Aug 14, 2015 | By Simon

When it comes to learning about basic engineering principles and simple machines, some of the best tools for learning can be as simple as basic toys.  Thanks to 3D printing and the ease of sourcing mechanical parts for cheap, many of these can even be made by hand, too.  

Among others, the PulleyBot from Instructables user ‘printeraction’ is among one of the better ones that we’ve seen and can even be modified with a number of different parts.  The simple, single actuator 3D printed toy features a transmission and is made up entirely of pulley systems.

Similar to bicycle chains, a pulley system involves a belt that is attached to a mechanical transmission.  The belt is looped around a set (or sets) of pulleys - which are usually simple wheels with grooves or teeth in them for the belt to catch on - and as a pulley rotates about an axis, it drives the belt via friction between the belt's surface and the groove of the pulley.  In turn, this drives the other pulleys linked to the same belt and provides motion and power.   

In the case of a bicycle, the power is provided by the riders legs connected to the pedals - however in more complicated pulley machine scenarios, the power is driven by an engine or other automated source of power.  For the PulleyBot, ‘printeraction’ has reduced this transmission to a simple system using easy-to-find parts.    

To create the PulleyBot, ‘printeraction’ has supplied all of the necessary STL files for 3D printing your own parts - which should be done immediately after sourcing the non-printed components.  To make sourcing the components - which include a Pololu Micro Metal Gearmotor 1000:1 and a 3 AAA Enclosed Battery Pack with on/off switch to both power and drive the system - easier, ‘printeraction’ has conveniently linked all of the parts he used to where they can be purchased online.     

While any 3D printer will do, ‘printeraction’ printed his parts on a MakerBot Replicator 2 with standard resolution.  Since he designed all of the parts to be printed without the need for support material and in one single job (on the MakerBot Replicator 2), the printing process took a total of 5 hours and 45 minutes.

Additionally, each of the 13 total 3D printed parts - including the pulleys - have been optimized to better serve their function in the final assembly.    

“I designed the 3D printed pulleys to have a tight fit around the shaft and the frame to have a loose fit,” he explains.

“The tolerances on the MakerBot I used may be different than the printer you used, so the fit may not be exactly the same. Try sliding your parts onto the D-shaft and see if they fit well. You may need to use a file to widen the axle holes if the fit is too tight, or you may want to reprint some of the parts and scale them up or down by a small amount.”

Once the 3D printed parts have been created, cleaned and organized, all that’s needed is to assemble the final parts into the chassis body.  Since the non-printed components were designed to fit neatly within the 3D printed designs, this process has already been tested by ‘printeraction’ and is just a matter of putting the parts together.  

Once the final assembly has been snapped shut and the pulleys and driving belt have been secured, the PulleyBot is ready to be used!  Of course, since the design of the PulleyBot is focused on being customizable, this standard bot design is only the beginning of what’s possible with the various pieces.  

“There are lots of fun ways to make pulley-driven bots, and they can have any range of complexity,” says ‘printeraction’.  

“Make your own PulleyBot using some of the tools and ideas I've provided. If you want to learn more about other pulley and cable mechanisms, check out this Instructable on pulley mechanisms. Have fun!”

Although he mentions that there are “definitely a couple ways I could have improved this design” including the decision to use bearings on the rods and more pulley systems, we’re quite impressed with the final result as-is.  For users looking for a more challenging build, they can always continue printing more of the components to build out a more complicated pulley-driven machine.  



Posted in 3D Printing Applications



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