Friday, June 27, 2008

How to measure a hydraulic cylinder

Due to the large number of requests I get, I thought I would take the time to clear up a few questions people have when it comes to how to size a hydraulic cylinder. There are MANY different configurations, and lots of people use lots of different names for the parts of a cylinder, so I thought I would try to make it a little easier.

Q: How do I find the "Bore"?
A: This is the diameter of the the piston INSIDE the cylinder tube. Larger bore = more lifting force. As a rule of thumb, Bore is approximately equal outside diameter of tube minus .5"

Q: What do you mean by "Stroke"?
A: This is the actual travel of the cylinder; Extended length (pin-to-pin centers) minus the retracted length (pin-to-pin center)

Q: What's this "Retract" mean?
A: Length, pin center to pin center, when the cylinder is fully closed.

Q: What does "ASAE" mean?
A: 8" and 16" stroke cylinders are available in ASAE and non-ASAE (Standard). All ASAE 8" Stroke cylinders are 20.25" retracted (vs 18.25" for non-ASAE) and 16" stroke cylinders are 31.5" retracted (vs 28.25" non-ASAE). Who decided this, I honestly don't know, nor do I know why, only that the ASAE cylinders have more room for adjustment.

Q: What's a clevis?
A: The most common mounting option, this consists of two "ears" on each end, with holes drilled for a pins to go through.

Q: What is a cross-tube?
A: This is a mounting option used on heavy-duty cylinders, consisting of one "cross tube" or "bushing" solidly welded to the cylinder tubing or rod end.

Q: What is a Tie-Rod Cylinder and what's the difference between it and a welded cylinder?
A: Tie-rod cylinders are the most common on agricultural applications. The "tie-rods" are the 4 long bolts or rods that run the length of the cylinder, holding it together. These are the most economical and easiest to rebuild, but have more interconnected parts, which gives it more possible places it could leak. Welded cylinders are much more robust, with fewer parts and larger rods which are much less likely to bend under excessive forces. Welded cylinders are also much more difficult to repair in the field.

Q: Will your cylinder will fit my 1972 FARMCO WHIRLI-MA-GIG-AMA-BOB?
A: I don't know, I don't work for them. Using the above info, please measure it a I'll see what I can do!

If you have any questions about hydraulic cylinders email me @


SieskoNators said...

Thank you for the information, it was very helpful!

SieskoNators said...

Thank you for the information, it was very helpful!

Kelway said...

Thanks, I'm glad to be of assistance! Comments and questions are always welcome.

Lavonne said...

Well said.

fccu said...

Great post!! Thanks for sharing.. :D

Anonymous said...

my wood splitter is leaking fluid from around the hydraulic cylinder shaft. can I purchase the seals/gaskets for this item?

Kelway said...

Sorry so long to reply! We usually can't really get seals for cylinders that aren't ours.

Charley said...

What I see here is very helpful, however I need to be able to dertemine the head dimensions of a 5" bore tie rod cylinder for machine design/clearance purposes (centerline location of the cyslinder is critical). I can guess at the tube od as being 5.5 inches diameter but have no way to know the head dia. I'm guessingperhaps 6.5 square --how close am I?