Meca Dural Duralumin Bicycle Frame Construction

Meca Dural bottom bracket shell

From the 1930’s through the 1950’s, the French were enamored with aluminum bicycle frames, even though steel was the material of choice for most builders.  A number of examples still exist today, and after disassembling and cleaning this 1940’s/50’s Mercier Meca Dural frame, I can see why.  The bottom bracket shell is a work of art, looking as if it had been machined yesterday, rather than more than 6 decades ago.

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I became curious about the method of joining the aluminum tubes with aluminum lugs, using what I had read were internal steel expanders.  Apparently, at the time there was no method to “glue and screw” the aluminum tubes, a method that was pioneered by ALAN beginning in the early 1970’s.  The only joining methods which were available then were gas welding the tubes – a process used by Nicola Barra; connecting octagonal aluminum tubes into aluminum lugs with connector bolts – a process used by Pierre Caminade; joining the tubes with aluminum lugs and wedged internal expanders – the method used by Meca Dural, and other other hybrid methods involving pinning the lugs, and using a steel rear triangle.

When I passed my magnet over the frame, I picked up no attraction, except for a very faint pull near the lugs.  You will note that the chain stays and seat stays are connected with a combination of bolts and aluminum sleeves, and that the bottom bracket shell is held in place with two large bolts connecting the lug to the chain stays.  The aluminum sleeves do double duty as the brake bridge and chain stay bridge.

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The seat tube/seat stay lug is pinned, as you can see above.  But what about the main tubes – how do the internal expanders work?

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As it turns out, it was fortunate that the Meca Dural headbadge was missing, which allowed me to peer into the head tube lug to examine the expander inside.  My magnet told me that the expander is steel, and the method to accomplish the expansion process seemed to involve a steel tab which was probably manipulated with a special tool.  When you think about it, the same idea is used for quill stems inserted into threaded steerer tubes.  That seems to have worked pretty well, so why should these lugs be any different?

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At first I wasn’t sure of the purpose for the large holes underneath each of the two headbadges.  Upon closer examination, you can see that the head tube and head lugs are actually machined as one piece.  The holes are necessary so that the expanders can be inserted to join the top tube and down tube, necessitating a hole for each tube.  And that is why there are always two headbadges on every Meca Dural frame -to cover these holes.  That’s one mystery solved.

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One thing that seems true of older aluminum frames is their flexibility, relative to steel frames.  My ALAN is a very flexible frame, but not too flexible.  I guess you would say it is flexible in the right kind of way.  To satisfy my curiosity about this frame’s flex characteristics, I squeezed the rear dropouts to test the amount of flex.  Then, in my unscientific experiment I compared the amount of flex on this frame, to all the other bare frames hanging in my shop, all of which are steel, and some of which are Reynolds 531.  I was able to flex the dropouts on the Meca Dural about 7 or 8 mm, using my weaker left hand at full force.  On several mixte frames, I could barely move the drop outs 3 mm, and on a diamond vintage Reynolds 531 frame, I could flex the drop outs about 6 mm at full force.  That’s a significant difference in flex, and it will be interesting to see how this frame rides once I have it restored.

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With just some minor polishing with a wadding cleaner (I use NEVRDULL), the frame shines beautifully.  I need to source some 650b wheels from the period, because at some point someone tried to install 700c wheels on this bike, and that is how the bike was configured when I acquired it.  The spacing at the rear dropouts is 115 mm, so it would be hard to find the vintage hubs to build a wheel set, even though I have a nice vintage set of rims.  Instead, I am on the hunt for a donor vintage bike from the 40’s or 50’s which can give me a decent 650b wheelset, and maybe a few other parts to add to my collection.


A 1940’s/50’s Mercier Meca Dural

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This French Mercier bicycle has captured my attention.  It is made from duralumin – the same stuff blimps were made with – by Meca Dural using a unique procedure to join the tubes with aluminum lugs and wedged steel internal expanders.  The Meca Dural company produced aluminum frames from the 1930’s through the 1950’s on behalf of a number of cycling manufacturers, Mercier being one of them.  A Mercier Meca Dural is included in the Embacher collection (which was sold in its entirety at auction, earlier this year).  The blackbirdsf site also has photos of a variety of duralumin frames of various manufacturers, including Aviac and Barra, as well as Meca Dural.

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This Mercier Meca Dural is a “ladies” bike with a step through frame, although it is not a mixte frame as it lacks the set of extra chain stays typically used to stiffen the frame.  Depending on many factors, this may or may not be a good thing.

The bike features a Stronglight crankset with 46 teeth, CLB 700 brakes with useful and ingenious quick release mechanism, Atom hubs, Samir Saminox 700c rims, Huret plunger/pushrod derailleur, a 4 speed freewheel, and a serial number on the left side rear drop out – 16822.  Here are some photos of the components:

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Huret derailleur with plunger/pull chain mechanism – for 4 speed freewheel.

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Stronglight 49D crankset

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Tank pedals

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Atom hub with Huret wingnuts

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Very nice CLB 700 brakes

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Mercier headbadge, with upper round Meca Dural headbadge missing

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Crankset lettering – Louis Verot chainring with 46 teeth, bottom bracket connector bolt

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Rear drop out with SN 16822

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Beautiful lug design which includes cable routing braze-ons

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Ideale Leather Saddle, Model 80

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Alloy porteur bars, CLB Guidonnet levers, Sufficit grips, Luxor headlamp, Dural Azur stem

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Luxor 65 headlamp

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Samir Saminox 700c steel rims

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Bottom bracket lug, joined below with bolts

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Hammered Le Martele Lefol fenders, hammered rear lamp.

