Challenges: Legnano Ofmega BCD and Huret RD thread
12-04-21, 05:04 AM
#1
Junior Member
Thread Starter
Challenges: Legnano Ofmega BCD and Huret RD thread
Hello,
I am building two more old projects and get these problems:
1. I have a Legnano pantographed crank (looks like made by Ofmega) for my basic Legnano. The original chainings (the dirty ones) are worn, so I want to change them. The BCD is very close to 144, but not enough to install Campagnolo 144 BCD chainrings. The distance between adjacent holes in the cranks is a tad more than 84,6 mm and the bolt with 144 chainrings wont fit. Originally Legnano crank had inner chainring with threaded holes. Legnano cranks distance between adjacent holes is about 85,3 mm, but is there a BCD for that?? I cant see any distortion or non symmetry in crank or chainrings...
2. I have a french Special Arliguie frame from about 60's-70's. It has Huret dropouts, but Huret RD bolt won't screw in freely, I forced a bit and it started to rethread the threads from the outer side and these are now good for my derailleurs, but from the inner side (not forced with the bolt) are still not suitable. I tried 2 different Huret derailleurs (Allvit and Svelto), 2 Campagnolo ones and Shimano Tricolor, but the same problem persists. I could be easily retapped, I think, but what is the original problem here? Am I missing something? Are the threads on RD hanger already altered or what? Is it intended for some other derailleur?
I am building two more old projects and get these problems:
1. I have a Legnano pantographed crank (looks like made by Ofmega) for my basic Legnano. The original chainings (the dirty ones) are worn, so I want to change them. The BCD is very close to 144, but not enough to install Campagnolo 144 BCD chainrings. The distance between adjacent holes in the cranks is a tad more than 84,6 mm and the bolt with 144 chainrings wont fit. Originally Legnano crank had inner chainring with threaded holes. Legnano cranks distance between adjacent holes is about 85,3 mm, but is there a BCD for that?? I cant see any distortion or non symmetry in crank or chainrings...
2. I have a french Special Arliguie frame from about 60's-70's. It has Huret dropouts, but Huret RD bolt won't screw in freely, I forced a bit and it started to rethread the threads from the outer side and these are now good for my derailleurs, but from the inner side (not forced with the bolt) are still not suitable. I tried 2 different Huret derailleurs (Allvit and Svelto), 2 Campagnolo ones and Shimano Tricolor, but the same problem persists. I could be easily retapped, I think, but what is the original problem here? Am I missing something? Are the threads on RD hanger already altered or what? Is it intended for some other derailleur?
Last edited by Jantaras; 12-10-21 at 07:34 AM. Reason: Manufacturer name corrected
12-04-21, 06:05 AM
#2
Senior Member
Not all Huret dropouts were threaded for Huret.
10 x1 or 10x26tpi ( Campagnolo) are the alternates
I forget what Native to Huret is.
10 x1 or 10x26tpi ( Campagnolo) are the alternates
I forget what Native to Huret is.
12-04-21, 07:46 AM
#3
feros ferio
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If the chainrings fit over the spider, you could always gently elongate their mounting holes slightly outward, or, maybe better, elongate the mounting holes of that nonstandard spider inward, This is my trick for mounting 130mm BCD chainrings on 128mm BCD Nervar cranks -- works like a champ, and very easily done.
__________________
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
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12-04-21, 09:16 AM
#4
Senior Member
-----
Jantaras -
the OFMEGA chainset worn by your Emilio is a model termed by the manufacturer the Forgiato -
it was later revised and the maker re-christened it Super Corsa "R"; here seen on a catalogue page of 1983 -
the BCD is a nominal 144, do not hesitate to follow John_E 's excellent advice
---
the nominal Huret dropout thread is 10 X 1.0
you could check with a a thread gauge the thread of the dropout and that of the mounting bolt you wish to use; thread gauges are a very low cost item and quite handy
possible that either the male or female threads have been slightly deformed
no harm could be done by running a 10 X 1.0 mm tap through the dropout
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Jantaras -
the OFMEGA chainset worn by your Emilio is a model termed by the manufacturer the Forgiato -
it was later revised and the maker re-christened it Super Corsa "R"; here seen on a catalogue page of 1983 -
the BCD is a nominal 144, do not hesitate to follow John_E 's excellent advice
---
the nominal Huret dropout thread is 10 X 1.0
you could check with a a thread gauge the thread of the dropout and that of the mounting bolt you wish to use; thread gauges are a very low cost item and quite handy
possible that either the male or female threads have been slightly deformed
no harm could be done by running a 10 X 1.0 mm tap through the dropout
-----
12-05-21, 05:41 AM
#5
Junior Member
Thread Starter
Thanks for your insights!
For Legnano cranks I will be modifying the holes, maybe the crank holes, or maybe I will order cheaper 144 BCD chainrings and modify them.
Now, these RD bolts and hangers are real head scratchers for me...
I have a PX8 with a hanger tapped with M10 x 1,0 (I checked it again with a M10 x 1,0 tap). I thought it will fit all Campagnolo type hangers, but I really used Suntour BL GT RD and it's bolt fits good. Now, I checked and this PX8 M10x1,0 hanger won't accept Nuovo Record's bolt. Also, Huret RD bolt won't go. I measured with thread gauge and Nuovo Record and Suntour BL bolt both looks like 1,0 mm thread. Now, Huret RD bolt is very very similar to 1,0, but not quite exact (the fit looks better than in the picture), but definately not 0,9, 1,25 or 1,5. I can't find exact thread match for Huret's bolt.
