Sound proof a generator- any ideas?

[MHF]

I need to soundproof (as much as possible) a gas powered generator in some
sort of box with sound absorption. The generator needs to breathe and
exhaust and needs an opening for power cables to exit. Anyone have
experience doing this? The generator is 30"L x 24"W x 25"H and is rated at
81DBA at 7 meters.

Thanks in advance.

Steve

[MHF]

We don't have "film industry" budgets. I need to make it myself, it's a 10 K
gas generator that will be installed in the back of a cargo van.


"Kurt Albershardt" > wrote in message
...
> MHF wrote:
>
> > I need to soundproof (as much as possible) a gas powered generator in
some
> > sort of box with sound absorption. The generator needs to breathe and
> > exhaust and needs an opening for power cables to exit. Anyone have
> > experience doing this? The generator is 30"L x 24"W x 25"H and is rated
at
> > 81DBA at 7 meters.
>
> How big (in kVA) is the genset, and how much is it worth? Good sound
> attenuating enclosures (like those from Matanuska) are not cheap. The
> film industry pays well for quiet power.
>
>
>

[Scott Dorsey]

MHF > wrote:
>I need to soundproof (as much as possible) a gas powered generator in some
>sort of box with sound absorption. The generator needs to breathe and
>exhaust and needs an opening for power cables to exit. Anyone have
>experience doing this? The generator is 30"L x 24"W x 25"H and is rated at
>81DBA at 7 meters.
>
>Thanks in advance.

Is it not already in a box?

The first key here is to start with a generator designed to be quiet. That
means low speed operation and a lot of poles. Then you get a box, and
then you get a special muffler system to reduce the noise leakage through
the exhaust.

It's MUCH easier to get a commercial silenced generator from Honda or
Agreko or one of those guys than try to engineer your own.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

MHF > wrote:
>We don't have "film industry" budgets. I need to make it myself, it's a 10 K
>gas generator that will be installed in the back of a cargo van.

It will cost you FAR more to make it yourself than to buy one designed for
the job.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Kurt Albershardt]

Scott Dorsey wrote:
>
> The first key here is to start with a generator designed to be quiet. That
> means low speed operation and a lot of poles.

And water-cooled, at least for the engine. There are a number of
inexpensive air-cooled 10k units on the market and they are loud.

Water jackets for the alternator is getting a little more exotic, but
also helps things.




> It's MUCH easier to get a commercial silenced generator from Honda or
> Agreko or one of those guys than try to engineer your own.

Yes, speaking from (repeated) experience.

[Scott Dorsey]

Kurt Albershardt > wrote:
>Scott Dorsey wrote:
>>
>> The first key here is to start with a generator designed to be quiet. That
>> means low speed operation and a lot of poles.
>
>And water-cooled, at least for the engine. There are a number of
>inexpensive air-cooled 10k units on the market and they are loud.

Water cooling helps a lot because you can get the radiator outside of
the noisy area for better cooling while keeping the noisy section
sealed up.

BUT, have you tried the little 1KVA units from Honda? Air cooled handheld
things, but very, very quiet. Quiet enough to speak in a normal voice
right next to them.

>Water jackets for the alternator is getting a little more exotic, but
>also helps things.

Only time I ever saw this was on some large (20KVA or so) rental thing
a a music festival in Richmond. I forget who made it but it was quieter
than the Agrekos. I remember looking under the hood and thinking it must
me a nightmare to work on.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Kurt Albershardt > wrote:
>
>Fuel cells are close to practical for some portable apps already. I've
>considered one of the 1.2 kVA Ballard units for awhile and if/when they
>get a decent reformer for LPG it might well end up in my kit. There's
>an educational discount program and I'm starting to think of some
>interesting opportunities that might qualify.

That would be very interesting.

Around here we have a bunch of APUs, basically little turboprop engines
driving 400 Hz generators, which are used to power aircraft on the ground.
They also get used when folks need 400 Hz power in nearby buildings, rather
than dragging a motor-generator set over and hooking them up.

