Little-Acorn

This is a spinoff from another thread ("Weird freewheel") that got a little off-topic.

I got one of those old 14-38 5-speed freewheels with the superhuge big cog on Ebay. I'd like to put it on a '73 Schwinn Super Sport 10sp, just for kicks and grins. That bike came with a 14-32, which wasn't bad, but I'd like to really make a hillclimber out of it. I'm sure the original derailleur won't be able to handle that 38-tooth big cog, though.

Any recommendations what rear derailleur would be able to handle this beast? I've heard a Huret Duopar, and a Shimano Tourney RD-TX51.

Any others that might be able to shift through the entire range of this 14-38?

fuzz2050

Damn, a 38 is huge... I can't vouch for that, but my Duopar Eco (The cheap version, same design but less titanium) can easily shift through my 12-34.

Retro Grouch 

Suntour Alpine Gear Tech is what you are looking for. It was designed to handle the 38 tooth big cog. I don't know where to find one.

cmcanulty

The shimano Tourney RD-TX51 works , it comes with or without hanger. It's pretty cheap at
https://www.jensonusa.com/store/produ...erailleur.aspx

meb

If that doesn't work, how about mounting a derailleur hanger on your derailleur hanger?
I've got a pair of those 14-38s I haven't installed yet, so if the Tourney works let us know.

Spicer used to make a Granny cog adapter for mounting a chainring on a Shimano cassette. I don't see the adapter on their site anymore. It was used primarly for mountain bike fixed/singlespeed, but someone must have tried that on derailleur and got that working.

cmcanulty

I got mine from this ebay seller. I called him and he recommended the tourney, call Chris there
https://cgi.ebay.com/SUNTOUR-FREEWHEE...3286.m20.l1116

Panthers007

My SunTour Mountech would do it - but it's also prone to blowing apart.

Little-Acorn

Well, I finally put the 14-38 freewheel (aka "dinner plate") on my '73 Super Sport, without changing the Schwinn-approved derailleur. Seemed to go fine in the lower four gears, and I was astonished when I shifted to the huge 38-tooth cog - it shifted right up to it with barely a clatter or grind. Wow, what a low gear.

But then I found the Schwinn-approved derailleur would not shift back down OFF the 38-tooth cog. The chainwheel on the derailleur closest to the 38-tooth cog, hung up on it like a railroad wheel on a steel track, and the spring wasn't strong enough to shove it off when I pulled the shift lever to relax the cable. In fact, I had a hell of a time getting it down onto the smaller cogs even after getting off the bike and pulling at it with my fingers. Finally got it back down.

So now I basically have a 8-speed bike, which is pretty much what I expected, with the biggest cog only accessible in an emergency, with major handwashing needed after getting off the bike to drag the derailleur back down where it belongs afterward.

So, I now have a Shimano Tourney RD-TX51 (with hanger) on order. About $15 from Bicycle Warehouse (Amazon.com has them for $11, but correspondingly higher shipping charges). Will hopefully put it on this weekend. And even more hopefully, it might even work.

Anyone had any further experience with these 14-38 five-speed freewheels?

Panthers007

That's good - I just got the last Huret Eco-Duopar off eBay. NOS and the Grand Jubilee model. Yahoo!

For future reference: I had both the Titanium Duopars and the Eco's back in the day. They both worked the (flawless) same way. But the Huret Titane (titanium) were not as strong and would bend with little provocation. And they sold for twice the price.

TireLever-07

Thats some low gear Acorn. The Shimano *Megarange* was only a 34 tooth first gear. I'd guess it was back when the usual crankset was 40-52 or a 42-52 tooth. Having a lower mounted derailler would likely be trouble for you on any surface. Chris

Little-Acorn

Well, the '73 Super Sport is a road bike. Only "surface trouble" I've ever had with a road bike, is banging a pedal on the ground in a high-speed turn while pedalling, which on reflection was maybe a dumb thing to do. That was on its kissing cousin, a Sports Tourer.

I just picked up the new Shimano derailleur, BTW, at Bicycle Warehouse on the way home from work. Haven't had time to install it, but I briefly held it up next to the axle and old derailleur and stretched it out. It does look like the closest derailleur chainwheel, will be well clear of that big 38-tooth cog. I'm greatly encouraged - the Huret Duopar I got on Ebay months ago, doesn't seem to clear (couldn't mount that one due to missing the mounting bolt and washers, which turn out to be very duopar-specific).

Hopefully I can mount the Shimano soon, and find out once and for all if the 14-38 dinner plate can be used!

