaustive or to limit the invention to the particular embodiments and applications
disclosed. The particular embodiments and applications were chosen and described to provide
the best illustration of the principles of the invention and its practical application to thereby
enable one of ordinary skill in the art to utilize the invention in various embodiments and
with various modifications as are suited to the particular use contemplated. All such changes,
modifications, variations, and alterations should therefore be seen as being within the scope
of the present invention as determined by the appended claims when interpreted in accordance
with the breadth to which they are fairly, legally, and equitably entitled.

We claim:
1. An impeller shaft support arrangement for alignment of water jets comprising
of:
a substantially rectangular fixture made by welding the MS angles;
a plurality of holes drilled in each MS angle for accommodating the M20 Hex
bolts and M20 Hex nuts are welded on top of each drilled hole to provide the thread for
screwing of the bolts;
wherein the said fixture is welded to the bottom frame of the ship's hull based on the
location of the shaft and MS angles are used in the forward and aft side for providing
support to the fixture.
2. The impeller shaft support arrangement as claimed in Claim 1, further comprising
04 nos. MS angles for additional supports for the said fixture.
3. The impeller shaft support arrangement as claimed in Claim 1, wherein the said
fixture is made by welding the 02 nos. MS angles of 900mm long and 02 nos MS angles of
550mm long.
4. The impeller shaft support arrangement as claimed in Claim 2, wherein the additional
supports for the fixture include the 700mm long MS angles.

5. The impeller shaft support arrangement as claimed in Claim 1, wherein the said
holes of 22mm dia are drilled in each MS angle for accommodating the M20 Hex bolts.
6. The impeller shaft support arrangement as claimed in Claim 1, wherein the said M20
Hex nuts are welded on top of each drilled hole in order to provide the thread for screwing of
the said bolts.
7. The impeller shaft support arrangement as claimed in Claim 1, wherein the said
fixture is configured to fasten the impeller shafts and prohibits any kind of movement.
8. The impeller shaft support arrangement as claimed in Claim 1, wherein the said MS
angles and adjustable bolts with nuts on all the four sides are configured for securing and
adjusting vertical and horizontal movements of impeller shafts during alignment.