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Welders and Welding Which welder is best and the best way's to use them.


Welders and Welding Which welder is best and the best way's to use them.

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  #21  
Old 06-22-2016, 03:19 PM
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Quote:
Originally Posted by ScooteK View Post
I thought professional boxers punch with 1000lbs plus of force.
Interesting, I did not know that

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  #22  
Old 06-22-2016, 05:11 PM
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I'll try to address the comments before it gets too long winded.

You guys are speaking to impulse loads caused by a change in momentum. The boxer is essentially throwing his fist, creating an impact. The time rate of change of the momentum of his fist is the resulting external force.

Impulse loading will occur within the human body as well, but on a much smaller level. Racking up the clearances between bones, compression of tissue, etc. Speaking to the interaction with the bars, there will be some impulse loads due to the possibility of the hand not being in full contact with the bar when landing a jump. All of this would compound into the final force being translated to the bars.

These types of loads are far more difficult to approximate, unlike the static forces created by the strength of the rider (bench press example). I suppose this is where safety factors come into play. How confident are we in our design loads? What is an adequate safety factor? 1.5, 2, 3?

That's ultimately in the hands of the designer (myself), but it's fun to think out loud sometimes.

Graham - I think it'll be a rigid bike. He has another guy making the forks and yet another guy building the frame. When all is said and done, this will be a handmade bike with components coming from coast to coast.

No worries on the misinformation. Carbon will be the major contributor when it comes to heat treatment response, and SS ranks pretty low in that category. That's what makes it an attractive option when considering welding high carbon material - the carbon content of the weld stays relatively low even after dilution from the parent material.

Thanks for all of the input guys. Please correct me if I'm off in left field. It's been a while since I've dug into the books.
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  #23  
Old 06-22-2016, 05:31 PM
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Quote:
Originally Posted by Bray D View Post
Looking at the design of this bar and how the weld joint will be loaded, I suspect you are going down an unnecessary rabbit hole. I would expect the tube to fail at the stem long before either of the welds fail. Do me a favor and fab one up, put it under a hydraulic press and test my theory.
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  #24  
Old 06-22-2016, 09:54 PM
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Very true. Sometimes we lose sight of the end goal. Hopefully what we learn along the way is valuable.

I'm still leaning heavily towards using Er70 for this project.

I do plan to build a replica from mild steel. I don't think I could load it properly in my press (20" width H frame), but I would definitely test it if I could. I love this stuff.
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  #25  
Old 06-23-2016, 01:45 PM
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Quote:
Originally Posted by Bray D View Post
I disagree. Regardless of the scenario, his body needs to be capable of producing the force necessary to bend them. If he can't physically create 300+ lbs of force, he can't physically bend them. His muscles will fail before the bars do.

Another scenario to consider is the bike landing on the bars during a crash. It would be extremely difficult to approximate the impulse loading in that case, and I don't think I'm responsible for preventing failure in that regard anyways.

If he ghost rides it off a mountain and ends up bending the bars, that's on him, haha.

edit: Inertial forces of the bars play a roll as well, but being approximately 2lbs, the effect is negligible.
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Originally Posted by entropy View Post
Without damage just how much force can a statistical median human arm assembly transmit before failure?

Designing for the mechanical ingratiation of the human into a machine is completely different then designing a machine to protect/project the human.

Way interesting thread

E
Remember what happens to steering wheels in a head on crashes, the driver walks away with no injury but the steering wheel is folded in half......

Most of us who race have seen this, it is impossible for us to have the strength to fold a steering wheel in half, but after our crash that is what has happened.

Interesting article here on forces of a racing crash, scroll down to the steering wheel picture. http://www.hotrod.com/features/1507-...rontal-impact/
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  #26  
Old 06-23-2016, 02:12 PM
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Interesting. I've heard of that happening for sure.

Are you sure you're not strong enough to bend a steering wheel? They're not structural members designed to take an axial load, so I wouldn't expect them to be very strong in that regard.

This is a poor example as it's obviously a cheap wheel, but I wouldn't be surprised if you were able to bend a higher quality wheel as well.

Skip to 2:30

https://www.youtube.com/watch?v=SMxB4RpCDzA
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  #27  
Old 06-23-2016, 03:03 PM
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I went looking for images of bent or broken handle bars and came across this one:

Quote:


I aired about 2 ft into the air in the cement bowl in my city and that happened, im just glad it wasnt when i was doing anything hard because i could have really injured myself. I hope whoever designs these handlebars sees this photo.
The design is a bit different in proportions, so may not indicate where your bar would fail, but it does have me thinking about doing some basic stress analysis on this thing.
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  #28  
Old 06-23-2016, 03:18 PM
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Nice! These bars will be similar in width, making the grip length (and lever arm) similar in length to the one in the photo shown.

