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</DIV><H1>Metal Tank Rack</H1><DIV </a></DIV><DIV id=Qtextbox><P><STRONG>Author: annparisi</STRONG><BR><BR>I am about to build a metal rack to support 3 tiers of fish tanks. I would just like to know from some one with some experience in this whether I need 4 or 6 legs to support the weight. The rack will be constructed out of 1inchx1inch square galvanised steel with a 1.6mm wall thickness. Each tier will have to support 400L water + tank weights. It will be 5foot long x 2foot wide. Any help would be greatly appreciated.

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Regards Ann

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</P></DIV><H2>Replies »</H2><DIV id=Atextbox><P><STRONG>Author: Cichlid Boy</STRONG><BR><BR>I haven't built one, but I'd be going with 6 legs for that much weight (1200kg + ). That's the weight of a small-medium car!

</P></DIV><DIV id=Atextbox><P><STRONG>Author: kevsta</STRONG><BR><BR>I haven't built one either, but another option is to buy some dexion heavy duty pallet racking which should set you back around the high 400s.

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</P></DIV><DIV id=Atextbox><P><STRONG>Author: aurea23</STRONG><BR><BR>i have had built by my dad a 3 tier 5x 2 rack. We used 50x25 mm tube with a 2.5 - 3mm wall thichkess, It has 6 legs and will literally hold tonnes...

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Mike

</P></DIV><DIV id=Atextbox><P><STRONG>Author: hyperdive</STRONG><BR><BR>I'm currently running six tanks on 3 levels on a dexion pallet rack. four of the tanks are 4x2x18 and 2 are 4x2x14. It does it no problems, and the whole rack cost under $450 brand new, and you can dismantle it to move it in 5 minutes.

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<P><STRONG>Author: MagicaDiSpell</STRONG><BR><BR>I am not sure what a dexion pallet is, but if you are using something with legs, I would go for more legs rather than less. Another point to take into account is point pressure. I am no structural engineer, but when we built our last extension we had to make the decision to sell our tank system, because the point pressure would have been too much for our concrete slab, even though the total weight of the system (3000 l of water plus tanks etc) would have been ok.

</P></DIV><DIV id=Atextbox><P><STRONG>Author: chorrylan</STRONG><BR><BR>hi,

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I have built one but was working out what I was doing as I went

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Mine is built from 22x38mm square form steel in 1.6mm wall thickness.

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It's holding up perfectly for me using just 4 legs but I have smaller tanks (60 x 18 x 16 inches with around 270 litres of water each).

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I would recommend strongly against the 1-inch x 1-inch profile steel though and recommend you use something with a rectangular cross-section if you're considering running 5-foot lengths with no support in the middle. I have no idea of the engineering explanation but if you keep everything else constant a square cross-section is far easier to bend than rectangular cross-section (assuming of course that the pressure is applied against the narrow side only)

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I also built mine as a complete frame so theres's a complete shelf at the gound level to spread the weight around rather than literally standing on 4 leg-ends.

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I needed to do this as the floor is irregular (slate) but would probably do it even if I was putting it on a concrete slab.

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There's some shots of the rack here to help get this in context:

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www.planetchan.com/laurie...ish/tanks/

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ps: being a paranoid sorta person and beng worried that I might be pushing my luck having only 4 supporting legs I had the tank bases made in three pieces. The base is made of a 40-inch piece n the middle and two 10-inch pieces at either end. This theoretically gives 'em a teensy bit more capacity to cope with any bends. This more of an issue when lifting than when on the rack though... if your rack bends I doubt minor details like a multi-pane base is going to save you. It does have the advantage though that the weakest component, where the hole was drilled, is in a separate 10-inch pane.

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Laurie

</P></DIV><DIV id=Atextbox><P><STRONG>Author: Craig Douglas</STRONG><BR><BR>My problem is the 1"x1". I looked at metal stands and almost all commercial stands are 50x50x1.6.

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Craig.

