"brevettata" tandem?
Ryan Cousineau
At a guess, I google-translated the name, and (as many of you know) it
means "patented" in the land of Giros and Fiats.
Any ideas what make of tandem would likely be misidentified this way? Or
is it a real marque?
I hope to take a look at it fairly shortly.
--
Ryan Cousineau rcou...@sfu.ca http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos
A Muzi
> I'm trying to chase down the provenance of a bike I haven't seen yet.
> At a guess, I google-translated the name, and (as many of you know) it
> means "patented" in the land of Giros and Fiats.
> Any ideas what make of tandem would likely be misidentified this way? Or
> is it a real marque?
> I hope to take a look at it fairly shortly.
Can't help with your specific problem but it happens all the time.
As in "I have this [part, bike, rim]. It's a "Brevettata" [or "Brevete",
or "SGCG", or "SICC", or "VIA", or "8.8.8." or by "Pat Pending", the
industrious Irishman who made so many things. . .] Can you fix those?".
He has no idea what it is. He looked at a part marked -
Brevettata= Patented, Italy
Brevete= Patented, France
SGCG= French engineering society
SICC = Italian version
VIA= Japanese Vehicle Industry Association, a qualitative certification
8.8.8. = Suntour trademark, Shimano's is 3.3.3.
Good luck with your tandem, whatever it may be!
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
rcou...@gmail.com
> Ryan Cousineau wrote:
> > I'm trying to chase down the provenance of a bike I haven't seen yet.
> > At a guess, I google-translated the name, and (as many of you know) it
> > means "patented" in the land of Giros and Fiats.
> > Any ideas what make of tandem would likely be misidentified this way? Or
> > is it a real marque?
> > I hope to take a look at it fairly shortly.
>
> Can't help with your specific problem but it happens all the time.
> He has no idea what it is. He looked at a part marked -
> Brevettata= Patented, Italy
> VIA= Japanese Vehicle Industry Association, a qualitative certification
Well, that at least explains why it says that on Shimano parts :).
> Good luck with your tandem, whatever it may be!
Thanks, Andrew.
After talking briefly with the seller, it appears to be a pretty old,
probably 3-speed (hub gear) tandem, apparently in lightly-used shape.
It's blue, chrome fenders, some sort of flat or "priest" or typical 3-
speed handlebar.
I'm going to see the bike tonight (the price is in my range, and I
just want a "around the park" tandem for me and the missus). I don't
want a bike that will fall apart in a mile, but looks are probably
more important than how many gears it has.
Any general remarks on tandems of this type? Is there likely to be
some freaky Italy-specific issues I might not expect versus, say, an
English or American tandem of the same era?
A Muzi
>>> I'm trying to chase down the provenance of a bike I haven't seen yet.
>>> At a guess, I google-translated the name, and (as many of you know) it
>>> means "patented" in the land of Giros and Fiats.
>>> Any ideas what make of tandem would likely be misidentified this way? Or
>>> is it a real marque?
>>> I hope to take a look at it fairly shortly.
> A Muzi <a...@yellowjersey.org> wrote:
>> Can't help with your specific problem but it happens all the time.
>> He has no idea what it is. He looked at a part marked -
>> Brevettata= Patented, Italy
>> VIA= Japanese Vehicle Industry Association, a qualitative certification
rcou...@gmail.com wrote:
> Well, that at least explains why it says that on Shimano parts :).
> After talking briefly with the seller, it appears to be a pretty old,
> probably 3-speed (hub gear) tandem, apparently in lightly-used shape.
> It's blue, chrome fenders, some sort of flat or "priest" or typical 3-
> speed handlebar.
>
> I'm going to see the bike tonight (the price is in my range, and I
> just want a "around the park" tandem for me and the missus). I don't
> want a bike that will fall apart in a mile, but looks are probably
> more important than how many gears it has.
>
> Any general remarks on tandems of this type? Is there likely to be
> some freaky Italy-specific issues I might not expect versus, say, an
> English or American tandem of the same era?
Send photos to me or some other doddering old bikie for a general
assessment. Or, better, post some photos for RBT review! There aren't
simple guidelines but we can help you avoid known or obvious troubles.
James Thomson
> Brevettata= Patented, Italy
> Brevete= Patented, France
> SGCG= French engineering society
I think you might be thinking of SGDG, "Sans Garantie du Gouvernement", a
disclaimer issued by the state meaning that the granting of a patent is not
an endorsement of fitness for purpose:
http://fr.wikipedia.org/wiki/Sans_garantie_du_gouvernement
James Thomson
A Muzi
>> Brevettata= Patented, Italy
>> Brevete= Patented, France
>> SGCG= French engineering society
James Thomson wrote:
> I think you might be thinking of SGDG, "Sans Garantie du Gouvernement", a
> disclaimer issued by the state meaning that the granting of a patent is not
> an endorsement of fitness for purpose:
> http://fr.wikipedia.org/wiki/Sans_garantie_du_gouvernement
Yes, a typo, sorry.
