Introduction: Brake Disc Clock


Hello! For this instructable, I’m going to be turning an old and rusty brake disc from the scrap heap into an interior décor desk clock, with the use of power tools, CAD, Generative design and 3D Printing. This project took me around 3 days from start to finish, however hopefully after reading this instructable you should be able to fast-track your project by avoiding the mistakes I made along the way

Why did I choose to do this project?

After helping finishing off a project car, I was left with a pile of parts destined for the scrap yard. However, with the current state quarantine, I missed my opportunity to get rid of this “junk” – fortunately this left me enough time to think of a good project which I could do to help prevent some of it going to the scrap yard.

Besides, as a First Year Engineering Undergraduate with a free summer, I have to use my degree teaching and time somehow!


What you will Need

To complete this project, you will need the following materials and Equipment:

· A used (or new, if you like that new-car smell) brake disc - Any size or shape will do; However, I recommend using a disk will a less protruding hub mount (so the clock as a whole isn’t as thick)

· Access to a 3D Printer with Filament – This will be required to print the base of the clock, as well as the mount for the clock to sit in the brake disc. For my project I used an Anet A8 using around 200 grams of Generic Grey PLA filament

· A Clock Module – For my build, I chose a generic 56mm clock module. I recommend using this format, as the modules are cheap and easy to model

· Bolts (and potentially Nuts) – This will depend entirely on the brake disc you are using. If you choose a disc with threaded holes (such as the one I used) on the hub mounting face, you will be able to bolt the adapter straight onto the disc. However, if not you can use bolts and nuts hold the clock module on with the Wheel lug Holes

· 2mm Rubber material – This will form the feet of the stand

· Paint of your colour – This will be used for finishing the base

· A handheld power sander and power drill (wire brush, rotary sanding and rasp attachments) – These tools are needed to remove and prepare the surface of the brake disc (and bolts if necessary)

· A pressure washer / Hose, Degreaser, Alloy Wheel Protector, sand paper and wire wool – required for thoroughly cleaning and preparing the surface of the disc

You will also need to be able to use a CAD package (In this tutorial I used Fusion 360, as that is what I have been taught with), as well as slicing software (This tutorial uses Cura)

However, I must also recommend that appropriate PPE in the form of Gloves (at least), Eye protection and a Dust Mask be used when making this project, as you will likely be dealing with both fumes and iron oxide dust / particles. A well ventilated work area is also recommended

Step 1: Brake Disc

Once I sourced my brake disc of choice for the clock project, the first step was to remove any surface grime and loose rust with a pressure washer (a hose will work too). I made sure to wash any internal cooling vents thoroughly, as grime and rust tends to accumulate there the most.

After drying the disc out, I began to scrape away the thick outside rim rust with a rough file, however it quickly became apparent that this was a slow and ineffective method of removing the oxide layer. After switching to a rotary sanding attachment for my electric drill, I was able to make quick work of the rust. This attachment was also useful for removing the outside lip on the disk (left behind by the wear from the brake pads).

With the lip removed, I was then able to sand down the flat surfaces with an electric hand-held sanding tool, using low grit sand paper. I made sure to keep regularly lifting and moving the sander, as the rust tended to accumulate and clog the sanding surface (I worked in a circular motion around the disc in the same direction of the wear marks, helping to emphasise the pad contact area). I also power sanded the exterior rim to help shine and remove any residual rust.

Once this was done, I used a wire brush drill attachment to remove the rust on the curved and depressed surfaces which cannot be treated with the sander, such as the hub mount sides and cooling vent ends. While this didn't create a perfectly smooth surface, it removed most of the rust leaving a shiny and textured finish.

The next step was to use a rasp drill bit to remove as much rust as possible from inside the cooling vents. This also didn't leave the surface perfectly shiny, however removed the majority of the large rust spots and made the disc presentable. I repeated this whole process on the reverse side of the disc, followed by going over all surfaces with a finer grit sand paper on the power sander (120 grit worked well at this stage)

The final parts to finish were the threaded holes on the face of the disc which I would be using to mount the clock module. As road grime had accumulated over time clogging the threads and making them unusable, I used a Tap and Die set to clear them out. Further continuing on the theme of refurbish over purchase, I managed to find two very rusty 8mm bolts of the right thread pitch in a toolbox of old collected fasteners, and using the wire brush attachment for the power drill cleaned them up to a usable standard again.

