Suggestions on 'dumbwaiter design'

Are you worried that some kids might find it and try it out?

Get a Harbor freight cable hoist and make a suitable basket for it to lift. A hoist with a hook isn't an elevator nor is a cargo basket to be picked up by that hook. Lift the basket above the second floor deck height and pull it in with a hook-pole as you lower it back to the deck.

Sounds like the pawls they have on many auto lifts. Basically an over center cam pawl. When the lift passes them they rotate up and when it clears they drop back. To retract them the lift I have has a simple bar that has pins that engage slots on these pawls. Pull the release cable and raise the lift and they retract.

I've had a cable hoist dumb waiter to raise firewood from the basement to the living room fireplace for 17 years. Work well. inexpensive and easy to constuct. capacity here is 500 lbs.

a step up. I've used a chain hoist to lower apple bins into the packing line for 22 years. capacity here is 1000 lbs. You can easily get an even larger unit.

Karl

If slicing off you arms is all you are worried about, how about putting a hinged door on the box that swings out over the second floor so the box can't go down unless the hinges shear off, then use beefy hinges? or how about having a cam or some sort of linkage on a door to the shaft that locks the box in place when the door is open? Or how about a variation of Elisha Otis' design where the pressure of the lifting mechanism keeps the pawls disengaged? though a slow leak would be like a normal decent and could still trap an arm so maybe that isn't really what you want. While it might seem that a double acting cylinder isn't needed on a dumbwaiter, If you do use a double acting cyl, and lock valves at the cylinder ports (at least for down) it will take a pretty catastrophic failure to be a big problem, you know, you could use a variation on that idea, with a sequencing valve and a small cylinder to disengage the pawl.

Harbor Freight has useable AC powered cable hoists quite cheap and frequently on sale.

They also have a swing arm for the smaller hoist which would be perfect for the barn application.

~$135 + tax / shipping, and whatever small cost for a load basket.

Check out an extension ladder.

On Mon, 19 May 2008 13:29:47 -0500, with neither quill nor qualm, Bill quickly quoth:

These might give you some ideas, Bill.

- Press HERE to arm. (Release to detonate.) -----------

Put the moving part on the track, the dumbwaiter carriage lifts them as it passes, If the dumbwaiter side is c-channel, when they pass the top flange a limit switch fires a lamp and you stop and lower to lock. To lower the dumbwaiter, go up until they fall free, then roll down right over them.

I saw a very interesting dumbwaiter design once that used a hose sitting on the top of the lifting rail, a wheel pair around the track squeezed the hose flat, as water or air was added to the bottom of the hose, it inflated it, forcing the wheel to roll up the rail.

Stuart

You beat me to it. :-) ...lew...

Take a look at the pawls on an extension ladder -- it seems to me that such a design (or a pair of them ripped off of an old ladder) would work just fine.

Having said that, I think I'd take the suggestions to use a cable hoist. Why do something fancy when something simple will do just fine?

Place I used to work at had a metal basket restrained by 4 vertical RHS members. It had PVC or nylon runner wheels on each corner to locate / restrain the basket. Lift provided by electric chain block. Worked well and was passed by OH&S inspectors. it had gates with interlocks at ground level and first floor.

Bill wrote in news:Xns9AA3935F2871Afredbarneybigmailbox@216.196.97.142:

I guess I was too smart for my own good :) I was trying to avoid the official use of the word elevator so I was using the word dumbwaiter in quotes to try to get my point across. There have been a few discussions in the past about home elevators and mostly what came across was the belief that no one but a 'professional' engineer should consider designing one and people were derided for suggesting that they were going to do it.

The 'dumbwaiter' in question will be 3 foot by 3 foot, 7 foot high and have a carrying capacity of 500 pounds. (Nuddge, nuddge, wink, wink, say no more, say no more....) ;)

Most of the problems that people had with the idea of a home made elevator was of using a winch to move the carriage up and down. None of the designs had a good failure mode or means of stopping the carriage from dropping 8 feet or so either with someone in it or the drop happening when someone would be entering the carriage.

Since I'll be using a hydraulic cylinder to do the lifting I'm eliminating the majority of that problem, hydraulics having a 'soft' failure basically just lowering the carriage slowly if there would be a pump failure, control failure or hose failure. What I'd like to do is add an additional layer of safety in that I'd like to make it impossible for the carriage to fall at all when on the upper floor even if the entire bottom of the cylinder would be sheared off (for the life of me I can't figure out how this would happen but....)

I've been thinking about it a bit more and I'm leaning toward something like this.

The carriage comes up past a spring loaded pawl that is pushed out of the way until the carriage gets past, then it snaps down again in a locked position where the carriage cannot drop past but whould rest on the pawl. To get the carriage down the system would have to raise the carriage up an inch or so where to of the carriage would push against a lever that would unlock the pawls and allow them to swing down. Once the pawls are unlocked the carriage could be lowered past them to the ground reseting the locking mechanism for the next lift. With it all mechanical I wont have to worry about relays or solenoids or other complicated systems failing and as long as we inspect the unit a few times a year I wouldn't be worried about wear and tear negating the safety feature.

Now I just have to design it :)

Bill

For what you're doing I'd buy a fork lift mast. Just put elevator car on forks. Bolted on, of course. Get a small electric hydraulic pump to run it.

For a safety from dropping; have you ever seen the catch on a car air bumper lift? The unit won't go down unless you hold the lever down against spring pressure. It's just a catch dog that will grab every inch or so.

Just a couple ideas.

Karl

Why not have the operating switch inside the dumbwaiter mounted on a bolt that locks the carriage to the rail by a spring? Pull the bolt out and the carriage moves, release it and it stops at the next bolthole.

Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/

What, you have a barn with *stairs*? What kind of decadent luxury is that? My barn has (very old, highly worn) 2x4s nailed to the studs, serving as a ladder. When you get to the top, there really isn't much to grab onto for the last step.

I'm planning a similar application to get items up to the upper story of my garage (there's a deck there). I'm going to use a hoist, as others suggested, and want the "carriage" to remain up top normally, so as to fill the hole. I plan on manually inserting pins through the deck's floor joists into matching holes in the lower carriage. It won't be really convenient, but the dumbwaiter will see only occasional use.

My bigger issue is what to use to guide the carriage, so it won't swing or twist during its transit. One guy (whose name actually is Guy) suggested rails & rollers for a garage door, but I found a linear slide on a piece of scrapped equipment that has a rail long enough to work, so that's what I'm contemplating using. It's pretty hefty, though, and we wonder about its appearance. It also weighs a couple hundred pounds or more.

[snip]

Joe

I used to work at a plant that had a hydraulic freight elevator, cylinder was under the car, not telescopic either, went 3 stories straight down. As far as I was told the only safety there was, was an orifice in the bottom of the cylinder, if the line broke the elevator would fall at a normal rate since that was the smallest restrictor in the hydraulic system. BTW it was a 12,000 # elevator.

Thank You, Randy

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Known as a "hydraulic fuse" in the trade.