Page 3 of 15 FirstFirst 1234513 ... LastLast
Results 21 to 30 of 148

Thread: Norman's Jib Crane adventure

  1. #21
    Join Date
    Dec 2015
    Location
    Chilliwack, BC, Canada
    Posts
    2,889

    Default

    Quote Originally Posted by RichR View Post
    Just my opinion, but I think your test is flawed. In each case your chain transfered the load to the top of your rig. I don't think that's the same
    as moving the boom pictured here up or down on the mast:.......

    Try this setup again ...... but this time attach the chain to the first crossbar above the boom. I think you will get a lower reading due to better leverage.
    Rich, it doesn't matter if the post and arm are welded or chained. It's still a system of connected lever arms that connect the two points of support and the load. The only thing that will change by moving the chain anchor is that the tension of the chain will rise due to the change in angles.

  2. #22
    Join Date
    Apr 2012
    Location
    Sydney
    Posts
    650

    Default

    Quote Originally Posted by RichR View Post
    Just my opinion, but I think your test is flawed. In each case your chain transferred the load to the top of your rig. I don't think that's the same as moving the boom pictured here up or down on the mast.
    It all does play tricks with the mind ... leastways has been for mine. For quite some time I had all the balls in the air, and only after some of them started to settle did the forces start to make sense.

    I do not think you are saying this, but for clarity, the chain at top of mast is attached to the top of the mast; it does not run over (in running wheel fashion) to attach directly to the scale.

    The assumption is that the mast is rigid enough to keep the top and bottom of the mast plus the boom in the form of a tidy right angle. When all this is true it does not matter how the triangle is formed; the boom will transfer push and pull to the bottom and top of the mast in equal quantity.

    Norman

  3. #23
    Join Date
    Apr 2012
    Location
    Sydney
    Posts
    650

    Default

    Quote Originally Posted by George Bulliss View Post
    ...
    A quick search of the internet shows a 1/2 ton crane with a reach of 8-12 feet requires a reinforced footing 4 feet deep and 4 x 4 feet in length and width. Your cement slab certainly isn't going to take that kind of load and I wouldn't think the roof is going to be able to take the remainder.

    Now, your plan is half the weight of the example I found, but the reach is the same and I bet the foundation requirement isn't much different. I would do some searching of manufacturer's sites; looked like there are a lot of specs to be found.
    Thanks for your input George. I do see the big footing requirement for some Jib Crane designs. Those with free standing columns (no anchor of mast at top) certainly do require considerable footings.

    My investigations at this stage are into the mast style as that seems to be the least stressed option.

    The wall mounted style is certainly out ... not enough wall strength for a single crane. Could put in several baby cranes, but would prefer not to.

    I have not ruled out the free standing style; or of something that is part free standing style that also has an anchor at the top.

    I did go the "extra mile" with the slab. The slab is of raft construction, 200mm thick with 2 layers of reinforcing bar. The raft sections are 400mm x 300mm and have another layer of reinforcing bar within them.

    For free standing style it really comes down to how large a footprint the free standing base is. Too large and you have to either "trip over it" or call it another floor level.



    Norman

  4. #24
    Join Date
    Apr 2012
    Location
    Sydney
    Posts
    650

    Default

    Quote Originally Posted by Tundra Twin Track View Post
    In the locked position there would be no swivel,it just gives you a very rigid setup for lifting heavy load.If your shoulder is rigid enough on wall,you could lift what ever I beam could hold
    Hi Tundra, Yes I do see it. It would work. The rig essentially becomes a Gantry Crane in concept.

    Norman

  5. #25
    Join Date
    Dec 2015
    Location
    Chilliwack, BC, Canada
    Posts
    2,889

    Default

    Norman, center or wall would be much the same. Either way the walls would see the upper pivot side loading. With a wall mount you'd still need to radially brace away from the pivot point and connect the other walls into a supportive system. Otherwise you're right and the one wall would flex and that would confine the load to a rather small section of it. So spider webbing the loads out to the whole structure is needed. But you need that anyway. Standard building design is for moderate wind generated side loading and mostly vertical loading from wet snow. Or if you're building to "tornado alley" standards then there will be some additional side loading built in.

