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mounting external generator


KEVIN

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hey guys , i own a 1986 toyota dolphin 21 ft. camper is prewired for genenerator, unfortunatley no funds to mount one in compartment. i am considering mounting a portable coleman on a platform 30in.x30in.off of the rear bumper,will i be wise running this gen. while drivivg to power everything, and should i weld gen. to platform (theft deterrent) thanks

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will i be wise running this gen. while drivivg to power everything, ................................................................................and should i weld gen. to platform (theft deterrent) thanks
Why do you want to run generator while driving? The only reason to run it while driving that I can see would be to run the roof air conditioner which it likely does not have enough power to run.

As to welding it to platform, I think it would be better to be able to remove the generator from the platform if you want to use it. Being attached and so close to camper would tend to drive one crazy after a short time. I think one would want to remove the generator to as far away as the campers shore power cord will allow. That would keep the noise under control.

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hey pat, thanks for the reply. the gen. is a 4kw. with 4 kids (4,9,15,16) t.v.,video, dvd player would be nice on long trips. no a/c this time of year (mass.) not sure if inverter would run everything .also i am welding an automotive muffler on the gen.,should quiet it down considerably.i just want to make sure any external gen. is safe to run while driving. thanks again

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If its like my Toyota first thing that comes to mind is the weight on the rear bumper the frame under the back is weak,as to the noise I tried to muffle down a welder didn't work. The quiet one's, its not just the muffler the eng is designed for it.

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  • 5 months later...

On this other RV Forum my handle is Hoochonwheels. I posted a how to for external gensets and here is a copy of that post:

AW, heck! I'll post the URLs and you can take a look.

http://i23.photobucket.com/albums/b364/BBLoA/MVC-001F.jpg

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http://i23.photobucket.com/albums/b364/BBLoA/box1.jpg

http://i23.photobucket.com/albums/b364/BBLoA/box2.jpg

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The lightweight aluminum angle ($10.00) will be placed inside the box and secured with RTV silicone ($8.00) and pop rivets($6.00). The steel 3/4" X 3/4" angle (10.00) will be welded into a rectangle that allows your furnace duct work metal box to sit in with a fairly snug fit. While at the welding shop you will need to have two pieces of angle steel made that will be the saddle for your box ($ Cost will vary mine was around $8.00). They will be attached across the bottom of the steel angle iron frame built for your box. My trailer drawbar (tongue) is the same with as the receiver on my Reese Hitch which made it very simple for me. I wouldn't have to use a spacer for my saddle to fit either the trailer or a 2" X 2" X 36" X 3/16" square tube steel. **Don't scrimp here this drawbar takes a lot of stress holding a 75-100 lbs. generator.** The two pieces of angle that form the saddle will vary depending on your trailer drawbar and the weight of the generator. Also if you want to carry only the generator you may have to add some spacers (washers) would work great if trailer drawbar and Reese Hitch bar insert is different.

You will see from the photos how I installed the lightweight angle as corner support and sealer. Use plenty of RTV silicone and after pop riveting these braces in place the excess can be removed rather easily after it cures. Also use the RTV sealant generously in the angle iron frame to prevent water from being trapped between the frame support and the box.

""Notice** Pay attention to your oil dipstick, on/off/choke control and spark plug location. With proper planning you will be able to access these componets without having to lift the generator from the box.

The lid with the overlapping lip can be sealed using foam insulation tape around the inside that meets up with the top edge of the box. In the center of the lid you will be cutting a hole to acommodate a house roof vent. I used a PVC type roof vent that allows a large volume of air to flow freely. You will see once again where the lightweight aluminum angle was used to reinforce this area and allow the mounting of the fan.

The fan is a low profile automotive radiator fan that will be powered by the 12 volt charge circuit on the generator A pin switch can be used to control the on/off of the fan if you don't want to start your generator with even a very slight load on this circuit.

In the bottom of your box you will need a fuel resistant mat. I elected to use a mat from Tractor Supply that is made for horses to stand on while in transport. It is reticulated and allows air to pass through and also absorbs even more vibration from the generator. Cut mat to fit. In the bottom of the metal box you will be cutting vent (intake holes) I used soffet vents like used in the eves of some houses most of these are louvered with a screen on the backside to prevent wasp and other pest to pass through.. You need to be generous with these vents because even though the mat is a lace work it will restrict some aiflow. You want the fan to be free and not pulling any negative pressure inside the box when running. This can be checked by raising the lid with fan off and fan on. You should feel no increase in the force needed to raise the lid. This means you have maximum airflow. The placement of the bottom vents should be placed according to the design of the generator. You want plenty of air flowing across the engine as well as the head unit (armature) generator.

The puchase of a dogbone adapter for electrical supply can be installed if desired or a simple notch in the top edge of the box for your RV supply cord/cable can be plugged into the generator.

Now for the fun part......

The muffler will have to be outside the box. After trial and error I achieved an 8 degree cooler running temp for the generator in the box than the generator sitting out in the open. This was a temp reading on the cylinder head. The radiator fan and placement of the bottom intake vents circulates the air in specific/critical areas. I ordered a Honda replacement (a new take off from a go cart builder) muffler off Ebay to have the extra manifold and mating flange I cut the muffler away leaving only the flange and stub of tube to attach the stainless steel flex pipe. Then mounting the muffler to the bottom of the box with extra flex tube to move or redirect the muffler noise if need be.

