Also the front back & side top & botom rails need to be double/triple is will be ply
I still say use lumber & cover w/ply
I still say use lumber & cover w/ply
Planning to build this
- Thread starter maxumis
- Start date
Mmmm, alot of worries on the stand...
I did the suggested changes to the design, and I must admit, it looks alot stronger now...
I'm not really worried about the middle "segmented" beam; it's function in this design is only to help spread the load to the load beering pionts. It's only in the design for weight distribution.
As for adding "diagonals". I'll have to see what is left over after everything is cut. There aint much left of 3 boards with the current design.
Which plays onto the budget... any aditional bracings from here on will meen purchasing an extra board.
I did my summs on a 2x4/ply stand a while back, and at that stage the 2x4s added up to the same price as 3 boards of ply; plus I would have had to then still get Ply... So that threw me into this design. 2x4s (38mmx114mm as their known here) are reletively expensive for some reason...
The tank and stand are 2 seperate entities. There not one unit. I'm young and will deffenatly still move house a couple of times.
I was wondering if anyone was formiliar with calculating deflection of a beam under load?
The reason I'm asking is, I was hoping someone could check my numbers; I'm getting 0.1mm max deflection on the front beam (dual 100mm x 18mm x 2440mm thus actually action as a singel 100mm x 36mm x 2440mm beam) with a uniform load of 1200kg/m(note this is the weight of the entire tank. It should actually be 600kg/m since the back of the stand will carry its share of the weight as well). Just for interest sake, I'm getting 2,3mm max deflection on the stand in the Forum stickey.
I did the suggested changes to the design, and I must admit, it looks alot stronger now...
I'm not really worried about the middle "segmented" beam; it's function in this design is only to help spread the load to the load beering pionts. It's only in the design for weight distribution.
As for adding "diagonals". I'll have to see what is left over after everything is cut. There aint much left of 3 boards with the current design.
Which plays onto the budget... any aditional bracings from here on will meen purchasing an extra board.
I did my summs on a 2x4/ply stand a while back, and at that stage the 2x4s added up to the same price as 3 boards of ply; plus I would have had to then still get Ply... So that threw me into this design. 2x4s (38mmx114mm as their known here) are reletively expensive for some reason...
The tank and stand are 2 seperate entities. There not one unit. I'm young and will deffenatly still move house a couple of times.
I was wondering if anyone was formiliar with calculating deflection of a beam under load?
The reason I'm asking is, I was hoping someone could check my numbers; I'm getting 0.1mm max deflection on the front beam (dual 100mm x 18mm x 2440mm thus actually action as a singel 100mm x 36mm x 2440mm beam) with a uniform load of 1200kg/m(note this is the weight of the entire tank. It should actually be 600kg/m since the back of the stand will carry its share of the weight as well). Just for interest sake, I'm getting 2,3mm max deflection on the stand in the Forum stickey.
Nice updates... what about the back rail being double duty? is there enough material for that?
Here are some examples of hangers ...
My favorites go over the top.. Normaly I would recommend a cushion (high density foam) between the tank & stand on glass or acrylic to keep the metal hanger from the tank, but your wood design shoud not be affected by the hanger over the top
.
Here are some examples of hangers ...
My favorites go over the top.. Normaly I would recommend a cushion (high density foam) between the tank & stand on glass or acrylic to keep the metal hanger from the tank, but your wood design shoud not be affected by the hanger over the top
.
maxumis;483647; said:
Nice design! I love the idea of an all plywood design...and to prove a point. I think it can be done and it seems that you have most of the bugs worked out. As for the diagonals, it looks like most of that will be taken care with the 'box' design. (As long as the tank bottom is screwed down to the stand as if it were the top of the stand). If this wasn't in the plan, just add an extra sheet to the top. I like the idea of the notched framing, it will add to the strength. When you glue members together, also screw them together (or use lots of clamps). It adds for a tighter seem.
I have the equation that you are looking for, but it looks like you already have it. I'll check your numbers and post the equations this weekend. Right now time is not on my side and it is also after 2am here.
Keep up the good work,
Ron
Okay, before people begin giving me the "smartass" eye. I've been researching loads and beams and joist and stresses and modulates of elasticitys and permissible stresses and a bunch of other unworldly terms. I couldn't make head or tale of it; being thrown in the deep end and all. Then a couple of nights ago I mention an observation I made with regards to the width and height of a joist, to my girlfriend. And BAM!!! She replies:"duh the formula to calculate Z is &$%^$^%$ bla bla bla" So I sat her down with a calculator and gave her weights and dimensions. 
Turns out she's not just a pretty face 
She is studying Quantity Surveying, and one of her subjects is Construction. Aint that sweet! 
Nerdy girls are hot.
