# What strength of beam do I need for a crane ?



## Martin (May 6, 2008)

Here's photos of my makeshift crane to lift boats into the attic where they rest during winter. Last time I used an aluminium ladder with an improvised crap and a pulley to double my force.














I felt pretty unsecure with above setup, as the aluminium ladder bent quite a lot under the load, the crab didn't slide nicely over the ladder and the pulley was almost too hard for me to pull. I decided I want a redesign:
A T-type aluminium beam, an electric hinge, a crab that runs on the T with wheels.
The total length of the beam is 5.8m (228 inch), 3.3m (130 inch) inside the attic, 2.5m (98 inch) outside. The load of 30kg max is suspended at the outside end, the beam is held 2.50m (98 inch) from that load end and at the inside end. So it's 2.50m (98 inch) of beam protruding without support and 30kg of load pulling down the end. Wait - the load is not static it's being pulled up slowly, so there needs to be some margin, I assume.
The load travels 7.5m vertically.

Now I would like to know what strength of beam I need for this. Obviously, I don't want it heavier and more expensive than needed, but I also don't want that it cracks.

I've asked a mechanical designer and the shop selling the aluminium, but they were not sure.
Any help greatly appreciated.


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## dom (May 6, 2008)

Looks scary Martin 
During my stay at hospital i noticed they used enclosed track type lifting apparatus -may be worth a look as well.

http://www.spanco.com/pages/wsalutrack.php

Cheers
Dom


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## KC2IXE (May 6, 2008)

You REALLY want to talk to what would be called in the states " a Material Handling company" - depending on rated load etc, they will design it (and maybe install it)

You are PROBABLY looking at a piece of 6" aluminum I beam, the Crab (called a Trolley here in the USA) and the hoist. Your HUGE problem is there is noting to pull the trolly araw from the building

Now, the BEST bet - and probably cheapest - is if you are allowed to mount something on the outside of the building - they would use what is called a rotating Jib - let see if I can do some ASCII art


|
|----------------
| / H
| /
| /
| /
| /
| /
| /
| /
| /
|/

The line at the left is the mount to the building wall - it's NEXT to the window, and pivots to fold flat
The diagonal is a brace - the horizontal is the beam holding the Hoist (H) - and as there is only a short distance betwee the brace and the hoist, everything is smaller and lighter

Please do not consider this professional advise. I worked fro a crane company installing these systems, but I'm NOT a mechanical engineer. I would not even design a system for my OWN use, never mind someone elses - too many factors - point loads, shock loads etc
edit:
Ascii cart didn't come out too well in the viewer

Here is another way using a top brace

http://www.low-cost-cranes.com/jib-cranes-311.html

http://www.spanco.com/pages/jibwm300.php

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200325507_200325507


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## gadget_lover (May 6, 2008)

The Machinery's Handbook has the formulas for how much weight a beam can support. I don't have time to look it up this morning, but mybe some of our other folks can help.

Daniel


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## Martin (May 6, 2008)

Dom, so you're back on your feet ?
I do have the enclosed track rails here, this is what started the idea. They were used for a heavy double-sliding door. But they need reinforcement, at 2.5m x 30kg. Brings me back to the original question...

KC2IXE, a roating jib, I know what you mean.
However, I want to have the beam extend 3.3m to the inside, so I can pull the hulls straight to their parking position on this 2.5 + 3.3 = 5.8 m rail.
So I need the full length beam plus the rotating jib for additional support.
I'd really like to know what size of beam I need for 2.5 m x 30 kg = 750 Nm, to go WITHOUT this additional support. I suspect it's not that very big.

Pushing out the trolley is no problem with a little wheel at the end of the beam. This lets me pull the trolley outwards with a rope.


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## mahoney (May 6, 2008)

I don't have time to look at the math now, and it's likely that the materials available in the US are not quite the same as are available to you, so I'll start with an obvious question or two.

Are you sure the house can take the load? Sure, the ladder outfit worked and the roof is still standing, but a beam and trolley will be heavier. There is considerable downward force where the beam is supported as it leaves the house and upward force inside on the roof. Have you consulted with a structural engineer?


