Displacement activities

Strangely, having realised that I’m now imminently facing more treatments, I retreated from all the obvious things that I ought to be doing, and vanished out into the freezing cold garage, and proceeded to disassemble my toy car. It’s been sat out in the garage with a broken speedometer for several months, barely touched, but this last set of news somehow galvanised me into action.

In the course of a few short hours I’d stripped out the entire interior, removed the transmission tunnel, and exposed the gear linkage and speedometer sensor, removed the broken sensor, adjusted the gear linkage détente, put it all back together again, fabricated a new sensor mount on the front bearing carrier, re-run the sensor wiring, and bonded some rare earth magnets to the disc rotor.

Unlike trying to monitor the propshaft rotation, monitoring the disc rotor works beautifully; the propshaft has a lot of play in it, as it connects the engine and gearbox which are both on flexible mounts, whereas the disk rotor doesn’t move in relation to the front bearing carrier at all. It’s possible to closely align the sensor to the magnets, and get a superb signal to drive the speedometer.

As a result, I can now (for the first time ever) see exactly what speed I’m travelling at in the car, and it’s somewhat eye-opening. I always knew the car was fast, but when the soft rev-limiter engages in 2nd gear, the car is already approaching 70mph. It’s completely mental. And exactly what I need at the moment!

The only question now is whether the epoxy resin I used to bond the magnets to the disc rotor is strong enough to keep everything in place, or if the magnets will eventually come loose. I’m currently pretty sure it’s the former – but as they say, pride comes before a fall!

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