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10/20/2017 1:01:18 AM
9/22/2017 12:11:25 AM
Posted: 8/17/2005 10:25:58 AM EDT
Hey all,
been trying to find some info for a while to no avail. I need an I-Beam (or Box, or C Track or X) something, to span 20 Feet, be Aluminum (light weight) and support about 500 lbs in the middle.

I am hoping for something that some sort of slider can attach to, like X and Box for sailboat travellers, but I-Beam will work fine. needs to be fairly light so two guys can lift it to head-height.

I'm open to suggestions, can't find weight capacities of beams anywhere.

Thanks,
Mister T
Link Posted: 8/17/2005 10:27:48 AM EDT
and this is going in the bedroom...?
Link Posted: 8/17/2005 10:30:08 AM EDT
[Last Edit: 8/17/2005 10:32:05 AM EDT by Bob1984]
The best I could find is Aluminum I-Beams Search Page Not sure how useful this will be to you. What you want are load tables, and if you're looking at a custom or irregular sized beam, you'll need someone who can handle doing the calculus that the load tables are based on. The only load tables I have access to personally are for residential construction stuff, not what you're looking for.
Link Posted: 8/17/2005 10:33:04 AM EDT

Originally Posted By Merrell:
and this is going in the bedroom...?




Gotta support the gf. He likes 'em a bit large.
Link Posted: 8/17/2005 10:33:35 AM EDT
What is your criteria for "support"?

No yeilding? No more than a given deflection?

Link Posted: 8/17/2005 10:37:27 AM EDT
When you say support Is 500lb the max load or the working load ?
Link Posted: 8/17/2005 10:38:03 AM EDT
point force or evenly distributed load?

Finally, some real work
Link Posted: 8/17/2005 10:39:20 AM EDT
I can give you the specs you need, but I need to know if this is max load or work load.
Link Posted: 8/17/2005 10:39:45 AM EDT
I install boatlifts. i need something to span across the slip and support (deflection doesn't really matter, just don't want it to be bending in half or wobbly) the bunks that the boat sits on. usually these bunks are 18 Lbs/ft 8" galvanized and about 20 ft long and have a pressure treated 6x6 on top. there is two of them, and i would guess that the aluminum I beam would have to support 1/2 of that load ( normally supported by a 6x6 or 6x8 galv I Beam, but needs to be replaced. I need the Aluminum beam to temporarily support this weight while i pull my boat under and remove the old galvanized beam and put in a new one, then drop the bunks back on top.

Thanks,
T
Link Posted: 8/17/2005 10:40:49 AM EDT
guessing this will be a "working load", that may vary in weight and may be moving somewhat with the other beam hanging by cables...

T
Link Posted: 8/17/2005 10:45:46 AM EDT
I was thinking something like 5x6" ibeam would do it, at least .250" thickness

Also, would this need to be anchored down on each end in order to support the weight? i was thinking maybe have some tabs welded on and just run a 5/8" stainless lag bolt into the top of each piling to keep it from shifting

T
Link Posted: 8/17/2005 10:49:21 AM EDT

Originally Posted By Mister_T:
I install boatlifts. i need something to span across the slip and support (deflection doesn't really matter, just don't want it to be bending in half or wobbly) the bunks that the boat sits on. usually these bunks are 18 Lbs/ft 8" galvanized and about 20 ft long and have a pressure treated 6x6 on top. there is two of them, and i would guess that the aluminum I beam would have to support 1/2 of that load ( normally supported by a 6x6 or 6x8 galv I Beam, but needs to be replaced. I need the Aluminum beam to temporarily support this weight while i pull my boat under and remove the old galvanized beam and put in a new one, then drop the bunks back on top.

Thanks,
T



If this is temporary then get you a W8X18. That beam has a 2 3/4" flange which would be plenty strong for the weight you will have on it and the span, it will cost 1/3 the price of aluminum.
Link Posted: 8/17/2005 10:51:04 AM EDT

Originally Posted By nwatson99:

Originally Posted By Mister_T:
I install boatlifts. i need something to span across the slip and support (deflection doesn't really matter, just don't want it to be bending in half or wobbly) the bunks that the boat sits on. usually these bunks are 18 Lbs/ft 8" galvanized and about 20 ft long and have a pressure treated 6x6 on top. there is two of them, and i would guess that the aluminum I beam would have to support 1/2 of that load ( normally supported by a 6x6 or 6x8 galv I Beam, but needs to be replaced. I need the Aluminum beam to temporarily support this weight while i pull my boat under and remove the old galvanized beam and put in a new one, then drop the bunks back on top.

Thanks,
T



If this is temporary then get you a W8X18. That beam has a 2 3/4" flange which would be plenty strong for the weight you will have on it and the span, it will cost 1/3 the price of aluminum.



A W6X15 would work, but for the few extra bucks it is wiser to go with the better of the two.
Link Posted: 8/17/2005 10:53:46 AM EDT
what would the weight be approximately? me and one other guy have to lift this often over our heads (only done twice per job though, thankfully)


T
Link Posted: 8/17/2005 10:56:18 AM EDT
W8x18 is 18 lbs per foot, W6x15 is 15 lbs per foot.
Link Posted: 8/17/2005 10:59:43 AM EDT
Oh.... well shit. that is what i'm replacing.... the beams i'm replacing are 15 or 18 lb/ft beams, and are heavy as hell... i need something really light weight.

T
Link Posted: 8/17/2005 11:01:21 AM EDT

Originally Posted By comp1911:
W8x18 is 18 lbs per foot, W6x15 is 15 lbs per foot.




You would almost think they planned it that way................................
Link Posted: 8/17/2005 11:09:08 AM EDT
Here you go. You'll be fine with the 5x6x0.25

Link Posted: 8/17/2005 11:43:04 AM EDT
[Last Edit: 8/17/2005 11:44:38 AM EDT by chuckhammer]
Assuming it is simply supported on both ends (not welded, bolted, or clamped down), the max moment load in the bean will be:
500 lb * 20 ft * 12 in/ft / 2 = Mmax = 60,000 in-lb

The max bending stress for the smallest aluminum I-beam I can find (W3x2):
60,000 in-lb * 1.5 in / 2.71 in^4 = Smax = 33,210 psi

The yield strength of 6061-T6 aluminum alloy is 40,000 psi at room temperature.

A 6061-T6 aluminum W3x2 beam will give you a safety margin of 1.2 (20% extra strength) for a 500-lb load in the center of a 20' span.

Figure you'll want 6" or so extra on each end of the span, so 21' of this beam will weigh only 42 lbs. I think you and your buddy can handle that.
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