Help, broken fixed cog?

I have a bit of problem, and sorry if this a stupid newb question, may the grilling commence:

So new bike last Thursday, on the weekend switched to the fixed side of the hub, monday took of back brake off all fine.
local mechanic checked the wheel was alined and chain tension was ok (as I did it myself)

Yesterday pulling away from some traffic lights it felt like my chain slipped, meaning the crack turned a little but the wheel did not.

so got off check chain all fine so set of again, this happened twice more today and quite scarily once today when i tried to skid on the way home. Then home tried to skid again total loss of grip on the wheel. tried to peddle forwards the chain went around but the wheels did not turn.

Looked back at the fixed cog and noticed a small metal ring hanging loose. The little ring has a few square shaped grooves which seem to be worn down, but the bike is 6 days old???

Sorry if this is really obvious but I don't know whats happend, why and what I can do to stop it happening in the future.

Don't have a camera here, will try with my phone, any suggestions welcome....

quite down i can't ride my bike :(

Lockring not tight enough.
Buy lockring tool and chainwhip, tighten. Done

^Yup, that and the slipping is simply your rear sprocket tightening up as you pedal.

The little metal ring with the square shaped grooves is the lockring.

It came off because it wasn't tight enough.

Put the cog & lockring on with plenty of grease on the threads.

Tighten like fuck with a chainwhip (cog) then with a lockring tool (lockring).

Done.

Thanks, two follow up questions if I may.....

1st So it wasen't that I did not do up the wheel tight enough, (as thats the only bit I put on) the cogs etc were all attached when the bike arrived.

2nd Can i borrow the above mentioned tools from any one?? Or if they are under £10, I might just buy them i guess.

Thanks for the quick answers.

http://www.lfgss.com/tags/slipping.html

Your location would help lenders.

Tool Library http://www.lfgss.com/thread2775-7.html

Your location would help lenders.

Sorry I work 1 min away from Oxford Circus, and currently crash on a floor in SW1V.

Def invest in the tools as well. Keep everything tight that needs to be tight...

@ Hippy thanks for pointing me towards the other threads, will read up a little, sounds like a few other people had the same problem with new bikes.

Not looking forward to my tube ride tomorrow into work.

hey,
if you still have the free wheel on the other side of the hub then you could flip your wheel (put brake back on) and ride to w1. i work on wardour st and would be happy to sort out your wheel, show you how to do it your self next time and tell you which tools you'll need. just let me know.

obviously you could just ride to your LBS as well.

hey,
if you still have the free wheel on the other side of the hub then you could flip your wheel (put brake back on) and ride to w1. i work on wardour st and would be happy to sort out your wheel, show you how to do it your self next time and tell you which tools you'll need. just let me know.

obviously you could just ride to your LBS as well.

I suddenly feel very silly, you are completely right, PM is on its way about offer for help.

www.velosolo.co.uk for cheap lockring tools, you don't need a chainwhip, you can use the "rotafix" method which you should come across on here or google.

be certain that you have not mashed the threads.

Rotafix for the cog, you still need to tightent the lockring. He's not riding the track.

hense the link to cheap lockring tools

...?

Nevermind I probably misread it. Multitasking + cider and tv..