Wanted Brompnot- aka Brompton clone
#51
Senior Member
No that's correct, if a manufacturer designed a folding bike around 16" wheels that inexplicably folded no smaller than a folding bike designed around 20" wheels, the 20" bike would have ride and gearing advantages. Is this just a theoretical musing, or do you have a particular 16" model in mind that folds in no smaller envelope than a similar folding 20"er?
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#52
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For technical reasons I do not recommend these aluminum blocks! The Brompton block in industrial plastic is much wider than the threaded rod brazed on the bike head tube and its material has some elasticity. When it is attached on the bike, its sides are pressed against the bike head tube what provides an excellent lateral stability. The aluminum block are narrow and only hold on the brazed rod they do not touch the bike head tube at all, their lateral stability rely only on the two bolds and their thin sides. They are definitely not good for heavy load or wide bags (some brands are honest and specify a max load lower than the 10kg allowed by the Brompton block).
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.
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#53
Schwinnasaur
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.
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#54
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For technical reasons I do not recommend these aluminum blocks!
The Brompton block in industrial plastic is much wider than the threaded rod brazed on the bike head tube and its material has some elasticity.
When it is attached on the bike, its sides are pressed against the bike head tube what provides an excellent lateral stability.
The aluminum block are narrow and only hold on the brazed rod they do not touch the bike head tube at all, their lateral stability rely only on the two bolds and their thin sides.
They are definitely not good for heavy load or wide bags (some brands are honest and specify a max load lower than the 10kg allowed by the Brompton block).
The Brompton block in industrial plastic is much wider than the threaded rod brazed on the bike head tube and its material has some elasticity.
When it is attached on the bike, its sides are pressed against the bike head tube what provides an excellent lateral stability.
The aluminum block are narrow and only hold on the brazed rod they do not touch the bike head tube at all, their lateral stability rely only on the two bolds and their thin sides.
They are definitely not good for heavy load or wide bags (some brands are honest and specify a max load lower than the 10kg allowed by the Brompton block).
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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.
Last edited by Ron Damon; 02-02-24 at 06:27 PM.
#56
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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.
#57
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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?
Yes, I'm a retired engineer.
Last edited by Duragrouch; 02-02-24 at 08:22 PM.
#58
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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.
I don't see the bike on Amazon, nor a general online search; Where did you buy it?
Last edited by Duragrouch; 02-02-24 at 08:30 PM.
#59
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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.
Yes, I'm a retired engineer.
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.
Last edited by Jipe; 02-03-24 at 01:45 AM.
#60
Senior Member
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.
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.
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?"
#61
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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.
I'll get both blocks and experiment.
#62
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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.
Its made in Japan?!?!
Did you get in Japan while in Japan or have it shipped**********
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#63
Senior Member
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.
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#64
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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?"
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?"
#65
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#66
Senior Member
. 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.
#67
Senior Member
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
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
I'm looking for a Brompnot trifold bike with external gears, open to anything w/ 3-6 (flexible), preferably a lighter weight P line variant for multi modal city use.
I like the Aceoffix P1 and Mobot but they don't ship to the US so I'm left w/Aliexpress.
So far I've found-
Aceoffix Ace01- 3/5 gear option, no rear rack/fenders/pig nose, $871+ $300= $1171
https://www.aliexpress.us/item/32568...Cquery_from%3A
Mint Bob- 6 external gears, P line wheelset/jockey, has fender/pig nose, no rear rack, $871= $250= $1121
https://www.aliexpress.us/item/32568...Cquery_from%3A
3Sixty- 3 external gears, old style, heavier, small rear rack/fender/pig nose, $443+ $300=$743
https://www.aliexpress.us/item/32568...Cquery_from%3A
Frescoche- 6 external gears, P line wheelset/jockey, has fender/rear rack/pig nose, $834+ $180= $1014
https://www.aliexpress.us/item/3256806037148638.html?spm=a2g0o.detail.pcDetailBottomMoreOtherSeller.7.41112Ngp2Ngpqb&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.40000.326746.0&scm_id=1007.40000.326746.0&scm-url=1007.40000.326746.0&pvid=668a8f5a-db39-4d3c-adeb-639022decc94&_t=gps-idcDetailBottomMoreOtherSeller,scm-url:1007.40000.326746.0,pvid:668a8f5a-db39-4d3c-adeb-639022decc94,tpp_buckets:668%232846%238107%2362&pdp_npi=4%40dis%21USD%21888.00%21834.72%21%21%21888. 00%21834.72%21%40210307c317065562973568444eeb9b%2112000036351792320%21rec%21US%21%21AB&utparam-url=scene%3ApcDetailBottomMoreOtherSeller%7Cquery_from%3A
I like the Aceoffix P1 and Mobot but they don't ship to the US so I'm left w/Aliexpress.
So far I've found-
Aceoffix Ace01- 3/5 gear option, no rear rack/fenders/pig nose, $871+ $300= $1171
https://www.aliexpress.us/item/32568...Cquery_from%3A
Mint Bob- 6 external gears, P line wheelset/jockey, has fender/pig nose, no rear rack, $871= $250= $1121
https://www.aliexpress.us/item/32568...Cquery_from%3A
3Sixty- 3 external gears, old style, heavier, small rear rack/fender/pig nose, $443+ $300=$743
https://www.aliexpress.us/item/32568...Cquery_from%3A
Frescoche- 6 external gears, P line wheelset/jockey, has fender/rear rack/pig nose, $834+ $180= $1014
https://www.aliexpress.us/item/3256806037148638.html?spm=a2g0o.detail.pcDetailBottomMoreOtherSeller.7.41112Ngp2Ngpqb&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.40000.326746.0&scm_id=1007.40000.326746.0&scm-url=1007.40000.326746.0&pvid=668a8f5a-db39-4d3c-adeb-639022decc94&_t=gps-idcDetailBottomMoreOtherSeller,scm-url:1007.40000.326746.0,pvid:668a8f5a-db39-4d3c-adeb-639022decc94,tpp_buckets:668%232846%238107%2362&pdp_npi=4%40dis%21USD%21888.00%21834.72%21%21%21888. 00%21834.72%21%40210307c317065562973568444eeb9b%2112000036351792320%21rec%21US%21%21AB&utparam-url=scene%3ApcDetailBottomMoreOtherSeller%7Cquery_from%3A
#68
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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
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
#69
Schwinnasaur
. 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.
#70
Senior Member
Good luck and I hope you find what you are looking for.
Edward
#71
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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
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
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...
#72
Schwinnasaur
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.
#73
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Found this online:
https://store.shopping.yahoo.co.jp/cospaii/fbmhsb.html
I wish we could buy it here in the US...
#74
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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?
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?
#75
Schwinnasaur