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## 9x23 (May 6, 2008)

I believe that KC2IXE is trying to describe a davit arm, and you can see examples at www.tractelswingstage.com. These are used on many buildings for window washing, and in my experience they are firmly attached to the building structure. 

Please note that there is much more to installing a properly designed crane for your described use. Just sizing the beam is only part of the formula, as you will need to make sure the it is attached properly (engineered) to the building structure. Like everyone else, I recommend that you consult a company that makes/builds/installs these system as "turnkey" to ensure that you will be able to safely and confidently operate this without fear of hazards. Good luck!

9x23


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## FredM (May 7, 2008)

I would dump the aluminum Idea and pick up some 8 inch galvanized steel C channel beams. You would only need 2 and since they could be a light gauge and still be plenty strong. they also would be cheap and light.


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## gadget_lover (May 7, 2008)

I just looked up the fomula for determining the beam size.... Page 260 of Macinery's Handbook has quite a section on the subject.

Unfortunately, It's all greek to me.

Sorry to be of so little help. Maybe someone else can look at it?


Daniel


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## Martin (May 7, 2008)

The wooden beam that makes the top of the roof rests on bricks and mortar, that wall having a strength of 13 inch. The force is straight down and I'm pretty confident that the bricks don't crumble. Compared to other houses I have seen, this is overdesigned. And when I used my ladder, there was no creaking of the wood at all, it was rock-solid. So I don't worry attaching my beam that pulls downwards.

My intention is to remove the crane and close the window when not needed, as I will use it only twice per year. This is why I rather not want to heavily overdesign it.
The aluminium ladder that I have used is 3" deep and it didn't break, so I feel the 6" that KC2IXE suggested are not unreasonable. Eventually, 750 Nm is not such a lot but I really lack the confidence not knowing how to calculate this properly.


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## precisionworks (May 7, 2008)

That is one of the most scary rigs I've ever seen:whoopin:

You really want to contact a mechanical engineer on this one, as you need a no-fail calculation.


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## Martin (May 7, 2008)

precisionworks said:


> That is one of the most scary rigs I've ever seen:whoopin:
> 
> You really want to contact a mechanical engineer on this one, as you need a no-fail calculation.


Maybe scary but I'm not afraid. It's not even 10m..

Relax. A friend of mine offered to run a mechanical simulation, I just need to define the shape of the cross section and the material. He can then scale it to the strength I need. This is a way forward.

I also learned what's the German equivalent to the "Machinery's Handbook". It's Maschinenelemente by Roloff/Matek and Taschenbuch fuer den Maschinenbau by Dubbel.


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## precisionworks (May 7, 2008)

> I'm not afraid.


I wouldn't be afraid either, unless walking underneath while you were hoisting.


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## mahoney (May 7, 2008)

Trolleys are typically designed for I-beams. You can also use them on back-to-back C-channels, and that would be a little lighter to mount/remove as you could do it one side at a time.

Engineering advice gotten over the internet from someone is worth less than what you are paying for it, and long distance engineering is only slightly more useless, but for an idea of some of the considerations involved...

If we look at the intended loads, you have the 30Kg for the kayak. You are moving the kayak, and we have to allow for accelerating force, we'll assume you are going to buy a SLOW (say less than 1m/5 sec) winch so we'll only multiply by 1.5. This leaves NO safety factor and rigging can involve a lot of unpredictable shock loads. For example, your kayak could swing and hang up on the overhang above the door and then slip free. Depending on how far it falls, enormous force can be applied to your beam. If someone watches the kayak go up from below, the minimum safety factor should be 8, if the yard is clear, you could potentially get away with a factor of 4, with the understanding that the rig could break if you are careless or something goes very wrong.

Just something to consider here, aluminium is much lighter than steel, but performs poorly when shock loaded, just the type of load you can get when rigging goes bad.

So assuming a clear yard and no neighbors in the path of falling beams or kayaks, 30 times 1.5 times 4 is 180 Kg. Your beam, anchorages (beam mounts), winch and trolley and any other bit of hardware in the load path (shackles, spansets, ...) have to be sized to take at least this much weight plus... Your winch and trolley weigh something as well, so let's allow 30 Kg for them (and the rope you are using to pull them in and out with, the pulley at the end of the beam, the extension cord...), and we need to consider the weight of the beam as well so lets allow 30Kg/m (assuming aluminium). I'm also assuming the winch is on the trolley, and not in the attic with the cable going over a pulley on the trolley. That produces compressive load in the beam and the math becomes much more complicated.

