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Sometimes metal fatigued and cracks... and breaks.


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I have a Moots CX TI bike 69 cm frame  They did oversize the down tube.   and a Chinese TI mtn bike frame.   Habenero cycles.  Both have taken a likin and kept on ticken.   The Wound Up fork got replaced (with disc brake tabs) by the guy's insurance company that turned in front of me with his car.     His statement in the police report said "I sped up to run into him"

The White Brothers mtn bike Fork with alum steer tube replace a long time ago when I hit some guy who did not have lights on his bike and I was doing about 27mph one night (sprint intervals).   I got a broken shoulder out of that one.

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3 hours ago, Yetti said:

I have a Moots CX TI bike 69 cm frame  They did oversize the down tube.   and a Chinese TI mtn bike frame.   Habenero cycles.  Both have taken a likin and kept on ticken.   The Wound Up fork got replaced (with disc brake tabs) by the guy's insurance company that turned in front of me with his car.     His statement in the police report said "I sped up to run into him"

The White Brothers mtn bike Fork with alum steer tube replace a long time ago when I hit some guy who did not have lights on his bike and I was doing about 27mph one night (sprint intervals).   I got a broken shoulder out of that one.

Wow - 69cm!  How tall are you?!! I’m 6’4” and I ride 61-62cm.

habenaro!  I have a bike from Xacd which is the Chinese source for habenaro.  I sourced straight from xacd in x’ian.  You can too.

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The Moots is a 28" c to c  top tube.   I am 6" 9" with a 39" inseam.   The running joke with my friends is they will ride up and ask how the 650 wheels are working out.   no they really are 700.   I learned a long time ago that a standard 3x spoke is a good pattern  I build them with extra tension because it think Rolf was right about spoke tension.   The rear just got a new rim and I still need to tie the spokes.

 

IMG_20190828_195944.jpg

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59 minutes ago, Yetti said:

The Moots is a 28" c to c  top tube.   I am 6" 9" with a 39" inseam.   The running joke with my friends is they will ride up and ask how the 650 wheels are working out.   no they really are 700.   I learned a long time ago that a standard 3x spoke is a good pattern  I build them with extra tension because it think Rolf was right about spoke tension.   The rear just got a new rim and I still need to tie the spokes.

 

IMG_20190828_195944.jpg

Thats a large bike!

But are those standard sized cranks?  I use Zinn custom long cranks - and Im short compared to you!

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25 minutes ago, aviatoreb said:

Thats a large bike!

But are those standard sized cranks?  I use Zinn custom long cranks - and Im short compared to you!

Did you note the 2 water bottle mounts on the downtube?  I have run 180 shimanos on everything for a long time.

  My brother has a Zinn with the 210 cranks.   He broke the rear triangle and had to get another one.  

I talked to Zinn at one point and he annoyed me on something so I kind of blew him off.  Conceptually there is merit to what he is doing. 

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On 8/27/2019 at 10:28 PM, aviatoreb said:

I was kidding check list but yes in 15 seconds you can look over the bike.  Tires and parts.  Glad I did!

dont laugh but I’ve snapped in two four different cranksets, one pedal, one frame and lots of spokes over the years.

If you’re breaking so many parts, I’d suggest running LoP to reduce the power output.

Clarence

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8 hours ago, Yetti said:

Did you note the 2 water bottle mounts on the downtube?  I have run 180 shimanos on everything for a long time.

  My brother has a Zinn with the 210 cranks.   He broke the rear triangle and had to get another one.  

I talked to Zinn at one point and he annoyed me on something so I kind of blew him off.  Conceptually there is merit to what he is doing. 

I had a bike once that had two bottles on the downtube - that was a custom bike built by...wait for it... Peter Mooney who is a frame builder in Mass.  I had that bike maybe 25 years ago when I was a bike racer in college.  Mostly these days I don't need a third bottle.  For three reasons - 1) I am old and lazy...so I rarely ride more than 2 hrs needing an extra bottle... 2) I live in the far north so it is less hot, 3) if I do go on a very long ride rarely, I am perfectly willing. on those rare occasions to stop at a story and get more to drink.

I do think the proportional to leg crank thing has been. fantastic and I have been riding that for 15 years now or so, initially on my Zinn, and then now on two other bikes.  Some 200's and some 190's.  My road bike is a Zinn and he did design severall clever things to make a stronger more stable tall bike (and mine is not as tall as yours).  Primarily the top tube is longer than typical wisdom - so for example imagine the top tube I see on your bike about 1.5cm longer then your stem would be a bit shorter (1.5cm) but your front wheel would be 1.5cm further away from you so your weight would be more between the wheels.  I copied that idea in the MTN bike  and the TT bike I had built in Ti by XACD and it is good.  That plus the long cranks taking a higher bottom bracket.  And there is a way of extending the front tube to make less stack height of your open fork area.  I'll send a pic.  His frame he built for me has really held up about 15 years now.

I like Zinn though.  I think you must have caught him on a bad day.  Actually since UC Boulder is my grad school almae mata I have been back there many times and also I have ridden with him - and he has even come here - and if he has a math question a few times he contacts me and he's quoted me a few times in his articles in velonews.  

