I beam sizing help for press build

[Rccrawlerguy]

I am looking to build a shop press. 52" wide bed with a 40 ton jack.

I am looking to use 10x26# beam
the moment of inertia of that is 144

Wl^3
_________
384EI

W= load
l^3= distance

384 in a constant
E=modulus of elasticity
I= moment of inertia

SOooo.

80,000*(52*52*52)
384*29,000,000*144

I crossed out some zeros and got

8*140608
384*2900*144

=
.00701 Can anyone verify that for me? I did the calculation 3 times using that formula, and got the same result.

 

[iron_worker]

I believe the formula you're using is for a beam with a distributed load across the entire beam. The formula for a fixed beam with a point load at mid span (worst case) is:

Deflection max = (WL^3) / (192*E*I)

Modulus = 29,000,000 lb/in^2
Moment of inertia = 144in^4 for 10 x 26 W beam
Length = 52"

Deflection max = .014"

Stress max = WL/8Z

Z=Section Modulus = 27.9in^3 for 10x26 W beam

Stress max = 18,638lb/in^2 = 18.6ksi

I believe you could expect a yield strength of 36ksi minimum and higher with higher grades of beam. So the safety factor is in the range of 2:1.

I think you should be ok with this design if you are in fact fixing both ends of the beam and not pinning them. That will increase the stress and deflection significantly.

IW

 

[Rccrawlerguy]

Thanks for the reply. Yes, the ends will be fixed. I am building this strictly as a press brake.

 

[A_Pmech]

An I-beam is not the greatest starting point for a press brake. It just doesn't have enough stiffness in the load axis. The result is a bend which varies in angle as a result of the press brake's "smile." Tooling held in the ram will also tend to work free if there's too much ram deflection.

Most of the major manufacturers use deep beams made from plate rather than rolled structural sections. If you haven't purchased materials yet, you might consider going that route.

 

[iron_worker]

You could also box in the beam front and back for a very substantial increase in strength. At that point, it might be just as easy to create your own beam as A_PMech mentions.

I don't have much experience using a press and none building one so others will have to chime in on how sensitive they are to deflection during use.

IW

 

[Kevin54]

First off.......RCCRAWLER.....welcome to Garage Journal. I hope you hang around for a long while, and if you are going to build a press, make a build thread for others in case they want to build a press also.

A while back, I posted up a drawing and dimensions for a 5 ton press. I also have a 30 ton press that I can do the same for, if you are interested. As far as all of the E=MC squared x moment of impact on your uncles side.....totally lost there.

But let me ask you this.....I have a 30 ton that does damn near anything a home fabricator needs. At work, some of our punch presses were 60 tons and pretty stout. What are you doing that you need a 50 ton press? At work, in the toolroom, I used a 50 ton hydraulic/electric Enerpac, and with the work we did, and some of it was concerning heavy dies, I can count maybe 3 or four times in the 32 years that I was there that we ever came close to using the 50 tons. Not trying to discourage you in any way, and I know bigger is better, but If you are going for overkill, I can't help you. But if you are interested, I can give you come pics and make up a detailed drawing of a 30 ton press. It would take me a few hours to make the drawing, but I'd be more than happy to help you out.

Just remember, the heavier the tonnage, and the wider the table opening, the heavier the I-Beam will need to be. Not so much for the uprights or the feet, but the top beam and the table beam both need to be equal in size due to the fact that what is pushing down is equal to what is pushing up.

 

[zkling]

Are you building a general press that will use a specific brake attachment, or are you building a dedicated press brake only machine? There is a difference in build style due to the loading that AP Mech described.

Ironworker gave you the correct forumla, but. Just a FYI, when analyzing a structure you need to look at the overall picture. Simply going after one component can lead to problems and or a lawsuit.

 

[Rccrawlerguy]

I am building this as a press brake specifically.I chose the W14x26# because i can get it for $10/foot. I can go bigger if needed. It will just cost me a little more.

Why did I choose 40T? I want to bend 1/8" steel up to 48" wide. Using the chart from Accurpress.com, it says 11ga(.120) with a 1" die will take 7.7T per foot. 10ga(.135) will take 9.9T per foot. So, I picked 40T.

Why did I choose 52" wide? I would like to be able to bend the full 48" wide, plus have a little extra if I need to bend something diagonal.

 

[A_Pmech]

For comparison, a section of 1" plate 24" deep is about 10 times stiffer than the W-section beam you propose using.