Duragrouch

My comment was in regard to someone mentioning the Dahon Mini 349 (16"), I looked at it online, and it (bifold) doesn't fold nearly as small as a Brompton/349 trifold, probably not as long as a 20" bifold, but closer to that in package length than a 349 trifold, so I was thinking, what's the point? I felt that trifold small is THE reason for going 349, otherwise, 20" has better ride and gearing. Someone on here disputed that, they have a 349 bifold like the Mini, and tout the advantages of it, despite it not folding as small.

Winfried

I'm indeed worried that those lighter alu blocks might not be as stable sideways with a fully loaded Brompton touring bag.

I guess I'll just file down Brompton's for extra contact with a DIY connector — which, if it fits, I might make out of wood and as a single piece, held against the steering tube with a pair of U bolts.

Schwinnsta

The weak point on the block is the top screw. It gets the highest load, being in tension. The likely scenario is it breaks, or it pulls out and strips out the thread from its attachment point. That said, it is way over designed. As you increase the load to say 30 pounds, the ride and stability of the bike are effected. I have not seen any issues for side loading or the alloy blocks or the Brompton block. The nice thing about the Brompton plastic block is that by filing it down (sanding it down on a belt sander), I changed the angle of the block to suit the geometry of the Swift handlebar. Otherwise, there might have been issues with the tall bags hitting the upper part of the stem or handlebar.

Duragrouch

Your reasoning is sound. Good to know. I'm not really a fan of the front block due to the short bolt span and long load cantilever, unless very low weight; I have a front rack with panniers and I think it's more sound to put loads on the top platform of the rack. That said, I do like that the front block load is not steered mass, if you're going for nimble steering.

Ron Damon

The ultimate question is not whether the plastic material block is stronger, sturdier than the Al-alloy alternatives. It's a good question, but not the one that matters in the final analysis. The ultimate question is whether the Al-alloy front blocks are strong, sturdy enough. I don't have a data-based answer to that question, but at least I have identified the right question. You are an engineer, are you not?

50PlusCycling

I recently bought a new Cospaii Brompton Clone, which are assembled in Japan. I've had a few Bromptons over the years, and I am impressed with the quality of this bike. It is fitted with an external 5 speed driveline using trigger shifters, the weight is 11kg, and I find it rides perfectly well. The price was $650 USD.

Duragrouch

Oh no, I totally understood the point you were trying to make; It's not a question of material, but contact of the piece over a wider lateral span, to prevent over-stressing the block attachment at the headstock, imparting lateral bending moment to a fairly narrow piece, whereas, with wider contact with the head tube, lateral forces will translate more into pure tensile loads on the block, so you're not pulling on just one side of the block, trying to peel it off, but distributing that tensile load over the entire block attachment (brazed or welded), and not having fully-reversing bending loads, bad for fatigue strength. Sorry for the run-on sentence. Yeah, I saw what you were talking about right away, I hit the like button, and tried to acknowledge that.

Yes, I'm a retired engineer.

Duragrouch

Gosh that looks like a good deal. Looking as close as I can, I'm guessing welded chrome-moly steel rather than brazing, same as my Dahon. Can you tell me the tooth count for the chainring, and lowest and highest cog? I'd like to calculate the gear range. Thanks.

I don't see the bike on Amazon, nor a general online search; Where did you buy it?

Jipe

This is exactly my point, its not about material but the shape of the block and especially the width and the contact of the block against the bike head tube provided by this width.

But the material used by Brompton is also needed because the little elasticity of the industrial plastic used to build the block compensate for the frame building tolerances to warranty that the block come perfectly against the head tube. Aluminum that has almost no elasticity would not fit.

Several people think that Brompton choose this plastic to lower the costs, that aluminum would be better, but this not true, plastic was chosen for engineering reasons, not cost (same for the chain tensionner arm).

BTW, the choice of brazing instead of welding is also for engineering reasons.

Duragrouch

Again, I agree. My guess is the plastic is 6/6 nylon, quite common. Generally, I prefer delrin, it machines lovely and I think may be stiffer and higher strength, can't recall, and can't find easy info online about it now without a download, but that also may be too stiff for the application, as you said, you need some flex.

Brazing: I'm not super knowledgeable in that area, but my perception has been, that is done so you don't heat the tubes hot enough to have a heat-affected-zone, as with a weld. Thus, steel tube frames were often brazed into lugs. I also know from reading years ago, that Schwinn fillet-brazed frames (back in the day, the majority of their product and actually on the cheaper bikes) were immensely strong, you could drop it from great height and the brazed joints would not break.