Mercier fork

Steel fork with lugged chrome fork crown, amateur paint job, Stronglight headset

The bike has a number of issues which will affect the restoration process.  The steel fork was horrifically spray painted gray  – so the paint will need to be removed.  Upon closer examination, I have concluded that the wheels are not original to the frame.  There is a 1975 date code on the Atom hub, and not only that, their diameter suggests that this bike was built for 650b wheels and not 700c – the fork crown and rear brake bridge daruma bolts foul the 700c tires.  Clearly the bike was built for 650b wheels, which I confirmed after measuring the CLB 700 brake reach.  And, some features are missing –  the fenders show that the bike originally had a rear and front rack, and the fork mount dynamo is absent, as well as the original chain guard.

Even so, I am looking forward to restoring this machine and to its first test ride, as I want to experience the feel of the aluminum frame and steel lugs, and to judge the frame stiffness for myself.  Stay tuned!

More Than Eye Candy

1973 Jack Taylor

Drooling over gorgeous vintage bicycles is one thing, but appreciating their enduring ride quality is another thing altogether.  This 1973 Jack Taylor Tourist has been with me for over eight years, and while I rode it quite a bit initially, I eventually set it aside.  The bike is larger than my usual size, and I did not adequately assess the lack of comfort associated with a 55 cm top tube length, given that I normally ride a 51.

Adding to that are the big 27 inch wheels and 29 cm bottom bracket height.  Throwing a leg over this bike is like mounting one’s 16 hand steed for a ride in the country side.  However, the very tall riding position is great for commuting.  It puts your head up above the fray and helps make you more visible to the car driving masses.  So, in order to enjoy this bike I needed to make some ergonomic changes.  Back to the drawing board.

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I needed to bring the bars closer to me. The tall Nitto Technomic stem came to the rescue.  Drop bars or mustache bars would push my arms out too far for this top tube length, so I located a vintage city style bar that had the right clamp size for the Nitto Stem.  I used Velo Orange levers to complete the vintage look.  Even though new, they are quite a bit more sturdy than the Weinmann and DiaCompe flat bar levers made in the 70’s.  Their only downside is that the levers sit out pretty far from the bar, so they are not the best choice for smaller hands.  I couldn’t resist using some bright yellow Benotto bar tape, which when wrapped three times over fit perfectly on the grip side of the bars, and which brings out the bike’s vibrant yellow highlights.

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This bike is unique in many ways, and one of them is the rear wheel which features this Sachs-Fitchel 2 speed Orbit hub.  The internally geared hub takes the place of a front derailleur and extra chain ring.  I had sent the hub out for a rebuild 8 years ago, not daring to do it myself at the time.  It still feels smooth, so I resisted the very faint urge to tear it down.  The internal gears can be lubricated by removing the spindle and squirting in a bit of automotive oil.  Easily done.  The spindle broke apart a number of years ago, so I did my own repair job using a tiny brad which I banged into the chain links.  The repaired link is slightly bigger than it should be, but hasn’t caused any problems.  One of the nice things about this gearing arrangement is being able to shift to a lower gear when stopped.  That’s not something you can do with a 100% derailleur equipped bicycle.

Whenever a bike sits for a while, all kinds of things go wrong.  Grease congeals, one kind of metal fuses itself to another kind of metal, bearings embed themselves into their cups and cones, and rust seems to form everywhere.

So, there were lots of other issues to address:  pitted bottom bracket cups, which I replaced with an exact and pristine match that I happened to have in stock; broken wiring for the sidewall driven Soubitez dynamo; and various rusted areas on the frame which needed to be sanded and then painted (I use clear Testor’s paint).  I had considered replacing the dynamo with something newer, but it is actually working just fine, and I can use it as a back up to my battery powered light if needed.  (P.S. I hate dynamos).

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Soubitez dynamo headlight is working!

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Testor’s Paints – I use clear paint for touch ups.

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Inelegant wire routing. Oh well.

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Perfect for commuting – Lyotard pedals with reflectors and cage tabs to keep your shoe in place.

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Frame touch up – sanded and painted.

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Very tight clearance due to low tread Stronglight 99 crankset.

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IRC Road Winner 27 x 1 1/4 tires

I really like these IRC 27 x 1 1/4 inch tires.  I purchased them eight years ago and unfortunately, they can no longer be found.  Not not only do they have a nice appearance, the sidewalls are very supple and the ride quality is even better than the much beloved Panaracer Pasela’s I have ridden.  I hope to ride these tire until the bitter end, and replace them only when absolutely necessary.  One issue with these older rims is that they cannot tolerate high pressures, due to their design.  So, I have blown these tires off the rim more than a few times.  Finally, I have settled on 70 psi in the rear and 65 psi in the front, and have had no blow outs since.

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In addition to rebuilding the pedals, front hub, and bottom bracket, I also replaced the straddle cables for the Mafac Cantilever brakes.  The brakes, while very powerful, are noisy under hard braking, partly because I am using these Kool Stop pads which not only don’t allow for toe-in, they seem to provide for the opposite of toe-in.  Even so, I would rather have these strong and reliable cantilevers for commuting in Portland.

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And finally, I sourced an exact match for the taillight with the broken reflector. I kind of miss the look of the bare bulb, though.

Now it’s time to get back out on this bike into this Fall’s windy, rainy weather and ride the leaf strewn avenues of Portland – hopefully in comfort!