iDRY Vacuum Kilns

Sponsors:

Beam Size

Started by clif, October 23, 2005, 01:32:41 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

clif

Hi !!  I am wanting to cut some beams to support  a mobile home.  They will be placed perpendicular to the long axis of the trailer.  I will make them out of spruce if I can determine the size.  The problem is I do not have a formula  for this type of loading.  Can anyone tell me the formula?  I am trying to attach a drawing.  Thanks Clif
Mighty Myte Mark IV Band Saw Mill .  " Don't let the past hold you back"

clif

Quote from: clif on October 23, 2005, 01:32:41 AM
Hi !!  I am wanting to cut some beams to support  a mobile home.  They will be placed perpendicular to the long axis of the trailer.  I will make them out of spruce if I can determine the size.  The problem is I do not have a formula  for this type of loading.  Can anyone tell me the formula?  I am trying to attach a drawing.  Thanks Clif!!!
Well, I guess I do not know how to attach the drawing.  I will give a stab at trying to describe the loading.  The foundation supports are 136"  apart (inside measurement), there are two concentrated loads of 3568 #  each 18" in from the foundation supports   ( making them 100" apart)  Clear as mud? 
  ::)
Mighty Myte Mark IV Band Saw Mill .  " Don't let the past hold you back"

Furby

I'm wondering why you need the beams?

clif

I am putting it on a foundation to make it a permament structure and do not want posts under  the trailer.
Mighty Myte Mark IV Band Saw Mill .  " Don't let the past hold you back"

Furby

Foundation as in with a basement?
They usually put a wall under the main rails, or posts/block pillars.
Can't help ya with the figures, but I know Don P can and will probly be along before too long.
Here's a link to some of his stuff:
https://forestryforum.com/members/donp/CalculatorIndex.htm

Minnesota_boy

I'd be hesitant to use spruce in that application.   Spruce has little resistance to rot which may begin in the damper environment under the mobile home.  There may be much bette woods for that.
I eat a high-fiber diet.  Lots of sawdust!

Don P

I'm coming up with a 12x12 in #2 spruce if that is what you use. Few woods will get you in under 10 x 12.
I used a third point loading formula here;
http://www.ls.net/~windyhill/Calcs/2ptbeam.html
Feel free to pm me if you need more info on that part.

You know one way of making this easier might be to make "safe load" tables like I beams have. If wood were grouped into broad strength catagories and #2 or better is assumed. Using the weakest wood in each group to figure by, tables with beam dimension up one side and span across the other side of the table. Each cell in the table would have the max load for many beam sizes and spansĀ  ???

Don P

Well, running some other woods was interesting

#2 Red oak would work at 8x12
Select Structural Southern Yellow Pine could work at 8x10
#2 SYP is pretty close to #2 Northern red oak strengths.

Microllams (LVL engineered beams) would work, I imagine 4 ply by 9-1/4 or 3 ply by 11.25, the building supply could check their specs

clif

Furby: It will be a crawl space with 16" sq. block columns every ten feet supporting the beams and      double 2x8 under the exterior walls to help support the trusses I replaced the roof with.  I also put T1-11 on the walls and foamed it all in place.

Minnesota_boy:  the beams will be at least three feet off the ground which will be covered with 6mil plastic, another reason I did not want any posts in the way.

Don:  I had 1/3 pt. ,mid pt. and uniform loading, I was hoping that since the loads werre only 18" off the supports that the beams would not have to be quite that large.  Maybe just wishful thinking. Thank you for the help.  the only trees large enough in my area are spruce, cottonwood, aspen and birch.  Sure wish I had kept my Statics and Dynamics text book from school. :'(  I know the answers are in them.

I am having a little ::) trouble uploading pictures/drawings with my Mac if there are any Mac users that have the patience to explain how to do  it I would be very grateful 8)
Mighty Myte Mark IV Band Saw Mill .  " Don't let the past hold you back"

Furby

Info on pic posting from a Mac:
https://forestryforum.com/board/index.php?topic=12238.0

Quote from: clif on October 23, 2005, 10:39:26 PM
Furby: It will be a crawl space with 16" sq. block columns every ten feet supporting the beams and double 2x8 under the exterior walls to help support the trusses I replaced the roof with. I also put T1-11 on the walls and foamed it all in place.
Um, does the trailer have a pair of steel beams running the length of it?
I guess I don't understand why you need the wooden beams if you are going to have block colums.
The blocks can be laid to support the steel beams that are the structure of the trailer.
Simply run some posts up the outside with beams to carry the trusses.
I know of one trailer that is supported by block piers on a hill side. The front of the trailer is right on a footing, and the back portion is supported close to 8' high by block colums or piers.

clif

One picture is worth a thousand words >:(  I got the trailer very cheap because a heavy snow and ice load demolished the roof so I built trusses and a rafter cathedral ceiling in the living room) and placed them on the existing trailer wall which the siding has been removed and replaced with T1-11 siding.  Afterwards I ureathane foamed the walls.  The  Block columns sit out under the trailer walls to support the beams which will support the  twin Ibeams under the trailer and also the columns will support the double 2x8's headers under the exterior walls.   I am sure I have throughly confused anyone trying to visualize this set up.  :D
Mighty Myte Mark IV Band Saw Mill .  " Don't let the past hold you back"

Raphael

The best approach may be to put the columns directly below the I beams and cantilever the wood beams out to support your sistered 2x8s from.  If I've got the picture in my head right this will put the bulk of the dead weight and live load squarely on the posts.
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Don P

I think I have a muddy picture in my head.
Maximum bending moment is going to be under the rails 18" in, see if this makes sense.
Max moment= 3578 X 1.5 = 5367 ft-lbs

I would be tempted to adjust the load on the third point bending calc till I got to that moment. ???


Thank You Sponsors!