So, some fairly theoretical math done, the downward force on the mount where the beam exits the building would be 522 Kg. Upward force inside the building at the other end of the beam would be 138 Kg. Maximum moment in the beam would be 619 Kgf*m and maximum vertical and horizontal shear are 285 Kg. To progress further you need the mechanical properties of the beams available to you and the strength of the material. 

These are not small values and I encourage you to get a proper engineer involved. What you want to do can probably be done safely, but I'm not sure it is a good do-it-yourself project.


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## Martin (May 8, 2008)

mahoney, all excellent points. These become quite impressive figures, from a 30kg kayak.
I will update the input I gave to my friend who designs gear boxes for a living. He has state-of-the-art mech design software.
Hopefully the final design that has everything factored in doesn't turn out too heavy to be mounted / dismounted by hand. Otherwise I really have to figure out a way to support the beam on its end, without being in the way of the load.


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## FredM (May 8, 2008)

mahoney said:


> Your winch and trolley weigh something as well, so let's allow 30 Kg for them (and the rope you are using to pull them in and out with, the pulley at the end of the beam, the extension cord...), and we need to consider the weight of the beam as well so lets allow 30Kg/m (assuming aluminium). So, some fairly theoretical math done, the downward force on the mount where the beam exits the building would be 522 Kg. .



30kg/m for aluminum? How thick will it be? Your numbers are crazy.

Here is the deal. Your boat weighs 30kg, if you raise it slowly technically there is a 30kg load on the "crane" once it gets moving. So I agree with the 1.5x assumtion made above for a large safety factor. 

However, if it does say fall a bit for some reason. Chain gets tangled or something:

1 meter fall means it will going about 4.4m/s when it stops it will weigh about 100kg. 

so above the safety factor of 4 seems ok as well so if it can handle 400kg you are ok for a hard fall and with a nice margin.

But in the real world you ladder worked so these numbers are useless.


This is what I would do as stated above by me and others. 

Use C channel beams 4 of them total like this

][ ][

put your rollers on the inside edges and put stops at the end. You can source these beams anywhere as they make car ports and covered parking with them. 

_____
][ ][

Bolt them together like above with some bracing. The c channel will be expensive so get galvanized. The best part is they will have the numbers for what one can hold when you buy it then you can decide how big to buy, 4 inch, 6 inch 8 inch, whatever. 4 of them will be strong as heck because 1 will be way stronger than your ladder.


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## dom (May 8, 2008)

Hi Martin
Yes- i'm walking again  thanks

I have to agree with Fred here -amazing that the ladder didn't snap.

I was going to suggest using the ladder on its edge as it will be much stronger but that doesn't give you much room to slide the boat thru the window frame -plus you probably already thought of that LOL

Cheers
Dom


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## mahoney (May 8, 2008)

30 kg/m might, or might not, be high depending on what type of beam is used. The beauty of going a bit high on beam weight in the calculations is not having to do the calcs over when you find your beam is heavier than you allowed for. The contribution of the beam weight is only about 1/6th of the moment value, and although calculating for a lighter beam would lower the shear values, this beam is probably most likely to fail in moment.

It's a small miracle the ladder did not fail, but it also means nothing went wrong at the moment when it was used. Things like cranes are over engineered because "stuff happens". For example, so far we have ignored potential wind load...

The light gauge C-channels suggested are a possible solution, however they are an "open" shape, the depth to material thickness ratios are high, and they have stability issues (failure can occur by rolling to the side). They work well for roofs because the flanges are held in place full length by the deck. A couple of them bolted on the outside of a rectangular tube could solve some of those problems, but the shape would need to be analyzed by an engineer.

As a real world example, I once saw a fall protection demonstration where 150 lbs of weight was dropped 6' on a cable attached to a jib crane arm and the dynamometer recorded the force of the weight stopping at over 1,200 lbs. That's an 8:1 factor. I certainly hope it would be noticed that the kayak had snagged before enough slack was out to allow a 6' fall, but in the world of overhead lifting, 4:1 is not considered much of a safety factor.


