Backblade upgrade!

[npalen]

I may have missed it, but has anyone mentioned a crossover relief valve to prevent over-pressure if you hook the end of the blade? If the pressure in either line exceeds the relief setting it momentarily dumps to the other line, preventing a dangerous situation.
Once the pressure goes back to normal levels, the valve closes again and normal operation resumes

I can see the crossover relief working if the cylinder is being forced to extend. In a situation where the cylinder is being forced to retract, however, the volume of oil in the base end of the cylinder being greater than in the rod end would actually intensify the pressure. Right?

 

[Buggs67]

Relief valve: $88 at ZORRO

Prince Double Relief Valve, 3/4 In NPT Port DRV-2HH | Zoro

Order Prince Double Relief Valve, 3/4 In NPT Port, DRV-2HH at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

I haven't found an electric diverter valve yet for hydrulic pressures.

 

[LD1]

Cross over relief only protect if cylinder is trying to extend. Not a good thing to rely on...it is best to just size cylinder appropriately.

 

[Kschwennsen]

Adding a lever for the driver to pull from the seat for sliding a lock pin might be a good idea as well. I just get off and move mine if needed to change the angle though...

 

[MHarryE]

This is the 3.5" cylinder from my skid steer snow blade. This was a very heavily built blade but had only a single cylinder. Since this happened I found most snow blades I've looked at have 2 single acting cylinders. This blade was designed so when plowing toward the right (most frequent) the cylinder was extended, and most of my snow plowing is fully angled. Last January I was finished my last pass, was waiting for garage door to open and looked at the blade area and saw the spray of oil. Tracing back, I saw where I hit a frozen chunk along the edge and it ripped the cylinder end apart. It was at the end of its stroke so hoses were protected but mechanically, it was toast. The chunk I hit was not enough for me to even notice or to sway my CTL which does not have very good tractive effort on ice - but it does have 4 ton of momentum.

 

[ovrszd]

Relief valve: $88 at ZORRO

Prince Double Relief Valve, 3/4 In NPT Port DRV-2HH | Zoro

Order Prince Double Relief Valve, 3/4 In NPT Port, DRV-2HH at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

I haven't found an electric diverter valve yet for hydrulic pressures.

I think this is the one I used from Surplus Center.

Selector Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com

Selector Valves,Hydraulic Valves,Hydraulics, DOUBLE SELECTOR Unused old inventory. GRESEN DS-12 double selector valve. When

www.surpluscenter.com

 

[CADplans]

I may have missed it, but has anyone mentioned a crossover relief valve to prevent over-pressure if you hook the end of the blade? ,,,,,,,,,,,,

IMHO, the OP DOES NOT want a crossover relief valve,,,

OCD was mentioned, think how crazy he will get when EVERY time he uses the blade, the blade rotates on its own.
The pressure on the cylinder will easily surpass the ~2,000 psi setting of the relief.
When the bypass pressure is reached, the blade simply rotates.
You are looking back, the blade is rotated "right"
Hit a minor "snag", and the next time you look back, the blade is rotated "left".

The cylinder will easily work at ~4,000psi, maybe even 6,000psi.
I used to specify cylinders,
the company that made them stated the minimum safety factor they designed to was three to one.
If the working pressure was 2,000psi, the cylinders were designed to survive 6,000psi.

I think it will surprise you to find out how easily that cylinder will go to 6,000psi.

 

[mcfarmall]

I may have missed it, but has anyone mentioned a crossover relief valve to prevent over-pressure if you hook the end of the blade? If the pressure in either line exceeds the relief setting it momentarily dumps to the other line, preventing a dangerous situation.
Once the pressure goes back to normal levels, the valve closes again and normal operation resumes

There is mention of a crossover relief in post #35.

 

[ForestGrump]

i used a similar setup with a Progressive Automations electric actuator, 2000# load with a 3000# static load. It worked fine till the end piece, which is made of cast aluminum splattered. They are sending me a new end piece, which I have to pay for, and I am going to reinforce with steel backing plates. I am also going to use soft 1/2" bolts for the mounting so one will shear vs breaking the actuator. I wsas using grade 8 which bent.
I do not understand how an aluminum casting can withstand a 3000# load and as the photos show it cant.

 

[LD1]

When the bypass pressure is reached, the blade simply rotates.
You are looking back, the blade is rotated "right"
Hit a minor "snag", and the next time you look back, the blade is rotated "left".

