another smiths speedo problem

[pinto pete]

my speedo neddle is erratic !

it jumps around at lower speeds.

is it the dip switches or the sender ?

i only have tomorow to fix it, i have sva monday morning !!!

[Flappa]

Where is your sensor located?

What gap do you have between the sensor and the bolt?

How eratic is the reading, and at what speed does it stabalise?

I've been playing with mine today

I set all switches to OFF = 2500 pulses/km (which is the minimum setting).

I put an alan key in my battery drill & held the sensor in front of it. Not the fasted of drills but got it to register. Even at this low speed the reading was very stable.

[pinto pete]

the sensoris on the cv joint.

i had no reading at all until i adjusted the gap to just over 1mm.

the needle flicks around up to and around 30

seems to be more stable after 30

[Flappa]

Just to be clear, when you say CV do you mean the rear lobro joint?

Have you checked the calc for the number of pulses?

It could be a problem if you have a setting for say 20,000 pulses/km, when actually your only giving it 3,500. This seems to be the problem I had, meaning that it wasn't getting enough pulses to read at all at low speed <20mph.

[pinto pete]

yes it's on the lobro

is the westfield calc  of 369087 / rolling circumference corect

[Flappa]

I don't know what that value relates to.

What I intend to do tomorrow is put some tape on the wheel & floor and mark a line on both. Role the car for 1 rev of the wheel and mark the second position on the floor. Measure between the 2 marks = tyre rolling circumference.

I calculated earlier that with an O/D of 560mm my tyre has a circumference of 1.75m.

1000m/1.75 = 568.41 revs per km.

6 bolts on the lobro = 6 x 568.41 = 3410 pulses/km. Look up the nearest value to this on the table provided with the speedo provides the settings for the 10 dip switches.

With the sensor on the lobro there's no need to account for diff ratio's etc.

Settings given to me by WF had 20,000+ pulses hence no reading when running at low speed.

[pinto pete]

i've printed off a table of pulses.

i've tried two ways of calcing rolling circumference.

there is a diference of 2" between them !!!

so i will have to measure the tyre tomorow to get a true circumference.

if i get a reading inbetween two pulses should i go over or under ?

[Flappa]

Pete,

The distructions just say use the 'nearest' value.

How do the values calculated compare to what you currently have? If you look up your current switch settings it will show the number of pulses its looking for.

Does this sound like it could be the problem?

[SparkyB]

Pete,

The erratic needle suggests that the sensor is not picking up all the torx bolt heads.  Do you have the sensor with the led on the back (Smiths Caerbont).  

I had quite a time getting the sensor close enough and at the right angle in order to register all 6 bolts.

In terms of pulse value mine was around the 5800 mark (I'll check today) and passed SVA  2 months ago..

Mark

[pinto pete]

i think i need to go down the garage and have a good fiddle

[SparkyB]

Just posted my dip switch settings in the other Smiths Speedo thread...

Good luck tomorrow Pete

Mark

[Flappa]

I've just been out in mine to test it. Drives gr8 but I'm still not sure that the speedo is reading right

Seems to be reading a bit fast.

SparkyB have you managed to check your settings yet

[pinto pete]

still not quite right

i have reset the gap to the lobro three times.

closer the beter, it' now between 1.2 and 1.5mm.

but it still dosn't read until it does 25-30 mph.

i have measured my roll/circum @ 69.6" 195/45/15.

used a flexible steel rule so it's quite acurate.

how many feet in a mile

i've had three different pulse readings so far !!!!

all different from westfields

[trickytiker]

hi pete

2 magnets on the edge of the rear propshaft join and a cheep

small reed switch of a alarm  about a pound

i had a lot trouble with 4 magnets my speedo is now

spot on

kevin

[geelhoed]

I calculated 5340 and added the 3%

at SVA it was 8% tooo fast but still accepable.

Typre pressures were way up near 3bar though!!!