Mercane Widewheel steering stem issue

well after expecting something like this for a while its finally manifested

Now this is something which I became aware of as a possibility something like a year back with the first reports appearing on reddit. Having some basic engineering skills and understanding a bit of how metals bond (or don't) with each other I expected to see this on my scooter one day or another. So I kept an eye out for it.

Below is the first example of this that I saw.. but his had been progressively ignored (because people are stupid) for some time.

Fig 1

the problem stems from what I believe to be a manufacturing design defect in the Mercane and that is based in the problem of "how do you marry a steel steering stem into a cast aluminium suspension / wheel holding system?".

As I see it (I've not yet done a full destructive analysis) the tube that is the steel steering stem is attached into this cast aluminium system.

The steel tube (in my above video) holds the steering bearings and looks like this when pulled out:

 Fig 2

note that the bottom bearing is still attached (as is visible in my video).

Note also that the tube (steering stem) being held appears to be plugged but also bears marks consistent with the broken section in Fig 1 above.

These images are all from the same failed stem. A second failed system was presented to my by some narcissistic fucktard in Melbourne who was trying to get me to help him with a warranty claim (although he'd been smasing into bumps and gutters with reckless abandon.

Fig3

His shows quite well how the steering stem had been deeply embedded into the top bracket (if I may call it that) and shows a steel base remaining. There are marks on that consistent with the shaft (which I'd like to have seen but said moron was unable to bother photographing as I requested).

My current working theory is that the steering stem is plugged at the bottom and has a plate welded onto it that allow the steel tube of the steering stem to be held onto by being welded to the plate. This weld has broken and leaves us with a tube that comes away from the plate as per Fig 3, but the base plate is still embedded in the base of wheel assembly.

So if I'm right then the issue is the failure of the weld and then the eventual (and inevitable) failure of the joint that the tube seats into. Something like this

Fig 4

If this is correct then I can basically repair this by:

• drilling a hole through the steel from below penetrating the plate and the plug at the base of the tube
• if the tube comes out (which I anticipate it will) putting some epoxy in there to help hold it
• putting a bolt through the hole to hold it together

I believe that this may even be a good idea (the bolt) to do preemptively on any Widewheel of this vintage that may as yet not suffered this failure

Today I pulled it down further for a good look, this video covers some of the points covered in the earlier video, but goes further.

While here, steering head bearing dimensions:

• outer race external diameter 37.91mm (don't forget it has a taper)
• stem is inner 27.12mm so inner race must fit that

Now in case anyone thinks this level of war is "BAD" let me say this is an exemplar of what I've done with my scoot for the last year of its life

Now as I said, I regularly inspect because I value my skin and bones, but as you can see I've enjoyed it, and I believe its eminently repairable (and actually still functional right now).

So lets see where this goes, as I'd like to avoid the front falling off

---

PS: I've now done the following

1. drilled in from the bottom of the assembly
2. tapped a thread into that hole 
3. fitted a bolt so that it goes through the thread
4. fitted a nyloc nut onto the top of that bolt so that it can't loosen

Video

Images

and

and looking down the stem...

so that's not coming off any time soon, and so if it gets loose again it will mean that both the weld has broken and the bolt has sheared ... I expect I'll notice before then.

HTH

selling shit to the unwary

eBay is a great place for bargains, but equally you can get shit there too. Happily the buyer protection system works. Case in point, these 10,000 mAh 18650 cells:

there were originally 4, but one has been sacrificed on the altar of science.

I was instantly suspicious about these cells as soon as I opened the pack, they were too light. I popped them on the kitchen scales and they weighed 24g each. A typical 18650 should weigh 45 ~ 50g

A typical 18650 should be expected to deliver somewhere around 2000mAh (even a cheap one) or more. However I'd sort of expected these to be "below par" and perhaps be ok to 1500 or so ... sadly for the seller I have a cell discharge tester and a few tests found that these cells were about 350mAh.

That's right

• good = 3000 (or so)
• average = 2000 (or so)
• these = 320 or about a tenth of good and four times less than I'd expected

That's of course simply shit.

So, why is it so (and indeed how is it so)?

Naturally I decided (after getting a refund) to cut the head off the cell and have a look. I found this:

and almost immediately noted the abundance of empty space in there with very little winding of "electrolyte",  becoming obvious when pulling it out of that cell

I count 9 turns ... which is low (commonly its over 20)

Here's a quick video

so, measuring the area of that electrolyte (as shown in the video) I get about 137cm² which is also very below par with this publication suggesting 846cm² for the area.

As 137 is about 0.16 of the area then that pretty much perfectly reflects in the reduction of capacity because 0.16 x 2000mAh = 323mAh ... or what I measured. Good thing I didn't use these cells for attempting to build a scooter battery.

