New project, nice welding

[n3303j]

The joining method must be secure enough for the job at hand.
The joining method must not damage or weaken the structure.

I built my recumbent bicycle with 4130 and Silbond 45 because it was strong enough. AND even with my heavy handed technique borne of lack of experience I probably would not damage the 4130 tubes by overheating them with my air/acetylene torch.

Welding instructor said you could do anything with oxy/acetylene torch and if you only had one method the torch was the do-all of the trade.

Friend built a go-cart with his torch and coat hanger wire as the filler. Kids never managed to break it.

Others here with far more experience can offer suggestions.

[BMCMOTO]

Let me just say, coat hangers ain't what they used to was!

Brian

[lucky phil]

But brazing is not as strong in most cases as welding, right? and what is the rule of thumb when deciding which method to use?
I asking for some information here because I have both a 110 welder as well as gas tanks, welding tips and cutting torch. In my youth I’ve did a lot of both while working in a car frame repair shop but it’s been 40 years since and my actual technical training was non existent, just a “do this do that” type of job but I did get good at both methods.

No Bronze rod doesn't have the same tensile strength as steel but that's not the only consideration. The main reason for the Bronze welding is that it provides a nice wide fillet joining the two structures which gives a dispersed load path for the stress from one piece to the other. This is important in a structure that isn't necessarily perfectly triangulated. In a triangulated structure you can go with TIG and a nice fine weld because the structure has in most cases a single load path in the correct direction. Ultimate rigidity in a frame as most would know these days is also not something desired or aimed for so ultimate tensile strength of the weld material in a well designed frame isn't necessarily important or desirable.
The other advantage to Bronze is as others have mentioned the grain structure of the parent material isn't affected or compromised. The ultimate tensile strength for the filler material often isn't the main consideration as even the bronze weld is much stronger than it needs to be in application. It "may" be less crash worthy but that's very hard to analyse. Ken Macintosh the Kiwi race frame builder at one time used to make his frames from material other than Chrome Molly and when asked why said that although CR-MO has a higher yield strength it didn't have any advantages in providing better rigidity. It may have survived a massive crash better but he thought if the crash was bad enough to deform his non CR-MO frame the frame would be destroyed anyway.
As you can probably tell from the images Bronze welding isn't exactly something that can be described as a low or moderately skill-full endeavour and that's the reason you don't see it in commercial applications. Same reason TIG was replaced with MIG in production because it basically cheaper, easier and faster and can be robotised. My 3 MV Agustas I owned in the early 2000's all had beautifully TIG welded frames but now all have MIG welding and have had for some time...sigh.
Interestingly Casey Stoner said that when he was racing the factory Ducati MotoGP bikes with the welded steel tube frames the biggest issue he had was that no 2 frames felt the same. he postulated that all the welded joints and the possible variations that introduced could be the issue as ally beam frames seemed more consistent. Interesting observation. True or not I don't know, KTM MotoGP guys dont seem to have an issue these days.

Ciao       

[lucky phil]

Metal shaping is great to do, especially with the right old Masters to teach you.  Good to hear you've got a connection to a real veteran.  There's lots of snake oil salesmen out there now to avoid, selling the latest widgets and hat trick work around. 

I've been busy lately working on my shops, with no spare time for actual metal projects.  I'm still learning & anxious to get back into working on V700 Corsa Record project.  It will be nice to update the build thread. 

Also want to improve my replica 1960's Holman Moody NASCAR cowl plenum air cleaner assembly for my 67 Galaxie so I can install it.  I used some basic power tools to make the wooden buck & radial hammerforms before shaping this project entirely by hand.  Fancy $$ tools may expedite a project but they aren't always necessary.









My free advice- go ahead and start practicing welding sheet metal (crs or alloy) with a gas torch.  No matter what you make, you'll need to be able readily & successfully join the pieces you shape.

Nicely done, I'm keen to learn the sheet metal skills.

Ciao

[Rough Edge racing]

Interestingly Casey Stoner said that when he was racing the factory Ducati MotoGP bikes with the welded steel tube frames the biggest issue he had was that no 2 frames felt the same. he postulated that all the welded joints and the possible variations that introduced could be the issue as ally beam frames seemed more consistent. Interesting observation. True or not I don't know, KTM MotoGP guys dont seem to have an issue these days.

Ciao       

Kevin Cameron did on recent article on Ducati frames. The frames flexed, by design or accident and it allowed the bike to corner better. Ducati riders said they "dug it " during cornering. The frames allowed some lateral flex. When Honda was chasing Ducati ,the Honda frames were too stiff..It took Honda a lot of money and research to figure this out.. Of course some riders preferred this , some not.
  I have several vintage Triumph land speed racers. One has a modified stock frame, the other a hanbuilt frame. I am an average  hobbyist welder using MIG and TIG. Tech inspection is tough and  non factory brazed joints would be very suspect. Same for  automotive racing roll cages, brazed joints  may not be allowed...

[lucky phil]

Kevin Cameron did on recent article on Ducati frames. The frames flexed, by design or accident and it allowed the bike to corner better. Ducati riders said they "dug it " during cornering. The frames allowed some lateral flex. When Honda was chasing Ducati ,the Honda frames were too stiff..It took Honda a lot of money and research to figure this out.. Of course some riders preferred this , some not.
  I have several vintage Triumph land speed racers. One has a modified stock frame, the other a hanbuilt frame. I am an average  hobbyist welder using MIG and TIG. Tech inspection is tough and  non factory brazed joints would be very suspect. Same for  automotive racing roll cages, brazed joints  may not be allowed...

