PIRANTULA - A powerful hexapod / spider

Note: I now believe that this robot might have a fatal flaw in the leg lengths being too long. Taking into consideration the torque generated by such long limbs, it becomes very difficult for this design to raise itself. However, I'm leaving it up in case somebody has better ideas such as mounting springs/elastics to take some of the strain and balance out some of the weight. Without such an improvement however, you are likely, like I have, to burn out a number of these rather expensive servos, so I would advise to consider selecting another design for now. I really do hope I can fix this at some point. Good luck my robo-building buddies!

WARNING: THIS ROBOT COULD EASILY CAUSE HARM TO YOURSELF OR OTHERS!

Disclaimer: Only commence making this robot and subsequently use it if you are fully aware of the dangers involved. I bear no responsibility for any harm or damage caused by making or using this robot. This robot is dangerous. Do not proceed to make it unless you fully undertand the danger and are of sufficient skill to avoid harm to yourself or others.

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It's like a tarantula... but only 6 legs so not a tarantual... it'sPIRANTULA!!

Design intent: Must be badass!

After being frustrated by lightweight robots, my aim was to design a robot with plenty of potential for expansion. To do this, I figured I need powerful servos and power supply.

This robot should be able to carry plenty. It's not the cheapest due to the powerful servos used.

Please take very good care of your fingers. The servos used here could easily snip off your finger. Also beware that it can pack quite a punch if you're in its way (it's drawn my blood already in one accidental "punch"). To keep it as safe as possible to myself, I've added a relay to cut off the servo power remotely via the Pi. Also beware that these power packs can pump out a lot of juice if shorted, which can burn you. I'd recommend removing any metal jewellery whilst building the circuits.

Designed entirely in FreeCAD, I can post up the source files if anybody is interested (typing this+BOM has taken forever!).

Also, as I post this, I've only just finished hooking it up and making it stand... so it's early days yet! Apologies for such crudeness in the design :). I work full time, so only have a few hours a week to improve / update the design... but fully intend to keep doing so :).

Future thoughts?

• Upgrading to include ROS (currently using my very amateur Python code).
• Single power supply (instead of separate source for Pi).
• Adding a detachable module on top for extra Pi4 power, using supply from main unit.
• Research into SLAM with pi camera and possibly LiDAR.

Bill of Materials:

• 18x Servos - Hiwonder LD-220MG Link
• 1x Pi Zero W - Link
• 2x Servo Bonnets - Adafruit 16ch PWM bonnet for Pi Link
• 4x Header pack (right angled) Link
• 4x header pack (straight) Link
• 1x 40-pin Extended header Link
• 1x 40 pin Female header Link
• 1x extra header pins - for hooking Pi pins onto topmost Servo hat Link
• 1x 40A 18650 Battery pack Link
• 1x 40A 18650 Battery pack with BMS Link
• 1x USB power bank - for powering pi Link
• 2x Voltmeter/Ammeter Link
• ~4 5-wire connectors Link
• 1x 30A relay Link
• 6x M6 25mm - for attaching legs to body Link
• 18x M6 40mm - for attaching servo brackets to leg pieces Link
• ~50 M3 12mm hex bolts - for screwing case lid down Link
• 12x M3 16mm bolts for screwing case sides together Link
• 12 m3 nuts
• 24 M6 nuts
• Lots of M6 washers - to give the legs a chance not to snap off, by easing the strain around the M6 bolts.
• 1x Fuse Holder - In case of things going bad! Link
• 2x 20A step down modules Link
• various brass standoffs Link
• Tons of cable ties Link
• Various 30A power connectors - Link

Print Settings

Printer Brand:

Creality

Printer:

Ender 3

Resolution:

0.2mm

Infill:

20

Filament: Tinmorry PLA

Black

Notes:

I used Cura's Tree supports. Without the tree supports, I think it might be difficult to get out the support from the limbs.

I print the limbs vertically, so one side should be clean down the bolt hole. The base bolt hole will need some work to prise out the supports.

Be sure to clean out the bolt holes on the limbs well, so the bolts can get in and engage with a nut and washer.

Print limbs with a skirt.

If you can print in flexible material, then do the toe in that. There is also a shock absorber for placing between the body and legs if able to print in flexible.

Category: Robotics