Ok so I'm about to start working on my CB350 frame, and plan on doing the de-tabbing of the usual tail section and side cover mounts. But was thinking I've never seen anyone cut off the stamp marks on the "back bone" where the 2 stamped pieces and spot welded together. I don't know if thats a good explanation of what I'm trying to do haha, but does anyone have a picture of a bike with this done to it? Some people have told me it might distort the fram and the engine might not line up or the bike might not track straight. The metal isn't that thick so I don't think welding it would create so much heat to distort the frame.
De-Tabbing and Welding Frame ?'s
- Thread starter 70Cb350
- Start date
mydlyfkryzis
当有疑问时踢你的敌人在生殖器上，你可以道歉后
70Cb350 said:
Welding distorts metal...
Proper techniques can compensate for this.
The backbone is the main load carrier for the frame.
Do what you want, but you don't have much experience, and this is a critical item to do right if you intend to actually ride the bike. The ribs add structural integrity to thin metal. The right way then is to make sure the replacement configuration is as strong and as stiff as the original.
Just butt welding the edges together will cause a loss of integrity and stiffness. The result can be as bad as a collapsed frame, or just something like a death defying wobble at speed.
Can it be done properly? Absolutely yes!
Can you do it properly? Your statement: I don't have much fab experience.
Your self described experience level makes me suggest you don't do it....
I wouldn't be doing it, my "I don't have much fab experience" statement was why I'm asking the question. I don't have the knowledge or experience to make the call myself and I didn't wat to go to a weld shop and waste someones billing hours asking questions. Figured I'd throw it out there to see if people have experience doing it or know of a way to do it .
Scruffy
West Tennessee
I have to do my own right now, can't afford my usual guy. Normally, I tack on the pieces, and the shop finishes the job. My preferred "torch" is FAA/USCG certified for airframes and fuel tanks. But, to fully do the frame on my 63 would cost money that I don't have right now.
So, high heat, slow feed speed... and a whole lot of plug/rosette welds to lock the pieces to the inner structure of the mated tubes. Even then, I'll need to have every line checked before I'll trust it.
So, high heat, slow feed speed... and a whole lot of plug/rosette welds to lock the pieces to the inner structure of the mated tubes. Even then, I'll need to have every line checked before I'll trust it.
mydlyfkryzis
当有疑问时踢你的敌人在生殖器上，你可以道歉后
Well, the way I see it, you are risking compromising the frame strength and rigidity for cosmetic reasons.
Fully welding the flange would increase the strength there, but removing it reduces strength. The frame needs to resist buckling, the flange increases the moment of the cross section and helps stiffen and resist buckling. When you remove the flange, you really reduce the strength. Think of an I beam. You are removing the center of the i beam. Even with thicker metal there, the frame will flex more.
If you are making a non-riding museum piece, go for it.
If you intend to ride safely, I think you are foolish to play with structural integrity. These frames are not the stiffest in the world, and the modification you are making will reduce the stiffness more.
Just for your own education, take a piece of 1/8 inch thick flat stock, 2 feet long. Hold it on one end. wiggle it back and forth and watch it bend. Then take a piece of angle stock. Same thickness. You can see how much stiffer it is. It is not the thickness of the stock that makes it stiff, the right angle bend adds to the moment of rotation and stiffens it. Angle stock is not "stronger" than flat stock, but it is stiffer. You are converting your frame from angle to flat. Even making it thicker will not make it much stiffer.
So fore warned is fore armed. You can do what you want. Others have done it, and that doesn't make it good. You are playing with basic engineering of the frame, blindly. If you calculate the moments, and put on sufficient material to regain the stiffness, then you are doing it right. But I don't think you are doing that and are playing with your own safety.
Had my say.....Good luck...you'll need it.
Fully welding the flange would increase the strength there, but removing it reduces strength. The frame needs to resist buckling, the flange increases the moment of the cross section and helps stiffen and resist buckling. When you remove the flange, you really reduce the strength. Think of an I beam. You are removing the center of the i beam. Even with thicker metal there, the frame will flex more.
If you are making a non-riding museum piece, go for it.
If you intend to ride safely, I think you are foolish to play with structural integrity. These frames are not the stiffest in the world, and the modification you are making will reduce the stiffness more.
Just for your own education, take a piece of 1/8 inch thick flat stock, 2 feet long. Hold it on one end. wiggle it back and forth and watch it bend. Then take a piece of angle stock. Same thickness. You can see how much stiffer it is. It is not the thickness of the stock that makes it stiff, the right angle bend adds to the moment of rotation and stiffens it. Angle stock is not "stronger" than flat stock, but it is stiffer. You are converting your frame from angle to flat. Even making it thicker will not make it much stiffer.
So fore warned is fore armed. You can do what you want. Others have done it, and that doesn't make it good. You are playing with basic engineering of the frame, blindly. If you calculate the moments, and put on sufficient material to regain the stiffness, then you are doing it right. But I don't think you are doing that and are playing with your own safety.
Had my say.....Good luck...you'll need it.
