jPrichard10 

I hope it's not bad to start a new thread about this, but the title of the old one is misleading at this point.

This is a frame with aftermarket Peugeot decals applied, but it's clearly not a Peugeot. Components, if any of them are original, are from the early 70s.

Wraparound scalloped seatstays, Georg Fischer bottom bracket, Swiss BB threading, imperial tubing measurements (28.6mm) bocama lugs, Campagnolo dropouts, 26.8 seatpost, mostly French components. No fork, sadly.







Some folks said Allegro, but there is no seat tube serial number. All the markings I can find are in the bottom bracket, and there are many. 56 stamped between the chainstays might be the frame size? I had seen the five digit serial number before, but the +GF+ Georg Fischer marking, a 48 stamp on the bottom and a 1 stamp closer to the downtube lug are newer finds from me.





No rivet holes on the headtube. The brake housing guides on the top tube look unusual to me; maybe added after the fact? Never seen any look this bad before.

Any ideas? Allegro seemed promising if not for the serial number. I have seen some Mondias with wraparound seatstays as well but not with Bocama lugs and GF bottom bracket shells. I just don't know enough about Swiss bikes (or bikes that used Swiss threaded bottom brackets) to identify this further.

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oneclick 

That top headset race looks a bit askew.

juvela

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the combination of this BOCAMA lug pattern with this seat stay treatment, Georg Fischer Swiss thread sandcast shell with the prominent lip on the drive side certainly shouts "Allegro!"

the 28.6mm tubing diameter is definitely puzzling; you could verify by taking measurements in different spots


one inquiry you could make would be to examine interior of head tube to see if there is any evidence of headplate fastener holes being filled in

while in there you could check for signs of original colour

shall look forward to reading what our numerous Allegro experts have to communicate


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PhilFo 

I LOVE classic bike forensics.

jPrichard10 

​​​​​​It definitely is; I have probably set it down on the race accidentally a few times trying to remove the bb cups. I'm likely replacing it anyway.

I'm aware that this might not actually be Swiss; I know at least Motobecane used Swiss threaded bottom brackets (I think with metric tubes though). Can't imagine Swiss threading was that common though. Does anyone know of builders in other countries using it?

I feel like the size stamped between the chainstays might be the most recognizable feature, so really hoping someone can find a picture of another builder with the size stamped there (in the same typeface).

rustystrings61 

As @juvela put it, the Bocama 14 type II lugs, seat stay wraparound treatment, sand-cast Fischer BB shell threaded for Swiss DO shout "Allegro!" The wraparound seat stay top is IDENTICAL to the one I had on my c.1974 model 76, which I found notable. I don't recall ever seeing a wraparound top that looked exactly like that, and it sure looks like an Allegro to me.

The things that argue against it being an Allegro are the seat post diameter (26.8 mm vs. the 26.6 mm, which is both what Allegros I have encountered took as well as being about the largest diameter post one can fit into a metric sized, 28.0 mm seat tube. Also, the lack of the serial number ingot on the left side of the seat tube.

The lack of head tube rivets is not a determining factor here. Allegro used both riveted metal headbadges and head tube decals. The database info I gathered shows sn 175513 with Nervex Pro lugs (c.1960) with a decal, then 195448, 208420, 210909, and 224502 with head tube decal and Bocama 14/II lugs.

Have ALL the tubing exterior measurements been checked to be certain they're Imperial all the way around? Is it possible that this bike was originally an Allegro; for some reason it became necessary to replace the seat tube, and the repair was done by reaming things out a bit and squeezing an IMPERIAL seat tube into a metric 531 frame - while adding bottle bosses and top tube cable tunnels and shaving off the fender eyelets?

I know the serial number is stamped -

1
94741

but if we read it as 194741 that would point towards an early '60s frame with Bocama 14/II lugs that someone restamped on the BB shell - those numbers look like they were stamped later - that someone repaired and modified and repainted.

Or am I just really, really reaching?

juvela

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absence of plating on taper tubes means that eyelets could have been excised post-manufacture

may have been performed when hydration provision was added...

overall impression is one of slight roughness as compared with what one normally finds on a vintage Special

makes me wonder if frame may be a half-step or so below the level of the Special

present finish appears to have been applied directly to the steel without the intermediary of primer


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jPrichard10 

Reach away! I'm open to all theories at this point.

I haven't found any signs of old paint, so if it has been repainted someone removed everything and masked very well.

