I’ve got a simplex SGDG derailleur I can’t seem to throw away.
Either me or the previous bike owner buggered the spring tension feature on the spring thru-bolt. -pic below
So now I don’t know how to adjust spring tension on this thing. I gotta think this was/is a common foul up.
Is there an elegant repair that I have not been able to find on Google? Or scheme on my own? I bought an engineering degree a long time ago, and it’s not divining me a solution.

Side bar: this thing bolts on through the inside of the frame- so if you start trying to disassemble with the 5 mm hex on the outside, the anti rotation feature get rounded off.
like Click &Clack the Tappet Brothers said - French engineers never copy anyone. And NOBODY copies the French!!

With only a single spring end hole in both parts of the pivot and no "B" screw type of feature I believe the spring tension was not meant to be adjustable. IIRC this was a near copy of the Shimano Crane top pivot which also had no adjustment designed in. Now one could drill a different spring hole, easier said than done. As to the pivot shaft rounding off one could turn out a replacement on a lathe. A bit beyond my skill level. Andy

It's adjustable to a certain extent by how tight you wind the spring before you lock it in place with the end plate. That's almost a three-hand job, although I have accomplished it by clamping an Allen wrench in a vise, inserting the pivot shaft onto the Allen wrench, and rotating the body until the spring tension is sufficient and the flats on the pivot shaft end line up with where the end plate needs them to be. Then, holding everything in place with your two hands, you reach over with your third hand for the end plate, put it onto the pivot shaft, and lightly tap it lightly in place, taking care not to knock the Allen wrench out of the vise or the bolt off of the Allen wrench.

Yeah, that's going to be a problem. Without the flats on the end of the pivot shaft, there's nothing to retain the spring tension. If there's barely enough flat left to hold it in place long enough to get it mounted on the dropout, the mounting bolt (inserted from the back) may be able to hold things together, but that's an ugly kludge and likely to fail at an inopportune moment. Better to acquire or fabricate a replacement pivot shaft with intact flats. Many of those pieces are interchangeable among the various Simplex models, so a derelict derailleur might supply a decent replacement.

I don't consider a full turn of the spring to be much of an adjustment. I don't remember servicing this Simplex version but have done a few Criteriums way back when. I broke the spring on at least two during the attempts to tension it better. The three real alternatives, Campy NR, Shimano Crane/Titilist and SunTour V series all hade far finer ability to tune the spring tension. Andy

problem solved - i sold the RD with the FD and shifters and two DT clamps.
I'm going to switch the Schwinn over to SunTour drive train parts. Having the Shimano RD and Simplex FD/shifters and Dia Comp brakes & Shimano levers.... all the mismatched parts was always distracting me while I was riding. I didn't think I had OCD.

hopefully I'll forget I have Malliard hubs.... dang it!!

ciao



sunnier days

That’s cheating.

.... yea....i recon so. and now my French hubs will have to get along with the Japanese frameset, Japanese drive train, and Taiwanese brakes. (I think my Sugino crankset is made in Japan...)
but at least the SIMPLEX parts are going to someone who appreciates them!!Arigatōgozaimasu

Pretty photo too. That is the kind of riding I would love. The old barns are disappearing where I am from. I was also under the impression that the frame dropouts weren’t really compatible with the usual Japanese/campy standards.

...this is a pretty good description of the way I have repaired a few of them. What also helps is to orient the thing in the vise so that you can slip another Allen key or some metal shaft of a driver into the slot in the vise jaws after you wind the tension on the spring, to lock against the parallelogram of the derailleur to hold the tension on the spring, while you affix the small anti-rotation washer that has the projecting tab on it.



...it's not elegant, but the best I've come up with is to mix up some epoxy in a small amount, clean the mounting surfaces with acetone, apply a light coating of grease to the flat portion of the derailleur body that rotates around the spring (so the epoxy won't stick to it if there's overflow), and then carefully apply the epoxy with a toothpick to the mating surfaces the rotating spring bolt, and the interior of the anti-rotation washer thingie.

I think the reason they are assembled the way they are in the first place, is that any sort of heat in this spot will take the temper out of the interior spring. Anyway, that's why I never tried to solder or braze this attachment.

Most times you also need to re-bend the tab on the anti-rotation washer back down, and sometimes when you bend it back down it snaps off. Not for the faint of heart, but worth trying for some of the best, later Simples rear derailleur models if you end up with one broken in this way.

Derailleur as received from an e-bay selleff who probably didn't know it was busted

The derailleur with pivot bolt and spring inserted, prior to cleaning with acetone.

Anti-rotation washer, and the interior mounting bolt.

...for clarity, I found these photos that I took to explain why I was requesting a refund on e-bay. I did manage to reattach the anti-rotation washer, using the above methods, but have still not used this derailleur on a bicycle I think it will work out longer term, but you never know. Those washers are not over engineered, in their original attachment design.

I like to think I am reasonably capable with mechanics but I may just take the derailleur to a shop and let them provide the necessary three or four hands. Gad. (In reference to this thread:
67-70 Peugeot PX-10)