How would you affix a hoist to this setup?

Hello,

My health quit on me and now I can't easily get out of bed. But I need a workspace to build models and robots. My solution is two tables that hang over my bed and drop down on four hoist cables. I plan on having one hoist for each table (not shown.)

The tables will be 4' w x 4' L x 4" high. Each will weigh about 100 pounds. See attached picture for what I'm going for in the extended and retracted configurations. Not shown in the picture but I plan to measure the height of my lower legs while in bed and use 3/8" steel cable as a safety mechanism to ensure that, if the hoist fails, the tables can't fall far enough to crush my feet.

The bed frame consists of 4x4 lumber with 2x4 crossbracing and various other bracing hardware. The bed supports are 2x4s spaced every six inches. I think I did the math at one point and at least one elephant can stand on my bed frame without it breaking if the load is spread out. Hanging a few hundred pounds from it isn't a problem.

For the lift cable, I'm not sure if it's better to have the hoist mounted overhead and pull up, which will mess up my overhead clearance and make the tables lower than I'd like, or run the cables down and have the hoist pull down to raise the tables rather than pulling (up if that's clear.)

If you often couldn't get out of bed and still wanted to work on your projects how would you solve this problem? Any advice welcome and thank you for taking the time to read this.

I minister to the needs of two bed-bound people round the clock. Apparatus that needs to be brought to the person is put on over-bed tables.*

It would simplify the making of the bed frame, I think, and not leave you feeling so boxed in or at risk of being crushed if you used a height-adjustable over-bed table that straddles both sides of the bed. It could be wheeled for convenience.

Will you have someone regularly in attendance who can bring your table to you and take it away again when you’ve finished your work? Or will there not often be anyone there but you, hence the overhead tables on cables idea?

*For the uninitiated, these are typically wheeled and the legs roll/slide under the bed. 

Edited By Bill Phinn on 12/08/2023 01:58:59

@Bill Phinn, that is very kind of you to take care of others. And thank you for the reply.

I should have been more clear. The bed frame already exists. That's what the bed I'm tying this while lying on now looks like. Exactly like that in fact. I wanted something that I could turn into a mount for anything if the need arose. Tables aren't there at the moment but, aside from that detail, that's my bed.

That is a good suggestion. I don't have anyone helping me. If I had the room I would use height adjusted tables as you suggested. I'd affix them to a little flat RC robot trolley and have them bring themselves to me when I wasn't up to retrieving them. Unfortunately I just don't have the room. This house is over a century old and not well thought out. The rooms are pretty small. My room is about 100 square feet and the bed takes up over half of that. The doors are below code requirements in width and there wouldn't be a way to move a single table next to my bed, let alone enough of them to get me the space I need.

In my previous place I had a table mounted to a pipe that swung over my bed when I needed it and back when I didn't, but there just isn't the room for that here.

While I don't completely trust a hoist, I do trust the four 3/8" steel cables (2800 pound working limit each) the length needed to stop the tables about a foot off the bed and reinforced on the backside of the table with a 6" x6" 1/4" steel plate. I wasn't sure how to convey that in CAD so I left it out, but it's part of the plan. The usual rule for max dynamic loading in forestry work (and I would assume elsewhere) is 10x the actual load. Actual load is 200 pounds. That gives a max dynamic load of 200 x 10 = 2000 pounds across four cables collectively rated for 11,200 pounds. I'm assuming that 200 pounds of table can accelerate to full speed in less than 6 feet, which they can't, but I really like my legs to be leg shaped so my math is cautious.

If I could think of another way to do this, or felt it wasn't safe between the hoists and safety cables, I wouldn't do it. As it is this is the best I was able to come up with.

Good morning, Eric

For now … May I just admire your initiative and determination

… this is self-help at a very impressive level and I am sure it will inspire the collective brainpower of this forum.

MichaelG.

The slide in tables impressed me. They are made of hollow tubing and have a tabletop

Don't want it there... so shove it away

If you're stuck for space then things get complicated, you need an extra safe system because exterior medical folk will go postal at you hanging 100lb plus above your bed

A car hoist system at the very end on the bedposts with a revolving 24mm threaded bar and a wire counterweight system at the corners closest to your head

Edited By Ady1 on 12/08/2023 10:44:19

Gosh, my sympathy for your predicament.

I don't understand the two tables, To bring the top one down, you would need to clear everything off the bottom one wouldn't you? And four cable supports for each of two tables 'nested' together is going to be a bit tricky to engineer and keep them level etc.

