Hey everyone!

It's been a while since I posted a build of my own, and what better way to ease myself back into the game than by replicating one of my favourite gadgets from the series? I stumbled across my original Chronodyne Generator whilst sorting through some of my Doctor Who props and given that this was one of my earliest attempts at prop building, there was a lot of room for improvement.

The plan here is to create an accurate model that can be 3D printed and 'unfolded' to be built using Pepakura (a method which involves turning a 3D model into a series of 2D nets which can be printed out and assembled by hand.) I began by modelling the generator's main body using the basic measurements given on the prop's concept art - 50mm diameter, 25mm tall - and extrapolating everything else using screenshots from The Caretaker.


Thank you to both Dino and davidnagel in the http://tardisbuilders.com/index.php?topic=6352 reference topic for their help with dissecting this prop and posting hi-res images from the episode. The next step is to model the 3 arms/legs.

It's good to be back!
-- 14th

One thing I noticed when looking back over the reference material for this prop is that the generator's "legs" are all a different shape to one another! With this in mind, I began by modelling just one of the legs before duplicating it and modifying the shape to match each of the 3 variants that I could make out on the original prop (as seen below):



There are just a few minor adjustments to make - including cut-outs for the LEDs - before I can begin optimising the model for 3D printing and assembling using Pepakura.

Thanks for looking.

Two updates in one day, how exciting!

As promised, I began optimising my model to make it more "3D printer friendly". First of all I separated the main body of the generator into 3 sections and made the insides hollow (including a 12mm hole in the bottom for a magnet to be glued into place for attaching the prop to metal surfaces just like in the show!) The reason for splitting it into 3 parts is that I like to make my models as easy to print as possible - even if it sometimes means that there are more parts to assemble afterwards. As it stands, the generator's main body can be printed without any supports, reducing the amount of time required post-printing to clean up the inside of the model.


Following this, I rounded off the corners of the legs to better match the original prop. This can only be done on the 3D printed version as otherwise, the Pepakura software will attempt to recreate these rounded corners when unfolding the model which will make it almost impossible to assemble whilst simultaneously maintaining one's sanity. I also added a curved recess to the inside of the legs so that they would sit flush against the body of the generator when assembled.


Last but not least for today is a mock-up of how the 3D printed generator will look with green LEDs installed in the centre:


Once I work out how best to print and assemble the legs I can add the slots for the LEDs and begin work on the Pepakura version.

Thanks for looking.

I replaced the bottom of the Chronodyne Generator with a removable base to allow access to the electronics and batteries, before adding three evenly-spaced holes in the outer wall - both to help with aligning the legs and for the wires that will power the LED in each leg.



Finally for today, I added holes to each of the legs for the LEDs to shine through, followed by a thin 'tunnel' leading back to where the legs join the rest of the generator for the wiring. I'm hoping that, with the tunnels being so small, this won't affect how easy the model is to print (but without a 3D printer of my own to do a test print, I can't be 100% certain that there are no flaws in the model.)



With the 3D printer-friendly model now complete, I can now move onto the Pepakura version!
Thanks for looking.

Optimising the model for Pepakura was much easier than optimising it for 3D printing! I didn't have to worry about overhangs, print supports or making the insides hollow to accommodate electronics. In fact, all I had to do was separate the legs from the main body, separate each of the "chunks" from the rest of the leg (for ease of assembly) and add slots for the LEDs to shine through.

Thanks to TinkerCAD (the 3D modelling software I use) having issues with exporting files without corrupting them, I had to clean up the model in Google SketchUp before it could be properly unfolded for Pepakura. On top is original, broken file, and below that is the repaired file. As far as I could tell, the random lines on the legs were a result of TinkerCAD corrupting the 3D model and these confused Pepakura Designer when I tried to unfold it the first time, splitting each leg into a separate piece every time it encountered a line, and for some reason wouldn't let me re-attach the pieces to form a single net.


(Ignore the generator's main body; I think that those lines were the result of me importing a curved object into SketchUp and for some reason the Pepakura software chose to ignore most of these lines, unlike the lines on the legs. )


File issues finally fixed, I imported the model into Pepakura Desginer to be 'unfolded'. Most of the unfolding process is carried out automatically by the software, but as you can see the computer's unfold would be extremely difficult to assemble unless you had tiny fingers, infinite amounts of patience and ultra-zoom camera lenses for eyes.



And so begins the most time-consuming (but in my opinion, the most fun! ) part of unfolding Pepakura: adjusting the parts to make them easier to build and removing anything that wasn't needed - for example the 0.5mm wide strip that wraps around the top disc; this is totally unnecessary because the card I will be using to assemble the model will give the disc its thickness anyway. To give you an idea of the issues I had to fix, here is a close-up of the top disc, with overlapping parts designed to recreate the depth of the holes in my original model:



Within an hour I was able to simplify the 46 automatically-generated parts into 16 usable templates.


Unfortunately I only have the trial version of Pepakura Designer, which prevents me from saving the unfolded model so that it can be downloaded and used by others. However, I would be more than willing to share the 3D model with anyone who wanted to unfold it for themselves.

Thanks for looking.

-- 14th

EDIT: here is a link to the physical build in paper and cardboard - http://tardisbuilders.com/index.php?topic=9038

Following the discovery of previously unseen details on the original prop (see from this post onwards: http://tardisbuilders.com/index.php?topic=6352.msg113947#msg113947) I decided to update my Chronodyne Generator 3D model. First, I cut 2mm off the bottom of the generator and created the black "tri-lobe" base which slots onto the generator and can easily be removed for adding electronics or changing batteries, etc. After taking this screenshot, I also made each of the legs completely hollow: both to allow easier access for LEDs and wires, and so that the base can be held in place without rotating.