Singlespeed & Fixed Gear - Derailed! (unchained?)

So i was out on my usual 15mi mashfest with my still new Steamroller, coming across a bridge, hauling typical ass, musta hit a bump or something because to my surprise my chain derailed. Luckily I wasn't bucked or anything (how common is that?) Anyway I guess my tension was a little too loose, I hadn't checked it in a few days. Is it normal for them to loosen over time or do I just have to crank down my nuts harder? I had my wrench with me but decided to just ride the few miles home gently as it was. I decided to take a pic of the tension:
http://i50.tinypic.com/29n6yyx.jpg

It's a little loose but I wouldn't have thought it would derail. So anyway, fyi. I've seen some pretty loose recommendations for chain tension around here, but I'm gonna start erring on the tight side. Basically like Sheldon Brown said (http://sheldonbrown.com/fixed.html#tension):

"make the chain as nearly tight as possible without binding. Notice how freely the drive train turns when the chain is too loose. That is how freely it should turn when you are done, but with as little chain droop as possible."

I never set upa chain so loosly that it is visibly saggy. The chain should be taut enough to look dead straight but you should be able to push it and have it give an inch or so easily. Hope that makes sense, I had a hard tim e learning what right tension is and its the best I can explain it.

That chain is retardedly loose.

Correct chain tension, is maximum tension without the drivetrain binding at any one spot (should spin as freely as if the chain was super loose). This minimizes the chance of chain drop and gives the best feel. Almost every drivetrain will have a tight/loose spot.

Heheheheh... nuts...

Uhm, yeah you should crank down on the track nuts hard enough that they don's slip. Given time you'll eventually get to know what this feels like. You might also consider picking up a chain tensioner wherever fine bicycles are sold.

That chain is retardedly loose.

Correct chain tension, is maximum tension without the drivetrain binding at any one spot (should spin as freely as if the chain was super loose). This minimizes the chance of chain drop and gives the best feel. Almost every drivetrain will have a tight/loose spot.

Yep, I know it's too loose, it fell off for crissakes. And for the proper tension you just rephrased what I quoted of Sheldon Brown in the last bit. This post was mainly an fyi to others, and I was wondering is it normal for the chain to loosen a little after only 100 miles or am I not torquing the nuts enough?

Uhm, yeah you should crank down on the track nuts hard enough that they don's slip. Given time you'll eventually get to know what this feels like. You might also consider picking up a chain tensioner wherever fine bicycles are sold.

Hmmk, I'll get em tighter, but I thought I had em pretty tight. It may be I was just sloppy/lazy with the tension last time. I just never thought it would come off like that.

Hmmk, I'll get em tighter, but I thought I had em pretty tight. It may be I was just sloppy/lazy with the tension last time. I just never thought it would come off like that.
That chain is waaaay too loose!
Watch:
http://www.youtube.com/watch?v=q0V1opTpxuc =easiest way to tighten chain
Maybe you didn't tighten your bolts enough before you went out to ride that time.
Also see: http://www.sheldonbrown.com/fixed.html#tension

Yep, I know it's too loose, it fell off for crissakes. And for the proper tension you just rephrased what I quoted of Sheldon Brown in the last bit. This post was mainly an fyi to others, and I was wondering is it normal for the chain to loosen a little after only 100 miles or am I not torquing the nuts enough?

If you centered the wheel on initial installation the wheel will be pointed to the left when viewed from the rear - this indicates that the drive nut is slipping under load. Undertorque, or crappy track nuts and a bunch of other things will cause this. Chain stretch will cause a little bit of tension loss when riding but it shouldn't be very noticeable over 100 miles. Do not overtorque track nuts, if they are slipping with the correct torque you should find out why.

That chain is waaaay too loose!
Watch:
http://www.youtube.com/watch?v=q0V1opTpxuc =easiest way to tighten chain
Maybe you didn't tighten your bolts enough before you went out to ride that time.
Also see: http://www.sheldonbrown.com/fixed.html#tension

Yes I now know it was too loose lol. It fell off. Thanks for the vid, I've seen it, I do know how to tension my chain. Just didn't have it tight enough this time. I think I tried erring on the loose side because I've read a lot of people around here say there should be a slight visible droop,and I've seen people downplay the possibility of the chain coming off (or maybe I was just lazy last time ("good enough!"), or maybe it slipped a little). I linked the same link to Sheldon Brown in the OP, I'd used that method before but I'm gonna be tensioning tighter consistently again from now on, obviously. Thanks for the advice though everyone lol.

operative word is slight. Mine has a very very slight droop that you can only notice if you really stare at it.

after about a month of riding fixed i dropped my chain going down a steep hill, in traffic, and it wrapped around my rear cog locking up the rear wheel. skidded through a tire and it was a miracle i was able to not fall with how unstable **** had become. thankfully i had a brake.

needless to say, i've made sure not to ride with a loose chain since.

operative word is slight. Mine has a very very slight droop that you can only notice if you really stare at it.

I imagine it varies from bike to bike. ie some have a more out-of-round rotation than others. Which is why I think going by sight, or recommending any droop, is a bad idea. As always Sheldon had it best: about as tight as can be with no binding, and long spins. Another tensioning protip I've picked up: once a person knows the tightest spot in their rotation, they should set the crankarms to that spot every time, then go by feel plucking the chain, for consistency/speed in tensioning.

after about a month of riding fixed i dropped my chain going down a steep hill, in traffic, and it wrapped around my rear cog locking up the rear wheel. skidded through a tire and it was a miracle i was able to not fall with how unstable **** had become. thankfully i had a rear brake.

needless to say, i've made sure not to ride with a loose chain since.

Wow yeah. I've been riding fixed about a month myself, which is why I made this cautionary post for noobs out there, so they don't make the same mistake. Dropping chains is possible! And yes definitely another reason to have a brake!

Step 1- Get a racquetball.

Step 2- Loosen rear axle nuts.

Step 3- Shove racquetball between rear tire and seat tube.

Step 4- Tighten rear axle nuts.

Step 5- Remove racquetball.

Step 6- Profit!

I imagine it varies from bike to bike. ie some have a more out-of-round rotation than others. Which is why I think going by sight, or recommending any droop, is a bad idea. As always Sheldon had it best: about as tight as can be with no binding, and long spins. Another tensioning protip I've picked up: once a person knows the tightest spot in their rotation, they should set the crankarms to that spot every time, then go by feel plucking the chain, for consistency/speed in tensioning.

It's also not a bad idea to turn the chainring on the spider so that the tight spot is where the cranks are horizontal, so you don't have any play while trackstanding.

Its very hard for me to get just the right amount of slack in the tension, because as I crank the nuts it rolls my wheel backwards making the chain tighter, so frustrating

Step 1- Get a racquetball.

Step 2- Loosen rear axle nuts.

Step 3- Shove racquetball between rear tire and seat tube.

Step 4- Tighten rear axle nuts.

Step 5- Remove racquetball.

Step 6- Profit!

Haha, I'm going to try this.

Its very hard for me to get just the right amount of slack in the tension, because as I crank the nuts it rolls my wheel backwards making the chain tighter, so frustrating

Just make it so that your wrench is puling up or down when tightening.

Its very hard for me to get just the right amount of slack in the tension, because as I crank the nuts it rolls my wheel backwards making the chain tighter, so frustrating
Are you using track nuts with captive washers or generic nuts with separate washers? Track nuts will let you tighten up without making the axle move.