DiegoFrogs

I admit that it is significantly difficult to calculate an estimate for the instantaneous input torque, but the relationship between the force required to create the input torque and the equivalent force required to do the same on an appropriately long chainwhip makes the decision a no-brainer. I'll possibly examine the mechanics at work in the rotafixa method and derive certain relationships with generalized variables. I've actually already done that for the other generalized case, but it was months ago and I had no intention of sharing that work, so it wasn't in a ready to be published form.

Also, I'm sort of busy at work... and didn't want to go through the entirety of my work again, but I wanted to show that the OP really should find some other method of fastening the cog to the hub, for his/her own safety.

I just thought the insinuation that the OP should just torque up a steep hill and that would generate significant moment on the cog so as to not allow the opposite motion to happen on the corresponding downhill was totally without merit. I therefore actually did some work to show that the poster was wrong.

baxtefer

the rotafixa method provides the same torque as the same force applied to a ~330 mm (12") chainwhip.
That is, Whithout the associated potential for knuckle-busting slippage.
Think about it, you're just using the wheel's radius as your lever arm.

bostontrevor

It will give you a little more torque unless you're working with a 24" wheel. On top of that, I find it easier to work with and can more readily deliver full force with both arms or possibly even my legs (in practice that's not really necessary).

r0cket-

Your hub is probably not stripped. If it were, the cog would spin freely, not move forward and back a little. What it sounds like is that your cog is narrow enough that your lockring isn't making contact w/ it, so you need a spacer between the cog and hub to push the cog outward (in the direction of the lockring).

Aeroplane

um, yeah... pretentious American accent. I thought Rotafixa was some Americanized marketing style word that Ron Popeil hocks. You know...

"These new Rotafixa cranks are recommended to sell for $160. But I'm selling them for not 140, not 120, but $100, AND I'm giving you a free vegetable slicer! Now, can you beat that folks?"

gmcaptain

I just whipped out my whip...

Study that whip and tell me that the distance between your center of rotation is 12 inches. Obviously yours could be larger than mine (not bloody likely), but of that 12 incher I'm looking at, the effective length, that is the distance between that center of rotation and the point at which your loading is centered, is considerably less than a foot. I'm looking at approximately 8 inches.

The point that I think you are missing is that if a person chooses to go this route (I agree that it should be done properly with a whip) they shouldn't be able to back that cog out. Think about this. If you do as the initial poster advised and put great bit of force on those cranks (either up hill or accelerating) then secure the lockring, there's no reason for the thing to slip causing strippage. Theoretically you have tightened it at your personal maximum, and nothing YOU can do will back that sucker off. If your 200 pound buddy wants to ride it just tell him no.

I commend you on your calculations and persistance on this matter. I am surprised that my initial guess of 50+ pounds was quite high. Excellent work. You have definitely proven that you know your sh*t and I regret and retract that former statement. Appologies for assuming there are rampant misinformed know-it-alls.