Diesel tachometer senser (mechanically driven)

Julian

unread,

Oct 28, 2009, 5:45:23 PM10/28/09

to

Please have a look at the first item in this link:

http://www.aetnaengineering.com/tachometer-senders-sensors.asp

I wonder if anyone could point me towards a supplier of something similar in
the UK?

It's for a Rolls Royce (Perkins) Eagle engine but I could probably adapt
anything 1/2 suitable to fit. Too old for most scrapyards nowadays :-(

Cheers Julian.

mark

unread,

Oct 28, 2009, 6:07:34 PM10/28/09

to

looks very similar to the rover pg1 gearbox one .

the gearbox is found on the 2 ltr T-sreries and diesel engines fitted
to 220 420 600 and 800.

all the best.markj

c...@nospam.netunix.com

unread,

Oct 28, 2009, 6:22:47 PM10/28/09

to

The Eagle was used in a wide range of British trucks including ERF.
Dealers may still have some old stock.

Julian

unread,

Oct 29, 2009, 2:56:56 AM10/29/09

to

"mark" <aboard_...@yahoo.com> wrote in message
news:dc1043f5-23f5-480c...@b2g2000yqi.googlegroups.com...

Thanks, will check this out.

Julian,

Julian

unread,

Oct 29, 2009, 2:59:22 AM10/29/09

to

<c...@NOSPAM.netunix.com> wrote in message
news:hcag7n$lt0$1...@news.albasani.net...

Yes, it's from an ERF E12 (12 litre Roller) I've tried a dealer or three,
they all laugh, I've a few more scrapyards to ring today. I think you're
confusing dealers of old to the ones today run by the bean counters. You're
lucky if they have an oil filter on the shelf nowadays :-(

Julian.

Michael Clarke

unread,

Oct 29, 2009, 5:44:08 AM10/29/09

to

Try Speedograph Richfield Ltd at
http://www.speedograph-richfield.com/

--
Michael Clarke

THE DOUGLAS STATIONARY ENGINE RESOURCE (admin)

unread,

Oct 29, 2009, 7:44:08 AM10/29/09

to

As an ex-electronics engineer by profession, I would offer the warning that
the electrical output pulses would need to be of the correct amplitude and
duration to "match" with whatever it is feeding into.
Sorry if I am "teaching my granny to suck eggs", but thought that a comment
in time may prevent you from spending money on something which may not work!

--
Peter Chadbund
The Douglas Stationary Engine Resource
www.duster.org.uk

"Julian" <j...@supanet.com> wrote in message
news:5Y2Gm.16567$MG6....@newsfe13.ams2...

moray

unread,

Oct 29, 2009, 7:56:06 AM10/29/09

to

What about taking a feed from the alternator W terminal?
Or have you already got a petrol tacho?

moray

"Julian" <j...@supanet.com> wrote in message
news:5Y2Gm.16567$MG6....@newsfe13.ams2...

Julian

unread,

Oct 29, 2009, 9:52:26 AM10/29/09

to

"THE DOUGLAS STATIONARY ENGINE RESOURCE (admin)" <ad...@duster.org.uk> wrote
in message news:8c2dnU1hAoKQHXTX...@brightview.co.uk...

> As an ex-electronics engineer by profession, I would offer the warning
> that the electrical output pulses would need to be of the correct
> amplitude and duration to "match" with whatever it is feeding into.
> Sorry if I am "teaching my granny to suck eggs", but thought that a
> comment in time may prevent you from spending money on something which may
> not work!

That's a fair point, and one that hadn't escaped my attention. The trouble
is I don't know exactly how it works or what output to expect. It ''feel''
(when you turn it) like an old generator that used to rest on a bicycle
tyre. I'm guessing that it's a simple AC alternator, frequency proportional
to RPM? A fair assumption or not?

Cheers Julian.

Julian

unread,

Oct 29, 2009, 9:55:44 AM10/29/09

to

"moray" <sp...@spam.com> wrote in message
news:HpfGm.2268$zy1...@newsfe14.iad...

> What about taking a feed from the alternator W terminal?
> Or have you already got a petrol tacho?

There's no W terminal, already checked :-( The ERF EC's changed to the W
terminal, mine is just pre W terminal.

I'm not in the least bit sure if a W terminal output would match that of the
tacho genny that I have at the moment?

Julian.

PS, found a breakers in Darwin (not too far from me) with a few Rollers
lying around - say I'm welcome to come and have a look-see.

Julian.

