Question for the hydraulically minded...

D

deker

Joined
Nov 14, 2005
Messages
3,496
So I went out to the shop to do some forging this morning and when I flipped on the press the pump sounded a bit different than usual and I noticed that the hose on the input side of the pump was collapsing under power. Am I right in thinking that something must be clogging the intake in the tank? Any other things that might cause this?

I'm assuming that I'll have to drain the system, pull the pickup out of the tank, clean everything out, and put it back together. What's the best way to drain the tank? do I just pump it out, or can I do something like disconnect the low pressure return line and let the pump do the work for me?

Thanks,

-d
 
Sounds like something is clogged. In order to clear it, you're going to have to take things all apart, and clean EVERYTHING until you find the issue. Based on you saying the line on the input side of the pump is collapsing, the plug is somewhere "down stream" of there. Worst case, your going to have to disassemble everything the fluid flows through, until you locate the issue.
If could be something as simple as being low on fluid....check that first. (you've likely already done that)

If the intake at the tank is plugged, you'll like have to find a way to take it apart, or possibly blow it out once the fluid is evacuated.

DO NOT try to drain the tank by disconnecting one side and turning it on!! That will be a train wreck, and you will likely get hurt in the process!!! BEFORE you take anything apart, shut off the power, and leave it off until everything is back together!!!
 
Thanks Ed. That's about what I figured the drill would be, but I always have to check since every time I *THINK* I understand how something works and spend hours doing it, thats usually when somebody steps up and says "Do this instead, it's the easy way" :D

So, find a way to pump or siphon the tank dry, take it all apart, clean, and reassemble. That should be a fun (and messy) day...

-d
 
Ed Caffrey said:
Sounds like something is clogged.

Based on you saying the line on the input side of the pump is collapsing, the plug is somewhere "down stream" of there.
Click to expand...


I agreed with what Ed said, but I would say that the blockage is UPSTREAM of the collapsed hose.

I would start with that hose, take it off, see if you can blow compressed air through it...
keep working back from there.


I would suspect a couple of things,

A clogged intake pickup screen
(You SHOULD have one of these to prevent taking up junk into the pump and valves)
the bigger it is, the less likely it it to be starved.
a large screen area, not just on the hose end..and kept raised up off the bottom of the tank too.
If the pickup too is too low it can become clogged with sludge that builds up on the bottom of the tank where the moisture collects

looking for a pic...

a stuck check valve on the intake side or improperly installed in the wrong direction...
(if you tookit apart since last time you used it)
moisture can rust inside these things


Does your tank have a breather?
If not it needs one, It cannot be sealed tight,
-if the air can't move into the tank...the oil can't move.

If you do have a completely open breather, close it off with mesh screen or something,
If a mouse can get in (opening size of a dime) it will & die and rot inside-clogging the intake hose.
Especially with the changing colder season, they are moving inside now.
-oil change time.
(another pro for an oil pickup screen)

If you have an oil drain plug at the bottom, you can tap it off now and again to check for sludge buildup.
 
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I need to double check for a drain plug. IIRC the lowest fitting on the tank is the one that connects to the intake hose. I'll have to double check. I haven't looked at the inside of the tank at all since I got the press. I suppose it'll be good to tear it all apart and learn more about it. The bit that sucks is that I'll likely have to pick the whole mess up to drain it as it sits on the floor. Good thing the engine hoist is handy. :) Yes there is a breather on the tank, and yes, it's filtered.

I suppose I'll be cleaning all the fittings while I've got everything torn apart. What type of pipe dope should I use when I re-assemble it?

Thanks,

-d
 
Is your intake hose a hydraulic hose? If not it could be breaking down due too the oil.
This is a common problem with hydro. systems. People use the cheap hose for the intake because there is no pressure. There should be a strainer/ screen in the tank for the intake hose.
Dan
 
cgn-hs said:
Is your intake hose a hydraulic hose? If not it could be breaking down due too the oil.
This is a common problem with hydro. systems. People use the cheap hose for the intake because there is no pressure. There should be a strainer/ screen in the tank for the intake hose.
Dan
Click to expand...

Hadn't thought of that. I have no idea what type of hose it is as I didn't build the press. I'll likely replace it just to be sure. I've got some other hoses I'll be replacing while I'm at it. What's one more right? :)

-d
 
Ok, so I just finally got time to get this handled. I took apart the intake and there was a mat of fiber clogging the pickup screen. My best guess is broken down filter material. That's been cleaned out. I replaced the intake hose with a new piece of hydraulic intake hose, and replaced the high pressure hoses to the cylinder with new shorter ones, including some new 45 degree swivel fittings to route the hoses in a safe, shorter path. New filter installed, 10 gallons of new hydraulic oil and the press is running again! I had one small leak at initial startup, but tightening the fitting a little more seems to have fixed it. I'll be back forging again soon! :)

Oh, and the pump sounds VERY different now. The whine is much lower in pitch which means to me that it was previously working too hard.

-d
 
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zaph1 said:
WooHoo! Great to know you got it fixed.
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Yup! Now I just need to put this project at work that's had me going 7 days a week for the past 3 weeks to bed and I'll be forging again! With any luck I'll fire the forge on Sunday! :)

-d
 
So, I've got some more hydraulic questions....Rather than start another thread I figure I'll bump this one up and see what happens.

