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Old 09-09-17, 08:02 PM   #226
linberl
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Originally Posted by bargainguy View Post
In the world of bicycle messengers, using a hi-ten (or even MTB) frame is not unusual. Less likely to suffer damage from repeated abuse - potholes and the like. While it's a little heavier than cromoly, less likelihood of downtime from frame damage, which means less worry of not having a paycheck, a fair trade-off.

I wonder if Brommies fall into the same category. A folder has additional stress to deal with - frame stress around the folding bits as the bike is being ridden as well as the stress of being folded/unfolded. So in a sense, it's over-engineering the frame at the cost of a little more weight. You might have to push a little harder from the extra weight, but it's well worth having your Brommie frame intact at the end of the day.
Ok, I can see that. Bike Fridays don't have mid-tube frame hinges so they can use a lighter steel. Moultons are steel but their hinges aren't the usual Dahon/Brompton/Tern frame hinge. So maybe bikes with those kind of hinges benefit from the heavier material? And maybe the aluminum Tern uses contribute to their failure?

From what I've seen, low end MTB use hi-ten. Messenger bikes tend to be beaters as well. Just not something I expect on a high-end bike. Are there any other bikes out there $1000+ that use hi-ten? I'd be surprised. I would expect the "over-engineering" to be in triple butted framing at that price.
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Old 09-09-17, 08:12 PM   #227
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Certainly any visible defect in a welded area is cause for concern. The history of that particular frame is not given, so it's hard to say whether its defect is structurally significant. (..snip)
Wut?
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Old 09-09-17, 08:16 PM   #228
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Originally Posted by Abu Mahendra View Post
Again, false choice. Obviously--you folks are deliberately dense when it suits--is not between Hi-Ten and Al, but rather between Hi-Ten and Chrome Molybdenum Steel.

You know, I know, we know that if the shoe were on the other foot, that is, if the Dahons and other blue-collar folders were made of Hi-Ten, you'd view that add further evidente if they their low quality. Once again, evidente if the elitism and bias that afflicts this channel.
First of all the Brompton does use Chromoly steel at least in part.

https://brompton.zendesk.com/hc/en-u...my-frame-last-

The way its worded above it is stating no mention of high tensile steel but I read something in the past that indicated that it was a mixture which was ok as brazing had no problem connecting the different steels at full strength. However it could be simply the frame is chromoly but the forks are high tensile steel I guess that would be accurate and fit in with the statement above. However I thought it was explained differently in the past with both metals used in the frame to give the right properties in the right places. I.e. a little bit of flex in the main downtube but rigidity in the bottom bracket. I guess the main frame could be chromoly but the rear section high tensile or vice versa as another option. The point is Brompton have designed their frame using different steels and also use brazing which is more expensive but gives a stronger frame.

I'd have no problem with Dahon using high tensile steel. I'm a huge fan of steel as anyone who reads my posts would know. I was the one saying the Dahon Curl should use a steel frame to give it better ride quality and help make it a more compact design. A few high tensile steel Dahon models with a 120kg weight capacity would be pretty good I think.
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Old 09-09-17, 08:24 PM   #229
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Not from Brompton, but I have no reason to doubt its accuracy:

Every Brompton hand-brazed hi-tensile steel main frame is essentially identical: the steel tubing, the hinge, the dimensions and the geometry.

from the link:

https://www.edinburghbicycle.com/info/brompton/
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Old 09-09-17, 08:30 PM   #230
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Wut?
Not all cracks lead to catastrophic failure, or necessarily *any* failure. A defect that affects structural integrity is ... (wait for it)... structurally significant.
Steve
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Old 09-09-17, 09:52 PM   #231
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Not all cracks lead to catastrophic failure, or necessarily *any* failure. A defect that affects structural integrity is ... (wait for it)... structurally significant.
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Old 09-09-17, 10:44 PM   #232
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Quote:
Originally Posted by bargainguy View Post
Not from Brompton, but I have no reason to doubt its accuracy:

Every Brompton hand-brazed hi-tensile steel main frame is essentially identical: the steel tubing, the hinge, the dimensions and the geometry.

from the link:

https://www.edinburghbicycle.com/info/brompton/
Now that we've all been sufficiently sidetracked by someone with a bone to pick with Not The Subject Of This Thread, back to our show.
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Old 09-10-17, 04:13 AM   #233
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Originally Posted by bargainguy View Post
Not from Brompton, but I have no reason to doubt its accuracy:

Every Brompton hand-brazed hi-tensile steel main frame is essentially identical: the steel tubing, the hinge, the dimensions and the geometry.

from the link:

https://www.edinburghbicycle.com/info/brompton/
I was curious why the Brompton site was saying both chromoly and high tensile steel in different places and turns out chromoly is or can be a high tensile steel.

