Cantilever bracket question

[ken masoumi]

I was wondering if I could make brackets that when installed,will have more space under the shelf they are supporting, what I mean is, instead of having a 45° cross piece from the tip of the "free end " of the bracket to the wall, I move it inward by 6" therefore creating more space under the shelf for easy passage or storage ,will this bracket still support the weight of 120 lbs?
The second small (6"x8") bracket is 8" below the the main one.
scan0001.pdf (http://www.sawmillcreek.org/attachment.php?attachmentid=312699&d=1430574267)

Sorry for the crude drawing I linked, if any of you has access to a computer drawing software, I would appreciate a more refined drawing to replace mine.

[Jamie Buxton]

The shelf itself is something like 3/4" plywood? Then yes, this should work just fine. I'd put one bracket every other stud. You might consider banding the edge of the plywood with something taller than 3/4", to prevent sagging under loads between the brackets.

[Jamie Buxton]

Or you could go with commercial brackets like these from Speedbrace -- http://www.wwhardware.com/fastcap-speed-brace-shelf-bracket-fcsb

[ken masoumi]

Those are good solid brackets ,good to know they are available,but for now and for this project I'm working on I already have a few metal brackets(Walmart) and I'm thinking of building 3 with 2x4s (one on either ends and one in the middle) so I'm all ready to do it this way.the length of the shelf is 96" by 18" deep.
I'll be using the metal ones on every stud.

[ian maybury]

Hi Ken. Guess it's in the end an engineering/structural design problem. Moving the strut in by 6in has several effects. The outer lip of the shelf is left unsupported. The force in the strut will increase by something approaching double, as will the loadings at both ends of it, and the consequent force trying to peel the rear leaf and the back of the shelf (or pull apart the corner joint on the bracket if it's carrying all the load) up and away from the wall too.

How the 120lbs is placed will also make a big difference. Worst case is as a point load at the front edge of the shelf, with 120lbs over each bracket. Regularly distributed (the 120 lbs spread) along the legth of the shelf eases the situation considerably, especially if the shelf is long and there's lots of struts. Regularly distributed, and centered well in from the front lip of the shelf is better again.

It's easy enough to bulk up the struts and increase the number to handle any extra load, but the outboard portion of the shelf is left cantilevered and has to support whatever load on it's own. Knowing the set up it's not too hard to calculate, but experience probably knows what works anyway.

Jamie's brackets look like a great solution to this very common problem. (think many of us have been down the road of figuring whether or not we can fit in a less intrusive shelf bracket layout to store heavy stuff in the workshop context) Whether or not they can handle 1,000lbs depends on all of the above (e.g. a regularly distributed 1,000lbs tight in against the wall is easy - it depends on how the loading is applied), but judging by the guy climbing on his shelves in the video they should be fine. There's likely a design/permitted loading spec document about somewhere for them, the suppliers might be able to help.

One to be careful of on fairly heavily loaded shelves is that there's the possibility either way of generating quite a lot of pull out force on whatever fixing screw/bolt is used at the top. You guys typically run lag bolts into timber studs, but if into masonry expanding plastic plugs (Rawlplugs) are not great in that regard. There's hardened self tapping bolts (what amount to lag bolts) for concrete about in recent years, they can have great pull out resistance but need an accurately sized drilled hole and no screwing in and out (once in only) to work properly....

[ken masoumi]

Thank you both for your comments,the weight of ~120 lbs will be distributed as evenly as possible and more toward the wall than the unsupported lip ,I'll be using 6 metal brackets(14"x 14")every 16" instead of the original idea of using smaller brackets because I am not really comfortable with leaving 6" of the shelf unsupported , I will also install two full length heavy duty bracket on the ends(one on each end ) but upside down ,plus metal brackets on the bottom . this may sound like overkill but I hope it will make the 96"x18" shelf well anchored ,any thoughts?

