Ever had a hydraulic crane (recognizable as a engine hoist) that's been sitting in your basement or garage for years? Have you ever been just laying around on the weekends looking for something to do; and the first question peculiarly applies to you? If one or both of the previous questions relate to you, stay tuned. In this instructable, we discuss converting a once hydraulic crane into a fully functioning pneumatic crane. If you are tired of dealing with the oil in a hydraulic system, just recently moved to a pneumatically supported warehouse/shop, or are just simply interested in the process; the following article outlines the steps to convert your crane.

My name is Sara Barnett, and I will be walking you through the process. I am a junior Technical Director student at the University of Cincinnati College-Conservatory of Music, and this transformation is my Final Project for "Pneumatics for the Theater" class, Fall 2015. Please view the school site if you are interested in finding out more information or joining us here at CCM.


Step 1: Attain Your Hydraulic Crane and Materials

If you have the same same crane that I worked with on my project, (Ruger Model HP-18A) then after having rolled your crane onto an inconsequential floor, you'll want to gather lots of kitty litter and rags for a potentially messy beginning.

Before you start to take the hydraulics off of the crane, you'll want to gather a few items. They are listed as follows:

For Dis-assembly

1. Kitty Litter

2. Scott's Rags (or any towels fit for grease clean up)

3. Hammer to help motivate old or stubborn parts i.e. cotter and clevis pins

4. Two (2) Buckets, one (1) to catch excess oil spill, one (1) to store cotter and clevis pins

5. Knife to cut hydraulic components from crane

6. Assortment of large wrenches

7. Blocks, or something to that effect, to rest the front of the crane on to reduce movement while working

For Assembly:

8. New Pneumatic Cylinder - specific cylinder used for this project found in step 3

9. 2½" x 2½" Base bracket clevis - size to cylinder rear end cap (also known as the rear pivot mount or cap clevis)

10. ¾" Diameter bore rod clevis - size thread to cylinder piston

11. ¾" Nuts - Coarse or fine depending on cylinder piston threads

For Pneumatic Powering

11. 5:3 Pneumatic Valve

12. ¼" and ½" Pneumatic Hose Tubing

13. Two (2) Adjustable, Free Reverse Flow, Flow Control Valves

14. Modular Air Regulator

15. Teflon tape

16. A variety of ¼" and ½" nipples - specific to valve and cylinder choice

Step 2: Strip the Crane of All Things Hydraulic

Next you want to rid the crane of all things that are hydraulic. After having done this, your crane should look like the first picture, above. Before you take any steps in stripping the hoist, drain as much oil as you can. This will help create less of a mess when taking everything off. As you start to take off the hydraulics remember to use the kitty litter to soak up any oil that is spilled.

In order to take off all of the hydraulic elements, you will need to start off by getting rid of the hose. Be aware when doing this that the hose is not completely rubber and can have a wire interior. With that in mind, choose a knife you do not care about and discard the hose as it comes off. Once all the hose is detached, remove the cylinder from the crane. To do this, you have to undo the cotter and clevis pins at the bottom and top of the cylinder. As you take out the last set of pins, keep a hand on the arm lever - as the cylinder will no longer be holding up the arm and it can swing back. Once the cylinder is free, it too can be thrown away or recycled. Be sure to keep the clevis and cotter pins as they can be reused in the future.

Step 3: Incorporate Pneumatics: Cylinder

Just as with the hydraulic system, incorporating pneumatics will require a cylinder. The cylinder chosen for this project is a Motion Controls D 30 SE DC SL36 RA1. This cylinder has a 2" Bore, cushions on both sides, a male 36" threaded stroke, and no front or rear mounting options incorporated with the cylinder. For ease of application, I placed the pneumatic cylinder in the same spot as the hydraulic cylinder.