So the findings: 2" x 4"(54mm x 100mm)joists centred on 16"(400mm) with a permissible stress of 7.5MPa carrying an uniform load of 1200kg/m will have a max span of 1.5m... Since my joists are only spanning +-410mm. I can rest assured that they will indeed hold the load with ease.
I recon it would be possible to draw up a table with tank height on x and tank width on y, and then have the table show proposed joist centres. Mmmm, maybe even a Jscript page to calculate everything you need to know to build a stand. You give it tank width and height, it gives you number of joists(each joist on a set of legs of course) and joist centres. Would that excite any one?
L_S as for the back rail... I'm gonna go for the extra piece of ply(total sheets for the stand now 4) Main reason; I want the stand covered as per chomper's suggestion. But I'm not doubling the rear rail. Since beam height has a DRAMATIC effect on strength. That rear rail in conjunction with the legs will be stronger than Russia...
plenty times stronger than the doubled up front configuration. Or so says Mr T and the math.
After this post I'll be able to see what a "hanger" is. But since I'm now covering the stand, can't I just screw and glue the "segmented"beam onto (under) the top cover? thus having the cover act as one big "hanger"?
Turns out she's not just a pretty face She is studying Quantity Surveying, and one of her subjects is Construction. Aint that sweet! Nerdy girls are hot.So the findings: 2" x 4"(54mm x 100mm)joists centred on 16"(400mm) with a permissible stress of 7.5MPa carrying an uniform load of 1200kg/m will have a max span of 1.5m... Since my joists are only spanning +-410mm. I can rest assured that they will indeed hold the load with ease.
I recon it would be possible to draw up a table with tank height on x and tank width on y, and then have the table show proposed joist centres. Mmmm, maybe even a Jscript page to calculate everything you need to know to build a stand. You give it tank width and height, it gives you number of joists(each joist on a set of legs of course) and joist centres. Would that excite any one?
L_S as for the back rail... I'm gonna go for the extra piece of ply(total sheets for the stand now 4) Main reason; I want the stand covered as per chomper's suggestion. But I'm not doubling the rear rail. Since beam height has a DRAMATIC effect on strength. That rear rail in conjunction with the legs will be stronger than Russia...
plenty times stronger than the doubled up front configuration. Or so says Mr T and the math.After this post I'll be able to see what a "hanger" is. But since I'm now covering the stand, can't I just screw and glue the "segmented"beam onto (under) the top cover? thus having the cover act as one big "hanger"?
maxumis;484806; said:
The hanger is to better join the center rail to the joists; a cover on the stand won't work as well to connect the beams, the cover is more for lateral (planar) support.
So, I guess I still recommend the hangers so the center beam doesn't fall out, I guess I am not sure how it will be joined to the joists. I think I am missing something
BTW; nice find of the GF
Here we call it the modulus of elasticity... Just trying to sound nerdy for your girlfriends sistermaxumis;484806; said:
maxumis;484806; said:
Yep, that works. Besides, the center beam really is only acting as bridging. It will prevent the laminated beams/frame from buckling. When it is segmented like that, it isnt reasonable to expect it to hold a load. Still I wouldnt change a thing.
maxumis;483647; said:...
I'm not really worried about the middle "segmented" beam; it's function in this design is only to help spread the load to the load beering pionts. It's only in the design for weight distribution.
...
I don't know why I didn't think of this before...It will complicate the assembly though. I was thinking of modular construction by making each beam/frame assembly and then assembling the whole stand.
If each segment of the middle beam is first screwed to each adjacent piece of plywood, then the center beam will better support the plywood top pannel (or tank floor). After a section of the middle beam is joined to the outer sheet of the adjacent perpendicular beam, then that adjacent perpendicular beam can be assembled. Sort of backwards construction but it will work.
An alternate method of assembly would be with traditional assembly line thinking. Make all of the parts then add the middle "segmented" beam using what is called Pocket Screws. They involve a jig for a hand held drill to make the 'pocket' holes for special screws. These holes are made in the segmented beam and the screw direction is from the segment to the perpendicular beam. Pocket Screws are common in cabinetry and have a lot of clamping force. I just don't know how well lower grade plywood will hold the screws in their edge. I have torn the edge out of some plywood projects so I am a little leary of recommending this method. The jig that I have sinks the hole to about 5mm from the edge. When the grain inside the plywood is parallel to the screw, there is little strength there.
One more alternate is to 'toe nail' the segmented beam. "Toe nailing" is a construction term where you would place the segmented beam in place and screw it in from an angle. This is my least favorite of all recommendations. If the screw is through the segment and into the perpendicular beam, it will have poor pull out strength. If the screw is the opposite way from the other side of the perpendicular beam into the segment, the pull out strength will be as strong as you can get but the problem is missing the segmented beam. Pre-drilling will help prevent this. If the pre-drilled hole seems to be more of a miss than a hit, just add an extra screw.
