Looking towards the corner of the room, I keep finding myself saying "Oh God, what have I done?" The space is occupied by an elaborate looking tricycle from the mid eighties, the Sinclair C5.
Sinclair, I've heard that name before...
It's pretty safe to say that Sir Clive Sinclair was a chap who looked forwards, as not only was he a successful entrepreneur, but often credited as an inventor. The Sinclair brand was first unveiled publicly in 1961 as Sinclair Radionics, initially selling radio kits via mail order. Whilst Sinclair Radionics saw some success with products such as the Sinclair Executive pocket calculator, the business ultimately suffered financial difficulties and was broken up. Clive went onto found Sinclair Research which went onto produce the immensely successful Sinclair ZX Spectrum microcomputer, which put personal computing into the homes of the masses for the first time. I've covered the story of the ZX Spectrum previously, and it's probably the reason why the Sinclair brand is so well known.
So what's a C5?
The Sinclair C5 was Clive Sinclair's foray into the vehicle market. It's believed that Clive had taken interest in the possibility of developing an electric vehicle since the 1950s, and carried out research throughout the 1960s and early 1980s. This led to the Sinclair C5 in 1985 which was released as a personal vehicle, billed by some as the transportation of the future.
Fundamentally, the C5 is an "Electrically Assisted Pedal Cycle" (EAPC) or known these days as an e-bike. Rather than two wheels, it has three and so is considered to be a tricycle. Whilst in the 2020's e-bikes have become popular, in 1985 there was little appetite for such products. The C5 received unfavourable reviews, and garnered safety concerns from motoring organisations, which ultimately led it to be an unsuccessful product that some consider to be a major contributing factor to the downfall of Sir Clive Sinclair's businesses.
I wanted to give an introduction to the Sinclair C5, this is by no means the full story and there's plenty of other articles that cover it better than I could. This blog post isn't a history lesson, it's an introduction to my latest project.
My Sinclair C5
This is my Sinclair C5. Yes, I now own a C5. On the surface it generally appears to be in good condition, if a little dirty. Sadly it's not usable, there isn't a battery for operating the motor and the tires/inner-tubes have perished. The front headlight assembly is missing the lens/cover so the bulb is exposed and much of the reflective coating has degraded. From what can be seen without taking the C5 apart, there is some surface rust in places, particularly on the hardware fixings. The back wheels turn freely however, and when lifting the front and pulling the vehicle along, the pedals are rotating so the chain appears to be all ok too.
Getting the C5 home
This Sinclair C5 was listed on eBay for a reasonable price. I had seen another listing that was around the same price point, however to get something like this posted would probably be rather expensive so collection in person is the preferred way of picking the vehicle up. This particular C5 happened to be within a reasonable distance from base camp and so that's why I settled on this particular listing. It also in my view from the listing photographs appeared to be in better condition.
And so on one rather fine Saturday morning, I headed off to collect the C5. My partner was debating whether to join me on this trip however it's a good job she didn't as in order to fit the vehicle into the back of the car, I not only had to fold down the back seats, I also had to move the front passenger seat forwards to it's full extent. This didn't leave much leg room.
The seller was very kind at letting me drive into their back garden to get the car closer and helped to get it inside the car. The seller also shared with me some of the history of this particular C5, and how he intended to restore it himself but never got around to doing so. He wished me the best in the restoration of the C5.
The first job
The first job to be done was to give the vehicle a quick initial clean as it would have to be stored inside the house. To do this I simply used some warm soapy water and a sponge. A more thorough clean is required to lift more of the dirt, I suspect that utilising melamine foam (commonly known as Magic Eraser) will help with this, but I plan to do that towards the end of the restoration as a "closing out" job. We also cut some lightweight plastic sheets to put under the C5 when it was inside as to not dirty the carpets.
Quick electrical test
My intention with the C5 is to strip it down to nearly component level parts, or at least take it apart enough to get to the chassis (or Y frame as I believe it is known), but before taking tools to the vehicle I wanted to check to see if the Pod and electric motor were working. The eBay listing stated the lights were working, but didn't state explicitly about the Pod. Furthermore, the listing stated the motor wasn't tested.
I hooked up a bench power supply to the battery connection terminals for this initial test. Set at 12V/1A, this would be nowhere near enough to turn the motor but I would hope to see some sign that that the motor was OK by watching the voltage dip, or the current limiter become active. The rear light illuminated, the front headlight did not (I haven't diagnosed this further yet) but to my delight, the Pod also powered up. The Pod uses a ULA IC, an early programmable microcontroller (of sorts) which were also used in the ZX Spectrum. These ICs are susceptible to damage as they are electrically delicate. A non working ULA would result in a non functioning Pod.
A quick introduction to the Pod
The Pod is an instrumentation cluster on the inside front of the machine, it is used to inform the driver of the state of the motor and battery. It also provides some protection functions to the motor through monitoring the temperature of the motor. If the motor gets to hot, it audibly alerts the driver and can cut power to the motor to protect it. The Pod also has two bar LEDs, with the left showing how much current the motor is currently drawing, and the right being a rudimentary "fuel gauge".
Testing the motor
In order to activate the motor, a button is pressed on the left handlebar which drives a relay for the DC switching of the motor supply. When I pressed this button, nothing happened. I did a quick diagnosis and found that the switch is connected to the main wiring loom via some crimped quick connect terminals which had corroded badly. I was able to remake some form of connection as when I pressed the button the relay was energising and the left Pod LED illuminated with a green LED, but there was no motor movement. Currently, the motor is not working and so will need to be looked at further. All in all at this point I am happy enough with the state of the electrics to begin to dismantle the vehicle, but that's for another day.
Why a C5?
OK, time to address the elephant in the room. Why have I purchased this C5? eBay is a dangerous place for me when it's late into the evening just before bed. To be honest I'd looked into Sinclair C5's in the past and thought that they looked awesome. I wanted to try one but didn't know anyone with a C5. When I was at Electromagnetic Field 2026, I came across two C5's and as soon as I saw one in the flesh for real, I knew I wanted to acquire one. OK sure, I could have bought a working one right away, but I really wanted a small restoration project as it would just give that extra self satisfaction that I contributed into getting it going again.
Thank you for reading
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Thank you for reading,
Rachel x
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