Thank you
A Muzi
>> Brevettata= Patented, Italy
>> Brevete= Patented, France
>> SGCG= French engineering society
James Thomson wrote:
> I think you might be thinking of SGDG, "Sans Garantie du Gouvernement", a
> disclaimer issued by the state meaning that the granting of a patent is not
> an endorsement of fitness for purpose:
> http://fr.wikipedia.org/wiki/Sans_garantie_du_gouvernement
I just read the article. I was wrong, it is not similar to SICC at all.
Thank you _very _ much.
Ryan Cousineau
A Muzi <a...@yellowjersey.org> wrote:
> >> Ryan Cousineau wrote:
> >>> I'm trying to chase down the provenance of a bike I haven't seen yet.
> >>> At a guess, I google-translated the name, and (as many of you know) it
> >>> means "patented" in the land of Giros and Fiats.
> >>> Any ideas what make of tandem would likely be misidentified this way? Or
> >>> is it a real marque?
> >>> I hope to take a look at it fairly shortly.
>
> > A Muzi <a...@yellowjersey.org> wrote:
> >> Can't help with your specific problem but it happens all the time.
> >> He has no idea what it is. He looked at a part marked -
> >> Brevettata= Patented, Italy
> > I'm going to see the bike tonight (the price is in my range, and I
> > just want a "around the park" tandem for me and the missus). I don't
> > want a bike that will fall apart in a mile, but looks are probably
> > more important than how many gears it has.
> >
> > Any general remarks on tandems of this type? Is there likely to be
> > some freaky Italy-specific issues I might not expect versus, say, an
> > English or American tandem of the same era?
>
> Send photos to me or some other doddering old bikie for a general
> assessment. Or, better, post some photos for RBT review! There aren't
> simple guidelines but we can help you avoid known or obvious troubles.
Well, you can't help me avoid trouble now that I've bought the bike!
It turns out it was...a 20"-wheeled folding(ish) tandem!
http://flickr.com/photos/rcousine/413380853/in/photostream/
Note graceful curved, integral rack/rear end.
http://flickr.com/photos/rcousine/413380855/in/photostream/
Here's the head badge ("G") and frame sticker.
http://flickr.com/photos/rcousine/413380857/in/photostream/
http://flickr.com/photos/rcousine/413380859/in/photostream/
Sorry about the taken-in-haste (repent at leisure) photos.
There's another badge that is all but obliterated, except for some faint
traces of the Italian tricolour. The notorious "BREVETTATA" badges were
just under the seatpost clamps on both seat tubes.
Cottered cranks, Aprilia (!) lighting system driven by a sidewall
generator, Carnielli (?) saddles. The strange hanging dropouts seem to
have a "C" cut into them (the second photo shows the mirror-image one on
the left side)
The frame has a proper split-shell eccentric front BB, and all the
frame's folding points (seatposts, hinge, bars, stem) have 8mm hex bolts
in them.
The brakes are Sturmey-Archer drums front and rear. The rear is an AB
(cable-operated drum) 3-speed hub stamped "70", which should be the
production year. Hub seems in good order, but only one gear is available
right now. That's the first order of business.
The shifter is mounted on the stoker's seatpost.
The "keel tube" is a pair of parallel bolted-in tubes about the same
diameter as the rear rack/triangle/whatever tubing. The rear "triangle"
also appears unboltable, though you'd have to be trying to fit this
sucker in a Cinquecento to want to do so, I suspect.
It's shopworn, but obviously lightly used. It looks cute and amusingly
retro. It should hold up well for around the park. The frame appears to
be braced in all the likely failure points, and construction is by
indifferent-looking welds.
C$220 took the whole thing away.
So, what is it?
Scott Gordo
> In article <12urh6o1ldlv...@corp.supernews.com>,
> "I don't want kids who are thinking about going into mathematics
>
> - Show quoted text -
I've had a couple of those gimmicks in the non-tandem version. One
said that it was made by Bianchi, and made in Italy. I've had another
one with identical construction that bore some Frenchy name I can't
recall.
All I can say is that what they had in style they lacked in any sort
of torsional rigidity. They're commically flexy, from the handlebars
on down, so doubling up on one, ESPECIALLY as a single speed...if you
see anything that looks like a hill, head in the other direction.
Keep an eye on them quick releases, especially the one that holds the
stem in place. The ones on my bikes were an insult to Tullio.
With all that said, it'll be a funny little ride and will def raise
some smiles.
/s
ps: Oh yeah, I don't believe that ANY of those parts followed any kind
of standard, so don't leave it out in the snow ;)
David L. Johnson
> Well, you can't help me avoid trouble now that I've bought the bike!
>
> It turns out it was...a 20"-wheeled folding(ish) tandem!
>
> http://flickr.com/photos/rcousine/413380853/in/photostream/
Durndest looking thing. Are those front and rear drum brakes? Good
thing that it won't be able to climb worth a damn, because trying to
stop with those on a downhill would be interesting. But it will
certainly get some attention.
--
David L. Johnson
Enron's slogan: Respect, Communication, Integrity, and Excellence.
jta...@nospam.hfx.andara.com
<david....@lehigh.edu> wrote:
>Ryan Cousineau wrote:
>
>> Well, you can't help me avoid trouble now that I've bought the bike!
>>
>> It turns out it was...a 20"-wheeled folding(ish) tandem!
