Ammeter pointer damping

[a101960]

Has anyone here ever adjusted the ammeter pointer damper? I am about to do mine I assume that the screw is turned clockwise. I seem to remember reading once that about 5 degrees is about right.
John

[Gerry]

Hi John, I might be wrong but on mine that screw adjusts the vertical play for the needle spindle, too tight and the needle won't move, too loose and the spindle falls out of the dimple!! Cheers. Gerry

[duTch]

 I either had to start a new thread, or find a relevant existing one to hijack....this won 

 I had though that this screw was for centering the needle and maybe had a soapbox session about it a while ago, but what Gerry says is exactly what I discovered.....
 
 It all started yesterday arvo when I made a snap decision to change to -ve earth, just enough daylight to do it (oh yeah), that was until I dropped one of the terminal grub screws, which hit the mudguard and...? ? so after a half hour -getting dark- phone torch would've been good if I'd looked in the right place, no find, so started this morning carefully snipping the grass with scissors (planning the job is a great idea), but gave up and got out the vacuum.....yep might've looked a bit weird vacuuming the lawn- but found it...you guessed it, last place I looked...!!!

 Then I realised the terminal block is a bit loose in the body, so figured to fix it...no go/ no need, but also noticed the coil close to the body, so fixed that with a nudge, figuring it could be a future short circuit (see photo)... then tried to 'centre the needle'...until I discovered that what Gerry said

that screw adjusts the vertical play for the needle spindle, too tight and the needle won't move, too loose and the spindle falls out of the dimple!!

, is how it is,and it's a bitch t get back in place...

  So now I have -ve earth, and a newly adjusted needle pivot and the only way I could find to adjust the needle centre is to 'manipulate' the shape of the needle...which gets out of shape anyway, when taking the face off...thing I noticed, is after I had the needle nicely centred, when I put it in the hole it went out of whack, took a while to figure that something magnetic was affecting it..

 Hopefully tomorrow road test will show all good (I'd go tonight, but don't need to and best play it safe)   

 

 

 

[a101960]

Well, curiouser, and curiouser! I got my information about ammeter damping from Shaun Hawker the BSA electrics guru. What he told me was that the screw bared on the pointer pivot and acted as a friction damper. If the screw is over tightened it will indeed cause the pointer to move from the vertical position due to the screw exerting to much pressure on the pivot point, thus as you turn the screw it will grip and clamp the pointer causing the pointer to move. Conversely if the screw is to loose then the pointer will part from the pivot.  All I can say is that I gave the screw a slight tweak and the pointer no longer swings about like a deranged metronome. The pointer action is smooth and reliable. What Gerry said is correct, but a secondary function of adjusting the screw is that it will facilitate a degree of friction damping. When adjusting the screw a degree of sensitivity is required. It worked for me anyway!
John

[duTch]

 Yep, that's about what I discovered- though not sure what you mean in earlier post about 5˚...?

[Greybeard]

I seem to recall someone discussing damping the needle by filling the ammeter case with oil. Not sure how you'd seal it though.

These ammeters are very cheap and nasty though; hardly a lab instrument.

As discussed a while ago I fitted a neat little multi coloured LED device that I've arranged to shine into the edge of the ammeter (only when the lights are on, to avoid draining the battery when I'm not riding; otherwise would need a switch). That gizzmo shows green for a positive value; amber for no current and red for discharge. I'll go and see if I can find a link to that discussion.

Later: http://goo.gl/9lp5OI

[a101960]

Yep, that's about what I discovered- though not sure what you mean in earlier post about 5˚...?

Dutch what I meant by that was that the screw should be turned by about 5° from the starting position to effect the adjustment. That is to say when you engage the screw driver in the screw slot, rotate the screw driver and turn the screw about 5° clockwise.
John

[duTch]

 

should be turned by about 5° from the starting position to effect the adjustment

Ok, kinda figured maybe that ...but it would be different for any situation I guess...

 GB, I remember that saga, was thinking of it the other day- so I presume it's still working fine, and would be a nice indicator for people like me who forget to turn the light off...just a matter of finding somewhere to stash it.

[Greybeard]

just a matter of finding somewhere to stash it.

The unit is tiny. Basically a normal LED in a holder that has the circuitry.

[duTch]

 Thanks GB, I came across that thread about oil in the meter while doing a search- try " amps Guage", or " Ammeter" I'll have a look when I get back to camp

 Found it; last post is from TT

I've heard of people filling the ammeter with oil.

http://www.a7a10.net/forum/index.php?topic=6611.msg45824#msg45824