[TheForge] 15Ton Press

[Ed Fasula]

Hi Chuck,

 > (you wrote)
Hey Ed, You have gotten me a little confused, A "22 gpm" 2 stage pump  puts 
out 22 gpm / 6.5 gpm at 3600 rpm with a 10 hp motor. When you couple it to 
a 1800 rpm 5 hp motor you now have an 11 gpm / 3.25 pump, not 22 gpm. So at 
low pressure Keith's ram is moving about 2 ips. Once it contacts the work 
at high pressure it is moving a little over .6 ips. You need to read Jim's 
primer again.
<

You're assuming he uses an 1800 rpm motor.  Have you seen the video?  He 
says his motor runs at 3450 rpm.  He calls his pump a 22-11.  So, according 
to Keith's description anyway, he actually is running twice as fast and 
with half the horsepower Batson recommends in his book.

 >
Also look at my design again.  The bottom die is stationary. The top die
moves. The square guides resist all side loading forces and you can attach
the cylinder to the frame with enough clearance (slop) so that it doesn't
see  the side loading.
<

Yep.  I understood that, Chuck.  The guides take all the side loading 
coming from the top die into the rails.  The sum of the torque applied to 
the ends of the main cross bar from the guides is equal and opposite to the 
torque applied to the center of the main cross bar by the bottom die.  So 
the cylinder doesn't see side load.  But to do this the rails have to 
transfer take some pretty hefty torque.  Like I said, by my rough numbers 
2x2 solid only allows about 1/2" off center forging.

 >
If you intend to do extreme  off center work , that you know will be
generating large  side loading forces, I would recommend using the 2
cylinder version of my design to avoid over stressing the frame.
<

No don't say that!  I just swapped cylinders once.  I don't want to go back 
looking for two now.  Seriously, you mentioned concern about balancing the 
cylinders.  I share your concern.  I don't know how to do it off hand.  So, 
looking at making the frame strong enough:

Batson calls for a 48,000# press to have 300,000 in-lb of torque 
resistance.  300,000 / 48,000 = 6.25 off center.  Well, that's huge.  Let's 
look at the numbers another way: Stress = M/S  where M is torque (or 
moment) and S is section modulus, which can be found in tables.  Checking 
against Batson's table for a W21X44 he lists safety factor of 5.9.  S for 
W21X44 is 81.6.  For typical structural steel allowable bending stress is 
about 24,000 psi.  300,000 / 81.6 = 3,700 psi  actual stress.  24,000 / 
3,700 = 6.5.  So these numbers are close to his.  If we added in the 
tension stress, which isn't much, we'd be closer to 5.9.

So, now, lets look at the side rails of a 48,000# press of your design with 
Batson's torque.  Rearranging, S(required) = M / 24,000.  So, S (required) 
= 300,000 / 24,000 = 12.5.  But, the torque is carried by two rails so it's 
6.25.  A 3 3/8" square solid bar gives S of 6.4.  Only a factor of safety 
of 1.02  And that's ignoring tension.

Similarly, by Batson's specs, for my 82,000 press 4x4 solid bars or 
5x5x1/2" tube would be considered minimal.

On the other hand, Batson's H frame double side angles have an S of 
3.06.  So, M = 3.06 x 24,000 = 73,400 but times 2 sides = 147,000 
in-lb.  So 147,000/48,000 = 3" off center with no safety factor and 
ignoring tension.   If you figure his safety factor of 6: 3/6 = 1/2" off 
center forging allowed.

Well, I just wore myself out.  The moral of the story is, I have no clue 
what a realistic off-center distance to design for is.  I'm seriously 
considering welding up 8x2x3/8" into 'T' shapes for side rails.

 >
The bigger pump and new cylinder should work better. The rod diameter should
also be fine in my design.
Chuck
<

Thanks for the information, Chuck.  Now I'm going to check into the 
capacity of a motor run at lower rpm with a VFD.

Ed


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