Little-Acorn

Someone's selling one in Texas.

https://dallas.craigslist.org/dal/bik/1118130739.html

Panthers007

That's a later production from the Huret. Sachs-Huret produced them for awhile, then Huret took it back over. They might be fine, but I'd rather take a new original production.

Little-Acorn

Well, I just put the new Shimano RD-TX51 rear derailleur on, and it shifts thru ALL the gears! Including onto the giant 38-tooth rear cog on that 14-38. And it even shifts back down off it, on command! Happy-happy, joy-joy!

Except... (there's always an except)

When I shift to the 38-toothed cog in back, the guidewheel on the derailleur does not move out far enough to give the chain any room between it and the cog. The chain rides up onto the cog as it should, taking the guidewheel with it. Feels like a normal, easy, correct shift in all ways. But then as you pedal, there's a rumbling from the derailleur, because its guidewheel is more or less riding on the largest cog, with the chain pinched between it and the cog.

The derailleur came with a hanger that is clamped under the rear wheel axle (and is held steady with a small bolt), as is common. The derailleur's "main body" (I call it) mounts to the other end of the hanger, with a spring-loaded swivel. The spring in that swivel, holds the main body as close to the axle as possible - you can push the main body away from the axle, thus giving the guidewheels more room between them and the cluster, but you have to push against the spring swivel to do it.

This seems a little bassackwards to me. It's that spring swivel, that's holding the closest guidewheel, too close to the 38-tooth cog. If the spring in the swivel were holding the main body AWAY from the axle instead of close to it like it does, this problem would be cured. But there doesn't appear to be anything I can change or adjust, to make it so.

I have the instructions that came with the derailleur, written in eighteen languages, including English which was mighty white of them. It describes all the usual adjustments, which I did, including adding two two-section links to the chain. But it's had this other probem throughout, where the closest guidewheel rides directly on the largest cog with the chain pinched between.

The instructions describe "using the B-tension adjustment screw", which was the only one I guessed could have any effect on the spring swivel holding the main body of the derailleur. But I've adjusted that through its full range, and it didn't seem to have any effect, at least not enough to keep the guidewheel from pressing on the chain and largest cog.

It's frustrating in a way. If I just reach in and move the derailleur main body outward manually, pushing against the spring tension of that swivel, it's an easy push, the body swings away, and the problem is solved - there is now plenty of room (it only needs a quarter inch or so) between the guidewheel and largest cog. And the derailleur shifts beautifully that way, through all gears without a slip, no rumbling or grinding, the birds sing, the sun shines, and all is right with the world. And then when I let go, the spring swivel brings the main body back clse to the axle, the guidewheel starts rumbling on the cog and chain when it's on that largest cog and, well, you know.

Anyone know of a way to persuade this Shiman RD-TX51 rear derailleur to stop cozying up to its closest-to-the-axle position? Preferably without the use of baling wire or super glue?

rickowensis

Try this: Remove the B screw and screw it in from the opposite side to gain a bit more adjustment. That should do it.

a77impala

Make sure when you swing the deraileur back you don't go to far and the chain starts skipping on the gear because the chain isn't contacting enough cogs to keep it from riding over the tops when under power.

dit

Is it possible that your chain is slightly too long? I had the same problem with a different setup just a couple of days ago and I took one link out of the chain and the problem went away and she rides just fine now.

Little-Acorn

Well, glory be, I dug an old pull spring (Home Depot technology) out of the tool box, clipped it and bent the ends to suit, looped one end around the bottom of the rearmost stay of the Pletscher rack where it bolts to the frame, brought the spring around the back of the derailleur, and hooked the other end on the steel pin next to the cable pulley. The spring pulled the main body of the derailleur down about 1/2" but still left it free to swing back and forth with changing chain tension or whatever.

And now it shifts onto and off that huge cog on the 14-38 freewheel, like it was born to do it! No more rumbling or rattling, shifts as smoothly as you could ever want, and such a simple fix that even I could do it.

Success! Now I can definitively say that the Shimano RD-TX51 is a very good derailleur for that giant 14-38 5-speed freewheel, at least on a '73 Schwinn Super Sport road bike. Provided you have an understanding hardware store nearby.

Even works smoothly when I'm on the biggest front chainwheel and biggest rear cog (38 teeth), and also when on the smallest front chainwheel (39 teeth) and smallest rear cog (14 teeth). And all other combinations and perturbations. I haven't found a way to break it yet!

And now when I want to hit that steep hill, I have a 39 in front and 38 in back, meaning almost exactly one wheel rotation per pedal rotation. If that can't handle the hill, then I didn't really want to go up it anyway.

Jeff Wills

Phiddlesticks. In Portland, there's some great hills. Have a look:

I have a 24/34 low gear- good for fragile knees.