give me some feedback

[crazy_cavi]

well im finally done renos to the living room of my new house and i want to set up my
150g tank 24x48 base. originally i had forseen using 6 4x4 legs between 2 4x4 rectangle frames but now i think 4 legs will do anyone have anything they would like to add??

 

[maxumis]

I wouldn't regard myself as an expert, but I would like you to know that mathematicly; the more legs the better. It's the distance between supports on the load bearing beam that will kill a stand. I would feel a lot more combfortable with 8 2x4 legs than just 4 4x4s...

just me 2c

 

[yourmylunch]

technically one 4x4 is enogh to hold up a 55 gal tanks weight

4 is fine as long as you watch out for lateral movement

 

[maxumis]

I agree that one 4x4 could probably hold up a 55G. We grossly under estimate the compression strength of our materials, but the issue is transferring the weight to the legs without to much deflection in the beams that distribute the weight. After running a set of calculations on my "to be" stand that will need to hold a 300USG tank I get a 0.1mm deflection on my front beam. Where as the same set of calculations on a 4 legged 2 joist centred 66" stand carrying 350kg/m will make your 4x4 beam deflect 6mm.

If you think it's okay for your stand to potentially giveaway 1/4" under the middle of your tank then go for it. If not, get some joists supported by legs in there.

 

[CHOMPERS]

technically one 4x4 is enogh to hold up a 55 gal tanks weight

4 is fine as long as you watch out for lateral movement

Not long ago, I posted a thread about lateral forces and it turned out to be a moron mating call. I am always happy to know when someone understands that straight down is not the only force you will run into.

 

[CHOMPERS]

maxumis, I just gotta know...civil, mechanical, or aerospace?

Again, welcome aboard.
Ron

 

[crazy_cavi]

the tank is a 150g not a 55g i put in the 5th and sixth leg all of the 4x4s are screwed in with 45* chunx of 4x4 and they are between 2 frames. i dont know how the prefab stand was suppose to work the thickest wood on it was 5/8 and it was all put together with finishing nails and glue . and it is supported laterally with 2x4 construction studs sorry about the long wait in replying its just that i thought this post got forgotten because i checked it a day after and it was half way down the page already but neway thx

 

[maxumis]

Sorry to disappoint you Chompers, but I'm a Computer Systems Engineer. I'm just good old fashioned curious. Civil: I've build a couple of fish tanks and I've mixed cement for my DIY backgrounds . Mechanical: I used to buy scrap motorcycles and fix them up (if that counts) I gave it up after I had a crash. Aerospace: I've designed and built 2 kite surfing kites; one 8sqr m and one 16 sqr m. Gave that up after I realised that I'm better at building stuff than riding them . You can’t ride or crash a fish tank... Once I find an interest, I learn as much about it as I can. Family and friends hate it, I love it.

C_C, you won't be sorry about those extra legs. As I've stated before, we really under estimate the compression strength of the lumber we use. With the right construction techniques you can support massive loads with relatively weak materials. We have a bridge made of glass in one of our local malls. People who walk across that bridge believe it will hold. They don't even consider that whilst still on the bridge, other people will walk across it too!. They don't consider that resonant tremors created by the steps of themselves and others using the bridge may cause it to fail... I look at that bridge and think; it's made of a steel frame and GLASS!!! Point being with the right construction technique you can build a bridge made of glass.

The strength of lumber lies in its compression strength. So when designing your stand, try to have as much lumber on top of lumber and rely as little as possible on screws and nails to carry load. Notching your legs as below makes for probably the best technique of all.

Hope this helps.

 

[soggysandwich]

^^that is what im doing when i make my stand. notching the legs like that

 

[Potts050]

I agree that one 4x4 could probably hold up a 55G. We grossly under estimate the compression strength of our materials, but the issue is transferring the weight to the legs without to much deflection in the beams that distribute the weight. After running a set of calculations on my "to be" stand that will need to hold a 300USG tank I get a 0.1mm deflection on my front beam. Where as the same set of calculations on a 4 legged 2 joist centred 66" stand carrying 350kg/m will make your 4x4 beam deflect 6mm.

If you think it's okay for your stand to potentially giveaway 1/4" under the middle of your tank then go for it. If not, get some joists supported by legs in there.

Check this out...


*** 30psf Live Load, Douglass Fir/Larch #2 Fb=1450 E=1.7mil.psi
(Deflection = 1/360)
o.c.
Spacing 2x6 2x8 2x10 2x12
12" 12' 0" 15'10" 20' 3" 24' 8"
16" 10'11" 14' 5" 18' 5" 22' 5"
24" 9' 7" 12' 7" 16' 1" 19' 7"

Simply supported truss deflections are easier to calculate with more reliable results. If you want to break up a span with an additional leg ensure that the load is born but not fastened to the leg to allow expansion and contraction with changing temperature and humidity. An inch of high density foam between the tank bottom and the stand will help to offset the deflection.

I'm more in favour of using more on center trusses for a longer span than using center support. Make sure that you allow a minimum of 4 sq" bearing area on your trusses for spans greater that 48". This may require using a top plate, or a 4"X4" rather than dimensional lumber on edge.