When most of the rust had been removed from the disc, it was time to prepare the disc for treatment and surface protection. I rinsed the disc again to remove any dust particles (You can also use soapy water to help remove residual surface oil or grime), and once it dried used Brake Cleaner to remove any stubborn grime and oil (while my disc felt clean to the touch, a considerable amount of grime came off with the cleaning rags, so I highly recommend this step).

Finally, I applied a few layers of protective alloy coating to the disc to help prevent re-oxidation. This is the point where you get to step back and admire your handiwork!

Step 2: CAD Modelling

With the brake disc now in its final state, it was time to make the CAD models needed to produce the 3D printed parts. As each brake disc will be different, and will have experienced a different amount of wear up until this point, the key measurements need to be taken were the Disc Diameter, Disc mount protrusion, Internal and External hub mount diameter, Hub Bore, as well as any stud holes and distanced from centre. For this final part, I also used the internet to find the “Bolt Pattern” for the alloy wheels of the same car (My donor car was a 2004 Toyota Rav4, which online sources say has a bolt pattern of 5x114.3, or 5 evenly spread bolt holes, with an imaginary circle with a diameter of 114.3mm passing through the centre of each of the bolt holes)

After collecting these measurements with a pair of electronic Callipers or a tape measure (for circumference to calculate disc diameter), I used my chosen CAD package to produce a basic model of the brake disc. If you are not producing any renders, this model doesn’t need to be complicated, and only needs to have the features listed above in the model to be representative enough of the disc. However, I as I wanted to produce renders of my disc, I also modelled the vents, chamfers, fillets, threads and surface finishes. (I find adding surface finishes along the way helps to visualise the final product)

With the Disc CAD’ed up to the desired standard, it was time to model the clock module. Using both callipers and online engineering dimension sheets, I collected all the necessary dimensions to produce an accurate model.

With these two components modelled, it was then time to design the clock module mount. This will depend entirely on the chosen disc, as some wheels (such as mine) will have additional threaded holes on the surface which can be bolted straight into to act as mounting points for the mounting bracket. However, if your disc does not have such threaded holes, I would recommend using a set of nuts and bolts through the lug nut holes to mount the clock bracket to the disc. As most clock modules come with a threaded head, I used this to mount the clock to the mounting bracket, and used the Hub bore to centre the module mount. Again, as I was planning to render the project, I modelled all the fasteners as well, however this is unnecessary for most cases.

The final part to do was to design the desk support bracket for the disc. Keeping my 3D printer build volume and disc dimensions / centre of mass in mind, and that I would be splitting the base in half for manufacture, I made a basic holder and base with rubber feet for the disc, using the Loft tool to produce a nice looking sweeping curve between the two parts. I recommend that you actually leave a hole directly under the disc through to the bottom surface, padded with some 2mm rubber sheet. This will reduce the load on the stand, and will help reduce material usage as the weight of the disc (in my case, over 5 Kg / 11lb) is not being supported entirely by the plastic stand.

At this point, if you are pleased with the result, you can move on immediately to exporting the printable parts as .stl files, ready for slicing. However, I thought this was the perfect opportunity to test my generative design skills, and produce a stand which saves on material, time and looks more interesting than a flush Loft.

Step 3: Generative Design

This will be a short guide to using generative design with Fusion 360 – it is a very powerful tool, using complicated iterative simulations and calculations to gradually remove material from a design in a load-dependant manner, however we will only scratch the surface for this tutorial. I have compiled two animated clips to visualise the generative process of the chosen holder design for you (labelled "Generative - Back" and "Generative - Front"). As design outcomes are generally impractical or impossible to make using "tradition manufacturing" (E.g. 3 Axis Machining), 3D printing is an excellent solution for manufacturing the final stand.

First, I reversed the stand loft (I.e. using the timeline in Fusion 360), and navigated to the generative Design Workspace. I needed to then select the Preserve Geometry (Locations where material will be placed in the final design, such as the base and holder of the stand), the Obstacle Geometry (Locations where material will not be placed, such as all other parts of the design file including the rubber feet, brake disc and clock module), the Structural Constraint (The contact surface which should not move / will resist the load, such as bottom face of the stand base), and the structural load (In this instance the weight and torque force of the brake disc). This final one was tricky to judge (especially as the desk is supporting the brake disc directly). I chose to apply loads of 3.5N tangentially to the vertical mating faces of the disc holder (leaning torque force), and 10N to the horizontal mating faces of the disc holder (weight and downward force), in order to account for an accidental knocks and pushing the clock (twisting and pushing down actions).

