Medium Sized Hydraulic Press Build

Ok. I finally put this thing together.

Yeah. Either I was terribly wrong about a 2hp motor being sufficient, or the 2hp motor above is not really 2hp.

The thing works. It moves the cylinder up and down, but I can't even crush a piece of conduit without stopping the motor.

The pump never even shifts to high pressure before the motor stalls.

On retraction, using this log splitter valve, the motor chokes just kicking the valve off the detent.

So... I think I'm going to go from a 2hp 3450rpm to a 5hp 1750 rpm. That should be quadruple the torque right? Roughly speaking.
 
Man, I don't know where folks were getting 2 or 3 hp as adequate for a 25 ton press... 5 is minimum. I'm not surprised your pump would not even switch stages. Glad to hear though that you've seen this as a possibility and have already decided to upgrade power.
You'd need a 5 hp 3450 motor, to just swap in- using a 1725 motor with a pump rated for "x" GPM at 3450 rpm will result in you losing half your GPM and thus ram speed. You could swap in a 1725 motor if you changed the pump to be one with twice the displacement or GPM at 3450, and arrive at about the same ram speed with half the noise. That's how mine is, oversized the pump to make up for halving the motor speed. Less vibration that way, still good fast ram speed.
 
Man, I don't know where folks were getting 2 or 3 hp as adequate for a 25 ton press... 5 is minimum. I'm not surprised your pump would not even switch stages. Glad to hear though that you've seen this as a possibility and have already decided to upgrade power.
You'd need a 5 hp 3450 motor, to just swap in- using a 1725 motor with a pump rated for "x" GPM at 3450 rpm will result in you losing half your GPM and thus ram speed. You could swap in a 1725 motor if you changed the pump to be one with twice the displacement or GPM at 3450, and arrive at about the same ram speed with half the noise. That's how mine is, oversized the pump to make up for halving the motor speed. Less vibration that way, still good fast ram speed.

Looking through my notes I made an error in both speed calculation and purchased the wrong pump. I meant to buy an 11 GPM pump.

So, to put what you're saying on paper, here's what I get:

4.5" cylinder
15.9 sq in cylinder area
Tonnage at 3000 psi 23.8 tons

.994 cu in/rev @ 1750 RPM = 7.5 GPM
7.5 GPM will fill that cylinder at 1.8" per second ((.3208 * 7.5 GPM) / 15.9 sq in) for feet per minute * 12 for IPS
HP requirement in high range then (.994 cu in/rev) is .42 HP to make 500 PSI at 1.8 IPS
HP requirement for low range then (.192 cu in/rev) is 2.5 HP to make 3000 PSI at .35 IPS

The 2 HP motor was moving the ram 3.5 IPS at roughly 16 GPM and to make 500 PSI (required to hit low gear) would require 4.3 HP, which it couldn't do.

So I need 4.3 HP out of the motor to get into low range at 3450 RPM. Which means I should be OK with a 5hp 3600 or 1750 RPM motor, if I was OK with the speed from either motor. A 1750 RPM motor would need 2.19 HP to hit 500 PSI and get into low gear.

Ok wrap up with a 5hp 3600 RPM motor:

4.5" cylinder
15.9 sq in cylinder area
Tonnage at 3000 psi 23.8 tons

.994 cu in/rev @ 3600 RPM = 15.5 GPM
15.5 GPM will fill that cylinder at 3.7" per second ((.3208 * 15.5 GPM) / 15.9 sq in) for feet per minute * 12 for IPS
HP requirement in high range then (.994 cu in/rev) is 4.5 HP to make 500 PSI at 1.8 IPS
HP requirement for low range then (.192 cu in/rev) is 5.23 HP to make 3000 PSI at .7 IPS

ETA Changed IPM to IPS.
 
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5Hp is a better choice.

BUT .... the motor is only half the formula ... the pump is the other half. Doesn't matter if you put a 20Hp motor on it, the pump can only deliver its rating.

Also, check the settings for the by-pass/check valves. Forging presses runat 2500-3000 psi, which is higher than many lower power systems are set at.
 
I don't understand your point.

The pump is going to dictate max psi and max rate of flow based on cubic displacement per rev, and max rated RPM. My pump is rated for 3600 RPM and 3000 PSI. Additionally the relief valve on my valve spool can be adjusted to reduce the max pressure generated.

Tonnage is the product of cylinder area and system pressure.

Ram speed is the product of pump RPM and displacement divided by the volume of the cylinder.

Power requirements, outside efficiency drain, is calculated by the system pressure requirements and the rate that pressure is to be delivered.

This three legged stool can be varied to balance, or to increase one aspect of performance at the expense of another. Salem's point for example, assuming 2 pumps have max psi of 3000, a 1 cubic inch pump at 1750 rpm is the same GPM, will move a ram at the same speed, with the same HP requirements, as a .5 cubic inch pump at 3600 RPM.

This thread and others have frustrated me because the majority of the advice or comments have been about one or two legs in isolation of the third. It should be possible to simply calculate exactly what components are required to achieve a desired result, or conversely, to input available components variables and identify which other component would be needed to make up for the available one's shortcoming, outside the extreme example of a 20 hp motor on a pump rated for, say, 1000 PSI.