Could you have each table mounted on heavy duty drawer runners to slide out of the way beyond the foot of your bed, and have a long stick to grab either one and pull it towards you?

Somebody must have come up with something on the netty

Spend a day or two google searching through pictures for ideas

Sliding system gives you more tables, like a BISLEY cabinet, also saves time switching tables, time gets important when its running out or you tire easily

Edited By Ady1 on 12/08/2023 11:09:30

You have answered my first question Eric - how much room is available ? Now I know - not much ! Several thoughts. 3/8" cable is not very flexible, so would need large pulleys, it is WAY to heavy for the application. Properly ferruled cables of 3/16" would give a considerable safety factor on your 100Lb tables. Operating the cables via a hydraulic cylinder above or below the bed would give stable operation of the rise and fall - a winch and drum may cause problems of cable lay on the drums. Solenoid operated safety latches and hose failure valves would cover some aspects of safety. Think car hoist as seen in most garages.  Just some thoughts. Noel.

Edited By noel shelley on 12/08/2023 11:14:09

@ Michael Gilligan - Thank you, I appreciate the compliment and encouragement.

Lots of ideas I'd not considered, really glad I asked. Whatever the end result is, it will be much safer than what I'd have come up with on my own.

@Ady1, those tables are a neat concept, but yes, space is a major issue.

Thank you very much for the advice and for taking the time to make a drawing. I approve of the idea of a safe system but I'll mention that I'm in the US. Most medical folks here don't care much about their patients. Not really their fault, it's what happens when the people who make a lot of money from medical care (the AMA) get to set the number of new doctors (also the AMA.) Leading to such absurd statements as "4 hours sleeping is 4 hours not seeing patients." Severe burn out and extreme apathy are the result. I envy the legends I hear of the NHS and a country where ~71% of the population doesn't distrust their doctor.

If I wasn't poor I"d go the 24mm drive route, it's a good idea and thank you for the suggestion. What makes this a challenge to do in a safe functional way is that I'm limited in both space and money. Counterweights I absolutely can do though, very good idea, thank you for that suggestion as well. I saved the weights from my old weight machine, all 220 pounds of them. The easiest way to make this safe may be to always have counter weights that exceed the weight of the table and pull it down instead of up, then anchor it while in use. Worst that can happen then is me getting whacked in the face if I forget to anchor it and the hoist slips while I'm leaning over a table.

Though I can't afford threaded rods, I'm wondering if I could do something with the old elevator design, not sure what the mechanism was called but it was a one way system that would engage if the car started to fall. I could do that on my CNC by cutting teeth into a 4x4 and then screwing that to the existing uprights on both sides, just need to find that mechanism and see if it actually would work here.

I actually spent about a week trying to find designs for this. I may well be using the wrong keywords or not thinking widely enough but I couldn't find any examples of someone doing this. At a basic level I know its possible because I can use steel cable and hang it where I want it and it won't fall, but making it tidy and retractable is another matter. If I had the room I'd use drawer sliders like John Doe 2 and you suggested, but the clearance off the end of the bed isn't much due to how small the room is. Actually, I think this is an elevator. Only just realized that. I believe I need to study elevator mechanisms and dumb waiters.

@John Doe 2 Thanks for the reply and sympathy, I appreciate it. I'll probably have 12" clearance between the two tables. Most of what I work with is pretty low profile. I was actually planning to offset the tables such that only the upper right rope overlapped and then run a guide through the bottom of the top table. Which would likely make balancing every more difficult. Unfortunately not enough room for sliding shelves but that is a very good suggestion and likely what I would do if I had the space for it.

@noel shelley - Thanks for the input and advice. I was using working force when I should be using breaking force. 3/8 cable has an absurd breaking force. I think I have some 3/16th aircraft cable and you're right, that would be a lot easier to work with and retract with the tables than 3/8 would be. Hadn't even considered hydraulics. I've actually got there two absolutely huge cylinders in my back yard. Don't know if the seals are still good but they're five foot high and weigh about 150# each. I think they came off a loader or other piece of heavy equipment. No hoses, pump or hydraulic fluid on hand but I'll see what those might cost. I think I also have some smaller cylinders as I suspect those big ones are absurd overkill for this.

Thanks to everyone for all the ideas and advice, I'll see what I have in terms of parts and then redo my drawings to try to apply your ideas in a way that will work with what I've got and the room I have.

