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View Poll Results: Dahon Mariner D7 or Tern Link D8?

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  • Dahon definitely

    3 11.54%
  • Tern definitely

    19 73.08%
  • Flip a coin, best two out of three

    4 15.38%
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Thread: Tern or Dahon

  1. #26
    jur
    jur is offline
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    Here are 3 cases reported to www.saferproducts.gov:
    http://www.saferproducts.gov/ViewIncident/1219075
    http://www.saferproducts.gov/ViewIncident/1196874
    http://www.saferproducts.gov/ViewIncident/1177798

    Look at the small amount of material in the actual hinge; if the latch is a bit loose, that transmits all the force exerted on the handlebars while riding, to the frame! With the latch not tightened properly, it snaps easily.

    There are numerous cases that were also reported at the now-defunct Dahon forums. Here's one:
    http://forum.dahon.com/index.php?showtopic=4450&st=0
    Fascinating reading. Note that Josh Hon himself actually advocated superglue for the Delrin block adjustment!! "Sorry boys, we stuffed up the positive retention of the Delrin block screw but superglue will see you right." That never should have happened.

    Most of the "problems" with stems come from overzealous adjustment freaks, who cannot leave good alone and have the urge to optimize beyond their abilities. I have seen delrin blocks explode, due to way overtightened adjustment bolts, they will also show excessive wear , if they are overtightened.... plus they will need more frequent adjustment as well.
    I have seen tightened down guide bolts ( for the plate, who needs to move freely ) making a folding stem a more or less solid one, without been able to fold.... and if than the lips are rounded off...due to not opening jaws for lack of the better word ....
    grinding away with every fold..... people who open the handle just half and force the stem to close ... and and and
    This incomplete list actually very neatly highlights my exact objection against that hinge design - there is a HUGE scope for things to go wrong. The design is not bulletproof, far from it. And worst of all, the screws are not retained positively. For example, those screws you mention that hold the sliding latch plate - they should have been shoulder screws. This is just one item in a list of things that a competent engineer would have done differently.

    No, I am utterly convinced the hinges are failing due to design issues, not over-zealous adjustments or material issues. Don't forget, Dahon had a HUGE loss in store if they didn't fight that conclusion tooth and nail. So money is at the bottom line, and as soon as money is at the bottom line, integrity goes out the window. You can't convince anyone who looks at the evidence with an open mind, that the design is not at fault here. "Ah yeah, mate, some hinges broke due to crappy workers. And yeah, others are breaking due to the owners adjusting the shiite out of the hinges! But it's not my fault mate!"

    My folding bike photo essays www.dekter.net/

  2. #27
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    Jur,

    I can certainly understand your position that a good design is a bulletproof one, and I certainly hope that's the guiding philosophy for all industrial engineers! "Stuff that works without fail" is the loftiest ambition.

    However, that is not what consumers get. Virtually everything we get, or can buy, fails when used, and particularly, if used outside the intended application parameters.

    So, while I hear your assessment of how that Radius hinge could have been designed better, I think it's way overboard to slam the design as incompetent IF ONLY because it does work the vast majority of the time, for the vast majority of users, under the vast majority of conditions. By my standards, an incompetent design would usually fail under normal use, often prematurely, for most users.

    I think that we'd agree that the exceptions are the true measure of a design's success, but perfection under all all conditions, for all users, all the time is an unacheivable standard.

    Could the Radius hinge have been better designed? Of course, yes, and let's presume that's what we have in the Radius v hinge, a better design. That only makes the Radius a comparatively worse design, not a bad one.

    Another condition to consider is whether the "R" stamped hinges, which we'll call the replacement handle posts, are also failing, and what their design specs are compared to the recalled subset of Radius handle posts. It has been, after all, longer that the replacements have been in use than the originals in most cases, so we might expect them to have seen as many, if not more, duty cycles.

    Again, I think it's irresponsible to condemn the Radius design, and particularly without understanding how the R differ from the recalled subset (remember not all Radius's were recalled). Absent that understanding, it also seems illogical to conclude it is a mechanical design fault that lead to those few failures and subsequent recall, because it cannot be ruled out that it was a metallurgical fault or improperly spec'd component.

    Undoubtedly your standards are higher than mine, and I'm glad for that since it appears that engineering and managing engineers is your work; I want the best product I can get at any given price point. Yet even if Dahon had hired you to lead the development of the Radius handle post and all of your design ideas and standards were met, that would not have precluded the possibility of design failures arising from factory production managers taking shortcuts on costs, labor hours, oversight, and standards that result in inferior quality products.