Upon replacing the hydraulic cylinder with a pneumatic one, it became apparent that the seals in the pneumatic cylinder needed to be replaced. Being that the seals keep air from leaking out of the system, and can effect the cylinder life, it is important to have properly installed and functioning seals. When ordering new seals, I went to the cylinder manufacturer Motion Controls and ordered a full D series seal kit (pictured above). When replacing seals (if that is necessary to continue) it is important to keep the seals clean. Not only should you watch for dirt and small debris on the seals but you also want to make sure that there is nothing in the cylinder that could get in the way or harm the piston and seals. Once all the seals have been replaced, use the regulator or connector and pneumatic hose to cycle the cylinder and make sure nothing seems to be out of place. A link to Motion Controls' how-to on seal replacement is as follows: http://motioncontrolsllc.com/accessory/d-series-maintenance

To cycle the cylinder you want to first pressurize the system. To do this, you should start with positioning the cylinder with the piston retracted. Connect your hose to the regulator or the air source coupler nipple. Afterwards insert your ¼" or ½" hose into the nippled inlet nearest the piston top. As air flows into the cylinder you are pressurizing the system. Once the system is pressurized, take the air out of the front nipple and insert the hose into the back of the cylinder. This should pressurize the cylinder and extend the piston. To keep the cylinder from moving have a friend hold it down or affix it to a work table as you do this first test. If a valve or flow control is not incorporated in the cycle of the cylinder, then your air source will provide a full, steady, and non-stop flow of air to the cylinder. Be careful with this as you do this not to pressurize the system too much. Be sure to stop the flow into the cylinder if and when it starts to sound full. The structural integrity of the cylinder should be enough to handle an increase in pressure and you should not be afraid of the cylinder exploding. However, the hose going from the regulator to cylinder is not as reliable as the cylinder itself. If the system is too pressurized then the hose will be the first to give, and blow itself out of the nipple it was in. Know that this is a possibility at all times during this process if conscious metering of the air isn't taking place. From now on, wearing eye protection is not necessary but recommended especially if the air is not regulated.

Step 4: Build/Affix Clevises to Cylinder

Depending of the type of cylinder you have purchased, the mounting hardware (clevises) differs. Working in a metal shop or an educational setting offers many advantages especially when it comes to having extra hardware such as clevises. That being said, all is not not lost if you do not have one available to you; as you can either purchase one or simply make it. Pull the dimensions off both your cylinder and crane hoist to know what size to look for. Before you take the time to create your own, or if you don't have the means to, look through the following cite for the clevis you might need. http://www.mcmaster.com/#clevises/=106ysrm

If you are unable to find the right size that's needed in stores or online, you can make one. As I was unable to find appropriate clevises, I created both the top (rod) and bottom (base bracket clevis). Above you can view the dimensions of the rod and base bracket clevises that I created, produced via AutoCAD. As seen with the design of the hydraulic crane, both clevises had to be able to pivot to accommodate for the change in movement along the plane. Taking this information and the cylinder size, you can fashion a new clevis to mount your cylinder. For this project, the bottom of the cylinder is a 2½" x 2½" square with four (4) threaded holes in the corners to compress the clevis to the cylinder. This build is mimicked in my rear pivot's base. Just as the hydraulic cylinder was, the bottom of the pneumatic cylinder will be at the base of the crane. The crane offers a tongue with a ¾" hole it for a clevis and cotter pin. Work with this premade aspect and build around it. Using the base of the rear pivot that was just created, you can weld two (2) flat plates of ⅛" steel with a ¾" hole in them. The holes should be in line with where the crane has it's. A ⅞" space in between the two (2) plates of steel should be incorporated in the build of the base bracket for the crane's tongue.

For the top of the piston, you can create either a traditional rod clevis, or a U shaped clevis with a ¾" hole in it for the piston. If you choose the U shaped clevis instead of creating a traditional one, there should be a nut both on top and bottom of the steel to hold it in place on the piston (see the 2nd to last picture).