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Just now, M20Doc said:

If you’re breaking so many parts, I’d suggest running LoP to reduce the power output.

Clarence

I actually have a. friend who is a professor of exercise physiology, and we came to the collective conclusion that the human version of LOP is to take nutrition by the fad now known as intermittent fasting.  Then you begin running on a more aerobic/fat burning metabolism. Vs the "ROP" version which is your sugar heavy anerobic metabolism.

But only a rough analogy.

The main problem is bike parts are designed with a 160 rider in mind - esp the performance racing stuff.  And they are always pushing the limit to try to make the stuff as light as possible - and that stuff always seems to break on me.  So I am always looking for something that is both quality/boutique build but also extra beefy.

E

P.S.  No one has. said it yet - but one thing I think is neat about Mooneys is that the frame is essentially like a bike frame.  Tig-welded chromoly tubes.  But I wish that could have been Ti tubes like our nicest bicycles.  Lighter/stronger and never corrodes.

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6 minutes ago, M20Doc said:

If you’re breaking so many parts, I’d suggest running LoP to reduce the power output.

Clarence

PS - my son just broke a pedal/cleat about three weeks ago - and broke his wrist.  :-(. He actually pulled right out in a spring -  and being a mechanical engineering geek he has a power meter - so he was doing 1500watts. That would be tour-de-france pro level numbers if he were about 40lb lighter/smaller. But he is a tall but skinny version of me - he is. 6'3.5'' and about 195lbs.  He. was using power-tap pedals which were just not up to that power.  So we did research to figure out which pedals the best sprinters are using in the tour.  So I just got him Shimano dura ace pedals.

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My ignorance of metallurgy and engineering leads to some nightmares here. This thread illustrates an example of a very beefy piece of aluminum fatiguing over time under repeated loads until failure.  The Mooney wing spar is also a beefy piece of aluminum that is loaded repeatedly.  We generally say these planes have no limit to their service life if maintained, and so I imagine the same concern does not apply.  But I have no idea why it wouldn't?

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7 minutes ago, DXB said:

My ignorance of metallurgy and engineering leads to some nightmares here. This thread illustrates an example of a very beefy piece of aluminum fatiguing over time under repeated loads until failure.  The Mooney wing spar is also a beefy piece of aluminum that is loaded repeatedly.  We generally say these planes have no limit to their service life if maintained, and so I imagine the same concern does not apply.  But I have no idea why it wouldn't?

Hence TI,  There are some TI frames that use the tubing as part of the suspension because TI can take repeated loading.   Insert PIC of Moots YBB   The shock is just an elastomer in a tube.  My wife has a YBB frame.     If I rode more I would have a YBB built for me. 

 

image.thumb.png.86cdf815c3e3e58c9565b6e76ae6c2d2.png

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1 hour ago, aviatoreb said:

PS - my son just broke a pedal/cleat about three weeks ago - and broke his wrist.  :-(. He actually pulled right out in a spring -  and being a mechanical engineering geek he has a power meter - so he was doing 1500watts. That would be tour-de-france pro level numbers if he were about 40lb lighter/smaller. But he is a tall but skinny version of me - he is. 6'3.5'' and about 195lbs.  He. was using power-tap pedals which were just not up to that power.  So we did research to figure out which pedals the best sprinters are using in the tour.  So I just got him Shimano dura ace pedals.

My watts numbers are pretty off the scale.   To push 235 lbs through the wind takes a bit of power.    Doesn't mean I am fast.  Just crazy watts numbers.    I have settled on the low to medium end of Eggbeaters.   If you go fancy TI spindle they can break.   Eggbeaters wear out over time because there is only a bushing on the inside and a bearing on the outside.   When I get a new pair, I pack them with axle grease then just run to failure.  There was that time a bunch of mtn bikers with not one stich of aero gear between them some with mtn bike shoes went out and got 2nd in the State Time trial.  We would have got first, but I pulled the last third of the way and blew out.  One of the three had a flat, so I had to catch back on for the finish.

  And yes most of my components are XT with some Durace XTR.   RaceFace Rings used to have a longer durability than Shimano Rings.   Back when I rode enough to change out chains once a month. 

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1 hour ago, Yetti said:

My watts numbers are pretty off the scale.   To push 235 lbs through the wind takes a bit of power.    Doesn't mean I am fast.  Just crazy watts numbers.    I have settled on the low to medium end of Eggbeaters.   If you go fancy TI spindle they can break.   Eggbeaters wear out over time because there is only a bushing on the inside and a bearing on the outside.   When I get a new pair, I pack them with axle grease then just run to failure.  There was that time a bunch of mtn bikers with not one stich of aero gear between them some with mtn bike shoes went out and got 2nd in the State Time trial.  We would have got first, but I pulled the last third of the way and blew out.  One of the three had a flat, so I had to catch back on for the finish.

  And yes most of my components are XT with some Durace XTR.   RaceFace Rings used to have a longer durability than Shimano Rings.   Back when I rode enough to change out chains once a month. 

