Is this spool bad?

[Groo]

I think I saw a 3 section v20 on ebay for $550. Powerbeyond is likely a plug change or the like.
The v20 looks to be good up to 15gpm or so, so probably about right for most smallish tractor's.
Really, I haven't worked much with the v20, so get some advice on component selection from someone that does.
Bucher is another well known hydraulic valve maker.

 

[BeezFun]

I think I saw a 3 section v20 on ebay for $550. Powerbeyond is likely a plug change or the like.
The v20 looks to be good up to 15gpm or so, so probably about right for most smallish tractor's.
Really, I haven't worked much with the v20, so get some advice on component selection from someone that does.
Bucher is another well known hydraulic valve maker.

It's thunderstorms here today, so I'll make it a shopping/pricing day. I'd like to get the valves at the local hydraulic place if they're not way more expensive than Bucher. If I buy from them I'll take the old valve in and see what they think went wrong. This is also a chance to change the mounting location for the valve, it was too hard to reach where I mounted it before.

 

[oldnslo]

For reference I looked at Fit Rites website and used the cylinder sizes he stated for the calculations below.

Cylinder 2" bore x 1 1/4 rod has rod end area of 1.91 square inches

Cylinder 2 1/2" bore x 1 1/2" rod has rod end area of 3.14 square inches

So if you have the 2" bore cylinder a leakage rate of .48 cubic inches would let the cylinder drift 1/4" per minute.

Some companies like Bucher list the leakage rate under given conditions others do not.

I wish you the best in finding a valve that will hold position over time.

 

[BeezFun]

For reference I looked at Fit Rites website and used the cylinder sizes he stated for the calculations below.
Cylinder 2" bore x 1 1/4 rod has rod end area of 1.91 square inches
So if you have the 2" bore cylinder a leakage rate of .48 cubic inches would let the cylinder drift 1/4" per minute.
Some companies like Bucher list the leakage rate under given conditions others do not.
I wish you the best in finding a valve that will hold position over time.

I have 2" bore, 1-1/4" rod, measured leakdown this morning. Leakdown at the cylinder was .375" in 38 min, which ends up being 0.019 in*3/min. This was a far slower leakdown than when I was out mowing and I can't explain the difference because I made these measurements with the same bush hog attached. I looked up the leakage for the Bucher valve that's comparable, and it shows nominal leakage of 0.336 in*3/min !!! That just can't be right, that means the valve would leak almost twenty times as fast as the valve I have. Even with my valve, I have to tweak the tilt cylinder every half hour or so to keep the mower deck level. I'm tempted to give up on the float feature of the valve and put in a load lock valve as you suggested in another thread.

I don't understand this at all because the front loader valves on my Kubota are 15 years old and the leakage is not noticeable even after sitting for days. Are kubota valves just so well made that they don't leak?

 

[oldnslo]

Beezfun
The difference in leakage rates is a combination of factors some of which are:
Load induced pressure higher pressure equals more leakage.
Oil temperature or viscosity. Hotter thinner oil will leak more than cold thick oil. Mowing your oil was probably hotter than when you tested today.
Oil volume in cylinder(s). Tilt is one cylinder and rod end volume so kind of a worst case scenario

Butcher rated their valve at 1450 PSI (100 bar) what is the load induced pressure on the tilt with your bush hog attached?

Suspect you may have to add a Load lock valve to keep this cylinder from drifting under load due the small volume of oil

 

[BeezFun]

Beezfun
The difference in leakage rates is a combination of factors some of which are:
Load induced pressure higher pressure equals more leakage.

Yes, I knew having the load on would increase pressure but wanted to try to reproduce the same conditions I had in the field.

Oil temperature or viscosity. Hotter thinner oil will leak more than cold thick oil. Mowing your oil was probably hotter than when you tested today.

Great point, I didn't think about that even though I regularly touch the hose and say ouch. It was a hot day when I was mowing.

