JHCC

Converting an inverted hydraulic press into a light-duty forging press

Recommended Posts

Update: the new motor arrived, and I connected everything up and and gave it a try. 

Nada. 

The motor works fine, but there was no movement at all in the cylinder. I suspect either that the cobbled-together mess of fittings I needed to connect everything had some issue, or that the pump simply doesn’t work. 

I’m in the process of putting the original pump back on, and we’ll see how that goes. 

Share this post


Link to post
Share on other sites

 Further update: got the original pump back in, and it works very nicely. Press is much faster, out about 0.33” per second. 

I had to add a good bit of fluid to get it running, and I’m wondering if part of my problem with the other pump might have been the same issue. I think I’m going to see if I can get some better fittings to connect it to the rest of the system (rather than the cobbled-together mess I had before) and see if that and more fluid makes a difference. 

Share this post


Link to post
Share on other sites
13 minutes ago, JHCC said:

I had to add a good bit of fluid to get it running,

More than a six pack? :ph34r:

What you're doing is simple John, there shouldn't be a jumble of fittings, anywhere. There is a high pressure line OUT from the pump to the in on the valve body. Two hoses to the cylinder. A return hose from the valve to the tank. 

Excess fluid and pressure is handled internally in the valve, it escapes over bypass to the return hose.

If you have more than that on it you have too much junk. 

Frosty The Lucky.

Share this post


Link to post
Share on other sites

Video of a full cycle with the new motor:

Haven’t fired up the forge yet, but I’ll try to get some video posted once I do. 

Share this post


Link to post
Share on other sites

 Still trying to figure out a way to incorporate the new pump, I realized today that I can replace the hose between the pump and the valve with one of the pieces of salvaged tubing without having to get any additional fittings. That means that I only need something to connect the pump with the reservoir. (It also means a slightly greater efficiency, as I’m not losing power to the hose kicking.)

 My local agricultural implement place has a great stock of hydraulic fittings of all sizes and shapes, so I’ll take those parts around tomorrow and see if they have something to make the connection. More to report soon, I hope.

Share this post


Link to post
Share on other sites

Well, got the proper fitting and connected it all up aaaaaaaaaaand...

Nada. 

I noticed, however, that there was some fluid bubbling out of the vent in the cap of the reservoir, and when I took the pump off, I could see fluid pooled on the inlet side and none on the outlet side. Twisting the shaft in the direction of the arrow stamped on the housing made the former bubble, but twisting it the other way pulled it through to the outlet side. 

I deduce that at some point in the past, someone had disassembled the pump and reassembled it the other way around. 

Undoing that setup would be too complicated, so I’m going to switch the inlet and the outlet and hope that works. Back to the implement place tomorrow.  

Share this post


Link to post
Share on other sites

Update: decided to have a go after all, and it turned out to be much easier than expected. The whole system is fully assembled and running well. 

2B0759FE-82D1-40AA-8E64-2FF2C4DC0BBA.jpeg

The ram speed is now 3” in 5.12 seconds, or about 0.585”/second. 

Looking forward to trying it out with hot steel!

Share this post


Link to post
Share on other sites

A couple of questions, but first some background.

In the following lists:

  • "Original setup" means 1.5 hp/1725 rpm motor and 0.75 gpm pump
  • "Second setup" means 3.0 hp/3450 rpm motor and 0.75 gpm pump
  • "Current setup" means 3.0 hp/3450 rpm motor with 3.14 gpm pump

With perfect efficiency, these setups should produce the following speeds:

  • Original setup: 0.23"/second 
  • Second setup: 0.46"/second 
  • Current setup: 0.96"/second 

Since there's no such thing as perfect efficiency, let's assume a more realistic 85%. That would produce the following speeds:

  • Original setup: 0.20"/second 
  • Second setup: 0.39"/second 
  • Current setup:0.82"/second 

However, the observed speed of the ram is:

  • Original setup: 0.26"/second, calculated from 7.75" of travel in 30 seconds (I strongly suspect that I mis-measured this; see below)
  • Second setup: 0.33"/second, calculated from 3" of travel in 9 seconds
  • Current setup: 0.58"/second, calculated from 3" of travel in 5.2 seconds

This would mean that the actual efficiencies are:

  • Original setup: 115% (which seems rather unlikely. If we assume that the original setup had an actual speed of 0.18"/second, that would mean 80% efficiency )
  • Second setup: 72% 
  • Current setup: 60% 

So my first question is, is that decline in efficiency reasonable? Although the speed of the current setup is significantly better than it was originally, that's still a pretty dramatic drop. Is there anything I can do to get the actual efficiency closer to what it should be theoretically?