Of all the wraparound seatstays I have found, none quite match other than Allegro's. I am tempted to remove some paint and see if there may have been a seat tube serial badge at some point, but not sure if it would "show" on the bare steel or not.

Also not sure if the tubeset would be stamped anywhere? I have an old fork I got at the co-op that had "Reynolds 531x stamped into the blade once I sanded it down, but don't know if that would be the case for frame tubes (or where to look).

I can't remember the measurements off the top of my head, but I measured at least the seat tube and downtube and they weren't straight metric sizes.

Not sure what to make of the "48" on the BB shell; it looks cast in at the same time as the +GF+. Is this a typical Georg Fischer treatment?

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juvela

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serial ingot would have been brazed on

if it were removed there would likely be some residue visible of the brazing material

the "48" marking on the shell could be a mould (cavity) number from Fischer


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rustystrings61 

Not all Allegros with 531 and Bocama 14/IIs got chrome. The “C” grade versions that came stock with Stronglight P3 headsets were unchromed - not shown in catalogs but made in some quantity with cottered cranks and Weinmann 500 sidepulls. Craig Griffith had some for sale years ago, and there are several examples listed in the Google doc above. Maybe the down tube was also replaced … I have a Mercian that had top and down tubes replaced …

juvela

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me comment not about plating/non-plating but about eyelets

reread

yes, aware not all received plating


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jPrichard10 

Maybe quite obvious question, but it seems a given that Allegro used metric sized tubesets?

Would it help measuring the head tube as well (OD and ID)? What numbers am I expecting to find for an Allegro?

I don't see any chrome, but I might sand down some spots just to make sure. I'm guessing to check the lugs and "socks" first?

bulgie 

I have a few Fischer pieces (crowns and BB shells) and I do remember some numbers cast-in sometimes, but I don't remember details. Not at home to go looking at them now. My shells are the kind Masi used, without the "swelling" around the openings for the threaded cups.

The RR dropout has the "land" for the extra spring hole for Campy Sport derailer, but not the hole. Roughly speaking, DOs with the hole stopped showing up in the early '60s, but the land for the hole continued until they made new forging dies without the land, in the late-'60s I think. However individual makers could have continued using older dropouts for some years after they were gone out of the pipeline from Vicenza. So it's only a rough indicator of age.

If the tubes are inch rather than metric, then 26.8 indicates either a plain-gauge ST or a somewhat heavy single-butted one, with slightly less-likely options including a double-butted ST (more common on Japanese bikes) or one with an internal sleeve added at the lug, á la Cinelli.

That's all I got! Cool frame though. Keep us posted if you find out more.

EDIT: I'm reminded by this pic from ebay, that the cast-in numbers are raised ("outies"), not sunk, so they are often filed/sanded off if the shell gets any cleanup. Same with the crowns -- raised numbers that almost always get removed during cleanup.


This shell is newer than yours though, so older ones might have had different numbers or styles.

juvela

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metric head tube 32.00mm

BSC head tube 31.75mm

metric top tube 26.0mm

BSC top tube 25.4mm

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BSC dimension frame tubes paired with a CH thread shell is quite an odd/unusual combination

hence speculation regarding things such as tube replacement or mismeasurement


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jPrichard10 

I wish I had long calipers to measure and see if the tubes are butted at all, but I suppose I could measure ID of the seat tube in the BB shell... Unless it's a double butted tube for some reason.

Not sure if that's common practice or not to measure ID of the seat tube in the BB shell. That is, if my calipers actually fit.

jPrichard10 

Mismeasurement is a possibility; the paint job might be a bit thick and rough in some spots.

rustystrings61 

Absolutely in agreement with @juvela on this - I think the eyelets probably went when the bottle bosses and cable tunnels were added. And I suspect some of the roughness is that this was likely the budget variant of this frame, no chrome, no fancy paint, no braze-ons apart from a pip on the downtube for clamp-band shifters and a diver's helmet cable stop on the right chainstay. The grade C variant doesn't appear to have been as finely polished before chrome or finish work, either.
I went back and looked at the one somewhat blurry photo I have of the sand-cast Fischer BB on my old one, no. 241247, has the same "+GF+" and "48" markings - and no other stampings or markings. I am wondering if the "48" is a model number or mould cavity as swell.

Whups! No, we are on the same page here, and apologies!

Did ANY of the classic Swiss builders use non-metric tubing? Mondia? Cilo?

jPrichard10 

rustystrings61 thank you for confirming with the "48"! Model or batch number was my assumption as well.

