Running a Hydraulic Motor - Valve Question

[Soundguy]

Wow.. calm down and put the red hot poker down

And don't worry.. no enthusiasm was needed.. I merely wrote a reply post.. And actually.. if you read my post carefully.. i was not even advocating using an ORC in place of the correct valve setup.. but rather I was reasoning thru what was happening ( out loud ) when a person used a regular spool valve on a motor.. (which is like a pump).. and when the return port wuld be blocked.. it would be like a pump deadheading.. except there would be no relief on that side of the system... In my suposition of that situation.. I also kicked in that it would be a motor with no orc doing this, as one with an orc.. wouldn't be carrying any more inertia than the rotating part of the pump. IE.. I was just trying to visulize what was going on in the circuit. ( I use visulization techniques and other low tech 'cheat' cues as a means to follow circuit flow in electronics.. helps me keep it all sorted out... I'm sure it's not the 'correct' way.. but hey.. it works for me.... and I've gotten pretty good at -not- letting the magic smoke out of too many electron powered devices for a while now...).. plumbing has some pretty good parallels to electronic circuit routeing... but I freely admit to having much less hyd experience...

Besides...are you seriously implying that the only form of ORC that exists in society today are the kind that pin or quick-pin onto the rear end of tractor pto stubs?

I've got a belly mower that has an integral ORC ratchet device built into the unit. It is between the top pulley and the blade carrier... A nice option I might add.

I've seen plenty of tractor pto setups with internal over running ratchets ( some good designs.. some not so good ).

Remember...I was merely speculating on a hypothetical possibility.. not making an all emcompassing statement.

Add to that that there are always more than one way to skin a cat.

Say I'm out in my backyard poking thru the junk pile trying to make a combination thingamabob-doohicky on the cheap with my ac only stick welder and a chop saw ( cuz I'm too cheap to own a decent set of torches.. or a plasma cutter ).. I've got most of the parts.. but not them fancy valves that would be the perfect soloution for my hyd motor problem. But.. I might have some old surplus drive component that has an orc built in.. or even one I can scavenage off my old rusty tractors. What do you know.. it would probably work on the cheap. A mechanical answer to a plumbing problem.

There are many such examples.. for instance.. mechanical answers to electrical problems. Generator comutator segments that rotate with brushes for making DC power instead of some fancy silicon devices. Way low tech.. but they work. Old style phone PBX systems that had mechanical rollers and cams for changinf electrical contact positions.... stone knives and bear skins.. but they worked. ( I had the 'fun' of maintaining such a PBX type system at one of my first jobs.. imagine my surprise when I found out that there was more 'mechanical' then 'electro' in the phrase electro-mechanical.. in that maintenance duty. In fact.. other than some fuses popping.. the bulk of my work on that phone system was maintaining the mechanical portions...

I'm not trying to be a jerk.. I'm just putting out some theoretical discussion here.

If every message got a single 'by the book' answer.. this web site would be so much less fun to read.... And the answer to every question could be phrased like " Refer to the shop service manual for your device , and reference the paragraph that applies to your specific problem area.".. The moderator or list owner could simply copy/paste that answer to -any- question that was posted.. and it would of course.. be answerd in the most efficient and correct way.. without actually saying anything... Could probably be shortened to 'repair it correctly' once most of the membership was up to speed. That would save bandwidth...

I like tinkering.. I like going to old engine and tractor shows and seeing how some people got buy without the right tools.. or without the right parts. ( I'm sure many people her also do.. otherwise we wouldn't see the multitude of was you can belt up or chain up a pto genset to any and every spinning part of a tractor EXCEPT the rear pto... there are a decent bunch of tinkerers and hobby machinists here that sometimes just build things because they can.. not because it is the most effecient.. or the most correct.)

While it's not correct.. i get a kick out of seeing a household water valve sticking out the lower rear right side of a ford 8n with a hose brazed on to the 'flow' end running to a loader lift cyl, and a chain wrapped around the upper lift arm going around the axle trumpet to divert flow out thru that water valve tot he loader when needed...

I find the ingenuity refreshing when I see a sheet metal screw threaded thru a piece of innertube sticking into an oil pan.. knowing that some poor guy probably got home one cold night without his old beater car burning up because he didn't loose his oil. Even thought he correct fix was a new oil pan.. or to drop it and weld it, braze it or solder it.

Same thing with seeing a penny soldered to the tank on a radiator. It's not correct.. but it's a cheap fix.

