Unwinding crank arms....help!

i seem to have come upon a small, but possibly fatal problem...

the right (non-chainring) crank arm on my single-speed keeps unscrewing itself from the bottom bracket... it started happening a few weeks ago, so i just re-tightened the bolt, and it seemed ok, till it happened again this week, and tightening wouldn't stop it from happening with increasing regularity.

now...i'm not sure if this means that it is simply the bolt that is scuppered, or if it is something even more troublesome....anyone have any ideas?

Firstly, what are we talking about here? Standard square taper BB or some modern hollow type of BB?

Assuming the former, is the crank bolt damaged? Is the BB thread damaged? Is it done up to the correct torque? Have you tried using threadlock?

Your crank arm's taper is probably fucked. The more you are tightening it the worse it will get and you'll get more and more play.

the right (non-chainring) crank arm

Either you're rocking a rare LHD set up, or you can't tell left from right.

Your crank arm's taper is probably fucked. The more you are tightening it the worse it will get and you'll get more and more play.

had the same prob and ^ was the problem. it will get worse over time if ^ is the problem and it might start destroying your taper on the bb in which case you'll end up having to change both bb and arm.

Either you're rocking a rare LHD set up, or you can't tell left from right.

you're right (pun partially intended)....it's been a problem for a long time!

if the crank arm taper is bollocksed, will i be able to tell from just a visual inspection? also, can it been fixed? or will i have to buy new crank arms?

just look at your crank. is the square of the taper still square or has one edge been rounded of?
take a pic of it and post.

if it is fooked, you can find a non drive side crank arm (left :-)) from your LBS. May save you from buying a complete chainset/matching BB