It’s been a labour of love, but the hours of elbow grease Toby Penter has put into restoring his Sinclair C5, including making its lighting safe and roadworthy, have very much been worth it.
The steam locomotive. The computer. The jet engine. Many and varied are the technological achievements of British industry. One that didn’t quite make the top 10, however, is Clive Sinclair’s eponymous tricycle: the Sinclair C5.
An unholy union of a Robin Reliant and a plastic bathtub, many and varied were the C5’s issues. Whilst far from its greatest issue, the lighting on the vehicle is considered wholly substandard by those in the know – and so I set out to improve it.
THE VEHICLE SUMMARY
Pitched as ‘the car of the future’, the C5 was a small, one-person, electrically assisted pedal cycle.
As you can see from some of the photos, it bears a greater resemblance to a recumbent bicycle than a conventional bike, and it is, of course, on three wheels.
Launched in 1985, it was manufactured by Hoover, for Sinclair Vehicles, with design input by Lotus cars.
It was invented and pioneered by Sir Clive Sinclair, who was already famous and wealthy from his development of computer systems such as the ZX Spectrum. Prior to all of this kicking off, Sir Clive was regarded as a generational innovator, with his name appearing alongside Edison, Nicola Tesla, and Brunel.
More than 14,000 C5s were optimistically produced in the first production run. It was expected that a 100,000 might be made by the end of 1985.
Unfortunately, the consumer had slightly different ideas, and only about 3,000 were sold in the initial wave. Following price reductions, the involvement of resellers, and a scheme where you received a free C5 with every washing machine bought, around 8,000 were ultimately sold.
It was described as ‘one of the greatest marketing bombs of postwar British industry’, and ultimately the venture was such a failure that Sinclair Vehicles declared bankruptcy, and it was Sir Clive’s last big project before fading into relative obscurity.
WHY DIDN’T THE VEHICLE WORK?
The launch was fraught with challenges. On the actual launch day, a couple of dozen C5s were rolled out at Alexandra Palace, demonstrated, and then handed over to journalists for a test drive.
The journalists drove through the park, down a hill – and then were unable to get back up the hill, as C5s are absolutely terrible at dealing with any kind of incline.
The marketing was also generally messy, with the initial belief being that Sir Clive was working on a full electric car, and then the vehicle eventually launching in an icy British January, where an open-topped vehicle wasn’t practical or enjoyable.
For a bit of extra money, you could purchase a ‘rain cheater’ – a sheet of unflattering tarpaulin that was somewhere between a coat and a tent.
The range of the vehicle was relatively poor and, to get the most out of it, you were required to purchase an additional battery at significant cost.
The vehicle was generally regarded as unsafe, as users are low to the ground, close to traffic (and nice leaded exhaust fumes!) and have limited visibility. The original boot came in grey, which was hard to spot, and the second half of the production run was done with white boots to improve visibility.
The issues don’t stop there. The size of the vehicle, its stability, gearing (or lack thereof), comfort and reliability were all criticised.
When braking, the vehicle had a knack for swerving into traffic. Significant elements, such as boots and wheel caps, tended to fall off. The vehicle has very limited ground clearance, with significant underslung parts prone to wear, is made of a wholly unsuitable material, and cannot be reversed.
If pushed backwards too quickly, the motors tend to catch fire. And the stock vehicle did not come with some desirable safety features, such as indicators, wing mirrors, and a horn.
LIGHTING FOR SAFETY
To light the vehicle, the first step was developing an understanding of the reasons and rules for vehicle lighting and understanding how the C5 measures up.
So, why do we light vehicles? Quite simply, to see, and to be seen. We are interested in improving our ability to see the world around us, and we are interested in making sure the world around us can see where we are, what we’re doing, and where we’re going.
The legal framework for vehicle lighting is then set out in the Road Vehicles Lighting Regulations of 1989. This legislation, supplemented by the highway code, sets out how vehicles should be lit.
Being a cycle, I have then benchmarked the C5 against the requirements for bikes. The bike regulations are further supplemented by statutory instruments, and standards such as BS 61023, which set out how they must be lit.
The most recent set of statutory instruments concerning bikes were amendments to existing legislation to allow the use of flashing bike lights, for instance.
How does the C5 stack up against the lighting requirements? Well, it doesn’t. Under the current regulations, bikes require a white front light, a red rear light, a red rear reflector, and amber/yellow pedal reflectors.
The C5 has a yellow front light (permissible for cars, but not for bikes), it does have a red rear light, but without a separate red rear reflector, and there are no amber/yellow pedal reflectors (however, there are reflectors running up the side of the vehicle).
So, there’s some work to be done here.
LIGHTING FOR AESTHETICS
Why do we light vehicles for aesthetics? Quite simply, because we like it! There has been a big development in the last 30 years in ‘car culture’.