So, my observations:
tapping Arliguie's hanger to M10x1,0 won't help to accomodate Huret RD bolt
PX8 hanger tapped to M10x1,0 is suitable for Suntour BL GT bolt, but not for Nuovo Record or Huret bolt (although both the BL and Nuovo Record are 1,0 mm threaded)
Arliguie's hangers forced/mangled a bit threads from the outside are good for Nuovo record and Suntour BL bolt, but too tight for Huret's. The inside (native) threads are too tight for any of the bolts...
looks like all three bolts (Nuovo Record, Suntour BL GT and Huret) have slightly different threads...
Maybe its the thread height that is wrong here or what?
For Legnano cranks I will be modifying the holes, maybe the crank holes, or maybe I will order cheaper 144 BCD chainrings and modify them.
Now, these RD bolts and hangers are real head scratchers for me...
I have a PX8 with a hanger tapped with M10 x 1,0 (I checked it again with a M10 x 1,0 tap). I thought it will fit all Campagnolo type hangers, but I really used Suntour BL GT RD and it's bolt fits good. Now, I checked and this PX8 M10x1,0 hanger won't accept Nuovo Record's bolt. Also, Huret RD bolt won't go. I measured with thread gauge and Nuovo Record and Suntour BL bolt both looks like 1,0 mm thread. Now, Huret RD bolt is very very similar to 1,0, but not quite exact (the fit looks better than in the picture), but definately not 0,9, 1,25 or 1,5. I can't find exact thread match for Huret's bolt.
So, my observations:
tapping Arliguie's hanger to M10x1,0 won't help to accomodate Huret RD bolt
PX8 hanger tapped to M10x1,0 is suitable for Suntour BL GT bolt, but not for Nuovo Record or Huret bolt (although both the BL and Nuovo Record are 1,0 mm threaded)
Arliguie's hangers forced/mangled a bit threads from the outside are good for Nuovo record and Suntour BL bolt, but too tight for Huret's. The inside (native) threads are too tight for any of the bolts...
looks like all three bolts (Nuovo Record, Suntour BL GT and Huret) have slightly different threads...
Maybe its the thread height that is wrong here or what?
12-05-21, 12:20 PM
#6
Senior Member
Yeah, those French…
you need a 26tpi gauge- in general that is what Campagnolo is acknowledged to be in the Nuovo: Super Record era
you need a 26tpi gauge- in general that is what Campagnolo is acknowledged to be in the Nuovo: Super Record era
12-06-21, 04:28 AM
#7
Junior Member
Thread Starter
Ok, thanks!
I thought of tapping the hanger threads with M10x1,0 tap (I already have it) and retap the Huret's bolt threads with the M10x1,0 die (I have to order it).
Now, is this Huret bolt too hard for die? Is it chomed or something? If it is too hard, I could use the bolt itself to force and "rethread" hanger threads.
Bike is french and I really want and older type of french derailleur to fit...
I thought of tapping the hanger threads with M10x1,0 tap (I already have it) and retap the Huret's bolt threads with the M10x1,0 die (I have to order it).
Now, is this Huret bolt too hard for die? Is it chomed or something? If it is too hard, I could use the bolt itself to force and "rethread" hanger threads.
Bike is french and I really want and older type of french derailleur to fit...
12-07-21, 06:40 PM
#8
Senior Member
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fine job with the pictures and text description
your eyes are the ones on the scene
if i experienced this symptom the first thing i would check would be to examine the first thread on the Huret bolt under strong illumination to check for any deformation
if found, would try a few strokes with a metric thread file to see if that would put things right
a metric thread file is a low cost tool and a very handy one to keep at one's work station
if not, then next step would be a run a 10 X 1.0 die over the bolt
suspect problem may be due more to manufacturing tolerances/variations rather than differing nominal sizes
-----
fine job with the pictures and text description
your eyes are the ones on the scene
if i experienced this symptom the first thing i would check would be to examine the first thread on the Huret bolt under strong illumination to check for any deformation
if found, would try a few strokes with a metric thread file to see if that would put things right
a metric thread file is a low cost tool and a very handy one to keep at one's work station
if not, then next step would be a run a 10 X 1.0 die over the bolt
suspect problem may be due more to manufacturing tolerances/variations rather than differing nominal sizes
-----
Last edited by juvela; 12-07-21 at 07:00 PM. Reason: addition
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12-10-21, 07:33 AM
#9
Junior Member
Thread Starter
Bolt threads looks fine. Ok, I will be tapping the hanger and the bolt with M10x1,0.
Interestingly the locknut of Huret RD bolt is threading throug M10x1,0 tap freely
I still wonder, if Campagnolo bolt is tight for M10x1,0 threads (that I have tapped for my PX8), how come other derailleur hangers accept all: Suntour, Shimano and Campagnolo bolts freely, without forcing or binding (for example, my Koga Miyata from 80's)? Does it mean it is 10x26 tpi? Does Campagnolo's 10 x26 tpi accept Shimano and Suntour bolts without any resistance?
Interestingly the locknut of Huret RD bolt is threading throug M10x1,0 tap freely
I still wonder, if Campagnolo bolt is tight for M10x1,0 threads (that I have tapped for my PX8), how come other derailleur hangers accept all: Suntour, Shimano and Campagnolo bolts freely, without forcing or binding (for example, my Koga Miyata from 80's)? Does it mean it is 10x26 tpi? Does Campagnolo's 10 x26 tpi accept Shimano and Suntour bolts without any resistance?