>>
>> http://flickr.com/photos/rcousine/413380853/in/photostream/
>
>Durndest looking thing. Are those front and rear drum brakes? Good
>thing that it won't be able to climb worth a damn, because trying to
>stop with those on a downhill would be interesting. But it will
>certainly get some attention.
Drum brakes are more effective with small wheels.
carl...@comcast.net
Dear J,
Is this a matter of rim caliper brakes being less effective on small
wheels? Or what?
Cheers,
Carl Fogel
rcou...@gmail.com
Considering that this thing uses steel rims, I'm pretty happy about
the drum brakes. And yes, it has front and rear S-A drum brakes (rear
is integrated into an "AB" 3-speed hub).
A Muzi
Most probably made by Carnielli (they made Bottecchia & Graziella
besides Carnielli label exercise/child/specialty bikes). These 20-inch
frame system components were sold to many European manufacturers. You
can see the similarity to my Bianchi. Gitane, Cazenave, etc, etc were
built from the same parts with minor detail changes.
http://www.yellowjersey.org/aq.html
A Muzi
>>>> Well, you can't help me avoid trouble now that I've bought the bike!
>>>> It turns out it was...a 20"-wheeled folding(ish) tandem!
>>>> http://flickr.com/photos/rcousine/413380853/in/photostream/
>> "David L. Johnson" <david....@lehigh.edu> wrote:
>>> Durndest looking thing. Are those front and rear drum brakes? Good
>>> thing that it won't be able to climb worth a damn, because trying to
>>> stop with those on a downhill would be interesting. But it will
>>> certainly get some attention.
> jta...@NOSPAM.hfx.andara.com wrote:
>> Drum brakes are more effective with small wheels.
carl...@comcast.net wrote:
> Is this a matter of rim caliper brakes being less effective on small
> wheels? Or what?
With a 20" wheel you can skid a drum, can't with a 'full size' wheel
carl...@comcast.net
wrote:
Dear Andrew,
Any idea why?
Can you skid a 20" rim caliper? (Fogel Labs does not stock the wheel
or courage needed to test what I presume are front wheel skids.)
I'm not arguing, just curious whether all brakes are more effective on
smaller wheels or if reducing the wheel size favors drums over rim
calipers or what.
Cheers,
Carl Fogel
carl...@comcast.net
Looking at what Andrew wrote one more time, I wonder if the idea is
that a drum can skid a 20" wheel, but a drum can't skid a 27" or 700c
wheel?
So before I find out why, I need to figure out what people are saying.
My guess is that almost any brake can skid any rear tire.
700c front rim caliper
Can or can't skid?
(Can't is my understanding.)
700c front drum
Can or can't skid?
(I'm guessing can't.)
20" front rim caliper
Can or can't skid?
(I'd guess can't, but maybe people are saying can?)
20" front drum
Can or can't skid?
(I'm surprised, but people seem to be saying it can?)
CF
A Muzi
>>>>>> Well, you can't help me avoid trouble now that I've bought the bike!
>>>>>> It turns out it was...a 20"-wheeled folding(ish) tandem!
>>>>>> http://flickr.com/photos/rcousine/413380853/in/photostream/
>>>> "David L. Johnson" <david....@lehigh.edu> wrote:
>>>>> Durndest looking thing. Are those front and rear drum brakes? Good
>>>>> thing that it won't be able to climb worth a damn, because trying to
>>>>> stop with those on a downhill would be interesting. But it will
>>>>> certainly get some attention.
>>> jta...@NOSPAM.hfx.andara.com wrote:
>>>> Drum brakes are more effective with small wheels.
>> carl...@comcast.net wrote:
>>> Is this a matter of rim caliper brakes being less effective on small
>>> wheels? Or what?
> A Muzi <a...@yellowjersey.org> wrote:
>> With a 20" wheel you can skid a drum, can't with a 'full size' wheel
carl...@comcast.net wrote:
> Can you skid a 20" rim caliper? (Fogel Labs does not stock the wheel
> or courage needed to test what I presume are front wheel skids.)
> I'm not arguing, just curious whether all brakes are more effective on
> smaller wheels or if reducing the wheel size favors drums over rim
> calipers or what.
No mystery, I think you can _see_ it. The ratio of the drum diameter to
rim diameter is more favorable. Ask any mechanic who ever built a
Schwinn Crate new out out of the box. On a tile floor.
David L. Johnson
>>> Is this a matter of rim caliper brakes being less effective on small
>>> wheels? Or what?
>> With a 20" wheel you can skid a drum, can't with a 'full size' wheel
>
> Dear Andrew,
>
> Any idea why?
I'll volunteer an idea. A 20" wheel has less leverage between the road
and the hub than a 27" wheel; the amount of braking force at the hub
would be twice as much for a wheel of twice the radius, to get the same
braking force at the tire.
On the other hand, since a caliper brake is at the rim, the braking
force of a caliper brake would be independent of the wheel radius.
> I'm not arguing, just curious whether all brakes are more effective on
> smaller wheels or if reducing the wheel size favors drums over rim
> calipers or what.
I'd say that small wheel size favors drums over calipers.
