Fork upgrade
06-05-21, 09:18 AM
#26
Grouchy Old man
Thread Starter
I don't think anyone here has ever, or would ever recommend a rigid carbon fork for 'actual' mountain biking. The OP's bike, with it's slick tires, low saddle, and extra-high trekking bars looks like an MUP cruiser, so the fork he picked seems use appropriate.
I've never quite figured out why everyone on BikeForums feels like they have to ride through every pothole instead of going around; is there some Rule about deviating from 'The Line' that I'm unaware of? Or why obstacles like that are such a big deal in the first place? Get your butt off the saddle, bend your knees, and shift your weight off the front wheel. Is Riding Light considered a dark art around here?
I've never quite figured out why everyone on BikeForums feels like they have to ride through every pothole instead of going around; is there some Rule about deviating from 'The Line' that I'm unaware of? Or why obstacles like that are such a big deal in the first place? Get your butt off the saddle, bend your knees, and shift your weight off the front wheel. Is Riding Light considered a dark art around here?
By the way what does MUP mean? Thanks!
06-05-21, 09:23 AM
#27
Grouchy Old man
Thread Starter
I've had a Walmart bike. It was a GMC Denali road bike, the components were garbage, however the frame was stout. I regret not taking it with me, because I would turn into a gravel bike. The fork was solid, and could accommodate several different 700c tire sizes. It survived the mean streets of DTLA.
06-05-21, 09:49 AM
#28
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AND pressurized aircraft like airliners have a limited lifetime measured in pressurization cycles, not flight hours or any such calendar time. Every flight leg (takeoff/landing) counts against the 'lifetime' of the airframe. The airplane boneyards out west are full of airliners less than 20 years old - ones that have already reached their limit of pressurization cycles. Why? Remember when Aloha Airlines Flight 243 lost an entire section of cabin 'roof' a number of years ago (April 1988)? Too many pressurization cycles that caused microscopic cracks in the skin, which also allowed corrosion from the salt air to weaken further. The plane was only 19 years old.
Unpressurized aircraft generally have component lifetimes measured in flight hours, if they have such a limit at all. That's why we still have DC-3/C-47s flying commercial operations around the globe at 80+ years old!
.
Unpressurized aircraft generally have component lifetimes measured in flight hours, if they have such a limit at all. That's why we still have DC-3/C-47s flying commercial operations around the globe at 80+ years old!
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But what do I know? I only worked there installing fasteners & epoxy for a really large portion of my working career. Because of this failure there are now fail-safe straps installed at every frame.
They alao had a similar issue with skin laps using too few rows of fasteners a few years back. In extreme high use aircraft. The lap would "straighten out" causing cracking parallel to either side of the lap. The solution was to make the overlap of the lap a bit bigger & add an extra row of fasteners so the twisting force that was a product of puting the panels under tension was reduced.
I've worked on in service aircraft that were as many as 3 feet longer than originally built because of the accumulated stress loads over the airframes lifetime & their service will continue until something cheaper to operate comes along. Most aircraft in boneyards has to do with operating cost rather than lifecycles. That's why they are in storage & not scrap in the recycling pile. Yes, We've scrapped a few failures too. Those leave in pieces on trucks. That happens very rarely. The cause is almost always Manufacturing failure to properly execute on Engineerings instructions.
Blanket statements about any material without regards to the engineering involved in the structure or failure mode highlights said persons ignorance ignorance.
Last edited by base2; 06-05-21 at 09:56 AM.
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06-05-21, 10:16 AM
#29
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If the carbon fork you are using (and that is shown in the photo of the 1st post) has a carbon steer tube, using it at such extremes of excessive spacers could be considered "abuse". I would not ride it as-is. If you have to ride those bars up that high you really do need a steel fork or at the very least a carbon fork with an aluminum steer tube. I have always been taught that use of spacers in excess of about 30 mm puts undue stress on the steer tube on a carbon fork. To my eye, if you plan to keep this bike, get a bike shop to re-configure your stem and bars so that the fork steerer can be cut down for increased safety.
Last edited by masi61; 06-05-21 at 07:13 PM.
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06-05-21, 11:05 AM
#30
Grouchy Old man
Thread Starter
If the carbon fork you are using (and that is shown in the photo of the 1st post) has a carbon steer tube, using it at such extremes of excessive spacers could be considered "abuse". It would not ride it as-is. If you have to ride those bars up that high you really do need a steel fork or at the very least a carbon fork with an aluminum steer tube. I have always been taught that use of spacers in excess of about 30 mm puts undue stress on the steer tube on a carbon fork. To my eye, if you plan to keep this bike, get a bike shop to re-configure your stem and bars so that the fork steerer can be cut down for increased safety.
06-05-21, 11:22 AM
#31
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06-05-21, 11:31 AM
#32
Grouchy Old man
Thread Starter
06-05-21, 12:49 PM
#33
Senior Member
My education IS in engineering - so I feel that I CAN speak with some degree of NON-ignorance. I also fly - since 1975. I've also done maintenance on an airplane, under the supervision of a licensed A&P.
There are testing methods to look for micro-cracks in metals (MagnaFlux and Zyglo). What we commonly call 'carbon fiber' is technically known as Carbon Fiber Reinforced Polymer. There ARE testing methods for cracks or other damage to carbon fiber, but they are beyond the scope of the average backyard mechanic. Damage to carbon fiber components may not show to the naked eye. Eddy current testing, and ultrasonic testing are two methods that are the most popular... Airliners ARE routinely tested with ultrasound devices on the airframe, wings, and tail surfaces... A carbon fiber bike frame, fork, or wheel isn't.
