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jplambs
19th November 2012, 08:42 PM
I'm almost finished building my new 40' auger and as I get down to the final few bits and pieces I think I may have been a bit to clever for my own good.

The auger works on a scissor lift principle and when it is in the lowered position the hydraulic oil tank is currently a bit lower than the inlet to the hydraulic pump. The question I have for those in the know is, is the pump going to provide enough suction to draw oil from the tank when it is in the lowered position or will I have to relocate the tank?

I'm using a v-twin briggs with the pump directly mounted to a bellhouse/clutch.

Cheers.

justinc
19th November 2012, 10:03 PM
MOST pumps require a pressure head to work effectively without cavitation. How much work / flow will the pump require at the position where the tank is level or lower?

If any more than a light load I think you will have a problem.:(


JC

sdt463
19th November 2012, 10:22 PM
I have a log spliter that I built that has the pump about 30 cm above the tank and it has never been a problem. If you have already built it give it a try and see how you go.
Dave

Blknight.aus
19th November 2012, 10:55 PM
it will only be a problem if you start approaching pump stall where the suction of the pump drops off because theres too much pressure on the other side of it.

IT wont self prime and once it starts cavitating it'll keep doing so until you get to a high flow low pressure situation on the output of the pump.

Rick1970
22nd November 2012, 03:22 AM
True that pump inlet below oil level is prefered, but as long as its not a stupid height above it and your hose (suction) is appropriately sized it will be fine.

jplambs
24th November 2012, 08:06 AM
Thanks Guys I think that answers the question, sorry I haven't been back on, we have been tied up fighting fires for most of the week.

When the auger is raised, and not by a lot, the tank rises above the pump. That is the position that it will be doing most of its work in so it sounds like it should be fine.

Cheers.

Nova
26th November 2012, 07:11 PM
You had better drop it into my place and make yourself another one without this problem. I should be able to find a use for it. :D:D

Thunder out your way again tonight? Making me nervous again. How did you fare last week?

Cheers,
Nova

jplambs
29th November 2012, 12:05 AM
Steady on, its only taken me 18 months to get it to this stage. Although I suppose if I tried again I'd know what I was doing this time. ;-)

Yup there was a bit on Monday, we fared ok but I spent three days south of here looking after a fire at Pitlochry last week, it took out about 300 Ha's all good though now.

Gerokent
29th November 2012, 10:23 AM
"MOST pumps require a pressure head to work effectively without cavitation."

Just being pedantic, but this is aeration. Cavitation is usally caused by restriction in the inlet, or to thick or cold oil. Both cause damage. Aeration will cause faults further into the system (jerky movement, overheating the oil, ect), whereas cavitation usally only affects the pump.;)

Blknight.aus
29th November 2012, 05:30 PM
to be really pedantic...

its cavitation..

areation is when air is introduced to the oil by means of an air leak on the suction side of the pump, in the pump or by venturi effect at joints during high flow low pressure operation.

cavitation is when micro bubbles are formed in the pump that immidiately collapse. they're bad for a whole host of other reasons.

justinc
29th November 2012, 09:45 PM
"MOST pumps require a pressure head to work effectively without cavitation."

Just being pedantic, but this is aeration. Cavitation is usally caused by restriction in the inlet, or to thick or cold oil. Both cause damage. Aeration will cause faults further into the system (jerky movement, overheating the oil, ect), whereas cavitation usally only affects the pump.;)

When I did fluid mechanics, I was taught Cavitation is a collapsing pressure wave generated within the fluid caused by a sudden pressure drop (after the impeller blades) due to; low inlet flow, a restriction in the inlet, too high a pump speed, or too high a viscosity fluid. This will erode and even destroy surfaces within the pump as each collapsing pressure wave is equivalent to a miniature explosive force.

AFAIR this LEADS to aeration, another serious pump efficiency scenario.

JC

Blknight.aus
29th November 2012, 10:17 PM
and that would be the near textbook explanation of cavitation.

Cavitation doesnt cause areation of the oil but when the 2 combine.... the areation tends to cancel out the cavitation as the oil becomes compressible..

heres a simple demo to try...

cup a strong steel rod in your hand have someone smack the other end with a large hammer... hurts yeah? well done, thats the end result of cavitation.

now do the same thing but first cup the rod in a large carwash sponge, the impact is the same but its softened.

