28T in 1950's?
 

Is there a period-correct, early- or mid-1950's, British or European, 4-speed rear derailleur (system) that will accept a 28T cog?
(I have the Cyclo Mk7, but it appears to only take up to a 24T).

198

Maybe a Simplex Grand Prix. I haven't tried it yet - and Velobase doesn't have any data on max chain wrap and cog size- but it looks like there's some room to play with. This is with 24T:

http://myalbum.com/photo/1MUtJMtxjGXK/1k0.jpg

It's interesting how far forward that Simplex mounts, non-.
It kind of gets me thinking about alternate mounting positions
and their effect on freewheel gearing.
I've seen no 4-speed freewheels have a 28T low gear, but
have heard that some do.
I don't really see that Grand Prix being able to clear 28T, but
I may be wrong.

198

I got a Campagnolo Gran Sport to work with a 28.

I'm pretty sure a Cyclo Standard can handle that. Disraeli Gears says 26t, but Standard Cyclo says 28t.

I got a Cyclo Benelux to shift to a 28t as well. It was a four speed derailleur that I used on a standard 14-28 freewheel. I was rarely able to get it into the 14t, but the others were fine.

Sorry to be offtopic, maybe it's just me but I want to soak that with degreaser. Pretty cool derailleur setup, though primitive by todays standards.

Thanks for the suggestion, ia.
Do you know how far back in time the Gran Sport goes?

rh: The Standard Cyclo looks more like non-'s Simplex Gran Prix than mine
(which is a plunger-style). I think mine is dated at 1955.
I might have to look into purchasing a Standard.


Olds: "In winter, a mature man's fancy turns to bicycle mechanics".

198

The Gran Sport RD started in 51 or 52, although there were minor changes over the years and the ones more commonly seen on ebay etc are typically from the late 50s. A Gran Sport may handle 28, depending on how it can be positioned relative to the wheel axle. If mounted on a long Campy dropout with integral hanger, and with the wheel positioned all the way back in the dropouts (adjuster springs removed), it should work. It may not work if using a bolt-on hanger. Lots of 50s derailleurs will work if you can mount them far enough from the freewheel. The other problem with many 50s derailleurs, especially the plunger type, is that they just can't wrap enough chain to give a very wide range, so you have to sacrifice the high gears.

Duk: My bike's dropouts do not have an integral hanger, so I would need a claw-type mount. From what you are saying, that sounds like the derailleur may be positioned too far back (or too high) to clear a large, low gear sprocket.

198

Yes, I think so, if using the usual style of bolt-on hanger. I see lots of different hangers are available nowadays, so maybe there is a longer one that will work. As for vintage hangers, there were various ones available in the 50s that clamp onto the chain stay, for mounting Cyclo Standard (or similar) or the various derailleurs that use the two small mounting bolts. I think these tended to be the touring derailleurs from Simplex, Cyclo, etc, so would also generally provide more chain wrap than the racing derailleurs such as Simplex Tour de France.

The easiest solution might be to figure a way to mount a longer cage on your existing Cyclo, to make it more like the Cyclo Tourist:
Cyclo Benelux Mark 8 Tourist derailleur

In 1950, Campagnolo showed a prototype of the GS. The first production model was in 1951. After several iterations the design stayed essentially the same from 1953 to 1960.

The GS I used with the 28 had a claw hanger, not an integral hanger.

Campagnolo considered the capacity of the Gran Sport to be 26t, as stamped on the back of the derailleur. I think if you go above 26t, the upper jockey wheel may start to interfere with the large cog, depending on derailleur mounting position, wheel position and chain length. So it may still shift onto the 28, but it might crunch and be somewhat noisy once there. In addition, the chain may be slightly slack because the jockey cage is being rotated further than where it should be to maintain chain tension. Another factor that will help the Gran Sport shift onto a cog bigger than 26 is having the chain as short as possible. This keeps the upper jockey wheel further from the freewheel, but may also mean having to avoid using the larger freewheel cogs when on the big chainring.

Again, I ran the 28 without a problem. As for the bit about cross-chaining, yes, don't do it.

Pictures of the setup.

https://farm1.staticflickr.com/596/2...50df102a_h.jpgbtb 023 by iabisdb, on Flickr

https://farm6.staticflickr.com/5681/...d134bb3a_b.jpgbtb 023a by iabisdb, on Flickr

Like I said, I haven't tried it yet, but there's space, and it looks like the location of the plunger can be adjusted, further away from the cogs, so I'll probably give it a try when I get to work on this bike.

No, me too. :) I just got this bike last week, and you're looking at one of the as-bought pics.

ia: Does that claw look like it is removeable? The reason I ask is cause I see a GS for sale at a reasonable price, but it does not have the claw.

198

Yeah. Let me know. Thanks.

Well said! And it looks like you are having a blast with the Grubb!

iab - Looking at your Cinelli, I see how you are able to get your GS to work on a 28. The small difference between chainring sizes allows you to have the jockey cage fairly wound up even when on the small ring. I would assume the OP is planning to use chainrings with a wider spacing than on your Cinelli, as it sounds like he is seeking fairly low gearing. Also, I suspect you would twist your hanger and/or derailleur if you inadvertently shifted onto the big cog while on the big ring. To avoid this grief, most folks prefer to make the chain long enough to permit the large-large combination, even if they never intend to use it. So yes, you can make a GS work on a 28, but there are necessary compromises that may defeat the purpose in wanting to use the 28 in the first place.

It's looking spectacular, Olds. I send some parts out to the machine shop to get polished next week. I know you don't want to wait till the year 2000 to see some pics, but I should have some pretty soon. I'm going for a "brand new bike" look.

My chain rings are 46T-40T.

Those are really good points!

Especially with bigger difference in chainring size, a too-tight chain can damage a lot of parts fast, everything from the frame to the hub and axle, to the chainset, chain, all because the chain isn't long enough to handle the biggest sprockets.

Oddly enough, with many derailers the one thing that [I]won't[I] be damaged from such an occurrence is the derailer itself, as the cage may swing fully out of the way of a full-tight chain!

The leverage that one can exert over the tension of the chain when the chain comes up short must not be under-estimated, and if the chain simply breaks you would be quite fortunate in that case.

That will be sweet. And worth the wait. Cool bike.

In that case, the GS may be a good option. Position the wheel as far back in the dropouts as possible (limited when using a claw hanger), and keep shortening the chain until the derailleur will shift smoothly onto the 28. Then very carefully see how far up the freewheel you can go with the chain on the big ring. It might just all work out fine! Let us know if you try it.