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## FredM (May 8, 2008)

mahoney said:


> but the shape would need to be analyzed by an engineer.
> 
> As a real world example, I once saw a fall protection demonstration where 150 lbs of weight was dropped 6' on a cable attached to a jib crane arm and the dynamometer recorded the force of the weight stopping at over 1,200 lbs. That's an 8:1 factor. I certainly hope it would be noticed that the kayak had snagged before enough slack was out to allow a 6' fall, but in the world of overhead lifting, 4:1 is not considered much of a safety factor.



Well that may be true for a factory, but this is a homebrew solution to doing it the hard way. 

The force that a fall produces is extremely related to if the system flexes. If that crane arm you saw moved .1" or ,01" that would produce a much higher reading than one that had 2-3" of flex in it. 

At any rate to calculate the force of a falling object you just take the speed when "caught" then over what length it is caught. This adds to the acceleration due to gravity and you recalculate the weight. It adds up fast for sure but in this application I cannot see it happening. I guess when lowering the boat, it is the most likely.


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## Martin (May 9, 2008)

One issue with the ladder is that it flexes. It flexes half the hight of the window, about 0.5 m ! So I have to pull the boat in at an angle.
The flexing also makes the boat rock a little vertically, as I pull it up. So I pull, then wait until the ladder calms down. Pull more, wait..

Initially, the flexing worried me and I thought the ladder would soon snap. I called my neighbor to look at it and tell me what he thinks. He's a practical guy, doing lots of work on his home. He had abused ladders in a similar way and said they just flex like this, they can even take more. So I proceeded. It worked.

My conclusion is, that if the calculation yields a beam that's bigger than the ladder (2 beams of 71.5 x 20 x 1 mm) I can expect less flex and it would be OK.
If however the calculation yields a beam smaller than what equals the ladder, something must be wrong.

Right now I expect that I need 4kg of aluminium per meter, using a rectangular cross-section beam. To be confirmed by my friend's computer. He will add in the factors 1.5 and 4.


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## FredM (May 11, 2008)

it is also the gauge of the alum not just the beam size.


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## HarryN (May 15, 2008)

The calculations are not that difficult for anyone trained in mechanical engineering. I used to know how to do this, and there are on-line calculators. Basically, you put in your load / torque, and it will tell you how much deflection will be seen. (There is always some). I will look for the link.

I used to do this in college (by hand), but that has been a few years, so I now use the very useful "rule of thumb" - for wooden beams - you want a depth of approx 1 inch per foot of unsupported beam length for "normal" loads.

A 30 Kg boat is well within "normal".

Alunimum is even stiffer than wood (around 2 x or so) - so it can be used with some confidence.

Rather than a "perfect" conversion, if you assume 8 cm depth per meter of unsupported length, and your "worst case unsupported length" is about 4 meters in that picture.

4 meters x 8 cm depth / meter length = approx 32 cm of depth to have less than 1 cm of "bending". This is pretty thick given your window size.

There are some simple things which can dramatically simplify this:

a) Attach a steel wire line from the end of the ladder to the outside peak of the house. The tension in this wire will help support the end, but of course, put an inward force on the beam. Assuming that you adequately support the end - then the unsupported length now drops from 4 meters to 2 meters.

b) Support your beam better - inside. The way it is rigged, the last point of attachment just inside the window is acting like a fulcrum (bending point) allowing a lot of beam bending just behind it.

c) Use a single piece beam - not a ladder with a sliding joint.

d) The load might seem symmetric, but in the real world, it is not. While an I beam seems right and is probably ok, a squre tube with a flange on the bottom for your moving part would actually be better. 

So, if you do ALL of those, then an Aluminum square tube a mere 15 cm on a side x 6mm thick would work nicely. (well supported - including the end with a steel wire) - double that if you do not support the end.

Interestingly, the same general recommendation as KC2IXE and others. Obviously - rules of thumb are not engineered solutions - just general ideas to gain some insight into the "minium" need.


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## Martin (Jul 3, 2008)

A friend of mine ran the mechanical simulation:
I need 30kg at 2.5m but in the name of safety, he overrated to 30kg at 3m:





The simulation says it will bend down 66mm at 30kg load. It will return to 0, once the load is removed.




