Laminated beam

[shvl73]

If you end up going with a wood beam (LVL, Paralam, etc,) the lumber yard you'd order from should be able to spec the beam size and design the bracing layout per your requirements (point load, support locations, etc,) they will have software and can have the distributer assist where needed. If they are a good pro oriented yard, they should be happy to help. After all, its about getting the sale.

An LVL beam my be easier to install if it can be laminated and through bolted in place rather than put up as an assembly. This would also depend on you tractors lift capacity and loader height.

 

[Tom_Veatch]

...Tom, can you elaborate on this.I do have trusses above where the beam would go but do you mean support it on the ends and attach to the trusses?.

That comment came from a background in which minimum weight had prime importance with cost being secondary. In this case, a single simply supported beam is probably your minimum cost solution.

What I was thinking was, if your hoist trolley rides the top surface of the beam, the top plus at least one side of the beam would have to be kept free of obstructions to allow the hoist to traverse. In that case, a simply supported beam would be about the only choice. But, if the trolley rides a track attached to the bottom of the beam (which has it's own design challenges) there is a possibility that the beam could be tied to and supported by existing or additional building structure.

The trusses I see in the pictures look to be standard roof trusses - 2x4 lower chords and braces with 2x6 upper chords. They are normally designed for expected roof loads plus 200# vertical load on the lower chord (primarily to accommodate personnel walking the beams during construction). I wouldn't consider them as candidates for significant support for your hoist. Especially since it appears your installation will run parallel to those trusses.

You could, again assuming that the hoist trolley rides the bottom of the beam, install a truss in which your beam is the bottom chord. That could minimize the size and weight, but would likely be a more expensive solution.

Since the beam must be designed for stiffness rather than strength, and steel is some 20x stiffer than wood (Young's Modulus for steel is about 30x10^6 and about 1.5x10^6 for wood), I suspect that your best, most satisfactory solution would be a simply supported structural steel I or H beam with the hoist trolley riding the lower flange of that beam. That would essentially remove the concern for beam instability mentioned in an earlier post and should be a simple, straightforward installation.

Using the assumptions previously stated, a simply supported standard I-beam 10" deep by 4.66" wide (25.4 #/ft ~ 750#) would be sufficient to meet the bending loads with the stated safety factor. This, in no way constitutes an engineering analysis and is no guarantee the beam is suitable for the purpose.

 

[bones1]

Thanks Tom for your insight.The steel beam sounds like the way to go except for working with that much weight.Building a wooden beam in place would be a lot more manageable,I think?.Or should I even attempt it?
More pondering to do.

 

[Tom_Veatch]

...The steel beam sounds like the way to go except for working with that much weight.Building a wooden beam in place would be a lot more manageable,...

Building a wooden beam in place is feasible and would mean that you wouldn't be dealing with as much concentrated weight. Though, a 6x18 wooden beam would wind up weighing almost as much as the 10" steel I-beam.

Understand I do not recommend this approach, but just as an exercise in imagining a hypothetical case, if I were going to do something like that, I'd try to select a bunch of 20' SYP 2x6's with the straightest grain and as free of knots and warping as I could find. I'd be very sure there were no loose knots, nor any knots greater than about 1" diameter or within about 1" of the edge of the board.

I would then lay 12 layers insuring that the end joints between boards or defects such as knots or squirrelly grain did not coincide in any two adjacent layers. I would use a good quality polyurethane glue between each layer being sure there was complete coverage in the glue line between each layer and clamp the s**t out of each layer until the glue set before going to the next layer.

A I laid each layer, I would make sure that each layer was straight and that the stack was building as near to square as possible. I would also build a temporary central support that was tall enough give the beam a slight (1/2" to 1") crown at the center before the hoist was installed and the beam loaded. I would not use any mechanical fasteners (bolts, screws, etc.) since a proper glue joint will exceed the strength of the adjoining wood.

Of course this is all academic since I would never recommend that anyone who was not skilled and experienced in timber construction even consider such a task.

 

[schmism]

I'd try to select a bunch of 20' SYP 2x6's with the straightest grain and as free of knots and warping as I could find. I'd be very sure there were no loose knots, nor any knots greater than about 1" diameter or within about 1" of the edge of the board.

Your unlikely to find find SelectStructural (SS) material in a SPSS 2x6 and even if you did it would likely only be 18' and if you did find it, your looking at some wicked expensive material.

Lot easyer to use a single 30' lenght of LVL or TGI. the TGI is harder to find than the LVL. Most real lumber yards will stock 30' LVL.

 

[Tom_Veatch]

Yeah, like I said, an academic exercise of a hypothetical situation.

Egon's answer in the second post of this thread is still the best, most practical, and probably, least expensive option for a wooden beam. I'd still look long and hard at hanging a steel I-beam across that span. The weight is more than one man could handle without mechanical assistance, but that's the case for any beam across that span with that load capacity. And I suspect that, if the supporting structure were in place, placing the beam, wood or steel, could be arranged as part of the delivery service.

I don't know what steel is going for these days, but I wouldn't be too surprised to find the costs between steel and an engineered wood solution to be somewhat comparable. But, if wood is the desired solution, I would certainly hope it doesn't become a DIY project.

 

[shvl73]

I think your idea of a 2x6 beam might very well work. I worked for a company that manufactured gluelams, not as popular as they once were but still viable. If a person could fingerjoint the joints and stagger them, I'd keep them at least 24" apart, why not. The thing to remember is, no engineering on a homemade beam. Quality control is that of the maker. Buying a LVL, Paralam or Versalam from a yard will at least get him some backing through engineering, probably steel would as well.

 

[Tom_Veatch]

Fingerjointing the ends would remove the need for long, clear lumber and make the project more feasible; less expensive dollar wise, but more expensive time wise. Any reasonably well equipped hobbiest woodshop will have a router table or shaper and finger jointing router bits are available.

Lower graded lumber could be processed to remove major defects and full length laminations could be pieced together from shorter, clear stock. Individual stock lengths would still have to be enough to maintain good horizontal separation of joints in adjacent laminations.

Shorter stock also opens the possibility of jointing and thickness planing faying surfaces to remove cupping and improve fit which could simplify the clamping setup. Might need an extra layer or two to make up the thickness loss but 6" jointers are common and many or most woodshops have a thickness planer.

If we're fabricating in place, some thought will have to be given to the gluing/clamping process. If the individual pieces are short enough it might could be a one-man operation. Otherwise we'd need either a long open time glue or a crew of glue-smearers. But, one advantage of a long open time glue is that it might allow multiple laminations to be laid and clamped simultaneously and actually shorten construction time. A slow cure epoxy, maybe?

Too bad it's just an academic exercise. It might be fun.

 

[gordon21]

Keep in mind that there are two ways to go with engineered wood. The first is a glulam which is essentially a bunch of 2x4's or 2x6's laminated together in a stack (a tall stack of glued wood layers layed horizontally). The other is a microlam girder which is similar to a 2" thick piece of plywood about 14" tall. Many layers vertically oriented all glued together. Three microlams glued and bolted together to make a 6" thick girder will support thousands of pounds.

Either version can be made in 30-50' lengths. If I confused you, I can attach a drawing.

Microlams run $6.25 per foot for a 2" thick girder 14" high.

 

[Egon]

Have you given any thought to a movable engine hoist? It might be handier than a fixed point.