</P></DIV><DIV id=Atextbox><P><STRONG>Author: c2105208</STRONG><BR><BR>I think some people often overestimate the load that can be taken on hollow sections....

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50x50SHS Grade 350 Steel (2.5mm thickness) will take a maximum axial load of 124kN at 1.0m effective length (that's straight from calculations in Australian Standards AS4100, simplified in AISC DCT's). For those not structurally inclined, basically that means that raw load on each leg of about 12.4Tonne! The real length of the leg will depend on the connection... If rigid joint (welded both ends to horizontal support 'beams') then 1.0m effective length will mean about 1.4m leg length. If bolted at top and bottom then about 1.2m leg length. Of course you wouldn't run it at 12.4 tonne since for glass tanks especially deflections are to be kept minimal... I'd say run maximum 3 tonne on each leg at 1m effective length with this size section. If you want to run a rack of several tanks high, where the leg length will be 1.8m effective length (round figures), the max load would be reduced to 78kN (around 7.8Tonne). So, run 2 tonne per leg max. Don't forget spacing issues...Depends on the size of the tanks. Can you be more specific? Do the maths

In any case I do not mind if you e-mail me to double check sizes and spans.

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Oh, and members subject to bending (the horizontal crossbeams between the leg for example) are a different kettle of fish totally, with different calculations to be done... And yes if you want to save money, rectangular sections are more economical than square sections when subject to bending if the load is on the narrow face. I won't go into details but it has to do with the amount of metal resisting the tensile and compressive forces in the top and bottom of the member respectively. You can get away with narrower width for members in bending if the section is deeper. Of course it would be better to just increase the size of the rectangular section - it would be stronger but less economical for the intended use.

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MagicDiSpell - The pressure would be too much for your concrete slab? Did you have very old concrete or...? Concrete can take enormous loads. The only possible problem with point loading is concrete 'creep strain', which is a continual long-term (we're talking years here) deformation (leading to cracking usually) under high loads. In any case, minimal specs for residential slabs is generally 20MPa grade, so even if you get dud stuff from the factory, 0.75 of this (statistical reason for this) would still mean about 15MPa. 15Mpa is 15x10^6N/sq.m which equates to about 15Tonne/square metre critical load. Again, you'd only ever want to run it safely (so you can sleep at nights

) at around 30-40% of this maximum however. Even with a point load they'd have to be of seriously small section to cause many problems.... Are you sure you were not told other reasons why the tanks were a no-go?

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Cheers

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Adam

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</P></DIV><DIV id=Atextbox><P><STRONG>Author: SeayTaing</STRONG><BR><BR>Okay!

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Seay

</P></DIV><DIV id=Atextbox><P><STRONG>Author: annparisi</STRONG><BR><BR>Thanks every one for all the advise. I think I will be going with the 6 leg option just to be sure.

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Ann

</P></DIV><DIV id=Atextbox><P><STRONG>Author: hyperdive</STRONG><BR><BR>Just to clarify about the dexion, it's basically pallet rack beams with 4 legs. Each beam is around 9 ft long and can take more than two tonne of weight without extra support. I have the three levels with a little under a tonne on each level. There is no extra legs and the beams do not bow at all. The racks come in 2ft or 3ft widths front to back (or close to) so you have 2 beams per level.

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</P></DIV><DIV id=Atextbox><P><STRONG>Author: approximate</STRONG><BR><BR>Hyperdive, do you mind telling me where you got the black pvc pipes from (as shown in the second picture)? Do you know if they come in smaller sizes? I was at Bunnings last weekend but couldn't find these 'pipes'.

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Can someone please post pictures of their centralised air-pump system if it's not too much hassle?

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Thanks.

</P></DIV><DIV id=Atextbox><P><STRONG>Author: hyperdive</STRONG><BR><BR>It's poly pipe, available from any irrigation, pump supply or pool supply place for next to nothing (about a dollar per meter for a medium sized pipe) the basic sizes are 1/2 inch, 3/4 inch, 1 inch, 1 1/2 inch etc up to a few inches.