Ben C
> On Wed, 07 Mar 2007 15:14:43 -0700, carl...@comcast.net wrote:
>
>>On Wed, 07 Mar 2007 15:46:32 -0600, A Muzi <a...@yellowjersey.org>
>>wrote:
>>>With a 20" wheel you can skid a drum, can't with a 'full size' wheel
>>
>>Dear Andrew,
>>
>>Any idea why?
>>
>>Can you skid a 20" rim caliper? (Fogel Labs does not stock the wheel
>>or courage needed to test what I presume are front wheel skids.)
>>
>>I'm not arguing, just curious whether all brakes are more effective on
>>smaller wheels or if reducing the wheel size favors drums over rim
>>calipers or what.
>>
>>Cheers,
>>
>>Carl Fogel
>
> Looking at what Andrew wrote one more time, I wonder if the idea is
> that a drum can skid a 20" wheel, but a drum can't skid a 27" or 700c
> wheel?
>
> So before I find out why, I need to figure out what people are saying.
>
> My guess is that almost any brake can skid any rear tire.
It should be able to, especially if you jam it on quite sharply, to be
sure to lock the wheel before the braking surfaces get a chance to heat
up too much.
Whether you can skid the front wheel depends on whether you endo first,
which you might expect to be the case on a dry road with a good tyre. It
also depends on how far back/forward your weight is.
But there is another question about wheel size which I have been
puzzling over and still don't have an answer to.
If the front wheel is locked, the bicycle and its front wheel can be
regarded as a single rigid body. There is a force rearwards
acting at the contact patch, and from that you can work out the torque
on the bike, and at what rate of deceleration it will endo.
But what if the front wheel isn't locked? In this case the system is not
a single rigid body, but is more complex. I initially started modeling
this as a rearwards force on the bicycle acting at the front axle
instead of at the ground, but I won't try to explain this further until
I feel more like I've figured out whether it's right or not. And if you
think about it, there are two ways to endo-- you can pivot around the
front tyre contact patch, or you can pivot around the front axle, with
the front wheel still turning.
If you are pivoting around the front axle, a smaller front wheel will
tend to make it easier to endo (and hence harder to skid the front
wheel), since the perpendicular distance from where the force is acting
to the centre of mass is greater.
Here is a herring to think about: imagine a bike with enormous wheels
and a low-slung seating position, such that you are 1m above the ground,
but half a metre _below_ the centres of the huge wheels. Now imagine a
similar bike, with the same wheelbase, but with small wheels. You are
still 1m above the ground, but now you are also half a metre above the
centres of the wheels. Will the second bike be easier to endo? Either
bike can theoretically endo around the contact patch, the first one
you'd think can't endo around the axle.
> 700c front rim caliper
> Can or can't skid?
> (Can't is my understanding.)
My estimate is can if the road is a bit slippery.
> 700c front drum
> Can or can't skid?
> (I'm guessing can't.)
Can if the road is slippery and the drum effective.
> 20" front rim caliper
> Can or can't skid?
> (I'd guess can't, but maybe people are saying can?)
>
> 20" front drum
> Can or can't skid?
> (I'm surprised, but people seem to be saying it can?)
If the drum brake is only able to exert a certain maximum force, then
that will result in a smaller force at the contact patch for a bigger
wheel as in a bigger wheel the drum is at a greater mechanical
disadvantage. This may be a reason why it might be easier in practice to
skid the smaller wheel with a drum brake.
But if you believe my herring about where braking forces act, then you
would expect the smaller wheeled bike to endo easier, and that there
will therefore be some road conditions in which its ability to skid is
limited by its tendency to endo.
peter
> >>carl...@comcast.net wrote:
> >>> Is this a matter of rim caliper brakes being less effective on small
> >>> wheels? Or what?
> >>
> >>With a 20" wheel you can skid a drum, can't with a 'full size' wheel
> >
> >Dear Andrew,
> >
> >Any idea why?
The torque exerted on the wheel by the road surface is proportional to
the radius of the wheel. The opposing torque exerted by the brake is
proportional to the radius where the pads are located.
Therefore a given size of drum (or disk) brake will be more effective
when used with a smaller rim compared to a larger one. OTOH, rim
caliper brakes have almost the same effective radius for both the
brake surface and the tire/road surface and the short-term braking
power isn't affected much by wheel size. But a smaller rim is less
able to dissipate heat, so small-wheel bikes with rim brakes are more
subject to problems related to rim heating.
Mark Hickey
> carl...@comcast.net wrote:
>> Can you skid a 20" rim caliper? (Fogel Labs does not stock the wheel
>> or courage needed to test what I presume are front wheel skids.)
>> I'm not arguing, just curious whether all brakes are more effective on
>> smaller wheels or if reducing the wheel size favors drums over rim
>> calipers or what.
>
>No mystery, I think you can _see_ it. The ratio of the drum diameter to
>rim diameter is more favorable. Ask any mechanic who ever built a
>Schwinn Crate new out out of the box. On a tile floor.
Another way to look at it is that the drum brake surfaces are moving
past each other about 35% faster with a 20" wheel (since the wheel
will be turning faster at a given speed). So... to the drum brake,
the forces stopping the 20" wheeled bike from 20mph will be equivalent
to the forces stopping a 27" wheeled bike from only about 15mph.
OTOH, the heat ultimately generated will be the same either way.
Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame
carl...@comcast.net
wrote:
Dear Mark,
I'd wondered about the ratios that you and other posters have
mentioned, but I'm still wondering about the skidding and whether it's
a small front tire on clean, dry pavement.
I can see that the drum's leverage improves with a smaller wheel, but
it seems as if the rim caliper would still have an advantage.
In any case, I don't see yet how a smaller front wheel would allow
skidding on clean, dry pavement when a larger front wheel won't skid.
Maybe there's some geometry change? Or maybe I've misunderstood which
wheel?
Meanwhile, this is as good a spot as any to announce that I saw what
may be the first turkey vultures of spring, circling in the late
afternoon sun and being harried by what turned out to be a pair of
crows.
Whenever they turned, the almost-level sunlight would light up the
white trailing undersides of their black wings in a gorgeous fashion.
Alas, by the time I got a camera out, I could barely see just one
vulture, lurking in the shadows of its customary 70-foot blue spruce:
http://i19.tinypic.com/2nvtizn.jpg
It's a wretched picture, taken through a fork in a tall elm tree, but
that's why they like their tall spruce--plenty of privacy, with easy
take-offs and landings.
Cheers,
Carl Fogel
Ryan Cousineau
"Scott Gordo" <blubb...@gmail.com> wrote:
> I've had a couple of those gimmicks in the non-tandem version. One
> said that it was made by Bianchi, and made in Italy. I've had another
> one with identical construction that bore some Frenchy name I can't
> recall.
>
> All I can say is that what they had in style they lacked in any sort
> of torsional rigidity. They're commically flexy, from the handlebars
> on down, so doubling up on one, ESPECIALLY as a single speed...if you
> see anything that looks like a hill, head in the other direction.
>
> Keep an eye on them quick releases, especially the one that holds the
> stem in place. The ones on my bikes were an insult to Tullio.
The good news is there are _no_ quick releases on this bike. The places
where you would expect them, there are these inch-tall, heavily-built
collars held together with 8mm hex bolts.
Even the frame hinge is held together that way.
If you look upthread, this frame has a lot of the tropes of Andrew's
pink Bianchi, most notably the bulged head and seat tubes.
> With all that said, it'll be a funny little ride and will def raise
> some smiles.
Undoubtedly. It's wife-approved!
> ps: Oh yeah, I don't believe that ANY of those parts followed any kind
> of standard, so don't leave it out in the snow ;)
Andrew: wanna sell your Bianchi?
--
Ryan Cousineau rcou...@sfu.ca http://www.wiredcola.com/
A Muzi
> Andrew: wanna sell your Bianchi?
Heck I just bought it in 1975 and it's only been welded and painted 3
times - I'm just getting used to it!
Ben C
[...]
> I'd wondered about the ratios that you and other posters have
> mentioned, but I'm still wondering about the skidding and whether it's
> a small front tire on clean, dry pavement.
>
> I can see that the drum's leverage improves with a smaller wheel, but
> it seems as if the rim caliper would still have an advantage.
It does, a rim caliper always has the best leverage. With a drum or disk
brake, you have to compensate for the reduced leverage by adding more
leverage somewhere else in the mechanism.
I haven't looked at drum brakes, but I imagine the cable pulls a lever
which operates the shoes. How long that lever is is quite important-- it
might be much longer than the equivalent lever on a rim caliper. And/or
there may be some mechanical advantage inside the drum in the way the
actual shoes are operated.
This is why I'm surprised that drum brakes should be force-limited--
you'd think that it wouldn't be too hard to design in an equivalent
mechanical advantage to offset the fact that the brake is acting at a
smaller radius, and allow any rider with averagely strong hands to apply
enough force to lock the wheel.
Force is one thing, the rate at which a brake can dissipate energy is
another, and that seems generally to be the harder part of brake design.
But that's more significant for long descents and prolonged braking,
usually less so for a quick stop or sudden brake application intended to
provoke a skid.
It may be that drum brakes aren't specifically designed for a size of
wheel, so when you put a drum brake all geared up for a large wheel on a
small-wheeled bike the brakes are sharper than you expect, so it becomes
easier to lock the wheel and skid inadvertently.
Mark Hickey
> Mark Hickey <ma...@habcycles.com>wrote:
>>Another way to look at it is that the drum brake surfaces are moving
>>past each other about 35% faster with a 20" wheel (since the wheel
>>will be turning faster at a given speed). So... to the drum brake,
>>the forces stopping the 20" wheeled bike from 20mph will be equivalent
>>to the forces stopping a 27" wheeled bike from only about 15mph.
>>
>>OTOH, the heat ultimately generated will be the same either way.
<snip>
>In any case, I don't see yet how a smaller front wheel would allow
>skidding on clean, dry pavement when a larger front wheel won't skid.
>Maybe there's some geometry change? Or maybe I've misunderstood which
>wheel?
Consider that, on the 20" wheel'd bike, the brake surfaces are moving
past each other 35% faster, thereby producing 35% more friction at a
given brake lever force. I think that explains it (though much
simplified, and I'm sure minus a number of fascinating details that a
brake expert would add).
>Meanwhile, this is as good a spot as any to announce that I saw what
>may be the first turkey vultures of spring, circling in the late
>afternoon sun and being harried by what turned out to be a pair of
>crows.