If overloaded at 100kg, it will bend down 221mm and return to 0 once unloaded. A little more, and the beam won't come back. And a little beyond that, it will collapse.




When reversing the beam, the figures remain exactly the same (we were all a little surprised):




30kg load at 3m:




100kg load (the limit):





So I have ordered that 80 x 80 x 6mm T-profile of 6m total length.
Now I am looking for a pulley, ideally an electric one, that is not too heavy and big.
I will keep you updated and provide pictures if anything tumbles down.


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## BIGIRON (Jul 3, 2008)

OK, I'm certainly not an engineer and don't understand a lot of the above.

Since what you've got now works, with some concerns, and you are not endangering yourself or anyone else (that has enough sense to stay out from under the load) and you're only lifting 70lbs or so, here's what I'd try first.

Simply run a light cable (or even rope) from the very top of the eave to the rung of the ladder to which you've attached the pulley. I'd use an eye or hook lag bolt at the eve and connect the line to it and the rung with clips or carabiners. You can do this as you are initially sliding the ladder out.

Another alternative would be place the ladder from the ground to the window, with maximun extension to provide as slight a grade as possible and just pull the kayaks up the ladder with a rope. It would be easy to fabricate some type of sliding cradle for the ladder if necessary.

Keep it simple and start slow.

Very nice house and kayak. And you're right, from what I can see of the construction, it is very well built.

edit - as I look back, I realize the "slide on the ladder" system probably isn't feasible. I do believe the supporting guy line (someone mentioned it earlier) is worth a try. I don't really think you need the sliding "crab", but a coating of simple paraffin on the ladder will allow it to slide more easily.

You might consider an alternative to your crab. Attach a second line to the bow or stern bringing it in the window - not through your pulley - as the kayak approaches the opening, guide it in with the bow line and as you reach max lift, pull it into the opening while releasing (slowly) enough of the lifting line to allow it to pull into the opening. Simple system used on everything from ocean freighters to shrimp boats, probably prehistoric.


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## Martin (Jul 3, 2008)

There'll be more photos as this becomes real, possibly with some of your suggestions in it.
Maybe I skip the electric winch, it should be possible to lift 30kg with a manual pulley. The one I have now has too much friction but this should be easy to improve.


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## HarryN (Aug 20, 2008)

Hi Martin - how is this project working for you ?

The risk I see in the design is that the T beam will tend to twist during the lift - potentially causing failure. If you can add a few gussets or supports to reduce twist, that would be good. The 6mm thickness will help.

I looked again at your original pictures and info. Maybe I am just slow today, but my perception is that the T beam will actually bend more than the ladder did. In the case of the ladder, you effectively had 2 beams, each about 50 - 60mm depth in a box like structure (the ladder) to reduce twisting. Now you have just 1 beam, 80mm depth, and no constraint to twisting.

BTW, your load is not 30 Kg. If you were on the ground pulling on the rope, the load would be 2 x 30 Kg = 60Kg (each end of the rope). 

If you are in the attic (and the beam did not bend at all), then the downward force is actually 30 Kg + (30Kg x sin45) = approx 50Kg.

Since the beam bends substantially, the side force of you pulling on the rope adds to the beam deflection, so you are nearly back at 60 Kg of load on that beam from an engineering calculation viewpoint.

Please consider again the idea of adding a wire or rope from the end of your beam up to the peak of the house. If nothing else, this can help reduce the chances of a catastrophic failure during lifting. Two of them would be better.


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## Martin (Aug 21, 2008)

Harry, I have ordered the beam a while back and it is supposed to arrive some time in September. Once it's here, I will just have a go with this and see how it behaves.

Last time I used a manual pulley, pulled from the attic. I will redesign it with roller-blade wheels (tires removed) to reduce friction.

I'll keep you updated.


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## Martin (Oct 19, 2008)

The beam has arrived a while back. In a first attempt I had mounted this in a non-symmetrical way and it twisted too much. Beyond that, the crab had far too much friction. I never dared to use that setup, so there's no spectacular crash pictures to show.

