I have been dismantling a spare speedo ( not having fixed my original, the needle refusing to come off so far)
With the drag disc assembly and mounting bar removed....so that just the worm gear and magnet remain......... the unit squeeks/squeels on turning. There doesn't however appear to be much lateral play at all when I try pushing the magnet from side to side.
I haven't worked out how to dismantle further and am not sure that I need to. Is there an way to oil the drive shaft end to remove the squeel ??
or do I just ignore the squeel ? and clean and reassemble the other parts ?
having played with it a bit it would appear friction on the drive shaft/spindle is causing the squeel and varies. occasionally it doesn't squeel and sometimes it gets louder. If I hold the unit loosely in the hand with a slow drill carefully turning it, then when the squeel gets louder there is obviously more friction/turning force and the unit will spin in the hand............so the bearing is pretty useless. What is the bearing ?? oiled felt ?? Whatever, doesn't look like I can ignore the squeel.
I can feel a bit end float on the shaft (if held upside down and I push the magnet)
looking down the drive shaft end I can see an inner shaft and a gap to the outer housing. Am wondering if this gap is something to get a little synthetic bicycle chain lube into ?
or is it some other type of bearing and I need to dismantle further ?
(hope I don't look too sad having this conversation with myself !!)
As I now seem to have two functioning non-flickering Smiths SSM speedo's I thought I might as well trap on the thread the apparent solution to this particular problem.
Both speedos had the same issue a squeel and a flickering needle, one sometimes jumping way across the dial. It would appear in both it was the drive shaft spindle being dry and causing friction & vibration. As far as I could see there was no physical contact with the drag disk ( so am mistified about why the needle could jump so radically on the one speedo)
Adding a couple of drops of lube so that it soaks through the gap between the inner and outer of the cable end of the drive shaft did the trick. It carried on squeeling at first, even got worse briefly on one, then stopped and now both seem very smooth and quiet.
I was careful about not adding much as had read elsewhere not to get lube on to the internals as it attracts grime. I also read that synthetic bike lube is a good replacement for watch makers oil...but hadn't seen anything anywhere on oiling this bearing, which it seems is polished steel ( on steel ?/plastic ?). After oiling and turning for 45 seconds with a slow drill ( avoiding any sudden change in speed as I read somewhere this might damage the spring) I stood it face up for a few hours just to make sure the lube didn't enter the internal. The lube I used was a dry synthetic wax oil for bicycle chains, which initially is runnier then dries somewhat.
I had fun taking two speedos out of their cases and taking one apart....but didn't actually need to !
On the one I did take apart I should re-calibrate it. I may have a go. But I may not need to as:
1) before taking the needle off I painted line-up marks on the edge of the drag disk and amplifier plate above it. I used a tooth pick point to get a fine line. It was relatively easy to hold the two in place with the brush end of a small paint brush when replacing the needle to the original position against the stop wire.
2)before unscrewing the calibration screw I painted lines to show the starting orientation of the screw slot, then counted the number of half turns before the thread disengaged. I also took a side on photo to compare with after. So I'm hoping the calibration won't be far away from where it was before ( which was no doubt nowhere near actual speed !)
I took the drag disk,amplifier plate, mounting bar and spring all off in one piece. Great care needed. Don't dangle the drag disc & have something with a hole in it ready to carefully place the disk spindle into.
I've spent 6 months or so scratching my head and asking questions on this one. I might just get the bike back on the road this year !. Hope the above may help someone else.