Niiiice. I was recently visiting my son and his family in East Texas,
and was out for a morning ride on my daughter-in-law's MTB through a
local preserve by a lake. As I came around a bend in the trail, a
pair of bald eagles swooped out of a tree, down the trail in front of
me. What amazed me most was the SIZE of the larger of the two, and
the noise generated by their (huge) wings. Sadly, no camera (and even
if I had one, I'm sure I would have still missed the shot due to an
overdose of awe).
Ben C
> carl...@comcast.net wrote:
>
>> Mark Hickey <ma...@habcycles.com>wrote:
>
>>>Another way to look at it is that the drum brake surfaces are moving
>>>past each other about 35% faster with a 20" wheel (since the wheel
>>>will be turning faster at a given speed). So... to the drum brake,
>>>the forces stopping the 20" wheeled bike from 20mph will be equivalent
>>>to the forces stopping a 27" wheeled bike from only about 15mph.
>>>
>>>OTOH, the heat ultimately generated will be the same either way.
>
><snip>
>
>>In any case, I don't see yet how a smaller front wheel would allow
>>skidding on clean, dry pavement when a larger front wheel won't skid.
>>Maybe there's some geometry change? Or maybe I've misunderstood which
>>wheel?
>
> Consider that, on the 20" wheel'd bike, the brake surfaces are moving
> past each other 35% faster, thereby producing 35% more friction at a
> given brake lever force.
If you're going at 20mph, the rim is rushing past the brake shoes at
20mph. This is the same for any rim diameter.
jta...@nospam.hfx.andara.com
Perhaps you missed the part of the thread wherein it was mentioned
that drum brakes were under discussion...
Ben C
Ah, now I get it. The smaller wheel spins faster (rpm) than the bigger
one for a given road speed. So assuming the drums are the same radius,
then the brake surfaces will be rushing past each other faster on the
smaller wheel.
Scott Gordo
> In article <1173281732.453734.50...@q40g2000cwq.googlegroups.com>,
Didn't notice it was a 3sp. That will definitely help.
> > Keep an eye on them quick releases, especially the one that holds the
> > stem in place. The ones on my bikes were an insult to Tullio.
>
> The good news is there are _no_ quick releases on this bike. The places
> where you would expect them, there are these inch-tall, heavily-built
> collars held together with 8mm hex bolts.
>
> Even the frame hinge is held together that way.
I was planning on doing the same thing, but I wound up just selling
them instead. I'm pretty sure that I've read here that a good QR can
provide more clamping force than regular nuts and bolts, but, like I
said, these were some pretty poor QRs.
> If you look upthread, this frame has a lot of the tropes of Andrew's
> pink Bianchi, most notably the bulged head and seat tubes.
Mine bikes had the same. That swanky loop that forms the rear triangle/
rack was my favorite aspect of the bike.
> > With all that said, it'll be a funny little ride and will def raise
> > some smiles.
>
> Undoubtedly. It's wife-approved!
Riding our old Schwinn tandem is the most dumb-fun my GF and I have.
It's like an instant parade -- strangers lining the streets smile and
wave. We should hand out balloons. I just hope that you guys are
lighter than we are.
> > ps: Oh yeah, I don't believe that ANY of those parts followed any kind
> > of standard, so don't leave it out in the snow ;)
>
> Andrew: wanna sell your Bianchi?
>
> --
> Ryan Cousineau rcous...@sfu.cahttp://www.wiredcola.com/
> "I don't want kids who are thinking about going into mathematics
> to think that they have to take drugs to succeed." -Paul Erdos- Hide quoted text -
>
> - Show quoted text -
/s
A Muzi
> [...]
>> I'd wondered about the ratios that you and other posters have
>> mentioned, but I'm still wondering about the skidding and whether it's
>> a small front tire on clean, dry pavement.
>> I can see that the drum's leverage improves with a smaller wheel, but
>> it seems as if the rim caliper would still have an advantage.
Ben C wrote:
-snip-
> It may be that drum brakes aren't specifically designed for a size of
> wheel, so when you put a drum brake all geared up for a large wheel on a
> small-wheeled bike the brakes are sharper than you expect, so it becomes
> easier to lock the wheel and skid inadvertently.
Bingo!
Ryan Cousineau
"Scott Gordo" <blubb...@gmail.com> wrote:
> On Mar 7, 8:27 pm, Ryan Cousineau <rcous...@sfu.ca> wrote:
> > In article <1173281732.453734.50...@q40g2000cwq.googlegroups.com>,
> > "Scott Gordo" <blubberp...@gmail.com> wrote:
> > > On Mar 7, 2:07 am, Ryan Cousineau <rcous...@sfu.ca> wrote:
> > > > In article <12urh6o1ldlv...@corp.supernews.com>,
> > > > A Muzi <a...@yellowjersey.org> wrote:
> >
> > > > > >> Ryan Cousineau wrote:
> > > > Well, you can't help me avoid trouble now that I've bought the bike!
> >
> > > > It turns out it was...a 20"-wheeled folding(ish) tandem!
> >
> > > >http://flickr.com/photos/rcousine/413380853/in/photostream/
> > > With all that said, it'll be a funny little ride and will def raise
> > > some smiles.