Instead, I started looking around for an industrial crab and after a few weeks found something fairly small ( rated 300kg, weight 2.5 kg ) on EBAY. With this crab I mounted the beam in a perfectly symmetrical way.

Today I used it for the first time, lifting two hulls. It worked very well and the beam bent and vibrated little. Since all bearings are ball bearings, I needed substantially less force to pull - now there's no need to go electric. Mounting the crane takes 5 minutes and a single person can do it. The only thing I need to change is the way I secure the rope. What I've done now is neither safe nor convenient.

Photos:























When one of my neighbors saw the crane, he said he wanted one too. If this man DOES build his own, I would HAVE to go electric to stay one step ahead..


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## ICUDoc (Oct 19, 2008)

Hard to view the pics in that format Martin but very interesting.
Is that beam steel or aluminium? 66mm sound like a lot at only 30kg!
A really cool project and an interesting diversion- how are you going to light it for night-lifts????


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## Martin (Oct 19, 2008)

The beam is aluminum. To be precise, AlMgSi0.5 (6060) F22.
Dimensions are: Cross-section 80 x 80 x 6 mm, total length 6 m, total weight just 14.5 kg. For this, the bend is reasonable.

Good point about the night-lifts: For a start, I turn on all my flashlights, strobe mode preferable, then throw them into the hull. Cable and beam remain unlit.


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## ICUDoc (Oct 19, 2008)

Martin said:


> I turn on all my flashlights, strobe mode preferable, then throw them into the hull.



LOL! Good plan- the kayak would look like something extraterrestrial on a gentle rise away from the Earth.....


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## HarryN (Oct 23, 2008)

Hi Martin,

I am glad it worked out for you. Apparently, it worked much better than the last try with the ladder.

I could not help but notice in the picture taken from inside your storage attic - is that really a big steel frame beam making up the shape of the roof ?


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## Martin (Oct 23, 2008)

Harry, the structure that carries the tiles is all wood (never seen anyone used steel for this), only the vertical rear and front parts are brick / concrete, being an extension of the walls. Very common building style in Germany.


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## Martin (Jul 19, 2009)

It's summer 2009 and my boat crane still hasn't collapsed. I'm attempting to add a winch now.
Here's my first shot based on recycled parts: A bicycle rear hub with freewheel driven by a power window motor and fed by a computer printer power supply:




































This is the type of winch being used on boats. The drum turns continuously and the "clutch" is engaged just by pulling on the cable end that exits from the drum. See the video (the freewheel can be heard clicking away).
The motor has no reverse mode and the freewheel prevents the drum from turning backwards, too. So reverse is accomplished by slipping the cable.

Now there's just one problem that calls for a redesign of the motor part: It takes over a quarter of an hour to haul a boat up into the attic (8m) ! The motor runs at 24V and draws 0.3 A => 7.2 W, quite a small motor.
I tried 36V, current remains the same, power rises to 11W, still takes almost 10 minutes and the motor goes darn hot.
The next shot will use a motor from a garage door opener, expecting < 2 minutes for the way up. Stay tuned !


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## 65535 (Jul 19, 2009)

I may be missing something here. But it doesn't seem like it would be all that difficult to pull the boat up 10meters at 30kg. I imagine it could be done in less than a minute by hand. Or if you really want, just get a simple hand winch with a 2:1 or 3:1 gear ratio.


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## Martin (Jul 19, 2009)

This is what I thought first. I believed that with my 2:1 pulley, I must be able to lift a 30kg boat easily. But my cable is coming in overhead and pulling it too much downwards makes the beam bend more. So I am pulling the cable at an inconvenient angle. It feels a lot heavier than 15 kg (30 kg x 2:1 pulley). Actually, a 30kg boat is my limit.

Very briefly I thought about manual winches but the electric solution had some convincing advantages:
I'm not occupied operating a winch or pulling cable at the rear end of the beam but can stand near the window to control the boat moving up and warn people moving into the danger zone below.
Steady movement minimizes stress on the crane
Easier to build with the parts I had
My neighbor had electrified his 3m firewood elevator, I just had to go electric to show off..


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## 65535 (Jul 19, 2009)

When pulling from the ground you are applying a 2x load to the hanging point. You have the weight of the part being lifted, plus you have the force of you pulling up. Which is slightly more than the 30kg of the boat.

