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Mr. Fix-It
Feb. 18th, 2008 03:04 pmFor a long time, our shower/tub had a problem: it would drain the water only when you held down the switch. Since our landlord bought the house to flip it and has been renting to us at a loss, she hasn't been able to afford to send a plumber out to fix what the lease didn't require her to—and she suspected she might have to replace the tub in order to fix it.
I finally got tired of it and decided to see if I could figure out what was going on. It turned out to take me less than half an hour to inspect, diagnose, fix, and test. I needed only a flathead screwdriver and a pair of needlenose pliers—and some mechanical know-how.
The switch is a metal knob about an inch long that sticks out from an octagonal plate screwed to the tub below the spigot. I unscrewed the plate and noticed a few things.
First, the knob extended about another two inches behind a D-shaped protrusion at the back of the plate, and was held against the protrusion by the force of a spring sandwiched between two washers. The washer towards the back was held in place by a U-shaped pin. This provided a certain amount of pressure against the D-shaped protrusion so that the knob could point up at a 45-degree angle or down at a 45-degree angle, but the spring would generally force it into one of these two positions.
Second, behind the U-shaped pin was another one going through a hole at the knob's back end and also through two holes on either side, providing a joint at which the knob could lift or lower another pin (and doubtless more pins below that). The weight of the water valve would not ordinarily be enough to affect the position of the knob.
In this case, however, the weight of the drain-and-rods assembly was clearly pulling down with more force than the spring could counter. As a result, even when I had pushed the knob down, lifting up on the assembly to open the drain, the internal weight would let the knob rotate around the D-shaped protrusion and drop back into a closed position.
Well, how do you add force to a stiff spring so that it can resist compression? I did it by stretching the spring out by maybe 1cm, then pinning everything back in place. I'm no mechanical engineer, so I don't know whether the spring will gradually lose its ability to resist compression again, but when I got everything assembled again, it was clear that the knob will now stay in either position without requiring lots of torque to flip it up or down.
And it's also clear to me that the knob-and-pin assembly is designed to be fairly modular: if the spring were to fail entirely, I think one would be able to replace the upper mechanism without touching the lower mechanism.
Yay me! Yay modular design! Yay hacking!
I finally got tired of it and decided to see if I could figure out what was going on. It turned out to take me less than half an hour to inspect, diagnose, fix, and test. I needed only a flathead screwdriver and a pair of needlenose pliers—and some mechanical know-how.
The switch is a metal knob about an inch long that sticks out from an octagonal plate screwed to the tub below the spigot. I unscrewed the plate and noticed a few things.
First, the knob extended about another two inches behind a D-shaped protrusion at the back of the plate, and was held against the protrusion by the force of a spring sandwiched between two washers. The washer towards the back was held in place by a U-shaped pin. This provided a certain amount of pressure against the D-shaped protrusion so that the knob could point up at a 45-degree angle or down at a 45-degree angle, but the spring would generally force it into one of these two positions.
Second, behind the U-shaped pin was another one going through a hole at the knob's back end and also through two holes on either side, providing a joint at which the knob could lift or lower another pin (and doubtless more pins below that). The weight of the water valve would not ordinarily be enough to affect the position of the knob.
In this case, however, the weight of the drain-and-rods assembly was clearly pulling down with more force than the spring could counter. As a result, even when I had pushed the knob down, lifting up on the assembly to open the drain, the internal weight would let the knob rotate around the D-shaped protrusion and drop back into a closed position.
Well, how do you add force to a stiff spring so that it can resist compression? I did it by stretching the spring out by maybe 1cm, then pinning everything back in place. I'm no mechanical engineer, so I don't know whether the spring will gradually lose its ability to resist compression again, but when I got everything assembled again, it was clear that the knob will now stay in either position without requiring lots of torque to flip it up or down.
And it's also clear to me that the knob-and-pin assembly is designed to be fairly modular: if the spring were to fail entirely, I think one would be able to replace the upper mechanism without touching the lower mechanism.
Yay me! Yay modular design! Yay hacking!
