is it possible to turn this dumb-waiter into an elevator?

Question

We recently acquired a house that has an elevator-like mechanism. The former owners call the thing a "dumb waiter", suggesting that it's not safe for human use. Although it's roomy enough for a human to stand in, and supposedly has a 300lb capacity, I certainly wouldn't ride in it. (Amusingly, one of our new neighbors, friend of the former owners, says he's ridden in it; but, he's a retired jockey :-) ).

I'm wondering if there's any possibility of upgrading the thing so that it is safe for human use. I don't think it'd be possible to install a braking mechanism, like the one on a real elevator. Absent any other ideas, I think the solution would have to be some sort of redundant suspension mechanism.

This is probably a situation where a picture is worth a thousand words, so here's a few. The "shaft" is composed of 6x6 timbers at each corner. The "car" is about 3-feet square and is made of metal; little plastic wheels keep it rolling along the timbers. It's suspended by a small electric motor and a length of 1/4" wire rope. The overall floor-to-floor height is 18 feet.

Answer 1

No, it can't. The design presupposes that it is only going to be used for food. It will not be robust enough or safe enough for people. Unsafe meaning, collapsing and falling down or just people poking their fingers and arms where they will snap.

Also, note that in NZ, it would have to be certified by a lift specialist. I suspect this may be true in many parts of the world.

I recommend that you call some companies that make lifts and see if they can fit a solution in the same spot. The cheaper residential lifts are not that expensive, in NZ anyway.

Answer 2

Forget it, this thing is a complete pile of junk.

But don't take my word on it. Ask your insurance company, because I guarantee this thing is news to them.

To qualify as a human-rated elevator it needs to be designed properly from the ground up. And in commercial practicality, that means using an off-the-shelf pre-engineered design, because that is far cheaper than a civil engineer designing an elevator from scratch. It would be impossible to build an elevator shaft out of 6x6 and have it be safety rated. Using a winch as a lifting mechanism (and braking mechanism!!!) is also a non-starter

This was a foolish hack design done by the previous homeowner behind the back of his insurance company. They represented it as a dumbwaiter for cargo only, even though it's obviously built for humans, for liability reasons.

There will be no way to adapt this into a legal elevator. For your own liability's sake you should either demolish the whole thing, or redesign the car to be 2 feet tall to preclude use by humans, so it truly is a dumbwaiter.

I don't gather that you want a dumbwaiter, but if you did, I would redesign it to have 2 cars moving opposite, so one car is low when the other is high, and they counterweight each other. I'd solve the "getting hung up and dropping" problem by having a lower cable also connecting the cars, so one moving up pulls the other down. The drive mechanism can now be on the bottom.

Answer 3

There's arguably no way to make this safe

There's two bits for this: making it safe enough for an insurance company, which you can't do, because you aren't a licenced engineer, designing from a list of pre tested and approved systems.

But there's also making it safe from your perspective - i.e, turning this into less of a deathtrap. I'd argue this can't be done without a rebuild, either.

My big worry is that the elevator car sticks and slips somewhere. It gets caught on the platform, the cable spools a little, and it drops a little way. The winch that is fine under just a standard load suddenly has the job of bringing an elevator car to a near instantaneous stop.

This is generally something you want to avoid doing in physics. It exposes every bit of the system to a multiple of the regular force on it. None of this system looks designed to handle multiple times the regular weight of the elevator + passenger.

The best case scenario is that the lift cable snaps and the passenger and elevator falls

The worst case is that a chunk of the lift structure collapses too, crushing the passenger under the wreckage, and possibly bringing with it some deck supports.

Winches with steel cables are dangerous enough, even without a deadly lift on them.

That's before, even, you get to backup mechanisms, which are another big design ask.

Then there's interlocks. Nothing, currently, stops someone climbing in underneath it while it is descending. There's a door stopping you going in while the elevator isn't there, but that can just be opened, leaving you to plummet down a lift shaft.

Answer 4

When I built my house, I put an elevator in between the garage and the attic to haul stuff (mostly Christmas decorations) up and down so my wife and I didn't have to drag them up and down stairs. It is a great addition. It is not unlike your elevator, in that it is designed to lift things (not people) and can fail in a number of ways - all of which should not be fatal to those loading and unloading it. Like you, I would not recommend anyone ride in it. Your current elevator is a long way from being safe enough for public transportation (for all the reasons folks have listed) but I don't know what kind of family situation you may be facing that might require you to trade off your family's safety versus getting affordable, stair-free access to an upper floor. I would advise (like the others) that you avoid using it at all for human transportation - there are just so many things that could go wrong and it would take so much to fix all of them. But I also don't want you leaving this forum without any useful advice and doing your best to fix it up because it is worth the risk to your family for reasons we may not understand. So my advice is think about what could go wrong that would be a major issue to you and address those. Lawsuits from non-family members and pinched fingers from doors are probably not what you should focus on. I see a real need for a fully redundant lift system at a minimum and certainly testing that it can actually carry the load prescribed under stressful conditions (including failure of one of the lift systems). And probably retesting it yearly to ensure weather didn't degrade any components. I am also really curious about what would happen if it got stuck between floors with someone on it - either due to a power loss or the rails getting jammed. How would you get them down? And finally, could you live with yourself if you or another family member was critically injured? So again, my advice is don't do it, but if you feel you need to press ahead anyway, please think through the failures and the consequences as best as you can to meet your particular family's needs. And to keep non-family members safe, I would keep the carrier at ground level and flip the circuit breaker so no one can activate it in your absence.

Answer 5

The aspect of elevators that permitted widespread use is the braking mechanism. Trusting one's health to a repurposed winch without a backup seems risky, at best.

If you're determined to make use of this device for moving humans, a secondary support system should be created. On the expensive side of things, I envision a series of nested cylinders containing hydraulic fluid. As the chamber descends, the fluid is pushed into a reservoir through a flow regulating valve. This would mean that a cable break would turn the free falling chamber into a carefully controlled descent.

Alternatively, a cable of similar strength as the winch wrapped around a capstan which is in turn attached to an unsightly large air-paddle would accomplish the same thing at a lower cost. Provision would have to be made to reel in the cable as the chamber ascends as well as allowing it to spool out on the descent. The air-paddle would only come into play if the primary lift cable breaks.

Based on the comments, I could have phrased the device in a different manner. There are exercise machines that drive what amounts to a large fan. If one pictures a paddle driven riverboat, but removes it from the water, it will reach a limiting speed based on friction with the air, as well as moving masses of air.

The comments also reference magnetic control devices commonly used in exercise machines.

A search for controlled descent devices does not return any references to air-paddle control. The idea appeared in a movie from the last century in which jewel thieves jumped from a building attached to a cable on a capstan with an air-paddle descent control. The cable snagged leaving one of the suspects suspended until authorities began winching him up. My suggestion may be as impractical as the idea of converting this to a human-rated lift.

Other aspects mentioned in the comments are valid and should not be overlooked.

'tis a bit of an unusual objective, but I have been considered a risk taker.