4140 High Tensile Steel | Interlloy | Engineering Steels + Alloys

So both statements are accurate although I think Brompton would be well advised to only mention Chromoly due to cyclists often having low regard for high tensile steel due to its common use on entry level bikes. All the 41-- series steels are chromoly steels. Mystery solved.
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Old 09-10-17, 11:21 AM   #234
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I fail to understand why Brompton only offers a 5 year frame warranty when, theoretically, 4140 is stronger than 4130 (which is used in Bike Fridays with lifetime frame warranty). Is it because of the hinge or brazing or something?
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Old 09-10-17, 11:42 AM   #235
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I fail to understand why Brompton only offers a 5 year frame warranty when, theoretically, 4140 is stronger than 4130 (which is used in Bike Fridays with lifetime frame warranty). Is it because of the hinge or brazing or something?
Warranty terms are (theoretically) market driven. Also, keep in mind that, in the bicycle industry, a "lifetime warranty" on a frame usually means "for the useful life" of the frame --- not "forever". Most bicycle warranties are not transferrable to subsequent owners, and a "lifetime warranty" is pretty much worthless if the entity making the warranty no longer exists.

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Old 09-10-17, 12:22 PM   #236
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Warranty terms are (theoretically) market driven. Also, keep in mind that, in the bicycle industry, a "lifetime warranty" on a frame usually means "for the useful life" of the frame --- not "forever". Most bicycle warranties are not transferrable to subsequent owners, and a "lifetime warranty" is pretty much worthless if the entity making the warranty no longer exists.

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BF and Brompton have both been around for many many years so a lifetime warranty is not worthless if you buy a bike from a reputable company. Transferrability might matter to some, but if you buy a bike in the price-range of BF or Brompton, you probably already know what you want and what works for you. Dahon has a 5 year warranty - I expect more from Brompton at 2-3 times the price - but I guess Brompton buyers don't.
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Old 09-11-17, 07:01 AM   #237
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Originally Posted by linberl View Post
I fail to understand why Brompton only offers a 5 year frame warranty when, theoretically, 4140 is stronger than 4130 (which is used in Bike Fridays with lifetime frame warranty). Is it because of the hinge or brazing or something?
This is what they say on the site. Seems fair to me.

Quote:
The Brompton frame parts (front frame, main frame, rear frame, forks and handlebar support assembly) are covered by a 5 year warranty against manufacturing or material defects (please note that normal wear and tear is not covered). Compared to the frame warranty widely offered on conventional bikes - often referred to as “limited lifetime” - this may seem quite short. However, the nature of our frame design, with its regularly folded and unfolded frame sections, and with the majority of Bromptons used in day-in, day-out commuting, our bike can be subject to the stresses more comparable with bikes with full-suspension frame parts, for which a 5 year warranty is the norm. Nevertheless, if your Brompton is over 5 years-old and develops a fatigue failure, please report this to your local Brompton dealer so that the circumstances of the failure can be discussed with the factory.
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Old 09-11-17, 07:51 AM   #238
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However I thought it was explained differently in the past with both metals used in the frame to give the right properties in the right places, i.e. a little bit of flex in the main downtube but rigidity in the bottom bracket.
A little knowledge is a dangerous thing. The Young's Modulus of various structural steels doesn't vary all that much.
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Old 09-11-17, 09:09 AM   #239
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Quote:
Originally Posted by Abu Mahendra View Post
Again, false choice. Obviously--you folks are deliberately dense when it suits--is not between Hi-Ten and Al, but rather between Hi-Ten and Chrome Molybdenum Steel.

You know, I know, we know that if the shoe were on the other foot, that is, if the Dahons and other blue-collar folders were made of Hi-Ten, you'd view that add further evidente if they their low quality. Once again, evidente if the elitism and bias that afflicts this channel.
For the sake of conversation, Dahon does make steel framed bikes in addition to aluminum framed bikes.

Pricepoint Boardwalk and SUV models are made from Hi Ten Steel.

Speed D7 and Speed D8 models are made from Chome Moly Steel.

I am not sure what Speed Uno's are made from.