They are ungodly noisy if you are in front of them or behind them, but
90' off-axis you can't hear anything at all other than the reflected noise
from nearby buildings. And the noise is all above 1KC, really, and most
of it above 5 KC, so it shouldn't be too hard to eliminate with baffling.

Somebody has to be able to make a quieted generator with this sort of
technology.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Arny Krueger > wrote:
>
>Freed of the need to run at exactly 3600 rpm, these machines feature low
>speed operation. This also about doubles fuel economy in typical use. The
>new tech generators also have lots of poles (typically 24).

You do NOT want a 3600 rpm generator. Most of the low noise generators
run at 1800 or 1200 rpm, and use generators with additional poles in order
to get 60 Hz at the lower operating speed. The sound difference is incredible.

Doing the inverter trick allows you to get away from the need for tight
speed regulation to get good frequency regulation on the output, but you
can't really run the engines any slower. I've never really looked seriously
at the inverter units, though.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Dale Farmer]

Scott Dorsey wrote:

> Arny Krueger > wrote:
> >
> >Freed of the need to run at exactly 3600 rpm, these machines feature low
> >speed operation. This also about doubles fuel economy in typical use. The
> >new tech generators also have lots of poles (typically 24).
>
> You do NOT want a 3600 rpm generator. Most of the low noise generators
> run at 1800 or 1200 rpm, and use generators with additional poles in order
> to get 60 Hz at the lower operating speed. The sound difference is incredible.
>
> Doing the inverter trick allows you to get away from the need for tight
> speed regulation to get good frequency regulation on the output, but you
> can't really run the engines any slower. I've never really looked seriously
> at the inverter units, though.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

I've started looking at inverters more seriously recently. My brother recently

bought a 'Hunting shack' in NH that he currently has to haul in gas for the
generator for the fridge and lights. He is semi-willing to bankroll a photo-cell
battery bank system for it. Inverters and photocells are a LOT more efficient
nowadays than they used to be.

--Dale

[Steve King]

"Scott Dorsey" > wrote in message
...
> Arny Krueger > wrote:
> >
> >Freed of the need to run at exactly 3600 rpm, these machines feature low
> >speed operation. This also about doubles fuel economy in typical use. The
> >new tech generators also have lots of poles (typically 24).
>
> You do NOT want a 3600 rpm generator. Most of the low noise generators
> run at 1800 or 1200 rpm, and use generators with additional poles in order
> to get 60 Hz at the lower operating speed. The sound difference is
incredible.
>
> Doing the inverter trick allows you to get away from the need for tight
> speed regulation to get good frequency regulation on the output, but you
> can't really run the engines any slower. I've never really looked
seriously
> at the inverter units, though.
> --scott

I do work for Miller Electric, made in the USA welding equipment
manufacturer. As people switch to their engine driven inverter based
welding power sources, essentially a multi-frequency AC/DC generator, they
are getting as much as 20% fuel savings compared to older technology. They
have several models that weld and generate power at 1200 rpm that are
purchased by customers concerned about noise levels.

Steve King

[[email protected]]

On 2003-09-09 (ScottDorsey) said:
>MHF > wrote:
>>We don't have "film industry" budgets. I need to make it myself,
>>it's a 10 K gas generator that will be installed in the back of a
>cargo van. It will cost you FAR more to make it yourself than to
>buy one designed for the job.

WHat about the real obvious solution? Park the damn thing far enough
away that the noise isn't a problem. WHen we do field day every year
with a ham radio club I belonged to when I lived in IOwa we
would park the gen on a trailer some distance away from
both operating
positions. Yah you could hear it when you stepped outside the
operating position which was in an RV, and you could hear it a bit
from the shelter house, but it wasn't as annoying as the guy mowing
the lawn right outside your window. A couple of heavy duty 100 ft.
cables to get the power where you needed it and you were in business.
I think that's a simpler solution than trying to soundproof the genny
yourself.

I note that in your article you didn't talk about your application for
this, but wiser heads such as the one I quoted are no doubt giving you
the straight poop when they say you'll spend more rolling your own
solution than buying one made for the task such as film crews use. IF
your budget isn't up to that best think about having enough heavy
gauge cabling to get the genny far enough away that the noise isn't an
issue.

