Originally Posted by
Lucero
Thanks all, by tensioning, I mean, I looked for a b adjustment, but there wasn't one, and I suspected the top pivot bolt would be a route to take.
I've subsequently ordered a 610 NOS , just in case I have borked something. How can I get the spring break to where it's meant to be?
Is your 810 mounted to a claw or directly to a Simplex dropout?
The B adjustment (on derailleurs with B screws) changes the angle of the derailleur body, which can increase tension on the chain. The Simplex 810 and others don't have a B screw but they do have sprung upper pivots as well as lower pivots. There is no adjustment for the angle of the body.
The upper pivot bolt must not be rotated when being removed from a claw or dropout. The hex socket is used to hold the bolt steady while the nut is loosened from the back side of the derailleur.
If the pivot bolt is rotated, the spring can break or in the case of a dropout mounted unit, the other end of the bolt becomes rounded and tension at the upper pivot is lost. If the spring is broken, you might be able to scrounge one from a donor with a claw (do you have a bike coop nearby?)
Here are some exploded views of the 810 that show the upper pivot bolt and spring.
This shows the T or touring cage
The GT cage
Secret decoder chart
What these illustrations don't show is where the inner end of the spring lands. I don't know if this is always the case, but this claw mount has a hole for the inner end of the spring. There is only one hole and I doubt that you could tighten the spring a full turn to increase tension. I suppose you could drill another hole for the spring end to increase tension, perhaps as much as 90° from the original hole.
Units that mount to the Simplex hanger are different. The inner end of the spring is held by a hole drilled in the body of the upper knuckle.
Dropout mount with upper pivot bolt that hasn't been mangled. No spring hole in the washer.
Under the washer of a dropout mount unit, Delrin body.
An SX630. Beneath the washer you can see there are two holes in the body for the inner end of the spring.
It may be possible to increase chain tension by adjusting the locknut that fixes the angle of the cage at the lower pivot.
If your upper pivot bolt has been stripped, there is a fix that I posted recently here:
ISO and for trade thread part 5