Not quite. The crossover on a DA cylinder will only allow it to rotate one way on its own without operator input

 

[CADplans]

Not quite. The crossover on a DA cylinder will only allow it to rotate one way on its own without operator input

,,,,,,,,,,, depending on lots of factors, like air in the system, and whether this high pressure can get oil past the piston seal of a $99 cylinder .

Even at that, OCD will not allow one to have any rotation of that blade, one direction, or not,,

 

[LD1]

,,,,,,,,,,, depending on lots of factors, like air in the system, and whether this high pressure can get oil past the piston seal of a $99 cylinder .

Even at that, OCD will not allow one to have any rotation of that blade, one direction, or not,,

Sure, if there is air in the system can cause a little blade movement. But a proper functioning system wont have air in it, only oil. And it dont matter if its a $99 cylinder or a $999 cylinder.....oil cannot move past the piston if the rod is trying to retract. Not even a little bit. A crossover will only protect when trying to extend the cylinder....but that creates another problem....you are sucking air in the gland seal. Air and god only knows what other contaminates and dirt/dust/water.

A crossover is designed for something with equal displacement, like a double rod cylinder, or a pair of equal sized single acting cylinders...or like trying to run a hydraulic motor with high inertial load off a tandem center valve and not a motor spool.

 

[npalen]

Sure, if there is air in the system can cause a little blade movement. But a proper functioning system wont have air in it, only oil. And it dont matter if its a $99 cylinder or a $999 cylinder.....oil cannot move past the piston if the rod is trying to retract. Not even a little bit. A crossover will only protect when trying to extend the cylinder....but that creates another problem....you are sucking air in the gland seal. Air and god only knows what other contaminates and dirt/dust/water.

A crossover is designed for something with equal displacement, like a double rod cylinder, or a pair of equal sized single acting cylinders...or like trying to run a hydraulic motor with high inertial load off a tandem center valve and not a motor spool.

The "oil cannot move past the piston" is probably one of the most understood principles in hydraulics. To help visualize, think of a cylinder with a rod but no piston. Try to push the rod into the cylinder full of oil with both ports blocked. Might say, "ain't gonna happen".
The rod, in the above scenario, is basically a piston with bad seals.

 

[LD1]

The "oil cannot move past the piston" is probably one of the most understood principles in hydraulics. To help visualize, think of a cylinder with a rod but no piston. Try to push the rod into the cylinder full of oil with both ports blocked. Might say, "ain't gonna happen".
The rod, in the above scenario, is basically a piston with bad seals.

Yes, it is very well understood by many.

However, here in TBN it is VERY frequently misunderstood. Especially when it comes to a loader drifting down.

 

[4570Man]

Yes, it is very well understood by many.

However, here in TBN it is VERY frequently misunderstood. Especially when it comes to a loader drifting down.

A leaky cylinder seal can’t be the sole cause of loader leak down but it will make the problem worse. A leaking piston seal will cause increased pressure in the cylinder due to less surface area and it would have to loose less fluid to leak down.

 

[npalen]

Yes, it is very well understood by many.

However, here in TBN it is VERY frequently misunderstood. Especially when it comes to a loader drifting down.

Yes, I meant to say "misunderstood". My bad.

 

[npalen]

A leaky cylinder seal can’t be the sole cause of loader leak down but it will make the problem worse. A leaking piston seal will cause increased pressure in the cylinder due to less surface area and it would have to loose less fluid to leak down.

Can you elaborate on this? Where would the lost fluid go? I can see what you're saying if you mean it is leaking past the valve spool.

 

[4570Man]

Can you elaborate on this? Where would the lost fluid go? I can see what you're saying if you mean it is leaking past the valve spool.

It could be leaking on the ground somewhere either from the gland seal or a hose. But assuming that’s not happening it goes back through the valve.

 

[LD1]

Yes, I meant to say "misunderstood". My bad.

Yes, on TBN its is pretty misunderstood. But outside of TBN....just about everyone I have ever dealt with regarding cylinders and hydraulics in general that work in the field understand. I do not understand why it is so misunderstood on TBN, and why bad info and advice continues to be spread.

 

[LD1]

A leaky cylinder seal can’t be the sole cause of loader leak down but it will make the problem worse. A leaking piston seal will cause increased pressure in the cylinder due to less surface area and it would have to loose less fluid to leak down.

Yes, a worn cylinder will exaggerate the root cause of the issue, rather than be an external leak or an internal valve leak. But its not uncommon to have other symptoms along with it. Such as weak lift.

At the end of the day, it is really simple to test the components. But too many people just throw parts at it and hope for the best. Id rather take time to troubleshoot and fix what is needed, rather than replace parts that might be perfectly fine