Once both clevises are made, affix them to onto the cylinder. The rear end clevis should be bolted (size relative) to the cylinder's end cap and the rod clevis will be compressed into position (see last picture).

Step 5: Provide Air to the System

And finally, the last step! Attach the cylinder to the crane via the clevises (First 2 pictures). Find the cotter and clevis pins that were set aside to make this connection. Once the cylinder is attached to the crane, to pneumatically motivate it you must gather the following objects:

5:3 Pneumatic Valve (Third picture)

2 Flow Control Valves

¼" Pneumatic Hose

Multiple Nipples ranging from ¼" to ½" - Use depends on cylinder

Regulator (Fourth picture)

Once all of this is gathered, reference the schematic (last picture) on how to wire up the hose. The hoses coming from the cylinder will go into the valve's two supply ports (labeled as 1 and 2 in pic. 3). Before you attach any active air supply to the valve, make sure that it is in the neutral state. The neutral state stops air flow into and out of the cylinder, causing the movement to "pause" until the state changes. Most valves have at least 2 states - those being exhaust and supply. However, being a 5:3 valve, we know that the valve has 5 ports and 3 states. With the third state you have the option of feeding air to neither the exhaust or supply, thus closing the system. Without the third state you lose the ability to do so.

After having inserted the hose into supply nipples 1 and 2, you can wire up the exhaust. To do so, you insert any free hose into the valve's exhaust ports (labeled at 3 and 5 in pic. 3). Once the exhaust hoses are inside of the value you can apply the flow control to the other end of the hose.

To adjust speed in any pneumatic or hydraulic system you have to meter the exhaust. In our system and most others, metering the exhaust is done with a flow control valve. Restraining the flow creates a slower movement from the cylinder. And so, without any constraints the cylinder moves as fast as gravity, the air supply, or the force allows. If speed is what you want to adjust as you are moving the cylinder, meter the flow control.

Once the wiring of the cylinder and flow control is set up, connect the regulator (picture 4) to the port labeled 4. With the regulator you can adjust how much pressure the cylinder is receiving. As we don't want any accidents to happen - it's important to adjust the regulator reading to lower than you would expect when cycling through the system for the first time. Once the system has been cycled a few times, adjust the flow control and psi to manipulate the cylinder. And with that you are completely wired up and ready to go.

Step 6: Let's See It Move

And there you have it! You just created a pneumatic crane from a once hydraulic engine hoist. Congratulations!! I and others at CCM wish you the best of luck with your instructable endeavors and encourage you to look at some of our other step by step projects. Check us out on instructables under the name: University of Cincinnati CCM Pneumatic Projects Fall 2015, or search CCM. I hope you have fun with you're new crane/hoist!

With absolutely no flow control and as much psi as our shop can offer, here is a short clip of the now pneumatic crane moving up and down - mostly because everyone likes to see things go as fast as possible!


Sara Barnett

Junior Year Technical Direction Major

University of Cincinnati College-Conservatory of Music.

<p>Really cool! How much can your new pneumatic crane lift? </p>
<p>Thanks tomatoskins! At around 125 psi, it can lift about 75 lbs and hold about 135 lbs. </p>
Hate to be the person to rain on the parade...but<br><br>Using pneumatics to lift heavy loads is extremely dangerous. If something jams or you try to lift more than your available pressure can lift, you end up with a compressed spring. Should the jam free itself, and the pressure is still in the cylinder, the arm will lift almost instantly and could seriously injure or kill someone.<br><br>The only way to reduce the risk is to add a flow regulator (ideally 2 in line for redundancy) to limit the speed of the cylinder actuation.<br><br>There is the reason we tend not to use pneumatic cylinders with high loads.
<p>no reply to that statement huh ? I sure hope it means the author took it on board and went back to an incompressible medium for cylinder pressure. Although just seeing the Ruger hoist is food for thought ! However air is deadly for the hoist if used by the uninformed person. </p>

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