> >
> > Undoubtedly. It's wife-approved!
>
> Riding our old Schwinn tandem is the most dumb-fun my GF and I have.
> It's like an instant parade -- strangers lining the streets smile and
> wave. We should hand out balloons. I just hope that you guys are
> lighter than we are.
Heh. At our fattest, the two of us don't break 300 pounds together.
Actual riding weights should be substantially less than that.
--
Ryan Cousineau rcou...@sfu.ca http://www.wiredcola.com/
carl...@comcast.net
wrote:
[snip]
>Heh. At our fattest, the two of us don't break 300 pounds together.
>Actual riding weights should be substantially less than that.
Dear Ryan,
You meant to write, "At my fattest, the two of us don't break 300
pounds together."
Pointedly,
Mrs. R. Cousineau
b...@mambo.ucolick.org
> carlfo...@comcast.net wrote:
> >In any case, I don't see yet how a smaller front wheel would allow
> >skidding on clean, dry pavement when a larger front wheel won't skid.
> >Maybe there's some geometry change? Or maybe I've misunderstood which
> >wheel?
>
> Consider that, on the 20" wheel'd bike, the brake surfaces are moving
> past each other 35% faster, thereby producing 35% more friction at a
> given brake lever force. I think that explains it (though much
> simplified, and I'm sure minus a number of fascinating details that a
> brake expert would add).
It would be better to think in terms of torque
and force, because braking is a force, not
dependent on shoe velocity; you get roughly the
same braking force when applying the lever at
20 mph and 10 mph.
Suppose the brake shoes are at 50 mm radius from
the axle and apply a force Fbrake when the lever is
squeezed. This exerts a torque = Fbrake*50 on the wheel.
The actual decelerating force is the force at the
tire radius Rtire, Fdecel = torque/Rtire.
Rtire is maybe 335mm for a 700c wheel and 250mm
for a 20" wheel, so the same drum brake on the
small wheeled bike is about 1.3x more effective.
Ben
Ryan Cousineau
carl...@comcast.net wrote:
Duly noted.
But actually, on those occasions when I blog about the missus, she is
inevitably described as "The Lovely One," which is a tidily
pseudononymous phrase.
Ben C
> On Mar 8, 6:21 am, Mark Hickey <m...@habcycles.com> wrote:
>> carlfo...@comcast.net wrote:
>
>> >In any case, I don't see yet how a smaller front wheel would allow
>> >skidding on clean, dry pavement when a larger front wheel won't skid.
>> >Maybe there's some geometry change? Or maybe I've misunderstood which
>> >wheel?
>>
>> Consider that, on the 20" wheel'd bike, the brake surfaces are moving
>> past each other 35% faster, thereby producing 35% more friction at a
>> given brake lever force. I think that explains it (though much
>> simplified, and I'm sure minus a number of fascinating details that a
>> brake expert would add).
>
> It would be better to think in terms of torque
> and force, because braking is a force, not
> dependent on shoe velocity; you get roughly the
> same braking force when applying the lever at
> 20 mph and 10 mph.
Braking is also a power-- the rate at which kinetic energy of the bike
is converted into heat.
To decelerate two bikes (of the same mass etc., but one of which has
smaller wheels) at the same rate must take the same power.
Power is force * speed where speed is the relative speed of drum and
shoe.
The larger wheeled bike has more force at the drum, but less speed
there, so power works out the same.
But for sudden brake locking experiments, rather than prolonged braking,
force rather than power is more likely to be relevant, and so it's the
higher force at the tyre for given braking effort that we reckon makes
it easier to lock the wheel if it's small.
David L. Johnson
> Braking is also a power-- the rate at which kinetic energy of the bike
> is converted into heat.
>
> To decelerate two bikes (of the same mass etc., but one of which has
> smaller wheels) at the same rate must take the same power.
>
> Power is force * speed where speed is the relative speed of drum and
> shoe.
>
> The larger wheeled bike has more force at the drum, but less speed
> there, so power works out the same.
Good point, but I doubt that the efficiency of the brake in converting
the kinetic energy to heat is linear with respect to velocity.
--
David L. Johnson
"Business!" cried the Ghost. "Mankind was my business. The common
welfare was my business; charity, mercy, forbearance, and
benevolence, were, all, my business. The dealings of my trade were but
a drop of water in the comprehensive ocean of my business!" --Dickens,
carl...@comcast.net
wrote:
[snip]
>>Meanwhile, this is as good a spot as any to announce that I saw what
>>may be the first turkey vultures of spring, circling in the late
>>afternoon sun and being harried by what turned out to be a pair of
>>crows.
>
>Niiiice. I was recently visiting my son and his family in East Texas,
>and was out for a morning ride on my daughter-in-law's MTB through a
>local preserve by a lake. As I came around a bend in the trail, a
>pair of bald eagles swooped out of a tree, down the trail in front of
>me. What amazed me most was the SIZE of the larger of the two, and
>the noise generated by their (huge) wings. Sadly, no camera (and even
>if I had one, I'm sure I would have still missed the shot due to an
>overdose of awe).
