Truss vs. I-beam for hoist?

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I want a way to lift objects both in my garage and in front of the garage,with a beam starting at the back of the garage and sticking out 3 - 4ft. through the front over the door. While looking at weights and prices of I-beams, I started wondering if I could use lesssteel by building a  truss like I've seen supporting roofs in factories.These are typicallybuilt of angle,top and bottom with rebar diagonals between them. I'm just wondering if anyone has tips, ideas, examples.(BTW I'm thinking I'd be lifting 700# cantilevered 4 ft.from support.)Miller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:Either will work, but it is quite likely that you don't have enough clearance for a truss. Also if you are running the hoist outside on a trolley, you will need a larger flange than what you will find on a standard truss. If you are going to run it outside over the door, you will have to make modifications to the header.
Reply:Trolley is out due to overhead door.I just want one lifting point outside and several inside,I was planning on adding steel header on columns ( on sides of the door)  for supportAs for clearance,there is about 2ft. between top of header and inside peak of roof.Miller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:Trusses require lateral support to work.   Roof trusses are attached to the plywood or other roofing material, and often braced on the bottom as well.Designing a truss is not a trivial matter.    Designing for an I-beam or H-beam is easier.   I agree that a truss would be lighter, but an I-beam would be simpler.   Have you considered what size beam you would use?   Generally, you can save weight with a larger beam that is not as thick.   One time I had to design a beam with limited headroom, and ended up specifying the heaviest 6 inch beam that was available.  Sounds like you have plenty of headroom.I took a quick look at the stress numbers for 750 pounds at the end of a four foot cantilever, and came up with a 4 inch I-beam, which weighs 8 pounds per foot, so not crazy heavy.  I did not try to look at deflection, however, which might call for something bigger.  Another question is how closely it would be supported inside, and how it will be supported.  You don't want to cave the roof in.  20 feet long times 8 pounds per foot is 160 pounds, maybe $150, so not prohibitive.I would still add a trolley, even if it would not go out the door, convenient inside.RichardSculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:Could you install the beam with the trolley inside, and use an engine hoist for your outdoor lifting?The cantilevering idea just doesn't sound good.Trusses absolutely require side support, and your roof truss would not work.  For it to work on a roof, you need multiple trusses, with a deck (and lower supports) preventing lateral and twisting movement.You could build a box shaped truss.  Think about what is used to support stage lighting.But that would only save weight off an I beam, might not be any stronger, would require some serious engineering, and probably rules out using a trolley.An I beam with a cantilevered end would also be a risky setup, because while the beam may be strong enough to hold your load "by the numbers", I beams left unsupported fail by twisting, and can drop the load at a much lower stress than you may expect.
Reply:Originally Posted by rafergusonTrusses require lateral support to work.   Roof trusses are attached to the plywood or other roofing material, and often braced on the bottom as well.Designing a truss is not a trivial matter.    Designing for an I-beam or H-beam is easier.   I agree that a truss would be lighter, but an I-beam would be simpler.   Have you considered what size beam you would use?   Generally, you can save weight with a larger beam that is not as thick.   One time I had to design a beam with limited headroom, and ended up specifying the heaviest 6 inch beam that was available.  Sounds like you have plenty of headroom.
Reply:[QUOTE=jpump5;489045]I want a way to lift objects both in my garage and in front of the garage,with a beam starting at the back of the garage and sticking out 3 - 4ft. through the front over the door. built of angle,top and bottom with rebar diagonals between them. I'm just wondering if First thing you should do here is forget the idea of using rebar in the fabrication of a truss!!!Bgbkwndo.
Reply:[quote=Bgbkwndo;489202] Originally Posted by jpump5I want a way to lift objects both in my garage and in front of the garage,with a beam starting at the back of the garage and sticking out 3 - 4ft. through the front over the door. built of angle,top and bottom with rebar diagonals between them. I'm just wondering if First thing you should do here is forget the idea of using rebar in the fabrication of a truss!!!Bgbkwndo.
Reply:Thanks for replies-   I  was thinking i would need a larger,more expensive i-beam.I guess a truss is not the way to go.I still need to look at means of supporting  beam. I realize truss design is not a simple matter.Was looking at the possibility of copying existing design from similar application. The reason I mentioned rebar for diagonals is that I've seen it used in trusses of steel buildings.Never thought about the weldability of rebar.Miller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:I'm no engineer but I think another issue you need to consider is whether the truss or I-beam or whatever can twist in the middle under load, because many things are a lot stronger in one direction than in other directions, if that makes sense. In other words, if the supporting member can twist, in many cases it can fail a lot easier than if it was prevented from twisting.Last edited by Kelvin; 03-22-2011 at 08:10 AM.
