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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
Posted to rec.crafts.metalworking
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Frame
I want to build an overhead "H" shaped frame for LIGHT lifting. The frame
is for between two containers that are 15'6" apart. They are reasonably accurately oriented parallel and level their tops. I was doing a cut schedule layout, and saw a couple of things. Originally, I was going to put vertical posts coming down and resting on a plate on concrete. Then I thought that I could span the whole thing with one piece, and rest it on the top of the containers and make two span supports. My end goal is to have two parallel spans perpendicular to the containers, 10' apart so I can lift half my 16' aluminum boat with each span. I could achieve that with just putting two pieces of 3" x 3" x .120" across there. The lifting points would be outward from center, about three feet from the container, so I would not be lifting the heaviest thing at the center of the span. (One end of the boat would be heavier than the other. I want to be able to lift the boat and pull the trailer out to work on it at home.) I want one perpendicular center piece, forming a big H. The long legs will be 15'6", and the short leg 10' long. Am I okay to use this idea, and just rest them on the top of the container on plates I shall make? Or should I put a support pole along the containers for a total of four support poles? Should I make any "A" shaped reinforcement along the top of the two spreader bars to give the center a little more strength? Then put another short piece between the apexes of the vees to give it more strength? Does anyone know how to calculate what the lifting strength of the 15'6" beams would be? I mainly want this to lift items on to and off my welding table, and to turn pieces of fencing and gates during manufacture. Total weight, 200# max. The boat, I would say, with motor, weighs 1,000# max, but the lifting points would be outboard of center, I'd say the boat is 6-8' wide, so I would have about 8' divided by two on either side of the boat, putting more strain on the beam closer to center, not in the middle. I do know this is for light lifting. I have a lot of experience in rigging, and know how to do a lot of tricks in lifting. I personally think that if I put a vee shaped piece on top of each beam, about 8' wide, and 140 degrees at the apex, that would give me more strength, and help support the middle, hence less sag and more safety. The end product would look like a house from top plate up, except for side wall plates. End plates, vee truss, connector, and peak beam. Input? Steve |
#2
Posted to rec.crafts.metalworking
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Frame
Steve, go to www.pwr-tools.com and download their Engineering Power Tools.
The freeware can do this, or pay the $49 for the full version and lots more features. For 3"x3"x.120" wall square steel tubing with rounded corners, 15.5' (186") long, ends simply supported, load concentrated at the center, I calculate that a load of 1000 lbs would cause the center to sag 2.6" and the maximum stress would be 38.9 ksi. Yield strength for structural steel is in the 35-45 ksi range so 1000 lbs would just cause it to yield. If you want a factor of 5 safety margin you could lift 200 lbs with each beam, with the load concentrated at the center. The standard version can do all of that. Using one of the advanced version features to allow fancier beam loadings, if your load is concentrated at two points each 3.75' (45") from each end with 500 lbs at each of the two lift points so the total is still 1000 lbs, now the deflection at the center is 1.7" and the maximum stress is 18.8 ksi, which is about half the yield strength. So about 1000 lbs at each point (2000 lbs total) would just cause the beam to yield, and a factor of 5 safety margin would let you lift 400 lbs total - still less than half the weight of your boat. Your idea of a truss beam would greatly stiffen things up, but unfortunately pwr-tools doesn't do truss beams and my references are at work so I can't estimate how much stiffer, sorry :-). Hope that helps. ----- Regards, Carl Ijames "Steve B" wrote in message . .. I want to build an overhead "H" shaped frame for LIGHT lifting. The frame is for between two containers that are 15'6" apart. They are reasonably accurately oriented parallel and level their tops. I was doing a cut schedule layout, and saw a couple of things. Originally, I was going to put vertical posts coming down and resting on a plate on concrete. Then I thought that I could span the whole thing with one piece, and rest it on the top of the containers and make two span supports. My end goal is to have two parallel spans perpendicular to the containers, 10' apart so I can lift half my 16' aluminum boat with each span. I could achieve that with just putting two pieces of 3" x 3" x .120" across there. The lifting points would be outward from center, about three feet from the container, so I would not be lifting the heaviest thing at the center of the span. (One end of the boat would be heavier than the other. I want to be able to lift the boat and pull the trailer out to work on it at home.) I want one perpendicular center piece, forming a big H. The long legs will be 15'6", and the short leg 10' long. Am I okay to use this idea, and just rest them on the top of the container on plates I shall make? Or should