tcs

Here is the description in 'Patent Application English':

https://patents.google.com/patent/CN...assignee=dahon

Here are the patent drawings annotated in Chinese:

https://patentimages.storage.googlea...204021155U.pdf

curl fork.jpg

chagzuki

Aha! I was right in my suspicions! This is a tremendous improvement; I've long thought that all folders should follow this sort of design. It makes no sense for the steerer to be part of the fork when the area which requires maximal stiffness is the elongated stem. This is the weakest area of the Brompton; their 'upgrade' to the M handlebar this year won't make any difference to stiffness when the majority of the flex originates at the stem/steerer interface, which in Brompton's case is prehistoric.

chagzuki

Furthermore any flex in the interface will translate to the fork providing a very minor suspension effect.

jur

Good guessing chagzuki.

Thor, I'd like to know if the main frame latch has had fundamental design changes since the mega-dodgy stem version that was recalled. Specifically, the bolts that hold the sliding latch plate, are they shoulder bolts? Or positively retained some other way?

cplager

Nice video.

Next time turn the phone 90 degrees.

tds101 

Actually, if you watch it on a mobile device, when in portrait the video IS full screen! LOL!!!

cplager

Yeah, dude. That's kind of the point. Neither computer screens nor TVs turn very easily. If your audience is teenagers, then by all means keep filming like that.

tds101 

Actually, dude, adults use TABLETS and CELLPHONES to watch videos all the time. All the people I know use them,...and quite a few are in their late 60's to boot. Computers are no longer the main form of media consumption.

bhkyte

Basically this is same as a mezzo fork.

bhkyte

Unless it is a square screen blackberry Q series or passport.......

chagzuki

I thought I remembered someone mentioning that Birdy uses a system of this sort but I couldn't find any pics on the net, perhaps I was getting confused with Mezzo. I'd assumed that since a Mezzo uses a regular ahead stem (or so it appears from the pics I've seen) the steerer must be conventional.

tds101 

Which is still fine by me!!!

At least @ThorUSA went through the trouble to create the video. I thank him for that.

tcs

Is it?

mezzo.jpg

We see in this picture that the Mezzo stem is clearly clamped to the steerer above an Aheadset. I don't see any steerer clamping mechanism at the fork crown. This would indicate to me that the steerer is one with the fork crown. On the Curl, the steerer is one with the stem, and the fork crown is clamped to it.

dahon curl.jpg

dahoneezz

Why do you require maximal stiffness in the stem?

chagzuki

I guess there's no justification for it beyond that it provides a kind of accurate tactile feedback that inspires confidence... I'm not knowledgeable enough to talk about 'power transfer'. If I'm riding casually on the Brompton it's fine but if I'm climbing a hill it feels like a bendy-bike, and for me that's not a good thing.

bhkyte

Not sure how you are differentiating the mezzo fork from the curl. Yes the steerer is connected to the fork. But the fork blades are separate from the steerer and clamped in to the steerer.
Big difference?
Certainly no flex in mezzo forks.

chagzuki

With the Curl the forks are clamped because it's a convenient way for the whole fork to clamp onto a steerer which is rigidly connected to the stem, this is paradigmatically different.

dahoneezz

Maybe its the U Brompton handlebar. Is aluminium no? Softer than steel?

tcs

The Curl fork design might be because Dahon's R&D said it's stiffer or stronger or more secure or less expensive to manufacture or maybe takes 3.6 seconds less time to assemble. But I'm of the opinion that the Curl fork is designed the way it is mostly to minimize the folded envelope.

curled up.jpg

(I also note in this shot they've corralled the floppy cables by tucking them under a brake lever.)

chagzuki

I use an S stem plus riser bar. The flex comes from the main frame hinge and crappy wedge stem. A wedge stem is basically a pivot(!).

George3

But a special front bag may be very expensive, like the Brompton front bags. So I definitely prefer a luggage rack over the rear wheel. On that you can strap a large backpack of your own choice. And if you need to carry the bike on a staircase, you can carry the backpack on your back. And also if you would park the bike and proceed on foot.

Winfried

Personally, I prefer having a bag in the front:

• It avoid adding yet more weight on the rear wheel
• I can easily grab something out of the bag, and also keep an eye on it

A sorry decision from Dahon, especially considering most of its bikes also have a bag lug in the front.

George3

The option for a front bag or front rack is adventagious, but is probably limited to about 27 litres (30 x 30 x 30 cm, or 1 x 1 x 1 ft) of luggage.

While on a luggage rack above the rear wheel you can strap a 120 litre backpack, or a 300 litre box, if they are not too heavy, without limiting the steering too much. 120 litre is the largest backpack you can buy. For people who have no car, or who go on holiday without a car, that option can be very important. That way a folding bike can also be used as a luggage trolley or shopping trolley for a pedestrian.

George3

Aluminum is softer than steel, but it should be applied thicker than steel, to make up for that.

reppans

Yup, Brompton's quick release bag in front is a MAJOR reason it's my preferred touring rig.
- best handling with weight carried on front
- doesn't preclude additional luggage on the rear rack, although front is always my 1st choice
- you can fold the Brompton with front luggage still attached
- the B will carry your luggage in shopping cart mode and I've pushed my rig like a baby stroller, incl. camping gear, for many hours/miles while sightseeing in places I wouldn't risk locking up (clicky).
- It's easy rig single shoulder straps into dual backpack straps. While touring, I often carry my T-Bag as a backpack for rough riding sections, through public transport, and ~1/4 mile in/out of the woods when hiking my entire rig to/from wild camping spots.

Unfortunately, it looks like the Curl's fold design (handlebar stem folds against front of head tube?) does preclude a protruding front mounting block... also doesn't seem like it would be able to carry/wheel your luggage like the B due to the main tube hump.

I also wonder how the Curl will ride without the suspension. When I first got my Brompton, I had a firm suspension block installed (just cuz everyone recommended it), but it was too brutal for me. Put the standard block back on and it rides as nicely as my 700x32 gravel bike - I can tip comfort toward either bike just by air pressure.