Mounting a Genset in my Pickup

[bobinyelm]

This may or may not be the right forum, but since all 5ers are towed by pickups (or flat-beds) I thought I might reach the right people here.

I also did a search, but unless I worded the search wrong, I found nothing.

I am interested in building a genset box for my pickup to hold a 3500w (3000w continuous) WEN-Pro Chinese genset. It's your typical tube-frame 3600rpm unit w/ a 6.5hp Honda clone engine and a 4.5gal fuel tank on top. I normally carry a Honda 2000i, but for Summer use, the extra might be enough to power my coach's 13,500 A/C (haven't yet tried it).

I know that it is much louder than my fairly quiet Honda inverter, but for use in Rest Areas and noisy parking lots, I am sure it won't offend too many folks, especially if I can:
1) Adapt some supplemental muffler after the surprisingly quiet factory unit (compared to many older "emergency" generators.
2) Put the genset into a custom box possibly lined with sound deadening material that has adequate ventilation so the unit doesn't overheat. This may involve side doors that can be removed, that open, or incorporate a 110v fan that (comes on whenever the genset is running and) forces air into one end and out the other, possibly louvered end (for rain protection.

Not sure if I want to compartmentalize it to hold such things as the blue-tote, and other equipment, or have it separate between the equipment box and the 5er hitch.

Of course, one would have to consider the exhaust, not only from a noise standpoint, but the fumes. Perhaps incorporate a venturi exhaust into which the muffler would exhaust, with plug-in sections to get it up high, which could be assembled when parked and stationary?

Anyone have ideas or existing designs who would be willing to share their experiences?

I have access to metal bending and tig welding equipment, and was thinking of making the box from aluminum tread-plate of which so many pickup bed tool boxes are constructed.

Thanks-
Bob

[TXiceman]

It is hard to deaden the sound on a cheaper generator. You best bet is to go ahead and buy a Honda EU series or like Yamaha. The majority of thr noise is NOT exhaust noise.

Ken

[bobinyelm]

Originally Posted by TXiceman

It is hard to deaden the sound on a cheaper generator. You best bet is to go ahead and buy a Honda EU series or like Yamaha. The majority of thr noise is NOT exhaust noise.

Ken

I don't think so, but thanks anyway.

[BCooke]

I was looking at a winter or spring project of the same, and concerns of mine were;
Ventillation
Exhaust
Intake air
Cooling
Thought about a double box with some kind of sound reducing properties

[bobinyelm]

I saw a box somewhere that was actually THREE boxes, each smaller than the next so air could zig-zag into the smallest where the genset was located, and all were lined with something like Homosote (like those ceiling tiles).

The Champion 4000 (3500 w continuous) has a noise level of 68db (vs 59db for a Honda), so even moderate attenuation could make one acceptable for use in noisy environments (parking lots, rest areas, truck stops, or enroute).

I have a Honda 2000i for everything but A/C use* which I would consider in a non shore-power campground, so I wouldn't try to make a Champion as quiet as a Honda, personally. Any 3600rpm genset is going to be louder.

Even a simple box with a layer of Homosote and maybe egg-crate foam inside that should knock-off a few db I'd think.

I was thinking of mounting a 120v fan in the box to pressurize it for cooling (louvers at the other end), or to evacuate it. Haven't decided. It would just be plugged into the gen so when it runs, the fan runs.

As for exhaust, maybe make an extension that puts it outside of the box. Whether it need more muffling would be something I'd decide after listening to it.

I am toying w/ the idea of a pin-box mount or a rear receiver hitch mount in addition to the P/U box. Not sure if mounting it on the 5er would make it too noisy or transmit too much vibration to the coach.

*The Honda 2000 will run a 9000btu portable roll-around room A/C. I use this w/ my Sprinter van, and have a piece of 1.4" plywood that cranks into the side passenger window out of which the hot air gets exhausted through it's 5" dia hose. I might take it in the 5er and do the same sort of thing in moderate weather (9000btu won't hack it at 100 deg down here!).

[TXiceman]

For each 3 dB increase in the sound rating, the sound power level doubles...so a 6 dB increase is FOUR time more sound power.

By building a labyrinth for the ventilation air to travel through, you enemy will be the added pressure drop due to the longer air path. The fans may not be able to produce sufficient pressure to push the required volume of air for cooling.