Inside the little Itasca the generator can not be heard however if you stand on the floor you can feel only a slight vibration in your feet. If hauling the box on your trailer? Simply disconnect the trailer from the hitch ball and this vibration is gone. If using the drawbar only you could set the box on the ground but I never felt the need to do so.

Once you have figured the space inside the box needed to access the routine matainance and keep in mind center of balance you are ready to mount the generator in the box. Center of balance is important and don't forget the ventilation holes in the bottom. Here is what the bottom of the box will look like and can be used to figure your center of balance.

______I_I_______ (Inverted diagram) the two verticals are the mounting legs of your saddle. They will straddle your trailer or the drawbar. I used grade #8, 3/8' shank bolts but with careful matching you could use some type of tractor pins for even quicker change over.

By placing the box on a flat hard surface and placing the rubber mat inside and sitting the generator in the box you want it to balance on the two legs created by the saddle. When the box will sit steady on these legs mark and drill though the generator frame and through the top legs of the saddle you made with the angle. My saddle pieces were 6" X 8" which gave me a spread of 16" plus the 2 inch space for the drawbar saddle for a total of 18". I used two high grade #8 bolts and washers which passed through the generator frame, rubber mat, bottom of the ductwork metal box and the upper legs of the saddle. Tighten only to secure do not compress the rubber mat or you will split it and loose the vibration insulation. I used 1/4" shank bolts with self locking nuts and flat washers ($5.00)

This box can be used for extra storage if you want to remove the generator, in my Minnie Winnie this can be a great blessing. For those of you that have the Reese Hitch luggage racks you may want to design your generator cover around the already made luggage rack. Very easy if a little planning is used.

I painted my box to match the color of my MH, I still need to put the Teal and blue stripes on the box but cold weather has set in and this spring I will finish the cosmetics. I preped the box by lightly sanding the galvanized metal and cleaned with muric acid (brick acid)

vinegar or most any mild acid solution would work. I used plenty of high grade primer especially on the joints and seams. I then used an epoxy appliance paint for the color several coats.

I plan on making a couple of additions to the box this spring. Two retractable handles to make lifting more easy. They will also be made to act as supports on the outer edge of the bottom so when the box is sitting on the ground the center saddle will support the weight and the handles will prevent the box leaning to one side or the other. I will make them, when not in use they can be pushed back under the box out of sight and no shin bone busters.

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Kevin, I know several people who run their external generator to power their roof AC while going down the road with no problems. Make sure you have a CO2 monitor when parked. A generator close to the motorhome could have exhaust back up into the MH. Your 4KW gen will power everything in your Toy even a 13.5 roof AC. An inverter will not power a AC unit unless it is a monster and your battery/alternator could not keep up with it.

Phantom, lots of planning went into your box, congrats, looks like a way to go. I appreciate all of the pics, helps other people see what you're explaining. Do you have any trouble pulling trailer, generator/box, bikes, etc down the road?

Allen

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Kevin, I know several people who run their external generator to power their roof AC while going down the road with no problems. Make sure you have a CO2 monitor when parked. A generator close to the motorhome could have exhaust back up into the MH. Your 4KW gen will power everything in your Toy even a 13.5 roof AC. An inverter will not power a AC unit unless it is a monster and your battery/alternator could not keep up with it.

Phantom, lots of planning went into your box, congrats, looks like a way to go. I appreciate all of the pics, helps other people see what you're explaining. Do you have any trouble pulling trailer, generator/box, bikes, etc down the road?

Allen

I bought a resse hitch that was not made for my Toy. I cut the ends off of the hitch and welded plates that extend back into the channel of the frame about 24". This distributes the weight over a wider area and not all the weight is at the very end of the frame rails.

I pull a 6'X8' trailer and two Honda Metropolitan Scooters and really cant tell they are even there.

When going to a primitive site I use a drawbar and mount the box to the square tubing drawbar. With the fan running off the 12 volt charge circuit and the vents I run 8 degrees cooler in the box than sitting outside the box with the Generator under the same load. My wife uses a laser thermometer in her jewelry casting and I took reading directly from the cylender head.

I did have to move the muffler outside the box. I used a stainless steel flex line comming off a stainless rigid hookup and ran it out the bottom of the box. The muffler attaches to what I called the saddle while on the move. Once we get to a campsite with neighbors the 4" stainless flex hose allows me to place the muffler in a direction away from the neighbors. The generator is a 6.5HP Honda 3600 made by Porter Cable. I installed a thermostat cutoff in case the fan was to quit in the middle of the night. Now that warmer weather is here. My kids are going to paint the stripes on the box to match the MH and I will install the retractable handles I mentioned in the write up.

Don't scrimp on the exhaust fan and you don't have to worry about adding an external intake. We used our generator for 3 days straight on the US127 450 mile Yard Sale and never threw a breaker. I had roof air, microwave and coffee pot on in the mornings and did just fine.

I hardwired a hookup so I can use it while cruising but hardly ever do so. The inverter runs the DVD and TV for the kids. If we go out west or down south in hot weather, I will use the roof air while traveling.

Two bolts hold the generator in the box. If we are going to a full hookup site. We remove the generator and drop in a solid rubber mat to keep the water from comming through the airvents in the bottom. The added space is a blessing.

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I read a post here,and someone used one of those cargo racks bolted to a hitch and mounted a toolbox on it then put a gen. in it. I think im going to try that. Ive got a 5000lb hitch welded to the back and have bolted a rack on the back already.All i need is a small gen.,does anyone know the weight limit for the back of a 92 warrior 21 ft. 1 ton. thanks.

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