I put a support pole along the containers for a total of four support poles? Should I make any "A" shaped reinforcement along the top of the two spreader bars to give the center a little more strength? Then put another short piece between the apexes of the vees to give it more strength? Does anyone know how to calculate what the lifting strength of the 15'6" beams would be? I mainly want this to lift items on to and off my welding table, and to turn pieces of fencing and gates during manufacture. Total weight, 200# max. The boat, I would say, with motor, weighs 1,000# max, but the lifting points would be outboard of center, I'd say the boat is 6-8' wide, so I would have about 8' divided by two on either side of the boat, putting more strain on the beam closer to center, not in the middle. I do know this is for light lifting. I have a lot of experience in rigging, and know how to do a lot of tricks in lifting. I personally think that if I put a vee shaped piece on top of each beam, about 8' wide, and 140 degrees at the apex, that would give me more strength, and help support the middle, hence less sag and more safety. The end product would look like a house from top plate up, except for side wall plates. End plates, vee truss, connector, and peak beam. Input? Steve |
#3
Posted to rec.crafts.metalworking
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Frame
http://www.flickr.com/photos/deserttraveler/
Here's a pencil drawing. It is all 3 x 3. The house like frame would give it rigidity, and take some of the bending out of the cross pieces by transferring it into compression at the peak. The peak will keep the thing from torquing. The D rings will be the lifting points for the boat, but other than that, there will be three roller D rings on the main 20' beam. Where it sticks 5' out from the crossmembers, it will be supported by chain to the peak. The biggest thing I will lift with this are an aluminum boat with a 40 hp motor @ the four points, about 3' in from the sides where they rest on top of the plate on top of the container. After that, the maximum I would lift would probably never reach 500#, but it would be used for items up to 150# during construction of the item on the welding table. By your estimation, Carl, it should be safe for that. What do you think of this design? I know I could overload this, but I know the weight I would be lifting, and I'm thinking 300# would be a big lift. This is not the design that I would like to do, but a compromise. I want to keep the open space without losing it to supports. I was an Offshore Petroleum Institute certified rigger, various union OSHA certified courses, and a crane operator. I know this will do what I want it to do, be an extra man for me when I need to flip a piece of fence, or lift something up on the table to work on or weld. I'm just trying to get an idea on the max load, and then I'll divide by 4 or 5 and live with that. Steve |
#4
Posted to rec.crafts.metalworking
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Frame
The simple beams were within a factor of 2 or 3 of just enough, so my gut
says your truss will be plenty - I just can't back it up with numbers without looking up some stuff. If I get a chance tomorrow at work I'll try. ----- Regards, Carl Ijames "Steve B" wrote in message . .. http://www.flickr.com/photos/deserttraveler/ Here's a pencil drawing. It is all 3 x 3. The house like frame would give it rigidity, and take some of the bending out of the cross pieces by transferring it into compression at the peak. The peak will keep the thing from torquing. The D rings will be the lifting points for the boat, but other than that, there will be three roller D rings on the main 20' beam. Where it sticks 5' out from the crossmembers, it will be supported by chain to the peak. The biggest thing I will lift with this are an aluminum boat with a 40 hp motor @ the four points, about 3' in from the sides where they rest on top of the plate on top of the container. After that, the maximum I would lift would probably never reach 500#, but it would be used for items up to 150# during construction of the item on the welding table. By your estimation, Carl, it should be safe for that. What do you think of this design? I know I could overload this, but I know the weight I would be lifting, and I'm thinking 300# would be a big lift. This is not the design that I would like to do, but a compromise. I want to keep the open space without losing it to supports. I was an Offshore Petroleum Institute certified rigger, various union OSHA certified courses, and a crane operator. I know this will do what I want it to do, be an extra man for me when I need to flip a piece of fence, or lift something up on the table to work on or weld. I'm just trying to get an idea on the max load, and then I'll divide by 4 or 5 and live with that. Steve |
#5
Posted to rec.crafts.metalworking
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Frame
"Carl Ijames" wrote
