Double check that everything is on the correct side. Cranks and pedals will be marked in some way with R and L. Slit in frame goes to the back (Or badge goes to front if you have Unicycle.come badge). If you already know this, no offense meant but it’s still always a good place to start.
There should be a lock nut over the bearing race on the pedals. My guess is that you are not getting that tightened up enough against the bearing race. Or worse you don’t have the lock nut at all.
Cranks should only need a little bit of tightening from time to time. If you are not sure how tight they should be your LBS should be able to help you. (they shouldn’t charge for a little favor like this. If they do find different bike shop)
I check my ISIS cranks every month or so and it usually takes a little turn (like 1/2") but that is not weekly thats more like bi-monthly but I’m pretty easy on my unis.
If you have access to a torque wrench I’ve read that 30 ft/lbs is the correct spec for tightening ISIS cranks, and also saw someone on this site say 50 ft/lbs so they won’t come loose again, but my instinct from working with fastners tell me that’s too tight. Though I did tigthen my cranks down to that once with no ill effects. Now I just use an 8" hex wrench and call it good. No problem with them coming loose at all.
It’s normal for them to come loose a little when a Uni is new, but after a few tigtenings they should hold pretty well without coming loose.
the way that i tighten things is that i get it as tight as i can possibly get it. For example when i let the bike shop true my wheel and they put my uni back together it will fall apart in 10 minutes because they think that its bad to tighten things up.
SOOO just get it as tight as you can, oh yeah its normal for your cranks to come loose. i re-tighten mine every month or so
You should have a dust cap, followed by a locknut, toothed washer, adjustable cone, loose ball bearings, and a cup. The adjustable cone tightens against the ball bearings to remove play in the pedal, the toothed washer prevents the adjustable cone from turning when you tighten the locknut, and the locknut keeps it all together. You may be missing the washer, if so you should get another from your bike shop. You will find that when you tighten the locknut the entire pedal will get too tight, so you have to allow for that when you set the cone. I usually start with it snug, and then back it off about a quarter turn, then try it with the locknut. I can’t remember the sizes for sure, but if I recall correctly the locknut in most pedals is 11mm, and the cone is 12 or 13mm. I use a nut driver to adjust my pedals, and I never have them come loose. That being said, I wouldn’t recommend loctite in a pedal. The chance of it getting into the bearings and really fouling things up is too great. If it is assembled correctly, and you aren’t missing parts you shouldn’t have to muscle it, or use loctite to get it to stay put.
If in doubt go to a bike shop and ask them to adjust your pedal. It should only cost a few dollars, and you shouldn’t have to worry about it again.
You can find cheap ones at automotive stores. I like the cheap needle torque wrenches or the very expensive ratchet ones. My impression is that the cheap ratchet ones are inaccurate.
I use it to tighten the screw securing the cranks. I find 30 ft-lb works well. I have not had to retighten them. I apply a tiny bit of grease to the joint before assembling them, and work up to the final tension slowly to let the parts mesh.