Nishiki Alien AL - Info? "Cracking stuff Grommet"

[incorrigible]

That last pic on page 1 is a nasty one. From what I can see, the crack goes underneath the downtube-headtube weld and then continues.
You won't fix that with a drill, some welding and a collar. That frame really needs a new headtube.

On the flip side, the original fork looks like it's in good condition, so if the bike is scrapped it can be salvaged to put another alien back to correct spec.

Anybody know an aluminum welder that has experience with building bicycle frames? I don't know if I'd trust just any aluminum welder with the job of replacing tubes. The fixes on my frames were possible because the damage was not nearly as extensive as this, and so experience with bike frames was not necessarily needed in my case.

 

[EarlofBarnet]

When I spoke to the guy yesterday he suggested cutting his losses and just scrapping the lot. However I've suggested swopping everything across on to a new frame. He would like a suspension fork too, so should mean the forks will be available.

I can't believe he hadn't noticed the cracks. Imagine it's last ride out could have ended nasty if the headtube had given way!

 

[incorrigible]

I say keep the frame and forks together, just in case the new owner decides to reincarnate this bike.

 

[danson67]

Incorrigible:

Anybody know an aluminum welder that has experience with building bicycle frames?

I'm certainly happy to help with that...I cover both camps there...
7005, so post weld heat not too difficult,

PM if you're interested.

All the best,

 

[incorrigible]

Incorrigible:

Anybody know an aluminum welder that has experience with building bicycle frames?

I'm certainly happy to help with that...I cover both camps there...
7005, so post weld heat not too difficult,

PM if you're interested.

All the best,

danson67,
That's good to know; I'll definitely keep you in mind should I need your services. In this case, this bike is too tall for me, so although I'd like to see it saved, there's not much point in me salvaging a frame that I cannot ride.

When you say "post weld heat", I assume you mean annealing. If just welding collars and gussets, is annealing necessary? I'll have to ask the welder who repaired my frames if he annealed them after welding.

I just tried to upload a pic of the repair done to one of my frames, but my 3G internet connection out here in the mountains of hillbilly country won't allow it this time of day. I'll try again later.

 

[danson67]

IMHO it would depend on the repair and the thickness of the tubes involved. If the collars and gussets spread the stresses well to the neutral axes of the frame, it should be OK. Plenty of heavier-end 7005 frames are not post-weld artificially aged.

If I were to replace the original head tube with similar (without collars or gussets), the stresses would still be concentrated at the lower corners of the welds as before. Thie set-up has been proved to often fail, so post-weld treatment would certainly be needed (ageing 6 hours at 200 degrees F (± 10 degrees F) plus 4 hours at 320 degrees F (±10 degrees F).

The headtube/weld side of the repair would be fine, the downtube/weld side and the rest of the frame would be slighly over-aged.
Ideally the whole frame would be annealed first, welded, then aged as above, but that's a whole lot more involved.

The weld profile itself can help a lot. The Nishiki welds are pretty convex, with some poorly wetted edges between 120 and 90 degrees. These are huge stress risers. 3:1 at least. I always try to get alu welds flatter or smoothly concave to taper the edges and even out stresses in the Heat Affected Zone around the weld:

It looks like an over-tight headset fit hasn't helped either.

All the best,

 

[incorrigible]

danson67,

Thanks for all the info.

Not to derail the OP's thread, but here's what I've got going right now (attached); 2 Alien ACXs and 1 FS3.

Here's some "before" pics of the FS3: http://www.retrobike.co.uk/forum/viewto ... alvageable

Head tube of the FS3 was cut along the cracks and then welded, and then welds were ground down to be flush with the original diameter/surface so that head tube would accept the aluminum collar that wraps around the front half of the head tube.

Like I said, I'll ask welder if he annealed (although I doubt he did). The shape and placement of the gussets and collars were my idea. Judging by the photos, is the repair sufficiently strong in your opinion?

I still need to smooth out a lot of the repair areas and also take the sharp edges out of the gussets on the ACXs so that paint will stick. I also need to cut out the seat tube "key-hole" slot on one of the ACXs (whatever its called).

Thanks in advance for your opinion.

 

[danson67]

Incorrigible:
It's always a bit 'poor form' to criticise other people's welding...

It's probably entirely safe, but I have to say that's not great. Just keep an eye on it.

Slow travel rate and low Amps make the arc wander and bead irregular. Would have been nice to clean up a bit after. I like the concave edge to the gusset (makes them less stiff at the ends, so evens stress a little) and the general location on the tube sides. The cap and rings on the headtube look solid enough, especially as bursting from the headset fit seems to be the main problem.

I would, of course, have done it differently (3 welders=4 opinions ) : sequence & locations of start/finish, some reinforcing welds, weld settings etc. or just replacing the headtube, but hey, that's just me

All the best,

 

[incorrigible]

Incorrigible:
It's always a bit 'poor form' to criticise other people's welding...

It's probably entirely safe, but I have to say that's not great. Just keep an eye on it.

Slow travel rate and low Amps make the arc wander and bead irregular. Would have been nice to clean up a bit after. I like the concave edge to the gusset (makes them less stiff at the ends, so evens stress a little) and the general location on the tube sides. The cap and rings on the headtube look solid enough, especially as bursting from the headset fit seems to be the main problem.

I would, of course, have done it differently (3 welders=4 opinions ) : sequence & locations of start/finish, some reinforcing welds, weld settings etc. or just replacing the headtube, but hey, that's just me

All the best,

danson67,
Thanks very much for the input. As for the concave gussets, I did that because it would fit better and be more comfortable if you had to carry the bike on your shoulder than it would using the straight edge of a purely triangular gusset. It’s good to know that it’s actually a better structural design than straight-edged triangles, although I had 2 frames fitted with pure triangles aligned to be parallel with the top 2/3 of the down tube (purely for looks). I can round those out (make them concave like the one in my 2nd photo) with a Dremel, but do you think the vibration might cause more cracking?

As for the head tube of the FS3, I realize it looks ugly, but I plan on smoothing all that out myself to save having the welder do it (and charging me more $$). I’ll start with an AC grinder with a sanding pad, and then perform any fine work by hand with files and sandpaper, so that when I’m done, the head tube will be a smooth cylinder just like an ACX head tube. I might even smooth out the transition from the old tube to the collar with (and I hope I don’t get tarred and feathered and run out of RB on a rail by the Old Guard of MTB purists for saying this)……ahem……a teeny tiny little bit of……um……bondo……Yeah, I said it: Bondo (let the hate mail ensue! ) Now I'll have to keep looking over my shoulder for the angry mob of purists. Perhaps someday they'll accept me when they see the finished product and realize what I've managed to cobble together from broken, lifeless bike parts.