Design guidelines for custom hydraulic cylinder

[Borealis]

We've got a little design task here. After looking at the options and the constraints involved with a module that installs in another machine, we're thinking about designing our own custom hydraulic cylinders--roughly 2.5" diameter, but with a short stroke, only about 1/4". The standard off-the-shelf Parker compact hydraulic cylinders won't integrate cleanly. Even though it's a pain, it looks like things will package best if we machine the bores right into some other components.

We've made plenty of custom pneumatic cylinders but never hydraulics. Searching online, I can't find much info for hydraulic cylinder design guidelines. If we're operating at 1000 psi, is there any magic involved with seal selection beyond the Parker o-ring/seal handbooks? It's going to see a lot of cycles, about 5 million per year, so longevity is a concern, too. It's ok if the customer has to spend 2 hours changing seals every million cycles, but the metal needs to last a lot longer. Can we do this in polished steel bores, or do we need to get everything hard-coated?

It'd be great to get some input/advice from someone who's been here before.

 

[atex57]

When you say " won't integrate cleanly. " is it length, diameter, mounting, other?

There are many types beyond Parker tierod style.

What makes your application unique?

Ed.

 

[kustomizer]

Were it me, I would like the shaft as long as possible with the piston in the middle allowing a bushing on both sides of the piston to keep it from wobbling. Even a short bushing might be better than none.

 

[Overland]

One of the rules of brainstorming is that there is no bad idea, because it might stimulate a better idea.

On that note, you can buy honed tubing, by the foot:
Honed Tubing Supplier | Pre Honed Steel Tubing | Hydraulic Cylinder Tube Distributor

Maybe you could buy a standard cylinder, keep some of the components, glands, rod ends, etc, then incorporate this into your existing components.

Can't really visualize what you are trying to do.
Bob

 

[Borealis]

When you say " won't integrate cleanly. " is it length, diameter, mounting, other?

There are many types beyond Parker tierod style.

What makes your application unique?

Ed.

We're trying to pack 10# of shit in a 5# bag. That's the basic problem; haven't found any OTS cylinders that pack as tight as we need. On the other hand, the models show that everything would fit pretty well if we machine the cylinders directly into some other parts of the system.

One of the rules of brainstorming is that there is no bad idea, because it might stimulate a better idea.

On that note, you can buy honed tubing, by the foot:
Honed Tubing Supplier | Pre Honed Steel Tubing | Hydraulic Cylinder Tube Distributor

Maybe you could buy a standard cylinder, keep some of the components, glands, rod ends, etc, then incorporate this into your existing components.

Can't really visualize what you are trying to do.
Bob

I like the idea of parting out somebody else's piston-rod-seal assembly and installing it in our custom cylinder. Thanks.

 

[Bill D]

Look at the little pancake style short hydraulic cylinders used for porta power units to steal some ideas.
Bill D

Link is to some company with nice photos
Cylinders - HVL, HPS, HLS Range | Hi-Force Hydraulic Tools

 

[metalmagpie]

Look at a Hercules catalog.

 

[McClure Machine]

We've got a little design task here. After looking at the options and the constraints involved with a module that installs in another machine, we're thinking about designing our own custom hydraulic cylinders--roughly 2.5" diameter, but with a short stroke, only about 1/4". The standard off-the-shelf Parker compact hydraulic cylinders won't integrate cleanly. Even though it's a pain, it looks like things will package best if we machine the bores right into some other components.

We've made plenty of custom pneumatic cylinders but never hydraulics. Searching online, I can't find much info for hydraulic cylinder design guidelines. If we're operating at 1000 psi, is there any magic involved with seal selection beyond the Parker o-ring/seal handbooks? It's going to see a lot of cycles, about 5 million per year, so longevity is a concern, too. It's ok if the customer has to spend 2 hours changing seals every million cycles, but the metal needs to last a lot longer. Can we do this in polished steel bores, or do we need to get everything hard-coated?

It'd be great to get some input/advice from someone who's been here before.

I build and modify hyd cylinders on a daily basis. I can help you with your design for you to build or I can build it for you.
If you can shoot me a email I can give you my number. way to many questions and parameters to answer on here
[email protected]

 

[Kevin T]

I think you are on the right track working with the Parker Design Guide. From Parkers POV I don't think there is much difference in the basic design of the dynamic seal. The material selection is critical and then if the material is dangerous or you dealing with very high pressures there are more factors to deal with.

I would search for "best practices" or "design considerations" for a piston or gland seal with the medium you are using. Just knowing the cycles your product will see should give you a heads up to talk to Parker directly and get good advice IMO. I designed a few over the years but always for non-destructive test purposes so I never had to consider "cycles".

EDIT: (had some time to geek on considerations for cycles) I found this.

..."Surface Finish for Dynamic Grooves
Straight-sided grooves are best to pre-
vent extrusion or nibbling. Five degree
sloping sides are easier to machine
and are suitable for pressures up to
1500 psi. (100 bar). The rubbing sur-
faces should be 8 to 16 RMS without
longitudinal or circumferential scratches.
Best surfaces are honed, burnished, or
hard chrome plated. Finishes of
dynamic contacting surfaces have a lot
to do with the life of the O-ring seals.
Appropriate surface finishes are impor-
tant. Limits of maximum roughness for
glands are given. Rougher finishes will
cause excessive wear. Finer finishes
reduce lubrication to the O-ring and
may result in stick slipping and irregu-
lar wear. Surface roughness values
less than 5 micro inches (0,15μmRa)
are not recommended for dynamic O-
ring seals. The surface must be rough
enough to hold small amounts of oil.
Finishes below 5 RMS wipe too clean
for good moving seal life.
Steel or cast iron cylinder bores are
preferred. They should be thick
enough not to expand or breathe with
pressure, otherwise the radial clear-
ance gap may expand and contract
with pressure fluctuations-causing
nibbling of the O-ring."...

from https://o-ring.info/en/technical ma... manual - o-ring gland design information.pdf