Hydraulics for Everybody
We live in an age where hydraulic tools and equipment have never been so inexpensive. Any homeowner can now own and use hydraulic tools that previously were only available to mechanics and industrial repair shops.
Even though hydraulic equipment has never been so easy to acquire, hydraulic equipment bring dangers and risks that first time users should be aware of so they can use the equipment safely.
Hydraulic Tools - You get what you pay for
Another concern with offshore hydraulic equipment is repairs. A lot of these inexpensive hydraulic tools have no spare parts available and so when it breaks, your only option may be to throw it out rather than fix it. If its critical that your hydraulic tool be always ready for use, consider getting more than one. Or consider buying a more costly domestic unit that offers a network of easy to find spare parts.
The picture above is a good example of a complete kit of hydraulic tools. This particular kit is specifically for automotive collision work. The kit includes hand pump, cylinders and accessories. and provides the do-it-yourselfer with the same equipment normally found in a garage or body shop.
How the logsplitter valve works
Push the lever forward and the spool inside the valve moves so that the condition of the valve becomes as it is shown in the box to the left. Hydraulic fluid moves into the cylinder and forces the ram forward splitting the log. Pull the lever all the way back and the spool moves until the valve is in the condition shown by the box on the right of the schematic. In this condition the valve swaps the fluid from one port to the other reversing the flow so that the ram pulls backward so the split logs can be removed.
Welded Hydraulic cylinders are - well - welded together. These kind of cylinders are intended to be used and discarded when they wear out and start to leak.
Single acting cylinders have only one inlet or port and use weight of the object they are pushing against or a spring to push the piston back down. Single acting hydraulic cylinders are often called rams.
Double acting hydraulic cylinders have two ports at either end of the cylinder. These hydraulic cylinders require hydraulic valves to reverse the fluid flow to move the piston back and forth. A hydraulic log splitter, for example, uses a double acting cylinder.
When you buy a hydraulic cylinder you need to specify the bore, which is the diameter of the piston in the cylinder barrel. You also need to specify the stroke which is the maximum distance the piston or rod can extend.
A log splitter, for example, often uses a 3.5" Bore, 24" Stroke Double Acting cylinder.
You can also specify what kind of connections you have on the cylinder rod and at the back of the cylinder. Many offshore cylinders are sold with clevis attachments on the rod and the back of the cylinder.
Hydraulic Cylinders for sale on Ebay
Hydraulic Hand Pumps
Ebay can be a good place to look for hydraulic hand pumps. But be aware that it is impossible to judge what condition a used hand pump is in by its picture. Buy a hand pump with the understanding that you might have to get it repaired and factor that into what you are willing to bid. Ebay often features high quality units such as those made by Enerpac and Parker.
Hand pumps come in a number of different sizes. They usually vary according to oil capacity. To make sure you are getting the correct capacity, you have to know how much oil is needed to operate your hydraulic cylinder.
For example, if you have a 1" Bore, 10" Stroke hydraulic ram you can make a quick and dirty estimation of the oil volume it needs by assuming that your cylinder is actually a rectangle measuring 1" x 1" x 10" = 10 cubic inches.
For any cylinder, multiple the bore times itself times the stroke. That should give you enough oil capacity to fill the cylinder and the hose that connects it to the pump.
Hand pumps are available from 20 to 150 cubic inch capacity. There is a limit to how big a cylinder you can hook up. By calculating how much oil capacity your cylinder needs, you can avoid buying a pump that is too small.
Great Stuff on eBay
Hydraulic Hose - Putting it all together
Most hydraulic cylinders you will encounter will have National Pipe Thread (NPT) female ports. 1/4" NPT, 3/8" NPT and 1/2" NPT are quite common. Naturally you want to make sure your hose has the corresponding NPT male connection. NPT connections are not perfectly liquid tight and do require teflon tape to seal properly. You simply wrap the threads with a few turns of teflon or PTFE tape and you will not have any leaks. When you buy hydraulic hoses you may see fittings with FJIC or JIC mentioned. This refers to a small tapered area on the front of the fitting. This is unimportant if you are using the fitting to connect to an NPT female cylinder port. It is very important if you are connecting two hoses together because the tapered FJIC or JIC flare is what makes the liquid tight seal.
Hydraulics Expert Advice
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Books by Peter Rohner
I would like to make this lens as useful as possible. If there is anything you would like added, please let me know. I try to be as impartial as possible. I know I promote Ebay sales and other products on this lens but I also like to give cautions and warnings where necessary. Hopefully from my experience, others can make educated decisions.