help with steel spans

[48Rob]

I need help to determine what size, and or shape, of steel I need to use to span/support a floor.

The main rails of the trailer are 66 inches apart.
The main rails are 2 inches wide, 8" tall, and 1/8" thick.

I need to weld supports under the main rails, spanning the 66 inches to support a plywood floor.
The overall dimensions of the area are 66 inches wide x 9' long.
The supports will be 70" long, with 4 inches of contact/weld area.
I was planning on either 3/4", or 1/2" plywood for the floor.

In the largest open area, when the maximum number of people "could" be standing together, the combined weight would be 1000 pounds
(4 people @ 250 pounds each.)
The plywood floor and covering adds another 100 pounds, so total of around 1100-1200 pounds to potentially be supported.
There are no cabinets or other items/weight on the area in question.
Average weight in the center of the span is only 600 pounds or so, but I want to plan for worst case.

What is the smallest (shortest vertically) beam, angle, or tube I can use to support the weight in that span, and the centers needed for them?

Thank you.

Rob

[Wanna Be]

HI 48Rob!

You would probably need 6 spaces, (16" center) to make the light weight factor.
I would use some 1x2x3/16 tube for that purpose.

It might be overkill BUT we are talking about peoples safety, So go with some overkill on steel,
You can save weight with some lighter weight plywood then.

Just my $0.02 worth.


WannaBe Lynn

[48Rob]

Thanks Lynn!

Do you know offhand what a single 1 x 2 x 3/16 tube can carry in the middle of a 66" span?

Rob

[Wanna Be]

48Rob,

According to the specification book that I have, That size will hold up to 500# in that span.

The only reason I would use that is just for safety,and lighter weight.

If you use lighter steel, you would HAVE to use heavy plywood too.

Hope this helps.

Lynn,,,,WannaBe

[48Rob]

Thank you Lynn,

Reason I was asking is because it is physically possible for three people, or two heavy people (600#+) to end up standing on just one support.
They would, if that happened, be closer to the outside than the middle, so maybe really nothing to be concerned about.
A little deflection is okay, but not a lot.
I realize the plywood will help spread the load, but I am indeed interested in using thinner plywood.
1/4 inch is a very big gain in this limited headroom project.
The 1 x 2 steel (I'm assuming the two inch side will be vertical...) will leave me with 8" of ground clearance, which I've determined is the minimum clearance I'll be comfortable with.
If there is 1" steel that can be used for support, I can gain an entire inch of head room!

Weight is of some concern, but I have several hundred pounds to play with before I reach my maximum, so another 20-30 pounds of steel isn't a deal breaker.

Rob