Tern Vektron S10 gen3

[Sav]

Have not posted for a while.

Upgraded one of my Kalkhoffs to an S10 Tern a year ago and the little bike has been brilliant, much more oomph than the kalkhoff. I did it because of the increasing difficulty in taking a full size bike on the train down here.

All was well until Thursday evening after dark when the Tern launched me into a swan dive going along a country lane without warning. It was not a black-out as it certainly hurt when I hit the deck on my front, fortunately not on my new hip!

To my untrained eye it would appear the handlebar collapsed, gaving way! The stub end picture in correct orientation attached can be seen to have sheared from the top with the hanging hinge on the bottom. If the accident had caused the break the 'hinge' which would have been the final thing to give way would not have been at the bottom. I would not have expected a simple tumble to break the handlebar anyway. The wall of the (ally??) tube is only 1.6mm, pretty thin.

Me? I'm in a lot of pain with gravel rash and I suspect a bunch of cracked ribs as I can hardly move, not good at any age leave alone 75!

Have emailed the retailers awaiting a reply and will email Tern as the bar looks mighty thin walled!

Anyone agree or disagree with my theory?

 

[Croxden]

Gosh, I feel your pain. It hurts a lot more in old age. Now I worry as I have a Vektron, not that I use it much. Keep us informed on how you go on with it.

 

[Sav]

Most helpful reply received immediately from the UK arm of Tern. Still waiting to hear from the 'sales' address at Fudges the retailers after 24 hours.

 

[matthewslack]

Post some more pictures if you can.

Of both broken ends, and also side on showing the length of the bars and what is mounted where.

It looks like a difference in colour on the right hand side in the pic, bright and shiny from 4 o'clock down, and duller upwards. That suggests a developing crack around the circumference which lead to final failure when remaining material could not withstand load. Probably on a bump.

Initiation of crack could be a surface defect, possibly from the clamping of some bar mounted thing.

 

[Sav]

Will do thanks, as soon as I can get down to the workshop.

 

[guerney]

That all sounds and looks very nasty. Hope you get well and back on your bike soon. Why do Tern have so many metalwork problems?

 

[Nealh]

That all sounds and looks very nasty. Hope you get well and back on your bike soon. Why do Tern have so many metalwork problems?

It's called karma for nicking the original intellectual rights from David Hon.

 

[Sav]

Nothing additional on the bars and nothing in the area of the break.

Now heard from Fudge's as well as Tern UK, will try and enlist some help to take pictures tomorrow afternoon.

Chris

 

[matthewslack]

Nothing additional on the bars and nothing in the area of the break.

Now heard from Fudge's as well as Tern UK, will try and enlist some help to take pictures tomorrow afternoon.

Chris

The full story of the fracture is in those surfaces, just needs interpreting by someone with the expert knowledge.

Is the break right by the stem clamp?

 

[guerney]

It's called karma for nicking the original intellectual rights from David Hon.

Clearly, they didn't nick enough - I bet they regret saying "Steal design secrets from David Hon, and make it snappy!"

 

[guerney]

Anyone agree or disagree with my theory?

It's hard to tell what may or may not have happened from that photo.

Hardly bargain basement, must be very annoying:

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Tern Vektron S10 2023 - Electric Folding Bike. Out of Stock. All Electric bikes are delivered free to the UK mainland, 365 day returns & Price Match.

www.tredz.co.uk

 

[Sav]

Things seem to be moving OK with both Tern and Fudges Cycles involved, bike is to be collected, these things happen, I just hope its a one-off failure.

Took some more photos, this one from the other side of the break, appears to me to have very little clean metal apart from where, I guess, it hit the road.

 

[guerney]

Could you upload more photos?

 

[matthewslack]

Things seem to be moving OK with both Tern and Fudges Cycles involved, bike is to be collected, these things happen, I just hope its a one-off failure.

Took some more photos, this one from the other side of the break, appears to me to have very little clean metal apart from where, I guess, it hit the road.

If the metal is not clean, there was probably a crack for quite a while before the break.

 

[Sav]

There's not much else to see,

Attached shows the break which looks like it was bent downwards. What else did you want please?

 

[matthewslack]

There's not much else to see,

Attached shows the break which looks like it was bent downwards. What else did you want please?

That's a really good picture.

The matt grainy texture in the upper part indicates 'overstress fracture', and the bending at both top and bottom shows that during your crash, at first it could stand the force applied, so it bent, until the stress at the outside of the bend exceeded the strength of the material. Then it snapped. It doesn't look like a material defect.

The crash produced a force it was not strong enough to withstand. The geometry of the crash will have had some influence on that. It probably hit the ground end on and stopped with the full load on the bar.

I'd consider you fortunate to not land on the opposite end, which can cause some very nasty injuries.

 

[guerney]

Looking at your most recent photo, of whatever part of the handlebar that is (handpost to the right of the image?) - I'm wondering if the bar is the same thickness all along it's length? If so, that would be a foolish design decision by Tern - if that's a photo of near the middle region of the bar, with the break to the left of the middle of the handlebar. My Dahon handlebar thickens near that break point. Tern should have used a thicker walled tube, more appropriate material, or a better shape. I've had at least two bad recent collisions so far, and the (Dahon built in April 2006) handlebar's fine. Tern's designs have taken a tern for the worst. At your age, broken bones can be very problematic.

This isn't my handlebar, but it's the same shape

 

[Sav]

Colection being arranged

 

[matthewslack]

Colection being arranged

If they replace your bike no fuss then at least the 'after' service is pretty good!

I hope you get a good outcome, and your ribs go back together OK.

 

[Sav]

Thanks,

Yes I am wondering what they will do with the bike. As mentioned there is surprisigly little damage to the paint work, but marks there are and they will need to be dealt with.

I am just hoping there is no quibble over the cause, it looks clear enough to me, but obviously has me worried from more than one angle.

Starting to be able to move a little easier but sleeping is still difficult and coughing is still agony.

In the doctors surgery tomorrow for flu jab, will ask about stronger pain killers.