vobopl

Preface:
Avoid cr@ppy chains!

I had my first warning when skipping to slow on the downhill coming to the railway crossing in anticipation of the car which overtook me after a long effort braking hard in front of me. My bike throw the chain off the chain ring while the rear cog wound it around itself rotafix method. A wheelie on the front, no fall - I was glad. My second warning was that I had to move the axle way more to the rear than before to get the tension right. Despite knowing that streached chain rides higher on the teeth, I put it back on and I was ready to continue in 5 minutes.

Just nearing my target, I pressed harder to get through the crossing before oncoming traffic - Result? This time the rear cog almost "rotacut" my drive side crank arm as the chain fall to the outside, catching the pedal spindle. Not only had I my rear wheel locked again, but also the cranks stopped in the awkward position. I managed to stay upright this time again, but the chain caught by the cog again acted as the chainsaw on my beautiful, freshly powdercoated rear fork end (first image)

The bike is out of comission until I get new, stronger chain and check for structural damage in the rear fork. I haven't touched my road bike for two months, time to say sorry

The bright side is that my home made fixing adapter survived all the torque. (second image)


Summary:
Avoid cr@ppy chains! And pay attention to the warnings you get.

fixedpip

Sorry to hear that your bike is bruised and scraped.

However, I'm confused why is this the chains fault? Sounds more like a chain tension, chain line or other problem rather than just a crappy chain.

vobopl

I tried to check for issues you mention:
Chain line is perfect - I have the spacers turned on lathe to fit.
I run axle positioners as chain tensioners - setting the right tension is no problem.

I believe the problem is that the chain elongates under hard pressure too much, to the point it is thrown off - with the same gearing I had to move the axle about 5-7mm back in the dropouts over the course of 2 months to maintain the same initail tension. I am looking into chainring not being true as another reason for the problem, but I am sure the chain streach doesn't help.

gally99

i'd be quicker to blame your cog than the chain...
look at how bad those teeth are bent...

vobopl

uniglide cogs come like that - I was trying to find straight tooth, wide base Simano casette cogs around but no luck.

Momentum

Looks like the cog has been carefully designed to throw the chain easily, maybe not ideal for fixed gear riding...

gally99

i blame the cog...

vobopl

I hope less so than the modern Hyperglide cogs . Besides, on both occasions the chain remained on the cog, it was additionally wound on itself while it fell off the chainring.

I hear wht you say, I was uneasy riding this setup last two months. Maybe its a time for a proper wheel besides trying to straighten the chainring (yes, it has some wobble) and getting a new chain.

Thanks,
v.

Aeroplane

Surly, Chris King, and endless bikes all make good replacements for the uniglide cogs that are designed for singlespeed riding (i.e., they REFUSE to throw the chain).