    Using a spreader system to make it a self supporting design could work. Especially if you located the machinery and heavier item storage around the sweep of boom. Is that the intent? Similarly the jib would work well too provided you don't try to swing it out to the side while loaded. If it's more of a lock in place and use extension then the inner boom would not see any significant twisting force. If you need to pass through the "short pass" roll the carrier in towards center, fold the jib, swing past the short point then fold out the jib and extend the load. THAT would work just fine since the boom would not see any torsional loads.

  6. #26
    Join Date
    Apr 2012
    Location
    Sydney
    Posts
    650

    Default

    Quote Originally Posted by BCRider View Post
    Norman, as you're fast learning the top will produce a large side force on the roof structure and by connection to the walls. The walls will likely need something stronger than drywall on the inside and cheap chip board on the outside to deal with the racking forces. That's all going to cause you to up the construction quality of the walls and either brace from the walls through the stock trusses to support the upper mount or to have the trusses engineered with additional sideways trussing to handle the side loads that normal trusses and roofs are simply not designed to handle. It may be that using plywood for the inside ceiling along with some diagonal and cross connectors between the trusses is enough for general stress with some additional material around the upper mount. But clearly some significant bracing over and above regular trusses at the point of the mount itself will also be required to spread the load out into the structure.
    Shed is of metal construction similar to the one in the picture. Mine will have two roller doors at same position as the image plus another at the corner of the near end in the image. There are 3 bays each 4m x 8m.



    Inside they look similar to this image. To be fair they are built strong. They are cyclone rated. The ONLY difference between the full cyclone spec and the one being assembled is the addition of cross bracing via tensioned wires instead of the flat straps in the image. I am investigating retrofitting that option into roof and walls using 3/16" (4.8mm) wire rope of 6x7 construction. Those ropes have 13 tonne breaking strain (way more than needed) though the idea is to create some more rigidity.

    I am very much still working thru design options; but I do have it the max sideways force on roof structure will be <240kg with a load of 100kg on a fully extended 6 meter boom. Somewhat <90kg when unloaded. That 90kg feels trival to me and could itself be totally removed with a little counter weight.




    Quote Originally Posted by BCRider View Post
    I would also pay careful attention to the concerns over that swinging jib on the end. The guys warning about twisting the main boom have a valid point.
    Point taken and very valid. The main boom for a cantilever design cannot be an I or W beam. Both the main boom and the cantilever boom need to be of RHS type. The mast could be an I or W beam; though it being RHS may be a better option also.

    Question is how much RHS? The test done with the 5 meters boom with an 80kg load sitting on the end showed me that a beam of that size is NOT required. In that first test even the 75mm x 50mm x 4mm RHS that was used to support both the 3.7meters of W-beam and an 80 kg weight did not seem stressed.

    I did reverse engineer a commercial articulated unit, with similar span to that proposed, using the total weight of the crane and the dimensions provided. I have it they used 200mm x 8mm RHS for the first section of the boom and 150mm x 6mm RHS for the articulated section. I think they have enough steel in this to prevent ANY FLEX.

    The W-beam in my first test was 160mm deep; this was way more than needed. There was no flex.

    My engine crane has been used to lift 3000lbs (1.4 tonne) of my Kondia FV1 mill with boom at full 1500mm extension. It uses primary boom of 70mm x 4mm RHS and 60mm x 4mm RHS for the extension. Sure it loaded up big time but it got the job done ... I am comfortable to say just.

    I am thinking 150mm x 6mm RHS for the first section of the boom and 100mm x 5mm RHS for the articulated section. I don't think we are at risk of a sudden breakage. More likely, when and if overloaded, is it will just sag to the floor. Should it be found to be too springy then I can up the spec.

    Quote Originally Posted by BCRider View Post
    I also would find a derrick boom of that sort a major PITA to have sitting central to the whole shop. I'd want that area available for assembly of larger items or to even pull in a vehicle for some work if needed. A fixed feature like that one kills off a lot of options.
    Somewhat disagree with this. That end bay of the shed is the workshop. It will be full of machines, benches and cabinets. Remember the shed is 8 meters wide; there will be room for a corridor each side. Do agree that lost is some "clear air" above in the immediate area of the mast.

    If I don't like it in that position I can move it to the end wall. It would then only sweep the end bay rather than two bays ... time will tell.

    Quote Originally Posted by BCRider View Post
    And if you're looking at a 200 or even 300Kg max load I'd suggest that this is a LOT of commitment for picking up and moving what is really not that large a maximum weight. With far less effort and a lot more flexibility of use I believe you could come up with a roll around lifter that neatly parks in a corner when not needed.

