Critical Speed Of Mainshaft; Jet Mainshaft Alignment - Hamilton Jet HJ212 Installation And Service Manual

Design Basics

Critical Speed of Mainshaft

C.W.F. Hamilton & Co. Ltd. must be consulted when calculating the critical speed of the jet
unit mainshaft.
The heavier splined end of the universal driveshaft should be fitted towards the engine.
If a heavy driveline is used then a transverse vibrational analysis of the jet unit mainshaft should also be
done.

Jet Mainshaft Alignment

If the jet unit mainshaft is inclined at an angle of 5° to the intake base and the port and starboard jets are
mounted at the hull deadrise angle, then the jet mainshafts are no longer parallel to the keel line in plan.
The following table lists the angle deviation of the jet unit mainshaft when the jet base is mounted parallel to
the keel line.
A Plan view
B Section through keel line
C Isometric view
1 Jet unit mainshaft
2 Mainshaft centre line
This diagram applies only to jet units where the mainshaft is inclined at 5° to the intake
base.
Figure 9: Jet Mainshaft Alignment
3 Transom
4 Keel line
P Port jet
S Starboard jet
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Installation and Service Manual