[sportster]

Background:

• round pipe, mild steel -- chrome plated. It's about 18" long, and is a mounting bracket for Harley exhaust pipes. I'll remove it tomorrow & get a better look at this crack
• ~ 1" diameter (maybe 3/4")
• ~ 1/8" wall thickness
• need to repair a crack around most of the diameter
• I intend to TIG the repair (obviously, but only if it makes sense)
• not really worried about corrosion. Although keeping the remaining chrome in tact would be nice (but not mandatory).

Questions. Do I:

• bevel the crack out.... maybe drill the ends of the crack ? or just weld it with chrome in place ?
• grind the chrome off.... within (say) 1/2" of the crack ? or just weld it with chrome in place ?
• use a preferred filler rod ? e.g. Regular ER70S2 ? or Stainless ? or Silicon Bronze ? or ?

Thanks for any direction(s) you might offer.

P.S. I don't have any practice pieces that are chromed, so I only get 1 shot at getting this right.

[cj737]

Grind off chrome. ER70-S6 (MIG wire) or S2 (TIG wire) work fine. You sure it’s chrome-plated mild steel? Use a magnet to verify. Some, not all, are polished stainless, even chromed stainless. I see more cracks in stainless from vibration, cracks in mild steel from rust/corrosion. Try to understand which it is.

Bevel not needed, a small drilled end is helpful. 1” with 0.125 wall is pretty stout material as a motorcycle dimension. You sure about those?

[sportster]

Thx for the direction cj.... ok, I'll grind the chrome back & just do it. The crack is all the way thru (not a surface blemish), and is right next to one standoff. Drilling probably not an option. Should work fine if I just do it, I think.

You sure it’s chrome-plated mild steel?

pretty sure. It came from the factory, unchromed, just painted black. I had it chromed back in the early '70s. Yes, I've confirmed it is magnetic.

1” with 0.125 wall is pretty stout material as a motorcycle dimension. You sure about those?

It was just a guess at the time, but now that I have the part off, I was in the ballpark, sort of.

Looks like it started out in life pretty close to a 3/4" Sch 40 pipe. Then drilled, and 4 threaded inserts/stand offs welded in. Nominal dimensions --> ~1" outside diameter, and at the end where I could get a measurement..... ~0.810 inside, wall ~0.090.

The pics are probably overkill now. But I have 'em so might as well post 'em.











The pipe on the left is a scrap piece of 3/4" Sch 40 pipe. Just thrown in for a visual comparison.

[cj737]

So does that piece support the exhaust pipe? If so, probably the weight of the exhaust (way thicker than needed tubing) is putting stress on the end since the bracket is not connected to the frame at the end. Does that make sense?

Seeing the crack, I’d probably use a cut-off disc and slice into the crack to cleanly open it, then weld it back shut. Use a tubing sander and grind the weld flush, then have it re-chromed. You might also see if there’s a way to connect the end of the support closer to the far end to help with the stress.

[sportster]

cj.... yeah, I think you're on the right / same page.

That support arm carries the rear muffler (in the RED area (R)) and a portion of the front muffler (in the BLUE area (F)). The 2 standoffs are where the support arm bolts to the frame.

52 years of vibration has taken it's toll on the support arm...... so I guess I can't complain too much. I'll have a go at TIG'ng it tomorrow. Thx again for providing me with direction.



And where the mufflers mount / look overall on the bike.

[sportster]

Again, thank you CJ for the direction on this. Just to follow up....

This is the result of my lame attempt at welding this crack in chrome plated mild steel. As suggested, cut a slit in the crack & ground back as much chrome as I could.... but never could get it all. Nasty stuff when the chrome spits back in your tungsten and/or helmet.... and we won’t talk about the nasty fumes.

I’ll give it a 1 out of 10 for looks.... but it did pass my hammer test and it did survive a 300 mile weekend ride. So, for now, I'm happy with the overall strength. We'll see how long it lasts. Lol. We'll leave it there.

Top side views....





Bottom side view....

[cj737]

For the money, function over form pays.

You can always come back and use a 1/2 belt grinder air tool or tube polisher and grind back some of the weld before having it re-chromed. Should make it all disappear.

Ultimately ought to seek a rearward support solution to avoid this in the future…