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Comment by yetihehe | Hacker News Reader

> Metal, vs plastic gears.

Sintered metal gears, last only a little longer than plastic and then fail catastrophically destroying half of the device so that you can't repair it. But at least they are much cheaper than proper machined gears.

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My KitchenAid mixer ate a gear many years ago. They would lead you to believe they are a high quality brand, no?

After disassembly, it turned out to be perhaps the only plastic gear in the thing. It occurred to me that it was perhaps designed to fail rather than the mixer continuing to break the bones of the person who got their hand caught in the paddle.

So, I throw the engineer a bone for that one. I was bummed though to have to order a replacement gear from some obscure place in Florida for like $75 or whatever.

Yeah, sometimes there are plastic gears designed in specifically for this, in blenders and kitchen appliances, some lathes even have a set of several copies of one plastic safety gear. But sintered metal gears in planetary gearbox of a cordless screwdriver which fails faster than it's battery (Einhell) - not acceptable.

The real crime is that there are only like 5 appliance parts companies that stock parts and they each seem to look at the other companies for what to stock. Meaning, if someone else has it they won’t. But what ever they do stock ends up selling for 500% or more of the wholesale price.

I had the same gear fail. It's called a worm gear and is, indeed, intended to fail before damaging the other gears. They're much cheaper if you buy a non-oem part. I bought one from amazon for ~10 USD.

Yeah, this was a time when Amazon was in its infancy. :-(

A worm gear! It is indeed designed to take the fall so the entire machine doesn't shred itself.

I bought an official replacement from KitchenAid for $12 including shipping.

> It occurred to me that it was perhaps designed to fail rather than the mixer continuing to break the bones of the person who got their hand caught in the paddle.

This is a good call out of potential other reasons an engineer team might make something cheaper & easier to break. It would be awesome to read a summary of the trade-offs the teams discuss in their process.

For those who want to see a teardown, AvE has one on his channel here; https://www.youtube.com/watch?v=0qKp-0h9P18

Interesting — it is the "Professional" version and appears to have different internals than my consumer-grade one.

My Electrolux Assistent N8, from 1978, also has a worm drive. Not plastic though, instead it has an electromechanical stall detector that shuts down the motor if it stalls. No need for sacrificial parts!

Capitalism is successfully optimizing for what I as a consumer can detect. I am not capable of simply looking at a device and knowing whether the metal is the quality metal it needs to be, or if it is merely some cheap metal that will bend if I breath on it too hard.

($YOU may be. I'm not.)

Except that nowadays I tend to just guess the latter and I'm statistically correct anyhow.

Superman has a quote about living in a world of cardboard, where he must control his every move lest he rip through everything. I'm beginning to feel that way myself with these consumer products. If you take them even 5% out of spec expect them to catastrophically fail. They'll catastrophically fail even if you use them entirely within spec. I'd happily pay a bit extra for something that wouldn't but there's no way for the manufacturer to successfully convey to me that this is such a thing even if they wanted to. The metaphorical water is so metaphorically muddied that it's just dry dust now anyhow, with fake 5 star reviews and decades of refinement on marketing messages about how this vegetable peeler peels vegetables so well that it will even enhance your marriage prospects.

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