REgards,



Richard Webb
Electric Spider Productions
REplace anything before the @ symbol with elspider for real email

--

[MHF]

problem is I need 10K in the van, generator must be in the van, no other
options.


"Scott Dorsey" > wrote in message
...
> Kurt Albershardt > wrote:
> >Scott Dorsey wrote:
> >>
> >> The first key here is to start with a generator designed to be quiet.
That
> >> means low speed operation and a lot of poles.
> >
> >And water-cooled, at least for the engine. There are a number of
> >inexpensive air-cooled 10k units on the market and they are loud.
>
> Water cooling helps a lot because you can get the radiator outside of
> the noisy area for better cooling while keeping the noisy section
> sealed up.
>
> BUT, have you tried the little 1KVA units from Honda? Air cooled handheld
> things, but very, very quiet. Quiet enough to speak in a normal voice
> right next to them.
>
> >Water jackets for the alternator is getting a little more exotic, but
> >also helps things.
>
> Only time I ever saw this was on some large (20KVA or so) rental thing
> a a music festival in Richmond. I forget who made it but it was quieter
> than the Agrekos. I remember looking under the hood and thinking it must
> me a nightmare to work on.
> --scott
>
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

[George]

In article
ogers.com>,
"MHF" > wrote:

> problem is I need 10K in the van, generator must be in the van, no other
> options.
>
> well I guess your ****ed then,asshole.

in case anyone is wondering about the outright rudeness of this post it
is in response to his beligerance, ignorance, and rudeness when a poster
at aapls made a off the cuff remark about the genset being used for
coffee machines.
george

[Arny Krueger]

"Dale Farmer" > wrote in message
...
>
>
> Scott Dorsey wrote:
>
> > Arny Krueger > wrote:
> > >
> > >Freed of the need to run at exactly 3600 rpm, these machines feature
low
> > >speed operation. This also about doubles fuel economy in typical use.
The
> > >new tech generators also have lots of poles (typically 24).

> > You do NOT want a 3600 rpm generator.

Noisy SOBs. They are the ruination of the solitude in what would otherwise
be some of my favorite places. In the woods a typical generator carries for
10-20 miles.

> > Most of the low noise generators
> > run at 1800 or 1200 rpm, and use generators with additional poles in
order
> > to get 60 Hz at the lower operating speed. The sound difference is
incredible.

Of course, with the AC/AC converters, generator speed is irrelevant to power
line frequency. Engine speed is based on power needs. Admittedly you need
some RPMs if you want real power out of a piston engine, but much of the
time it doesn't take much.

Small generators are typically sized to meet peak needs which are often
starting surges from induction motors. That kind of load doesn't last long,
so people end up with a 4 KW generator that only needs to pump out a few 100
watts most of the time.

> > Doing the inverter trick allows you to get away from the need for tight
> > speed regulation to get good frequency regulation on the output, but you
> > can't really run the engines any slower.

Not for peak power. If you ask for 4 KW from a 4 KW generator it's going to
rev up and try to be loud. This AC-AC converter thing could work both ways,
enabling engines to really rev if serious power is required. Since the
intermediate form of power is DC it also enables some battery-based
strategies for handling peak loads. Some high end products claim they will
dip into their starting battery if necessary.

> >I've never really looked seriously > at the inverter units, though.

I hope to never have the need, but I have lost power at home for maybe 12
days in the last two years. Legacy infrastructure sucks.

> > "C'est un Nagra. C'est suisse, et tres, tres precis."

> I've started looking at inverters more seriously recently. My brother
recently
> bought a 'Hunting shack' in NH that he currently has to haul in gas for
the
> generator for the fridge and lights. He is semi-willing to bankroll a
photo-cell
> battery bank system for it. Inverters and photocells are a LOT more
efficient
> nowadays than they used to be.