Having said that, so far the (superb looking) welds on my 4130 Dahon have held up fine, and it's a more economical process (but more difficult with thin-wall tubes). Surlys are famously tough, and as I recall, use a welded 4130 chrome-moly frame. 4130 is described as an "exceptional (good) welding steel". The amount of chrome and moly is not that much, not enough to air-harden like stainless, usually hardened by quench and tempering, so not sure if a cr-mo frame needs to be post-weld heat treated to restore strength in the heat-affected zone. "Is there a metallurgist in the house?"

Winfried

Thanks for the info. Even when fully filled when touring, the T-Bag is around 8kg so I'm good. Besides, a heavier bag means more wobble.

I'll get both blocks and experiment.

freckles

NICE BIKE!

Its made in Japan?!?!

Did you get in Japan while in Japan or have it shipped**********

Duragrouch

I'm also curious, if frame made in Japan, or made in China and just assembled in Japan? Either way, I'm interested, but cannot find any trace of this bike online, where it can be purchased, or just mentioned at all. Do tell. Thanks.

Bleu

. Nope not fillet brazed. Schwinn developed a dip-brazed process which uses tubes that are punch-formed to create something of a lug before being heated and dipped into a vat of molten bronze/brass(not sure of the exact alloy) . Very quick process and cheap because of it, and strong as hell.

mlau

Any links for that Cospaii?
I love the fold and utility of the Brompton, but it's expensive and heavy.

Duragrouch

Really(?!) So the dip-brazing just conformed to the joint and formed a fillet naturally? I could see that as possible, different liquids naturally form convex or concave shapes due to surface tension and other factors. I just recall the joints being very smoothly blended, I didn't see shapes like that until I bought my Cannondale, which had large aluminum welds that were post-dressed with handheld power strip-belt sanders, no undercut, real craftsmanship.

edwong3

Not sure if you are still looking for a Brompton clone but this Mint Bob Six seems to be available for shipping to most anywhere. It's listed on eBay.

New MINT BOB SIX Folding Bike | Light Weight 10.5 Kg.| 6 Speeds | eBay

With shipping it comes out to $980 but don't know about any customs/import charges if any. Seems like a C-Line equivalent with six external gears and weighs about the same as my Zizzo Liberte at 10.5 kgs. or 23.1 lbs.

Edward

Jipe

Price $690, shipment costs $290 = 42% of the bike price lost for shipment!

Schwinnsta

Are you sure you're not talking about elecro-forged? That is actually welded, not brazed. Their 70s 10 speeds like Varsity work like that. Smooth joints but heavy steel.

edwong3

I don't know if I would use the word "lost" as far as the shipping costs, but sending something like a bicycle from Asia is not cheap. Just keep in mind that a genuine C-Line Brompton Explore can sell for anywhere between $1,750 to $1,950 USD and if you get any of the "limited" or "special" editions, you can add a few hundred extra. In your first post, you did quote some prices that exceeded $1,200 for a clone so it's entirely up to you to figure it out.

Good luck and I hope you find what you are looking for.

Edward

freckles

YES! I saw the ebay listing after posting here- Though red is not my preferred color, its definitely a contender! Its seems like Mint is a Thai brand? Most of the youtube reviews seem to be in Thai.

I've also seen listings on Alibaba- 3sixty, MInt and a couple other brands which has option to order a single sample. Included shipping costs plus single sample order, the total price is still attractive.

Do you have any idea if the sellers on Alibaba listing 3sixty, MInt and others are clones of the clones??? I can't tell if they are actually making those brands in their factory...

Schwinnsta

Oh, is that a thing? People who can't afford Bromptons but want them anyway, buy the clones. And people who can't afford the clones buy the clones of the clones.

freckles

I think the owner of the Cospaii lives in Japan. I clicked on their handle and saw JP there, assuming that stands for Japan. Trifold bikes seem to be very popular in SE Asia and Asia, they have so many options!

Found this online:
https://store.shopping.yahoo.co.jp/cospaii/fbmhsb.html

I wish we could buy it here in the US...

freckles

No idea!
I just had a paranoid thought after seeing listings on Aliexpress and Alibaba of the same bikes (3sixty, Mint plus other brands) being sold by different "stores".

I don't know if they're actually making the bikes or are reselling.

Pricing a single sample plus shipping from Alibaba seems like a good deal, if they are real clones vs counterfeit clones...

Fake clones? Is that a thing?

Schwinnsta

A fake would be if they took a clone and put Brompton decals on it, otherwise it is a copy they or clone. They may or may not be infringing on copyrights. In some countries, the laws on it may differ.