[TheForge] 15Ton Press

Fri Jan 18 16:14:05 2002

Hey Ed,
I'm in the process of ordering the video to check out the press.

Using a 5" cylinder with a 4" diameter piston sounds a little screwy.
A 4" piston would match up better in a 8" or larger cylinder which would
also give you a more controllable ram speed. 4 ips is a lot faster ram speed
than I would want to control.

If Keith is running the pump at 1/2 the recommended hp he probably has his
max pressure set pretty low, to avoid stalling his motor.

Increasing the side rails from 2" to 3" square would be fine. It would
facilitate supporting 6" die bases, but would cost more, and make the press
heavier. The larger sizes are also usually also special order at steel
yards.
You might also consider one of Jim's brainstorming ideas, of cutting the
window frame out of a single piece of solid plate. It would be tremendously
strong but unless you could find thick scrap plate and had a cheap way of
cutting it, this option would be very costly.

What are you planning to do with your press that you are worried about
excessive side loading?
I forge blade smithing hammers in large taper dies in my old press with no
problem.
Chuck

----- Original Message -----
From: Ed Fasula <[email protected]>
To: <[email protected]>
Sent: Thursday, January 17, 2002 11:43 PM
Subject: Re: [TheForge] 15Ton Press

> 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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