I have worked on low noise air condition equipment and it is a lot more than a box around the noise source.

For the loss of air volume and other fan related items, you will need to look at the Fan Affinity Laws....Fan Affinity Laws

Ken

[bobinyelm]

I have no doubt that you are correct.

I'll do what I can do (measuring the inside-of-the-box temperature and keeping it within reason) and leave it at that.

For $500 or less (genset plus the box), I will at least be able to cool the trailer in high ambient noise areas.

There's nowhere I want to "camp" overnight that's hot enough that I won't have shore power. I detest high temps, so plan to beeline to where A/C isn't necessary in the warm months, at least in the evenings.

If the Champion at 68db (that's the number on the box) is no noisier than the refer units and diesels idling at rest areas and truck stops where I may overnight on my way out of Dodge, I will be satisfied. Sounds like a good excuse to buy a Radio Shack db meter for $50, if nothing else.

Bob
See you're a Ham.
I finally let my ticket lapse, but was very active from 1962 for about 25 years.
I have to say now that I am retired, it might give me something to do on the road.

[jamesgr81]

This has been tried before many times.

The generator will overheat in the box unless it is power ventilated. The mechanical noise will require a large box, walls insulated and more insulation inside. You will need a very large enclosure.

Look at the enclosures for the new trailer mounted quiet diesel gensets used at special events - they are substantial.

The generator will blow up leaving you with a unrepairable China geneset.

[bobinyelm]

Originally Posted by jamesgr81

This has been tried before many times.

The generator will overheat in the box unless it is power ventilated. The mechanical noise will require a large box, walls insulated and more insulation inside. You will need a very large enclosure.

Look at the enclosures for the new trailer mounted quiet diesel gensets used at special events - they are substantial.

The generator will blow up leaving you with a unrepairable China geneset.

Do the fans I mention count as power ventilation?

When I think back on my old Winnebago Class A Motor Home (5500 watt 1800rpm Onan), and my Lance truck camper (3400 watt 3600 rpm Generac) with built-in generators, they had about 8" space all around them, and had NO power ventilation. They had small openings at the bottom and top of their compartment doors which were covered in metal mesh to provide natural convection ventilation, and that was it. In fairness, they had their mufflers OUTSIDE the compartments, though I do plan to extend the exhaust outside my compartment as well.

Wonder how they survived the heat without a problem?

I planned to have far more ventilation than that for my Champion-in-a-box, but maybe you are saying they are far less tolerant of heat than my old RV gensets?

[Engineer Guy]

There's good nuggets of wisdom in most all the comments above. Based on Decades of Sound and Sound Engineering involvement, I'll pass along some fundamentals.

1. IF the vexing cooling issue is solved by Forced Air Cooling, low frequency energy can be tackled. I've used Egg Cartons in Basement Sound Studios, and above ground. Only dense Mass stops lower frequencies. This means an effective Enclosure must be made of MDF or Drywall, etc.. Especially by using MDF, you could have sections clip together so that the Enclosure weight is manageable.

My opinion is that you'll want to line the Enclosure with stapled-on Aluminum Foil or 'Reflectix'. If you 'manage' heat by reflecting it, vigorous Fan cooling will allow that heat to be exhausted. I suspect that heating up the MDF Enclosure will make the cooling situation worse by heating that Mass, which is far more difficult to cool. I suggest not heating that Mass in the first place. I've used Aluminum Foil behind Wood Stoves, and it reflects Heat very well.

The Human Ear is a pretty good relative dB 'Meter'. Instead of an inexpensive dB Meter, consider instead buying a Radio Shack Indoor - Outdoor Thermometer. Use the Outside Probe on a Wire to monitor internal Genny Enclosure Temperature.

2. I've designed Labyrinths made of dense Ceiling Tile for deadening Voice frequencies. They do affect conductance and flow, making Air movement less efficient. Instead, I would design in both an Intake and Exhaust Fan; large diameter Computer Fans, for example. The Intake Fan could be on the bottom of the Enclosure for noise reduction. Perhaps you could start with just an Intake Fan, and monitor internal Enclosure Temperature and dB/noise 'leakage' first before cutting in a 2nd Fan.

3. On my very quiet Kipor 3000 Genny, simply closing the side Door after maintenance really cuts down the noise. It's lined with medium density material that resembles Vehicle Roof Liner 'pad'. The Engine is totally surrounded and enclosed, but Air is drawn in/fumes exhausted to the outside. The Engine bolts to Rubber Pads to isolate it from the Frame.

