Grand Bois

I'm guessing that you have a claw that's for a Huret derailer, but your derailer is set up for a hanger with the stop in the standard Campy position. The stop on a Huret hanger is too far forward. If that's the case, you just need to switch to a standard Campy-style claw.

southpawboston

Second revival of this thread!

So is the main body of the duopar (the part that bolts to the dropout and supports the "first" parallelogram) supposed to be able to freely rotate about the dropout the way that most derailleurs do? Or is it supposed to remain fixed in place, while the "second" parallelogram takes care of positioning the jockey wheels closer to or farther away from the cogs.

I just installed a Duopar on a frame with a Shimano-style dropout hanger, and with the tabbed and keyed washer at the dropout stop, the main parallelogram is at about a 45 degree angle.

jan nikolajsen 

While mine is not exactly seized in place, it certainly is snug and doesn't move during shifting. 45 degrees works real good on my bike.

Road Fan

That sounds right, Southpawboston. The chain tension created by the arm tends to position the main parallellogram forward. It can be pivoted backwards to make it easier to pull off the rear wheel.

45 degrees sounds ok, to me. I've installed them on bikes with Shimano or Campy-style hangers maybe half a dozen times. Got one now on my 1984 Trek 610.

southpawboston

Thanks Jan and Road Fan. The thing is, I'm concerned it won't be able to work well with the 12-32 8-spd cassette it's being mated to. The larger cogs, no problem at all. The "second" parallelogram can bring that upper jockey wheel nice and close to the larger cogs. However, when trying to negotiate the smallest two cogs (12 and 14T), the second parallelogram can't get close at all-- probably 2cm away at best. Is this going to cause shifting problems? Furthermore, the only way the first parallelogram can span the 8 cogs laterally is with the limit screws all the way out. Again, not a problem for the largest cog, but for the smallest cog, the derailleur does something funny: if the second parallelogram is all the way "up" (close to the cogs) as the first parallelogram is moving laterally out toward the smallest cog, the second parallelogram contacts and interferes with the first parallelogram before it reaches the limit screw and the derailleur gets stuck somewhere between the two smallest cogs. i.e., the lateral range is more limited when the second parallelogram is in the up position, closer to the cogs. I just installed it tonight and don't have a chain on it yet, but just playing around with it with my hands, the only way the derailleur can move laterally all the way to the smallest cog is if the second parallelogram is partially or all the way "down". If this is too confusing, I'll upload some pics to illustrate. And perhaps I'm overanalyzing things before putting them full together!

Road Fan

The Duopar was not designed in teh days of freewheels wider than 7-speed. If you're getting it to span an 8 at all, consider yourself lucky.

I haven't used one with a 12, but I've used it with many 13s. I can't believe the free length is much different between the 12 and 13, and I find the shifts into and out of my 13s are as seamless as can be.

I'd say, just put it together and ride it. I think Huret did a great job designing this. Give it a chance to do what it was designed for, then you'll know. Watch out for the limit screw, don't lose it. I don't think we're as good at visually analyzing as we think. I know I'm not.

Captain Blight

So, a favor:

Would someone with the tools and skills be willing to measure up and either accurately describe or annotate a photo of this mythical tabbed washer? I'm a handy guy with a set of files and a frickin' virtuoso (in my own mind) at the grinding wheel. It's just that I've got a new-to-me bike that's just begging for a Duopar rear mech, and I'd like to be able to use my Eco.

Or could someone with the spare parts handy compare and contrast one with the tabbed front-wheel washers that have been mentioned-- or maybe a Sturmey washer? Ya folla?

I have a feeling other people than me would be really grateful.

Grand Bois

The Duopar wasn't the only model to use that tabbed washer. You may be able to find a lesser Huret derailer that has the part you need. The best ones had a "B" screw on the washer so you could adjust the angle. I bought a cheap steel Huret derailer on eBay and was able to make the washer from it work on a Duopar by bending the tab 180 degrees and turning the washer the same amount. The washer has to have little nubs on it that fit into the slots in the derailer and keep it from rotating. That makes the washer hard to fabricate.

See post #25 for a picture of a tabbed washer.