On the other hand: did any British builders (or other Imperial tubing users) use Swiss bottom bracket threading? Perhaps if they really wanted to use this BB shell, although it seems possible you could tap this for BSC? Just wild speculation from me, since I don't know anything about anything here.

rustystrings61 

I got curious about the substitution of ISO/Imperial tubing in a frame originally built metric and posted this over in the framebuilding forum -

"There is a lively discussion over in the C&V section regarding a mystery frame that appears at first blush to be a Swiss-built Allegro - the Bocama no.14 type II lugs, the distinctive wraparound seat stay top, the shape of the indents in the right chainstay, "diver's bell" chainstay cable stop, the sand-cast George Fischer BB shell and Swiss threading. However, this one appears to have IMPERIAL dimension seat and down tubes, as well as some other things that don't match, though they may well be changes made during a repair/repaint - no fender eyelets on the Campagnolo 1010 dropouts, likely added bottle bosses and top tube cable tunnels.

Is it possible to removed damaged METRIC 531 tubing, with it's 28.0 mm diameter, and swap in IMPERIAL 28.6? How about downtube replacement? Is there sufficient slop in the tolerances of the stamped steel Bocama lugs and the cast Fischer BB to permit that? I have been wondering if this bike started as an Allegro and required replacement of the seat and down tubes with whatever was on hand.

I'm pretty sure the Mike Melton-repaired Mercian I have involved subbing in metric Vitus 971 for the destroyed original Imperial gauge 531 top and down tubes on it, and I can see using smaller diameter tubes as replacements - but can it go the other way around?"

We'll see if we learn anything from that.

juvela

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no one questioning your vernier caliper skills

it can sometimes happen that a tube is put slightly out of round by the heat of brazing

in such a case one could get a "large" or a "small" measurement result depending on where caliper applied


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bulgie 

Measuring the wall thickness of a tube anywhere but at the ends is tricky. I have a "butt sniffer" similar to this one, by Farr Frameworks:



It needs calibration to read anything like the actual thickness, and is best thought of as a comparative measure. As in, how much thicker is the butt versus the unbutt? It definitely can distinguish between single-butted and double-butted seat tubes though. Send your frame to me if you want me to use my butt-sniffer -- or bring it to anyone else who has made their own. They're not exactly common but many framebuilders have them. Or make yourself one; it's not too hard.

Measuring the thickness at the top on a finished frame is notoriously difficult due to the vagaries of heat distortion, reaming etc. It can be inferred from the seatpost size that fits, but with a large uncertainty.

Measuring the ID at the bottom by reaching in thru the BB shell opening is durn near impossible. Even if you had calipers the right shape (most are not), you'd be measuring to a hefty burr. Properly deburring to allow a better measurement is conceivable, but hard to prove you have deburred it enough, i.e. hard to trust the number you got. Then there's still the heat-distortion problem. I consider it effectively un-measurable without destroying the frame.

jPrichard10 

Well, I stand corrected -- and I should have measured in more than one spot first. While there are many places where my calipers read 28.6, most places are 28.2-28.4. Top tube is 26.2 or higher, never dropping anywhere near 1" range for an Imperial measurement.

Edit to add: does this make the 26.8 seatpost a bit odd? That seems to make the tube walls rather skinny. The Campy seatpost has 26.8 on it and it doesn't look like it has been shaved down at all.

Sorry for all the hubbub about tubing diameters; this was definitely a metric tubesets, and the top tube should have been the only information needed to confirm that, as it's nowhere near 25.4.

I guess we're to the point where I sand the seat tube and see if there's any sign of a former Allegro serial badge? Not sure if that's an overkill move or not. If it's not an Allegro, someone tried awful hard to mimic one.
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jPrichard10 

Wait, one more question that's been nothing me before I take the paint stripper to it: do other Allegros have the size stamped on the back of the bottom bracket just below the chainstays? This is still something that no one here has addressed.

juvela

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"Edit to add: does this make the 26.8 seatpost a bit odd? That seems to make the tube walls rather skinny. The Campy seatpost has 26.8 on it and it doesn't look like it has been shaved down at all."

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given all the "attention" it has received by someone previously t'is not at all unreasonable to consider it may have been the recipient of a seat tube ream

two possible causes come to mind -

a) deformantion at top of seat tube due to overtightening of binder

b) had a 26.8mm size pillar to hand which wished to employ


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obrentharris 

My 1961 does not. (Sample size of 1)
Brent