The IP address used for your Internet connection is part of a subnet that has been blocked from access to PubMed Central. Addresses across the entire subnet were used to download content in bulk, in violation of the terms of the PMC Copyright Notice. Use of PMC is free, but must comply with the terms of the Copyright Notice on the PMC site. For additional information, or to request that your IP address be unblocked, For requests to be unblocked, you must include all of the information in the box above in your message.How to Make Your Own Portable Air Conditioner Summer's here and we are all sweating. If you spend any time outside, you'll end up wet. Things are worse when you get to hotter climates. Summer is also the time for drives to see relatives, friends and places. But what if you don't have air conditioning in your car, how could you survive a 10-hour journey? It's actually not that bad, because we've lived through those drives without problems, but what if you could make those drives more comfortable?

Instructables user CameronSS posted a guide to help everyone build their own portable air conditioner. This would make any long journey in the car easy to live with. The materials needed to assemble your AC might already be hidden away in your garage. You'll need a portable cooler, 12V battery, fans, and a generous helping of ice. Cameron reports his tests as well. He started his contraption in a parked truck. The temperature was 95 degrees in the shade. The heat outside was 108. Within five minutes of starting the portable AC, the truck had cooled down to 75 degrees, and the air coming out of it was at 65. Two quarts of water had been refrigerated and 8 pounds of ice were used. The ice had melted after 40 minutes, leaving the water at 50 degrees. Still, the output was of 65 degrees. That's a great idea for those long rides. All you need to made this work over a longer period is ice, and you can get that at truck stops and rest stops all over the place. The handy bags they come in could also keep them isolated, and not put water all over the place.

He basically came up with the device with his dad, who let him use an old pickup truck. The trouble is that the pickup truck doesn't have AC. The idea is based upon portable coolers which have refrigeration units built in. The trouble is that these units cost a lot of money, from $500 to $5,000. His solution costs $10. The basic concept is to use a boating bilge pump to circulate iced water through a heater core, thereby chilling it, and to use a pair of 12V box fans to blow air through the heater core. Cameron lists his materials in detail. The most important parts are a bilge pump and a heater core. Making your own AC does involve playing around with wires and electricity in a very limited fashion. You don't need to be an expert and anyone can do this. What's really interesting is that you can scrounge around for these parts and end up paying nothing. We all have stuff lying around in our garages and sheds that can be cannibalized to create the AC. The first step is to create holes in the cooler lid for the fans and for the pump.

The bilge pump is used to power some fans to circulate the cold air that is generated from the AC out into the environment. After attaching the fans and the heater core to the lid, you can attach the bilge pump to the bottom of the cooler. fan not running on hvac unitYou'll connect the output of the bilge pump to the input of the heater core and add some fan guards. my outside ac unit fan not workingThe wiring is pretty straightforward. heat pump and ac unitWires should be coming from the fans and the pump. Use wire to attach them together, reds together and blacks together, and connect them to the 12V battery. To operate it, you'll dump in some ice, 3/4 of the way, and half a gallon of refrigerated water. Make sure that the fans are going the right way, fanning air out of the AC instead of in!

So check out his handy guide over at Instructables. [Instructables via Lifehacker, images via CameronSS]If you’re old enough to remember the 1980s, you’ll recall that mail used to be delivered in Jeeps. They may have looked cooler than the boxy mail vans on the road today, but they were dinosaurs. Now, the current delivery vehicle—the Grumman Long Life Vehicle, or LLV—has become a dinosaur itself. Built on the chassis of the Chevy S10, the aging and obsolete LLVs have puttered past the expected end of their run. Built between 1987 and 1994, the LLVs are in rough shape. A report released over the summer by the USPS Office of the Inspector General estimated that in 2013, the maintenance cost for its 142,000-vehicle LLV fleet was close to $452 million—or more than $3000 per truck. Fuel efficiency was also listed as a concern. LLVs were designed to average 17 mpg (not bad), but the actual number has been about 10 mpg (terrible). So the U.S. Postal Service is shopping for a new truck, and it has issued a request for information from manufacturers interested in providing the new mail-delivery vehicle.

The replacement process is still in the very early stages, but the contract promises to be a lucrative one for the winning bidder. The USPS said it plans to purchase 180,000 vehicles at $25,000 to $35,000 each, a potential $6.3 billion worth of new mail vans. The USPS said that it wants the new vehicle, like the LLV, to have right-hand drive, an enclosed van-style body, a heavy-duty automatic transmission, and a sliding driver door. It also needs to be cheap and easy to maintain and be able to withstand 20 years of severe use, other LLV attributes. But the similarities end there. The new vans will have safety features now standard on passenger cars and light trucks, including a front airbag, tire-pressure monitors, a backup camera, daytime running lights, and ABS. The postal service has also called for more fuel-efficient, less-polluting powertrains and is considering alternative-fuel vehicles for a large part of its fleet. So what does all this mean to the average letter carrier?

We asked a carrier who has been delivering mail for 35 years. Speaking anonymously to avoid ruffling feathers at the top of the postal pyramid, he said that when it was introduced, the LLV was a vast improvement over the old Jeeps, which he described as “pieces of crap” with no power steering and a wide turning radius. But the LLVs, he said, are past their prime. “Right now, they’re rattle traps,” he said. “The heat doesn’t work half the time; they break down a lot; when it rains, water comes in around the windshield and the doors. Sometimes the packages get all wet.” He also ticked off a laundry list of problems with the LLV, which he thought could have been avoided if letter carriers had been involved in the design process. For starters, he said, the exhaust pipe exits on the right side of the vehicle. “They need a carrier to help design the truck, not a bunch of pencil necks that don’t know what it’s like to carry mail,” he said. “The Einstein that invented it put the exhaust pipe on the same side as the driver, so we’re always sucking exhaust.”