TC Bros Hardtail Fit-up Question

[79josh81]

So I’m fitting my bike up for a TC bros hardtail. I do weld but this is my first time ever using a TC hardtail. I followed their frame prep directions with cutting and grinding and everything came out how they say it should be.

My problem is the diagonal cut top rails on the hardtail and how they meet up with the “stamped” section on the stock frame.

To put it lightly, the fit is kind of garbage as is. Maybe I’m being too picky but I have about an 1/8” gap in spots where the hardtail meets the “stamped” piece like in the pic. Myself, like most people I’d think, prefer a tighter fit when welding.

So I guess I’m just curious what did you all do to fix this and tighten it up some? Did you file the shit out of the diagonal cuts on the hardtail to cope it and make it fit better? Or did you just bridge the gap and then make a second pass over it and call it good?

 

[79josh81]

Everyone stand down...I was just being picky. It actually welded up pretty nice as is.

 

[mrtwowheel]

That's what I was thinking, not a HUGE gap, and any more grinding may have made the gaps wider. Some of the seat hinges that I've seen also double as reinforcement for those three tubes.

Scott

 

[fredintoon]

Everyone stand down...I was just being picky. It actually welded up pretty nice as is.

Hi josh,
1/8" ain't so big of a gap that it won't weld up nice.
Thing is, the larger the gap the more weld shrinkage you'll get.
Best you take a bunch of post-weld measurements, eh?

 

[79josh81]

That's what I was thinking, not a HUGE gap, and any more grinding may have made the gaps wider. Some of the seat hinges that I've seen also double as reinforcement for those three tubes.

Scott

Yeah I’m also going to weld some kind of a gusset up there that helps brace the forward force of the hardtail rails into stock frame.

 

[79josh81]

Hi josh,
1/8" ain't so big of a gap that it won't weld up nice.
Thing is, the larger the gap the more weld shrinkage you'll get.
Best you take a bunch of post-weld measurements, eh?

Yeah I just welded enough to fill the gap and then I took a second wider pass over it. Everything is still square and nice. I must have measured 20 times for squareness from a bunch of different points in between my welds.

As far as the gap, the way TC bros instructions sounded was like it was going to be a flush fit with no gap.

 

[brianis]

i usually run a plug inside to both sections if i do a weld on hardtail just helps strengthen

 

[79josh81]

All welded up and turned out good.

 

[59Tebo]

Yeah, it did! Nice gusset, too. It'll be "rigid" awright! Save that seat loop, if you ever decide to make it a restoration project. I didn't see a "before" picture, so I don't know what shape it was in before you put the saw to it, but all-originals are getting awful hard to come by. They only made so many of 'em.
I had an 'excuse'. My '75 was a, well, "Basketcase" when I got it, and a restoration project would've been prohibitively expensive. Believe it or don't, in the condition it was in, it'll be cheaper to chop.