Home Made Bikes

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Posted: May 18, 2019 at 23:49 Quote
I think that durability ain't worth fighting over, it's been long sorted on alu and steel frames alike, what you don't mention is the ability of steel to absorb shocks better than alu, this gives steel an advantage as a frame material, also a well designed frame that takes in account forces and build accordingly will outlast any ti/steel/alu one that is badly welded or executed.

* RMR, bb height it makes all the diff erence! :p

*f*ck, edit bb drop (when wheel size is the same)

Posted: May 19, 2019 at 2:43 Quote
I also posted below question in the home made parts topic, but this might be the better topic:

But talking design: what are typical input loads or G's for design of stems, pedals/cranks, frame/suspension? Is their a a source or paper with what is this typical for say XC-all mountain-enduro-gravity/dirt.

Are there any EC or NEN norms to be applied before you can sell item x as DH part in Europe? And what about norms in US?

Posted: May 19, 2019 at 4:21 Quote
Look for ISO 4210

Posted: May 19, 2019 at 4:58 Quote
Looks to be mainly for regular bicycles?

https://www.iso.org/standard/68260.html
bigquotesThis part of ISO 4210 does not apply to specialized types of bicycle, such as delivery bicycles, recumbent bicycles, tandems, BMX bicycles, and bicycles designed and equipped for use in severe applications such as sanctioned competition events, stunting, or aerobatic manoeuvres.
It is behind a pay wall, so I cannot check the whole document..

https://www.zedler.de/en/zedler-aktuell/publikationen/news-detail/the-iso-4210-standard-for-bike-tests-sets-a-floor-not-a-ceiling.html:
bigquotesManufacturers should also know that merely complying with ISO 4210 may not absolve them of liability in case of product failures.
It seems to be minimum not which is not even legally required, nor aimed ad providing proper testing to avoid liability.

The link provided there to the complete article is unfortunately dead. But I am looking for the answer of this bullet:
bigquotes- Does the lab vary test loads to account for different types of use? For example, mountain bikes should be tested at different loads depending whether they are intended for cross-country, allmountain, enduro, freeride or downhill use.

I would like to see more input load factors: say you would FEM a frame: what would be good factors to use for various disciplines, along these lines:
70% (?) x rider weight x max G on bottombracket (originating from cranks)
30% (?) x rider weight x max G on headtube (originating from the handlebar)

reaction forces on the wheel axles, in their max compressed position?

Calculating back from a fork spring, assuming that there will be a rider using the heaviest spring and still bottoming out: you can say 200mm travel x spring rate and that is your maximum force. But what, if any, factor on top of that?

What codes to use for max allowable stress for bending, shear and combined stresses?

Posted: May 19, 2019 at 7:06 Quote
Grumposaur wrote:
But talking design: what are typical input loads or G's for design of stems, pedals/cranks, frame/suspension? Is their a a source or paper with what is this typical for say XC-all mountain-enduro-gravity/dirt.

Are there any EC or NEN norms to be applied before you can sell item x as DH part in Europe? And what about norms in US?

ISO 4210-6 specfies the test protocol for frames and forks. Standard practice is to test to ISO 4210-6 + X%, where X is some arbitrary safety factor, often 25%. The question is how accurately the ISO testing models real stresses. They were developed from estimates of forces and observations of failures, so it's reasonable to expect the model to be imperfect.

Listen to the Downtime podcast with Cesar Rojo. He discusses riding for many months with data logging equipment on the bike and finding the actual stresses a bike experiences. His observation, not surprisingly, was that some ISO tests are far too severe and some fall far short; Cesar speculates this, combined with the "ISO + X%" testing, is why we keep seeing failures in certain parts of frames and rarely in others.

EFBE is one of the test labs with a more advanced test protocol. My preference when working with EFBE is to use their "all-mountain" test protocol for fatigue and their "DH" test protocols for max load. Their DH fatigue test is brutal and would result in an overbuilt all-mountain / enduro bike.

Posted: May 19, 2019 at 7:42 Quote
@R-M-R The info and links that you're sharing are pretty interesting. Thanks. Smile

Posted: May 19, 2019 at 9:08 Quote
R-M-R wrote:
Grumposaur wrote:
But talking design: what are typical input loads or G's for design of stems, pedals/cranks, frame/suspension? Is their a a source or paper with what is this typical for say XC-all mountain-enduro-gravity/dirt.

