Picture of Hydraulic JudoBots

Two robots face off and try to throw each other off of a table! It'll make more sense after you watch the video...

More footage from actual student-built JudoBots:

I call them JudoBots because of the way they seem to throw and grapple with each other during combat.

Although designed for children in grades 4-6, I think just about anyone can have fun with this. Even parents can't resist trying it out!

The bots are assembled from four components built separate from one another: the base, the stand, the arm, and the hydraulic system. The hydraulic system uses plastic syringes as pistons and water as the hydraulic fluid.
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Step 1: Materials, tools, and design criteria

Picture of Materials, tools, and design criteria

JudoBot Criteria

  1. The base of each JudoBot must fit within a 10-inch square. This is to prevent students from building sprawling robots that cannot be flipped.
  2. Material limitation: craft sticks (50), craft cubes (10), cubes with holes (10), syringes (4), adhesive bumpers (10), decorative woodcraft/extra woodcraft (5), everything else within reason.

Material limitations are in place to promote resourcefulness and to reduce cost. Also, clever students can no longer pile hundreds of sticks onto their bot in order to make it too heavy to move.

You may choose to use other materials. This is what I use because I need to streamline my materials to fit with the other projects in my program, as well as keep the cost per project low.

Step 2: The Base

Picture of The Base

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Step 3: The Stand

Picture of The Stand

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Step 4: The Arm and the Wedge

Picture of The Arm and the Wedge
sbend copy.jpg

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Step 5: Assembling the pieces

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KarenT35 months ago

awesome project we have to battle soon :)

luzm made it!5 months ago Thank you so much. I had a lot of fun doing this

WYE_Lance (author)  luzm5 months ago
Very cool! Thanks for sharing your awesome design and for including a video!
chuangt2u1 year ago
Very cool.
Had to make some...

Will video the battle ... "There can be only one".

Thanks for the ideas.


goyo811 year ago
Fantastic project! My students built these in my physical science class and it was their favorite!
yo you know the whole pressure thing yay that is what works the thing what ever it is you know wat evs
Judobot Tournament! cant wait fir the thrill of the amazing tounament
what types of judobots can be made? like creative ones?
Idea: create a team event after the battles......a pass the parcel sort of thing.....vid the results. For a team vid
krouterer2 years ago
This is a awesome machine !
I build mine this afternoon in 45 minutes, and it works great. I showed my students (5/6 class) your video this morning and they where fascinated. This will be our next Project to do. I can't wait to see what the kids will construct!
Thanks for this good idea!
WYE_Lance (author)  krouterer2 years ago
Very cool - let me know how it turns out, and maybe post some photos
chriscook82 years ago
Hey thanks for the awesome project, we just used it for our kids program at our hackerspace. We had about 25 kids building them and it turned out fantastic!
WYE_Lance (author)  chriscook82 years ago
Wow, that's great! Thanks for sharing that with me :)))
Bindi 30002 years ago
and it is awsome
micraman2 years ago
Hi there! I just wanted to say thanks for the wonderful idea! I adapted the syringe concept and made a catapult which won first prize! Thanks!
WYE_Lance (author)  micraman2 years ago
Wow, that's awesome! What contest did you win first prize in?
Well it wasn't really a contest we were supposed to build a mechanical toy in Physics.
anibioman3 years ago
these are really really cool i made something similar in technology class but we made claws and used them to pick up ping pong balls in this little game of who can pick up 5 balls faster.
carladee3 years ago
Great project! I recently used this in my high school physics class. The students really enjoyed it. A couple of groups added a third syringe to make the arm lengthen. I even had one student make his robot walk.
WYE_Lance (author)  carladee3 years ago
Amazing! Thanks for sharing that with me. Do you have any photos or video of your student's designs?
Very very cool. It's genius to use syringes as both the cylinders and pump. Simple and functional. Reminds me of building backhoes and dozers with my pneumatic Lego cylinders. If I don't place in the Play contest I hope you're the one that beats me.
WYE_Lance (author)  NightHawkInLight3 years ago
Thanks, but I got the syringe idea from hydraulic robot arms that I found on Youtube and this site.
This is so cool and a great fun way to teach kids so much. I am highly impressed.
iPD3 years ago
Wonderful! :-)
jetringer513 years ago
Just built my first one and it's pretty cool. My students are getting excited to try them out.
WYE_Lance (author)  jetringer513 years ago
That is awesome!! I'd be thrilled if you could post some photos or video of the project in action.

I am planning an update for this project, but I'd like you to here it first:

Use masking tape to secure the piston that actuates the pivot, not cable ties. Students requesting for help tends to bottleneck at this step, so using tape is much easier to attach and readjust (and it's just as effective).

I just finished conducting this project with about 30 4th-5th grade students. Take your time with each step, especially the testing/redesigning phase. Many robots perform less than impressively at first and require some additions and adjustments. Be sure to bring unassembled components for the students to refer to. Have fun!
gmtanner3 years ago
Great Idea!!!

How long does the typical build take?
WYE_Lance (author)  gmtanner3 years ago
Each one takes about 1.5 hours from start to finish
A fantastic way to cover the curriculum, involve the students in "doing" and also allow them to have a lot of fun. They soon learn if their design is viable. Proof of concept is the competition. It either wins or loses. Some real- world learning! Wish I'd thought of it!
stumitch3 years ago
VERY well done! my students all want to build it!
ZeroSight3 years ago
this has earned you a subscriber. the idea of challenging young kids to think an build is also great.
macrumpton3 years ago
Very cool. It would be interesting to create a computer interface for these. Maybe a 2 motor setup where one motor selects which plunger to operate and the other actuates the chosen plunger.

PS I thought Sumo was the sport where the winner gets his opponent to step outside of the ring. Is Judo like that too?
WYE_Lance (author)  macrumpton3 years ago
Yes, it is more like sumo in some ways, but sumobots are already established as small bots with wheels that try to push each other out of a ring, like this:
fozzy133 years ago
This is really cool! Being a judo player, the title of this instantly interested me. I've seen similar things on Youtube before, good job.
Aron3133 years ago
That would be awesome to play!!!!!!
Kiteman3 years ago
Gosh, that's brilliant!