Captain Blight

Doesn't actually help. I am considering doing a short production run of these, so all the information I can get is not too much. Since I do not myself have a Huret washer and do not expect to see a Huret washer at any point in the foreseeable future, this is the next best thing.

thook

Hello gentlemen,

I was wondering if someone with Duopar experience could help me figure something out? I bought one months ago and I'm finally getting around to the build I wanted to put it on. I'm mounting it to a bolt on hanger as there is no hanger on the frame. The problem is, it won't rotate at the hanger pivot bolt. I have all the hardware save this little, transparent washer in this link.........

https://lh6.ggpht.com/_jIpsYYJIn_4/TH...t1hardware.jpg

Is that my problem? If so, would any standard, thin washer work in lieu of not having it?

Thank you for any input!

Oh, btw, just what is the little, beveled bolt for at the far right end in the above link?

thook

Bump to the top!..........

thook

Um.........nevermind. Got it.

yellowdog76

Did you ever find or make campy Huret washers?

gmt13

Kind of late to post this, but I found this photo album to be quite helpful. https://www.flickr.com/photos/28267220@N05/sets/72157623530295917/with/4446539901/.
I did some measurements from the pics and was able to manufacture a washer to fit a duopar to a Huret dropout. Scrap aluminum and some drilling and filing.

-G

bocobiking

I just mounted a Huret Duopar Eco and took it for a ride. I love it.

But does anyone know the steps to removing the rear wheel when using this rear derailleur?

Aubergine 

The DuoPars are the best friction rear derailleurs ever.

What problem are you having with removing the wheel?

artclone

The Duopar's hanger bolt is meant to be loose enough to allow it to swing backwards which really helps when removing the rear wheel.

There's a lock nut on the back of the hanger to lock in this small amount of play. If not, this is the problem - - the deraillur is just tightened all the way down. This doesn't hurt anything until you need to change wheels.

3alarmer 

...until the aren't. Then they are vexatious.

Aubergine 

Yes, all those pivot points need regular lube. They definitely are not as bombproof as the contemporary Suntour derailleurs.

JohnDThompson 

Pretty much the same as with any other derailleur: shift to the smallest cog, rotate the derailleur body out of the way, and slide the wheel out.

N.B. you can also easily disengage the pulley cage spring to remove tension from the chain, which is also helpful sometimes.

JohnDThompson 

Some Duopars (maybe only the titanium ones; I can't remember) use an allen socket expansion bolt threaded from the back to lock the upper pivot adjustment:

artclone

Cool! I did not know that.

bocobiking

I'm not using a separate hanger claw; my derailleur is mounted directly to the dropout. The tabbed washer is mounted with the mounting bolt, and the tab is resting on the campy dropout notch. There is no other locknut, nor is there room for one on the mounting bolt. I have tightened the mounting bolt down until the derailleur cannot rotate. With this setup, the derailleur is functioning fine, but I would need to loosen the mounting bolt to remove the wheel (not a big problem).

Given all of that, should I loosen the derailleur a bit so that it pivots, or leave it tight? I read different answers in different places.

Thanks for your help.

dddd

There are at least three ways that a tightened mounting bolt can allow for free rotation of the derailer about the pivot bolt.


1) The bolt features a stepped-up diameter above the threaded end, which bottoms on the hanger, thus preventing tightening torque from binding the "B-knuckle" at the mounting bolt.


2) The bolt features extended threading for a locknut on the reverse side of the hanger mounting hole. The Locknut locks the bolt without the bolt pinching the B-knuckle, so the derailer is free to rotate about the mounting bolt.


3) The mounting bolt is threaded internally where it is threaded externally, allowing a set screw to be tightened inside of the threaded end of the mounting bolt, thus expanding the bolt so it cannot move within the hanger mounting hole. The derailer again is free to rotate about the mounting bolt which effectively acts like a rigid part of the frame without having it be tightened down against the derailer's B-knuckle.


I use a Duopar derailer on my Trek 510 with the mounting bolt tightened down on the derailer's upper (B) knuckle.
The washer tab broke off long ago as the washer is hardened, and thus brittle. You cannot bend these things!
I have great difficulty removing the rear wheel. I first remove the QR completely and then "finesse" the wheel out of the frame without loosening the mounting bolt. I'm sure this would be easier with vertical dropouts, or with even longer chainstays than this sport-touring bike already has.

bocobiking

[QUOTE=JohnDThompson;19932780]Some Duopars (maybe only the titanium ones; I can't remember) use an allen socket expansion bolt threaded from the back to lock the upper pivot adjustment:



Wow! I just found it. Ingenious. What a piece of arcane knowledge about an obsolete part. Thanks.