That Castro is gorgeous, be nice to see some more custom versions.

please explain how the castro is structurally incompetent.

where is the like button ?
I would ride it

North Americans don't understand...
Have a cigar..........

Finally, some one who asks the right question instead of just spouting off irrelevant non-sequiturs!

I have to assume that those of you defending this bad design have never had any mechanical or aeronautical engineering training, so I'll try to keep it simple.

Classic lightweight truss structures consist of triangles (a stable shape) that try to put the sides of the triangle in tension or compression, not bending. This allows the use of "slender" elements in the truss and the lightest truss.

The classic truss also places elements "far apart" at the extreme positions in the truss - say the top and bottom of a bridge truss, like the one shown. This is because the loads put into the truss are carried by the outermost elements and the farther apart these elements are, the lower the stresses in those elements.



The classic bicycle diamond frame is close to having the most efficient triangular shape. The spacing of the top and
front tubes on the head tube causes some bending there (as does the fact that the joints aren't pinned). But that classic
design tries to place the tubes in the main triangle far apart to lower the loads in the main triangle tubes.

The stupid design in question essentially joins 2 triangles at their points. The outer elements in each triangle run down to join at a point. (This is much different that the classic truss with widely spaced top and bottom elements.) So all the bending load on the front of the bike now has to go through that very low height "point" where the triangles join. To take that load, the tubes have to be much, much heavier - and notice the twin tubes. The same load in a classic diamond is taken by tubes that are much, much father apart - so they can be much lighter. The stresses in the diamond tubes could hundreds or even thousands of times less those concentrated in that little point.

That artsy fartsy design (and the Cannondale/Origin 8 Bully I previously complained about) just waste weight in the name of stylin.' Have you ever asked yourself why the lightest road racing frames don't look like this stupid thing and are all the classic diamond?

If you want something different, that's you free choice. But as a mechanical engineer and especially as an aeronautical engineer, I'm apalled at these overweight designs that sacrifice proper lightweight engineering for style. In my mind, Mother Nature is saying Nonononononononononono. The people who put out these bad designs are counting on the public being almost completely technically ignorant.

Really,...you DO KNOW what they say about people who "ass-u-me", don't you? Do all British have "bad teeth"?

Is not the strongest way of connecting two wheels together a stiffer narrower truss rather than two larger tiangles. If the rider doesn't need to sit down. Hence the design of motor trials bikes, bicycle trials bikes and some BMX racing bikes that are designed for standing riders.

So arguably some of these none large triangle or space frame designs are stronger when standing?

I think you miss the veiled Fidel Castro quip.

Le sigh,..

Or do You think about 'the Castro' street in San Francisco? Castro District San Francisco, Castro guide, gay and lesbian news MyCastro SF

I agree with what Flyboy2160 is saying about triangulation, but at the same time I do like the Castro because it looks cool.
The classic Moulton F frames seem to be a strong design although it doesn't look it.
I much prefer the Moulton spaceframes though since they look frail but are proven very strong.

I used to hang in the road forum until I was mocked for asking why road bikes don't have thru axles (many do now).
So those clowns may be the technically incompetent people the Castro will win over.

Unless carrying a bike often or checking it as luggage; I am more relaxed aboout trying to weight weenie my bikes.
I have a 6kg Dahon Dove but much prefer riding a 18kg fatbike.

How pompous can one person get? The fact is that bike frames don't have to be triangulated... that has been proven by bikes like Bike Fridays, Bromptons, Schwinn Twenties/Shoppers (and their ilk), Moultons and such that are decades old. You can argue as much as you want but the frames just plain work and reliably so.

Copenhagen (version of) Dursley Pedersen is another truss triangulated frame design ..
https://www.google.com/search?q=Cope...MAHbTMsuc6M%3A

I saw one built where all the tubes, But the chainstays, Bolted to the BB shell, so they all could come apart for compact travel .. https://www.dursley-pedersen.net/imag...copenhagen.png

& 1 had 20" wheels to further ease the smaller Packed size

Ugh,...

All right, now we're doubling up on logical fallacies: both ad hominem and non-sequitur!

I never said all frames have to be triangulated. just that it's the most weight and stiffness efficient design.

