Aubergine 

dddd

There are a couple of issues with re-adjusting the pivots on these derailers!

Firstly, it's a challenge to find the right wrench for all of the nuts and bolt heads. What works on one will have clearance issues on another, and you have to be able to get all of them adjusted properly. Very common for one pivot to cause the derailer to fail to retract fully toward the dropout, and it's difficult to identify which one it is!

I had to do a sequence of tests by first loosening all pivots slightly, then setting cable tension to JUST allow shifting to the smallest cog.
Then, I secured each pivot's adjustment, testing each adjustment independently to verify it was as tight as it could be without causing any resistance to retracting to the smallest-cog position.

If the locknuts are torqued properly using practiced workshop skills, then no threadlocker products are needed to keep the nuts tight. These derailers were state-of-the-art in the late 50's and 60's, and were successfully raced in many professional racing events and championships, so are a reliable piece of gear if kept in a proper state of lubrication and adjustment.
They can be challenged by modern chain's flexibility, since most vintage derailers feature abundant "chain gap" near the smaller cogs, but unless one pushes for use of a 6-speed freewheel (with modifications as shown below), they should handle 5s freewheels with ease if the freewheel is positioned within a proper distance range from the dropout.

The return spring on these is fairly stiff, so keeping the cables and shift lever pivot working smoothly (lined cable housing, appropriate ferrules, oiled lever pivot) should make for quite-decent shifting performance.

Mr. 66

USAZorro

I find they are quite functional doorstops, but just a bit light to properly serve as anchors.

I don't blame you for trying to maintain originality, but I recommend the advice of the much-more-patient-than-I dddd, as my record with these is abysmal.

Aubergine 

3alarmer 

...what he said ^^^^. I was just working on one of these yesterday, which I use on a Grand Jubilee of about the same age as your bike (because some bastard stole the Jubilee rear derailleur off it. ) It works fine for up to about a 26 large cog freewheel for me, but it's a high maintenance derailleur in terms of lubrication. Otherwise it gets more and more difficult to get it to shift through the full range onto the smaller cogs. I'm also using it on a 6 cog freewheel.

I can't imagine you'll have trouble keeping it going, because Schwinn put so many of the "Schwinn approved" ones into the used parts stream.

Salamandrine 

I like Allvit derailleurs. IMO they've been unfairly maligned. Allvits work just fine if properly adjusted and maintained. I think the doorstop reputation started during the bike boom era. Many were never properly adjusted to start, quickly became clogged with dirt, and finally more often had bent in RD hangers. Flopping your bike over on the drive side was once common practice for the generation that had grown up with one speed coaster brake bikes, or maybe 3 speeds. Once the drivetrain components are all cleaned and lube, and the jockey cage points in the right direction, the shifting is as good as most derailleurs of the era.

non-fixie 

Sorry to hear that. Must have been an exceptional streak of bad luck. Allvits were used on the most expensive hand-built touring bikes here in Europe around 1960, and with good reason. It was the best available derailleur at the time.

The ones I have didn't need much more than a damp rag and a few drops of light oil to function as intended, i.e. shifting a 14-28 5-cog FW with a satisfying clunk and being able to handle a rather surprising (and welcome, I might add) amount of chain wrap.

I built a bike for mrs non-fixie with an Allvit, and ended up quite jealous. So I built another one with an Allvit for myself. We took both bikes to the Retroronde, Eroica Britannia and a week of touring in between last year and they performed flawlessly.

What I really enjoy is riding behind a bike with an Allvit and seeing the mechanism in action. Call me a hopeless romantic, but for me C&V doesn't get much better than that.

OldsCOOL

dddd

The Allvit took parallelogram derailer development literally 180 degrees in one swoop by completely inverting the parallelogram, pivoting from a stationary bottom location instead of from the top.
The result was that the upper guide pulley now tracked even the steep contour of larger freewheels, preserving a more-uniform chain gap distance between the top pulley and the cog that the chain was running on.
Even better, the top pulley moved through an arc which matched the slightly-concave cone profile of the most popular "alpine" freewheel sizes (typically 14-26t, 15-26t or 14-28t) used by touring bikes, sport-touring bikes and the new wave of price-point "ten-speeds" that started flowing into the U.S. around 1960.

Later parallelogram derailers from Shimano and Simplex would modestly approach the inverted Allvit arrangement using a "drop-down knuckle" at the derailer's mounting point, but they likely were still constrained by Huret's patents. Also, the Allvit's fully-inverted parallelogram (with it's super-long upper knuckle) left the dropout hanger more vulnerable to bending in the event of impact, due to the added leverage. Salamandrine has it right about this derailer's added vulnerability to the bike being "flopped on it's driveside", though I have found it easy in practice to grab the Allvit and pull it outward with bare or gloved hands as an added parameter of "roadside adjustment"!

The Allvit was named (translated) "all speeds", which referred to it's ability to handle 3, 4, or 5-speed freewheels of the late 1950's.
Getting one to shift across even an Ultra-6 (narrow) 6-speed freewheel requires a most precise lateral positioning of the freewheel relative to the driveside dropout (but again, one can yank on the Allvit at roadside to "fine-tune" it's position below the freewheel!).
I've had good results using standard Shimano Uniglide 6-speed freewheels with several Allvit derailers, but each took time and effort to diagnose and modify the derailer's travel-limiting mechanical dimensions within the body and parallelogram. Different versions (including Schwinn-Approved) require different parts to be ground down here and there, with paper shims and wet paint used to identify the exact sources of interference (and which made for some "sporting" efforts in the workshop!).

One top-shelf custom bike builder in Japan apparently was so enamored of the Allvit's particular "knee-action" movement that he modified one for dual cables leading to the right shift lever so as to eliminate the stiff spring force (and it's requirement of a heavily-tightened shift-lever friction adjustment).

Of obscure note is one Japanese "copy" of the Allvit, the Sugino VIC derailer. It employed a similar, huge, chrome-plated drop-down knuckle with the slanted parallelogram invented by Suntour. It was part of an indexed 7-speed system (with thumb shifters) and is perhaps the heaviest rear derailer ever made(?). But it's robust construction did not cover for it's relatively-exposed and delicate adjustment screws, which made it and it's front mate a poor off-road derailer set.
See photo at:
https://www.bikestash.com/images/rear...ur_640_480.jpg