Tacho - Bike Computer

[Refueler]

So based on anothers thread ages ago - I thought I'd have a look at this.

Ebay had plenty available and at cheap as chips prices. I paid pennies for one from Hong Kong.

It's not fitted yet - as I have to decide how to mount the sensor and also clean up crankshaft pulley for epoxying magnet to.

One of the concerns was the ebay listing indicated that RPM display wouldn't go high enough. So I thought - OK - run it on MPH setting with smallest wheel diameter and create a table using my hand-held tacho to calibrate.
Well with item in hand, I concocted a way to test it ... simple - wave magnet back and forth across the sensor mimicing wheel ... Wow - I got the RPM display up to 3800 ! Well over what's needed for my engine. No need for conversion, no need to play with units. Dead straight RPM display.

So now is the task of sorting how to mount it.

Item was : Bike Computer

Hand Held tacho that will check it : Hand Held Tacho

 

[Shearwater]

Good timing, thanks. My 5" diameter clock rattles when shaken and doesn't work when the engine runs but I have a bike with a computer....and last night I spent the evening getting depressed at the prices of tachos. Now I know what to do!

 

[[32511]]

We used a bike computer on the "soapbox" gravity racer we built for Goodwood Festival of Speed. At speeds of over 60mph, and 20" wheels, the contacts in the sensor soon gave up. I suspect at engine revs the life may be brief- let us know the findings.

 

[ridgy]

Bike computers are magnetic so there is no contact...Why would it give up?

 

[[32511]]

The one we had used a micro-switch in the sensor, operated by the magnet. The magnet needed to be within about 12mm of the sensor. If there is one which doesn't rely on micro- switches, it could well be practical.

 

[Bodach na mara]

Some use reed switches, but even these are supposed to be good for tens of millions of operating cycles. I believe the modern ones use Hall effect sensors.

 

[Refueler]

[ QUOTE ]
The one we had used a micro-switch in the sensor, operated by the magnet. The magnet needed to be within about 12mm of the sensor. If there is one which doesn't rely on micro- switches, it could well be practical.

[/ QUOTE ]

This has to have ( instructions say ) 1mm gap between magnet and sensor. This is going to difficult to set-up. But I'm wondering whether a stronger magnet could be substituted so to increase the distance range. Hand testing indicated a max distance of 2mm with original.