--- In [email protected], "Iain Street" <[EMAIL PROTECTED]>
wrote:
>
> Ron Jones wrote:
> > Ann wrote:
> > > Here I am asking for help and advice again :-)
> > >
> > > The restoration of Bluebell is continuing (see
> > > http://www.bridge19-40.org.uk/ link New Boat) and now that the
> > > engine is running, we realise just how noisy a Lister in a
cruiser
> > > stern with absolutely no sound insulation is.
> (snip)
> > Oooo, what sort of Lister? Not renound for their quietness are
they!
> > The less number of cylinders then the more the vibration and
noise -
> > it doesn't really smooth out until 4 cylinders or more.
> (snip)
>
> It's an SR2, on hardwood engine mounts. The current silencing
arrangements are
> a very basic silencer, which I re-covered as it had several large
holes in it.
> --
> Iain
>
I think the advice about the hospital silencer is good, but I also
suspect this will be of more benefit to the steerer.
Being air cooled I think you have a far more complicated job you
would with a water cooled engine because I have yet to see an air
cooled Lister that does not "leak" at least some hot "cooling" air.
When this became excessive on the SL range and the ambient engine
room temperature went up the steel inserts in the piston crown used
to pop out, howevevr I think the SR does not use inserts. AS the
ambient temperature rises the power the engine produces can fall
(expanded air so less oxygen per cu. ft.) and you can also get smoke.
As the power falls the steerer tends to try to raise the revs and
makes matters worse.
On the plus side you should not have the shaft banging about in the
stern gear (as long as the alignment is good) because of the solid
mounts, so that is a large source of "noise" eliminated.
First off Im would try to stop "secondary/sympthetic" vibrations by
ensureing all side and roof panels are well batoned, stiff and well
secured, all seats and tables are well secured or on rubber pads, and
any window hoppers are fitted with thin rubber U section around the
edge. Seales Direct in Hampshire do a catalouge and mail order.
The next step is to try to airproof any engine covers (but beware of
the need to ensure adequate engine air as decribed by other posters).
I fitted rubber U section with a small O section on the top around
the metal upstands that support the engine covers and that made a
fair difference. You can also stick closed cell "rubber" strip to the
underside of the cover boards where they sit on the bearers to
achieve the same thing. All above materials available for Seals
Direct and local "rubber merchants".
Because this is an air cooled Lister I would look very carefully at
the bulkhead between engine and passengers, even if you have to
istall a false one. I am thinking two layers of well bonded 3/4
shuttering ply, firmely fixed and with no openings. If you have to
have a door then the double thickness of ply will allow you to easily
make a large rebate around the appature (again sealed with closed
cell foam strip) with a robust catch to hold it firmely closed.
Unfortunately HSE may demnad the steerer is given ear plugs ;-)
Take great care that such a bulkhead is close fitted and airtight to
the hull, cabin sides and deakhead. Again seek to make all appatures
for wiring etc the minimum size and airtight.
(I know one wde beam boater who fitted a rear bulkhead with a six
inch gap filled with dry (when he put it in) sand to try to deaden
sound). The boat assumeda soemwhat "nose up" attitude - I do not
advise this course of action.)
I do not know how far you have got, but the toilet compartment and
servery located between the rear bulkhead and pasangers may also help
baffle the noise.
Only after that would I start to think about boxing the engine and
gluing sound absorbing material to the inner faces. Howevever I
suspect trying to isolate the customer cabin from the engine and
stopping sympathetic vibrations may well prove cheaper, easier and
allow better access for servicing.
Tony Brooks
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