Raxel

Standard steel Brompton uses dirt cheap non-butted high tensile steel (Not even the 4130 cro-mo alloy other folding bike uses).
3-2.5 titanium alloy actually has HIGHER tensile strength than Hi-Ten 1020 steel so 40% lighter titanium frame should be actually STRONGER than steel Brompton frame.
And that's why Brompton titanium fork and rear triangles are approximately 40% lighter than steel counterparts.

That's simply not true. The lightest XCR/953 road frame still weighs around 1.3kg (custom Rob English frame).
The lightest MASS PRODUCED titanium road frame (litespeed ghisallo) was lighter than 800gram. HUGE difference.

Raxel

There are Chinese Brompton knockoff frame made of better material (4130 cro-mo). They are roughly 100 gram lighter, and half the price of the original frame.

And no, Brompton will never use top quality steel for their bike. XCR or 953 frames are actually more expensive than most titanium frames.

Winfried

So why does Brompton stick to hi-ten instead of moving to 4130 cro-mo?

Margins?

tcs

I read once on the internet (and if you read it on the internet, it must be true) that Andrew Ritchie couldn't bend the mainframe arch in cro-mo with his hand bender and switched to hi-ten. I'm suspect of that tale, but even if so that was 35+ years ago, and I too have wondered why Bromptons hasn't moved to higher grade steel...and for that matter, forged F&R dropouts.

It may be that at the tube wall thickness that meets a design spec dent resistance criteria there's no weight advantage in using higher-grade steel. I'm suspicious of this explanation, too, but it's possible.

tcs

Somewhere between a review and marketing copy :

https://www.rouleur.cc/blogs/desire-...st-look-review

Jipe

Weight is not all, yes its possible to make it lighter but then the frame isn't rigid enough, it become too soft.

Joe Remi

I suspect a lot of it has to do with they sell every bike they make that way. Harley-Davidson used to be like this in motorcycles, too, they sold the same basic design for decades and couldn't keep models on the showroom floor. That market finally failed but Brompton is a long way from a similar fate.

monsterfather

Just like to learn from here, is the Brompton bike folding design registered? Some local guys in Hong Kong said the registered design will soon expire (but they simply forget renewal), so there will be many clones at much cheaper prices coming (well there are already!) …

CEBEP

I believe you meant patent? Patent did already expire and there are already lots of Brompton clones available.

monsterfather

i see… but why Brompton not renew their patent (or cannot do so?)

CEBEP

As far as I know they just expire and can't be renewed unlike brand name registration. There are also different rights like copyright rights and that's a different thing as well
​​​​

tcs

Andrew Ritchie's first folding bike patents date from the mid-1970s, and the final form of the basic design appears in patents in the early 1980s. IIRC British and USA patents at the time ran for 17~19 years from the date they were granted.

Patents are an incentive to folks to invent useful items/processes. There has been a good deal of international cooperation in patent law. These days most countries recognize patents, once granted, running for a period of 17 years from the time of application. Patents cannot be extended or renewed. If a further improvement is made, that improvement can be patented, but that does not extend the patent on the base invention.

There are other kinds of intellectual property that are protected (or not) in different ways. Compositions (text, music, computer software & etc.) and art are generally covered under Copyright. Names, slogans and logos are generally covered under Trademarks. There is much less international harmonization in Copyright and Trademark law, and what is Copyrighted or Trademarked in one country might not be - and probably isn't - copyrighted or trademarked in another.

Bromptons to my knowledge have made three attempts to exclude other Andrew Ritchie design tri-folders from the lucrative European market. The first was some two decades ago when some design copies were offered for sale in the EU. The manufacturer/importer made no effort to distinguish their bikes from Bromptons. IIRC they used identical graphics. Patent protection had expired, so Brompton sued under EU copyright law, pointing out that even the owner's manual was just a copy of the Brompton owner's manual. Brompton won this case.

In 2017 Dahon introduced the Curl at the Eurobike trade show. Brompton filed for an injunction based on...well, I'm not really sure what. At the first court hearing, Dahon pointed out the patent protections had long since run out, a blind man could see the difference in appearance between the machines and the EU had granted Dahon 11 patents on the novelty of the Curl design. Brompton's request for an injunction was dismissed and the company was ordered to pay Dahon's legal expenses.

In 2019 the carbon fiber Chedech bike was offered in the EU. Brompton filed suit claiming copyright infringement, specifically saying the Chedech had the same mainframe silhouette as the Brompton had since the 1988 production run started. The question became: could the appearance of an industrial design be protected under copyright? An upper-level court ruled that under EU law: yes, IF (1) the design was unique, (2) it was an artistic expression by the designer, and (3) another shape could perform the same function. I'm not aware that the lower EU court has returned to make a ruling on Brompton's specific lawsuit.

In the United States the appearance of an industrial design can be separately protected apart from function by something called a Design Patent. (Function is of course covered by a regular patent.) (Brompton does not have a US Design Patent.) I understand in most jurisdictions around the world the appearance of an industrial design cannot be protected.

monsterfather

My sincere thanks for sharing these details here. Learnt a lot!