The numbers I calculated initially were considering a straight bar at full width, supported dead center. The grip length is far shorter than that. Looks like the required force to bend the bars at the end of the grip rather than the center are as follows:

Annealed 4130: 691lbs
Normalized 4130: 660lbs
4130 Q&T to 35HRC: 1446lbs

edit: Just to be clear where these values are coming from, I'm doing simple bending stress calculations for a straight cylinder with a 1" OD, .87" ID, made from materials with yield strengths listed in my post on page 1. After calculating the moment required to create the yield stress in the material, I then divide that by the length of the lever arm (15.75" for the full length calc, 8" for the grip length calc) to find the resulting force necessary to create that moment.

That force is per side, so I multiply by two to find the total force that must be produced by the rider.

Last edited by Bray D; 06-23-2016 at 03:25 PM.
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  #29  
Old 06-23-2016, 03:44 PM
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Well... why didn't I do that search days ago?
http://blog.fairwheelbikes.com/revie...dlebar-review/

E
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  #30  
Old 06-23-2016, 04:01 PM
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Interesting read, however they never loaded the bars to permanent deformation. All of their testing (in regards to what we're interested in here) was performed to measure elastic deflection.

They never subjected them to the loads necessary for them to bend.
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  #31  
Old 06-23-2016, 04:14 PM
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I'm wondering if your source is right for the relative yield strength of normalized vs. annealed 4130. Here's a link to another site that shows the same yield for normalized, but a lower yield for annealed, which is what I would expect.

http://www.engineersedge.com/materia...roperties1.htm

It's showing normalized yields at 63.2 KSI and annealed at 52.2 KSI...with a correspondingly softer Brinell number for the annealed material.
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  #32  
Old 06-23-2016, 04:23 PM
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I assumed normalized would have a higher strength numbers than annealed as well, but I got my numbers from Matweb so I just trusted their numbers. I always thought they were a pretty good source.

I have a membership, so I'm not sure if you guys will be able to see this, but here's links to my material info.

Annealed:

http://www.matweb.com/search/DataShe...b2b6259&ckck=1

Normalized:

http://www.matweb.com/search/DataShe...b96eaa9f0312fb

Q&T to 35 HRC:

http://www.matweb.com/search/DataShe...d450d5d7646d82
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  #33  
Old 06-23-2016, 04:45 PM
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I wish that I could remember who made my bars because after all this I would love to know the numbers on em...
I'm about normal size at only 6'6" and 250+ and so far as I know they are not bent... And before I wasted my back... I was known to catch a little air
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  #34  
Old 06-23-2016, 05:07 PM
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I'm sure we're over analyzing this, but it's all good. The material thickness alone is most likely double what most bike manufacturers are using. These bars are going to be beefy.

Do your bars have a cross bar, E? I have riser bars, but they're just a single tube. No issues in regards to strength here either, but I'm a lightweight too.
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  #35  
Old 06-23-2016, 05:40 PM
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Originally Posted by Bray D View Post
I'm sure we're over analyzing this, but it's all good. The material thickness alone is most likely double what most bike manufacturers are using. These bars are going to be beefy.

Do your bars have a cross bar, E? I have riser bars, but they're just a single tube. No issues in regards to strength here either, but I'm a lightweight too.
No Cross bar and I'll guess about 2" of rise.
Bike is a ridged, TIG, Tange/CrMo Frame set and I haven't ridden in way to long!
I look at it and my back whispers, "I can hurt you."


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  #36  
Old 06-24-2016, 09:26 AM
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Haha, I try to get out once every couple weeks. We have a few nice trail systems within an hour of me. Makes for a nice after work activity if I'm not busy in the shop.

I'm not sure this adds much value to this thread, but I started bending up a replica to prove out my process. This is just mild steel. Bend locations couldn't be any closer. It's right at the limits of my bender.

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  #37  
Old 07-19-2016, 12:26 PM
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Time flies, eh? Still working on these guys, amongst a slew of other projects.

I got the 4130 bent up last night. Came out nearly perfect. Hoping to weld in the cross bar this weekend. I'll be running weld tests on the mild steel this week to find a sequence that minimizes distortion.

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  #38  
Old 07-19-2016, 02:09 PM
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I'd be interested to see Clint's calculations. I have personally bent a couple of sets of bars in my younger days of riding BMX. I know you want the bars to survive but at what point do you want them to yield in order to not break the rider's wrists/arms/hands? BTW I'm 6'2" and 200 lbs so I'm certainly not huge but not small either.
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  #39  
Old 07-26-2016, 09:52 AM
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Getting closer. Everything is fitted and cleaned up for weld. My tests showed that it could pull up to .7 per joint. I'm OK with that, so long as it's symmetric. I'm hoping the higher strength 4130 resists warping more than the mild steel did. We'll see.

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  #40  
Old 07-26-2016, 10:15 AM
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I like the looks of those...the radiused cross bar is a nice touch. Nice work on the fitup!
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