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Ran D. St. Clair · 07-11-2010, 09:58 PM

Refrigerator Cabinet

It only took about a week to complete the refrigerator cabinet, mostly waiting for paint to dry. The refrigerator bay is probably the simplest bay in the truck with the possible exception of the coat hangar – mudroom nook right next to the entry door. It only has one shelf which holds the refrigerator about 16” off the ground. I added some 1.5” x 1.5” vertical braces below the shelf to help carry the weight down into the floor. The vertical cabinet walls are 5/8” plywood like everywhere else in the truck. The shelf is 5/8” plywood as well.

The Sunfrost RF-12 weighs about 200lb so it is anything but light. I expect the 5/8” plywood shelf would sag under the weight except that it will be screwed directly to the bottom of the refrigerator.

I called Sunfrost and they informed me that the bottom of the fridge is made from ½” plywood. As it comes from the factory it has legs made from 1 ½” by 3 ½” by 1” tall particle board. The legs are screwed and glued to the bottom of the refrigerator. They are actually pretty strong and would be fine for a normal stationary installation, but I don’t need them for what I am doing. I considered making brackets that bolted to the legs but the guy from Sunfrost suggested that I just chisel them off and screw directly into the plywood on the bottom of the fridge. I like that idea because it is simple, stronger than brackets bolted to particle board, and saves an inch of vertical space for more storage.

I realize that screws into the ½” plywood bottom of the fridge won’t have a lot of pull out strength, but if I use about 10 of them they should be fine. Normally those screws won’t have any stress on them to speak of as gravity will be pushing the fridge down onto the shelf. The weight of the fridge will try to bow the shelf down away from the bottom of the fridge in the center, so the screws will have to help hold the shelf up in the center, but that won’t take much force, especially given the short lever arm where the edge of the fridge is only ¼” away from the supporting wall where the shelf mounts.

When I hit a big bump the dynamic load of the fridge pushing down into the floor could be up to 1,000 pounds or more. That’s why I added the 1 1/2” square vertical braces under the shelf, where they can help support the plywood cabinet walls. I anticipated this extra load and replaced the ½ R-Max foam insulation under the ½” plywood flooring with ½” plywood, so it is solid wood or plywood all the way down to the 1.5” thick wooden floor boards.

Immediately after the bump, the fridge and everything else in the back of the truck could go zero G before crashing back down. That means I also need to hold the fridge down, but only a few pounds of force will be needed in that direction. The screws up through the shelf into the bottom of the fridge should suffice for that. Then the shelf itself will be tied into the 5/8” plywood cabinet walls with 5 each of my 1/8” thick aluminum L brackets. Each of those has 2 each #10 screws into the plywood cabinet walls, and another 2 each screws into the bottom of the shelf and all the way up through the shelf into the bottom of the fridge. All that should hold the shelf and the fridge down. Since the cabinet walls go from floor to ceiling, are wedged tightly in between, and are screwed to the inner plywood floor, walls, and ceiling with 6 more of those aluminum brackets per cabinet wall, the whole thing should be pretty solid.

On top of all that, the fridge comes with a couple of heavy steel brackets that are intended to be screwed into the back wall for earthquake safety. I will screw those into my ½” plywood wall so the fridge will be held solidly both top and bottom.

Compared to the vertical loads, the side loads from acceleration and breaking should be pretty minor. If I ever put the truck on its side all bets are off though. The whole structure in there is pretty solid, but not that solid. I doubt there would be much to do after a rollover accident other than set fire to the whole thing…

You may note that there is nothing shock mounted here. I am depending on the truck suspension to smooth out the bumps. I am also depending on the structure of the fridge itself to take the pounding. It seems to be a heavy plywood box so I am thinking it is pretty strong. Most of the components within the walls are fully surrounded by insulating foam, so the stresses are well distributed. The compressor and radiator cooling are wide open on top and well mounted. The doors are well supported with heavy full length piano hinges, so I think it will take whatever reasonable abuse I might give it.

The one thing that worries me is the internal shelves. They are nice looking glass shelves and they mount on rather flimsy looking plastic mounts that plug into holes in the walls. I assume that they are tempered glass and probably plenty strong for whatever static loads they might encounter, but I worry about something hard and heavy bouncing around inside the fridge. That and they are smooth glass, so of course things can easily slide around on them. They can also slide fore and aft on the shelf mounts, and could even fall off the shelf mounts and fall down inside the fridge. I split some model aeroplane silicone fuel tubing and pressed it onto the edges of the glass, and then wedged the shelves in place on the plastic brackets. At least they are now held snugly in place. I may have to replace them with some sort of wire shelves or possibly pad them with some of that rubber waffle mat that they use for shelf liners though.

The refrigerator doors are held firmly closed with magnetic latches. It takes a pretty good tug to open them. Even so, I am not sure that they will stay closed as I bounce down the road. I may have to add safety or travel catches of some sort, but that will have to come later.

The next step is to build the kitchen counter and sink bay. It is probably the most complex of all, so I expect it will be several weeks as I work through it. I still have a lot of little detailed design work to do. I will also be laminating my own Formica counter tops, making custom drawers, and installing the small amount of plumbing that this project involves.

To be continued….

