they didn't always work

[keannu]

What do "they" and "work" each mean here? Does "they" mean "this or that invention" and "work" mean "function" or "be effective"?

pp182)Never will I forget my uncle John who was always inventing things. In fact, he never let a day go by without working on this or that invention. The problem was they didn't always work. Once, he worked hard for eight years to build a machine that would fill the cat's dish when it was empty. The finished machine which he thought was very useful was anything but useful. It was seven feet high!

[5jj]

Yes

[mohammad56]

What do u mean?

[Chicken Sandwich]

What do u you mean?

What do you mean?

[Rover_KE]

What do you mean?

Keannu asked 'Does "they" mean "this or that invention" and "work" mean "function" or "be effective"?'

5jj replied 'Yes', because that is what it means.

Rover

[keannu]

Is "work" more strictly "function in machine/device" or "have results/be effective"? I mean if the writer intended to say "the machines he invented didn't always function(after turning it on, the arms moved or something) or "they didn't always bring any result he expected in general meaning".
"work" is hard to perceive in an exact concept in this case, so both concepts might have no difference.

[Chicken Sandwich]

Is "work" more strictly "function in machine/device" or "have results/be effective"?

I think you are, once again, being too analytical. I understand 'work' to mean this:

6 machine/equipment a) [ intransitive ] if a machine or piece of equipment works, it does what it is supposed to do :

work - Definition from Longman English Dictionary Online

[keannu]

It's because my workbook with the example gave me such a definition of "be effective", which confused me. I don't know who to blame, it's all my fault!

[SoothingDave]

If something functions but is not effective, then it does not work. Native speakers are not going to make some distinction here with the word "work." If I build a flying machine that does not "work," it may mean that the wings flap just like I designed it, but it is incapable of flight. Or it may mean that it exploded when I tried to start he engine. Either way, it did not "work."