[Reinis Kanders]

120 lbs per 96 inches does not seem to be that much, less than 1.5 lbs per inch. I am no structural engineer, but it does not seem to be much of a load.

[ian maybury]

As Reinis 120 lbs over 96 in or specifically over 6 brackets isn't that bad - 20 lbs/bracket Ken.

Hardwood weighs about 45 lbs/cu ft. If we said that there was a maximium of solid pile of boards 15in wide x 15in long x say 12in high at most being supported by each bracket in your typical workshop wood store install that would amount to roughly 1.6 cu ft or 72lbs/bracket - maybe more if somebody gets really heavy handed. By that measure your 20 lbs/bracket doesn't seem wildly ambitious - but your need to make it neat/slim/to take up less space underneath ups the ante. (presuming it's for wood storage) It's not by accident that wooden brackets typically place the strut right out near the ends of the batons - Ikea reckon this pretty skinny example of a long strut type can handle over 30 lbs: http://www.ikea.com/us/en/catalog/products/56696109/ Moving the strut inwards would hugely weaken it however.

People are putting up shelves fairly regularly in workshops, but possibly with simpler formats or using commercial hardware. Maybe somebody has a proven bracket design?

I can't say by looking/ getting a lot more specific whether what you propose would be OK or not. One major issue is to come up with a sound bracket design. I wouldn't be keen on leaving the overhung part of the shelf in your sketch unsupported. If on the other hand you were to make up some brackets made out of good hefty timber batons in the form of an inverted L with a supporting strut about half way in like the one in your sketch (or like a beefier version of the Ikea one, but with the strut moved in some distance) then the horizontal batons could continue right to the outer edge of your shelf and hence support your overhang - without intruding too much in the under shelf space. Much like the commercial steel ones, but with the strut added since steel is strong enough to avoid the need for one. (you'll notice the deep web they have in the corner just the same)

Key requirements apart from making sure the basic members are strong enough (the price of moving the strut in is that they likely need to be several times stronger) would be to ensure that the corner of the L was very well jointed to handle the strong outwards pull. The strut would likewise need to be either notched in or otherwise well secured to ensure that it can't slip.

Sorry i'm not giving an answer in words of one syllable - I can't. Simple triangle brackets in e.g. ply are more straightforward, but the requirement for neatness/not intruding into the space underneath ups the ante/forces sailing close to the wind big time. Making strong shelf brackets in wood that look nice/so they don't take up too much space is a pretty hefty woodworking project too - it's probably not by accident that most use commercial (metal) shelf brackets with a specified load capability.

One option if you definitely want to go DIY - you could consider making a test bracket, mounting it as you intend and then carefully/safely and progressively loading it to failure. It probably wouldn't be unusual in a formal design scenario to require it to handle x5 the your nominal load for longer term safety.

[ken masoumi]

Reinis,Ian, you were both right about the weight not being a huge issue , I found that out after I installed 6 home (Depot bought) metal brackets and tested the shelf,it felt solid ,put on more( than usual ) weight near the middle of the shelf and it was still fine .
I guess I was over thinking the bracket /weight ratio ,I still have a 4" overhang but I'll leave it the way it is since it will handle all the weight I plan to put on it.. as you can see in the picture I have plenty of space under the shelf to store my jointer and the two tool chests so I did achieve enough space with those metal brackets after all.
Thank you all for your help.
Ken.
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[ian maybury]

Sounds good Ken. Pardon my making it a little long winded - i hope the stuff brought out the reality that small differences can have big implications...

[ken masoumi]

Sounds good Ken. Pardon my making it a little long winded, but as i hope the stuff brought out small differences can have big implications...
Ian, I was hoping and got thorough responses here , but your posts in particular made a few issues a lot easier to understand, I thought having a second bracket to act as a support for the brace would allow me to move that brace a few inches back ,your post made me realize it's possible but to a limited degree,thank you for taking the time to explain it all so clearly.