uklee70
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| posted on 1/4/06 at 02:04 PM |
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HELP Urgent Speedo Magnets
Hi all
I'm having a spot of bother with my speedo
I'm using the original triumph bike clocks
and magnets on the driveshafts
which way do the magnets go if you know what I mean
I spaced them on the drive shaft and let the magnets stick on the metal on there own
but no signal do I have to glue them on with the magnets trying to repel the metal
Is this making sense or am I being a real dumb ass !
Please help
Lee
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emsfactory
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| posted on 1/4/06 at 02:08 PM |
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I take it you mean the polarity of the magnet?
Dont know if it makes a difference.
Wiggle the magnet infront of the sensor and see if you get a reading. If not turn it over and do it again. If you still dont get a reading the magnet
may be too weak or to far away or something else might not be working.
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MkIndy7
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| posted on 1/4/06 at 02:09 PM |
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The magnets go either way up
You have to glue them on to stop them flying off
How do you know how to space them so there the exactly the same as they were on Triumph to give the same reading on the dials?
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uklee70
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| posted on 1/4/06 at 02:10 PM |
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thanks I should have thought of that
I am a dumb ass 
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uklee70
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| posted on 1/4/06 at 03:33 PM |
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No joy back to the drawing board
I'm going to try bigger magnets next
has anyone got any ideas on magnet size
Also has anyone got a different speedo sensor working with there bike clocks
thanks Lee
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MkIndy7
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| posted on 1/4/06 at 04:28 PM |
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Do you know where they were placed on the original bike?
and spaced them at the same diameter on the new set-up?
You could be gettintg far too many or far too few pulses per second to register.
And was the original a continuity pulse (0v contact) to complete the circuit or a voltage pulse?
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uklee70
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| posted on 1/4/06 at 04:55 PM |
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the triumph set up was in the front wheel
we had to cut the sensor out as it was a sealed unit with magnets on a disc
the magnets in the original were in a disc that rotated that had 5 magnets in the disc
the spacing between the magnets is alot bigger now but I was hoping that I would still get a reading and a speedo healer for adjustment
So I think I'm going to had a real problem with this
If you have any suggestions please tell me
would I be able to use an aftermarket magnetic speedo and still use the bike clocks.
thanks Lee
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MkIndy7
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| posted on 1/4/06 at 06:06 PM |
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The Dial knows or calcualtes the speed by knowing how many pulses a sec/min it recieves from the sencor.
So for simplicity 10mph may be 1 pulse per sec and 20 mph 2 pulses per sec
If the magnets are placed in a smaller diameter than the original then it will reieve more pulces per sec as the magnets are in effect close together,
indicating a false speed.
I don't know how speedo healers work i'm afraid to comment on weather that could correct this.
"I spaced them on the drive shaft"
From this I would guess its recieving far too many pulses as the magnests if they were on the wheel would be say 10" from the hub so the magnets
are XXcm apart, whereas if yours is on the driveshaft so they would be XXmm apart.
I think the conclusion is ...
Unless the outside diameter of the bike tyres and car tyres are the same and you place the magnets on the same place on the car wheel then its
unlikely to work without some very complex working out and calculations.
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k33ts
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| posted on 1/4/06 at 07:24 PM |
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i got some magnets out of one of those heavy duty door catches from b&q as there very strong and flat so easy to mount.
i would say you would need them the right way round aswell. cant think of the word but there like polarity concious 
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DIY Si
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| posted on 1/4/06 at 11:22 PM |
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The gauge will be recieving a wierd set of readings as the set up has changed. The diameter makes no difference. 1 rev/min is 1 rev/min regardless of
diameter. However, if the sensor used to be on a wheel, but is now on a prop it will be out by the gearing of the diff, assuming the same wheel/tyre
size as on the bike. ie where is used to be say 1 rev @ 10 mph it now sees 3.4 rev/min@10mph. Or whatever you're diff ratio is. Hope that makes
sense.
