Let's talk about structural support...

[Chad]

I looked at LVL a bit, I think it may be a viable alternative... I like that I can get it in specific sizes and it is not susceptible to varaitions in material properties caused by knots, grain directions and stuff like that... I also think that the LVL material would take glue a bit better to make a T joint.

 

Chris, I dont think you are seeing in incorrectly... I battled with myself on the 45s initially and I am sure there are improvements to be made... the one that you suggest would probably be easier for me to model anyway I think my next step is to create a model... I need a math day

 

How do you all think I should model the tank itself?

[ctenophore]

That sounds like a pretty cool idea... I think I will play around with it some and see if I can come up with anything that catches me. I know this can be done with steel... I am pretty sure all that would need to be done is to have a steel plate, put a frame on one side to support the tank at the edges and attach it to the pedestal on the opposite side. However, I would prefer to do it with wood so I can make it. In the end, if I cant make numbers come out, I will switch and have it built.

As CH mentioned above, you could do this same idea in CMU + LVL. I've used LVLs before when building a stand several years ago; I did a 7' span holding up a 235gal, unmeasurable deflection. They're pretty stiff, so I suspect with proper sizing you could center support them and get the look you want.

[CHUBAKAH]

This thread makes me LOL.

[ctenophore]

What's funny, Mark?

[Chad]

So me being the geek that I am and having a few extra hours to kill on a plane yesterday while heading west for a couple weeks, I modeled the design I had up earlier in a FEA program. Jury is in and wood is a rasonable thing to make this stand out of... with much higher of a safety factor than I would have guessed... ~7 with 4000 lbs as an input force spread evenly across the bottom glass.

 

Here is a picture of the model with the applied force:

 

 

And here is a picture of the stress analysis. I changed the scale on the color enough to be able to see if there are any issues that would need to be dealt with in the stand... as it turns out, it looks ok. The red in the tank area is due to the changed scale and not unacceptable stresses. Just some low loevel stresses in the vertical supports, but nothing that I am at all worried about

 

 

More to come, while I move forward with my design.

Edited October 7, 2010 by Chad

[kingfish]

For the stand you need a structural engineer and not a mechanical engineer. Mechanical engineers deal mostly with HVAC and plumbing type stuff.

 

The stand is very doable, you will just need to make sure the horizontal plate is stiff enough or braced with a frame so it doesn't flex any. How far in are you thinking of setting the side panels?

 

 

Really just being sarcastic. Any engineer that can recall strength of material can perform the anaylsis. You can use stress strain calculation to design the stand or a residentail structural and framing book to get the formulas. I'm put together a speadsheet for my tank stand design. I got tired of using a calculator. If you can open the attached PDF you can see what I have done. You can get a copy of the spreadsheet if you want to plug in your number and I can check them if you don't understand. I tried to make the input simple as possible.

 

For example: Based on my input, I can use either 2 X 6 or 2 X 8 for my horizontial members. FYI: I plan on post the detailing of efforts and project as I get further along. All structural components have but cut now I am in the process of assembling.

Aquarium Stand Calculations for 210 gallon tank.pdf

[kingfish]

So me being the geek that I am and having a few extra hours to kill on a plane yesterday while heading west for a couple weeks, I modeled the design I had up earlier in a FEA program. Jury is in and wood is a rasonable thing to make this stand out of... with much higher of a safety factor than I would have guessed... ~7 with 4000 lbs as an input force spread evenly across the bottom glass.

 

Here is a picture of the model with the applied force:

 

 

And here is a picture of the stress analysis. I changed the scale on the color enough to be able to see if there are any issues that would need to be dealt with in the stand... as it turns out, it looks ok. The red in the tank area is due to the changed scale and not unacceptable stresses. Just some low loevel stresses in the vertical supports, but nothing that I am at all worried about

 

 

More to come, while I move forward with my design.

 

I'm curious, what's your distributed load in psi or lb/in? Have you already identified the stress location in the horizontial members. I expect to see higher stress along the very center of the top and bottom horizontal members. Leg compression or bulking was Negligible based on 2-d calculations. Why is the stress concentrated to what seems like one corner? Can I see a front view and top view so I can have a better look at your analysis? Nice work what software are you using?

Edited October 7, 2010 by kingfish

[Chad]

I'm curious, what's your distributed load in psi or lb/in? Have you already identified the stress location in the horizontial members. I expect to see higher stress along the very center of the top and bottom horizontal members. Leg compression or bulking was Negligible based on 2-d calculations. Why is the stress concentrated to what seems like one corner? Can I see a front view and top view so I can have a better look at your analysis? Nice work what software are you using?

 

A few more minutes before I go and try to get lost in the woods for a week...

 

Thanks, I am using the FEA module in Autodesk Inventor. I found out that I could get the entire Inventor Pro series through my alma mater for <$200, so I couldnt pass up the opportunity to play with it.

 

The distributed load was rounded to 2 psi (59*35 area with 4000 lb water weight, more than would actually be in an ~250g tank).

 

I also expected more stress in the horizontal members, I think the difference is that the glass is significantly stiffer, so after a very small amount of load is placed on the horizontal members, it displaces out of the way and the load path shifts to the vertical members which are waaayyy below their limits (I think when I did the 2d calc, a 2x4 is good for up to ~10,000 pounds in compression). What do you think about this theory?

 

Here are the pics you asked for, the top view is not very useful because the view is obscurred by the glass keep in mind the scale of the color. Also, I changed it to contour color change to call out the areas of higher (still low) stress in the vertical members (the four circles in the center are the applied load)

 

 

 

Leaving right now for a week, will be next week!