Bogus answer to squeeking fan belt puzzler

The puzzler answer to What’s Making That Noise is completely wrong. Years ago when they used this puzzler, I contacted their expert at Harvard. He failed to realize that modern fan belts are two part systems. There is a woven belt on the outside that holds the outside circumference constant. On the inside is not natural rubber that contracts when heated. There is synthetic rubber that expands when heated. As the belt slips, it heats up, the synthetic rubber expands. The outside of the belt keeps it from getting larger, so the rubber reduces the inside circumference, making the belt tighter. I verified this with an engineer at the Gates Rubber Factory who said the idea that the belts was shrinking due to it being heated was completely bogus.

Leather belts “shrink” due to over eating.:crazy_face:


And spring loaded serpentine belt tensioners make this discussion moot.


It just bothers me that after talking to Car Talk’s self proclaimed expert, a professor at Harvard, who said that he would tell them to stop using this puzzler after realizing that their answer was bogus, they went ahead and used it anyway and gave the wrong answer. I do not like the idea that they are spreading mis-information, when their own expert says that it is incorrect and he said that he would tell them to stop using it. The relatives of someone who was an expert about belts used during WW1 are not themselves experts by way of genetics. During WW1, they used natural rubber belts because synthetic rubber had not yet been invented, but no one has used them in the last 75 years.

Who was it that said behind every major crisis you’ll find a Harvard man involved? Prolly doesn’t even have a drivers license.

Chuck, you overestimate the amount of technical research behind the puzzlers. These aren’t documented proofs, they’re fictional fun with a few facts added.

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And no one has used V belts for over 25 years and serpentine belts generally without spring tensioners.

Let it go.


If this issue is the biggest problem that the OP has this week, he should consider himself very fortunate.


It seems sort of like that question high tech companies sometimes ask job applicants.

Say you have a thick steel plate with a 1.5 inch diameter hole in it. When you heat the plate will the hole become a larger diameter, or smaller?

Larger… thats how you drop in bearings with an interference fit

If you ever checked the amp output of an alternator immediately after starting the engine and watch it drop from a high amperage to a moderate amperage in a minute or so, you’ll understand the real reason the belt stops slipping after a minute or so. The alternator simply becomes easier to turn. The more amps the battery draws while recharging, the harder it is for the engine to turn the alternator. After a minute or so, the battery is topped off again.

Yeah but if the metal all around the hole is expanding, wouldn’t it expand into the hole and make it smaller? I wouldn’t have gotten the job.

No, you wouldn’t have gotten the job.

The heat makes every dimension larger, including the hole.

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Heh heh heh

If that happened a disc of metal would get thicker in the middle when heated. It doesn’t.

We had this discussion here about 10 years ago, I think.

Yep, 10 years ago:

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I must have been working that day or at my retirement party. I’ll take your word for it. Looking at some of the posts, there seemed to be some serious discussion. Everyone knows about the ring and the ball though, just threw me talking about a thick plate. Awfully tempted though to click on one of those bathing beauty ads instead though.