Huh!  I never thought of egg beaters.  Yah - I bet your watts are high - and if only you were 135lbs instead of 235lbs then I bet. you could be tour de France champion!  Actually 235 at 6'9'' is pretty well fit.  That is a real beauty mtn bike you got there.

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1 hour ago, DXB said:

My ignorance of metallurgy and engineering leads to some nightmares here. This thread illustrates an example of a very beefy piece of aluminum fatiguing over time under repeated loads until failure.  The Mooney wing spar is also a beefy piece of aluminum that is loaded repeatedly.  We generally say these planes have no limit to their service life if maintained, and so I imagine the same concern does not apply.  But I have no idea why it wouldn't?

I know...this has always been my thought.  Honestly I wonder why a 50 year old wing spar is not highly suspect - and if it were then the way to manage the condition would be to constantly inspect it - perhaps one of 3 standard inspection schemes would be X-ray, die penetrant or sonic inspection.

I had a "soft ride" bike frame once that after about 5 years started creaking like crazy and had developed spider cracks through out.  I generally avoid Al frames.

That Thomson stem I showed cracked now that I look at it - seems a poor geometric design even though most of it seems beefy.  That was my (and their) mistake.

But now you see my point of this thread - which is discussing metal fatigue in general - in my case in a setting where I have seen metal failures several times.

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I've cracked several aluminum bike frames and snapped a carbon seat post (mid race). I've not yet had a failure of a Thompson part - stem and seat post on my mtb are Thompson. 

I like the Chris King headset, my mtb hubs are Chris King, they are fantastic and beautifully designed.

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13 minutes ago, ohdub said:

I've cracked several aluminum bike frames and snapped a carbon seat post (mid race). I've not yet had a failure of a Thompson part - stem and seat post on my mtb are Thompson. 

I like the Chris King headset, my mtb hubs are Chris King, they are fantastic and beautifully designed.

I LOVE Chris King Stuff - fantastic!

This is my second Thomson part failure - the other was a seatpost.  Seatpost failures are not so scary as they rarely lead to a crash.  A fork or stem failure tends to lead to a crash of the worst kind - high speed face plant.  KNOCK ON WOOD!  

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Y'know, just thinking about this thread this morning I examined the aluminum frame on my CB1000r.  Its just really thin aluminum.  I was genuinely surprised.  Still, that thin aluminum is more than enough to take lots of punishment, just like lots of thin aluminum airframes.  I still think there's something hinky with these bike parts.  There's no way they receive anything even approaching the kinds of stress to which motorcycles and aircraft are subjected.  Something smells.  I think you bicycle guys are getting ripped off hard.

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5 hours ago, aviatoreb said:

I LOVE Chris King Stuff - fantastic!

This is my second Thomson part failure - the other was a seatpost.  Seatpost failures are not so scary as they rarely lead to a crash.  A fork or stem failure tends to lead to a crash of the worst kind - high speed face plant.  KNOCK ON WOOD!  

True, however the carbon seat post that snapped during a race left a sharp jagged piece of carbon fibre pointing at my private parts. I completed the lap - about another 5km - standing. My quads were on fire but I avoided impaling myself.

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45 minutes ago, Hyett6420 said:

Ooh i had that once except it was the stem pole, inside the frame.  It fatigue broke just above the expanding joint that holds in it place.  The whole handlebars and stem pole came off in my hands.  Quote interesting crash!  :). 

Dood you are old :-) stem and quill

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2 hours ago, ohdub said:

True, however the carbon seat post that snapped during a race left a sharp jagged piece of carbon fibre pointing at my private parts. I completed the lap - about another 5km - standing. My quads were on fire but I avoided impaling myself.

Well... you coulda stopped safely.  After that what risk happens between the jagged carbon and your privates is between you and your maker.

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Still have the broken part?

Hard to tell from a pic, what may be dirt vs. actual....

I circled an area of interest that looks very much like intergranular type corrosion...

The Metal looks eaten away by salt water/sweat....

If the head of the crack initiates where corrosion exists... it is quite reasonable that you have found the source of the failure.

you can see why there are limits to the amount of this type of corrosion in spar plates...

The amount of time for that damage to occur can be less than a year...

It looks possible that some corrosion may have initiated a crack... crack propagation comes with the heavy load put on the part during use...

 

Additional thoughts...

1) is there a coating or just a polished finish?  Is the coating or polish missing where the corrosion occurred?

2) there are lines in the surface left over from forming the parts... any cracks start at the bottom of those lines?

 

The learning opportunity here... is there are some nice aluminum spar caps under the rug in the back seat... they have a tendency to have feet and dirt rub the protective coating off...

The bare aluminum can get exposed to all kinds of liquids from back seaters...

If you see corrosion starting on a spar cap... don’t wait for the annual to look into it... act immediately.

Corrosion works quickly... and inter granular corrosion works deeply...

PP thoughts only... not a metallurgist...

Best regards,

-a-

804D65DC-EE19-406F-9B88-D190BB97F7F4.jpeg

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