    Without giving offense to the Chinese, have we ruled out that some buyer at Dahon China took a bribe from a raw material supplier who sold him a batch of inferior alloy that lead to weaker than spec'd hinges?

    Have we ruled out that someone at the very top of Dahon was over-driving factories to meet market demands and explicitly ordered the reduction of heat soak time on the locking plate in order to raise production speed?

    Could Dahon have been more transparent about what they determined the source of the failures to be, and put all this speculation to rest?
    Chaad--'95 DeKerf Team SL, '02 Lemond Buenos Aires, '05 Novara Buzz, '73 Schwinn Collegiate, '06 Mountain Cycle Rumble, '09 Dahon Mariner D7, '12 Mercier Nano, '12 Breezer Venturi

  3. #28
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    OMG, I spent WAY more time writing that last post than I should have; this matter of the old Dahon Radius handle post is really not relevant to making a buying decision today.

    What is relevant, perhaps, is knowing that the Tern hinges, with their NorGlide bushings and tighter machining tolerances, will probably deliver a stiffer, quieter, longer, lower maintenance service life than the Dahon hinges, particularly at the margins of the use environment.

    They are not bullet-proof, however, and will still require some maintenance: http://16incheswestofpeoria.wordpres...lding-bicycle/

    Me? I gotta get of the forum now and go to work so that I can earn enough dough to buy myself a Tern Verge X10! *drool*

    Chaad--'95 DeKerf Team SL, '02 Lemond Buenos Aires, '05 Novara Buzz, '73 Schwinn Collegiate, '06 Mountain Cycle Rumble, '09 Dahon Mariner D7, '12 Mercier Nano, '12 Breezer Venturi

  4. #29
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    Thanks for the link to my article on the Tern Link P7i. I found my sample, supplied by Tern for evaluation, to be a rock-solid design. Eliminating the creak from the main frame was a matter of a quick adjustment to the tension. It was the only maintenance I performed on the bike in approximately 300 miles, including a bit of dirt road riding. And this was a pre-production machine: no serial number.
    16incheswestofpeoria.wordpress.com

  5. #30
    jur
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    Quote Originally Posted by chaadster View Post
    So, while I hear your assessment of how that Radius hinge could have been designed better, I think it's way overboard to slam the design as incompetent IF ONLY because it does work the vast majority of the time, for the vast majority of users, under the vast majority of conditions. By my standards, an incompetent design would usually fail under normal use, often prematurely, for most users.

    I think that we'd agree that the exceptions are the true measure of a design's success, but perfection under all all conditions, for all users, all the time is an unacheivable standard.
    Yes, not to wring every last ounce out of this discussion, it needs to be pointed out that the mech is a *safety critical* subassembly, meaning if it fails it has direct impact on the user's safety. There are strict standards about such things. For example, to guard against electrocution, there are enforced rules that insulation must be double, so that even if one level failed, there is a backup level of equal strength.

    For that hinge quite besides the lack of positive screw retention (which is BAD no matter which way you try to cut it), there is absolutely NO backup safety mechanism. One failure and your down and out. And because the hinge is something that gets operated all the time by the user, it should offer the necessary protection - due diligence. It's no use to argue that the Ford Pinto design was OK because out of the many thousands on the road, only a few fuel tanks exploded. I think the level of threat to the user is on the same level - you can get killed quite easily if you lost control of the bike in traffic. Dahon got off very lightly.
    My folding bike photo essays www.dekter.net/

  6. #31
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    Quote Originally Posted by jur View Post
    Yes, not to wring every last ounce out of this discussion, it needs to be pointed out that the mech is a *safety critical* subassembly, meaning if it fails it has direct impact on the user's safety. There are strict standards about such things. For example, to guard against electrocution, there are enforced rules that insulation must be double, so that even if one level failed, there is a backup level of equal strength.

    For that hinge quite besides the lack of positive screw retention (which is BAD no matter which way you try to cut it), there is absolutely NO backup safety mechanism. One failure and your down and out. And because the hinge is something that gets operated all the time by the user, it should offer the necessary protection - due diligence. It's no use to argue that the Ford Pinto design was OK because out of the many thousands on the road, only a few fuel tanks exploded. I think the level of threat to the user is on the same level - you can get killed quite easily if you lost control of the bike in traffic. Dahon got off very lightly.
    At this point, Jur, it's clear to me that since you don't want to acknowledge, discuss, or refute any of the alternate explanations for the handlepost failures other than repeating the same, unproven and unsupported ideas of fundamental design failure and engineering incompetence, that your mission is not thoughtful dialogue but rather simply to malign and discredit Dahon.
    Chaad--'95 DeKerf Team SL, '02 Lemond Buenos Aires, '05 Novara Buzz, '73 Schwinn Collegiate, '06 Mountain Cycle Rumble, '09 Dahon Mariner D7, '12 Mercier Nano, '12 Breezer Venturi

  7. #32
    jur
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    On the contrary, I think Dahons are quite good bikes. I toured Tasmania on an OEM one. I owned 3 altogether, one of which had that hinge.

