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Old 04-24-19, 01:06 AM
Bonzo Banana
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Originally Posted by tcs View Post
Here's a cross-section of a turbine blade superimposed on a Dahon Curl image:

Why is the Curl designed this way? Well, form follows function, and it achieves a notably smaller fold:

BTW, in a detail of this image, you can compare the smooth welds of the Dahon with the lumpy braze work on the Brompton:

From an engineering viewpoint there is no benefit to smooth welds it is cosmetic value only. I guess it depends on how it is done, ground off, sanded off, filled or a secondary weld it's extra money spent for no real advantage. Cannondale charge maybe 30% more sometimes than competing brands that have same spec bikes made in the same factory like fuji-ta, they disguise the aluminium used with made up names and on first look you could think it was a carbon frame bike because of the smooth welds. It's basically a extra process in order to inflate the retail price in my opinion and I have seen on a forum a thread about a Cannondale cracking at the smooth weld, that doesn't mean anything in itself without more data and statistics but Brompton vs Dahon are two completely different approaches to bicycles. I've seen a low end Dahon bike in a retail store with a very messy welded frame, it may not have effected it's strength in fact it could be a very strong frame but visually it looked very poor. The factory used for that frame could be completely different from the factory used for the Curl. If Dahon continues with the Curl design the manufacturer of that frame could change and standard welds re-appear, I don't think that should be seen as a downgrade or upgrade in itself.

I think there has been a trend away from the classic double triangle frame design which is very strong and rigid to shorter life aluminium frames which resemble carbon frames and are actually weaker than older frame designs, typically the seatstays instead of being at the same height as the top tube are now further down welded lower on the seat tube. This gives a softer ride but adds much more fatigue as the seat stays flex more as they are welded to a more flexing area of the seat tube. Some of these modern bikes have lower weight limits and shorter frame warranties and are what are called stylised designs, inferior engineering for cosmetic reasons and commercial advantage. Smooth welds is part of that approach. Brompton are already making their life difficult by manufacturing in the UK there is no money to spend on smooth welds and un-necessary cosmetic improvements.
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