Well, I finally found a treadmill on eBay that was the right price (£15) and close enough (10 miles away).
This is all that was left of the sensor
The only problem was that the sensor was faulty – for faulty read smashed to bits, the picture on the right here shows the only remains. No serial or part number or even internals to figure out how the sensor worked. I should point out at this juncture that it’s a manual treadmill and does not need plugging into the mains. Being battery-powered I was fairly safe to poke around with the gubbings without risk of electrocution.
I accidentally discovered that when the two wires running to the sensor touched that the readout was triggered (two touches = 1 metre) and with a bit of internet research I found out that there are basically two types of magnetic sensor used by treadmills. The Hall effect sensor relies on a current created by the path of a magnet and is the kind you find on bicycles. The other, pictured left, is a simple switch that is operated by the proximity of a magnet, this is what I needed to fix my treadmill (Maplins – £1.79)
, so with a deft bit of soldering and a length of old speaker wire I found in a box in the garage I folded the connectors to fit the remains of the sensor and soldered on the speaker wire as shown right. The only problem now was that the whole thing was flapping about inside the remains of the old sensor looking like it would fall apart with the first knock, so back to the garage for 
the hot glue gun!
Being careful not to burn my fingers, I glued the sensor, connections and the wire into the remains of the sensor and added a bit more glue around where the wire goes in for added protection and left it to cool – as shown left.
The finished product whilst looking a bit Heath-Robinson seemed to 
do the trick as I screwed it back into place as seen here on the right.
I routed the wire so that when the treadmill is folded away when not in use it does not stretch and damage the sensor or wire. The magnet can just be seen as the silver circle in the flywheel just below the sensor in the picture. Every two passes by the magnet causes the 
distance meter to advance a metre. I taped up all the connections for good measure and gave it a little test.
The whole repair seems to have worked well so far, so total cost was £15 for the treadmill (plus collection) and £1.79 for the magnetic sensor from the good people at Maplins and only took about half an hour to complete. As I said earlier, this is a manual treadmill and does not require any mains power, had it been a mains powered treadmill I would have had to have been a lot more careful as mains electricity can and does kill. There are a number of treadmill parts sellers on eBay, but I was not able to determine w
hat type of sensor (Hall effect or switch) they were offering and at about £20 a sensor it would have cost more than the treadmill itself, double if I ordered the wrong type. The final picture shows the tools I used in fixing my treadmill, comprising ‘Old Faithful’ my soldering iron, a hot glue gun, solder and wire cutters.
Just a reminder – this is not a ‘how to’ site, but a blog of how I fixed a particular problem. If in doubt, contact an expert – you can do untold damage to yourself if you start playing about with thing like mains power etc. You have been warned!
I am off for a jog in my garage – cheers!
I’m fascinated by the concept of a ‘manual’ treadmill (as distinct from the sort you work with your feet)?
Its fair to say that you could replace the word ‘manual’, with the word ‘cheap’.
The belt is set at about 15 degrees to the horizontal, so each step is an upwards step and in the best tradition of Newton, equal and opposite forces cause the belt to rotate when you step forwards.
The trick comes in not leaning too far forwards as this causes uncontolled acceleration and a floor/face interface.
… thus demonstrating the athletics corollary to 3rd Law of Motion- “Entropy increases randomly and rapidly when you inadvertently impinge on the environment ”
BTW – I’d advise staying with Newton. IF you can get into a regime where Relativistic Effects become noticeable, you have probably over-trained?
There was a fit fencer called Fisk
Whose ripostes were surprisingly brisk.
So fast was his action, that Lorentz’s contraction
Reduced his epee to a disk
Very good sir!
For a number of reasons, firstly back in my Kendo days I would swear that some of the Shinai (wooden hitting stick) was travelling at near light speed when some of the more experienced opponents hit me with it. We were told that experienced exponents of the art could make the tip of the Shinai move at around 200 mph – I have no idea if this is true, but I know they can really move when they want to.
Secondly, I have always been facinated by the Hafele–Keating experiment, taking an atomic clock for a flight around the planet and measuring the time shift generated by this.
I like to think the relativistic effect is what inspired the ‘light speed’ effect in star wars, I could be pushing it a bit with that though!
I reckon a 6ft stick would need to be ‘twirled’ at about 8Hz/ 480rpm for the tip to reach 200 mph. Just might be possible with a “shaft + chain-linked-head” weapon such as flail or Morningstar ?
But there are claims that the “Crack” of a whip is due to a ‘travelling loop’ formed in the lash which forces the airflow to exceed Mach 1
(BTW – my limerick is deceptive – If Mr Fisk’s epee HAD shortened as described, it would also have become infinitely massive)