Topic: Minimum thickness framerail

[InAquaVeritas]

I've been working on my 77 F1 for a few months now and messed up a bit of the grinding on it...possibly...hence this topic...

I have ground some tabs and such off the frame but in my overzealousness I dug into the tubes a little. My question is wether or not I should have it welded back up for some extra strength? The biggest spot is the backbone, where the tabs that held the harness sat. The rail where the seat lock and back hump went has a minor dent as well.

There will be more welding done on the frame at the same time: it will get some tabs for the indicators and rear fender, tabs for the covers and oil tank, brake cilinder mount, rear pillion mounts and my footpegs/rearbrake mounts.

This is OD at either side of the spot (paint still on), original tube OD:


This is the OD where I ground it down:


These are the two low points, seen from the side with a straight edge laid on top:


I hope someone can help me out, thanks!

[calj737]

It's not ideal, but I don't think you've created a dangerous situation.

[InAquaVeritas]

My thoughts exactly, it's not ideal and since I want this to be a daily driver (both highway and city) and I ride hard (straight to speedlimit, late braking, lots of forces) I want this to be safe.

My main worry is that if I have it welded back up the frame will warp since the tube section is so short.

[calj737]

I doubt it would warp, unless you went haywire with heat. Simple heli-arc or TIG will tack anything securely to that frame.

[FunJimmy]

1/2 mimimeter is only 0.010" (ten thousands of an inch) about the thinckness of a poor mans buisness card. Hardly a worry. If it where in a highly visible are, it would be worth brazing and filing for optics, but don't stay up worrying about frame failure.

[754]

1/2 mm is about .020..or 20 thou.. So probably an average of 10 thou per side .
 The wall thickness on the lower tubes is. 060........ So the backbone is that thick..or more..

[FunJimmy]

1/2 mm is about .020..or 20 thou.. So probably an average of 10 thou per side .
 The wall thickness on the lower tubes is. 060........ So the backbone is that thick..or more..

Ooops. My bad.

[InAquaVeritas]

1/2 mm is about .020..or 20 thou.. So probably an average of 10 thou per side .
 The wall thickness on the lower tubes is. 060........ So the backbone is that thick..or more..

Does that mean I'm safe? The 1/2 mm has been taken off one side, just the top. The rest of the tube is intact, paint and all still there.

I've got on old van as well, 1983 Volkswagen T3 campervan (my right-laner), that has very model-specific rust issues and to fix it I'm going to use a stick of tin, a blowtorch and a grater/sander. This is to replace the rust prone filler used in the weld. This is a common technique apparently, will this work to reshape the rails that have a slight dent in it or will this simply come off?

[calj737]

I don't know about "tin" but do know that lead will adhere to the tubing and was used as a body filler here in the States decades ago. Only problem is you can't weld to lead.

Are you planning on powder coat or painting the frame rails? If paint, just use some Bondo filler and be done with it. If powder coat, I guess if you're worked up over the minor irregularities melt some lead on, file smooth and level, and go forward!

[InAquaVeritas]

It's called 'vertinnen' here, which means tinning or tin-coating. It's bars of 75% tin, 25% lead.
It's still used for the T3's because of the rusty weld problem, holds better than bondo according to the forums on vans. Using it on my bike gives me a chance to learn to use it before I butcher the big (and very expensive) sheet metal of my van.

At first I'll paint the frame, in case I want to add or remove things. When I'm happy with it all, I'm going to powder the frame, so I want the tubes and welds to look as smooth as I possible.

[calj737]

I know what tin is, wasn't what I meant. I just don't know about tinning tubing for structure or technique.

If you plan to smooth the factory welds, your in for an effort. Before you do that, I'd strongly encourage you to re-weld them then smooth the new beads. That will insure proper penetration and that your "smoothing" doesn't weaken any welds.

[strynboen]

tinning vill not make it stronger.
 ist only kosmetic  or a vay to konnekt plates
 .the heat vill make  steel  strengh vorse
..leave it as it is.
.auto karosse are different..the form give it its strengh..not the thiknes...ok if it are rusted thin it veak aut. but generell the form gives strengh
.sorry for my english..

[mono]

tinning vill not make it stronger.
 ist only kosmetic  or a vay to konnekt plates
 .the heat vill make  steel  strengh vorse
..leave it as it is.
.auto karosse are different..the form give it its strengh..not the thiknes...ok if it are rusted thin it veak aut. but generell the form gives strengh
.sorry for my english..

+1 to that and what others said.   It's a negligible loss of material.   

[InAquaVeritas]

tinning vill not make it stronger.
 ist only kosmetic  or a vay to konnekt plates
 .the heat vill make  steel  strengh vorse
..leave it as it is.
.auto karosse are different..the form give it its strengh..not the thiknes...ok if it are rusted thin it veak aut. but generell the form gives strengh
.sorry for my english..

It was meant to be purely for looks, but I'll be using bondo. I never thought about the heat weakening the steel. It popped up as a thought when I was looking for repairs for the van. Thanks for the heads up!

I know what tin is, wasn't what I meant. I just don't know about tinning tubing for structure or technique.

If you plan to smooth the factory welds, your in for an effort. Before you do that, I'd strongly encourage you to re-weld them then smooth the new beads. That will insure proper penetration and that your "smoothing" doesn't weaken any welds.

I found the technique in an old book my stepdad has and I had never heard of it before, so wasn't sure on how widespread it was. I was going to use it as I've seen copper being used to smooth out welds on bare frames. Gives an amazing look as well.

Also a very good point about the welds, something I didn't think of either. Re-welding the whole frame is out of budget for now, I might do this at a later point if at all.

Thanks for all the info, I'm sticking to bondo and will leave the tube as it is. I might clear coat that section, so I can see anything happening to the structure before it really breaks ( if at all of course, I'm being overly, overly cautious with this. Peace of mind for an over-thinker)

[Lostboy Steve]

Weld it up and regrind it down.

[InAquaVeritas]

Weld it up and regrind it down.

That was my original plan, but after showing it to a few frame builders they all agreed not to weld it. It is on the top of the tube and the weld itself will shrink while cooling, this will warp the tube and ruin the frame. If it was all the way around I would've probably done it.