    Re the hinge, the facts are out there - nothing unsupported at all. I posted plenty references. You don't think it is at all significant that that hinge has been ditched...? Or that Tern has come up with a bullet-proof hinge...? Perhaps you are unable to see through your own prejudices...?

    I thought you said you would love to get schooled. So I patiently explained a whole bunch of things, based on facts, but you are stuck on what you believe despite those explanations. Whatever. I'm going for a ride now.
    Last edited by jur; 07-19-12 at 10:23 PM.
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  8. #33
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    Quote Originally Posted by jur View Post
    On the contrary, I think Dahons are quite good bikes. I toured Tasmania on an OEM one. I owned 3 altogether, one of which had that hinge.

    Re the hinge, the facts are out there - nothing unsupported at all. I posted plenty references. You don't think it is at all significant that that hinge has been ditched...? Or that Tern has come up with a bullet-proof hinge...? Perhaps you are unable to see through your own prejudices...?

    I thought you said you would love to get schooled. So I patiently explained a whole bunch of things, based on facts, but you are stuck on what you believe despite those explanations. Whatever. I'm going for a ride now.
    Personally, I've been extremely disappointed owing an Apple iPhone.. Take a look at this.. http://abcnews.go.com/blogs/technolo...alian-airline/

    Who knows if mine will explode. Again, Apple products suck -- Not..

    Wow, I thought our summer is hot! Goosh, this room is getting really hot here. It might explode like an iPhone any moment?

    Chill out guys.

    I ride my bike everyday. Sometimes I wonder if my Trek carbon frame will explode any moment and I will crash and burn. And since I tour with my carbon frame, who knows that I might die some day as the carbon stays crack due to the stress of carrying those panniers. Probably not likely cause, I think I'll be run down by the overzealous Vancouver, BC drivers who are more content to speed through stop signs or trucks who are on a mission to side swipe me at any moment!
    Trek 5000 carbon road bike
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  9. #34
    New usename ThorUSA brakemeister's Avatar
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    its friday
    good day to make plans for the weekend
    and for sure include a little bike ride in the planning as well.
    be it on a Brommy Tern Dahon whatever ...

    thor

  10. #35
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    Sorry, Jur, that was unnecessarily snippy of me. I was frustrated trying to get my thoughts out while pecking away on an iPad, but that's no excuse for taking a jab at you. I apologize for doing that.

    Though we do have different opinions on the matter and on how to interpret the facts, that's ok; thankfully it's not a big deal, and I can certainly live with the possibility that I am looking at things wrongly. It wouldn't be the first time!

    Again, my apologies, but also my thanks to you for taking the time to explain your position and share your opinions. I enjoyed the discussion!

    Here it's lightly breezy, 80F, and beautifully sunny skies, so I'm gonna go grab a bike ride and enjoy the day, too. It is Friday in the summer, so who's to complain if I knock off early?!
    Chaad--'95 DeKerf Team SL, '02 Lemond Buenos Aires, '05 Novara Buzz, '73 Schwinn Collegiate, '06 Mountain Cycle Rumble, '09 Dahon Mariner D7, '12 Mercier Nano, '12 Breezer Venturi

  11. #36
    jur
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    ^^ Well that is a very gracious apology, a rarity in forums. Accepted, and kudos to you, sir!

    I'm afraid I am quite passionate regarding this hinge issue, I have followed it for some years and one day had the sudden insight into the raft of reports of a variety of problems, that there is a common factor of loosening fasteners.That Dahon thread that I posted a link to, has a list of problems and later, suggestions on how to improve those problems.

    It is possible that the recall was due to welding; I did see a thread in Dahon forums of s stempost which broke off cleanly in the welding. But those were rare in the reports; what was seen often enough, was those examples I posted 3 refernce of. What is significant to me, is that those photos show how the hinges broke off in the hinge forging itself, quite far from any welding.

    Anyway, I enjoyed my ride, I am still in the top200 of the Rapha Rising challenge in strava.com.
    My folding bike photo essays www.dekter.net/

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