If a designer wants to choose to emphasize something else, that's a free choice. Do you really think I don't know about the single top tube designs? Their designers have chosen that most likely for cost and simplicity over weight - a valid decision. The bikes with the fold in the top tube would have a more complicated fold mechanism alignment issue if the fold line extended down to a second pivot in a lower front tube.

Here's a cross section of one of the failed Tern frames.

Notice the massively thick side walls of the tube and its oval shape. Both are needed because that single tube is taking all the bending load. In a diamond frame that load is taken by two tubes that are more widely spaced. The stresses in those tubes vary inversely with a power relationship to the distance apart. That's why the diamond frames have smaller tubes with much thinner walls and are thus lighter.

Here's a Tyrell that's fully triangulated instead of the Castro open X:



Unlike the Castro, the bending load in the main triangle is not concentrated where the two top tubes cross. It's spread out over the cross section that runs down to the lower tube. Because of the power relationship to stresses, this makes the Tyrell much, much stronger and stiffer than the Castro.

Although I'd prefer a custom steel butted diamond framed folder, I made a cost decision to go with a heavy single top tube folder that met all my other requirements.

But the Castro is just an incompetently designed mess intended to look "kool." They had the tubes and the space to make a diamond, but instead chose an open X design. I've never, ever seen an open X used as a piece of real structure and you haven't defended it from an engineering point of view - you ducked the issue. And it's not me being pompous, it's Mother Nature saying so. I'll say to you what an aerospace colleague of mine once said about know-nothing managers making technically incompetent decisions: you may choose to ignore the laws of physics, but the laws of physics never ignore you. Enjoy your ignorance.

Yup, fully triangulated - reminds me of the new Fubiefixie


My worry with those is the inevitable play in all those joints making stiffness a problem, especially laterally.

I have just one fold joint in my old Downtube frame, but just a little slop in it was enough to make me fix the joint with an interference fit spring pin:

Except: Mr Pedersen did his bikes before 1900.. the design has been proven for over 115 years..

I always liked Java bikes. They sell a few different folders and minivelos with disc brakes that are good value.
I found a new top end mini with aero features, the Freccia, wish it had discs though.
The graphics are crazy but otherwise not a bad value when compared to other carbon road bikes.
Saw it on ebay too but that link may expire.
JAVA Freccia 451 Carbon Mini Velo Bike 20? 1 1/8? Minivelo Bicycle With Sram APEX 20s | Racing Bikes

No one is disputing physics or the most efficient design based on various requirements. What I was disputing was your arrogant, boorish and patronizing remarks about a bike frame (as well as towards people who like it) that you deemed "structurally incompetent arts-fartsy things" that can only be appreciated by those "who don't know anything about structural design and analysis" when frames such as the one in question are sound in execution. Keep blabbing but it won't change the fact that the simple frames that you don't like do actually work in the real world.

On one hand, you never said that all frames have to be triangulated, that a designer is certainly free to choose something else, that you know about single top tube designs, that their designers most likely chose the design for valid reasons, and that such a design is a valid design decision.

Then you call the Castro an incompetently designed mess for what is basically a braced single top tube design. Do you know of Castro bikes which have failed? Why do you assume that the tubing diameter and thickness do not conform with best engineering practice, where single top tube design is concerned? And if you don't know the spec for the tubing, why do you assume that the builder is ignoring the laws of physics?

that's absolutely mental. reminds me of this article: AngryAsian: Enough with the logos already - BikeRadar

A retailer in Singapore I keep in touch with its selling these. They are carbon and 8kg, and sell for about $2,000. Here's the sample image he sent me. Anyone interested let me know and i can tell you what the retailer is. I am not crazy about the integrated caliper brakes, the garish colors and stickers, and that it is carbon.

Yet another reason I have never cared for single tube folders, and much prefer the Dahon Dashes, and Tyrells of the folding world. Aesthetically and structurally a superior design...

And often twin top tubed designs dont fold very well.
There is a reason for "inferior designs". Compromise.

Great job smallwheeler. Best thread ever due to your efforts showing the rarer stuff out there.

Hah,they took a page out of Giant's book. I've lost count of the number of 'Giants' on my Defy,but at least the dark paint scheme hides most of them. Otherwise,that Java is a sweet ride at a decent price.