Now try to manouver the rod, you can do so far more precisely without the sponge ( assuming the rod is long enough and heavy enough) and that follows the effect on your hydraulic system.

with the pump cavitating the oil coming out of it is still continuous oil (no bubbles) so the system will still work, with the oil getting aerated you loose accuracy in the system as the "oil" is now compressible due to the air in it, as the system pressure changes the oil bubbles shrink and grow

For my money...

Cavitation is worse than aeration because you cant see the pressure waves coming out of the pump at better than ludicrous speed that shortens the service life of joints, hoses, pipes, seals, valve spools pretty much everything thats not a nice fat chunk of unforgiving cast metal.

Gerokent
30th November 2012, 09:30 AM
I stand corrected. :bangin:

jplambs
1st December 2012, 07:20 AM
Another question for all the gurus, does it/will it harm the pump if I run the motor with out any oil flow for more than a few minutes? Just wondering for while I'm in the process of setting the hydraulic connections and motor up.

Cheers, JP

Blknight.aus
1st December 2012, 07:37 AM
if your operating without bypass oil relief, yes.

if you have bypass oil relief no

If you have a 4 port 3 position DCV no because that will usually be set up for normal flow, reverse flow and return to tank

If your pump has in internal pressure relief return to in put no.

Blknight.aus
1st December 2012, 06:40 PM
Shatter beer bottles: Bare-handed bottle smash - YouTube

special thanks to carjunkieanon in the interesting pics thread for the link to the machine gun rocket pack on the XKCD website and my natural curiosity to read the whole what if section and blindly follow relevant links.

start watching at about 44 seconds.

jplambs
4th December 2012, 10:31 PM
Thanks for all the help Dave, you're invaluable as always.

I've pretty well finished assembly and encountered another problem tonight, as soon as the engine goes under load it starts surging, once I engage the hydraulic drive I get about two revolutions out of the auger and the engine stalls. I tried adjusting the governor but that only made the problem more obvious. If I hold the governor open the problem pretty well disappears, fuel supply isn't an issue so I think I might have to tackle the carby tomorrow. Any other ideas?

I know the rules around here so I thought I had better add some photo's, you'll all have to excuse the mess under the auger, it's where I'm storing my tools in the neighbour's shed while I'm doing the work.

Blknight.aus
4th December 2012, 10:40 PM
governor tension not set correctly for the application.

Choke spring

air filter

blocked emulsion tube in the carby.

Rick1970
5th December 2012, 05:16 AM
If the engine checks out ok.........

Is it enough HP for the application? Was the engine sized to closely to the pump input HP requirements? From experiance if the pump needs 8HP @3600 rpm to give the required pressure, this would meen at least a 10-11HP petrol engine. Adjusting the goverened speed up will increase the the required input HP the pump needs to deliver the required pressure.

There can and will be a sudden line pressure spike when you engage the auger that will load up the engine and show up if the engine has a problem or is too small for the job. Not exact, but as a very basic rule of thumb, every 1(us) GPM of oil flow @ 1500PSI needs 1HP to drive it. So 5gpm @ 1500psi needs 5HP, 10gpm @ 3000psi needs 20HP.

I have some charts that give grain screw auger HP requirements and delivery rates at differant speeds/angles at work if you need to varify anything.



On a side note, bit hard to see in the pic but that return line into the top of the tank. The oil returns below oil level yes? If not, fit a drop tube to the fitting into the tank so it does. Filter ????

jplambs
5th December 2012, 06:46 AM
Hi Rick, The V-twin is a 16HP Briggs, when I made some initial inquiry with the hydraulic supply company they believed that it was big enough for the job. That was over 18 months ago now (this has been a long, slow project). Regarding the return line, no it doesn't return below fluid level, is this quite important? The filter is on its way, I was going to place it inbetween the high pressure line and the spool.

Cheers JP

Blknight.aus
5th December 2012, 05:03 PM
yes, if the oil return is above the oil level you can aerate the oil in the tank, the system wont like that.

unless your getting a full pressure full flow filter the filter in hydraulic units usually goes in the return to tank line and you have a strainer on the suction side to catch the rocks before they hit the pump.

bushrover
5th December 2012, 08:04 PM
All hydraulic systems develop pressure due to the microscopic air bubbles in the oil. Oil itself doesn't compress so cannot produce pressure only flow. The oil is the lubricant, cooling mechanism and the solid that causes movement - you don't need any oil to actually cause movement, any gas can do that. Cavitation can occur in pumps, motors, valves, cylinders, sharp bends, etc, etc, when the microscopic air bubbles expand due to low pressure i.e. motor over running, hence anti-cav valves fitted to motors.

