Wagner hidraulyc cylinder capacity

[pr2501]

What is the cilynder capacity illustrated on image below. Cylinder is 25 long and 5 cm of diameter.
I took also some measurements and marked them with blue color on last image. There it results 127 cubic cm. But I think that it is more.

[Chotu]

(PI*R^2) x h

R=2.5cm
h=25cm

R^2=6.25

PI*6.25=19.6

19.63*25=490

490 cubic centimeters, 16.5 fluid ounces, 1 pint, half a quart, half a liter.

[DougR]

Seems to me there are several issues here:
- The calculations shown which were done with the tape measure dimensions relate to the outside dimensions of the cylinder, but not the inside dimensions. This will make a small percentage difference in volume.
- The cylinder shown on the Wagner data sheet is a balanced cylinder, and Wagner has deducted for the volume which the piston and piston rod take up. This is why their numbers are smaller than what you think they should be. Also ,
The volume of the cylinder will not change regardless of the position of the piston rod.
- The cylinder which you show in your picture is a non- balanced cylinder. That means the steering will not be equal to port or to starboard, and the volume of the cylinder will vary depending on the position on the piston rod, because there is more or less of the piston rod inside the cylinder.

DougR

[pr2501]

DougR
The Wagner data sheet says 127 cubic cm
The matematica result is 400 cubic cm.
How can be there so big the difference?

[pr2501]

I am asking because I need to find out how big autopilot pump do I need. The broken one is PF 1.0 power pack.
I have to choose between RPU80 or RPU160.

[DougR]

Originally Posted by pr2501

DougR
The Wagner data sheet says 127 cubic cm
The matematica result is 400 cubic cm.
How can be there so big the difference?

As I alluded to in post #3, you aren't comparing apples and apples, and that is why there is so much difference between the two figures. Here is what I mean:
- The Wagner N40-120 cylinder is 10" long and 2" outside diameter, but the end fittings on the Wagner screw into the body of the cylinder which reduces the internal volume by at least 1.25" on each end, which means the internal length of the cylinder is maybe 7.5" long.
- The wall thickness on the Wagner cylinder is at least 1/8", which means the internal diameter is only 1.75".
- The piston rod on the Wagner cylinder is either 5/8" or 3/4" in diameter, and runs straight down the length of the cylinder, in one end and out the other, which reduces the internal volume by that much.
- The internal piston which is mounted on the cylinder rod carries two cup seals and a bearing sleeve, and is at least 1.5" long and attached to the piston rod, again decreasing the internal volume.

The cylinder which you show in your pictures has about the same external dimensions as the Wagner, and the volume calculations which were so kindly made by Chout are based on those outside dimensions. But these calculations don't consider any of the items which are listed above.....such as the volume of the piston rod, or the piston itself, or how the end pieces fit into the cylinder, etc.

So the 400 plus/minus cubic cm volume stated is really a very rough estimate of the actual cylinder volume of the cylinder. To get an accurate volume you need to contact the cylinder manufacturer or measure the liquid volume or open the cylinder up and actually measure all the parts and calculate everything.

Hope this explains better what I meant earlier.

DougR

[pr2501]

Type N40-1 - Wagner Engineering Ltd.
With diagram in link abowe I can understand why then the oil volume is 127 cubic cm.

Actually I should already say before why I am looking for this info. I need it for dimensioning of autopilot pump.