I also like the old push lawnmowers at shows that have their blade removed, and a hole cut in the deck and a automotive alternator bracketed in with a belt over to the drive shaft, with +/- cables ported over to an insulative block of wood, or terminating in jumper cable ends.... Just pull the rope and you have a high amperage push battery charger/booster that runs on a pint of gas and you can push it wherever you want to and don't need a 300' extension cord. Conventional? surely not. Practical? good possibility, even if the weird factor is pushing some high marks.. IMHO.. a gas powered battery charger is no more odd than an electric chainsaw...

For every correct way to complete a project there are dozens of incorrect ways.. and some of those incorrect ways happen to work just fine even if they fly in the face of conventional logic.

who wants the soapbox.. I'm done with it.

At this point all appologize to the original poster for hijacking this thread off topic, and to Rick for introducing non standard thinking on the subject.

Who's next? I can still sit down so the jobs not done yet!

Actually.. before anyone does reply.. please DO note the appropriate use of I have used in this reply.. and take the message in that tone.

Rick's a super smart guy.. and nothing in my message should be construed that I'm disagreeing with his good factual info. I'm just point out that my bent sense of reasoning makes to to the finish line of the same race using a different path.


Soundguy

I'm not picking on you, Chris, really. I just can't develop any enthusiasm for your mechanical answer to a hydraulic concern. It is just one more frigging thing to have to design into an implement or whatever that someone else has presumably done at least a fair job of engineering. The vast majority of off-the-shelf hydraulic motors in applications germain to this discussion would have round, keyed shafts of one inch diameter or possibly a little more. Never have I seen one with a 1-1/8" or 1-3/8 " six splined output shaft. So we get to adapt a round keyed shaft on the motor to a splined shaft to accept our ORC that just cost us $45-$60. Then we get to adapt the ORC's output BACK to the round, keyed drive coupler the implement had to accept the motor to begin with. Go find one or two orbit motor applications and check out what would be required. Makes a zero pressure return or crossover relief look pretty inviting IMHO. BTW, you are missing out on the 9 inches of snow I just had to blow out of my drive up here.

 

[Soundguy]

You could just put a check valve between the IN and OUT lines to the motor and do the same as an ORC.

DRL

Why a check and not a relief??. ( Ok.. I admit I only took a single hyd class in engineering school.. and it is late.. so I may be missing the obvious here.. )

soundguy

 

[RickB]

Wow.. calm down and put the red hot poker down




Soundguy

No red hot poker here; we are just not in agreement. And I wanted to explain why I disagree. No sweat.

 

[DRL]

Why a check and not a relief??. ( Ok.. I admit I only took a single hyd class in engineering school.. and it is late.. so I may be missing the obvious here.. )

As explained in other posts I was just throwing out other ideas. Maybe you have a CV in a junk box and would have to buy a PR. A PR would bring the motor to a stop smoothly, how long it took to stop could be controlled with an adjustable PR. Using a CV the motor would coast more like a ORC.

DRL

 

[Soundguy]

No red hot poker here; we are just not in agreement. And I wanted to explain why I disagree. No sweat.

I guess I'm not thinking that we 'aren't' in agreement.

I'm not saying the hyd valve method is wrong.. or that the mechanical method is particularly correct. I was merely trying to visualize what fluid dynamics were happening in the circuit when a regular valve got turned off with an inertia load on the motor.. and then visually compair it to a non inertia load.. I just think in more 'mechanical' nature to sort out the permutations in the circuit... in my theoretical schematic in my head.. an ORC ont he pump was my way to eliminate the inertial load from the motor, in order to think about what happened in the circuit. Not specifically correct fluid flow wise, as the valve you speak of actually remains open on the return side.. but int he end.. the same functionality was reached... no 'pop' spike load on the output line of the pump...

Just because i specified a possible alternate method to accomplish something doesn't mean I particularly endorse it as a good fix.. just that it was possible'.. besides.. as i said.. in my original message.. I was 'thinking out loud'.. IE.. not meaning for that visual representaion to actually be physically manifest...I actually think we are more in agreement, than disagreement.

Good thing no hot poker... some of my job is 'sit down' time.. and that would be darn uncomfortable!