With these conditions defined, I selected the material as ABS plastic under the material selector (Unfortunately Fusion 360 does not include PLA in this list, however ABS has similar enough properties to not impact the final design too much for situations such as this). For more complicated projects, you can alter other settings such as safety factor (the scale factor of which a design can withstand a certain load), however for this project these settings do not need to be altered and can be kept at standard.

Finally, I checked the simulation parameters were OK and (recommended if your computer is powerful enough) ran a preview of the Generative Design. As the preview appeared promising, I sent off the study to the cloud to compute the final outcomes. This computation process can take several hours to complete depending on the simulation (which, in my case, it did).

When the results were finished and prepared, I was able to look at all the returned options, and selected the most appropriate design to use based on ease of manufacture, strength and material cost (as outlined on the right of the viewer). The Generative tool will return designs that, while computationally meet the parameters, in reality are not feasible (for one or more of the three reasons listed above), as you can see from some of the results I received. This is why it is important to filter the results individually after they are computed.

At this point, you can complete any final modifications to the final design (e.g. removing unnecessary parts or residual points which do not add to the part) and export out of Fusion 360 the printing designs as .stl files.

Step 4: Standard Render

Being a visual worker, I wanted to create a set of high-quality images and renders in order to get a good idea as to what the final product will look like, and I also wanted to take the opportunity to improve my rendering skills.

First, I assembled all the parts of my design into a single CAD file, and moved to the render work space. The first step to producing a set of high-quality renders was to allocate material surface appearances to all the components. The best way to do this is use the “Allocate Bodies” setting to turn entire components into one solid surface finish (choose the finish which is either the most used by that component, or has the most faces in hard to individually select positions, such as “satin steel” and the brake disc internal fins), then individually allocate the secondary surface finishes.

For most situations, the standard fusion 360 render environment (solid colour) will be more than sufficient, as it will produce renders where the focus will only be on the design (and also reduce processing time, as there is less background to render, which is advantageous to less powerful computers). By adjusting parameters such as camera angle, altering light intensity, light angle, exposure, focal length and material surface finish, I was able to alter the outcome of renders in any way I wanted.

With these settings adjusted, a quick in-canvas render gave me an idea to how a full render will turn out, and if I was satisfied with the results, the next step was to prepare a full render. I recommend for non-professional situations you set render quality and resolution to standard, as this will help reduce the time for rendering and will be more than good enough for most applications.

Rendering is a process of trial and error – If you do not like how the render appears, adjust the parameters slightly and try again until you like the result!

Step 5: Scene Render

Although I was very pleased with the solid colour background renders, I wanted to produce some more complex and professional renders of my design. Whilst the stock environments in Fusion 360 are good, I didn’t feel that they complimented the design well. As a result, I downloaded and used free online High Dynamic Range 360-degree images for the renders (Royalty free from HDRI Haven so I could upload it to instructables – However, credit for the Auto-Shop environment image to Oliksiy Yakovlyev, and the Office Scenery image to Andreas Mischok). There are thousands of scenes such as these online – search “HDRI 360” into a search engine to find them.

Once I had downloaded the chosen image in resolution, and imported the file into fusion using the “attach custom environment” feature under scene settings, I was able to adjust the orientation of my design to get the best view-point. For this part, I was forced to use 4K images, as my computer is not powerful enough to process 16K scenery images, and crashed upon scene selection. However, this was fixed with the use of the Depth of Field setting, which blurred the background of the scenery, removing the pixelation and also helped draw attention to the clock design from the scenery.

To further improve the appeal and depth of these renders, I also chose to include some additional environment elements. It was important that these elements didn’t draw too much attention or take long to model, but helped emphasise the design and aesthetic of the render. For the Auto-shop Scene, I chose to model a work table, two hex bolts, a spanner and a wheel nut, and for the Office Scene I chose to include a computer desk model which I had modelled earlier for a degree computer lab, allocating the appropriate surface finishes and canvas (Fusion 360 Screen) to all the new additional elements.

It is important to remember that in almost all situations (excluding renders with very reflective surfaces) you don’t need to model what a camera can’t see! Save the time or use it to make the on-screen elements more appealing.

Once I was happy with the scene setup, I performed the renders, and also made a short spinning animation of the model (I chose not to include a guide for it in this instructable, as I am not experienced enough to produce particularly appealing animations as of yet, and don't wont to make an even long wall of text!). Following this, I began preparing the models for 3D printing.

