Designing a long drawer for a heavy load?
#8
  
I'm building drawers for a built-in cabinet, where the drawer width could be up to 33" but the depth won't be more than 15".  Given the built-in cabinet's constraints, I expect I'll need to use side-mount runners--I want two layers of drawers, top & bottom, and there's little vertical space to accommodate bottom-mount runners.

I'll be using the drawers for a vinyl collection.  Given the size & weight, then, two full-width drawers could be subject to upwards of 110 lbs each.

   

I have 3/4" plywood for the box, and 1/2" for the bottom which I plan to dado in 1/2" from the edge.

What should I be aware of regarding this build?  Can heavy-duty, side-mount runners reliably support these drawers?  Is there danger of the drawer sagging in the center under this load?  Will racking be an issue for this design?  Should I plan for drawer dividers, front to back, to enhance the strength & rigidity?

   

Thanks for your input.
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#9
  Re: Designing a long drawer for a heavy load? by grwold (I'm building drawers...)
I built the same style of drawers for the built-in base cabinet bank in my shop a couple of years ago. I use these four drawers for very heavy items, i.e. routers, electric drills and other heavy items. I used side mounted slides with ~100 lb. capacity. Used the same material you mentioned, 3/4" for the sides, front and back and 1/2" dadoed in for the bottom. So far it's worked great with absolutely not problems.

Using plywood, you can glue all the joints, including the bottom, which makes it very strong.
When installing the slides, I think I put a screw in every mounting hole for extra support.

Good luck,

Doug
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#10
  Re: Designing a long drawer for a heavy load? by grwold (I'm building drawers...)
I did similar drawers for my wife's photo albums, which are probably just as heavy. The drawers I made were 34x22x12 (I think) with sides and bottoms as you plan (3/4" and 1/2"). We moved from that house, but I believe the side were poplar instead of plywood. Doesn't matter, after I glued everything together they were extremely strong, and supported on 100# full extension slides. They were in service for over 5 years before we moved and nary a problem. The dividers you show probably would add to the strength and rigidity, but I'm not sure it's needed. With a drawer that wide and a heavy load, if you install 2 drawer pulls and someone attempts to open it with just one, it might ***** a little on the slides.....but I doubt you'll have any problem with it racking.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#11
  Re: Designing a long drawer for a heavy load? by grwold (I'm building drawers...)
You need the sagulator, which calculates the amount of sag for various materials when certain loads are applied. There are many ways to stiffen up the bottom of a drawer. The dividers you show have the effect of reducing the drawer width (as long as they are secured to the front and back of the drawer.

The sagulator is an online calculator and it's free to use.

https://woodbin.com/calcs/sagulator/
Still Learning,

Allan Hill
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#12
  Re: Designing a long drawer for a heavy load? by grwold (I'm building drawers...)
Thank you, all. Appreciate the feedback.

Allan, that sagulator is all right! If I used it correctly, it claims I'll have 0.000" sag per foot ("Plywood, fir").
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#13
  Re: Designing a long drawer for a heavy load? by grwold (I'm building drawers...)
Blum makes an accessory for wide draws.

https://www.amazon.com/Blum-TANDEM-Later...B00ZGKOFCS
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#14
  Re: RE: Designing a long drawer for a heavy load? by Cooler (Blum makes an access...)
You can buy side mounted slides with at least 500 lb capacity, if needed.  In your case, you could calculate the approximate load when full, but I'll bet slides with 150 lb capacity would be more than sufficient.  Your drawer design is more than robust enough.  

John
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