OT: calling MgoEngineers and MgoPhysicsNerds

Submitted by Rodriguesqe on

I recently moved into a new place. Im on the 3rd floor and the stairs are a huge (small) bottleneck that I couldnt get almost any of my furniture through.

I think the cheapest solution somehow is for me to build a crane and hoist it to a rooftop deck. From there it will be easy to get the furniture into my unit.

One of my coworkers happens to be a wiz at DIY and also is an accomplished welder. He can build the crane no problem.  But our plan is to build a cran with a base that we will weigh down (theres no good place to mount the crane). We will attach an electric winch to the crane

My stuff isn't overly heavy, just too big for the bottleneck, probably all under 100 lbs.

My deck is approximately 40ft above ground. Assuming my coworker builds a crane that can handle the load, how much weight will I need to weigh down this crane? Is there a ratio? And does the height matter to the ratio?

Thanks in advance to the MgoUser that knows this stuff off the top of his head.. I'll post an ms paint doodle of the crane to give some idea.

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brad

October 14th, 2016 at 8:56 PM ^

Really, the height is only important so you know he weight of rope you're lifting along with your object.

Forget about the height and worry about everything happening inside your apartment. That is the stuff that will injure you if things go wrong.



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cheef16

October 14th, 2016 at 9:46 PM ^

I don't have any sense of the capacities at play, but is there any concern about your deck's ability to support the weight needed to stabilize the crane, plus the crane, plus you and all your friends, plus the video crew being demanded by the MGoCommunity?

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MeanJoe07

October 14th, 2016 at 8:01 PM ^

first your gonna tinkle in the hallway and do the Hokey Pokey before you guzzle a an orange juoce with full pulp. make sure it's full pulp okay. then you laugh like a hoaniuh ND to the ticket game 7 times. okay? say yes

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stephenrjking

October 14th, 2016 at 8:07 PM ^

This appears to have a high probability for calamity. I echo the request of others for filming.

I'm not sure what steel you're planning to use. Are you positive that your steel and welds will be sturdy enough to hold firm under the loads you're talking about?

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Blue in Denver

October 14th, 2016 at 8:54 PM ^

But you're talking pretty long columns here.  Buckling is not normally something someone in racing is worried about.  It IS something you need to worry about.

I'm 25 years removed from my mechanical engineering days, so hopefully the structural engineer who chimed in above will do so again.

You know those private antenna towers that have 3 main 'pipes' in a triangle, connected to each other every foot or so?  Think in those terms.

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brad

October 14th, 2016 at 9:35 PM ^

Bucking is an issue with steel, but the actual steel pieces should be pretty short, which is good. The rope in tension is the only long element here and that can't buckle. Also the actual steel compression forces are going to really small, so like someone else said, the welds or bolts will be the critical thing most likely.

You do have to find a good way to swivel or pull your shit over the actual roof once you've lifted it up though. Is that figured out in your buddy's crane design?



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Rodriguesqe

October 14th, 2016 at 9:42 PM ^

well, we had plans for the pivot.

He thought the bearing from a BMW might do all the work we need:

Wheel Bearing - Front - GMB

 

but he also has other bearings around the shop we could otherwise use. But that was not considering what Blumanji said about the counterweight needing to pivot with the load. We wouldnt be able to that with this setup. Do you agree that would be mandatory. We just need to pull it in a distance of a few feet. Probably 90 degrees, and we'll be well above minimum counterweight.

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brad

October 14th, 2016 at 11:37 PM ^

If you use this, you'll need a different type of crane than you described. This bearing would work at the top of a tripod and your crane arm would have the counter weight attached directly to it at the opposite end of the lifting end. It's probably more risky because the counterweight would need to be adjusted to work with the weight of your object. If it's not adjusted correctly you could potentially tear your crane arm out of the bearing when you lift something.

Ah! Unless your counterweight is set on a flat rolling furniture dolly and then connected up tight to the back end of the crane arm. A tripod with that bearing at the top, and a very stiff crane arm with that rolling counterweight at its rear would be perfect for you.



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Tacopants

October 14th, 2016 at 8:34 PM ^

If making a simple hoist/pulley is impractical you should get a scissor lift or boom lift.