Oil volume in cylinder(s). Tilt is one cylinder and rod end volume so kind of a worst case scenario

Didn't appreciate that until I did the leakdown numbers. It's actually a very small volume that's involved.

Butcher rated their valve at 1450 PSI (100 bar) what is the load induced pressure on the tilt with your bush hog attached?

Seat of the pants is that the mower is 500#, probably a third on each support point, so call it 150#, distributed over 1.91 in*3, so the load is 150/1.91=78psi which is nothing compared to 1450psi. If I scale that, the leakdown on mine would be .019 * 1450/78 = .353 which is the same number as the Bucher. So that is also explained.

Suspect you may have to add a Load lock valve to keep this cylinder from drifting under load due the small volume of oil

Yeah, I think you're right. Thanks for taking the time to look at this, I think I understand what's going on now. I'm a bit surprised that so many people rave about top and tilt setups but never mention this issue. I think I might not have bothered with the investment if I understood this clearly.

 

[MtnViewRanch]

Yes, I knew having the load on would increase pressure but wanted to try to reproduce the same conditions I had in the field.


Great point, I didn't think about that even though I regularly touch the hose and say ouch. It was a hot day when I was mowing.


Didn't appreciate that until I did the leakdown numbers. It's actually a very small volume that's involved.


Seat of the pants is that the mower is 500#, probably a third on each support point, so call it 150#, distributed over 1.91 in*3, so the load is 150/1.91=78psi which is nothing compared to 1450psi. If I scale that, the leakdown on mine would be .019 * 1450/78 = .353 which is the same number as the Bucher. So that is also explained.


Yeah, I think you're right. Thanks for taking the time to look at this, I think I understand what's going on now. I'm a bit surprised that so many people rave about top and tilt setups but never mention this issue. I think I might not have bothered with the investment if I understood this clearly.

All I can say is that I have only sold Bucher valves to my customers, I have never, not a single complaint about the valves leaking down excessively. I have Bucher valves on my 75hp tractor, and with a 3500lb implement, the drop rate is acceptable at less than 1/4" per hour. I guess my point is that even with the acceptable leak rate that Bucher has, the valves DO NOT leak at that rate which is why I only sell them.

It seems like all the other valves have some issues from time to time.

And as far as your 500lb mower, you need to figure that the weight is substantially more when cantilevered out 6' from the actual cylinder rod. IT IS NOT 78psi at the cylinder.

If this is really only an issue with your mower, why not simply un-plug the rod end hose when mowing?

 

[oldnslo]

Beezfun,
The attached circuit shows a possibly load holding option that would also allow the use of the "float" feature. It does require electrical signal to operate. Companies like Bucher, Hydro-Force, Delta Power, Rexroth - Oil Controls, etc. all make these Normally Closed solenoid operated valves. Just throwing out another possible option to help keep you confused

 

[Groo]

Most leakage I see is a cylinder floating up when other sections are worked hard.

If it is drifting down you are worried about, an external load holding valve might be one way.

 

[BeezFun]

I guess my point is that even with the acceptable leak rate that Bucher has, the valves DO NOT leak at that rate which is why I only sell them.

I believe you, because I've left my front loader in the air for weeks and it doesn't drift down, so somebody made this valve that doesn't leak.

And as far as your 500lb mower, you need to figure that the weight is substantially more when cantilevered out 6' from the actual cylinder rod. IT IS NOT 78psi at the cylinder.

When the tail wheel is down and I'm mowing, it would be 78psi on the cylinder. If it's cantilevered out I agree it would be a lot more. But I don't care if it leaks down when it's cantilevered because I'm not mowing.

If this is really only an issue with your mower, why not simply un-plug the rod end hose when mowing?

That's what I'm doing. But it's not just with the mower. If I'm trying to hold a back blade at a tilted angle and it leaks down/up this fast, I'll have to disconnect the hose then too. Not an impossible situation, but not what I expected.