Critique my cheap aquarium rack please

[1Der9_3hy]

I plan on using CMU's (also known as cinder blocks, which =16"x8"x8" give or take a fraction of an inch) for the uprights. There will be four uprights (only 2 are pictured for simplicity and because i did not want to sketch a side view ). Each block costs $0.97.

The horizontal plane will be made of either 2x4 or 2x6 white pine lumber. Not certain yet, but i may have to build some sort of "deck" for the 54" span to eliminate the chance of deflection.

Anyone seen something like this before? Or done something like this? I can fit 7 "15" gallon tanks (24x12x12) this way, and it only takes up 19" more than what i am using now to fit 3 of the same tanks.

It should be under $60 to assemble the whole thing, so its very cheap to make. Ive used a setup like this before to hold two 50 gallon rubbermades (troughs if your not familiar with the brand) that were filled with water & aquatic plants. It was rock solid for years.

 

[cilyjr]

it will hold the weight. when you mount the rails you are planning on placing them so the thinner part is holding the weight.. ie the tanks need to rest on the 1.5 edge of a 2x4

 

[pickupman66]

I was thinking the same thing and cilyjr. If it were me, I would build a rectangular frame from the 2x4's for the tank to sit on. if you simply lay a 2x6 or 2x4 on its side side, it will bow severly. you want them upright on their 1 3/4" edge so they have better structural integrity. without that type of shelf, I would be hesitant to sit anything of weight on it, including my fat butt.

 

[cdness]

With the 2X4(6) on the flat side it will deflect WAY too much. You will need to stand it up on end and possibly just build a shelf for the tanks to keep them up.

I am attempting to figure out why the blocks and not just building with lumber?

 

[bct15]

Well I dont know how much deflection your 2x4 will experience without an analysis, but I do know that the orientation of your 2x4 is important. Wood is strongest when the load is parallel to the grains of the wood. They are cut to resist fracture (and support a load) along a certain axis and remember the fracture occurs orthogonal to the direction of loading, you want your grains oriented in the direction to resist load. Fracture prefers to follow a weakened path such as grain boundaries and if the grain boundaries are orthogonal to the load plane then the wood will fracture at a much lower stress then if it were oriented properly.

Also do not place the tank on the small side of the 2x4, stress is defined as load/area. If you have the load applied over a smaller area you will have a larger stress, which you do not want. Without knowing the material properties of the materials I can not say for certain if that will work, but I do know that the anisotropic behavior of wood will dictate your chances of success. I believe typically 2x4s are cut to support a load in the longitudinal direction.

 

[1Der9_3hy]

it will hold the weight. when you mount the rails you are planning on placing them so the thinner part is holding the weight.. ie the tanks need to rest on the 1.5 edge of a 2x4

I was thinking the same thing and cilyjr. If it were me, I would build a rectangular frame from the 2x4's for the tank to sit on. if you simply lay a 2x6 or 2x4 on its side side, it will bow severly. you want them upright on their 1 3/4" edge so they have better structural integrity. without that type of shelf, I would be hesitant to sit anything of weight on it, including my fat butt.

With the 2X4(6) on the flat side it will deflect WAY too much. You will need to stand it up on end and possibly just build a shelf for the tanks to keep them up.

I am attempting to figure out why the blocks and not just building with lumber?

Would you guys trust four 2x4(6) on there side to support three 15 gallons? I guess the nice thing about this setup is i can try it and if it bows i can tear it apart easily and change it.

As for the top, i plan on making a deck of 2x4's laid on end with some ply wood to tie it together and create a flat surface for the tanks.

Also the legs are not wood because A) i need to be able to move this entire setup easily & B) an assembled stand of this size wont fit through the stairway/door at the bottom of the stairs without removing a wall.

Well I dont know how much deflection your 2x4 will experience without an analysis, but I do know that the orientation of your 2x4 is important. Wood is strongest when the load is parallel to the grains of the wood. They are cut to resist fracture (and support a load) along a certain axis and remember the fracture occurs orthogonal to the direction of loading, you want your grains oriented in the direction to resist load. Fracture prefers to follow a weakened path such as grain boundaries and if the grain boundaries are orthogonal to the load plane then the wood will fracture at a much lower stress then if it were oriented properly.

Also do not place the tank on the small side of the 2x4, stress is defined as load/area. If you have the load applied over a smaller area you will have a larger stress, which you do not want. Without knowing the material properties of the materials I can not say for certain if that will work, but I do know that the anisotropic behavior of wood will dictate your chances of success. I believe typically 2x4s are cut to support a load in the longitudinal direction.

Thanks for the DETAILED response I appreciate it.

 

[bct15]

As I stated, you will want the 2x4 supporting the tank on the wideside to reduce the amount of stress imparted into the 2x4. Laying some plywood across the 2x4s will significantly increase the load bearing surface area, which help out a lot when considering the load. Also, a third 2x4 will not hurt anything. I think you should have a piece of plywood on both levels if possible, bit saying that this will work but adding plywood will help.

 

[1Der9_3hy]

Thanks again. The bottom level will have 4 2x's total (two on the front legs and two on the rear legs). Ill add ply wood and go from there.

 

[cilyjr]

this is how a 2x4 or 2x6 is set to best support weight you oviously dont need the cross bracing... i personally would not use a 2x6 because you dont need too a 2x4 will do the job.

 

[1Der9_3hy]

this is how a 2x4 or 2x6 is set to best support weight you oviously dont need the cross bracing... i personally would not use a 2x6 because you dont need too a 2x4 will do the job.
http://www.homeadditionplus.com/images/home_pics/Floor_Joist_Cross_Bracing.jpg[/IM vG][/QUOTE]

Thats the plan (minus the braces) :D I might even eliminate the bottom row and make the whole thing one level. I use it to grow some nice live bearers that i trade into stores for supplies and frags. So using a little space/energy as possible is what im shooting for.

 

[bct15]

Those cross bars actually put a preload on the 2x4 in the grain's radial direction helping to relieve the stress experienced by the thinner face. In your case if you orient the 2x4s like that the cross bars would serve a purpose.

 

[Reef Breeders Verified Sponsor]

Dont use cinder blocks, the whole thing will collapse if the boards bow. Just build a stand, I built one out of 2x4 s and osb for $35, and it is rock solid.

 

[cilyjr]

i have actually had a 39 on nothing but cinder blocks before. it was fine for years though i would not recommend this

 

[1Der9_3hy]

Those cross bars actually put a preload on the 2x4 in the grain's radial direction helping to relieve the stress experienced by the thinner face. In your case if you orient the 2x4s like that the cross bars would serve a purpose.

Dont use cinder blocks, the whole thing will collapse if the boards bow. Just build a stand, I built one out of 2x4 s and osb for $35, and it is rock solid.

I appreciate the concern guys, i do But I have to fall back on my experience here and i know as long the horizontal boards are built properly this setup is rock solid. Its ugly, but it can be tore apart and put back together faster than you can drain 4 tanks. I am remodeling/adding onto my house, so this aspect is very important to me.

i have actually had a 39 on nothing but cinder blocks before. it was fine for years though i would not recommend this

This ^ I will have to grab a pic, i have 10 50 gallon rubber maids supported on nothing but cinders and 2x4's, going on 10 years now that i think about it. God im getting old.