Some remote entry point cabins in Canadian parks are set up this way. I'm
thinking specifically of the Cache Bay entry at Quetico. They run computers,
lights and communications including a real-time charge card validation link
off solar cells, wet cells, and a generator for back-up. Keeping the
generator turned off most of the time is a good thing.

[Arny Krueger]

"Steve King" > wrote in message
et

> I just heard a report the other day on NPR, while talking about the
> great NE blackout, that some Canadian areas still distribute high
> voltage electricity using DC, which, the claim was, is more efficient
> than AC.


True. Insulation and corona losses are serious issues in BIG power lines. DC
carries 40% more voltage (gosh, that's nearly twice the power!) for the same
peak voltage. Some insulator stacks are like 20 feet long and weigh
fractions of a ton. You've got a minimum of 3 (often 6) of these swinging
from a line 80 foot+ towers dancing across farmer's fields, over mountains
and through suburbs.

Solid-state rectifiers and inverters have made all the difference.

Back in the old days people tried this trick with mercury vapor tubes and
motor-alternator sets with the motors connected in series and the
alternators hooked in parallel. Not a pretty picture!

[Scott Dorsey]

MHF > wrote:
>problem is I need 10K in the van, generator must be in the van, no other
>options.

How far away from the van do you have to be working?

If you can keep the van a few hundred feet away from any place where you
are working, you might be able to get away with some of the cheaper stuff.
Even so it will be loud just because the engines themselves produce a
lot of noise if they aren't specifically designed to be quiet.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Dale Farmer]

Kurt Albershardt wrote:

> Dale Farmer wrote:
> >
> > I've started looking at inverters more seriously recently. My brother recently
> > bought a 'Hunting shack' in NH that he currently has to haul in gas for the
> > generator for the fridge and lights. He is semi-willing to bankroll a photo-cell
> > battery bank system for it. Inverters and photocells are a LOT more efficient
> > nowadays than they used to be.
>
> For a small system like a cabin, it's often more efficient and less
> expensive to use DC for the whole system. DC fluorescents, LEDs, and DC
> fans can be very efficient. Sometimes an inverter is useful for
> auxillary loads but often I find you can dispense with them completely.

Yes and no. It's not a question of pure efficiency. The fridge is already there,
and it's one of those dorm sized fridges. It's mostly just for keeping milk and stuff,
so it isn't burning lots of power. Place is already wired for AC, and I'd like to keep
that investment. The newest generation of compact flouiresent lamps are lots less
money and I think I'll get better efficiency from a larger inverter than the little
inverter
that is in each little DC fluorescent lamp.
The generator will still be there for charging the battery bank if needed, but much
nicer if it doesn't have to be left running all the time you need lights, and left
running
as they go to sleep so the fridge will still be cold in the morning.
First generation is probably just going to be an inverter and battery bank to be
charged by the generator. Then genny just has to be run for a couple of hours each
day rather than 18 hours or so per day.

--Dale

[Scott Dorsey]

Steve King > wrote:
>
>I do work for Miller Electric, made in the USA welding equipment
>manufacturer. As people switch to their engine driven inverter based
>welding power sources, essentially a multi-frequency AC/DC generator, they
>are getting as much as 20% fuel savings compared to older technology. They
>have several models that weld and generate power at 1200 rpm that are
>purchased by customers concerned about noise levels.

I don't really understand the older technology.

As I get it, the way the old AC arc welders work is that they are just a
single-phase motor that is designed to have a very high impedance, so that
the winding impedance limits the total current that can be produced when the
thing works into a dead short. Right?

It's like using a big resistor to fake a constant-current source?

And I know some of the adjustable ones (we have an ancient Lincoln here)
have an external ballast inductor with several taps, so you can adjust the
total current that can be delivered into a short. This is probably very
inefficient since there are a lot of losses in the whole thing.

And the DC ones are just the same thing with a big bridge rectifier on
the secondary (It's a bunch of mercury vapor cans on the Lincoln), right?

So, with the inverter systems, you are doing the current regulation with
the electronic stuff and saving all the ballast losses?