My original math was wrong, and I mistakenly bought a larger displacement pump than I intended, which doubled up into the result of a motor with insufficient power to generate even 500 PSI.

I have more than one option to resolve this, though a larger motor is likely the best, least expensive and highest performing option. I could get a pump with less displacement. I could get a larger cylinder, or a combination of the two. Either would increase the ability of this motor to develop greater tonnage at the expense of ram speed.

The recalculation I did above is telling me that simply getting a 5hp 3600 rpm motor will do what I originally wanted. A 5hp 1750 would do it at half the speed and have power on tap.

I'll double check those numbers again before I order, but it looks like a 5hp 3600rpm motor, and adjusting my relief valve down a bit since 3000 PSI requires slightly more than 5hp, will result in a press that moves 3.7 inches per second under no load and .7 inches per second under load, with a max tonnage output of 21 or 22 tons (guesstimating based on reducing relief valve set point).

I don't know what you mean about forging press PSI requirements being higher than most other hydraulic systems. 2500-3000 seems pretty standard in high flow unless you're talking about high pressure systems like enerpac which are low flow, or charge pumps and hydrostatic systems that are often lower pressure. It is something to watch for when shopping components for sure.
 
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Ok. I've double checked my numbers and it looks right. I've also input an estimated 85% efficiency, which gets everything right in line with the general rule of 1HP for 1GPM at 1500psi.


My pump is 2 stage, .994 ci in low pressure and .192 ci in high pressure. At 3440 RPM this is 14.8 GPM and 2.85 GPM respectively. The pump switches from low pressure to high pressure at 500 PSI. At 14.8 GPM, it would take 4.96 HP to switch to high pressure. At .192 ci, it would take 5.75 HP to make 3000 PSI at 2.85 GPM, so, throttling the relief valve down to 2600 PSI brings the HP requirement down to 4.98. Essentially, tweaking the relief valve to kick in before the motor stalls at FLA draw.

Now, with the 14.8/2.85 GPM, and a 4.5" cylinder, we can calculate that it will move 3.58"/.7" per second, and develop 20.67 tons at 2600 PSI.

Using a 1750 motor, it would essentially move half as fast, but I could run it to the max 3000 psi and generate 23.8 tons, and the motor would not work very hard to do it. Given what everyone has said about speed, I'll give up 4 tons to move 2x as fast and go with a 5hp 3440 RPM motor.

That's using the following formulas from engineers handbook:
Cylinder area in sq in= Pi x R ^2
Cylinder force in Tons = System Pressure (PSI) x Cylinder Area (sq in)/2000
GPM = Pump Displacement (cu in) x Motor RPM
Pump Input HP = GPM x Pressure (psi) / 1714 x Efficiency
Cylinder Speed (inches per second) = ((.3208 x GPM) / Cylinder Area) x 12
 
Yes, your numbers look good now.

What I was saying was some folks think just a bigger motor or a bigger pump, or a bigger cylinder will make for a more powerful press, but as you said, it is a combination of all three factors that have to be considered.
 
I built one of these based on the Batson H press plans. Fortunately I was able to give a guy at the local scrapyard $20 and the cut list and he did it all the cutting in his spare time at work. For $30, there is a lot of information there and it's worth it just to get the right parts coming. I used a 5hp motor and 20 ton cylinder. It's more than adequate for my use.
 
Trial run today. 5hp was the trick. The pop can was just all I had left to crush when I thought to record it. I'm hoping to make dies and mash metal tomorrow.

 
Looks good, nice and fast. I also would be interested in a solidworks file as I'm starting to rethink using my I beam. I can make it work but it will take some clever building and thicker steel then my plasma can cut. But a H press I could whip out rather quickly. I see you decided to use square tubing instead of angle for the sides. Looking good man
 
Yes. I was worried the angle iron would want to twist. I can export the assembly to solidworks easy enough. You'll want to tweak it I'm sure but it would give you a starting point.
 
That would be sweet. What's your tube thickness? Looks like your plate is what 1/2". I will send you my email
 
The tubes are .25 wall. The die plates are .5 but all the other plate is .75 ar400. Just because it was scrap.
 
Looks like it runs really nice. Oh and email
JTcustomKnives
at
Gmail.com
 
I would just send the cut list to my local steel guys and have them cut it. How do you like the bottom ram moving the die and steel up. That's how my mini press is and I allways thought when I upgraded I would go with a top ram set up.
 
I would like a top ram more, but not enough more to make the effort to build it that way.
 
this is what i tossed together while we where watching a boring movie. The tubes are 4" square and 48" long but that was just a random guess as i dont know ram length.

press%20H.jpg
 
my only issue is that everything is welded so no rebuilding it if something wears or binds up
 
Well, I initially intended to bolt the top together, so everything could slide out the top, but being pressed for time I just welded it all up. If it has to come apart, I'll have to air arc it apart. What you have drawn is basically mine upside down, then you need to get it up to working height which I didn't think I really had ceiling height for. I'll send my model shortly.
 
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