Alpha Simplex derailleur - alignment problems

Re:

The washer provides a second anchoring point for the derailleur.
The washer has a profile that inserts itself in the groove where also the wheel axle slots in. Without it, the derailleur only hinges on the wheel axle, and it's free to rotate.


Although...as I'm writing this, I realize that is enough to place the washer on the inner side of the frame. This was it won't be in the way and it still provides a fastening point. I'll try that.

Re:

Yes, put it on inside of dropout, that's where it's supposed to be. :roll: The "profile" is a locating lug which as you say fits in dropout. From the 2nd of your pics, inside red circle, if you look at the actual hanger itself you will see an indent on it between where it's securing bolt is and washer for axle nut, on it's other side there will be a corresponding lug sticking out. This goes in the dropout slot. With washer on other side both the lugs locate in dropout slot to ensure hanger is in correct place as you tighten the bolt and stop it moving when wheel is out. Once the wheel is in and axle nut tightened it's never moving.
The small bolt that holds the hanger in place is, by itself, not enough to secure the hanger, the wheel securing axle nut does that.
Remember what I said about adjusting the mech limit screws after you put all the parts in correct place as mech will have been moved.

Thanks.
Yes, I will make sure to regulate the screws.

At this point the most difficult thing remains to find the correct wheel alignment. As it is I do it "by eye", which is not the most accurate method.