Aeration is introduced air in a system on the suction side of a pump, motor (suction side on over run), valves on the low pressure side, leaking cylinder seals, etc, etc. Dieseling is when the enlarged air bubbles from cavitation are suddenly compressed again and explode - diesel. Aeration usually causes wear (lack of lubrication and cooling), can cause dieseling - on the pressure side of a pump or cylinder. Erosion is caused by dirt, metal, cavitation and dieseling.

and the thousand other causes and scenarios of problems in hydraulic systems. Generally you need positive pressure to the pump and no air in a hydraulic system and as already stated, the return line must be below the lowest oil level in the tank.

and jplambs, you will 100% guaranteed fail components early in your hydraulic system with the setup you have. How early is in length of string territory.

Rick

jplambs
5th December 2012, 08:50 PM
Hi Rick, thanks for that, what exactly is going to cause the failure in the system, do you still believe that it will fail if the oil return is below the oil level and a filter is installed inline?

Cheers JP

Blknight.aus
5th December 2012, 09:04 PM
all hydraulic systems fail, eventually... I've currently got 2 failed $100K+ pressure rigs at work at the moment....

the more overkill you build into them the longer and crappier they will continue to run.

bushrover
5th December 2012, 11:05 PM
Hi Rick, thanks for that, what exactly is going to cause the failure in the system, do you still believe that it will fail if the oil return is below the oil level and a filter is installed inline?

Cheers JP

JP

Hydraulic pumps don't like a suction head so every time the tank is below the pump you risk damage and as already stated return oil in to the top of a tank will aerate the oil and possibly cause damage to any part of your system.

How long will it last.............................................. ................................ who knows, but a well set up system running at the same speed, volume, pressure etc as yours will last longer.

Bottom line, if you can raise the tank so the oil level will never be lower than the pump inlet and put the return in the lower part of the tank or as already said, extend a tube to the bottom of the tank, you will go a long way to improving reliability.

Oh... and definitely fit a return filter or if you insist a high pressure filter as well after the pump - but get advice on what to use before doing this.

Plenty of good advise on here. Just set it up well, keep the oil clean and cool and you won't have a problem.


Rick

Rick1970
6th December 2012, 03:40 AM
If you run into trouble, give me screw dia, auger length, numbers on motor and pump i can double check it.



Yeah, return should be below oil level. Prevents airating the oil and problems stated above.

Filter in the pressure line is good, IF its a high pressure filter (expensive). If its a spin on canister, it will be a return filter and should be in the return line between spool valve and tank. High pressure will make short work of a spin on element.

Suction strainer is good, but must be of an decent size and you must be able to get access to it to replace it. This can sometimes be hard in a smallish tank like yours.

Keep an eye on the oil temp when using it, if you can hold your hand on the tank, its generally ok.

If it was me, i wouldn't be running it till there is a filter in place. A lot of contaminats in a hydraulic system are put there bolting it all together and the filter removes a lot of this. Do a filter change shortly after putting the auger into use, sorta 1st service kinda thing. Filler/breather cap on the tank is a service item too, and should be replaced when you do the oil/filter.

I know that you proberly coppied a factory built auger, but most of the the manufactures designs are 99% cost motivated and the quality of a lot of the crap sold to farmers amazes me.

jplambs
6th December 2012, 08:47 PM
Hi Rick, Rick and Dave,

I confirmed the order of the filter this morning - it's one for the return side - there is a drain plug on the bottom of the tank that utilises a bsp thread so I should be able to plumb the oil return in there. It is at the opposite end of the tank to the suction as I was mindful to ensure that I allowed for some cooling in the system.

Regarding the oil height issue I have discovered that when I raise the auger to what I would consider to be its lowest working height the oil tank - or at least a third of it - is above the pump.

What I'm thinking of doing at this stage is changing a couple of fittings around this week so I can hydraulically drive it from the tractor for harvest next week - this should allow the screw to bed in to the barrel - and then try to get the engine sorted when I don't have to rush.

