quiet box for a gen set

[busshawg]

I put this post on the other board as well as I need all the help I can get , haha.  I am going to start building a box to install my gen set in. I have the specs as to the size and I will be using fire retardent insulation. My question is has anyone used wood to line the inside of their box and what are the chances of it catching on fire. What is a good material to use to build a box. I don't have any room on the inside of the old A/C compartment so it will be a 3 sided compartment with the top insulated as well. I am istalling it where the A/C condesor was on my MC9

Thanks in advance

[Stormcloud]

Hi, Grant:

Sorry I cant help you with the quiet box.,I havent done mine yet....but we're gonna be into Wpg and return on Saturday Apr 4 with the bus, so if you're around on Saturday later in the day (4-5ish) maybe we can meet for coffee.
7-two-4-7-oh-6-1.

Mark

[busshawg]

That would be great , would love to see your bus!!

[blue_goose]

I am now building the third quit box for my generator.  Not that I needed 3 but this will be the third time I have moved the generator.  My box is built out of one half in plywood and insulated with soundown.  It has always been quit and I don't think there is any way for it to catch on fire.  Pine doesn't start burning until it gets to about 475 degres.  Your generator will quit long before that.  This time I am putting the radiator in a different location to try and keep it cooler.  The problem that I have had before was the location of the fan was pulling dirt into the radiator and making it overheat. 
Jack

[gus]

I built a 3/4" plywood box for my genset, lined it first with heavy auto floor sound deadening material and covered that with fireproof sheeting from EHP. 

It is a Honda EV6010 gas, water cooled genset which is pretty quiet to begin with and is really quiet in the box. The box has a 3" opening across the top front for air intake and has openings in the bottom for hot air exhaust.

If you make a box I recommend at least openings so air can circulate.

I used plywood because it is much easier to work with and absorbs sound better than metal.

[Tim Strommen]

Use "rockwool", not animal wool.  Rockwool aka. "mineral wool" or "mineral fiber", is non-flamible.  Rockwool is prettly much the industry standard sound control product (there are other products, but the cost can't be beat...).

Doing a mylar faced vinyl-limp-mass on the inside face of the rockwool will cut down the low frequencies and keep the heat in the box (so the fan can correctly dispose of the heat) - the limp-mass is like a lead sheet, it's heavy so it resists the force of soundwaves against it.

Isolating the genny from the enclosure by using soft rubber mounts will help keep vibrations from getting to the genny case itself. If not isolated, you may find that the enclosure radiates vibration from the genny as sound (defeating the purpose of building it in the first place).  Use the softest isolator you can that will support the weight (some high $$$ gennys use air-bags ).  Likewise, having a flex joint in the exhaust piping will keep the exhaust system from radiating mechanical vibrations that originate from the engine (a small resonator attached to the engine, then a flex joint, then the real mufler vibration isolated from both the engine and the enclosure should make for a quiet genny).

Remember, sound doesn't like to go around turns - the more of them you use in your intake and exhaust openings (assuming you have the insides covered with rockwool for absorbtion), the quieter it will get.  Also if you allow for progressively larger openings as the air gets further away from the engine in your duct work, the slower the air will move which should reduce the "rushing air" sounds (and if this is coupled with lots of turns in the ductwork, should kill off most of the higher frequencies).


If you go with a liquid cooled genny, try to build two separate chambers for the engine/alternator and the radiator.  The high volume fan for the radiator makes different sound than the engine/alternator does, you can better "tune" the separate chambers to damp the noise from each source separately.

-Tim


EDIT: Sorry, forgot to mention another usefull tidbit that sound is very directional (especially the higher the frequency).  Ducting the intake and exhaust openings away from "people ear level" and then ensuring that the opening is facing away from the ground (like straight back and up from the bus along the roof line for the exhaust, and perpendicular to the side of the bus for the intake).

You also want to make sure that your enclosure is sealed except for the intake and exhaust that you intend.  Sound will find and exploit any cracks or small holes for it's own purposes -T

[Kwajdiver]

My gen set is water cooled.  The quiet box came with the unit.  I vented the side of the bus, which was great ideal, it really sucks in the air.

Bill

[Dreamscape]

Bill, Where did you get the scoops? Are they off a boat?
Looks great!

~Paul~

[Kwajdiver]

They are Stainless Steel, from Boating USA, or Boating World.  Took a hole saw and just started cutting away, with Fred's help.

Bill

[Tenor]

Here's the box I built.  Just used 3/4 inch plywood, 2 115 cfm pancake fans.

[Tenor]

Here is the intake fan




And here is the exhaust fan.  The genset is thermostated to 170.  So far, it really doesn't heat up the box at all.

[TomC]

In my AMGeneral Transit, I built the box next to the drivers seat like a front engine.  The genset had to be installed through the front door and is serviced from inside.  The base is built from 1/4" steel plate with angle iron welded to the perimeter to bolt the 3/4" plywood sides to and have 1" leaded foam insulation screwed to the plywood.  The cabinet is so tight that the radiator is remote mounted under the drivers seat with a 1/2hp 2spd belt driven squirrel cage blower-high speed for day use, low speed for quiet night use.  For ventilating the cabinet, I have a 8" bathroom ventilator that is 250cfm from Graingers splitting into two 6" hoses on a rheostat.  Works well and is quiet enough where Dick Wright didn't think it needed any further quieting.  Good Luck, TomC

[buswarrior]

Our fellow busnut Jim Shepherd sells fire detection, heat monitoring and suppression systems for generator compartments as well as the main engine room.

http://www.rvsafetysystems.com/index.htm

Support your local busnut!

happy coaching!
buswarrior

[Marcus]

Sucking air from the side of the coach and blowing it out the bottom will keep your whole unit clean and cool. In 5 years I have not had the genny over 190 degrees and I live in Florida.

[edroelle]

Grant,

I just sent you a copy, at your email of record, of the generator seminar I gave at Bussin 2009.  It has some theory and practical information for building an enclosure for noise reduction and cooling.

Ed Roelle
Flint, MI