Can two hydraulic cylinders of two different sizes, be plumbed together?

[Bigshooter81]

If they are acting in unison on the same mechanical function or leg?

I have a constraint that only allows for a certain length of retracted cylinder, but at the same time require more of a radial arc than one cylinder can provide on it's own, if I add a linkage, and change the directions of the push/pull, I can add a second cylinder, but am not sure how the function of two potentially different sized hydraulic cylinders will act on the same circuit.

Thanks.

 

[4570Man]

The big cylinder will fully extend before the small one moves because the larger cylinder requires less pressure to lift the same load.

 

[Bigshooter81]

The big cylinder will fully extend before the small one moves because the larger cylinder requires less pressure to lift the same load.

And the same way when retracting?

Otherwise no issues, as long as the meet or exceed pressure ratings?

Will the system be only as strong as the weakest cylinder then I'm guessing?

if they are both the same bore and rod size, but different stroke length will the move in unison until one reaches full extension?

Thanks.

 

[aircommuter]

The small one will extend first because it takes a smaller oil volume. If you are trying to use them together like on a loader you will bend something most likely. Retracting force varies with piston size and rod size. It is all based on the square inch displacement, multiply by by psi and you have the force.

 

[bigdeano]

Post #2 is correct. If they're both the same size either one could move first, no way to tell without trying it.

 

[mkr7734]

Post #2 is correct. If they're both the same size either one could move first, no way to tell without trying it.

Best answer,,,, not a good idea, they will never work in sinc.

 

[aircommuter]

How about a sketch of what you are doing, then we could help more.

 

[bcp]

They will work together, each to their best ability, it they are mechanically forced to, like this diagram of a boom.



If they can operate independently, like this lift platform, they won't lift evenly.



Bruce

 

[Bigshooter81]

The small one will extend first because it takes a smaller oil volume. If you are trying to use them together like on a loader you will bend something most likely. Retracting force varies with piston size and rod size. It is all based on the square inch displacement, multiply by by psi and you have the force.

Not like a loader. they will be inline with one another, operating a single articulating "dump/curl" mechanism so to speak.

 

[bcp]

Not like a loader. they will be inline with one another, operating a single articulating "dump/curl" mechanism so to speak.

Functioning something like this, mechanically?

Bruce

 

[Bigshooter81]

Functioning something like this, mechanically?

Bruce

View attachment 471028

Yes! Thank you for taking the time to provide that..... I am not skilled at drawing, and worse, posting pics.

Thanks.

The function is not for pushing, but for pulling the larger cylinder will have far less leverage, and the smaller more so there shouldn't be any issues with over stressing the cylinders.

 

[bcp]

Yes! Thank you for taking the time to provide that..... I am not skilled at drawing, and worse, posting pics.

Thanks.

The function is not for pushing, but for pulling the larger cylinder will have far less leverage, and the smaller more so there shouldn't be any issues with over stressing the cylinders.

Sounds more like this diagram:



Bruce

 

[Bigshooter81]

Sounds more like this diagram:

View attachment 471030

Bruce

Swap the cylinders around, but maintain the leverage points and yes, exactly.

 

[bcp]

Something to consider is to arrange the leverages to not use the cylinders together.

The boom will be hardest to raise when more horizontal. This is when it would be an advantage to use the larger cylinder alone. As the boom reaches, say, 45 degrees, the large cylinder is at the end of the stroke, and then the smaller cylinder continues the lift.

Bruce

 

[aircommuter]

I do not see the need for 2 cylinders in that situation , just tilt that post back and make it rigid. When the angles change so does the leverage. To use them like that you need separate valve control or you have a priority situation where you actually may go down instead of up because of load changes. Backhoes for example have different pressure relief settings for different cylinders because one may over stress another and break a hose or worse.

 

[Bigshooter81]

Something to consider is to arrange the leverages to not use the cylinders together.

The boom will be hardest to raise when more horizontal. This is when it would be an advantage to use the larger cylinder alone. As the boom reaches, say, 45 degrees, the large cylinder is at the end of the stroke, and then the smaller cylinder continues the lift.

Bruce

Yes the smaller cylinder will be used with 20 degrees either side of vertical, and the larger from 20 degrees to beyond horizontal.

so hopefully because the bottom of the stroke will be beyond horizontal, and the smaller will have far more leverage, there won't be an issue.

 

[Bigshooter81]

I do not see the need for 2 cylinders in that situation , just tilt that post back and make it rigid. When the angles change so does the leverage. To use them like that you need separate valve control or you have a priority situation where you actually may go down instead of up because of load changes. Backhoes for example have different pressure relief settings for different cylinders because one may over stress another and break a hose or worse.

I need 17" of total stroke, but don't have enough room to install a cylinder with that kind of retracted length. Otherwise I would definitely prefer one cylinder. The smaller cylinder will have priority as it will leverage almost 3 time the push/pull poundage as the larger cylinder.

 

[bcp]

If you don't need down force, maybe a stroke-doubler cable and pulley system would work.



Bruce

 

[Bigshooter81]

If you don't need down force, maybe a stroke-doubler cable and pulley system would work.

View attachment 471033

Bruce

If I was purely lifting that would work, but the needed movement is a radial curl, and in a very compact area.

 

[Luke'sScreenName]

What about when retacting the cylinders? Could the larger one pull the rod or damage the packing of the smaller one?