Lighting vehicles for aesthetic purposes, as status symbols and statement pieces, has become much more commonplace. Most famously, films such as the Fast and Furious series have immortalised this style of vehicle lighting – undercar neons, strip lighting for features, and avant-garde headlights are all typical of this style.
Beyond that, there are famous, culture-defining vehicles that have famous lighting schemes associated with them. The Back to the Future DeLorean famously has a strip of lighting to the front, side and top (as well as a bright yellow flux capacitor!). The signature feature of a vehicle from the Tron franchise is thin, panel-hugging strip lighting that gives a distinctive look.
But I hear you ask: ‘Toby, what is the British legal framework behind aesthetic vehicle lighting?’. Fear not, I’m getting there!
We are back to the Road Vehicles Lighting Regulations of 1989. Vehicles are not permitted to have blue, red and green lighting on a vehicle, as this is lighting that can be used by the emergency services.
Other than that, you are just not allowed to have the actual illuminated surfaces visible from the rear of the vehicle; that is to say, the glow is fine, but you should not be able to see the source.
THE RELIGHTING PROCESS
Before I could get into the relighting process, there was quite a lot of work to be done. I bought my particular C5 off Cambridge University, who were using it, at the time, as a test vehicle for a rocket powered by chip fat.
It was, at one time, on the Brainiac Science Abuse TV show, which was a mainstay of my childhood, if you haven’t seen it.
However, this meant that, when I received it, the vehicle was in a pretty sorry state. A lot of grinding, ultrasonic baths, bending of parts, and about a tube each of thread lock and grease later, the vehicle was in a condition where I could begin to think about lights.
It would also be rude not to mention the good work of C5 Depot (c5depot.co.uk) here – who provided parts and expertise required to do the initial repair, service the motor, and install additional electronics.
So, on to the relighting. There were two key themes I wanted to push when doing the relighting.
Firstly, to improve the safety of the vehicle and, secondly, to see if I could enhance the aesthetics of the vehicle – or at least do something different with it.
On safety, it comes back to those key themes from the start – seeing and being seen. This meant implementing a new (white) LED bulb for the front of the vehicle, replacing the old bulbs. The previous ones may have been fantastic in 1985 but weren’t illuminating anything in 2025. So, new bulbs front and back.
I also installed indicators. Now, you can purchase original Sinclair C5 indicator kits on eBay (other reselling sites are available) – however, these are around £300. Not wanting to burn money and knowing full well that a bike shop would do a new set of bike indicators for £25, I settled on the cheaper option.
This prompted a long foray into 3D modelling and 3D printing, to design parts that slot into the old flag holders at the back of the vehicle. This should been a relatively simple part – but required more iterations than I’d like to admit for myself and my friend to figure out.
Lastly on safety were brake lights. It’s very helpful to be able to tell when the vehicle in front of you plans on slowing doing – so, once again it was a case of going to the 3D printer to create a part that would enable me to sling a brake light under the vehicle.
The light I used is, again, intended for cycling applications, and works on a small gyroscope within the light. This detects when you are slowing down and gets brighter accordingly.
Aesthetically, I hope the pictures speak for themselves. I’m not much of an architectural lighting designer, so you’ll have to forgive me for my efforts here, but there were a couple of pieces of inspiration that were key to me here.
Firstly, the Fast and Furious look – that is to say, underslung neons that give the impression of a street racing car. This was achieved by using a Buck Converter to step down the 24V circuit and create a new 5V circuit around the vehicle, which enabled me to use off the shelf RGB USB strips to create a consistent under-glow.
Secondly, there is the Cyberpunk/Synthwave Tron look – which I had hoped to achieve with electro-luminescent (EL) wire mounted to the key accents of the vehicle.
Whilst I was very keen on this one, practical constraints held me back here. The PU composite material of the C5 is very difficult to adhere to, so it was impossible to attach anything to the body of the C5 without either damaging the finish, or by using an overabundance of attachments which hurt the daytime aesthetics.
The EL wire was a serious challenge, and one I’d like to revisit in the future – potentially by wrapping the vehicle to give it a new finish that is easier to adhere to.
Conclusion
Overall, I was very happy with the scheme that was developed, and hopefully the images do it justice.
Whilst it’s rare for me to use the vehicle at night, I’m confident it’s now slightly safer if I want to do so. And with the new aesthetic lighting, if I am out at night, I’m equally confident it will look as ridiculous as ever.
Toby Penter BA (Hons) IEng MILP is a principal lighting engineer at WSP
This is an abridged version of the article that appears in the February edition of Lighting Journal. To read the full article, simply click on the page-turner to your right.
Image: Toby Penter’s C5, courtesy of Toby Penter