>
>Mark Hickey
>Habanero Cycles
>http://www.habcycles.com
>Home of the $795 ti frame
Dear Mark,
Yesterday, the turkey vulture decided to roost on the sunny side of
the blue spruce, making it possible for an incompetent photographer to
capture its red head and white beak:
http://i15.tinypic.com/42n3dpx.jpg
Notice that the bird is obviously peering down at me.
It's rather annoying to sneak around in a stealthy fashion, trying to
avoid disturbing animals, only to find that they're using their
superior eyesight to watch you every step of the way.
Not long ago, I was walking along the tops of the bluffs above the
Arkansas River with my camera turned on and my orange watch cap
stuffed into a pocket to avoid detection, looking down at the river
bottom for a fox.
No fox was visible.
There was an odd bush, however, in a clearing near a small grove of
saplings where I think the fox has a den. I stared at it for a while,
thinking that it might be a fox, but that was just wishful thinking.
What the hell, I took a picture, just so I could see the details
later.
Here's the full-size picture. It's fuzzy, but the odd bush is pretty
much dead-center if you draw diagonals from the corners:
http://i15.tinypic.com/29zsbux.jpg
Here's a cropped view of the bush, in the middle about 20% up from the
bottom:
http://i17.tinypic.com/2mez32u.jpg
You can see why I didn't waste more time on that indistinct bush.
A little further along the top of the bluff, I happened to look down
again.
The bush, which had been sitting still and watching me, was now
walking to my right, toward its den, showing its pale, bottle-brush
tail.
Large picture, left-click in lower right in Explorer for full-size,
bush again dead center:
http://i17.tinypic.com/33lds09.jpg
Cropped view of bush walking to the right:
http://i15.tinypic.com/2ik9y09.jpg
Then the bush turned its head to stare at me. You can see the black
tips of its ears:
Large view, again dead center:
http://i15.tinypic.com/2q9jja0.jpg
Cropped view of bush's black ear-tips:
http://i16.tinypic.com/2wmnihy.jpg
Like the turkey vulture, the bush had been watching me all the time,
easily spotting me 250 yards away.
Cheers,
Carl Fogel
rcou...@gmail.com
> -snip-
>
>
>
> Ryan Cousineau wrote:
> > Well, you can't help me avoid trouble now that I've bought the bike!
> > It turns out it was...a 20"-wheeled folding(ish) tandem!
> >http://flickr.com/photos/rcousine/413380853/in/photostream/
> >http://flickr.com/photos/rcousine/413380855/in/photostream/
> > Here's the head badge ("G") and frame sticker.
> >http://flickr.com/photos/rcousine/413380857/in/photostream/
> >http://flickr.com/photos/rcousine/413380859/in/photostream/
> > Sorry about the taken-in-haste (repent at leisure) photos.
> > There's another badge that is all but obliterated, except for some faint
> > traces of the Italian tricolour. The notorious "BREVETTATA" badges were
> > just under the seatpost clamps on both seat tubes.
> > Cottered cranks, Aprilia (!) lighting system driven by a sidewall
> > generator,Carnielli(?) saddles. The strange hanging dropouts seem to
> > have a "C" cut into them (the second photo shows the mirror-image one on
> > the left side)
> > The frame has a proper split-shell eccentric front BB, and all the
> > frame's folding points (seatposts, hinge, bars, stem) have 8mm hex bolts
> > in them.
> > The brakes are Sturmey-Archer drums front and rear. The rear is an AB
> > (cable-operated drum) 3-speed hub stamped "70", which should be the
> > production year. Hub seems in good order, but only one gear is available
> > right now. That's the first order of business.
> > The shifter is mounted on the stoker's seatpost.
> > The "keel tube" is a pair of parallel bolted-in tubes about the same
> > diameter as the rear rack/triangle/whatever tubing. The rear "triangle"
> > also appears unboltable, though you'd have to be trying to fit this
> > sucker in a Cinquecento to want to do so, I suspect.
> > It's shopworn, but obviously lightly used. It looks cute and amusingly
> > retro. It should hold up well for around the park. The frame appears to
> > be braced in all the likely failure points, and construction is by
> > indifferent-looking welds.
> > C$220 took the whole thing away.
> > So, what is it?
>
> Most probably made byCarnielli (they made Bottecchia &Graziella
> besides Carniellilabel exercise/child/specialty bikes). These 20-inch
> frame system components were sold to many European manufacturers. You
> can see the similarity to my Bianchi. Gitane, Cazenave, etc, etc were
> built from the same parts with minor detail changes.
>
> http://www.yellowjersey.org/aq.html
> --
> Andrew Muziwww.yellowjersey.org
> Open every day since 1 April, 1971
Coming back to this post rather late, I should say that a kindly
Briton named James dug up some fascinating new information, including
photos of another one of thses tandems!
http://www.bikecult.com/works/collections/grazzitand.html
The bike in question has some interesting detail changes from mine
(notably, the single-sided drivetrain), but the frame is clearly
identical, with all of the tandem-specific bracing in the right shapes
and places.
Most notably to me, this explains why my "Carnielli" would have a big
serif "G" logo on the head tube: it's a Graziella. The font on this
bike's logo is unmistakably the same as the font on my bike's head
tube badge. Well, sticker.
There's also one more detail, which I will describe in 8 hours and 36
minutes.