Are there any EC or NEN norms to be applied before you can sell item x as DH part in Europe? And what about norms in US?

ISO 4210-6 specfies the test protocol for frames and forks. Standard practice is to test to ISO 4210-6 + X%, where X is some arbitrary safety factor, often 25%. The question is how accurately the ISO testing models real stresses. They were developed from estimates of forces and observations of failures, so it's reasonable to expect the model to be imperfect.

Listen to the Downtime podcast with Cesar Rojo. He discusses riding for many months with data logging equipment on the bike and finding the actual stresses a bike experiences. His observation, not surprisingly, was that some ISO tests are far too severe and some fall far short; Cesar speculates this, combined with the "ISO + X%" testing, is why we keep seeing failures in certain parts of frames and rarely in others.

EFBE is one of the test labs with a more advanced test protocol. My preference when working with EFBE is to use their "all-mountain" test protocol for fatigue and their "DH" test protocols for max load. Their DH fatigue test is brutal and would result in an overbuilt all-mountain / enduro bike.
That conclusion is in line with the article I previously linked, that there is some inconsistency in the ISO, that would at least partly explain why certain things fail a lot and others hardly ever:
bigquotesPedals, for example, are required to undergo impact tests, but cranks are not. Yet there is no denying that a high load on a pedal, caused by a failed jump or a fall, is also transmitted to the crank and bottom bracket.
Indeed you see more often broken cranks then pedals.

But as said before: I cant see that ISO cause it behind a pay-wall: But does it specify different load-cases for different disciplines of bikes? I am really curious to the differences over the disciplines for design loads.

I see here that EFBE can do the tests for different categories accoording ASTM category; https://www.efbe.de/tri-test-en.html#zwei and they say there:
bigquotesmodern high-end sports bikes diversify to a degree of specialisation that the existing standards provide very few answers for. ISO 4210 only knows one type of MTB, and EN 15194 recognises no more than one type of EPAC
But I cant find the loadcases they will apply on their site. Only forms to submit a frame for testing, but prior that one would like to design for EFBE test case first, right?

Posted: May 19, 2019 at 12:01 Quote
Do we need a separate thread for metal properties nerds

Posted: May 19, 2019 at 22:50 Quote
Grumposaur wrote:
But I cant find the loadcases they will apply on their site. Only forms to submit a frame for testing, but prior that one would like to design for EFBE test case first, right?

I'm afraid I can't provide the EFBE test protocols, as I'm under non-disclosure agreement as a client. I don't have ride data like what Cesar Rojo describes, so I can't comment on how accurately the ISO and EFBE tests model actual stresses. The EFBE tests feel more reasonable, for whatever that's worth, and they offer numerous options for various categories of bikes. The only one that concerns me is their DH fatigue test. Maybe it's appropriate; all I know is it's brutal - far more intense than the other fatigue tests.

Posted: May 22, 2019 at 23:17 Quote
I love this discussions about who has the biggest (knowledge/title) dick

Posted: May 23, 2019 at 2:29 Quote
RMR knows everything, no need for further discussion

Posted: May 23, 2019 at 2:34 Quote
dhmtbr777 wrote:
RMR knows everything, no need for further discussion


Posted: May 23, 2019 at 6:38 Quote
One of the few times I ever wished to be a lecturer for the school of engineering was so that I could pull up the home made bikes thread in front of a full lecture hall of students and watch the carnage...

Posted: May 23, 2019 at 7:59 Quote
Kustomango wrote:
One of the few times I ever wished to be a lecturer for the school of engineering was so that I could pull up the home made bikes thread in front of a full lecture hall of students and watch the carnage...
Hahaha... I can just imagine the scene. With the students up the front willing to wage verbal warfare with each other and anyone else, going mental and foaming at the mouth at the prospect of having a discussion (argument). A group of students a few rows back drifting in and out of consciousness through lack of sleep. Finally, the group towards the back which is a mix of students that pay little attention during lectures but pass exams nonetheless, and then the ones going through the stage of wondering why the F they chose to do engineering Wink

Posted: May 23, 2019 at 9:48 Quote
No special engineering.


Then I realized I had screwed up the crank clearance and the yoke plates were too thin.

Lesson's learned. Don't freehand the bike, take the time to do the CAD/drawing. Do a full fit up BEFORE paint.


Bike had a double chainstay transplant and survived.

First ride.


 
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