What resources to look at for building a quiet generator compartment?

[luvrbus]

When those are installed on boats the water is discharged with the exhaust they have water passing through over the exhaust  at all times when running ,My 12.5 was a Universal brand made in WI there was no water in the manifold ,when they sold out to Westerbeke they stop selling mine for RV use     

[belfert]

Would it work to build 2x4 walls with steel studs all the way around the generator and then fill the walls with mineral wool insulation?  I would use heavier gauge steel studs than they sell in the big box stores.

Would the steel studs vibrate or otherwise transmit sound?  I would put plywood on the studs and then a layer of foam on top of that. I need to do measurements to see if walls of the compartment could even be that thick.

[richard5933]

Would it work to build 2x4 walls with steel studs all the way around the generator and then fill the walls with mineral wool insulation?  I would use heavier gauge steel studs than they sell in the big box stores.

Would the steel studs vibrate or otherwise transmit sound?  I would put plywood on the studs and then a layer of foam on top of that. I need to do measurements to see if walls of the compartment could even be that thick.

I would think that it shouldn't take 4" thick walls around a generator to do sounds insulation. That seems like a terrible waste of space. Check out the sound insulation qualities of mineral wool - I suspect that it won't do much for the lower frequency sounds like a lead sheet (or similar substitutes) would.

[belfert]

My generator compartment is where the A/C condenser used to be.  I can't really use any empty space for anything else so I might as well try to isolate the sound as best as possible.  I would still use mass loaded vinyl foam composite on the inside in addition to everything else.

I noticed on Soundown.com they recommend attaching a diesel generator to a steel plate that weighs 50% of the weight of the generator to help isolate vibration.  I have no plans to do that as it would take a steel plate around 250 pounds to make that work.

[luvrbus]

Quite boxes are made of metal ,if you want strength in metal studs you buy boxed studs ,the rock wool I don't think is going to work for you though

[luvrbus]

I would think that it shouldn't take 4" thick walls around a generator to do sounds insulation. That seems like a terrible waste of space. Check out the sound insulation qualities of mineral wool - I suspect that it won't do much for the lower frequency sounds like a lead sheet (or similar substitutes) would.

Richard ,Brian has always asked for ideas and then does it his way which is good IMO

[belfert]

Richard ,Brian has always asked for ideas and then does it his way which is good IMO

I am trying to combine the best ideas you guys have suggested to come up with a quiet generator compartment without breaking the bank.  I was hoping to only spend $2,000 on the generator installation, but I am not sure that is really possible.  I have to rent a skid steer for about $250 just to load the generator into the compartment.  I also have to spend $800 on charge air cooler repair, $550 on new tire pressure sensors, $1,000 on new steer tires, and $175 to replace window glass that a vandal broke.

I looked into the lead lined plywood you suggested, but I am not convinced that it is worth nearly $1,000 for a single sheet of plywood.  The tax, crating, and shipping cost is more than the $450 cost of the plywood.  It really isn't any cheaper to drive to the factory and would take me three days for the trip.  Is sheetrock really a good idea in a bus?  Won't it end up cracking from vibration and the bus twisting going down the road?  Lowes locally doesn't carry the Quietrock at all, but I can apparently get it from two drywall distributors.

I called Soundown yesterday as suggested, but I had to leave a voicemail for someone.  They called me back at the end of the day, but I was driving so I couldn't answer.  I will call them back on Monday.

[richard5933]

Some plywood, contact cement, and a roll of lead sheet flashing? Add to that a layer of dense foam with a foil inner layer and an expanded steel mesh to hold it in place and further break up the sound waves?

[belfert]

Quite boxes are made of metal ,if you want strength in metal studs you buy boxed studs ,the rock wool I don't think is going to work for you though

I'll plan on a steel box then.  I will have to build it in place so I will need to find a mobile welder to do the welding.  I have a welder, but a first grader could weld better than I can.  The welds will need to be continuous and actually penetrate into the metal so the welds don't break.

My only concern about a steel box is the extra weight.  I'm figuring it will take at least 300 pounds of steel sheet.  I'll end up with 1,000 pounds of weight in the generator compartment.