This is one of those situations where you're going to spend a ton of time and money designing and building (and transporting and assembling and tearing down) when you could have just rented a lift and been done with the entire process.

The next best thing to do is to get someone out who does something like piano moving to give you an estimate on how much it would cost to just have them do it.

 

If you still want to do it yourself I'd probably also check to see what your health insurance does and does not cover...

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MLG2908

October 14th, 2016 at 8:45 PM ^

I agree with those that suggest much can go wrong with your plans.  For example, the base may slide or shift under load even if heavily weighted (what is the coefficient of friction) creating different dynamics and potentially damaging the building and/or your goods.  Are you well insured?

Moving your own stuff is one thing.  Being responsible for moving a future tenant's goods creates potential liabilities that you may need to consider.   

If you want to try this project, do some research to benefit from others experiences.

http://www.instructables.com/id/Boom-Crane-Pulley/

https://www.reddit.com/r/DIY/comments/oqhc0/moving_furniture_into_a_3rd…

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aratman

October 14th, 2016 at 8:48 PM ^

You can lift anything with enough pullys. if there is a roof above the deck screw a heavy eyelet into a beam.  You can either get an electric wench at the Freight or snatch blocks and rope.  They have load levelers to help balance and many many nylon straps. 

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Don

October 14th, 2016 at 9:13 PM ^

OK, now we're getting into legal territory. No beam is going to be right at the outside surface of a roof; it's going to be below the roof decking, which in turn will have sequential layers of some sort of waterproofing material above it. If you start drilling holes through that waterproofing to anchor to a beam, you're now opening up the roof—and everything below it—to water. Water is not your friend once it penetrates the membrane, whatever its construction.

Sure, you can caulk the hell out of the holes once you're done, but if the owners ever found out you'd been drilling through their roof and then water damage occurred, you'd be in an interesting legal situation.

I'd recommend moving out. Find yourself a place with a sane access plan. I suspect your building was built 30-40 years ago when appliances and furniture for students were smaller.

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Njia

October 14th, 2016 at 9:00 PM ^

There is literally no way this would be approved. Someone will call the police, who will unquestionably issue very expensive citations for all manner of violations. I can assure you that the fines alone will run several times the cost of a lift.

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turtleboy

October 14th, 2016 at 9:16 PM ^

The minimum amount of weight needed is more than the weight of the heaviest object you're lifting, minus the weight of the crane itself. If I were you I'd simply brace the base of the hoist against the top of the frame of the door wall, so the entire weight of the building works in your favor.

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micheal honcho

October 14th, 2016 at 9:39 PM ^

2 4"x4"x 10' beams laying flat on the deck 12" apart with 12" 4x4s like ladder steps between them. Bolt this down thru the deck surface & thru another 4x4 spanning deck beams. Pulley & come along or electric wench to lift. Don't forget a trailing line firmly attached to the load for control/manipulation and to swing it up to deck surface once up. You'll have to remove a section of rail on the deck.



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ole luther

October 14th, 2016 at 9:50 PM ^

height absolutely matters. maybe not from an engineers standpoint but  I've been actually doing this shit for over 30 years and someone is going to emergency and someone is going to jail if the strength of the vertical shaft isn't considered.

The higher the vertical shaft, the more outward stress is placed upon on it.  Therefore, the higher, the stronger the vertical must be.

Seen them snap many times due to lack of strength and not being braced properly.

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StraightDave

October 14th, 2016 at 9:54 PM ^

then buy some crap and assemble it inside the house?    How did the previous tenants get thier shit out?

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mbrummer

October 14th, 2016 at 10:44 PM ^

Am I the only one that is disappointed this post  isn't a theoretical physics question.  Deep in theory and nuance?  

I'll quit drinking and go to bed..

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MIdocHI

October 14th, 2016 at 11:02 PM ^

This reminds me of my glass boat tour of the canals of Amsterdam while under the influence of the local substances. The tour guide explained that all the buildings had large hooks at the roof peaks so furniture and appliances could be placed in the upper floor apartments through the windows by using a rope because the doors and stairwells were small and narrow. So, I suggest putting a very large hook at the roof peak and doing what the Dutch do. I am sure that your landlord won't mind.

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