Author Topic: Raised and bent bars  (Read 7578 times)

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Offline gPink

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Re: Raised and bent bars
« Reply #50 on: November 11, 2013, 01:22:07 am »
The pictures of the throttle side stanchion appear to show a crack where it receives the round bar. Could be mistaken.

Offline dude

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Re: Raised and bent bars
« Reply #51 on: November 11, 2013, 02:21:40 am »
The pictures of the throttle side stanchion appear to show a crack where it receives the round bar. Could be mistaken.
It's hard to tell, might just be a scratch. The tank and other panels are also for sale, all have light scratches. Probably dropped and totaled by the insurance company.. Doesn't look like a high speed crash. I'm telling ya, these bars aren't that hard to bend!

Offline dude

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Re: Raised and bent bars
« Reply #52 on: November 11, 2013, 03:43:09 pm »

Here's something I did a few years ago. I made the air deflectors from Tap Plastic smoked panels, and mounted HD pegs with long bolts thru a chrome socket spacer ;D. I bent part of a HD 3 piece clamp about 45 degrees to make the angle right, and the chrome didn't even flake off or mar! These have been over 100 mph many times and keep your feet from blowing off the pegs (which can really give you a pucker) without damage. Did I mention I like to bend things? And use sockets for spacers?
They were still attached when I traded it for the Connie less than a month ago.

Offline cuda

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Re: Raised and bent bars
« Reply #53 on: November 11, 2013, 11:20:36 pm »
I bent mine!
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Offline PeteTN_zgtr

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Re: Raised and bent bars
« Reply #54 on: November 12, 2013, 03:18:30 am »
OK, some thoughts Brian,

So the "rules" are not so much rules as guidelines ready and ably out- smarted by able and clever people who commonly squeeze what is required out of reality

Yeah, sort of, but these 'rules' are in many design textbooks and tend to be based on test data. To some degree you're right in that the variability in fatigue data is high and is hard to pin down exact design numbers for any given material, which is a good reason to be conservative.

Yeah, I don't really know the material properties of the stanchions vs. say a brake lever; maybe the evidence is more empirical (sort of). We have seen brake levers that bent a lot before breaking off. If you recall pictures of Egodriver71's handlebars after his accident, they broke off without bending very much. They didn't appear very ductile.

And yes copper and aluminum parts can be made for a infinite life if stress is low enough. What you're not mentioning and maybe not thinking of is that the copper on those navy ships is probably fairly ductile. When ductile materials are stressed past yield especially at stress concentrations, the material plastically yields and relieves the stress. And of course if the designers aimed at 10,000,000 cycles for a fatigue life, and they see 1,000,000 cycles in 20 years, then those parts will last longer than the ship.

My gut feeling is that those stanchions aren't that ductile just based on those pictures of the broken ones. And you still haven't addressed stress concentrations. Look on the back side of the stanchions; the casting flash and the cast in lettering and the internal corner at the top are all stress concentrations, which would yield and be fine in ductile materials. I guess those pictures of Egodriver71's bars just make them look not ductile ... OK I found the pictures, here you go, top of the stanchion broke right off without bending (not much if any). I believe a stress concentration in those bars on that bike would cause a small crack instead of just yielding.

Anyway, Brian you're keeping me up past my bedtime and I didn't have a cold one!

cheers
Pete

Offline PeteTN_zgtr

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Re: Raised and bent bars
« Reply #55 on: November 12, 2013, 03:24:38 am »
See if I can get the picture.

Offline nando

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Re: Raised and bent bars
« Reply #56 on: November 12, 2013, 03:32:51 am »
The only hope I have to get back to my regular life is to 'unnotify' myself out of this thread...so long my fellow metal-benders
I am voting for anyone who wasn't there during the government shut-down.

Offline BDF

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Re: Raised and bent bars
« Reply #57 on: November 12, 2013, 12:23:52 pm »
See- we are closer in our thinking than you thought :-)

One comment about the brittle stanchions though: I just do not think we (all of us on the planet) have enough data to have any conclusions, at least none based on more than 'gut feeling' (read: educated guess). The problem is the very, very few stanchions that have failed, and we just don't know what caused those failures. As I said before, I am leaning away from the stanchions being brittle and leaning toward manufacturing flaws just because there are so many C-14's out there, so few stanchions have failed, and yet when they do fail they seem to do so fairly easily, at least some of them, and so very quickly. So in my thinking, brittle stanchions fits in fine with the couple of very brisk breaks that some have had but it does not even get close to making sense that more have not broken without severe stress. Going by the early pictures in this thread, maybe even excessively excess stress 'cause the original poster sure got excessive with them IMO.

Brian

OK, some thoughts Brian,

<snip>

Anyway, Brian you're keeping me up past my bedtime and I didn't have a cold one!

cheers
Pete
KiPass keeping you up at night? Has the low fuel warning burned your retinas? Find peace, harmony and the answer to these problems. www.incontrolne.com

Offline PeteTN_zgtr

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Re: Raised and bent bars
« Reply #58 on: November 13, 2013, 12:59:03 am »
Well looks like we lost even Nando. Yes agree, the original poster got excessive with his bars!

I'll just mention that brittle can be strong if not abused or over-stressed. Again I strongly believe that the stress concentrations are what gets you in brittle materials because when "overstressed", cracks form at those locations but the part doesn't break off because the remainder of the material was not overstressed. Just material at one tiny place. I put overstressed in quotes because absent stress concentrations the part would not be overstressed but with stress concentrations the proper design load is reduced so cracks won't form at stress concentrations. Exactly the issue with this part that cracked at work recently.

We'll maybe Nando's right and we should sign off on this one. Good discussion and if anything maybe got people to be more thoughtful before they just start bending stuff

take care
Pete

Offline dude

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Re: Raised and bent bars
« Reply #59 on: November 13, 2013, 02:50:43 pm »

They call me MISTER Bender! (Play on the movie "In the heat of the night", an even better classic than "Peewee's big adventure".