07-11-2010, 09:58 PM	#224
Ran D. St. Clair Senior Member Join Date: Apr 2009 Posts: 212	Refrigerator Cabinet It only took about a week to complete the refrigerator cabinet, mostly waiting for paint to dry. The refrigerator bay is probably the simplest bay in the truck with the possible exception of the coat hangar – mudroom nook right next to the entry door. It only has one shelf which holds the refrigerator about 16” off the ground. I added some 1.5” x 1.5” vertical braces below the shelf to help carry the weight down into the floor. The vertical cabinet walls are 5/8” plywood like everywhere else in the truck. The shelf is 5/8” plywood as well. The Sunfrost RF-12 weighs about 200lb so it is anything but light. I expect the 5/8” plywood shelf would sag under the weight except that it will be screwed directly to the bottom of the refrigerator. I called Sunfrost and they informed me that the bottom of the fridge is made from ½” plywood. As it comes from the factory it has legs made from 1 ½” by 3 ½” by 1” tall particle board. The legs are screwed and glued to the bottom of the refrigerator. They are actually pretty strong and would be fine for a normal stationary installation, but I don’t need them for what I am doing. I considered making brackets that bolted to the legs but the guy from Sunfrost suggested that I just chisel them off and screw directly into the plywood on the bottom of the fridge. I like that idea because it is simple, stronger than brackets bolted to particle board, and saves an inch of vertical space for more storage. I realize that screws into the ½” plywood bottom of the fridge won’t have a lot of pull out strength, but if I use about 10 of them they should be fine. Normally those screws won’t have any stress on them to speak of as gravity will be pushing the fridge down onto the shelf. The weight of the fridge will try to bow the shelf down away from the bottom of the fridge in the center, so the screws will have to help hold the shelf up in the center, but that won’t take much force, especially given the short lever arm where the edge of the fridge is only ¼” away from the supporting wall where the shelf mounts. When I hit a big bump the dynamic load of the fridge pushing down into the floor could be up to 1,000 pounds or more. That’s why I added the 1 1/2” square vertical braces under the shelf, where they can help support the plywood cabinet walls. I anticipated this extra load and replaced the ½ R-Max foam insulation under the ½” plywood flooring with ½” plywood, so it is solid wood or plywood all the way down to the 1.5” thick wooden floor boards. Immediately after the bump, the fridge and everything else in the back of the truck could go zero G before crashing back down. That means I also need to hold the fridge down, but only a few pounds of force will be needed in that direction. The screws up through the shelf into the bottom of the fridge should suffice for that. Then the shelf itself will be tied into the 5/8” plywood cabinet walls with 5 each of my 1/8” thick aluminum L brackets. Each of those has 2 each #10 screws into the plywood cabinet walls, and another 2 each screws into the bottom of the shelf and all the way up through the shelf into the bottom of the fridge. All that should hold the shelf and the fridge down. Since the cabinet walls go from floor to ceiling, are wedged tightly in between, and are screwed to the inner plywood floor, walls, and ceiling with 6 more of those aluminum brackets per cabinet wall, the whole thing should be pretty solid. On top of all that, the fridge comes with a couple of heavy steel brackets that are intended to be screwed into the back wall for earthquake safety. I will screw those into my ½” plywood wall so the fridge will be held solidly both top and bottom. Compared to the vertical loads, the side loads from acceleration and breaking should be pretty minor. If I ever put the truck on its side all bets are off though. The whole structure in there is pretty solid, but not that solid. I doubt there would be much to do after a rollover accident other than set fire to the whole thing… You may note that there is nothing shock mounted here. I am depending on the truck suspension to smooth out the bumps. I am also depending on the structure of the fridge itself to take the pounding. It seems to be a heavy plywood box so I am thinking it is pretty strong. Most of the components within the walls are fully surrounded by insulating foam, so the stresses are well distributed. The compressor and radiator cooling are wide open on top and well mounted. The doors are well supported with heavy full length piano hinges, so I think it will take whatever reasonable abuse I might give it. The one thing that worries me is the internal shelves. They are nice looking glass shelves and they mount on rather flimsy looking plastic mounts that plug into holes in the walls. I assume that they are tempered glass and probably plenty strong for whatever static loads they might encounter, but I worry about something hard and heavy bouncing around inside the fridge. That and they are smooth glass, so of course things can easily slide around on them. They can also slide fore and aft on the shelf mounts, and could even fall off the shelf mounts and fall down inside the fridge. I split some model aeroplane silicone fuel tubing and pressed it onto the edges of the glass, and then wedged the shelves in place on the plastic brackets. At least they are now held snugly in place. I may have to replace them with some sort of wire shelves or possibly pad them with some of that rubber waffle mat that they use for shelf liners though. The refrigerator doors are held firmly closed with magnetic latches. It takes a pretty good tug to open them. Even so, I am not sure that they will stay closed as I bounce down the road. I may have to add safety or travel catches of some sort, but that will have to come later. The next step is to build the kitchen counter and sink bay. It is probably the most complex of all, so I expect it will be several weeks as I work through it. I still have a lot of little detailed design work to do. I will also be laminating my own Formica counter tops, making custom drawers, and installing the small amount of plumbing that this project involves. To be continued….