    For myself and others that magic "skyhook" is in the form of a common engine hoist. And certainly for myself it's been super handy. All my current major machine tools were moved from the old shop and/or brought into the new shop and placed with relative ease. But it does take up a lot of floor to maneuver and use.
    I am way over those rolly rolly things in my shop. I agree use of the engine crane in the shop is a PITA. Can never get the engine crane into position when needed. For use near the mill it can be done, but only if I clear an area large enough to swing it in. For the lathe it is hopeless; the arms/leggy things simply do not go under the lathe.

    Quote Originally Posted by BCRider View Post
    I've also got this image in my mind of a smaller footprint lift that uses a large deep cycle RV or marine battery and a cable winch as the power source. The winch and battery would be the counter weight for the items being lifted. The battery and winch would be down low on the rig to try to hold the center of gravity low and reduce the tip over tendency but would swivel with the upper arm. I don't see it being much larger for a rolling footprint than about 1x 1.5 meters yet with the battery and winch as a counter weight it should be able to extend some reasonable shop loads as chucks or other larger tooling out far enough to allow you to place them on the spindle or tables of machinery.
    Thanks for agreeing that a counterweight is a valid consideration in the design of a crane

    Norman

  7. #27
    Join Date
    Apr 2012
    Location
    Sydney
    Posts
    650

    Default

    How about this as an option to assist stiffening the upper building structure.

    At each of the red lines in the image below I attach a vertical beam to the block wall; then run (say) a 25mm all-thread rod from each thru to the building structure. The two side ones attaching to the building columns; the end one to the high point of the end beam frame.

    I figure those, together with cross brace stiffening wires would add considerable additional rigidity.

    The block wall on the left is 1200mm high. The one at the back a little lower; about 800 at the point marked.

    The block wall is integral to the slab. There is a set down between the slab and the wall, for water drainage and access (the visible portion is about 500mm wide x 90mm deep) and runs under the wall. It was poured with the slab with starter bars rising into the wall. The wall is reinforced with additional vertical and horizontal bars, plus is core filled.



    Thanks to participants for keeping the juices flowing at this end.

    Gee I might even be able to load up the rig to 500kg or so.

    Norman

  8. #28
    Join Date
    Dec 2007
    Location
    South Wales
    Posts
    6,246

    Default

    There is always the option of a removable leg support from the end of the jib to the floor, either a single box section tube or an A frame that can be inserted should you need to lift greater loads, with the addition of a couple of heavy duty castor units the SWL will be considerably greater than the free cantilever that the unsupported jib is, the King post cranes I've had fiddlings with had the King as tall as you can fit, the jib lower and a tie bar between jib tip and top of the King post, some had quite respectable safe working loads, several has a steel cable tie with cleats or crimp eyes on, think tower crane, I must admit I didn't like the knuckle jib option, as was pointed out the torsion on the jib would be considerable, I haven't tried working any numbers out but from previous experience with a jib tip drop leg you should easily lift a ton, safely but it should be worked out properly, I think you'll get near 250kg at full reach going by what was over our lathe in work, the cranes and lifting inspectors were ultra fussy and used bonkers factors of safety, the same as lift cages, the thing that caught everyone our was all the calcs were done, the crane assembled and it failed due to nuts and bolts, cheap crap, they were correctly marked but the threads on the nuts were oversize and stripped, clang.
    It will be a really nice place to work when finished
    Mark

  9. #29
    Join Date
    Apr 2017
    Location
    Kelowna BC
    Posts
    554

    Default

    I dont think the 4 ft deep anchor would have been a problem, if the floor was not yet in.
    So i had this thought, if you had a 12 foot wide door at one end of the shop, and could live with your lathe and mill there....could you mount the crane outside the end of slab (with proper anchor), and be able to swing inside to the machines.? I know it doesnt reach much of the shop.

  10. #30
    Join Date
    Dec 2015
    Location
    Chilliwack, BC, Canada
    Posts
    2,889

    Default

    Norman, your reply above to my post shows you've given this a LOT of thought and have most of the bases covered. From your load testing which seemed fairly recent I didn't think you were that far along with the idea.

    I do agree that the RHS tube would be a lot stronger in torsion. But doesn't that cause problems with moving items long the length of the boom? Would you add a track of some sort or will it have a larger section that wraps around and wheels that ride along the top of the RHS?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •