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Bent Bars...

Old 01-26-21, 03:10 PM
  #1  
randyjawa 
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Bent Bars...

Ove the years, a few bikes have come my way with handlebars that tend to lean in, like the set on this old Torpado...


I thought, because I had seen a few like this, that the design was original but I am pretty sure that I am wrong. Take a look at how deformed the stem clamp section of the handlebar. The bar slopes away from the center. I might add that it was difficult getting that old TTT stem off of those screwed up bars...



Rarely will I keep a bike off of the road for a missing or incorrect item. With that in mind, and since my stash is long gone, I had to settle for a set of Asian bars...


Seems like that is always one more item to find but at least I will be able to get the bike on the road sooner than later...
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Old 01-26-21, 03:18 PM
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Nothing lost there, IMO. Sakae bars are great, and they hold up well.
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Old 01-26-21, 03:20 PM
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It probably wont straighten that kink near the stem clamp, but i used a 2t car floor jack and some pieces of wood to straighten one of my HVZ drop bars.
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Old 01-26-21, 03:22 PM
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My suspicion is that the AL used on old bars had inferior mechanical properties of more recent ones. That is probably why Cinelli used the sleeve on older bars.
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Old 01-26-21, 07:52 PM
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Bending aluminum seems sketchy to me, but I would worry more about trying to correct a modern bar than a soft vintage bar. I have one nitto bar I might try and correct sometime but the misalignment is minor and I will need to build some sort of jig to even determin what's wronge. The bars came on a nitto stem that was also slightly wraked, which I decomissioned on principle.
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Old 01-26-21, 07:59 PM
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Seen it before, but never as pronounced as Randy's example. You did the right thing.

That's scrap aluminum or an art project waiting to happen.

-Kurt
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Old 01-26-21, 09:00 PM
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I draw the line at salvaging old bars that have any signs of having been bent or crashed. If it's been bent, it gets tossed.
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Old 01-26-21, 09:14 PM
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Drop bars have multiple radical bends! I don't know if they are annealed after bending or not. I suspect not, so what is wrong with bending them back? Work hardening of AL is an issue but they were bent severely to begin with!

Has anyone seen stress crazing or fractures on new bars from the forming process? Does anyone know what the process yield is for material failure as opposed to dimensional deviations?
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Old 01-26-21, 09:18 PM
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Originally Posted by SJX426 View Post
My suspicion is that the AL used on old bars had inferior mechanical properties of more recent ones. That is probably why Cinelli used the sleeve on older bars.
...this is a true story. They will, eventually, break. somewhere near the stem clamp.



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Old 01-26-21, 09:29 PM
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Originally Posted by SJX426 View Post
Drop bars have multiple radical bends! I don't know if they are annealed after bending or not. I suspect not, so what is wrong with bending them back? Work hardening of AL is an issue but they were bent severely to begin with!

Has anyone seen stress crazing or fractures on new bars from the forming process? Does anyone know what the process yield is for material failure as opposed to dimensional deviations?
...new bars are made by a different process, because they are a different, modern aluminum alloy.



I have pretty good health insurance, and it covers a lot of facial reconstructive surgery. But I'm on my own for the dentistry that accompanies it. So I toss a lot of olde aluminum bars, even when they look relatively straight. I like the idea of having that reinforcing sleeve right at the stem clamp. But I broke a bar once (half tore it, actually). It got my attention, and maybe until you do that it's hard to understand how frightening it is.
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Old 01-26-21, 09:35 PM
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Old 01-27-21, 01:07 AM
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Originally Posted by SJX426 View Post
Drop bars have multiple radical bends! I don't know if they are annealed after bending or not. I suspect not, so what is wrong with bending them back? Work hardening of AL is an issue but they were bent severely to begin with!

Has anyone seen stress crazing or fractures on new bars from the forming process? Does anyone know what the process yield is for material failure as opposed to dimensional deviations?
I have spent my adult life working with metal and built up hundreds of vintage bicycles. One thing that I do know for sure is that aluminum does NOT like to be bent. Fractures are all but guaranteed. With that in mind, there is no way that I would attempt to bend the bars back, even if they were something special. Too dangerous, in my opinion.
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Old 01-27-21, 01:51 AM
  #13  
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I worked in the pipe and steel bending trade from 1981 to 2000 in the engineering department. We were able to bend all sorts of structural steel as well as pipe and tubing made from steel, aluminum, stainless steel, Incoloy, Inconel, Hastelloy, etc. Each material had its own idiosyncrasies of what it would tolerate. Aluminum age hardens very quickly. When bending aluminum, we'd have to buy it directly from the mill, because if it spent any time laying on the racks at a supplier, chances are it would crack when bending. These handlebars have had plenty of time to age harden, and any attempt at bending it back into shape it would be an exercise in futility.
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Old 01-27-21, 06:46 AM
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Thanks for the links. Interesting videos. Which AL alloy is not described in either one and doing a quick search did not reveal which is the preferable alloy.

I would be surprised if any were age hardening alloys, which would have to be specified as not all AL age hardens as described. Age hardening is related to temperature (heat) which impacts the crystalline structure to change (as does the work hardening).

I wasn't being critical or expressing a bias, just wondering about the material properties and the production process along with the engineering considerations of both.
@3alarmer - I am sorry you experienced significant injuries as a result of a failed bar. I understand the long term impacts from accidents. If replacing old bars with new ones gives you the confidence to continue to ride, that is great! Enjoy the ride!
My worst accident left me with a permanent vision impairment causing me to see double, depending on the range of focus. It is a challenge to wake up every morning and get my brain to switch dominate eyes! The nerves in my left forearm are still growing back after 11 years with new sensations occurring over long periods of time. Leaning the wrong way on my left arm is painful when the skin is pinched between the plate on the bone and whatever I am leaning on. Accidents and age change your perspective and sometimes makes you more aware of a given situation.
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Old 01-27-21, 07:46 AM
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Originally Posted by cudak888 View Post
Seen it before, but never as pronounced as Randy's example. You did the right thing.

That's scrap aluminum or an art project waiting to happen.

-Kurt
the bars and an old saddle and a wall
faux Picasso
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Old 01-27-21, 08:02 AM
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The above cautions are valid and believe me cutting a gorgeous Cinelli or a beautifully painted fork matching a complicated frame pattern that was dropped on the fork end, bending it, are truly painful .
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Old 01-27-21, 08:17 AM
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As far as aluminum bending, who here hasn't reefed their alloy brake arms for toe-in? Especially those squealing Mafacs. Perhaps solid alloy is more tolerant of bending than something hollow, like a bar.
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Old 01-27-21, 09:34 AM
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Originally Posted by clubman View Post
As far as aluminum bending, who here hasn't reefed their alloy brake arms for toe-in? Especially those squealing Mafacs. Perhaps solid alloy is more tolerant of bending than something hollow, like a bar.
I have used the caliper bend method to toe in calipers, in the past, but I do not recommend doing so with Universal calipers. The alloy Universal used is very prone to cracking. I do not have a picture of the caliper I did break, but the condition of these Universal brake lever/bodies might add credibility to my concern...


As for Mafac, as I recall, they have a toe-in adjustment built into the design, do they not?

Anyway, just a thought or two on the subject. The handle bar is now a matched set of handlebar (I cut it up but hated doing so - that said, I had to cut up a Pinarello years ago for the same reason, I still have nightmares).
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Old 01-27-21, 09:41 AM
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Yep, the Universal levers cracked just looking at them. Mafacs had no toe-in, you just bent them.
Fine looking Torpado Randy.
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Old 01-27-21, 10:43 AM
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Unless for a wall hanger, straightening bent alloy handlebars and then riding to any significant degree is foolhardy at best. Bars get bent generally for two reasons, a significant crash or long term metal fatigue (the dreaded droop) both of which should relegate the bars to the recycling bin. Compare the price of a pair of new bars to new teeth if you think I'm wrong (and that's if you only face plant...ever seen what happens when bars break while riding? I have, not pretty) and if you still want to straighten and use such damaged goods, I'll show you natural selection in action.
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Old 01-27-21, 12:11 PM
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Universal lever bodies and brake calipers are cast and not forged. Castings do not have an noticeable elasticity and don't deform, they fail catastrophically. That doesn't make them a bad caliper or lever base.
Designing with castings is a poor choice of saving money over durability, however.
P1000593, on Flickr

Impact with a car at 21mph
P1000602, on Flickr

Oh and look at the bend of the AL lever! Rolled sheet AL that is formed. It is all AL but the process to make the part can have dramatic difference. Not all AL is alike not only in the process but by the alloy of choice. AL alloys are a receipt of ingredients to get a desired result of mechanical properties based on the application and choices of the engineer. That receipt also determines the manufacturing process, both in the "cooking" of the receipt and the final process to make the end product.
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Old 01-27-21, 12:16 PM
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Originally Posted by Markeologist View Post
Unless for a wall hanger, straightening bent alloy handlebars and then riding to any significant degree is foolhardy at best. Bars get bent generally for two reasons, a significant crash or long term metal fatigue (the dreaded droop) both of which should relegate the bars to the recycling bin. Compare the price of a pair of new bars to new teeth if you think I'm wrong (and that's if you only face plant...ever seen what happens when bars break while riding? I have, not pretty) and if you still want to straighten and use such damaged goods, I'll show you natural selection in action.
Mine were crash damaged, i eventually made bullhorns out of them and they have been fine for some time now. When reshaping, they seemed to bend at new locations, and over a wide radius.
But yeah not recommended.
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Old 01-27-21, 12:31 PM
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Originally Posted by SJX426 View Post
Universal lever bodies and brake calipers are cast and not forged. Castings do not have an noticeable elasticity and don't deform, they fail catastrophically. That doesn't make them a bad caliper or lever base.
Designing with castings is a poor choice of saving money over durability, however.
P1000593, on Flickr

Impact with a car at 21mph
P1000602, on Flickr
French castings from Bike Boom-era are notoriously bad...those brake handles in above posts showing classic "metal rot" from a bad mixing of materials...stuff just crumbles away. Cast French "death stems" of Bike Boom-era have both bad alloy and poor design (no stress relief holes for example) and are really only good for wall hangers and parade bikes but I would not do any serious riding with them. I'm a vintage French-bike guy but for my period-correct builds I go with the contemporaneous forged stems from 3t.
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Old 01-27-21, 12:39 PM
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Originally Posted by geeteeiii View Post
When reshaping, they seemed to bend at new locations, and over a wide radius.
But yeah not recommended.
They bent at different locations because the previous locations were work hardened with the last bend action. Typical behavior and an indicator.
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Old 01-27-21, 01:02 PM
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Originally Posted by clubman View Post
Yep, the Universal levers cracked just looking at them. Mafacs had no toe-in, you just bent them.
I always favored grinding down brake pads to create toe-in rather than the less safe method of bending aluminum caliper arms.
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