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04/12/2018, 07:46 PM | #1 |
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Calling all engineers!!
I'm well along with a build for my 300g in-wall tank. I'm about to start building the stand (out of wood) and need some engineering guidance.
My tank is 96" long 30" deep and 24" tall. the front of the tank will be sitting on 2x6 rails with 2x4 uprights every 16". Plenty of support up front, here's where I need the help of the engineers, for the back of the tank I want to have it completely open, which means the top rails are going to have to be pretty beefy. What do I need to carry the weight of the 300g and have very little (or within acceptable limits) deflection on that top beam? Thanks for reading.
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Jimmy MASVC President Dishes are done man! Current Tank Info: 300 in progress |
04/12/2018, 08:29 PM | #2 |
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Dang, 300g is alot of water weight. You might need more than just 2x4s up front to support that kind of weight.
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04/12/2018, 08:33 PM | #3 |
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Is the tank gonna hang back into that doorway?
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04/12/2018, 09:52 PM | #4 |
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No, It will be flush with the jamb.
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Jimmy MASVC President Dishes are done man! Current Tank Info: 300 in progress |
04/12/2018, 09:59 PM | #5 |
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this is where I'm at now, the stand will bolt right up to the wall into the 2x6s, which means the stand that I will build will only need to be 25.25" wide (the wall is 4.75" wide)
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Jimmy MASVC President Dishes are done man! Current Tank Info: 300 in progress |
04/12/2018, 10:40 PM | #6 | |
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I wouldn’t be worried about the front. 2x4’s at 16” oc is plenty strong. Think about load bearing walls which take much more weight than a fish tank. Each 2x4 here is only taking like 200-250 lbs. It’s gonna be tough to span 8’ in the back with little to no deflection using timber. Can you live with one midspan post? |
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04/13/2018, 06:28 AM | #7 | |
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he got 8 across the front. only half of that should able to hold up the whole tank as long as within reasonable height. as for the back. 2x8 across the 8" span should able to hold it up no problem.
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04/13/2018, 06:54 AM | #8 | |
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You’re saying a single 2x8 is ok to span the 8’ across the back? What are you basing this on? Did you check the deflection, moment, shear, etc... or are you just assuming it would work? |
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04/13/2018, 07:01 AM | #9 |
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What about a coated steel I-beam, or square tube? Then you could rest it on a 4x4 on each corner maybe?
...I am no engineer, just thinking out loud for alternate options
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04/13/2018, 07:31 AM | #10 | |
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i got 5E-4m deflection. i will call that 0.
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Dont let me know where u lived if u have a nice pair of clownfish in ur tank!^_^ Clown kidnaper^_^ Current Tank Info: 300DD, SM200/RD3,ATI 60-8X80+4X75, 2 Sea Sweep & 4X6105 & 6208 Last edited by ClownNut; 04/13/2018 at 07:42 AM. |
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04/13/2018, 07:51 AM | #11 | |
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Just to follow up now that I’m at work and can run some calcs. - assuming tank weighs 500 lbs empty - you’re looking at a distributed load on that back beam of ~188plf - using a single 2x8 spruce pine fir would yield .25” of deflection. - it is also overloaded in bending moment. - if you used double 2x8’s you could half the deflection (assuming you’d glue/screw them together well) - not sure about you, but I’m not comfortable with 1/8” deflection on a glass tank. I’d want 0” period (had a tank crack recently) This is over simplified analysis and assumes you’re putting load directly on the timber. Where really, in order for the timber to deflect, the glass has to deflect. I just wouldn’t want to put that kind of stress on the glass/joints personally. If it were me, I’d either build it all out of steel, or find a way to add midspan support. This is just my opinion. I’m by no means a timber design expert but I do come across it somewhat frequently as a Civil PE |
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04/13/2018, 08:20 AM | #12 | |
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Can you share your calculations? Applying a 2.6kn/m load (half will go to the front) to a 2.44 m long steel W8x10 will still yield a .5mm deflection. So something you are doing is just not right if you are coming up with 0... |
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04/13/2018, 08:33 AM | #13 | |
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PM you too, i want to see how do you comes up to your number.
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Dont let me know where u lived if u have a nice pair of clownfish in ur tank!^_^ Clown kidnaper^_^ Current Tank Info: 300DD, SM200/RD3,ATI 60-8X80+4X75, 2 Sea Sweep & 4X6105 & 6208 |
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04/13/2018, 09:44 AM | #14 | |
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What would you think if I ordered a 5"x8"x96" glue laminate? That should be able to hold up 2 or 3 of my tanks???? Just guessing of course.
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Jimmy MASVC President Dishes are done man! Current Tank Info: 300 in progress |
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04/13/2018, 09:58 AM | #15 | |
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I don’t have much experience with glue lams. I’m sure whoever you ordered one from could tell you the bending capacity though. |
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04/13/2018, 11:45 AM | #16 | |
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Sus and clown nut, thank you for your expertise,
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When it comes to bending capacity, educate me on what I need to know. At 96" will they just give me deflection at a certain a weight? or is there going to be a number associated with agiven type of laminate? And to make sure we are on the same page, (correct any of this that you see wrong) 300g of saltwater is roughly 2600 lbs and i'd agree with you that 500 lbs is a liberal estimate for the tank. total of 3100 lbs, half the weight held up by the front which means i'm concerned with a load of 1550 lbs that this beam has to hold (at a minimum).
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Jimmy MASVC President Dishes are done man! Current Tank Info: 300 in progress |
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04/13/2018, 11:53 AM | #17 | |
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If they could tell you the deflection based on the load of 194plf (1550 lbs/ 8ft) that would be great. I’m guessing though they will just give you a moment capacity. If you are able to get that, along with shear capacity, EI value, and allowable end reaction (with bearing length) then you can calculate the deflection and verify if it works or not. |
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04/13/2018, 11:56 AM | #18 |
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And to answer your second question, yes you are seeing that right. 2600 is probably a bit conservative but better to be on the conservative side
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04/13/2018, 12:22 PM | #19 |
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If you could find a beam with an EI value in the 270x10^6 that would equate to roughly a 1/16” deflection.
This value is similar to that of a double 2x10 spruce pine fir. |
04/13/2018, 01:12 PM | #20 |
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If you wanted to use a steel beam to save on the size of wooden beam, could you not bolt it to the wooden stand? and otherwise construct it out of wood?
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04/13/2018, 02:07 PM | #21 | |
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Jimmy MASVC President Dishes are done man! Current Tank Info: 300 in progress |
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04/13/2018, 02:14 PM | #22 |
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also keep in mind, because the pine is not isotropic. i dont know how much of the result can be trusted.
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Dont let me know where u lived if u have a nice pair of clownfish in ur tank!^_^ Clown kidnaper^_^ Current Tank Info: 300DD, SM200/RD3,ATI 60-8X80+4X75, 2 Sea Sweep & 4X6105 & 6208 |
04/13/2018, 02:20 PM | #23 |
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04/13/2018, 02:23 PM | #24 |
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04/13/2018, 10:49 PM | #25 |
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How much head room are u looking for? It looks like u built the wall around 42” tall, so if u use a double 2 X 10 it will leave u with about 32” to 32.5” of head room. If u want more then that then u may need to go with steel. U could also come in about 2’ from one end with a support, then u would only have a 6’ span & a double 2 X 8 would work & give u a little more head room.
I’m no engineer & I didn’t calculate to see if a double 2X10 would work, I was just using it as a example as far as how much head room u would have. I know I wouldn’t use anything less then that to span the entire 8’. |
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