Molybdenum adds quite a bit to the quality of many steels, not just Hi Ten, stainless steel in particular. It tends to make steels more resilient and in other situations less prone to corrosion..
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Old 09-11-17, 09:42 AM   #240
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It's not just about elastic properties but fatigue weakness and the materials in question may be a mixture of hardened and unhardened. One of the big advantages of brazing is the ability to mix metals in construction. This may be variations of the same base metal, hardened and unhardened, different metals or even non-metals and differences in thicknesses where welding might damage the thinner material. There are a huge variation of steels and aluminiums all with advantages and disadvantages for each application. High end low volume brazed frames either using columbus or reynolds tubing have been blending different materials for years to get the right properties in the right places. Probably the same is true of welded frames its just more difficult which metals can be paired.

See no.7 here;

https://app.aws.org/wj/2000/09/0015/
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Old 09-11-17, 09:44 AM   #241
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This is what they say on the site. Seems fair to me.
Trek and Specialized both have lifetime limited warranties. They don't apply that to the suspension forks/parts but the frames are warrantied even on the mountain bikes. I've never seen anyone on a Brompton put their bike through anything even close to what a mountain biker does, they mostly pootle to transit. Daily use is a problem? If there are specific parts on the frame that are over-stressed, design them better with better materials (or exclude those specific parts if you cannot).

I'd buy what they're saying if the Brompton was in Dahon price range, but not at the price Brompton charges. I think they owe their customers more. Imo, it's a premium bike at a premium price with a low-end warranty. A quality steel bike should last decades and the warranty should reflect that.
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Old 10-16-17, 11:33 AM   #242
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I was just contacted by a Bay area medical researcher whose Tern frame failed last week. I encouraged him to post information and pictures into this thread.

Thanks,
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Last edited by downtube; 10-16-17 at 11:38 AM.
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Old 10-16-17, 12:29 PM   #243
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That would be me (the medical researcher). This is my first post here so can't upload a picture yet, but it was a clean break at the weld at hinge in the middle of the bike. Tern 20 inch bike; I was sent to the trauma unit at the hospital with several head injuries (even with a helmet on). Recovering now (this happened last Thursday so I'll get some stitches out tomorrow).
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Old 10-16-17, 12:35 PM   #244
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Best wishes for a speedy recovery, joewiems, and hoping that you will have your bike replaced under warranty.
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Old 10-16-17, 12:42 PM   #245
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That would be me (the medical researcher). This is my first post here so can't upload a picture yet, but it was a clean break at the weld at hinge in the middle of the bike. Tern 20 inch bike; I was sent to the trauma unit at the hospital with several head injuries (even with a helmet on). Recovering now (this happened last Thursday so I'll get some stitches out tomorrow).
I'm really sorry to hear this. I hope you recover soon.
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Old 10-16-17, 12:43 PM   #246
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Saw this on the London Brompton Club FB page last month;
supposedly by Unruly’s (Advertising Agency) reception in Whitechapel.
22008226_10154709102406436_6940662596475359571_n.jpg
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Old 10-16-17, 04:28 PM   #247
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That would be me (the medical researcher). This is my first post here so can't upload a picture yet, but it was a clean break at the weld at hinge in the middle of the bike. Tern 20 inch bike; I was sent to the trauma unit at the hospital with several head injuries (even with a helmet on). Recovering now (this happened last Thursday so I'll get some stitches out tomorrow).
Wow! Hopefully nothing serious. Update us on you're recovery.
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Old 10-16-17, 07:40 PM   #248
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I also wish him a quick recovery. He told me he bought two Tern's. The one that failed was a Link that was purchased in 2016. He said it was not part of any current recall.

He said he will stay away from public posting until his attorney gives him permission.

Thanks
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Old 10-16-17, 08:03 PM   #249
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The one that failed was a Link that was purchased in 2016. He said it was not part of any current recall.
Based on what I saw in the various failure pictures, it seems to me this was a design problem not a manufacturing problem; if this is correct it therefore affects ALL Terns made before the weld design was changed and augmented, and the recall is a red herring. There will therefore very likely continue to come cases to light of frames that broke exactly as the others did and not be part of the recall.

If Tern had any business sense, they would speedily replace this guy's two frames with the improved versions, no questions asked, and pay for his expenses, and get a non disclosure agreement.
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Old 10-16-17, 08:34 PM   #250
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He said he will stay away from public posting until his attorney gives him permission.
Wisely....
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