Obviously having a winch directly mounted to the lifting point is the best option. By having no external pulleys and using a winch mounted directly to the beam you minimize deflection AND it's the smallest force possible during lifting.


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## Martin (Jul 20, 2009)

Right, the winch at the lifting point would have been perfect. Readily-made winch & crab sets are available and I can pack the required length of cable (8m since no pulley) fully on the winch drum. Still I had to abandon this approach:
1) Adds far too much height for the boat to fit thru the attic window (pix earlier in thread)
2) A winch + crab set is at least 20 kg in weight and heavily overrated for my use

As long as I'm pulling in the direction of the beam, I'm not adding extra flex. I believe when I have the stronger motor, there will be nothing to wish for - unless maybe dual speed ?


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## dom (Jul 20, 2009)

Hi Martin
Looks very hi tech solution.
Have a look at this motor
http://secure.oatleyelectronics.com...d=192&osCsid=ad0a8a3dd8a526ebde636ca7472adb22

Pretty cheap even when you add price of controller
and throttle.

Have used them for making ebikes.
You'd need a couple car batteries or cheap jumps start kits for powering it though.

Probably AU$200 all up.

Actually i have a brand new one i'll never use you could have for postage cost.
Also think i have a freewheel mod you can bolt on to it. 

Cheers
Dom


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## Martin (Jul 20, 2009)

Thanks a lot for your offer, Dom. Don't get me wrong if I reject it though. I rather see this on an ebike of yours.

I'm really sold on the garage door opener which is perfect for my use, yielding a 50rpm / 70W motor and matching transformer. The other great thing about a garage door opener is that I can salvage a spare sprocket, chain, switches to maintain the one that is mounted in my garage. Plus I get 2 extra transmitters. Making the very best use of it.
Once the winch is working as desired, I'll update the thread.

Talking of ebikes, I recently borrowed one of the 45km/h Kalkhoff ones from a dealer. I got if for an hour. The coolest thing about it was maybe not the speed but the fact that suddenly racers and motorcyclists would talk to me, they never do when I'm on a regular bike.


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## dom (Jul 21, 2009)

Looking forward to what you come up with Martin.
The 45km/h Kalkhoff sounds like fun.

Cheers
Dom


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## Martin (Aug 30, 2009)

Finished, everything works, so this should be the final post on this project.
The modified winch uses a motor taken from a garage door opener:






Mounted:





Created a safer and faster mounting method for the Seacycle hulls:





Enhanced the rear mount of the beam:





Lifting a boat is now possible in a reasonable amount of time. Watch it on video:
1) The winch (50 rpm)
2) Boat being lifted
3) Hauling in

Remaining issues:
First, the climbing rope that I use, it somehow gets twisted after several uses. No big deal - I drop it down from the window and let it untwist.
Second, when not careful, the rope crosses as it runs onto the hub.

Future plans: None - just maintain it as it is. Happy with it, happy with the 7 min setup time.

Thank you for bearing with me !


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## precisionworks (Aug 30, 2009)

Very nice solution 

Watch out, when your neighbor sees yours he's going to want you to haul his firewood :nana:


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## choffman (Aug 30, 2009)

The rope crossing as it runs onto the hub can be rectified by tapering the hub or turning a new one with a taper.

Example of a wire tugger for electricians:







other views can be seen here:
http://www.greenlee.com/cat_docs/Cable_Pulling09.pdf

I'd be willing to bet that a decent ball bearing swivel connected to the end of the rope at the boat would stop/lessen the twisting.


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## Martin (Sep 13, 2009)

Thanks for that input, choffman ! Very effective and simple, the tapered drum. I'm tempted to touch that working system again ... have seen tapered bicycle hubs from time to time, so next one that comes along is put to good use.

The swivel is not such a good idea, I've actually had one in before. Without the swivel, the rope runs over the rollers though twisted in itself. With the swivel, the rope in itself tries to untwists and consequently, the leg that runs down from the crab to the swivel twists with the leg that runs from the swivel to the crab (see my drawing). This quickly locks both the crab movement and the vertical movement and so I went back to not using a swivel.


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