PH Origins: Traction control
Traction control ruining your fun? You've an engineer from Surrey to blame for its existence...
On the ground, ever-increasing power, speed and weight rapidly exacerbated traction issues. This was particularly problematic for locomotives; if too much power was applied from a dead stop, the wheels could break free and spin on the rails - resulting in damage to the track and potentially overspeeding the locomotive's powertrain.
More power and heavier trains and payloads, unsurprisingly, caused this destructive slip to happen more frequently. Outside of dumping sand on the rails to boost traction, operators had to rely on the driver's skill to avoid significant damage.
James Edward Francis, an engineer based in Surrey, took a particular interest in the problem. 'Slipping of the wheels involves unnecessary wear of the wheels and rails, or roadway, and is also a waste of energy', he stated, earning him a place as being one of the first on record against burnouts or drifting.
The system functioned in a similar, albeit less complicated, fashion to today's traction control systems. A centrifugal governor was connected to the driving axle, while another was hooked to an unpowered wheel or axle. The governors were linked - by a specially engineered mechanical or electromagnet-based system - allowing for a comparison of the rotational speeds of the powered and unpowered wheels.
If a driven wheel began to spin much quicker than an unpowered one, the difference in the governor speeds would cause the output of the linkage system to change. This action would then be used to trigger a reduction in power output, allowing traction to be re-established and acceleration to continue.
While the focus of the patent was on electrically driven rail vehicles, the system was designed to be applied to anything that could move under its own power - with mentions of cutting fuel, or altering the mixture, in order to regulate the power output of vehicles equipped with an internal combustion engine.
The automotive market had to wait for the development of compact, affordable solid-state electronics until a production traction control system was viable, however. Buick was the first past the post, with its exclusive 'Max-Trac' set-up, which arrived in late 1970.
It was eventually offered on all of Buick's full-size models, including the LeSabre and Riviera, and it functioned like Francis's system. One sensor looked at the speed of the front wheel, while another on the output of the transmission measured the speed of the rear axle. A transistor-based computer compared the readings and, if a major difference was detected, the ignition would be cut and torque interrupted.
It cost the equivalent of £42 at the time - around £600 today - and, according to a Popular Science feature, 'seemed like magic'. The system was phased out after a few years, though; as emissions control regulations grew tighter, catalytic converters were required. The Max-Trac's spark-cutting approach resulted in unburnt fuel making its way into the exhaust, which would ruin the catalytic converters. Consequently, seeing no other sensible way to implement the system at the time, Buick quietly dropped it.
The advent of more advanced electronic fuel, ignition and brake controls resulted in traction control making a comeback in 1986, as it could be enforced without dousing catalytic converters with fuel. As driveability and safety demands increased, its fitment became increasingly common - and countless tyres cried out in relief.
Lewis Kingston
There wasn't anything in place to reduce power automatically in order to re-establish traction, however, if the wheels broke free. So, if you were on a slippy surface, you could probably pull off some quite spectacular pirouettes.
The later GKN FFF100 prototype had upgrades to further boost traction (I think they modified the way the transmission behaved and upgraded the differentials), in '72, but still no traction control system.
Do shout if you see a reference that says otherwise, though!
Interesting article, cheers.
IMO in a real sports car it's fine to leave it up to the driver to control wheelspin, but in anything else TC is valuable.
Yes, agreed – a great aid for general driving.
If a driven wheel began to spin much quicker than an unpowered one, the difference in the governor speeds would cause the output of the linkage system to change. This action would then be used to trigger a reduction in power output, allowing traction to be re-established and acceleration to continue.
It compared the rotational speeds and 'somehow' changed the linkage system. Details, we need details!
The other primarily proposed alternative would use small DC generators coupled to the unpowered and powered axles. Francis envisioned that their armature currents would 'oppose and normally neutralise', so that when slip occurred the resulting current would energise a solenoid which would interrupt the power circuit – or be used to trigger some other form of interruption.
Some other variations were proposed, including an electro-pneumatic option (designed to integrate with the Westinghouse air brake, it seems) – but they all functioned on the same basic principle of comparing the difference of the driven/undriven wheels/axles and then instigating a change.
It compared the rotational speeds and 'somehow' changed the linkage system. Details, we need details!
Gassing Station | General Gassing | Top of Page | What's New | My Stuff