Soundguy

 

[Yankee Clipper]

I don't know of any compact tractor that offers a motor valve, as most use three position (up- neutral - down) neutral detented control valves. The spring loaded neutral is why you need a bungee cord to keep it in the work position.
Motor valves have a detent that keeps it latched in the work position until you want to shut the motor or drive off. When you shut the flow off in a motor valve, you have a position that allows the motor to coast or else the motor can blow the shaft seal or other damage be done.
Rick hit it on the head that the cheap way to fix this is to use a low pressure return - straight return from the motor discharge port to the tractor reservoir so if the control valve is accidentally put in neutral, the fluid can go to the reservoir while the motor (and driven stuff) spools down.
Most open center systems do not have motor valves - maybe Deere does offer one - I dunno. Larger tractors using load sensing systems allow you to tune to flow to multiple circuits on multiple valves without wasting HP and fuel - a bigger deal all the time.

 

[john_bud]

Why a check and not a relief??. ( Ok.. I admit I only took a single hyd class in engineering school.. and it is late.. so I may be missing the obvious here.. )

As explained in other posts I was just throwing out other ideas. Maybe you have a CV in a junk box and would have to buy a PR. A PR would bring the motor to a stop smoothly, how long it took to stop could be controlled with an adjustable PR. Using a CV the motor would coast more like a ORC.

DRL

I may be wrong (it happens!), but I think you mean a Cushion valve and not a check valve. A check valve stops flow until the valve directed pressure overcomes the latent pressure in the hoses. They are used commonly in loader control valves so when you have the loader 1/2 way up with a full bucket the boom won't drop as soon as you crack the valve. The check holds it until the valve directed pressure starts it moving.

As stated earlier, a cushion valve is a dual bypassing system made up of 2 relief valves and some internal fluid routing. They are used in backhoe swing circuits usually mounted under the box between the BH control valve and the swing cylinders. As you might imagine, there is a lot of inertia when you swing a boom and full bucket side to side then flip the control back to center. The cushion valve allows the boom to smoothly slow to a stop.

jb

 

[Soundguy]

That was my point.. I was asking the poster if he really meant check valve.. or a relief setup.. etc..

soundguy

I may be wrong (it happens!), but I think you mean a Cushion valve and not a check valve. A check valve stops flow until the valve directed pressure overcomes the latent pressure in the hoses. They are used commonly in loader control valves so when you have the loader 1/2 way up with a full bucket the boom won't drop as soon as you crack the valve. The check holds it until the valve directed pressure starts it moving.

As stated earlier, a cushion valve is a dual bypassing system made up of 2 relief valves and some internal fluid routing. They are used in backhoe swing circuits usually mounted under the box between the BH control valve and the swing cylinders. As you might imagine, there is a lot of inertia when you swing a boom and full bucket side to side then flip the control back to center. The cushion valve allows the boom to smoothly slow to a stop.

jb

 

[DRL]

As stated earlier, a cushion valve is a dual bypassing system made up of 2 relief valves and some internal fluid routing. They are used in backhoe swing circuits usually mounted under the box between the BH control valve and the swing cylinders. As you might imagine, there is a lot of inertia when you swing a boom and full bucket side to side then flip the control back to center. The cushion valve allows the boom to smoothly slow to a stop.

jb

Yes I know, I was the one that stated it. A cushion valve is the best choice. I was throwing out other ways to skin a cat. Didn't I read the project we are talking about will only turn one direction? If so, you can use a crossover line with a check valve between the lines to the motor. The check valve allows fluid to go from the OUTlet to the INlet of the motor. This setup WILL allow the motor to freewheel with the valve closed.
Sorry I am not being very clear, I can't even talk without pen and scratch paper much less type.

DRL

 

[radman1]

I'm not picking on you, Chris, really. I just can't develop any enthusiasm for your mechanical answer to a hydraulic concern. It is just one more frigging thing to have to design into an implement or whatever that someone else has presumably done at least a fair job of engineering. The vast majority of off-the-shelf hydraulic motors in applications germain to this discussion would have round, keyed shafts of one inch diameter or possibly a little more. Never have I seen one with a 1-1/8" or 1-3/8 " six splined output shaft. So we get to adapt a round keyed shaft on the motor to a splined shaft to accept our ORC that just cost us $45-$60. Then we get to adapt the ORC's output BACK to the round, keyed drive coupler the implement had to accept the motor to begin with. Go find one or two orbit motor applications and check out what would be required. Makes a zero pressure return or crossover relief look pretty inviting IMHO. BTW, you are missing out on the 9 inches of snow I just had to blow out of my drive up here.

FYI, Surplus Center has 3 different pto drive motors with 1-3/8" 6 tooth splined shaft like on typical pto shaft. Just type in pto drive motor. Cost is about $280-290.