Racing Spider

Flexapod (Servo-less Octapod)

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A playfully terrifying mechanical spider with a unique drive system

I built this for the challenge, I was inspired to improve upon the ideas that (former Mythbuster) Jamie Hyneman shared in his project videos from 2015. 

The key my version of his creepy crawly is what I'm calling a Flexapod mechanism. An Arrangement of cams, shafts and bearings that enables super radpid movement and adaptability over rough ground. Also it is quite capable of making people's skin crawl and squirm.

It uses 3D printing and off-the-shelf  RC parts: battery, bearings, motors, controllers, screws, bolts aswell as a few custom bits. All of which I will explain as I endeavour to share this project for those who want to build one of their own.

So if you keen to build it, let me know and I will help you where I can.


All the 3D printing STL's

x-zip-compressed - 4.54 MB - 02/13/2020 at 13:34


  • Assembly graphics

    Russell Munro6 days ago 0 comments

    These are graphics of the machines assembly and operation. 

    Exploded view of the tray and left hand side. The right hand side is a mirror copy. Not show in drive belt between motor pulley and inner camshaft pulley. 

    Exploded View of the "hip" sub-assembly. 8 of these are assembled first, 4 left orientation 4 right. 

    The cams working together to create a walking gait. Notice how the main cam (show here as see through) rotates on the same axis that the leg pivots up and down on. This is the key to the independant suspension of the legs.

  • BOM and STLs

    Russell Munro02/13/2020 at 13:33 0 comments

    Let's start with the bill of materials and STLs. The instructions are coming in a series of posts in the near future. 
    Link to the BOM. Most of the parts are off the shelf or 3D print. 2 of the parts (x2) are custom made, the camshafts, I will explain these in a future instruction post. 
    Link to STL zip. The STL parts where designed to print on my Lulzbot Mini 6" with 0.5mm nozzle. Your results may vary so I recommend you print one of each part before printing all the parts, just in case you need to make some printing adjustments.  
    Print ‘Cam Lift’ and ‘Cam Main’ with strong or stiff material like nylon or PLA. All the other parts use I used ABS. Use whatever material you like but the Cams need to be a strong material because the bearing impart a lot of cutting stress. 
    ‘Gears’ and the ‘60 tooth pulley’ may need a 0.5mm print nozzle. This is because of the detail required in the teeth. I've never tried so print them on a nozzle bigger than 0.5mm. If you try a bigger nozzle please let me know how it turns out. 
    Don't print all the Tray files, choose the '12 inch printer' file if you have that size print bed. Used the other 3 files if you have smaller print bed. 
    Print all the parts in the XYZ orientation that they come in. This is to maximise component strength. Also, some parts will require support material.  
    Except for ‘60 tooth pulley’, print all the parts with maximum fill. Be careful that sometimes 100% fill can bulge a part. So, you might be better off with 90-95% fill. ‘60 tooth’ can happily live with 10% fill. 
    If you find any mistakes please let me know. Thanks for following. 

View all 2 project logs

  • 1
    Tray and mounts

    Parts to Print
    1x Tray-full.stl  (or Tray-back, front and joint for 6" print bed)
    6x Bearing-rib.stl
    4x spring-mount.stl
    1x Speed-controller-mount.stl
    1x Mount-mount.stl

    6x 10mm screw
    10x 10mm counter-sunk screws (+4 for 3 part tray)
    18x 3mm nyloc hex nuts

    A) If you had to print the three piece tray joint them together now with 4 counter sunk screws. When assembled the whole tray should sit level on a flat surface. If it arching up you may need to clean up the underside of tray-join.stl to help it sit better with the front and back pieces. 80 grit Sand paper on sanding block should help.

    B) Push 18x nuts into the resecess underneath the 6 Bearing-rib prints. You may need to use a solding iron to heat the nut, melt the surounding plastic and set it in fully. If you do, make sure to temporarily screw in a m3 bolt to keep the nut thread aligned with the bolt hole.

    C) fit spring mounts with 2x counter sink 10mm screws from underneath the tray
    D) fit motor mount with 2x counter sink underneath the tray. Make sure flat is facing away from the tray centre
    E) glue ESC mount in place

  • 2
    Knee joint

    coming soon

View all instructions

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Russell Munro wrote 5 days ago point

Thanks Dejan! 

  Are you sure? yes | no

Dejan Ristic wrote 5 days ago point

VERY cool. As an extra bonus it has that uncanny valley creepyness of the Boston Dynamics robots. Will follow this project for sure.

  Are you sure? yes | no

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