I'll throw my experience on the pile here.
Originally Posted by
sykerocker
For it's day (somewhere along the line of just before we all discovered Sun Tour), the Simplex line of derailleurs were THE low buck alternative to everything else out there....
By the mid-80's Simplex had gone to the Japanese style horizontal parallelogram, by which point it was too late
Fritz, if you are interested in some level of originality understand that "back in the day" the original owner might quite likely have replaced the derailleurs with Suntour after a few years. Skyerocker is quite right about the timing - Suntour was the cheap and excellent way to go when you wanted to upgrade. The surprising thing is that you found a bike with original derailleurs. But you won't be violating C&V-ness if you replace them, especially if you use one of the Suntour V models.
You can certainly use the Simplex derailleurs if they aren't broken. But do examine the front for cracks in the clamp, and the rear for cracks in both top and bottom knuckles.
As for Simplex copying the Japanese design, they did but they left out one key element. Suntour's big innovation was the slant parallelogram which made the cage move up and down along with out and in, respectively. Their patent ran out in, ah, '86 if remember right, at which point everybody started doing it. The later Simplex RD looked similar with the cage being horizontal and the rear pivot moved backwards, but they never put in the slanted axis that made it move up and down! So while they
look like a slant parallelogram RD, they don't
act like one.
Originally Posted by
Sluggo
Perhaps the least satisfactory part of the system is the plastic shift levers, which were flexy and added a lot of slop to the system.
My guess is that with current freewheel tooth shapes and chains, these would shift just fine.
Some people tend to break the levers, but I've been using Simplex DT levers on my UO8 since about '73 or '74. Have commuted on it about 800 miles this year. (I bought the bike in '72 [I think, though it may have been '73] but it came with stem shifters, and eventually I replaced them.) Operate them smoothly and by gripping the entire lever, metal housing and all, and they should be fine. Of course, now mine will probably break tomorrow.
I agree that modern chains and gears should shift fine with the Simplex. Anecdotal evidence: I put Simplex derailleurs on a tandem I rebuilt last winter, and so far they have shifted quite nicely.