I would focus on a sliding tables Bisley type system

It could be quite useful for electronics work

Edited By Ady1 on 12/08/2023 13:26:40

sliding tool rack

I do like the design of those tool boxes. The problem I have is that there's not enough space between the wall and the bed for the sliding tables to close without cutting off my ability to walk on that side of the room. I'd have to make the tables very narrow but then my equipment wouldn't fit on them. I may have a work around but I'll need to draw it and then post it here for further input (if people remain open to giving me advice and critique.)

I'm thinking of adding two rails to the bottom side of my bed frame and making a counter weighted lift sort of thing. Then building a 2 or 3 drawer/table cabinet like I think you're suggesting and having that run up and down on the rails. That will deal with balancing issues due to both the rails and there only being one cable in the center. It would also get the tables out of my way when I'm not using them. And let me just copy the safety mechanisms used in lifts, like the original Otis one demonstrated here: https://www.youtube.com/watch?v=sSjJjKcoNRk. Plus, if I'm using posts to guide it up and down then I can put in an emergency stop bar as another safety mechanism, which I couldn't do with floating tables.

I'll post an updated drawing when I have one. Thanks again for all the help and advice.

Edited By Eric Olson on 13/08/2023 02:00:57

This is a familiar situation, there are any number of industrial cranes and systems that lift a large item from four corners.

That said which layout is best for this application?

Posts and rails are OK, but they introduce some dreadful tolerancing problems, so don't have four, keep with one or two.

Four cables, ropes will do fine, leading over sheaves to a common drum (winding cylinder), will give a good raising mechanism. A turnbuckle tensioner in each corner will set it level.

I would definitely motorise it with an economical gear motor from ebay, nice and slow. Who wants to work hard?

@Roger Best - Thank you. Though you didn't say this, what I think I'm hearing is that I could have both an elevated shelf system and a crane system if I was sufficiently clever about laying it all out. Or I could design for both, install one and then add the other as energy permits. The ultimate goal being to have the same square footage of table on my bed as I have in the workshop.

That's a good plan. I'll start looking for gear motors. I had a scooter motor I was going to sand cast gearing for, but if I can find a gear motor that will do the job that'll be much easier and probably more reliable.

Thank you very much for all the suggestions, I'll update my slowly progressing drawing in Solid Works accordingly.

Hi

Something to consider is a manual method of operating the tables should a power failure occur.

In The UK there is a voluntary engineering group called Resmag **LINK**

I wonder if a similar organisation exists in the US, If you don't mind me asking what state do you live in? I can think of a few UTuber's that might take this project on.

Lets get this project on the way ASAP.

@John McNamara - That is a good point thank you very much for mentioning it. I'm planning to have a battery system someday but that's likely a bit far off. I'll add a way to lock out and detach the cable system so I can put a manual ratchet system in if I need to.

That's a good resource, I joined and will try to attend their monthly online meetings. There is an American equivalent, it's RESNA, but it's very... American. Even though they're a non-profit, to join they want disabled people to pay them $90 USD a year. I don't have $90 a year and I'm better off than a lot of disabled folks. I sent them an email pointing out that charging the disabled to be affiliated with them in this context is a bit like a student charging a university professor to listen to their lectures. They haven't replied. Charities in the US are often for profit organizations that simply came up with an excuse to be tax exempt. They don't care about the populations they claim to serve. Even so, a charity billing their intended beneficiaries is a new one for me.

I'm in Washington. It's a good suggestion but I don't have one of those photogenic disabilities. My issues are related to the heart, nervous and respiratory systems. I look normal except that I'm on oxygen at the moment. If people had x-ray vision I wouldn't look normal, but they don't so I feel a bit ashamed asking for more direct help.

Once I do the doctor ordered stuff I usually have about an hour of energy a day. I do wish I could move faster, it's quite frustrating knowing what I need to do but being too poorly to do it. I'll get this done once I have the plans and this board has weighed in on them. After that I should move faster with future projects because I can just wake up and start work rather than spending hours to try to get up and move to where my tools are. .

This is taking longer than I thought it would to design. I'm on my fourth redesign now. Compared to actually building this stuff CAD saves so much time. If I had a higher ceiling this would be a much easier thing to do. Or walls that were further back from my bed.

Thank you very much for the advice, resources and encouragement.

Edited By Eric Olson on 21/08/2023 09:41:34

Edited By Eric Olson on 21/08/2023 10:29:22