The simple beams were within a factor of 2 or 3 of just enough, so my gut says your truss will be plenty - I just can't back it up with numbers without looking up some stuff. If I get a chance tomorrow at work I'll try. ----- Regards, Carl Ijames "Steve B" wrote in message . .. http://www.flickr.com/photos/deserttraveler/ Here's a pencil drawing. It is all 3 x 3. The house like frame would give Steve, Based on Carl's previous numbers I would tend to agree that it should be sufficient. I would personally move the angles out until they are over the edges of the containers (opening up the 140 deg apex and leaving the height about the same). This will deliver the load from the center I beam to the containers directly instead of just stiffening the middle of the cross bars. Leaving the "boat hooks" mid span on your cross bars should not be a problem. I am sure you would think of it, but I would also weld 4 stops to the cross bars so they can not slide across the roofs of the containers. -- Stephen B. Remove the first Spam only to e-mail directly |
#6
Posted to rec.crafts.metalworking
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Frame
"Stephen B." wrote Based on Carl's previous numbers I would tend to agree that it should be sufficient. My gut says it's good to go, but approaches strain at 350# on center beam, and redlines at 500#. I have a 497# atv that will be a test lift, and deflection noted. Perhaps even put in vertical temporary stiffener whenever lifting more than 350#. I would personally move the angles out until they are over the edges of the containers (opening up the 140 deg apex and leaving the height about the same). It's all 3 x 3. The reason I brought them in is that is the point of attachment to lift the boat, the biggest thing I'll lift. This will deliver the load from the center I beam to the containers directly instead of just stiffening the middle of the cross bars. Leaving the "boat hooks" mid span on your cross bars should not be a problem. I am sure you would think of it, but I would also weld 4 stops to the cross bars so they can not slide across the roofs of the containers. Better than that, four base plate structures will be welded to the tops of the containers to receive the ends. NO CHANCE OF MOVEMENT ONCE IT IS WELDED OUT. -- Stephen B. Thank you for your comments. Steve |
#7
Posted to rec.crafts.metalworking
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Frame
"Carl Ijames" wrote in message ... The simple beams were within a factor of 2 or 3 of just enough, so my gut says your truss will be plenty - I just can't back it up with numbers without looking up some stuff. If I get a chance tomorrow at work I'll try. ----- Regards, Carl Ijames Appreciate it. Now's the time to do the numbers. This gives me a clear span under the lift, converts downward bending to compression, and just stiffens and strengthens in several ways. Steve |
#8
Posted to rec.crafts.metalworking
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Frame
"Steve B" wrote in message . .. Appreciate it. Now's the time to do the numbers. This gives me a clear span under the lift, converts downward bending to compression, and just stiffens and strengthens in several ways. Steve Have you considered wood? http://www.awc.org/technical/spantables/tutorial.html In Fig 3 a 2x12x16' falls within the range you are looking for. Pressure treated syp (Southern Yellow Pine) is nearly as strong as oak and doesn't need protection from the weather. You do have to brace it to stop twisting but the H center bar helps. Pick two without knots on one side and make it the bottom. jsw |
#9
Posted to rec.crafts.metalworking
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Frame
Ok, I got out my old book and did a little trig :-). For a simple
triangular truss with two equal sides and a horizontal crossbar at the base, the load needs to be applied at the joint at the apex of the angled risers. That places the angled risers in pure compression and the horizontal bar in pure tension. You can drop a vertical bar from the apex to the center of the horizontal beam and apply the load at the base of that, if you want, just make sure it can support the entire load in tension. If you use two lift points part way up each angled riser, that adds bending stress and greatly weakens the assembly. Here are a few equations for you: length of horizontal beam: L angle of base of risers with horizontal beam: T load applied to apex: W length of each angled riser = L / (2 * cos T) height of apex = (L * tan T) / 2 compressive force on each angled riser = W / (2 * sin T) tensile force on horizontal beam = W * cos T So, if L=15.5'=186", W=1000 lbs, and T=30 degrees: length of each angled riser = 186 / (2 * cos 30) = 107.4" height of apex = (186 * tan 30) / 2 = 53.7" compressive force on each angle riser = 1000 / (2 * sin 30) = 1000 lbs tensile force on horizontal beam = 1000 * cos 30 = 866 lbs Using eng. pwr tools, one estimate of the compressive load a slender beam like 3" square tube 107.4" long can support 8900 lbs with a safety margin of 5x. The cross sectional area of 3" square .120 wall tube is 1.34 in^2 and if the tensile strength is 35,000 lb/in^2 the horizontal beam can handle 35,000 lb/in^2 * 1.34 in^2 = 47,000 lbs, or 9,000 lbs with a factor of 5 margin. Gosh, one truss like this can handle 9,000 lbs (if you can keep it upright :-)). Anyway, play with the formulas to find an angle you like. ----- Regards, Carl Ijames "Steve B" wrote in message . .. "Carl Ijames" wrote in message ... The simple beams were within a factor of 2 or 3 of just enough, so my gut says your truss will be plenty - I just can't back it up with numbers without looking up some stuff. If I get a chance tomorrow at work I'll try. ----- Regards, Carl Ijames Appreciate it. Now's the time to do the numbers. This gives me a clear span under the lift, converts downward bending to compression, and just stiffens and strengthens in several ways. Steve |
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