Single piece crank question
 

I am helping a friend with a loose bottom bracket but I'm only really familiar with three piece cranks. The crank has about 1/16" of play to wiggle around freely. This would be no problem for me with a regualr square taper but I don't know what I'm doing with this. I have attached photos.

I know pictures of the right side of a bike are normally discouraged, but it's applicable here.
http://i107.photobucket.com/albums/m...5/DSCN0539.jpg

And the problem area:
http://i107.photobucket.com/albums/m...5/DSCN0540.jpg

Thanks in advance.

Those are pretty easy to service. All you need is a plumbing wrench (adjustable wrench) or vice grips, and maybe a flathead. Some modern bmxes and children's bikes still come with those. The big ones are called "ashtabula" or American, and there are also smaller ones that are pretty much the same, just smaller.

http://www.parktool.com/repair/printhowto.asp?id=92

Those types of cranks are built basically like wheel hubs - you'll have to tighten the cone against the bearings 'till there's no play without binding, then tighten the lock nut onto that. They're supposed to be easy to work on, once you know what to do, of course.

Same basic principle as a 3 piece. There is a lock nut instead of a lock ring, a keyed washer and an adjustable cone in place of the adjustable cup. Loosen the lock nut, adjust the cone and tighten the lock nut (or remove the left pedal, take everything apart and clean it, lube and reassemble if you are feeling generous).

The lock nut won't budge. Should I just try harder or is it a left handed thread for some reason?

It's been awhile, but I think it is left hand threaded.

Yes, left-hand threaded for Ashtabula cranks.

Neal