CLICK & CLACK : Cup 'o Joe, on the Go

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Sunday, June 21, 2009

Dear Tom and Ray:

I want to add a comical touch to my car (when and if I ever get one). I was thinking about affixing a coffee mug onto the roof right above the driver's seat, as if I forgot my morning coffee. I think it would be funny to see me driving down the highway, 70 mph, with my forgotten drink clinging to the roof of my car. I have two questions: (1) What glue do you guys suggest so as not to have the paint eaten off the roof of my car? Or some other form of attachment? (2) Do you guys think this is funny?

-- Victor

TOM: I think it's very clever, Victor. I know there are serious people all over the place who will disagree with me, but I think we all need a few more laughs these days.

RAY: I think the only concerns relate to safety. You don't want the cup to fly off when you're going 70 mph and hit some other car in the windshield. Or even just scare another driver if it comes flying at him.

TOM: So, forget about glue. I wouldn't trust a commercial glue in that situation, at those speeds. What you need are sheet-metal screws. And I'd suggest you use a plastic mug.

RAY: Place it where you want it on the roof, and then drill four screws right through the bottom of the mug. Be careful that the screws aren't too long, or they'll stick down into the passenger compartment.

TOM: Right. Then when you go over speed bumps, you'll bounce up and get four holes in your head.

RAY: Then, to prevent leaks into the car, cover the tops of the screws with a clear, silicone caulk. And draw a bead around the outside of the cup, too, to prevent water from coming in underneath it.

TOM: I have a few concerns about the distraction it may provide to other drivers. I wouldn't want anybody getting obsessed about your coffee mug and causing an accident while frantically trying to signal you to pull over. But I think the vast majority of people will just smile and shake their heads.

Dear Tom and Ray:

My son, who transports cars for a living, says that we should not put a car battery on the garage floor for more than a few moments while we're moving it from one place to another. In other words, we should never store it on the garage floor. He claims that it will discharge. He says it happens to them all the time. Now, I'm an electrical engineer. Nothing in my knowledge, training or experience tells me anything about cement garage floors being in any way, shape or form conductive, or in any way a cause of battery discharge. Which one of us is nuts? -- Tom

RAY: Your son is. We've always been told not to leave car batteries on garage floors, too. But that's so other mechanics won't trip over them.

TOM: Cement is not conductive. You're right about that. But any rechargeable battery -- that's left anywhere -- eventually will lose its charge. Rechargeable batteries are particularly quick to discharge. Just like your cellphone's battery runs down when it's sitting on the kitchen counter overnight.

RAY: There are some people who have told us that this old myth comes from the days when battery casings were made out of wood. If the battery acid spilled out, it could make the wood wet, and create a conductive path to a moist cement floor. I wasn't around when batteries were made out of wood, so I don't know.

TOM: Another theory is that garage floors are simply colder than, say, workbenches. And, as every electrical engineer knows, chemical reactions slow down in lower temperatures. So, while the battery might not be discharging on the cement floor, it might be cooling off, and be less able to pump out its power temporarily.

Got a question about cars? Write to Click & Clack in care of The Post, or e-mail them through http://www.cartalk.com.

2007by Tom and Ray Magliozzi and Doug Berman


© 2009 The Washington Post Company

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