I've kind of wondered about this.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[LeBaron & Alrich]

MHF > wrote:

> I need to soundproof (as much as possible) a gas powered generator in some
> sort of box with sound absorption. The generator needs to breathe and
> exhaust and needs an opening for power cables to exit. Anyone have
> experience doing this? The generator is 30"L x 24"W x 25"H and is rated at
> 81DBA at 7 meters.

Well, now you should know from the replies received that you can buy
this cheaper than you can build it, especially since you don't know what
needs to be done in order to build it. Reality is a tricky thing.

--
hank alrich * secret mountain
audio recording * music production * sound reinforcement
"If laughter is the best medicine let's take a double dose"

[Kurt Albershardt]

wrote:
>
> Park the damn thing far enough
> away that the noise isn't a problem. WHen we do field day every year
> with a ham radio club I belonged to when I lived in IOwa we
> would park the gen on a trailer some distance away from
> both operating
> positions. Yah you could hear it when you stepped outside the
> operating position which was in an RV, and you could hear it a bit
> from the shelter house, but it wasn't as annoying as the guy mowing
> the lawn right outside your window. A couple of heavy duty 100 ft.
> cables to get the power where you needed it and you were in business.
> I think that's a simpler solution than trying to soundproof the genny
> yourself.

Just remember that 10 kVA at 120V is 83.3A and will require some decent
copper to carry it all. Running at 240V (assuming you can balance the
phases reasonably well) will help somewhat--and most inexpensive gensets
won't output full current at 120V anyway. Be prepared to crank up the
output voltage (not always easy on inexpensive units without mucking up
the frequency) to compensate for line losses.

[Kurt Albershardt]

Dale Farmer wrote:
>
>>> I've started looking at inverters more seriously recently. My brother recently
>>> bought a 'Hunting shack' in NH that he currently has to haul in gas for the
>>> generator for the fridge and lights. He is semi-willing to bankroll a photo-cell
>>> battery bank system for it. Inverters and photocells are a LOT more efficient
>>> nowadays than they used to be.
>>
>> For a small system like a cabin, it's often more efficient and less
>> expensive to use DC for the whole system. DC fluorescents, LEDs, and DC
>> fans can be very efficient. Sometimes an inverter is useful for
>> auxillary loads but often I find you can dispense with them completely.
>
>
> Yes and no. It's not a question of pure efficiency. The fridge is already there,
> and it's one of those dorm sized fridges. It's mostly just for keeping milk and stuff,
> so it isn't burning lots of power. Place is already wired for AC, and I'd like to keep
> that investment.

That pretty well settles it, then. I'm using a marine refrigerator in
my camper but it costs over 10x what a dorm-style unit from Costco does.




> The newest generation of compact flouiresent lamps are lots less
> money and I think I'll get better efficiency from a larger inverter than the little
> inverter that is in each little DC fluorescent lamp.

Probably not, based on my most recent measurements. I'm seeing 120VAC
and 277VAC electronic ballasts with around 90% efficiency which you have
to factor into the roughly 85% efficiency of most inverters running at
1/3rd load. Run just the fluorescent and you get swamped by the 10-20W
idle current on the inverter. Good DC ballasts are running 85-87%
efficient end-to-end, but stay away from the cheap ones. Iota sells
some that will drive a T8 or other full-sized bulb for $28 (versus
$20-22 for a comparable quality electronic 120VAC ballast.)



> The generator will still be there for charging the battery bank if needed, but much
> nicer if it doesn't have to be left running all the time you need lights, and left
> running as they go to sleep so the fridge will still be cold in the morning.
> First generation is probably just going to be an inverter and battery bank to be
> charged by the generator. Then genny just has to be run for a couple of hours each
> day rather than 18 hours or so per day.

In that case, and assuming you're going to be using an AC genset, let me
recommend the Iota DLS series converters for bulk battery charging of
small-medium banks http://www.iotaengineering.com/dls.htm Linear
chargers are notoriously ineffective on most gensets and most of the
competetive switchers are at least twice the price. Drop me an email if
you want more info--I've got dozens of these in service in all sorts of
unusual applications.