So this is of course a working practical example of why you went to school and why they taught maths.

old companion revitalised (with a battery)

When I was in school (so yes, around 1979) Seiko released a sort of budget water proof watch called the Sports 100. They weren't hard core bulky divers watches, but were styled divers and were 100 meters water resistant. True Divers watches were (at the time) quite chunky and even Seiko at that time were so expensive that I never thought I could afford one. The Sports 100 was at the time $199 retail, cheaper but still out of my reach. To give that a perspective I paid $800 for my first used car bought about the same time as the release of the Sports 100.

At the time I had a Seiko watch, but it was a LCD screen digital watch, but it wasn't very waterproof (perhaps 50m?), and while it had some nice features you had to press buttons to actually find the date or use the stopwatch, and the buttons were a bit stiff.

So one day I found this watch (looking almost new then, not "weather worn" like it does now) at a pawnbrokers shop at about the time that my Seiko Digital (with a cracked screen) was telling me "time had come" for a new battery. At that time it was already an older watch and I got it for a low price.  The serial number on the watch (7123 - 823A - 940634) suggests its now 40 years old. 

Back then the outside of the rotating bezel was blue and there was a visible red line around part of the edge, barely visible now. But still, what drew me to it then (in particular) was the almost orange colour of the face. I like orange.

That was in about 1982 and since then this watch has been on my wrist, across a number of continents, diving, driving, motorcycling and hiking. I can't say how many times its had the battery changed, but I'd say (on average) every 4 years. Its been in a box since about 2006 (over 12 years) now largely because the battery ran out and as I was by then carrying a mobile phone every day decided that I didn't need a watch. So it sat in the box with a dead battery. Given that its been in a box for the last 12 or so, thats over 26 years on my wrist.

The recent purchase of the Seiko 5 Automatic watch made me think "why don't I pull the old watch down and replace the battery". So I bought a tool ($7) and a battery ($5) off ebay and "had a go". It was as simple as it sounded.

and with the back off the battery just fell out. Basically on this model the battery is held in by the back. The printed circuit is a thing of beauty, thick and untarnished

There was a tiny bit of corrosion on the terminal on the outside of the battery (which I scraped off with a small sharp blade, taking care that nothing fell into the watch), replaced the battery and did it up. There is a small amount of corrosion visible on the steel, but nothing much really. 

If you do this yourself do not attempt to bend that bottom (relative to the picture) battery terminal and DO NOT touch that coil.

I believe its fared better than my fathers Omega Sea Master (automatic) which was pretty much fucked after 20 years (perhaps a little more less, I can't be sure), making the Seiko a true quality bargain.

Its now running fine and I'm quite happy to have an old companion back.

Win Win

A puncture, but no flat tyre: why I like Slime

Some time back I installed Slime into my MX60 because - pneumatic tyres and my knowledge of what that brings. Of course it brings some amount of bump compliance, but it also brings the possibility of punctures (you know, popped rubber balloons).

Inevitably I noticed this ...

yep, a puncture to my tubless tyre (because while tubes are a whole different ball game all balloons can be popped.

which is where Slime comes in, it remains "sealed" in the tyre as a goop and when there is a puncture it oozes out carrying its little particles with it, to block the gap, which is exactly what they did.

Clearly this is a large cut and exceeds the claimed capacity to block holes, yet block it it did.

I observed the "ooze" of liquid and wondered what it was, did I run over some snot or something?

Nope, it was just it "doing its thing" letting the water out,but the particles becoming trapped. Pressure was still good 30PSI.

I observed that something was still in there, puffing the rubber out. So wondering if I'd run over some glass or something I decided to look carefully and indeed I could see something still in there. I decided to dig it out. Surprisingly this is what I found:

a small but sharp shard of "blue metal" rock that's commonly used in road surfacing. Clearly it had flung up and striking the rear tyre at exactly the right angle, had penetrated and been pushed in.

This whole episode highlights why on a scooter I didn't want pneumatic tyres, but if you're going to have them, then use slime.

---

PS

Well I went for a ride this morning and when I put the scooter out in the sun to give it a recharge (its still a bit cold for optimal charging here) I found that there was slime all over the rear guard

you can still see that the hole is wet ... so I'm assuming that its centrifugal force pushing this out, as the tyre is still at 30PSI (where I inflated it to yesterday afternoon and before I went on a ride.

But its still clearly leaking out, so I'll have to see about taking the tyre off and see what if anything I can do from the inside.

So this means that while slime hasn't meant I don't need a new tyre it means I can keep on using it till one arrives (or I try to repair it).

POST Script

having now done the change I put together this small set of videos

and an analysis

puncture is actually just under the shadow of my fingertip ...