Introduction: Car Security Hack
I use a steering wheel lock in my car as a deterrent to thieves. So far (touch wood) it has done its job.
Last weekend, it broke. The key to unlock it would not turn and it took ten minutes of two engineers jiggling the key, the lock and the wheel before it was undone.
A piece of equipment like this absolutely has to be reliable, so I was going to have to replace it. Then I realised that since its primary function is as a visible deterrent, it didn't actually have to function as a lock, it just to look like one.
Step 1: Dismantling the Device
The device works by having an extensible bar which ratchets out between opposite rims of the steering wheel. This extensible bar is retained by a pin.
I could not find a way to remove the extensible bar pin as it seemed to have been installed at manufacture before the covering was applied to the far end of the device.
I broke the pin off by extending the bar to its limit very quickly to apply a transverse shock to the retaining pin. This took a few iterations but eventually the bar slid right out.
Then I went to remove the lock.
The inner barrel of the lock rotates, and there was a small pin visible on the outside of the lock housing. I assumed that this pin was what prevented the outer lock barrel rotating under torsion.
I marked the position of this pin with an ink dot on a piece of tape and then drilled it out with a 4mm (5/32") bit.
The pin was obviously extremely hard as the bit slipped off, but the steel around the pin was obviously very soft as the bit chewed down into it very easily.
Since the pin wasn't going to play, I drilled a hole in the steel either side of it and then used a punch to knock the pin sideways and out.
Step 2: Removing the Lock Barrel
After the pin was removed, the lock barrel was eased out.
The bolt which locked against the ratcheting bar was removed.
The inner and outer barrels were separated, which released the dozen lever and spring sets which formed the match for the key. They can be thrown away.
The lock barrels were reinserted into the steel housing.
The extending bar was slid back into the device.
Provided that the lock is put onto the steering wheel with the drilled holes hidden from view by the centre of the steering wheel, there is no external indication that the lock is not fully functional.
Step 3: What Failed, and What I'll Do Next Time
I tried a number of things which didn't make it to the final hack.
Unless the steering wheel is at the correct angle when the device is applied then the device will fall off, as there is nothing preventing the ratcheting bar from slipping back into the body of the device.
The first attempt tried to add some friction to the movement by jamming a piece of eraser into the housing where it would grip the ratchet. This sort of worked, but moved out of place whenever the ratcheting bar was moved.
The second attempt tried adding padding and friction to the ratcheting bar itself by various layers of tape (both duct and masking). This didn't work at all, as the difference between "no effect" and "jammed" was impossible to find.
The final attempt involved applying and expansion to the ratcheting bar by winding a spring and slipping it into the device before the bar. This was a bit of a Hail Mary and it didn't come. Dumb idea.
Knowing the internals of the device as I now do, a repeat of the hack would be much quicker to implement, more useful and more useable.
- Drill a single 4mm hole down beside the lock barrel retaining pin
- Punch the pin sideways
- Remove the lock
- Remove and discard the tumblers from the lock
- Reassemble, filling the drilled hole with epoxy or hot glue and painting the surface
This would retain the ratchet mechanism, but mean that anything (including a screwdriver) would open the lock.
You live and learn.