Syringe Hydraulic Arm PDF – Download in PDF Format
Like working with gears, pulleys, or levers; a mechanical advantage can be realized by using different size cylinders on the end of the hydraulic connections. By trading distance moved with the amount of force the advantage is realized.
|Moving the larger cylinder between 1 mark moved the smaller cylinder 2 marks.||Hydraulic cylinders for lifting and tilting bucket are easily seen in this tractor my father constructed.|
The story of my father’s company Champall Manufacturing in a 25 minute video. I created this several years ago as a DVD, not the best narration but an interesting story.
History of Champall Manufacturing – Link to YouTube video
Testimonial to Popularity of the Project
Sandy Gady 7th and 8th grade Math,Science, Design and Engineering teacher
“I have done the hydraulic arms with the syringes, they are so cool it’s beyond description. I used to do them when I taught 6th grade in a small town. We had lots of retired people with saws, so they would cut up the wood we needed. I then enlisted several of them to come into the classroom and we taught kids how to use drills, screwdrivers and hammers to assemble the finished project. In the end, they had a hydraulic arm that moved in three directions. I’ve had contact with some of these students since, and many of them still have their hydraulic arms 20 years later. They still beam with pride when they talk about them. Cost of materials, about $5.00. Educational value, priceless”.
|FuelMyBrain kids built a slightly different version of the hydraulic arm.||Large flat container was used to hold water to fill the hydraulic arms.|
I used one flat washer on the pivot point of the gripper part of the arm, not sure it is needed.
|8/32 Machine screws were used to hold clamps on and for pivot points.|
|I used these copper plated ½” tube straps to fasten the actuators (syringes) to the wood.||
The upright part of the arm is a furring strip. This inexpensive wood is used when installing drywall.
The base can be made from scrap boards also, best to pick out the better boards as some are warped. This board was labeled as 1” x 6” but true dimension was smaller.
Making Up the Parts
Normally I am making up kits for a class, so I will get all the parts fabricated first. That way few tools are needed to complete the project and it is safer for them not having to use saws or drills.
|Straighten the bend in the straps with a pliers.||The straps should look like this after 90 degree bends have been removed.|
|Cut the furring strip to 8 ½” in length.||Cut the 5/8” square stock to 11” in length.|
|Cut 1” from both ends of craft stick, the ends are used for building gripper parts and the center is used to connect syringe to pushrods.||
|Drill holes for bearing pieces on the boom, I drilled both pieces together.||Bearing pieces after drilling the two holes at once.|
|Drilling the two holes on boom to mount the actuator (syringe). There is also a hole at the far right that is
the pivot for this portion of the arm.
|Drilling hole at end for gripper assembly, this is drilled 90 degrees from the other holes.|
|Hole for strap on the main support is close to the edge so be especially careful when drilling.||Larger holes on the ends are pivot point and smaller holes in the middle is where pushrod attaches.|
|Make another bend a short distance from the previous bend in the opposite direction.||
This is what the pushrod should look like, two will be needed. I was going to use music wire which is stiffer but it is also harder to bend.
|Mounting the actuator to lift the arm. I find it easier to test the fit of all pieces before gluing the wood wedge.||
Actuator to lift the boom is securely strapped at the correct angle. I should have mounted this slightly higher.
|To position the two craft sticks that will be part of
arm bearing make sure that the arm will come down to where the actuator is almost pushed in.
|Also make sure the arm can swing upwards without the binding at the hinge location.|
|Syringe actuator in extended position should lift arm above horizontal position.|
|Note washer on the bolt at the pivot point should help the wood parts move easier. Do not tighten the head of the bolt down too tight, the parts must be free to move easily.||
|Bend the wire 90 degrees downward into the plastic tubes.||
Carefully bend the wire back so the pushrods do not
fall out. I was going to use music wire which would
have been stiffer but the paper clip material is much easier to bend.
|Either 3/16″ OD plastic or aluminum tubes can
fit over the end of syringe to make a tight
connection with clear tubing if using 3/16″ ID tubing.
|With the tubes on the end of the syringes the
clear tubing fits tight.
|Attach one end of the other piece of tubing to the lower syringe.||Attach the larger 12 cc syringes to the opposite ends of the plastic tubing.|
Filling the Cylinders
Part of the key to success with this project is getting as many of the air bubbles out of the lines as possible. In automobile brake lines this is known as “bleeding the brakes”. I am not sure I have the best procedure for this
but I will give some suggestions.
|Now using large wood screw countersunk to hold arm to base.||College for Kids class built 12 of this project.|
|One addition that could be added is a way
to limit the upward travel as there is not
enough support for the plunger when it
pushes out to the extreme causing
arm to bind at the very top.
|Syringe Hydraulic Arm was a Big Hit at my Booth
for STEM Day at MN State Fair
Note: some of the hydraulic kits are on sale right now.
I have been working on building a simulator to demonstrate Pascal’s Principle of fluids using syringes and plastic tubing.
“Pascal’s Principle states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container.”
What exactly does this mean in practice? For the simulator I used a large syringe that has a piston cross section diameter of 34 mm and small syringe with cross section diameter of 13 mm. Like other mechanical systems there is a mechanical advantage where distance moved and force tradeoff. When the smaller piston is pushed with a force, that force is distributed equally across the larger piston cross section causing a greater net force. For the fluid to be spread across the larger cross section more fluid volume must be moved from the smaller cylinder.
For my first experiment I worked from the other direction and pushed the large cylinder a short distance of 8 mm which extended the small cylinder a much longer distance of around 60 mm until it could not move any farther. I calculated this also which was off the first time but repeated trial proved that calculated and observed were very close.
For calculations we need the formula for the area of a circle :
Area of Circle = π x radius²
Large Piston cross section area = 3.14 x (34/2)² = 907 sq mm
Small Piston cross section area = 3.14 x (13/2)² = 133 sq mm
Moving the large piston 8 mm will displace amount fluid = cross section x length of movement
Fluid Displaced = 907 sq mm x 8 mm = 7256 cu mm
The movement of the small cylinder should be the fluid displaced / cross section area of small cylinder.
7256 / 133 = 54.6 mm movement of small cylinder
Actual movement was recorded at 60 mm or 6 centimeters. My calculations included some rounding errors and measurement of piston might not have been accurate.
I have not checked the amount of force generated but did check the amount required just to move the opposite cylinder. Moving the small cylinder with the large cylinder took a large amount of force, 1250 grams or around 12 newtons. This is like pushing down on the short end of a lever. Pushing the small cylinder took very little force.
Air Powered Model Car
I built the OWIKit Air Racer kit which uses compressed air to power the car much like how a steam engine functions. It is a rather difficult kit to build with so many pieces and the tiny O-rings. Blog article on building OWIKit Air Powered Racer.