Generator 2pole (3000rpm) vs 4pole (1500rpm) power/size Q

[kashurst]

5Hp is 3.7 Kw, or with a resistive only generator load 3.7 KVA. So you could split the engine from the alternator with some belts to reduce the engine speed. Needs some engineering drawings and some poly V belts etc. Do-able. Possible easier than replacing the gennie if the max output is acceptable.

 

[vas]

I will send you some pictures tomorrow, I have one here in bits at the moment.

thanks A, although you missed the thread and came across them by accident in a Spanish bowrider search thread

as I thought quite a job getting pulleys with keys that will fit on the crank and gen, tensioner, plate where they all attach, change of balance for the whole setup meaning redoing the whole subframe and supports and a few more jobs in the process. Reasonably easy if you start afresh, not that easy doing such a mod, too many things to alter, I'll probably just end up upping the insulation and learn to live with 45dB when the engine is running, would be nice to have 40dB on the aft deck and salon though!

we shall see,

cheers

V.

 

[vas]

Went about with my mobile with a dB soundmeter app and measured the following:
aft deck 49dB
salon 48dB
lower helm 47dB
corridor at the cabin level 44-45dB
bow cabin door closed 39dB
salon with gen off 25dB

me again, waiting for some stuff to arrive, so got 4sqm of 5cm closed cell sound insulation (the cheap black stuff, couldn't find anything else readily available) and had a go at the salon insulating the e/r outlets of the salon level ok behind furniture but still sound was going through and carefully sealing smallish gaps (ok, some were up to 8mm...) as well as the rear side of the small sofa and cabinet panels.
after 3h work had an audible improvement verified by the soundmeter app on my mobile:
aft deck 46 from 49
salon 45 from 48
lower helm actually slightly more
corridor and bow cabin no change, they'll only improve if I seal the bow bulkhead of the e/r where the diesel tanks live, but I doubt I'll ever do that.

anyway, I've only done just over half of the salon stbrd side (generator is on the stbrd side of the e/r) will probably finish that over the w/e and then stuff the rest of the material behind the sofa on port side. I'll be v.glad if I manage to go down to around 40dB and then wont bother with changing gen to a 1500rpm one I recon...
I know it's a v.ambitious target, but it has softened the "hammering" of the small motor at 3k rpm and sounds smoother.

cheers

V.

 

[BartW]

Hi Vas,
I learn that you don't want to "case" your generator,
because you want to "see" it,
I can totally understand, we had 3 cases of nearly catastrophic accidents * with the genny...

but nonetheless, there are perfect solutions adding some alarms on it,
also usefull when the genny is running when you are NOT in the engine room

so therefor I think that casing the genny still is a good idea, and can give you up to 10db extra isolation,
and with your skills with grp and wood + foam, not a big deal..
let alone adding a few simple alarms


*1 rotten hose, behind seawater pump, pumping seawater straight into the boat,
luckyly the engine over temp sensor stopped the genny running

*2 pully of the seawater pump free , not spinning , pump not working, we saw that during a maintenance job / test

*3 forgot to open seacock after winter maintenance, melded impellor and seawaterpump started leaking

 

[vas]

thanks Bart,

yes, I've setup my yanmar with the following:
Linear actuator with feedback operating the governor so that it picks up the revs slowly on startup and drops slowly to turn off
rpm counter
oil press
s/w press (v.useful to either identify blocked exhaust elbow -high press, or failed impeller/closed seacock-low press)
coolant temp
EGT (probably an overkill, I see a fairly constant 200-210C at the exhaust elbow before the mixer, doubt that's going to change much ever...)
these go through a custom box I made to the NMEA2000 bus, so anything off the accepted values will immediately initiate shutdown and report on all plotters or screen running the issue. So I think i'm covered, hence could really do with building a box.
However, since the rebuilt I've not finished soundproofing the e/r so last year I've started with the undercarpet heavy mat and e/r ceiling 40mm decent sound material (two layers of different foamy thing a heavy rubberised/lead whatever layer in the middle and an alluminum foil outside. That's gone well and together with the underwater exhausts has reduced noise considerably, but had lots of areas that needed attention, especially behind the salon cabinet/sofas and the ducts taking the e/r cabling to the helm. This is what I started tackling now.
To cut it short, I'm planning to insulate as well as I can the e/r noise which will obviously lower the engines noise as well, and then if generator still is annoying, I'll think about building a box.
TBH, if I manage to drop to 40-41dB in the salon and 44-45 at the aft deck, I'll call it a day and wont go any further.
dB being logarithmic means it's an awful lot of effort to improve not that much, so not going to loose my sleep over it.

cheers

V.