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It moulds to shape when filled with hot water and you can screw connections on, and remove them later without having to cut the pipe, so it's better than pvc in my opinion. It is available in pretty much any size from 4mm and up.

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<P><STRONG>Author: syco120</STRONG><BR><BR>Hi there Ann , 6 x legs would be needed for your application given the tier requirements and based on the 5 foot length !!

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(dont consider any less)

..If you care to look back through the pages , i'm sure Phil from brissie , has pic's up of a similar set-up, you might like to take a look...and i think the spec's were included in that post ....Good luck....

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bob.

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Andy , Do those racks come in a brighter colour and how do you manage to work around all those pipes and cords and things...

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bob.

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</P></DIV><DIV id=Atextbox><P><STRONG>Author: hyperdive</STRONG><BR><BR>Unfortunately that was the only colour they came in at the time.

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The pipes are at the back of the tanks so there is no need to work back there 99% of the time.

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<P><STRONG>Author: danceswithdingoes</STRONG><BR><BR>Andy, how the heck do you actually get anything out of those tanks as they look to have only a few inches clearance

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</P></DIV><DIV id=Atextbox><P><STRONG>Author: syco120</STRONG><BR><BR>Cool Andy, but that 1 % would scare the crap outa me

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Otherwise that industrial pallet racking yer using , sounds

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cost effective and user friendly besides it has the option of hight variance from memory, But i have to ask how do you support the centre of the under tank from front to back, do you make something your self ???? Interesting !!! Also how do you find the movement seeing as its not welded ..

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Thanx ,

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bob.

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</P></DIV><DIV id=Atextbox><P><STRONG>Author: hyperdive</STRONG><BR><BR>no movement whatsoever - it's as solid as any welded stand I've ever seen.

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I have the tanks sitting on 16mm mdf for a little extra support, but it really doesn't need it. I've seen the racks with just foam underneath the tanks set up for years with no problems. I'm just a little paranoid.

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As for the height, unfortunately I didn't have too much ceiling height to work with, so space had to be minimum. The distance between the top of the tank and the tank above is actually the gap you can see plus the height of the orange beam. The only hassle is putting anything large into the bottom two tanks, but most stuff can be put in through the ends anyway. Other than that, the gap is big enough to get my arm into the tank so that's all I need. I really haven't had a problem with it.

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It was the price I paid for having three levels instead of two, but I guess it gets me another two tanks so I'm not complaining.

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<P><STRONG>Author: hyperdive</STRONG><BR><BR>I forgot to mention, there are actually no electrical leads at the back of the tanks. The black things you can see there are panduit straps (zip ties). The powerboard setup has been improved so there is no chance of water getting onto it.

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</P></DIV><DIV id=Atextbox><P><STRONG>Author: Lee Miller</STRONG><BR><BR>Hi Ann,

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You said;

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Thanks every one for all the advice. I think I will be going with the 6 leg option just to be sure."

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You haven't said whether or not you will be upsizing from the 25 x 25 x 1.6 RHS. I'll assume that you're not. IMHO that is WAAAAY too small. It's not so much the load on the verticals that will give you grief, as the distributed load on the horizontals and the shear force on the connections (between the horizontals and the verticals).

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There has been some very good advice given on this topic (even if some was too technical for the average fish keeper

). Steel and glass flex at greatly different rates (modulus of elasticity) therefore an overloaded steel beam will flex more than the tank it supports leaving the middle of the tank unsupported - then something's gotta give - usually it's the front of the tank separating from the sides with water (and fish) all over the floor. The deeper the horizontal beam, the less flexing occurs. Personally I'd go for a 50mm minimum.

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Other considerations - 1.6mm steel won't hold a very strong weld and it won't take long - in a fish tank situation - for rust to weaken the structure.

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Just my opinion - good luck.

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PS: Can someone tell me how to do that quote thing?

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Thanks.

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