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MkIndy7
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| posted on 1/4/06 at 11:56 PM |
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quote:
Originally posted by DIY Si
The gauge will be recieving a wierd set of readings as the set up has changed. The diameter makes no difference. 1 rev/min is 1 rev/min regardless of
diameter.
But surely the time difference inbetween the pulses would be closer if it is nearer the centre?
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uklee70
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| posted on 2/4/06 at 08:20 AM |
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Thanks for the help everyone
I'm not to worried about the correct pulses as I have a speedo healer to adjust that.
But the issue is with the magnets passing the sensor I'm getting no reading at all.
I have ordered some stronger magnets but I'm still wondering which way the magnets should go.
At the moment the stick to the hub (whatever poll that is) or do they have to go the other way
Again I hope this makes sense
Lee
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MkIndy7
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| posted on 2/4/06 at 09:46 AM |
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quote:
Originally posted by uklee70
But the issue is with the magnets passing the sensor I'm getting no reading at all.
I have ordered some stronger magnets but I'm still wondering which way the magnets should go.
Lee
Getting no reading at all could be because the reading is so far out, if your using the dial to check the reading.
I'd forget about the dial and connect a multimeter onto both leads coming from the sencor and test for continuity as the magnets pass the sencor
and at what range it will still pick up the signal.
That'll atleast tell you if its the sencor/magnets or the Dial.
As for which way round they go I'm certain that it doesn't matter
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DIY Si
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| posted on 2/4/06 at 10:27 AM |
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Time difference is always the same, regardless of diameter. The closer to the centre the magnets are, the slower they are going round. So if the speed
is 1 rpm and two magnet's are placed at the edge and the middle of a disc, they both come every 60 secs. One has further to go, but is moving
faster so the timing stays the same. What does change is the amount of time the magnet spends in front of the sensor, since the further out one is
going faster. Make sense?
[Edited on 2/4/06 by DIY Si]
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MkIndy7
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| posted on 2/4/06 at 09:12 PM |
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Yup thats better explained than I was getting at.
We worked it out how many pulses a second the sencor would have to read with the magnets on the driveshafts and it was astronomical.... so we decided
to put them on the diff/prop flange instead where it was a larger diameter and therefore less pulses to deal with per sec, due to the effect of the
diff as well.
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DarrenW
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| posted on 3/4/06 at 09:23 AM |
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I cant comment on your set up but for the DD2 i installed magnet polarity was critical. The supplied magnets had a pip on them. They had to be a
certain way round. I bonded them to diff flange - not the prop itself). Flange was cleaned extremely well, araldite mixed up correctly and dab put on
flange, magnet placed on top and pushed down till in contacted the flange. More araldite placed around the magnet but only the lightest of smears on
top. Second magnet placed as close as possible to 180deg. Sensor position also crtitical - 1mm gap set with feeler gauge. Sensor bracket made very
strong to prevent movement or vibration.
Does this answer question?
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02GF74
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| posted on 3/4/06 at 11:27 AM |
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magnet polarity and orientaiton; this depends on what is inside the sensor.
bike speedo (not motorbike) are cheap and cheerful and contain a reed swtich; basially spring loaded contact. when magnet is brought near, it pull
the contact closed. The magnet can be in N-S or S-N oreitnation.
N=north, s=south. a rectangular magnet will have N at one and and S at other; the flux or the bit that does the pulling will be strongest and the
ends and not the sides, hence oritentaion makes a difference although you will have 2 positions (out of a pissilble 6) when it works the best.
The other type of sensor uses hall effect (I need to read this up to remind me) but the magnet needs to go in 1 way for this to work as the snesor is
polarity sensitive.
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if you are using the original magnets, attach one with say tape to tube that you can rotate, e.g. hand drill and whizz it round next to the sensor;
then repeat until you have triedthe other 5 positions; hopefully one of those will register.
Are you sure the snsoer is woired correctly and not damaged?
[Edited on 3/4/06 by 02GF74]
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