Rick the motor is a MR 125 C004 and the pump is a 20C22X016G (the 016 used to be ?77 - it has been stamped over) the petrol is a 16HP Briggs Vanguard 303447 1302-E1 and the Auger is 40' and 8" diameter.

The Auger is a copy of a F.A. Miller and Sons auger in terms of the scissor lift however there are a couple of differences, FAMSON used 1"1/4 pipe for the carriage I've used 2"x3" 2.5mm RHS. They used a hydraulic cylinder for lift and lower and I've used a braked winch (the cylinder was $1600). The reason for the auger build was that my old one was completely destroyed when a neighbour borrowed it and the motor broke away from the front linkage arm, swung up and smashed the barrel as he was going up his driveway. It wasn't his fault as it could have happened to anyone. The motor wasn't damaged during the incident (it was the platform it was on that caused the damage to the barrel) so that is the motor that is being reused for this project. I wasn't too worried about it initially as another neighbour has a similar auger, albeit 34 or 36 feet and a 9 inch barrel and he is powering that hydraulically with a 13 HP Briggs. Not only that he often has it working at 45 Deg angles.

Cheers again,

Jonathan.

Rick1970
7th December 2012, 03:38 AM
Ok, the pumps appears to be 22cc so at 3600rpm (i take thats its a direct drive engine, no reduction) you should be getting around 20GPM (US). The motor is 125cc so auger speed @3600 engine rpm will be around the 600rpm mark and deliver about 78t/hour. 8" screw @ 600rpm takes .42hp/foot @ 45', so 16.8hp to drive auger. With a 125cc motor, the line pressure would have to be around 1450 psi. To drive a pump with an output of 20gpm @ 1450psi would take 20.3hp..............basicaly a 24hp petrol engine. Even running the auger vertical (lest hp required and lest grain shifted) would take 9.2hp at the auger.

With oil flow like this, you would also need 3/4" hoses for the pressure and work lines, 1 1/2" for the suction and 1" for the return.

If it was me, i would be dropping that pump size to something in the 11-13cc range, dropping your oil flow to around 10-12gpm and auger speed closer to 350rpm.

Returning the oil straight into the bottom is ok, but you will need some type of baffle in/over the port to stop the oil pushing straight up through the tank, basically airaiting it from the other side from where it is now. Weld/silver solder a drop tube into the existing fitting to drop the return point under oil level would be easier.

Nova
7th December 2012, 09:45 AM
Nice looking unit there.

A suggestion for you. Seeing that you are using a braked winch for the raise/lower you could drive it with a small hydraulic motor instead of the handle and make it quicker to raise. Can you easily add another spool? My auger runs like that and works really well.

Cheers,
Nova

jplambs
7th December 2012, 12:52 PM
Hi Nova, unfortunately no, in the original quote from John F. (you should be able to work that one out) he quoted for a double spool. All the gear then turned up just as I broke my back last year and I didn't notice for about 3 months that it was a single. By that time he wasn't interested in doing anything about it. He was also meant to have made sure that the motor, spool and pump were going to work with this auger, something I've now discovered since this thread and subsequently talking to shipway's he didn't do. He had the petrol motor in there to make sure it would be right too.

Rick, thanks once again for all your help, so just to make sure I understand you correctly if I went with that smaller pump I would be quite safe running things with the current motor and the existing half inch pressure and return lines as well as the 1 inch suction line?

350 RPM doesn't bother me, I just want to get the grain moved as safely as possible not at light speed.

Blknight.aus
7th December 2012, 01:42 PM
correct

thing of it like gearing (assuming all the max pressures are in order) If you have a small pump driving a big motor it is effectively geared down.

IF you have a large pump driving a small motor it is effectively geared up.

For low tech applications like this one, if speed really isnt an issue (Ie you can start it let it run while you walk away from it) then a power steering pump isnt a bad solution

Rick1970
7th December 2012, 06:06 PM
Your average automotive p/s pump may be a bit small and slow for this application. On that note, i did however reseal a p/s pump, from a ZD Fairlane i think, that was being used to drive the bat reel on a baby plot harvester/header. Chain driven from a shaft on the front, so it only runs when you engage the front. Simple and effective.

If speed isn't an issue, stick to a smaller pump, 10cc, even 9cc and it should do it easy. Everything will run that bit cooler and you won't be taxing the engine quite as much. Currant hoses will be ok.