Craig Fox

The 3D printed section which holds the dyno generator needed a bit of re-design, so that's changed shape slightly and now includes a lid to hold the dyno in better. This now securely holds the generator in place whilst the lead turns it to generate power.

I've assembled all the parts together, which meant I could get my trusty assistant involved for some testing; Reuben the Labrador! He helped me do several tests of pulling the lead out to generate power. As Reuben pulls the lead out it rotates the generator in the lead, providing power to the USB port. A little red LED also lights up so you can see when Leashy McLeashy is working. A normal phone charging cable can then be used to connect the USB port on the generator to your phone, giving you some extra phone charge when out on a walk.

The proof of concept is coming together in this prototype. I've 3D printed a housing for the dyno generator. This holds the generator in place on the retractable dog lead meaning that it can be rotated as the dog lead extracts and retracts without falling out.

The 3D printed part was made using a process called FDM (fused deposition modelling). The FDM 3D printing machine melts plastic and extrudes out into tiny lines. These lines are gradually layered up to make the finished part. This is such a useful manufacturing method as it's quite quick and can make almost any part that it's possible to model in the digital world! For this project that's a great thing, as I was able to measure the generator and dog lead, then design a housing that fits perfectly around both parts. I wouldn't have been able to go online and find a housing that would be suitable for this job otherwise.

My next job is to tidy up the assembly of all the parts, then I'll hopefully be able to share some successful testing in my next blog post.

It was great to have the kick off call with Lilli and hear her explain more about her idea of a dog lead which could charge your phone whilst you're out on a walk. I know from my own dog that there is a lot of energy available from them running about so being able to capture some of that  to charge my phone would be great!

I have taken Lilli's idea and plan to develop it on a retractable dog lead. The easiest way to turn motion into power is by rotating a generator. Rotating movement in = power out.  A retractable dog lead already does the step of turning linear motion (your dog running backwards and forwards) into rotational motion (the coil inside the handle which turns to retract or extract the lead). I then just need to connect that rotational motion to a generator.

For the proof of concept, I plan to use a small hand-cranked dyno. This is a product already available where you turn a handle to give power to a USB port; perfect for plugging your phone into!

For the initial stage of the prototype I have started joining this hand-cranked generator to the rotating coil inside the retractable dog lead. This has involved some cutting open of the dog lead housing to make space for the generator, and some remoulding of the generator handle to get it to fit snugly into the grooves on the dog lead coil. The generator handle is made from a thermoplastic, so I was able to heat it up to make it soft enough to be reshaped to fit into the dog lead coil.

At this stage the prototype looks quite rough and ready! This is because I'm purely looking to test whether my ideas on how to make Lilli's Leashy McLeasy 2000 functional, actually work. Once I've proven that the general design concept is functional, then I can refine the design to  make it look nice as well.

My next steps are to design and 3D print a frame which will connect the rest of the generator securely to the dog lead housing. Watch this space!