Quote:
Originally Posted by Cory
I don't understand why I keep hearing references to "outside of a tube". What difference does it make? There should be no difference in how well the shaft is supported in either scenario and your shaft deflection is basically nonexistent in both scenarios.
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Quote:
Originally Posted by BrendanB
Its probably stemming from people seeing the walls of the tube acting as an insurance policy in that if the chain does stretch or it wasn't machined right there's a larger tolerance and the tube will keep the chains on the sprockets. Outside the tube, not so much and if the frame isn't that rigid it gets even better. ..
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Yes, that's exactly right. The vast majority of "chain in tube" designs I've seen recently are designed so that the inside opening of the tube is greater than the pitch diameter of the sprocket plus the height of the link as viewed from the side (H in
this image), and (much) less than the sprocket outer diameter plus H plus R, where R is the hub diameter (same image). This means that the chain is free to move when it engages the sprocket, but cannot jump from one tooth to another even when there's no tension on the "back side". Cory referred above to tube larger than this, where the "in-tube" advantage does not apply:
Quote:
Originally Posted by Cory
I still think that will have very, very little effect on whether chain details or not. 233 has done exact center to center for ages in a tube, but a tube that is far larger than the sprocket, so there is nothing constraining the chain top-bottom from coming off.
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While I cannot cite experience, I can see where C-C spacing can work for fairly short runs (where C-C is only ten or twenty full links), but I would absolutely shun C-C without a tensioning option for long runs, like a 6' lift. Maybe someone with more experience in this can better tune my gut "ten or twenty full links" to a more definite number.