As for the aircraft in the boneyards, many are not all that 'old'. YES, some were taken out of service due to efficiency (or regulatory changes), but many are there because of lifetime cycles. When I was with the airlines, they were just introducing the 737-300/500. The -200 was being removed for two-fold reasons - engine efficiency being one, and noise being the other. The high-bypass engines of the 300/500 were more efficient and much quieter. A bunch of pilots were sad to see the 727s retired. Faster than stink, but noisy! But now the 300/500 are pretty much retired in favor of the 700/800/MAX... The L-1011 and DC-10/MD-11 were phased out due to regulatory changes that no longer required more than two engines for over-water flights . ETOPS meant that the twin-engine 757 and 767 could be used for transoceanic passenger flight -
There are testing methods to look for micro-cracks in metals (MagnaFlux and Zyglo). What we commonly call 'carbon fiber' is technically known as Carbon Fiber Reinforced Polymer. There ARE testing methods for cracks or other damage to carbon fiber, but they are beyond the scope of the average backyard mechanic. Damage to carbon fiber components may not show to the naked eye. Eddy current testing, and ultrasonic testing are two methods that are the most popular... Airliners ARE routinely tested with ultrasound devices on the airframe, wings, and tail surfaces... A carbon fiber bike frame, fork, or wheel isn't.
As for the aircraft in the boneyards, many are not all that 'old'. YES, some were taken out of service due to efficiency (or regulatory changes), but many are there because of lifetime cycles. When I was with the airlines, they were just introducing the 737-300/500. The -200 was being removed for two-fold reasons - engine efficiency being one, and noise being the other. The high-bypass engines of the 300/500 were more efficient and much quieter. A bunch of pilots were sad to see the 727s retired. Faster than stink, but noisy! But now the 300/500 are pretty much retired in favor of the 700/800/MAX... The L-1011 and DC-10/MD-11 were phased out due to regulatory changes that no longer required more than two engines for over-water flights . ETOPS meant that the twin-engine 757 and 767 could be used for transoceanic passenger flight -
06-05-21, 02:31 PM
#34
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https://www.newscientist.com/article...ngerous-flaws/
https://www.washingtonpost.com/archi...-7fba0533d566/
https://www.nytimes.com/2001/11/27/s...stic-tail.html
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06-05-21, 04:57 PM
#35
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06-05-21, 05:24 PM
#36
Senior Member
That's NOT what the acronym was -- IIRC, it was for 'Extended Twin-engine OPerationS' or something like that... The available thrust of ONE engine was enough to sustain flight for an extended period of time - enough to get to the destination. And no - it wasn't just enough power to get to the crash site -- I've heard that one enough, too... 
06-05-21, 05:55 PM
#37
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Not officially, but that’s what the aircraft engineers and mechanics called it.
They are funny people (for the most part).
They are funny people (for the most part).
__________________
Ride, Rest, Repeat. ROUVY: terrymorse
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06-05-21, 06:23 PM
#38
Rhapsodic Laviathan
There is a lot more to that story. IIRC in excess of 80,000 flight cycles, & the epoxy they used to bond the panels never actually bonded because the mechanics that installed it were in a hurry. Had they been patient & followed procedure, the still cold (from frozen minus 80f) epoxy would not have been wet with condensation & the proper structural bond would have been achieved. The result of this error left the full structural load on the inadequet number of fasteners...for 80,000 cycles.
But what do I know? I only worked there installing fasteners & epoxy for a really large portion of my working career. Because of this failure there are now fail-safe straps installed at every frame.
They alao had a similar issue with skin laps using too few rows of fasteners a few years back. In extreme high use aircraft. The lap would "straighten out" causing cracking parallel to either side of the lap. The solution was to make the overlap of the lap a bit bigger & add an extra row of fasteners so the twisting force that was a product of puting the panels under tension was reduced.
I've worked on in service aircraft that were as many as 3 feet longer than originally built because of the accumulated stress loads over the airframes lifetime & their service will continue until something cheaper to operate comes along. Most aircraft in boneyards has to do with operating cost rather than lifecycles. That's why they are in storage & not scrap in the recycling pile. Yes, We've scrapped a few failures too. Those leave in pieces on trucks. That happens very rarely. The cause is almost always Manufacturing failure to properly execute on Engineerings instructions.
Blanket statements about any material without regards to the engineering involved in the structure or failure mode highlights said persons ignorance ignorance.
But what do I know? I only worked there installing fasteners & epoxy for a really large portion of my working career. Because of this failure there are now fail-safe straps installed at every frame.
They alao had a similar issue with skin laps using too few rows of fasteners a few years back. In extreme high use aircraft. The lap would "straighten out" causing cracking parallel to either side of the lap. The solution was to make the overlap of the lap a bit bigger & add an extra row of fasteners so the twisting force that was a product of puting the panels under tension was reduced.
I've worked on in service aircraft that were as many as 3 feet longer than originally built because of the accumulated stress loads over the airframes lifetime & their service will continue until something cheaper to operate comes along. Most aircraft in boneyards has to do with operating cost rather than lifecycles. That's why they are in storage & not scrap in the recycling pile. Yes, We've scrapped a few failures too. Those leave in pieces on trucks. That happens very rarely. The cause is almost always Manufacturing failure to properly execute on Engineerings instructions.
Blanket statements about any material without regards to the engineering involved in the structure or failure mode highlights said persons ignorance ignorance.
06-05-21, 06:30 PM
#39
Rhapsodic Laviathan