[Jim Blackwood]

Your stud wall idea is interesting, in apartment construction they sometimes build a "party wall" which is a 6" wall based on 2x4 studs with double studs staggered to the opposite edges of a 2x6 plate so the plates are the only connection between the two walls, and then fill with insulation. They work fairly well, since you have to vibrate two separate walls to transmit sound. Removing the direct connection of the plates and the attached walls would make it work even better.

Here's an idea for you, since sound can't travel through a vacuum all you have to do is build a sealed box inside a sealed box and pump out all the air. 
Seriously though, anything you can do to isolate the inner from the outer enclosure is going to help. That's why I suggested two layers separated by foam rubber. A soft closed cell foam would be better and the denser the inner layer the better.

Jim

[DoubleEagle]

I am trying to combine the best ideas you guys have suggested to come up with a quiet generator compartment without breaking the bank.  I was hoping to only spend $2,000 on the generator installation, but I am not sure that is really possible.  I have to rent a skid steer for about $250 just to load the generator into the compartment.  I also have to spend $800 on charge air cooler repair, $550 on new tire pressure sensors, $1,000 on new steer tires, and $175 to replace window glass that a vandal broke.

I looked into the lead lined plywood you suggested, but I am not convinced that it is worth nearly $1,000 for a single sheet of plywood.  The tax, crating, and shipping cost is more than the $450 cost of the plywood.  It really isn't any cheaper to drive to the factory and would take me three days for the trip.  Is sheetrock really a good idea in a bus?  Won't it end up cracking from vibration and the bus twisting going down the road?  Lowes locally doesn't carry the Quietrock at all, but I can apparently get it from two drywall distributors.

I called Soundown yesterday as suggested, but I had to leave a voicemail for someone.  They called me back at the end of the day, but I was driving so I couldn't answer.  I will call them back on Monday.

I'm a frugal cheapskate, and it seems to me that you need to price around some more. $1500 for one sheet of plywood would only be justified if the lining were gold foil, but even then, the price is crazy for the noise reduction you get. Mass loaded vinyl sheets, 12.5 X 4' (50 sq. ft.) by Acoustimax are $64.97 ($1.30 per sq. ft.). Custom Coach (Columbus, Ohio) used cork sheets and lead sheets between layers of plywood to isolate noise. They would probably use mass loaded vinyl nowadays.

Using hundreds of pounds of steel might have a mass absorption factor, but it will surely add to your gross weight and stopping distance. You don't have to rent anything to get your generator in, just jack it up on blocks gradually, and use a cheap come-along to winch it in, or use pipes to roll it in. Tires can be had for less than $1000, and people have survived for decades without tire pressure sensors. Get outside with a tire thumper (or your booted foot) every time you stop. But then, if you have money to burn, send it to me and I'll eradicate it cheaply. 

[belfert]

Notice I said I am not going to pay $1,000 for a sheet of lead lined plywood.  I didn't call anyone else about pricing.  I will probably go with mass loaded vinyl instead.

I have BFGoodrich ST230 steer tires now that I like.  What I really need are tag axle tires.  I will move the current steer tires to the tag axle and get a new set of ST230 tires for the steer axle.  Sorry, I am not going going to put the cheapest China bomb tires on my bus.  $1,000 is just an estimate that might be high.  TPMS sensors are worth it to me.  I have had three trailer tires get punctured by road debris.  How many hours would I have driven with a flat trailer tire without sensors?

[belfert]

What gauge steel would be good to use for an enclosure?  I was looking at 11 gauge (1/8" thick), but that gets heavy in a hurry.  Would you attach it to the structure of the bus, or try to have it freestanding?

The condenser bay I use for my generator is about four inches wider than the door.  I also have to deal with the opening mechanism for the door which intrudes into the compartment.  I am really starting to think I will need to sacrifice some other bay space for the radiator.  There is plenty of room for the generator itself in the condenser bay, but not enough for the radiator too it appears.

My condenser bay runs parallel to the length of the bus.

[chessie4905]

Lead line your own plywood. Install hush mat on opposide side. Hush mat is frequently used to silence car interiors. Mount box on air cushions. Mesh exhaust isolator. Careful isolation for exhaust, power cables, fuel lines going through box.

[Utahclaimjumper]

You should also be able to use an engine puller type cherry picker to install it,, most are good for 1000 to 2500 pounds and on rollers.>>>Dan