ChrisQ

unread,

Oct 29, 2009, 1:56:20 PM10/29/09

to

How many wires coming out of it ?. That is, is this an optical, hall
effect or other magnetic sensing device internally. If you can get the
lid off it, can you post a jpg somewhere so we can see the internals ?.

If it's two wire, then it probably uses a simple magnetic reluctance
sensor. Otherwise, some electronics inside...

Regards,

Chris

Julian

unread,

Oct 29, 2009, 3:31:11 PM10/29/09

to

"ChrisQ" <me...@devnull.com> wrote in message
news:8HkGm.21374$k74....@newsfe17.ams2...

It's a simple two wire jobby (non polarity sensitive) . I think it's
probably two wire and not one wire because the truck does not use the
chassis as a return circuit for electrical equipment. There's nothing fancy
about it at all. Unfortunately it is assembled in a way that makes taking
apart without damage impossible :-(

I've tested it with an AVO. So far I've spun it up with the cordless drill
and measured Hz, Volts AC & DC but I've not found an output that seems to
correlate with RPM. However this sort of thing isn't really by forte and
don't really know what I should be looking for.

I've proved the integrity of the wiring between tacho genny and instrument
panel (which is made of unobtanium) so I'm just problem solving by process
of elimination really.

Thanks Julian.

Dave Liquorice

unread,

Oct 29, 2009, 4:54:40 PM10/29/09

to

On Thu, 29 Oct 2009 19:31:11 -0000, Julian wrote:

> I've tested it with an AVO. So far I've spun it up with the cordless
> drill and measured Hz, Volts AC & DC but I've not found an output that
> seems to correlate with RPM.

It's not just a simple switch is it?

--
Cheers
Dave.

David Billington

unread,

Oct 29, 2009, 6:23:02 PM10/29/09

to

I've no idea if it's suitable but a number of VWs have an electric
sensor that plugs into the gearbox, I think it's a hall sensor. The
beauty is some of the vehicles using the gearbox have a cable drive and
others the electric sensor which connects to the same gearbox fitting as
the cable drive. The electric sensor unit is driven by a square shaft
about 3mm AF which fits into the gearbox in the same way as a cable
would. My VW has it and is a 1995 Passat. Might be adaptable.

Jules

unread,

Oct 29, 2009, 6:43:28 PM10/29/09

to

I wouldn't expect a mechanical switch, but a hall sensor's a distinct
possiblity.

If a ahll sensor then it should give an AC waveform when the shaft's
rotated I would have thought, but how clean that signal would be or what
amplitude I don't know - maybe an AVO's expecting a nice clean sine wave
or something, and what the sensor throws out is a series of spikes...
putting it on a 'scope might be the only way to truly test it.

ChrisQ

unread,

Oct 29, 2009, 7:20:39 PM10/29/09

to

It guess it could be a hall / solid state sensor with an open collector
output, which would need a load resistor at the other end of the wire.
To check this, are both leads the same colour and if not, what do you
get if you measure the volts at the device the sensor plugs into ?.
Also, what does the avo read on ohms range if you turn the shaft slowly
by hand ?.

It's probably unlikely to be a mechanical contact switch as the life
wouldn't be anything like good enough...

Regards,

Chris

Dave Liquorice

unread,

Oct 29, 2009, 7:40:06 PM10/29/09

to

On Thu, 29 Oct 2009 17:43:28 -0500, Jules wrote:

>> It's not just a simple switch is it?
>
> I wouldn't expect a mechanical switch,

Reed switches will take the number of operations required but might
not be quite robust enough for use on an engine.

> but a hall sensor's a distinct possiblity.

That is a distinct possibilty. This particular senor beinga two wire
device it may not produce a sensible output unless it has the proper
bias voltage/current.

--
Cheers
Dave.

Nov 2, 2009, 7:36:55 PM11/2/09

to

"Julian" <j...@supanet.com> wrote in message

news:14mGm.32356$fq2....@newsfe18.ams2...

hello Julian painted my mower now, changed the engine, hopefully the rain
will stop soon so I can give it a whirl.
Thanks!
Gill electronics make the sensors for the new Triumphs
http://www.gill.co.uk/. they have something that 'looks' similar.

Also I have recently had a crankshaft magnetic pick up rewound by
http://www.westcountrywindings.co.uk/services.htm

A magnetic sensor should have 'some' resistance, when you put an ohmmeter on
it. when you put the sensor near to a lump of metal the resistance will go,
or vice versa. All the best B