4. On a Website I can't find to pull up now, some resourceful fellow adapted a Car Muffler from a source like 'Pep Boy's' to his Genny. I've also got a Generac 4500, and it's noisy as all get out. This is why this idea grabbed my attention. The Muffler was mounted in the horizontal plane. The trick was to mechanically mount the Muffler to the Genny Engine; not the Frame. Then, the add-on Muffler moved with the Engine; an important detail. This fellow left the OEM Genny Muffler in place, and adapted that output to the Car Muffler. Of course, the Muffler should safely exhaust to outside the Genny Enclosure.

When you consider how loud an un-Muffler-ed Engine or Motorcycle is vs. a Muffler-ed one, it makes sense that a large Car Muffler would really help w/o restricting Engine performance.

5. Inflatable 'Air Feet' or Pads are used in Labs to minimize Optical Table vibration. They're also used on some Car or Trailer suspensions. They could de-couple Genny Enclosure vibration from the Truck Chassis.

A few dB here and a few dB there will add up to noticeable sound/energy level reduction in the 'right' frequency ranges [long Wavelength Bass].

Newer Gennies have pretty sophisticated Control Boards/Electronics that can tolerate only so much heat. In this regard, they differ from Old School 'blunt force' Gennies.

I would approach this as a 'work in progress' and leave yourself space to implement some or all of these ideas until you're satisfied 'enough' with the results for your unique situation.

Good Luck.

[bobinyelm]

This is an interesting box, though it's for a Honda EU3000i, which is pretty quiet to begin with.

It's commercially made specifically for the Honda, and they say they've sold hundreds to folks for RVs and mounting behind tractor-trailer cabs to power air conditioners and stuff.

It sure is TIGHT (though it has a fan).
Interesting also is that the exhaust is NOT dusted outside, but is discharged in the box enclosure.

Generator Box | HAPCO INC

[w6pea]

Originally Posted by bobinyelm

This is an interesting box, though it's for a Honda EU3000i, which is pretty quiet to begin with.

It's commercially made specifically for the Honda, and they say they've sold hundreds to folks for RVs and mounting behind tractor-trailer cabs to power air conditioners and stuff.

It sure is TIGHT (though it has a fan).
Interesting also is that the exhaust is NOT dusted outside, but is discharged in the box enclosure.

Generator Box | HAPCO INC

yes that is interesting.

[steelpony555]

I would like to see some db ratings under load. The Honda under load increases its rpms but the Champion stays pretty much the same. At idle yeah the honda is definitly quieter, and that is the db's they advertise. I was at a festival where a vendor had a honda and another had a champion. My ear did not detect a whole lot of difference. But then I am half deaf, at least thats what my wife says lol.

[bobinyelm]

Originally Posted by steelpony555

I would like to see some db ratings under load. The Honda under load increases its rpms but the Champion stays pretty much the same. At idle yeah the honda is definitly quieter, and that is the db's they advertise. I was at a festival where a vendor had a honda and another had a champion. My ear did not detect a whole lot of difference. But then I am half deaf, at least thats what my wife says lol.

The Champion says 68db at 50% load on the specifications.

There's NOISE, and there's noise. We perceive different frequencies and mixes of different frequencies and character very differently as humans. 68db of one kind of sound may be preferable than 62db of another just because how it strikes us.

This is an interesting video, but most video cameras have auto sound level, whereby they try to raise ALL sounds up to the maximum practical on the sound track, so hearing difference is difficult. The best way to compare noise on this video is to listen to how loud the announcer's voice is compared to the generator noise while he and the generator are running at the same time, rather than how loud the generator noise is coming from your speakers.

One of the industrial Hondas makes 68db, just like the Champion, so you can compare. I thought the economy 2500 at 69db was actually more pleasant that the 68db one, again, it's perception.

Honda Generator Decibel Levels - YouTube

BTW, there's a YouTube where someone actually ran a Champion genset under different load conditions, measuring the sound level with a db sound meter. The Champion DID measure about 67-68db at half load, and only 69db at full rated load, though the character of the sound was different at full load.

This is a non-professional review of the Champion, BTW:

http://www.youtube.com/watch?v=7vNbp-4aP0s

Bob