My second question is: if the system really is moving fluid at 60% efficiency, that would mean that the actual volume is 1.88 gpm. This in turn would mean that the press is producing 2735 psi (3 hp*1714/1.88 gpm).  With a 4" diameter cylinder, that would be 17.2 tons. Is this a reasonable calculation, or am I missing something else? (I haven't yet forged with the current setup, but 17.2 tons at 0.58"/second seems reasonable.)

Share this post


Link to post
Share on other sites

Pump ratings are measured at the pump outlet, not through a bunch of hose, fittings and valves. It's sort of like a car's horsepower, is it crankshaft BHP or delivered HP. What's made by the engine is absorbed by every component it's conducted through. 

The more fluid being moved the larger the % of power lost to friction. 

Pressure is lost through flex and stretch in the circuits. 

Frosty The Lucky.

 

Share this post


Link to post
Share on other sites

So, you’re saying that the 60% efficiency at the cylinder (the equivalent of delivered HP) is not unreasonable, considering the efficiency of the motor and the loss of delivered volume through friction etc? Does that apply to hydraulic pressure (tonnage) as well as to speed? In other words, has the effective tonnage dropped from the theoretical 10.8 to something like  6.2? 

Share this post


Link to post
Share on other sites

Friction shouldn't effect tonnage as much as speed and the two don't really equate. Gross entropic pressure losses come from flexible components, the worst offenders are hyd. hoses. Notice how they jump when you put pressure to the system? I don't mean just cycling the ram up and down I mean put some squeeze on something. The flex is caused by the hoses expanding in diameter. Being hydraulic the fluid puts equal psi on every interior surface in the circuit. To flex say, 2,500 psi hose draws a lot of available energy and it's lost to the work surface, the piston. 

A pump delivers higher GPM by using larger pump vanes which being larger can't deliver as much pressure for a given motor.

You need to determine if you can get more work done with a faster ram or a stronger one. This isn't an either or matter, it's pretty fluid. 

Frosty The Lucky. 

Share this post


Link to post
Share on other sites

In that case, I suppose changing the pump-to-valve connection from hose to pipe was a good thing. 

Share this post


Link to post
Share on other sites

Sure was, it was a favorite trick of  mine. Besides having less stretch pipe radiates heat faster. Cool hydraulics are happy hydraulics. Heat isn't an issue for The Presscious. 

Have you done any smooshing? You know I really want to see Presscious doing it's thing to hot steel. 

Frosty The Lucky.

Share this post


Link to post
Share on other sites

Haven't had a chance yet: I'm out of propane and haven't had the time to commit to a full-on fire-up of the coal forge. I will definitely keep you posted.

Share this post


Link to post
Share on other sites

Fluid viscocity will play in to the losses as well.  During winter a thinner fluid will work more efficiently and in summer a thicker fluid will work more efficiently. 

The thinner fluid will have higher pumping losses vs the heavier fluid for a given temperature.   So, if you match the fluid for temps it can increase speed and minimize losses. 

Share this post


Link to post
Share on other sites

Made a set of combo dies and tried them out on some hard maple:

Looking forward to actually trying them out on hot steel. 

Share this post


Link to post
Share on other sites

Have you smashed a penny? Looks good from here, plenty fast and makes kindling easily. 

Frosty The Lucky.

Share this post


Link to post
Share on other sites

First day forging with the new motor and pump. Quick takeaway: definitely improved, to the point that it’s useable. I think that I will want to upgrade the motor and pump at some point in the future, but it’s better than nothing. 

I took a moment to add some safety bars. These aren’t guards per se, but they do indicate the area outside which one should keep their hands when the motor is on. 

3EE5C5D0-F308-48C8-954C-6333E06E49A2.jpeg

Share this post


Link to post
Share on other sites

John: Do you anticipate having enough people working in your shop that you can't keep an eye on them with The Presscious running? If yes then safety bars are a good idea. Inn my shop I just yell at people crowding people using a power tool, were I going to be conducting classes I'd paint an exclusion zone around every machine and make it plain it's an 86 offense to enter that zone while someone is using the machine. If the person needs a helper then they ask me.

My only thought for the lower guards is not being able to access the dies from a low angle.

All in all The Presscious is looking good. Well done.

Frosty The Lucky.

Share this post


Link to post
Share on other sites

The safety bars are a reminder for ME. I found myself not paying quite as much attention to safe hand distance as I should, so I added the bars as a rather vigorous visual reminder. Better to have and not need than need and not have.

 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.