i overhauled a simplex rd recently and am having trouble understanding how to mount it in the on-frame derailleur hanger. i'd like to use the top portion of this diagram as an example of the issue:



the derailleur is not exactly like that pictured, but does have these similar parts:

- hanger bolt (3876). mine has a tiny hole for the spring. the bolt is hollow and threaded inside to fit the screw described below.
- spring (3885). mine installs in the front of the body, before the bolt, and is secured to both bolt and derailleur body.
- bracket (3563L). mine is teardrop shaped, has no tiny hole for the spring, has a square hole for the bolt, and has two notch-like-things (not merely one as shown), one bigger than the other, and they project on either side of the bracket (so one hugs the derailleur and one fits against the frame).
- screw (2551A). the bolt (3876) does not screw into the frame, so this screw is used to fit inside the hollow bolt to secure the derailleur.

questions:
- how do i load (tension) the spring? or do you pre-load the spring at all?
- which side of my bracket faces the frame?
- if you think you might have a similar derailleur to the one i described, could you post a pic or provide some info?
- is it wholly necessary for the spring to be engaged for the derailleur to work adequately?

many thanks.

this bad pic shows how i have the bracket currently.

Can't be of much help but it might help to post pics of your derailleur's back side. They had so many variants.

Your bracket does face the hanger like in the diagram. Tab on bracket acts as the stop against the outside diameter of the derailleur hanger.

Did you have it apart? It looks like the tabs are somehow reversed. The larger tab points outward on mine. It is the derailer stop. The smaller one goes where your larger one is. There's a lot of variation on those, though.

You use an allen wrench on the pivot bolt to preload the spring and to put the tab in the correct position for mounting. you don't need to turn it far. Hold it until you get the bolt tightened from the back side.

That's not the hanger bolt; that the upper pivot tension pre-load bolt. The hanger bolt is #2551A , and it installs from the back side of the hanger.

You only need to reset the pre-load if the backing plate #3563L was removed allowing the pre-load to be released. In that case you insert an allen wrench into the pre-load adjustment bolt #3876, twist it to apply pre-load, and install the backing plate #3563L to hold the pre-load.


Yes.

yes, i completely overhauled it, but it didn't look like it was mounted correctly to begin. the previous owner said there was "something" wrong with it. i always assume i can repair these things, sometimes to my detriment.

thanks for the info. so you're saying the wider bracket tab (currently facing toward the frame and acting as the stop) should be facing outward (doing nothing), and the smaller tab should fit between frame and derailleur, acting as the 'stop'? that would allow a little more travel.

thanks for the correcton on the terms. i was mistakenly calling the tension bolt the hanger bolt, and the hanger bolt the screw. i have their orientation installed properly, but not tensioned with the spring properly.

i assumed this was the case, and tried several times to do what you describe without success. the back of the tension bolt does not fit well inside its bracket hole, and i'm unsure where to orient the bracket when i begin the spring tension.

good point. i've been lazy with pics as my phone's camera sucks, and i've found it a hassle of late to pull out the big slr. but here's another bad phone pic of the backside.



the tension bolt end looks more round and the bracket hole looks more square. if this poses some of the problem, maybe i can refab the bolt end with vise grips or something to prevent it from moving within the bracket.

That's what I'm saying.

There have been a few threads like this. You're not the first to have trouble with these. I've screwed them up myself. I deleted the picture of my SLJ I had posted above because I noticed that the inner cage half was upside down.

Now that you've posted a picture, I think it's obvious how that part goes on. The small tsb goes toward the wheel. Could you have the spring mounted upside down? The end shouldn't stick out that far.

This is a different model derailleur than yours, but it should show how the backing plate is mounted to hold the upper pivot spring pre-load:

i wish!

if i mount the spring in reverse, the shorter end of the spring pops out of the body when under load (tensioned). so, i think i'm good with at least that part.

John's picture above shows that all you need to do is turn the pivot bolt until the tab is positioned at the front of the hanger and install it. Hold it in position while you screw in the bolt from the back. That's all there is to it. Turning the bolt to the correct position sets the preload.

[QUOTE=eschlwc;16089983]

if i mount the spring in reverse, the shorter end of the spring pops out of the body when under load (tensioned). so, i think i'm good with at least that part.[/QUOTE

Maybe you are trying to put too much tension on that spring because you still have it assembled wrong. It should be less than half a turn.

a half turn will pull the spring out of the body if mounted in the opposite way. so i'm sure the spring's orientation is not a contributing factor to my foolishness. however, your note of 'half-turn' does help.

john's pic confuses me because our brackets are different. if you look at my pic in post 8, i assume the following:

- the large tab of the bracket hugs the derailleur body, facing outward.
- the small tab of the bracket faces the bike frame.
- the pointy part of the bracket's teardrop (opposite the tabs) is closest to the cable entry.

true?

easier said than done. like i briefly mentioned before, there may be an issue with the way the tension bolt and bracket fit together, but i'll keep trying. your guidance is helping tremendously.

i think i figured it out (with your help):
- half turn pre-load, held while tightening the back bolt.
- teardrop point of bracket facing rearwards.
- tighten the hell out if it to keep the tension bolt in place. if the tension bolt loosens, the spring won't work (at least with my possibly mangled tension bolt).

i'm still not sure my tension bolt fits neatly in the bracket hole, 'cause the bolt can move all around within the bracket hole. the flats of the hole don't hold the tention bolt in place. but if it's super tight to the frame, the spring should work.

on a related note, why do the best vintage derailleurs i've used, suntour cyclone and campy nr, go without this anchor spring and continue to work so well? it seems an unnecessarily engineered extra.

anyhoo ... thanks for all the help! i'm a lot happier now.

It's simply a different design. Campy used a very similar top sprung design on the 1st generation Rally.