Super Simple Hydraulics Using Syringes

Simple hydraulics using syringes

When making a toy excavator arm, or any robotic arm, the typical approach is to put motors at the joints, or if there isn’t room, to put the motors somewhere else and transfer the force using fishing line and pulleys. [Navin Khambhala] chose instead to do it more like the real excavators, with hydraulics using syringes. And we have to admit, the result it pretty elegant in its simplicity.

The syringes do the job of single-acting hydraulic actuators, one at the motor and the other where the force is needed. In between them, what appears to be clear vinyl tubes carry the fluid between syringes. 12 volt DC motors with bolts on them move nuts attached to the syringe pistons to push and pull the pistons. It is so simple that no further explanation is needed, though like most apparently simple things, we’re sure a lot of effort went into making it that way. The video below shows the finished product, as well as walks through the making of it.

And as for other methods of transferring force, for the ‘fishing line’ one, see or own [Joshua Vasquez]’s detailed articles on making working tentacles. For putting the motors at the joints the Pixar style lamp is always a fun one.

34 thoughts on “Super Simple Hydraulics Using Syringes

  1. This Videos Is awesome. Now if I can apply the scientific method to it this would make a perfect science fair project for my kids explaining hydraulics that would surely win.

  2. I love it! This just proves that you do not need high end equipment or expensive parts to make something really nice.
    A project well done.

    PS: syringes and a cheap gearpump pumping mineral oil (instead of water) can do wonders and really demonstrates the wonder of hydraulics. When the inlet of the pump is connected to a syringe (reservoir) of the same size, the pump could never transfer too much oil and therefore prevents the syringe at the receiving end from popping. When the syringe close to the pump is directly connected to a slide potentiometer it can even be made to act like a servo. But that would all make the project much more complicated, though much more suited for automation (computer control). Ahhh… these are the projects.
    I mention this because I did some experiments with capacitive sensing, to replace the potentiometer by to simple strips of coppertape on the outside of the reservoir syringe, though to get enough sensitivity oil is not very usefull as a dielectric and water is to be preferred. However water is too thin and “leaks” through the gears of the pump, so large forces are difficult to maintain without the motor slowly pumping to compensate for the leakage (to maintain position). After seeing this video, this old abandoned project is remembered again and should perhaps be revived soon.

    1. I was trying to make capacitive sensing with 3d-printed linear actuators, but it seems capacitance would be too low to properly measure position, someone touching actuator would have too much influence on it. Maybe a strip of “conductive” filament and wiper would be better? Those have pretty high resistivity (more like “resistor” filament than “conductive” filament) so would not use too much power.

      1. What if you sent a low frequency radio wave into a conductive fluid and measured the signal strength after a software bandpass filter? You could measure with and without the signal in the fluid to remove any external noise.

    2. I also thought of a gear pump – like the one I use in a water sprayer which is nice on festivals when the sun blazes down. That was less than 4€ and makes several bar of pressure. But then of course you could have a central pump and control valves to make it closer to the real thing. But in a model I would stay with water anyway. It makes much less of a mess and I don’t know if the cheap pump is resistant to oil. Using valves also solves the problem of backwards leakage through the pump – at least a check valve could be used.

  3. My daughter has a Tinkercrate where the main project is to build a arm/claw using syringes. She liked that a lot. We took it to a hackerspace located downtown and put it together there. When she was done she went outside and was showing it off to anyone who walked by on the sidewalk. I think she was 4 or 5 at the time, it was a while ago. She was giving them lessons in hydraulics!

    The tinkercrate used cardboard pieces with round prong fasteners for the joints. The cardboard eventually gets droopy. I meant to cut her a bunch of new pieces out of acrylic on a laser cutter but never got around to it.

  4. Holy crap that was awesome. I’m amazed at his thought process and simplicity in design. Little things like the JB Weld (?) around the ends to hold the nuts – so simple yet so awesome! Very nicely done!

  5. Cool project! I’ll add it to the list… *sigh*
    Technically, it’s only hydraulic when it’s pushing out. It’s pneumatic when it’s drawing back in (the atmosphere being the source of both air and pressure). It wouldn’t be too hard to upgrade to a double-acting system, though.

      1. I would think so too, but…
        I tried similar project. And no matter what I did, in pulling configuration those syringes always sucked air inside and therefore promptly failed. I tried four different syringes, i tried boiled water, i tried oil, i tried featherlight loads. Syringes barely moved themselves, not much else. Left me quite unsatisfied.

        It’s a small wonder for me to see such a nice working example.

        If somebody has insight why I failed and [Navin Khambhala] so elegantly succeeded..

        1. The syringes are single acting cylinders/pistons in that case. So you need an external return force, like a spring or the weight of the machinery lifted. A hydraulic cylinder is never “sucked back”. Of course this is a little difficult in a model. But installing springs is possible.

  6. I think it would be great to also give some credit to this poor Afghan refugee boy which is living in a remote village in Iran. Without having access to internet or other information and yet he accomplished this masterpiece !
    Video upload date is December 28th 2014 but it looks like it has been taken much before that.
    In the video someone just found him playing with his toy and asks him how it works and he explains.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.