Reply:I know you are already going to use an I or H beam but I will throw this out there on the subject. A truss is not going to handle a single point load like an I or H beam would. The span between the webs on the truss where there is no support will possible sag asyou roll by them. The H or I beam is better in that the top and bottom flanges are tied together the whole way. Inbetween webbing on the truss, it would have to act like a small I beam and that is not what they are designed for, their load is supposed to be spread out more.Millermatic 252Lincoln 175 plusTA 185tswTA 161stlhypertherm pmax 45Victor torchHenrob torchAn S10 for each day of the week
Reply:Standard off-the-shelf roof truss, used as a cantilevered lift point?Nope.Could an engineered truss-like structure be used as a cantilevered lift point?  Sure.  Go pay the engineer to design such a thing for you.  Not all that difficult.But remember that a lifting point up in the air has to have the correct structure underneath it to transfer the loads properly.btw, rough rule-of-thumb for building cantilevers is to make the structure 'behind' (into the building) 3x as long as the cantilever extends out.  So for a 4 ft cantilever, you want 3x4=12 ft of beam/joist/structure properly supported going back 'into' the main structure.Did you consider just using  an engine hoist to lift stuff up?  The best laid schemes ... Gang oft agley ...
Reply:Originally Posted by jpump5Thanks for replies-   I  was thinking i would need a larger,more expensive i-beam.I guess a truss is not the way to go.I still need to look at means of supporting  beam. I realize truss design is not a simple matter.Was looking at the possibility of copying existing design from similar application. The reason I mentioned rebar for diagonals is that I've seen it used in trusses of steel buildings.Never thought about the weldability of rebar.
Reply:Yeah,The bar joist for lifting beam idea wasn't great. (torsion,single point loading etc.)I assumed it was called a "truss" because of it's appearance.Engine hoist isn't my favorite option,but not ruled out.-ThanksMiller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:There is a major difference between a truss and I-beam. I-beams are used for trolleys because you can load the bottom of the I-beam. You can not run a trolley along the bottom of a truss. The bottom of a truss is never to be used for a load. If you use a truss, you must run the trolley along the top of the truss.As others mentioned, an I-beam would be a better choice due to the twisting that will occur in a truss.
Reply:Originally Posted by A/C GuyThere is a major difference between a truss and I-beam. I-beams are used for trolleys because you can load the bottom of the I-beam. You can not run a trolley along the bottom of a truss. The bottom of a truss is never to be used for a load. If you use a truss, you must run the trolley along the top of the truss.As others mentioned, an I-beam would be a better choice due to the twisting that will occur in a truss.
Reply:Originally Posted by rlitmanI beams are prone to twisting too.I don't get why it matters whether or not a trolley is run on the top or bottom of a truss.Just look at a truss bridge.  The roadway is often on the bottom.
Reply:to get inside the garage roll up mount another i beam under the beam on a set of roller trolleys ...roll the beam out the door then use the trolley on the beam to roll it into the garage.... like was said above the 3 to 1 rule sounds right for the length of the rolling beam.After the arc has died the weld remains
Reply:Originally Posted by Boilermaker237to get inside the garage roll up mount another i beam under the beam on a set of roller trolleys ...roll the beam out the door then use the trolley on the beam to roll it into the garage.... like was said above the 3 to 1 rule sounds right for the length of the rolling beam.
Reply:we had fabricated a roller to place between the beams to allow for the lift on the tail end.You want to lift plate out of the bed right?how much overhead room will there Be?After the arc has died the weld remains
Reply:Originally Posted by Boilermaker237we had fabricated a roller to place between the beams to allow for the lift on the tail end.You want to lift plate out of the bed right?how much overhead room will there Be?
Reply:[quote=Bgbkwndo;489202] Originally Posted by jpump5I want a way to lift objects both in my garage and in front of the garage,with a beam starting at the back of the garage and sticking out 3 - 4ft. through the front over the door. built of angle,top and bottom with rebar diagonals between them. I'm just wondering if First thing you should do here is forget the idea of using rebar in the fabrication of a truss!!!Bgbkwndo.