Yes frame flex is engineered in these days and absolutely necessary and fundamental. Here's a clue, You see race and superbikes with long front engine mounts not short. So the mounts from the steering head area down to the front of the engine. They naturally went shorter and shorter for a few years there until they found they were too stiff and the chassis didn't flex enough. They all now use as long a front mount arms as they can looking for the magic flex. Triple clamps and swingarm pivots are another area, esp the s/a pivot. They used to be very robust but have been pared down over the years looking for controlled flex.
It's still more art than science but science has a big part now. The Ducati carbon box concept was an interesting methodology that ducati were pursuing and the desirable flex was engineered by arranging the lay of the carbon weave. Problem was that Stoner left Ducati and Rossi wanted an alloy beam frame so that avenue of endeavour was abandoned. maybe it will come back.

Ciao

[moto-uno]

 ^  Interesting that you make mention of the swing-arm mount . Quite a few years ago when Yamaha was just getting into flat track racing, they
made a frame that had allowed rake and trail changes and various swing-arm mount locations , apparently they found the swing-arm location ( up & down)
had the greatest effect on it's handling . Peter

[drdwb]

I have a dollar that says that's TIG. The color fades too rapidly near the joint. Doesn't matter.. it's nice work, however it was done. I, personally, have never been able to do that "stack of dimes" with a torch.

Chuck what exactly is the stack of dimes your referring to?  In High school we could earn an A in welding class by
 1 If we could use a torch to “weld” a penny on end to the bottom of a coke can.
 2 use a stick welder start with 1/8 inch 1x4 flat steel and build it up to 1/2 thickness the entire width and length, the instructor would cut through in two places any inclusions only a C , we spent hours in the booths smoking cigarettes and trying to earn the A, I managed the penny to the bottom of the can, but never mastered the build up. 50 years latter I’m slowly improving my mig and tig skills.

[lucky phil]

^  Interesting that you make mention of the swing-arm mount . Quite a few years ago when Yamaha was just getting into flat track racing, they
made a frame that had allowed rake and trail changes and various swing-arm mount locations , apparently they found the swing-arm location ( up & down)
had the greatest effect on it's handling . Peter

Yes, different reason to flex but the height adjustment has an effect on chain pull. Because most bikes have what is referred to "swingarm droop" that is the angle of the arm from the pivot to the rear axle drops you get rising rear ride height during acceleration due to chain pull from the top run of the chain. Just like a shaft drive bike without a torsion bar design. So under acceleration the rear suspension tends to extend not squat. It's not only the droop though as the pivot height in relation to the gearbox countershaft position is also a factor as is the size of the rear sprocket. This is why on a GP bike gearing changes are critical to chassis performance and why they try to keep the rear sprocket as close in dia as possible to each other by changing the countershaft sprocket as well sometimes to get the gearing right. It also minimises the lengthening or shortening of the swingarm to achieve the correct chain tension. So the swingarm pivot location is another variable to the effect of chain pull and therefore rear suspension extension during acceleration. Rear suspension extension during acceleration affects traction and the transfer of weight to the rear and away from the front. So on a GP bike from the apex when you get on the throttle you dont want the bike to squat at all, you want the rear suspension to extend which helps keep the front wheel weighed and the steering geometry steep so it doesn't unload the front tyre and you lose traction and/or the bike doesn't tend to understeer out of the corner and want to run wide. Now days Ducati have a squatting system that compresses the rear shock on late corner exit so the rear has more traction. This system as I said is in effect pretty much after all the turning has been done and the bike is in the transition phase to almost upright or you would negate all the benefits of rear suspension extension from the initial apex point. This also negates the negative from having suspension extension during corner exit in that the bike is more prone to wheeling so the squatting system helps with this as when the bike is wheeling either the rider needs to roll off, use a little rear brake of the anti wheelie software pull out some engine torque to control it and that costs time and drive.
On a flat tracker the pivot adjustment would be for much the same reason although I'd say the rear traction would be the major thing they would be chasing more than the front steering.

Ciao

[Chuck in Indiana]

Chuck what exactly is the stack of dimes your referring to? 

See that picture I posted of 8 tubes coming together? The ripples in the weld are commonly referred to as a stack of dimes if they are all the same. It happens each time you dab the filler into the puddle, normally at about one a second, depending on the job. There is a little skill involved. 

[Turin]

More than a little skill, nice welds look like a stack of dimes, and my welds look like someone fed solder to a duck, and I smeared it around randomly via the ducks keister .

[n3303j]

https://soranews24.com/2020/09/07/a-chain-of-welding-theme-parks-is-opening-in-japan/

I knew fire, sparks, molten metal and the crackle of electric arcs had to appeal to the masses.

[Canuck750]

More than a little skill, nice welds look like a stack of dimes, and my welds look like someone fed solder to a duck, and I smeared it around randomly via the ducks keister .

That describes my welding bike exactly!

[moto-uno]

  It's not all that hard to have brazing  with the ripples that appear similar to the Tig welding stacking of dimes . Nothing a few thousand hours of
practice won't help :) . Peter

[John A]

I stumbled across a nice instructional video and remembered this thread https://youtu.be/fWF0zCcXR5A
I would have used a little more of an oxidizing flame with a smaller tip but it wouldn’t be as pretty.

[Perazzimx14]

How about the quality weld on the steering head?