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Comment by ygra | Hacker News Reader

Interestingly, the Bosch food processor we have has a plastic coupling between the motor and the meat grinder attachment on purpose, so if anything gets stuck, it's a 5 € plastic part that's broken, instead of a more expensive and less accessible one. So a plastic coupling alone doesn't sound that alarming in general.

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That is only true if the parts are available, often times companies will change the design annually and discontinue the parts making that "easy fix" a time bomb waiting to break and now you have to replace the entire thing

3D printing could resolve some of that, but brands have been known to issue take downs or other legal threats over people sharing models so....

The folks over at Lens Rentals have an excellent blog where they tear down lenses and cameras; they've discussed previously that plastics and metals have strengths and weaknesses, and encouraged people not to simply assume that plastic components in a lens tell you anything about quality or durability.

I think Kitchenaid's have that too, I remember repairing one years ago with my dad.

Yes, they precisely have that. Have repaired three Kitchenaid mixers over the years, from different eras. Even in the higher end machines where it is almost all metal gears and parts, the helical gear box in those too is all plastic parts for easy and cheap replacement, and so that anything getting stuck doesn't burn out a more expensive elctrical motor.

I have an immersion blender that also has plastic gears, and even though the motor is sold as a single unit that is not an FRU, you can take it apart and service it with off-the-shelf gears you can source from eBay.

The two coffee grinders I have, high quality metal burrs, plastic gearing, for the same reason.

My higher quality power tools- track saw, drills, etc, all plastic gearing, metal everywhere else.

It just makes sense when it comes to repairs, though can be frustrating when they strip out.

That said, most consumer crap made today is complete shite.

Most garage door openers too.

Unfortunately, it's an open system, so the grease usually dries out after 5-10 years. Undo the 6 screws and put some marine grease on them every couple years everybody.

I bought and installed a Sommer Evo+ (German made), after Chamberlain, Craftsman products crapped out prematurely. So far, so good (7 years), extremely quiet; slow, but well put together.

Garage door maintenance, every two years, regular as clockwork. In Southern California, with all the dust and the dry desert heat, you have to clean them down and regrease regularly. If you don't, they get real noisy, and then they fail. I've looked at closed system units, but they aren't worth the cost vs the 20 or so minutes of biennial maintenance. I'd rather have $3 of plastic gears strip out that I can reorder through a dozen different supplies than actual damage to my door or the infrastructure that holds the door. Though that has become less of an issue on newer units with excessive force sensors.

Your drills have plastic gears simply as a cost saving measure. Spend a bit more and you get powdered metal gears.

Okay, I'll bite, tell me which drills I should be spending a bit more on?

Not sure. I don't think drill manufacturers advertise these details often because they don't want to confuse consumers.

You can try to watch teardowns, like this DeWalt by Ave: https://www.youtube.com/watch?v=NHCS7JXfuv0

Gears at 16:40

Yeah, okay, you got nothing.

What are you talking about? You claimed the plastic gears were used as a failsafe. That's not true, higher quality equipment uses metal gears. Drills already have fuses and overload detectors built in.

Go watch some teardowns of cheap stuff vs expensive stuff and stop being a jerk.

I'm not your mom. I'm not gonna explain everything AND shop for you.

> the helical gear box in those too is all plastic parts for easy and cheap replacement, and so that anything getting stuck doesn't burn out a more expensive elctrical motor.

I preferred metal "shear pins" for this function ... much easier to find replacements for at the local hardware store.

Now that I agree with. Unfortunately their usage in lower end products, and also the move to lighter weight products with higher torque due to brushless motors, seems to have reduced their usage. Maybe because they are an all-or-nothing failure point. Unless you really abuse the gear box, plastic gears don't tend to strip out all at once, they just get "worn" or "sloppy." That said, I think a lot of products are a race to the bottom in some regards.

They do. I've replaced ours twice in 15 years of ownership (and have 3 more replacements in the junk drawer, since they came 5-for-$10: ASIN B07Y7S33RF).

It's a pretty elegant design. Unfortunately, a lot of people (including my wife, initially) would be prone to concluding that the whole unit was “worn out and needed replacing”.

It depends a lot on where the breakable part is, and whether it can be replaced reasonably. I just did some repairs on our Cuisinart food processor, that highlighted poor design.

The motor is in the base of course, driving a shaft that comes up through the center of the housing. So far, so good. The problem is that this beefy-looking motor is screwed onto three plastic pillars that are just part of the otherwise thin outer housing. Each pillar is essentially an "asterisk" cross-section, probably to minimize material, and it had just snapped off the outer shell. You can buy things like the blades or the plastic bowl, but not random parts from the inside (or, outside).

I managed to get it together with a screw through the housing and a large glob of epoxy putty, but the experience really emphasized that it was pretty much designed to fail.

Its common practice for larger devices as well. E.G. construction equipment will often have an inexpensive rubber coupling between the very expensive 250 HP diesel motor and the hydraulic pump or air compressor that provide useful working fluids to the tools.

Sometimes they can be a right bastard to replace, but its still cheaper and much quicker than replacing a blown hydraulic pump and flushing the system to ensure no filings escaped the filters.

Yes, this is the moral of the story behind the “one boss shay.”

https://www.gutenberg.org/files/45280/45280-h/45280-h.htm

A deacon designed a horse cart where all the parts were designed to last a hundred years. Most cart had a weak spot which meant the cart wore out but never broke down. This thing was built with no weak spots.

So on the hundredth and one year to the day, all of a sudden everything failed at the same time and it collapsed into a cloud of dust.

There are 2 issues:

1. They don't sell this coupler as a part. I could get one from abroad for like $7+postage and wait weeks for it.

2. This plastic crap is glued to the motor shaft. I might deform the shaft while trying to fix it.

> it's a 5 € plastic part that's broken

FWIW you can buy used one for that price

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