I came across a really good deal on some brand new Sauer Danfoss DS250 hydraulic motors and grabbed a couple figuring that they would be good to run a twisting machine and rolling mill. According to the spec sheets here they will put out around 270lb/ft of torque continuous. I figure with a little torque multiplication via a chain drive I'll be in the 600-700lb/ft I'd like to see for my twisting machine. The problem is speed. According to the documentation, the motor will run 250-300RPM at a full flow of 16GPM. That's WAAAAAY to fast. However, when I began to look at the graph on page 35 of the specs linked above, I THINK what I'm seeing is that you can get slower speeds with lower flow and so long as the pressure is maintained the torque will be the same. It looks like the sweet spot is 1550PSI@4GPM. Since I want to run this off of the same powerpak I use for the press, I've got WAY more pump than I need to do that. So, my question is, can I get away with using a motor valve like this and adjust the relief valve all the way down to 1550PSI to keep the torque at the sweet spot. Then I'd put a flow restrictor like this or this between the valve and the motor to reduce flow and slow things down to the RPM I want. So, the other question that arises is "which flow restrictor?". I think (but I'm looking for some schooling here) that if I put a single bidirectional flow restrictor on either side of the motor that I'd get the same motor speed in either direction. If I put in a flow restrictor that restricts only one way, I'd need two right? Once I get this figured out I'm only a few hundred $$ and a weekend or two away from a machine that will twist 2.5" bars of steel with ease.

Then I just need to sell some Damascus to make the $$ :)

So, is my reasoning here sound? Anybody here have experience that they'd be willing to share?

Thanks,

-d
 
If you are multiplying the torque with a chain drive, you will also be lowering the speed by the same factor.


I would just use a gear reduction output on the motor ( they are cheap from the surplus suppliers). A 10:1 reduction will gain a lot of torque and slow that horse down to about 1/2 RPS ( 30RPM), which should be a good range for twisting.
 
bladsmth said:
If you are multiplying the torque with a chain drive, you will also be lowering the speed by the same factor.


I would just use a gear reduction output on the motor ( they are cheap from the surplus suppliers). A 10:1 reduction will gain a lot of torque and slow that horse down to about 1/2 RPS ( 30RPM), which should be a good range for twisting.
Click to expand...

I looked into gear reducers and the ones that can handle the torque that this hydraulic motor will put out are anything but cheap. I know it's not apples to apples, but the HP ratings might help clarify a bit. The hydraulic motors I've got will be running between 12-13HP and almost 300lb/ft of torque. That's a big and expensive gear box. Most of the affordable ones I've seen are 1-2HP input. I'd shred those.

On the other hand, I can get #60 chain and sprockets at my local farm supply for not a whole lot. I looked into doing all the reduction with the chain/sprocket setup and it would require a jack shaft setup and at least one 15" diameter 60 tooth #60 sprocket which would be neat looking, but more large dangerous spinning stuff to build giant guards around. If I can keep things compact and easy to build safety guards around I'd prefer to go that route. The price just about balances out since the large sprockets needed to do all the reduction would be about the same in price (or possibly more) than the flow restrictor setup.

-d
 
get a junk car differential and weld the spiders. a 3.55 differential is 3.55/1 ratio driveshaft to axle rotation. you can usually find the ratio on a tag on one of the cover bolts. Full sized car diffs can handle the the torque and if you go to a u-pullit junkyard, or you have a redneck friend with a yard full of old cars you can get them pretty cheaply. once I figure out which axle is going in my Duster I will have an extra, but that's a few months down the road at least, I have to get the rest of the drivetrain reassembled first

-Page
 
sunshadow said:
get a junk car differential and weld the spiders. a 3.55 differential is 3.55/1 ratio driveshaft to axle rotation. you can usually find the ratio on a tag on one of the cover bolts. Full sized car diffs can handle the the torque and if you go to a u-pullit junkyard, or you have a redneck friend with a yard full of old cars you can get them pretty cheaply. once I figure out which axle is going in my Duster I will have an extra, but that's a few months down the road at least, I have to get the rest of the drivetrain reassembled first

-Page
Click to expand...

But then the machine would be HUGE! Unless I got into cutting down axles, etc which is more work and expense than $100 worth of sprockets and chain from Tractor Supply. Really, I shouldn't need more than a 2'x3' footprint for the whole deal, including the "bed" area that the bar to be twisted will be over. Most bars won't be more than 12-18" long. Anything longer will be twisted by hand anyways since it would be small (Viking style composites). I see no reason for twisting a 3' bar of 2"x2" stock. Ok...I can see a few reasons for it, but I'm not building Damascus motorcycles or anything... :D

I'll hopefully have some time in a while to do up some drawings of the machine as I have it in my mind. Maybe it will make a bit more sense then.

-d
 
You could also use a car transmission, if you remove the tailshaft housing from something like the A833 4 speed I have for the Duster it is a package 14 inches x 16 inches by around 18 inches. You could also build something based on the planetarys out of an automatic transmission. Just a thought.

-Page
 
sunshadow said:
You could also use a car transmission, if you remove the tailshaft housing from something like the A833 4 speed I have for the Duster it is a package 14 inches x 16 inches by around 18 inches. You could also build something based on the planetarys out of an automatic transmission. Just a thought.

-Page
Click to expand...

I was going to suggest something like this,

in Amish or Old Order Mennonite areas, you see lots of these transmission hookups to small diesel engines for just about anything.

You have a choice of 4 or 5 ratios to choose from as well.
 
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