Make a simple double acting hydraulic cylinder out of syringe and other parts for your children toy projects.
Make suggestion because this can be for sure upgraded so any ideas are welcome.
Step 1: What You Will Need Parts and Tools
Please use appropriate PPE (Personal protective equipment) when working.
Screwdriver with the radius about 4-5mm and no markings like Cr vanadium.
A syringe (3x) nipro 3ml or similar. At least 3 but may be many more if you are not handy.
A type of cheap lighter
A good one lighter for heating plastic parts
Sort of dremel type tool with drills and similar various pieces
Water hose connectors 4mm type ''T''
Step 2: Start
Start by measuring a required length for a cylinder and other parts so it can feet your project. This means syringes and screwdriver.
After measure cut the side (oposite of the place where needle goes) of the first syringe to desired length.
Cut part where goes needle from second syringe. You will need this for hose connector.
Step 3: Preparation for Friction Welding
Heat with lighter a part (were needle goes) you previously cut so it is soft and mould it to a cone sort of shape. It does not need to be very accurate.
What is important is that the hollow part needs to be filled in (to disappear).
Then use a stone (pink one on the pictures) to give it a more cone like shape. One more important step. Do not make to sharp angel on the cone.
Drill the syringe, where you wont a hose connector to be, just a little bit so it is more like a guide for cone part you made.
Step 4: Friction Welding
Like in picture attache cone part to dremel and press on the guide in the syringe.
Important step - Do not make strong pressure or to light (about 0,5 kg).
Then turn on dremel and when you fill its melting plastic turn off quickly dremel while still applying pressure.
If angle of the cone is too sharp it will cut through and you failed.
If angle of the cone is too blunt you cant guided it and you will failed.
It is more trial and error. You will maybe need many syringes before you get it right or you are very good with tools and lucky.
If you make it its bond is very very strong no glue can mach it (and this type of plastic is very hard for gluing and your doing hydraulics!)
After that drill through a hole so fluid can pass.
Step 5: Cheap Lighter
Why cheap lighter?
Only the cheapest lighters has the required parts!
This can be dangerous! Disassemble the lighter. You need to use empty lighter (double check). Use PPE for eyes.
You scavenge a O ring and two parts (white and red look pictures) that can be screwed together through plunger rubber.
Red part (look picture) requires a little dremel treatment and it's not easy to pull out. You will need to carefully cut plastic around it. It is important that the side that fits on rubber has fine surface.
The white part (look picture) needs to be widened so shaft (from screwdriver) can pass nice (not too loosely). Use dremel.
Step 6: Small Parts and Bits
From third syringe use part where needle goes. Cut it away from syringe just like first one. Use lighter, dremel or combination to put it on shaft. Be careful or it will be to loose or wont fit, so make a slow progression.
After that use lighter and heat it so plastic softens up and shape it so it resembles the original part (dimension and shape vise) where plunger goes. You will put a plunger rubber on this part after you put it on shaft.
Cut the plunger of the second or third syringe with scissors. Cut outer part (that doesnt have hole) but do it from the inner circle going toward outer edge and watch out so you don't damage outer edge. It should snug feet the white part from lighter.
On first syringe shorten the part where needle goes and widen it so a ''T''connector for hose can fit. Again snug fit, slow progression is key to success. This can be reinforced with glue gun or super glue etc.
The ''T'' connector is on one part closed so hose can go on the other. But this is not that important as you can use two hoses!
Step 7: Putting It All Together
Follow pictures it is the easiest way of doing it.
Screw together the white and red part, with plunger rubber in the middle. Do not tighten it up yet.
When inserting plunger part with red and white part in cylinder make sure it is dry as well as cylinder. If two part are dry it will hold the pressure fine because after insertion as you tighten it up the rubber part will expand and push on to the wall of cylinder with good enough force. If wet it will be slippery and get out of cylinder when fully loaded.
Screw it slowly and frequintle test it for leakages, so you don't over tighten it or have leakage. If you fill that O ring is moving while you move schaft than you need to tighten it up a little. So check for vacuum and pressure test. With this set up it can easily hold up to 1.5 bar which is around 1.5 kg so its good force.
For the excavator on the picture I used a type of peristaltic pump (3 of them one for every cylinder) from toy bubble gun. The pump need a little adjustment and modifications but is very good choice for hydraulic toy project for your children.