Step 6: Slicing and 3D Printing

In order to 3D print any design, you must first “slice” them into layers, using slicing software such as Cura (I opted for this piece of software as it is easy to use and supports a wide range of commercial printers as standard, not just Ultimakers).

To slice the parts to be printed, I opened the exported .stl files, rotated the parts into a good orientation for printing (the least overhanging parts as possible is generally a good option), and adjusted the print settings. For my model, I used a layer height of 0.3mm in order to reduce the print time, and because I would be finishing the stand after with fine grit sandpaper and Paint, so the layer lines would not impact the final product. You can also increase the printing speed to reduce print time, however you must make sure that it’s not too fast so that the printer cannot keep up or causes significant defects from vibration

As I was using generic grey PLA, I opted to use a hotend temperature of 200 degrees and my build plate disabled (I would recommend ~50 Degrees Celsius, however my Anet A8 bed connector melted and burnt on previous print so I opt not to use it, and use glue stick and masking tape for first layer adhesion instead – they don’t call them “fire-starters” for nothing!), however your settings will vary depending on firmament type so check with your manufacturer for the best settings.

With the slicing settings set, I saved the GCode file and transferred it to the 3D Printer for printing! The total printing time was around 18 Hours for all 5 printed parts, using a total of 201 Grams of filament (including supports)

Step 7: Finishing and Assembling the Printed Parts

With the 3d printed parts fresh off the printer, I removed all support and brim material with a pair of short clippers (I used the pair supplied with my 3D Printer), and used fine grit sandpaper to smooth out the outline of the base (a small "elephants foot" was left behind by the printer, which interfered with the mating surface of each side of the base) as well as the layer lines on the surface and top of the print. This is the part of the build where ensuring your 3D printer is properly calibrated will pay off - I needed to do a considerable amount of hand sanding to get a flush fit with the brake disc and ensure the parts were up to scratch.

After cleaning the parts of plastic dust from sanding, I used a two-part epoxy adhesive (Araldite Rapid) to join the two base sections, waiting over and hour for the bond to harden and set. I also applied the adhesive using a nail around the join with the base section of the print to strengthen the print and prevent it detaching from itself.

With the base joined, I again used fine grit sandpaper to remove the excess adhesive, and to clean up the join for painting. after masking taping over the contact surfaces with the brake (to make sure the surface dimensions are not altered), I applied several even coats of spray-on Black Matte Paint (I had originally intended to use a Red Glossy paint as shown by the renders, however I did not have enough to finish the project to a satisfactory standard), letting each layer dry before a further application.

With a satisfactory surface finish and everything else complete, all that was left to do was remove the masking tape and assemble the clock.

Step 8: Reflection

Overall, I have found this experience very rewarding – It has allowed me to practise and improve my practical skills, as well as my CAD Modelling and Rendering, whilst providing me with the satisfaction of saving material, once considered junk, from the scrap heap. I am very pleased with how the clock has turned out, especially considering I accomplished this task over a period of 3 days, and I personally really like the overall aesthetic of the design and parts used.

There have been several different points of improvement which I have learnt and would use should I repeat this design and build again:

· If I were able to choose the Brake Disc (E.g. buying one from a scrap car / disassembly yard), from a range of options, and not just what I had on hand, I would opt for a smaller disc with a less protruding hub mount. Whilst the clock is still desk size, it is large and heavy so a smaller clock would be better. Other factors such as drilled and grooved discs would also provide more pleasing aesthetic aspects to the design (personal taste)

· I would double check that my printer was perfectly calibrated. Whilst it is not the best machine available, a few more minutes of double checking would have saved my much more time down the line of the project

· Go straight to using power tools. I spent a reasonable amount of time trying to manually prepare the brake discs, when I should have used powered tools from the start to save time (and energy!)

· Choose a disc will less rust and preparation needed. While it was definitely possible to turn a very rusty disc into an interior standard piece of decoration, I would not recommend using a disc with that much preparation required (especially one which has been exposed to the elements as much as the one I used had)

·Use a 3D Printer with a larger build volume. Whilst my printer is more than sufficient to make the stand in two halves, there is still a visible line down the middle of the stand where the two halves have been joined together, despite significant effort to sand and smooth that area, so printing the stand as one piece would prevent this issue

If you have managed to make it this far through my Instructable… Thank you for reading! This project has been great fun to build, and now stands in pride of place on my desk (fingers crossed I won’t be missing any more lectures from now on!). If you have any questions, please don’t hesitate to message either in the comments below, or me directly – I will try to answer as best as I can!

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