Apr 04, 1998
RAY: Ha. We're back. You're listening to Car Talk with us, Click and Clack, the Tappet Brothers and we're here to discuss cars, car repair, and dah --
TOM: And dah --
RAY: The new puzzler.
TOM: Yeah.
RAY: Your recent... My brother took a trip recently.
TOM: Yes.
RAY: He took a trip on the rails.
TOM: I certainly did.
RAY: He told me he was spending a week in Florida. He really spent five days on the train.
TOM: And a day in Florida.
RAY: And a day... But it reminded me of a puzzler of yesteryear.
TOM: Yes.
RAY: Imagine, if you will, a long freight train. Like the kind you see out West. Now a couple of hundred cars.
TOM: Yeah.
RAY: It's pulled into the yard. The train yard and it's stopped and big... I don't know what they do. Gets out to go to the bathroom. All the train workers. They get back in and the engineer opens the throttle and the train starts to pull away from the yard. When they realize it, the caboose has a problem. The brake is frozen on one of the wheels of the caboose.
TOM: How would they know?
RAY: Because the wheel is being dragged and there's... There are sparks and smoke.
TOM: Yeah.
RAY: And someone standing there says, "Stop the train." So, they manage to signal to the engineer, to stop the train. Well, they can't fix it, so they just cut the caboose loose. They remove it and they give him the go ahead. They wave him. You know. Go ahead. He gives it the throttle. The train doesn't move.
TOM: Yeah.
RAY: He gives it more throttle, it doesn't move. He gives it more and what's happening is the train isn't moving, but his wheels are spinning.
TOM: Yeah.
RAY: The cars aren't moving. There's nothing wrong with any of the remaining cars and there's nothing wrong with the engine, but there is something wrong with the engineer.
TOM: Yeah.
RAY: The question is what's wrong with this picture?
TOM: Phew. This is good.
RAY: When a train is... When a locomotive is pulling cars, each car is attached to the one in front of it and behind it by a coupling, but the couplings aren't rigid. They're, in fact, sloppy.
TOM: Um hmm.
RAY: So that when the train stopped and it started to go, you didn't realize that something had happened before that. When a long freight train pulls into a yard, before it takes off, it will frequently back up to compress all the couplings and then when it takes off, one car at a time begins to move and it's quite a while, in fact, before the caboose begins to move.
TOM: Phew.
RAY: But in this situation, the train was stopped. He did that backing up thing. I failed to mention that in the statement of the puzzler.
TOM: Another form of obfuscation and nicely done I thought.
RAY: The train is halted because the brake is stuck and because it's stuck, the caboose is in a sense pulling the train from the other end. So, now all the couplings are all stretched out. They remove the caboose, but the guy doesn't back up.
TOM: Right.
RAY: They give him the go ahead. He says, "OK. I'll go ahead."
TOM: So, now he's going to pull all 750 cars --
RAY: At once.
TOM: At one time.
RAY: He's going to try to move the last car while he's trying to move the first car and the train is just too heavy and he doesn't have enough friction between the wheels on the track --
TOM: So, a train --
RAY: To accomplish this.
TOM: So, a train can't really pull from a dead stop all the cars that you see behind it sometimes.
RAY: If it's long enough, it can't do it.
TOM: It it's long enough, it can't.
RAY: It can't do it.
TOM: So, the little engine that couldn't. Couldn't.
RAY: Couldn't do it.
TOM: It's as simple as that.
RAY: And you have to apply the rules of incrementalism. You have to pull one car at a time until finally you got one car, two cars, three cars, dah-dah-dah, and you've moved them all and once it's moving, of course, you can't stop it because everyone knows trains can't stop for beans.
TOM: Yeah.
RAY: Anyway, who's going to win the new 10th Anniversary Car Talk T-Shirt, this week, Tommy?
TOM: The winner this week is Oliver Gersch. Get this. He's from Dortmund, Germany.
