When replacing the hydraulic cylinder, precise measurement is essential to ensure optimal performance. Proper measurement of the hydraulic cylinder is a basic skill to help you choose the right parts for your job, guaranteeing safety, efficiency and reliability. This guide will talk about the necessary measurements to ensure that you get the right parts all at once.
Measurement Tools
Before we begin, let’s gather the simple but essential tools for the job. Getting precise measurements is impossible without them, and guessing is not an option.
- Tape Measure: A reliable retractable tape measure is perfect for the larger measurements, like the cylinder’s overall length.
- Calipers: For smaller, more critical dimensions like rod and pin diameters, nothing beats the precision of a digital or dial caliper. This is the difference between a pin that fits and one that doesn’t.
Essential Components to Know Before Measuring a Cylinder
To measure a cylinder correctly, we first need to identify the key parts we’ll be looking at. Understanding what each component does will make the measurement process much clearer.
- Cylinder Barrel: This is the main body of the cylinder that contains the piston and hydraulic fluid. Its internal diameter, or bore, determines the cylinder’s power.
- Rod: The chrome shaft that extends out of the cylinder barrel to perform the work. Its diameter is critical for strength and seal compatibility.
- Piston: The component inside the barrel that is attached to the rod. It moves back and forth as fluid is pumped in, creating the cylinder’s action. While we can’t measure it directly without disassembly, its size is defined by the cylinder bore.
- Mounts: These are the connection points at each end of the cylinder that attach it to your machine. They come in various styles (like a clevis or cross-tube) and their dimensions are non-negotiable for a proper fit.
How to Measure a Hydraulic Cylinder Accurately
Now that we have our tools and know the parts, let’s get to the core of the task. These key measurements are the essential data points you will need to identify or order a replacement hydraulic cylinder. Take your time and measure twice to ensure accuracy.
1. Retracted Length (Closed Length)
The retracted length is the cylinder’s length when it is fully closed. This is arguably the most important measurement to ensure the new cylinder will physically fit on your machine. If this dimension is wrong, the cylinder simply will not mount onto your equipment’s frame and linkages.
How to Measure: With the rod fully retracted into the barrel, measure from the center of one mounting pin to the center of the other mounting pin. Do not measure from the ends of the cylinder.
2. Extended Length (Open Length)
This is how long the cylinder is when the rod is all the way out. If you have the stroke length, you might not need this measurement, but it is a great way to double-check your work. This, combined with retracted length, gives you an idiot proof way to measure your method of measuring Stroke.
How to Measure: Take this measurement from the center of one pin to the center of the other while the rod is at full extension.
3. Stroke Length
Stroke is the total travel of the rod, or the distance from fully retracted to fully extended. This is the cylinder’s range of motion. The stroke measurement is what determines how far your machine’s boom, bucket, or other attachment can move. The stroke must be matched to the original cylinder specification to retain your equipment’s correct geometry and function.
How to Measure: The most accurate way to get this measurement is Stroke Length = Extended Length—Retracted Length. That means if your extended length is 45” and your retracted length is 25”, your stroke would be 20”.
4. Bore Diameter
Bore is the inner diameter of the cylinder barrel. This measurement directly correlates to how much push/pull force a cylinder will generate at a given pressure. A cylinder with too small of a bore will be too weak, and a cylinder with too large a bore can overpower the design of your machine. Matching the bore is critical to performance.
How to Measure: You are not able to get a direct measurement of this without disassembling the cylinder. The best way of getting this number is using your calipers to measure the outside diameter (OD) of the barrel. Using this OD, you can reference a specification chart or call a knowledgeable supplier who can usually determine your bore as barrel wall thicknesses are relatively standard.
5. Rod Diameter
This is the diameter of the chrome rod that is protruding from the cylinder. Rod diameter is critical to determining the column strength(bend resistance) of a cylinder, and if you plan to rebuild, it is key to getting the correct seal kit. How to Measure: Use your calipers to get this measurement. A tape measure is not accurate enough to get your proper rod diameter.
How to Measure: Use your calipers to get a precise measurement of the rod’s diameter. A tape measure is not accurate enough for this.
6. Pin Diameters
These are the diameters of the mounting pins that hold the cylinder to your machine. Like the retracted length, this is a go/no-go measurement. If the pin holes are the wrong size, you will not be able to attach the cylinder to your equipment.
How to Measure: Use your calipers to measure the diameter of the pin holes at both the rod end and the base (barrel end) of the cylinder.
Master Your Machine with the Right Measurements
Measuring a hydraulic cylinder correctly is very helpful. It helps you avoid ordering errors and wasting money and time. You need to know what to measure, how to measure with the right tools, and record the numbers accurately. When you know how to do it, you feel more in charge of repairing your off-road equipment, and you know you can get the right parts and fix your important machine fast.
