3 ms·

Oooh yes, don't get me started on inaccessible little plastic sacrificial parts. Yes, having one part be sacrificial to protect the others is good engineering,

Oooh yes, don't get me started on inaccessible little plastic sacrificial parts. Yes, having one part be sacrificial to protect the others is good engineering, but only if it's also easily replaced and inexpensive. If you can't get replacements or they're 3 hours of disassembly away, that's just planned obsolesce in a dress. And the number of times I've broken a little plastic tab! How much can it cost to put a extra 0.5mm of plastic in the mould just there? What fraction of a penny was saved and now requires a whole new part, comprising probably at least thousands of times more material plus shipping energy?

ethbr0 5y ago
Re: sacrificial parts, I recently had to rebuild a two-car wood (read: heavy) torsion spring garage door system. The cleverest part was the plastic coupler [0] between the door-connected shaft and motor. When the system originally locked up, the coupler broke. Consequently after restoring the system, I needed a $9 piece of plastic, rather than a $xxx new motor. Made me sad that more modern things aren't designed with such value-protective degradation modes. [0] https://www.amazon.com/LiftMaster-Coupler-Chamberlain-Craftsman-Garage/dp/B007VP7A5A https://www.amazon.com/LiftMaster-Coupler-Chamberlain-Crafts...
- a_mechanic 5y ago
  FYI motor couplings are not typically designed to fail as a method of protecting the motor. Overload protection is usually handled electrically, with fuses/circuit breaker which will remove power when too much load is applied to the motor (stuck door) or via controller board and load sensing. https://www.prairielectric.com/blog/how-do-circuit-breakers-protect-appliances/ https://www.prairielectric.com/blog/how-do-circuit-breakers-...
xyzzy_plugh 5y ago
There is no cost savings associated with the size of tabs, for example. It's an assembly thing. Usually you want the easiest to assemble as labor and QA is expensive. Ease of disassembly has by comparison very little upfront value.
bombcar 5y ago
Even better - just ship with a few extra parts slipped in. I’ve actually seen this - extra screws and clips right inside the cover just like extra buttons sewed into the corner of a shirt.
jacquesm 5y ago
A lot of those plastic tabs work just fine when something is just made because the plasticizer is still present abundantly, then later, when it has evaporated the parts become brittle. https://en.wikipedia.org/wiki/Plasticizer https://en.wikipedia.org/wiki/Plasticizer

ethbr0 5y ago

Re: sacrificial parts, I recently had to rebuild a two-car wood (read: heavy) torsion spring garage door system. The cleverest part was the plastic coupler [0] between the door-connected shaft and motor. When the system originally locked up, the coupler broke. Consequently after restoring the system, I needed a $9 piece of plastic, rather than a $xxx new motor. Made me sad that more modern things aren't designed with such value-protective degradation modes. [0] https://www.amazon.com/LiftMaster-Coupler-Chamberlain-Craftsman-Garage/dp/B007VP7A5A https://www.amazon.com/LiftMaster-Coupler-Chamberlain-Crafts...

a_mechanic 5y ago
FYI motor couplings are not typically designed to fail as a method of protecting the motor. Overload protection is usually handled electrically, with fuses/circuit breaker which will remove power when too much load is applied to the motor (stuck door) or via controller board and load sensing. https://www.prairielectric.com/blog/how-do-circuit-breakers-protect-appliances/ https://www.prairielectric.com/blog/how-do-circuit-breakers-...

xyzzy_plugh 5y ago

There is no cost savings associated with the size of tabs, for example. It's an assembly thing. Usually you want the easiest to assemble as labor and QA is expensive. Ease of disassembly has by comparison very little upfront value.

bombcar 5y ago

Even better - just ship with a few extra parts slipped in. I’ve actually seen this - extra screws and clips right inside the cover just like extra buttons sewed into the corner of a shirt.

jacquesm 5y ago

A lot of those plastic tabs work just fine when something is just made because the plasticizer is still present abundantly, then later, when it has evaporated the parts become brittle. https://en.wikipedia.org/wiki/Plasticizer https://en.wikipedia.org/wiki/Plasticizer