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Chuck MC8 (207.69.10.158)

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Posted on Saturday, October 19, 2002 - 6:49 am:   

I plan to install a 4.5 Onan RV genset ( 2 cyl gas eng) in the area that formerly housed the A/C condenser in my 1977 MC-8.
That bus access door is expanded metal. I would like to make the setup as quiet as possible, So I thought of replacing the expanded metal on the door with solid sheathing. ( my mc8's siding has been replaced with smooth siding).
I am wondering about cooling the generator. It's air cooled, of course, and (blows) vents
through the floor. There are already two louvered vent holes in the floor from the factory a/c installation. So,I believe it could use one of these for the engine blower to discharge heat. Would then the other vent hole provide enough incoming air for it's needs?
I had thought of using one of those household digital thermometers that measure "indoor and outdoor" temps, and locate one of those sensors in the
"box" with the gen, so I could monitor the temp from inside the coach.
Also, I assume the mufffler has to go umder the coach....do these have a tendency to fall victims to "speed breakers" in parking lots?
Thanks for your thoughts.
Ross Carlisle (Ross) (216.107.197.199)

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Posted on Saturday, October 19, 2002 - 8:47 am:   

The cooling air intake should be a reasonable distance away from the air exhaust or you will just be recirculating hot air. The intake should be in the door if the exhaust is in the floor.

I just installed a powertech diesel. The principles are the same. It exhausts through the floor and they specifically warn against taking your cooling air intake from the floor.

The exhaust should be as close to either axle as possible. The closer the muffler is to an axle the less of a change there will be of high centering on the genset muffler.

I've also found that most of the noise from these gensets comes from the blower, not the engine. Unfortunately, there is really no way you can muffle the blower noise without resticting air flow.

My Powertech makes hardly any engine noise, it's all blower noise. It's pretty loud from outside the bus, but you can hardly hear it from inside. After the interior is in and I insulate the genset bay a bit more, it should be almost silent from inside the bus.

Ross
Peter Broadribb (Madbrit) (216.67.207.36)

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Posted on Saturday, October 19, 2002 - 2:03 pm:   

Looking at my old Apollo, if you close off most of the mesh leaving a 4-6" wide band at the opposite end of the compartment to the blower exit which should be through the floor. Then insulate the door with foam sheet to the level of quietness you want. Bend up a piece of sheet metal into a "Dog-leg" cross-section and afix it to the door over the remaining opening. This is to divert the incoming air to the end of the compartment and also give a restriction to help reduce escaping noise. Make sure it leaves enough room for air to pass by. You can insulate this piece too but is a little harder to make it work on the bends unless you can stick the foam to it without the heat unsticking it later.
If you don't understand what I am trying to say, go look at any older motorhome and see how they have done it. It is a fairly standard method. Another way is the mount a thick sound insulated panel on stand-offs, to the inside of the mesh door. Leaving room aound the edges for the incoming air to pass by.
To reduce dust being blown by the exiting air from the blower, put a horizontal plate a few inches below the exit,this will make the air go forward and backward and not down.

Peter.

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