Tachometer

[Robotstar5]

So I'm looking for a tacho to put on my tractor, there is an "official" version driven by a rubber wheel on the fan belt for north of £300 so that's out

So I started looking at automotive or marine options, but they all seem to be driven by a pulley sensor (proximity switch) or off the "W" terminal on the alternator and I have a dynamo

I was hoping to find something driven by the LT side of the coil/points and wondered if the forum collective had any suggestions? (it's a 12 volt positive earth system if that makes any difference)

Cheers.

 

[jerrytug]

If you want proper tractor analogue stuff, I have no idea. But:
Can you glue a tiny magnet onto your flywheel pulley, or anything else turning at crankshaft speed?
Then, can you mount a little (Hall effect) sensor close to it on a bracket?
Thirdly, could you tolerate a digital display? You need a tiny amount of 12v DC for power.

I have an old Gardner 4LW on my barge, and bought the entire rev counter kit from Chyna for £20. Genuine ones are mega bucks and probably less reliable over one lifetime.

 

[Cobbler]

Put in electronic rev counter on eBay & lots come up.

 

[Lewis_RX8]

If you want proper tractor analogue stuff, I have no idea. But:
Can you glue a tiny magnet onto your flywheel pulley, or anything else turning at crankshaft speed?
Then, can you mount a little (Hall effect) sensor close to it on a bracket?
Thirdly, could you tolerate a digital display? You need a tiny amount of 12v DC for power.

I have an old Gardner 4LW on my barge, and bought the entire rev counter kit from Chyna for £20. Genuine ones are mega bucks and probably less reliable over one lifetime.

Thats how I did it on my lathe

 

[Ubique]

Thats how I did it on my lathe

Similar to what I did on my Fobco Star.

 

[Johnnybravo]

Vdo used to make one that ran off the coil. Had one on my air cooled beetle

 

[Cobbler]

Vdo used to make one that ran off the coil. Had one on my air cooled beetle

I think most of the after market ones do, or did. I’ve had a couple that had 2 wires, one to each terminal of the coil.

 

[Woody.v8]

Has it got an alternator? Some older stuff used to have a tach terminal.

 

[Wildefalcon]

Single tooth trigger wheel on the crank pulley, crank position sensor on a bracket?

 

[carbon]

Has it got an alternator? Some older stuff used to have a tach terminal.

So I started looking at automotive or marine options, but they all seem to be driven by a pulley sensor (proximity switch) or off the "W" terminal on the alternator and I have a dynamo

It’s not that modern, it has a dynamo and is positive earthed. Lots of older tachometer’s just connected to the coil connections.

 

[carbon]

I’ve found this on eBay, not studied all the description but seems suitable
Rev counter

 

[CompoSimmonite]

One option, but no idea how expensive, would be to source a Lucas C40T dynamo off an old car such as MG which had a rev counter cable output on the rear.

 

[Robotstar5]

Put in electronic rev counter on eBay & lots come up.

I tried that and probably the best type are like this but will need a sensor.

 

[Robotstar5]

I’ve found this on eBay, not studied all the description but seems suitable
Rev counter

Thanks, now on my watch list

 

[Robotstar5]

Vdo used to make one that ran off the coil. Had one on my air cooled beetle

I did search for that type, but they seemed to achieved "classic" status with prices to match

 

[Robotstar5]

Thanks for the replies, I will have to look for a way to mount a discrete sensor which will be fun on something with a wiring harness consisting of four wires!.

 

[brightspark]

why do you need one are you running critical stuff off the pto or just fancy one

 

[Robotstar5]

why do you need one are you running critical stuff off the pto or just fancy one

Just fancied one to see what the engine was doing

 

[MattF]

Just fancied one to see what the engine was doing

If it's making a noise, it's running.

 

[brightspark]

i once fitted one to my stockcar .dunno why i never looked at it . just flogged the ass out of the engine in order to win no matter what it revved to