Steel brackets to hold bench seat up

[frogger]

Hi,

Just wondering if someone can help.
I want to get 3 steel L brackets build to support a bench seat I have built. I need the brackets to support up to 200kg. The vertical plate will be held into the double brick wall using dinabolts. I dont want the plate too large so that you can not see it below. My questions are.
Seat size is 1400mm x 560mm with 45mm support frame.

My question is how think and what type of steel I will need to support this weight ? I will have the horizontal peice weldered to the vertical plate. Also what type of steel should I be using. ie thickness, solid, hollow etc.
I hope thats enough info for someone to help.
Frogger

[wheelinround]

Thats a fair weight Frogger plus the weight of the bench
I'd be looking at Gal angle 60mmx60mmx6mm width of the bench with and same down the wall under the bench.

[Jacksin]

The seat looks a fair weight in itself plus allowing for a couple of perhaps heavy weight adults (or kids jumping around) and you are asking an awful lot on the brackets.

I think Wheelinround's steel size could be under-gauge. I would think 10mm minimum thickness with a 45deg welded bracing with the whole thing galvanised.

Have you considered Frogger, dyna-bolting through the back framing into the wall and installing a couple of fancy (turned) legs under the front corners?

[Ivan in Oz]

Or go Square Section Gal,
with the 45* Bracing

Galvit, Then Silver Frost the cleaned up Welds?

[frogger]

Thanks for all your suggestions. Yes the bench is pretty heavy and with 2 adults plus kids on it it will need some support. 10mm thickness does sound solid but im sure with the weight invloved maybe not. When your talking that type of steel. Is it best to have a post type eg 60mm x 60mm with 6mm thickness or a solit peice of steel being 10mm thick ? Also when I get it welded is that very stong and not likely to come apart ? In regards to Jacksin comment I want to bench to be floating hence why i need such huge supports.

[MrFixIt]

Hi

Thanks for all your suggestions. Yes the bench is pretty heavy and with 2 adults plus kids on it it will need some support. 10mm thickness does sound solid but im sure with the weight invloved maybe not.

The "thickness" is not the critical part. The most important part is to have a 45º between (or very near) the ends of the "L" bracket.

Provided that YOUR method of mounting the bracket will support 200kg, a pair of 6mm thick brackets (with the 45º support) will EASILY support 200kg weight.

[frogger]

ok thanks. With the "L" bracket I only want it to come down the wall around 150mm. The other part of the "L" bracket can be 500mm long. Ill use 2 x 12mm dinabolts to hold it in. Will the '"L" bracket need a 45degree support or the weld should be enough to hold it ?

[DJ’s Timber]

I don't think you'll get away with 150mm part of the "L" it's too short, the amount of leverage at the end of the 500mm bit will either pull the bolts out or crack the bricks.

And yes you'll need a 45° support on it unless you're using box tubing or angle, flat bar won't be able to support itself.

[Yonnee]

Agreed,
Structurally you would get away with something like a piece of 150mm x 50mm x 6mm RHS the length of the bench and butt weld 3 outriggers the depth of the bench of say 50mm x 50mm x 6mm. Weld them with a 3 phase MIG and they would certainly be strong enough, but its the fixings into the bricks and the bricks themselves I'd be concerned about. If you wanted to persevere, I'd dyna-bolt every brick along the length of the bench as well as construction adhesive.

[Ivan in Oz]

Perhaps Chem-Set Type
rather than Dyna Bolt......Or should I say "Mechanicaly Fixing" them.

Also,
Yes,
I agree,
the 150mm Vertical is a Bit short.....Quite a Bit Short

[frogger]

Thats great. Thanks for your help with that. What would be best. Using boxing or flat steel. If boxing what size would be the best ? Using maybe the 50mm x 50mm ?

[DJ’s Timber]

Here's a drawing of how I would make it, using 50mm x 50mm x 2.5mm tube.

Attachment 64227

With the holes for the dynabolts, I would have them as far apart as possible with the top one inside the gusset area drilling a 25mm hole on that side with a 12mm hole on the brick side and the the bottom 12mm hole hole can be in the 45° cutout section. Would located the holes so they line up with the middle of the bricks as long as they are solid bricks. If not solid bricks, would be even better to drill right through the double skin brick wall and use all thread and put a 5mm flat bar with holes to line up with the ones in the bracket on the other side of the wall

Same for the long leg, say 3 holes to take a wood screw, so would need say 3 - 5mm holes on top and 2 - 12mm holes on the bottom side with the last 5mm hole in the 45° cutout section.

[frogger]

DJ. You are a super star. Thank you so much for that. That is a huge help. Thank you so much to everyone who has helped. I think your diagram more than answers my needs. Thanks again.
Frogger

[MrFixIt]

Hi

ok thanks. With the "L" bracket I only want it to come down the wall around 150mm.

This is REALLY TOO short

The other part of the "L" bracket can be 500mm long.

For THIS length. The *leverage* is very high on the top dyna bolt. Fixing the bracket mechanically or chemically will not make any difference to the load/stress on the top bolt, however the chemical based fastener is less likely to pull out.

Think of the leverage like that of a claw hammer when used to pull out nails. Your bracket will be "pulling" on the top bolt. Any "jumping" up and down on the seat by kids (et al) will be like tapping out the dynabolts. They may hold, they may not

Ill use 2 x 12mm dinabolts to hold it in. Will the '"L" bracket need a 45degree support

Absolutely

or the weld should be enough to hold it ?

No, it won't.

If you really *must* have a SHORT bracket then if you are making the brackets or are having them made to suit your needs then consider having a "leg" above the horizontal leg, (see rough image below) but still invisible behind the seat itself. A dyna bolt though THIS short leg will help the structural strength against being pulled out.

It will "transfer" the load to a point between the two top bolts and will therefore act less like a lever (claw hammer) on thetop bolt.

The angled support arm does not HAVE to be 45º, it needs to be from the outer end of the horizontal arm to the lowest convenient point on the arm attached to the wall the very bottom is ok with the lower dyna bolt mounted just above - make sure you have enough room to fit the bolt and nut .
It will not be as strong though as a longer downward leg.

HTH

[Pulse]

...sure are a lot of amateur structural engineers on this forum... we really need a real one.

On the rams et website:
A 6mm dynabolt only 25mm embedded into 20Mpa concrete has a tension working limit of 2200 N or about 220kg per anchor. Depending on the size of the bracket two of these should be plently...

10mm steel, dynabolts into every brick and 12mm dynabolts really are overkill....

The longer the leg attached to the wall, the smaller the fastener you could use. The bench is 560mm deep so a 560mm leg attached to the wall means the weight of the person (if represented by a point load 560mm from the wall) is equal to the tension on the fastener. If the vertical leg is halved then the tension in the anchor is doubled. Therefore a 140mm vertical leg against the wall with two brackets supporting 100kg each would require a 4kN anchor eg a 10mm dynabolt 45mm embedded into 20Mpa or two 6mm dynabolts adequately spaced.

cheers
Pulse