Warren

Hi All, The HBAS is having a tank crawl tomorrow, starting at 10:30am from the National Aquarium.

Just a reminder to all clubs - you need to advise us in writing who your delegates are prior to the meeting.

Ah, so you'll miss the committee meeting then...

Not 100% sure about this but I'm fairly sure fish are not as susceptible to mercury poisoning as humans. I believe fish have a mechanism for binding many heavy metals into their system without becoming toxic. This is why it's bad to eat shark from the fish & chip shop as the accumulated mercury is much higher in the animals at the end of the food chain. Maybe they are effected by high levels of heavy metals but a heater will not be the cause.

I can understand what's going on in your head. Even with all the calcs to support a tank or stand being good there's always something you might have overlooked or done wrong or even assembly errors etc. The first time you fill your system you have this dreaded feeling of what if... Then for days you worry if it's going to be ok. Calcs and experience don't change this, I get it every time.

Yes, apologies if it's out of hand - just don't want your tank to break...

This is nothing to do with ego, it's about making sure a tank does not broken. The calculations were based on less than 1% surface area having support on the stand in question. Even with poly, there would be only 4 points of contact where the 4 middle legs join the frame. When the middle legs were welded in it bent the top part of the frame away from supporting the tank. As both the tank and frame are hard and will not flex enough to distribute the load over any more than just the 4 points, almost all the load is on these points or distributed near them with the help of the poly having some crush. After the poly is crushed or deformed most of the weight is still on the 4 load bearing points. Given the actual contact area bearing the load is very small compared to the surface area of the bottom of the tank, 1% was considered a reasonable starting point. Even if it was 10% the load on the glass is still too high. The tank is 1500 x 700mm so 1050000mm². 1% = 10500mm² or 102 x 102mm of total contact area. There may be a little more than 100 x 100mm of contact area but the pressure will not be even and still mostly concentrated near the 4 middle legs. 10% gives 105000mm² or 324 x 324mm contact area. It's not possible this much area is available given the size of the frame material and elasticity of the material it's made from.

The statement was made because you would not listen and it seemed futile to try to help - giving up was the only option. If you looked at the figures and made adjustments of factors of 2,5 or 10 you would still see the glass was under too much stress. The base figures are simply a place to start - assumptions to get things going. Fairly standard what-if scenarios... Sorry if you've taken it personally, was not the intention.

Hey, it's not abusive, I'm simply stating you seem to know more than someone who can do the calculations (even if they were stuffed-up the first time...) and has many years experience.

I personally think it will be ok. If you put quite a bit on every metal surface before putting down the ply so it oozes out plenty once fitted you can then place the tank on the ply to it conforms to the same flatness as the tank. You will likely need some small wedges around the edges of the ply in a few places to push low areas upwards. At the corners the ply will tend to droop away from the surface of the glass. If it happens, push a wedge into the glue between the wood and steel until the wood comes up at touches the tank. No-more-nails takes quite a while to go hard so maybe wait a week before removing the tank and adding the poly before filling. I've done this many times on uneven stands and on tanks much bigger than this one. If a little time is taken checking good even contact all the way round you'll end up with and very flat base.

I give up, you seem know everything you need to know about welding and stress calculation. As I don't know everything there is to know, I will not comment further. In my 25 years experience of welding, structural design and fabrication I regularly learn new things...

Oops, did get it out by a factor of 100 (I hate unit conversions!!), so only 9kg/mm² or 90n/mm² :oops: However, this is still too high by a considerable amount when you consider the maximum loading for glass is approx 19.2n/mm². Hope you understand the basic laws of physics and the risk you are taking with your tank. I assumed a certain cross-section and multiplied it by 10 and worked with this. The calculations are based on 625mm² of contact area or a total of 25x25mm which you are very unlikely to actually achieve with this stand. The earlier figure is based on poly partially spreading the load over a larger area. Even so, at 20n/mm² it's still higher than the strength of the glass... Can't understand why you'd want to take this risk. When you compare these loadings with what you'd have if the supporting surface was flat you can see why there is concern. The loadings on a properly supported tank drop from 90n/mm² to 0.05n/mm² or 1680 times less. When you can offer something to back up your claims please comment further.

This is actually a very good option. If you have a decent saw you could make long thin wedges as packers and then use the no more nails to take up the last very small gaps... Alternatively you could try planing the wood to create hollows where the high-points are.

Well, you can try if you want but a quick type on the calculator shows you'll likely get in excess of 2000N/mm² or 200kg per square mm of force on the section of the tank at the high points and nothing anywhere else. This assumes a fairly even spread-out of the load due to poly placed under the high points but much more than the glass is good for. If you really want to risk breakage now or any time in the future, go for it. Worst case, if the poly does very little to help with the high points, you'll get over 9000N/mm² or 900kg per square mm - death to the glass and some. I really think advice and an approach like this should be taken only if you don't care if your tank breaks and only if you don't want to sleep well at night...

Please show your calculations that justify your statement...

It's not going to sag ever without being forcibly modified. 4mm is a lot to take up. What's happened is when the two middle legs were welded to the underside of the top full-length member, the welds have shrunk as they cooled making the bottom side of the top runner shorter than the top side. This causes it to bow upwards. It would be possible to bend it down but it will tend to bend unevenly. The easiest way is to run a hacksaw most of the way through the top runner at the top of each middle leg so the stand can sit flat again at these points. You can then tig weld up the side of the cut to strengthen it. Do not tig weld the top or it will bow in the opposite direction and be hollow instead. Then you can use the no-more-nails option to take up any small errors that are left.

Not so sure about that. I think you'll find it took years of dedicated effort to get that way in the first place...

Yes, really was their garage. Have been there a few times and can vouch for the before pictures. I think I need to see the afterwards to be sure it's real and not a clever photoshop edit... Will report back after conference if it really is like this...

And more to come... Back on topic please.

Install Ubuntu and run Vista as a virtual machine...

You obviously get a much better deal than we do... We'd pay that from Napier to Palmy. Would hate to think what it would cost to Chch... However, it would be guaranteed to arrive safely.

Yeah Fliway are very good but do you need that arm and leg? They're also the most expensive by a factor of at least 2... You could easily buy two tanks the the freight cost.

You are correct, if one end is showing as level and the other isn't then there is a twist somewhere in the stand. It's unlikely to be coming from the floor as this stand looks easily to be stiff enough to support it's own weight without twisting due to the floor. Maybe the correct term to use is flat.

I recently shipped a tank from Napier to Auckland with Mainfreight. The company I work for has found them to be the best for commercial... It cost about $360 to ship a crate 2.6m x 1.7m x 0.95m and weighed 800kg all packed. Smaller tanks would cost considerably less. I just packed it pretty well with a lot of padding (75mm thick of poly-bubble) and labeled it up as a glass aquarium - please don't break me. No carrier I talked to will insure a glass tank though. I did try Conroys but they were one of the most expensive and they eventually refused anyway as it was just too big.

Not really but it's good learning example. Simple putting it there is a breach of the guidelines. However, I've made the statement now so it can stay for everyone else to learn from. I'll trust you'll be honest and not include anyone who contacts you from the site with respect to this. The only way you can form a buying group is through telephone and email contact outside this site. You may not use the email link button either as they are there as a privilege and are not a prospecting tool...