Mountain Bike Reviews Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
59 Posts
Discussion Starter · #1 ·
I started my 2nd frame the other day using 1-.7-1 Top + Down tubes, a 1 9/16" paragon BB shell and Nova 44x1.25mm HT. I was trying to keep tubing thick to match my experience and welding skill level, which is not awesome... I also added some slip-in aluminum cups to the headtube during welding, which I had heard would help me minimize my distortion there...

I did still manage to distort the HT pretty good though, as shown below. It now measures ~45.7mm in the narrowest point, which after reaming would yield ~0.8mm wall.

My initial feeling is that I should scrap this and start over with a Paragon 44 HT instead - but seeing as I don't have that much experience, I wanted to get the thoughts of people that do so I can learn more about this as well.

Thanks in advance.
-Andrew


 

Attachments

·
Registered
Joined
·
183 Posts
I've done worse brazing :)

Interesting that your TIG has pulled it out of round in the opposite direction to my brazing (I think because of the way the brazing fillet holds the heat when cooling).

Why not just give it a gentle tweak in a soft jaw vice to equalise the diameter? Or try an exhaust pipe expander (I've never personally found the expander to work).

With a bad early frame I just fitted a cheap headset and slightly filed the cup to ovalise it to match the head tube (and didn't ream - just faced). I'm still riding the damn thing to work 8 years later without a creak or problem.

With cartridge bearing headsets you can press in the bare cups and then trial fit the bearing - if it drops in the cup OK then you are good to go. If a tight fit then either the HT or cup needs more attention.
 

·
Registered
Joined
·
1,882 Posts
Give'er a little squeeze in the vise to equalize it back and ream n build it.

You'll likely want to start building on the next one very soon anyway. So build it ride it and don't expect it to live a long life.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #5 ·
Thanks all, lots of options I hadn't considered. Despite riding the last frame I built pretty hard for ~a year now without issue, and great advice/help from a pro I unfortunately no longer live near, I tend to be on the overly worried side about what I personally weld together. That said, I will be building another frame soon so if this lasts through a year of my abuse I'd be happy.

I do like the idea of silver brazing rings onto the HT, I've never done that so it could be a cool learning opportunity, and it looks like NOVA does have some for this tube specifically. I guess I'll have to play around with things and see what I can make work for me.
 

·
Registered
Joined
·
482 Posts
I’ve done that and the bike was mine, number 14 for me I think? Those head tubes are too thin wall for my heat input so I’ll use Paragon only now. So it’s not just your experience level since I still have it happen!

Silver braze the rings in there with something “thicker” than 56, with adding filler to the thin sides. You can always get an oversized King headset in 0.05 or 0.1mm if the normal cups are too loose when pressing in.



Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #7 ·
So I ordered some reinforcing rings and an additional set of tubes - figured I'd give equalizing/brazing a shot and have a backup if I do something dumb in that process... I got a good result on the bottom end of the headtube with a squeeze in a vise, but the top ended up pretty D-shaped before I realized I'd gone too far. Probably for the best since I've only brazed small parts (h20 bosses), I decided to try brazing rings on this anyway for practice but haven't had any real good results yet.

Long story short - this turned into weld/braze practice and I've re-started with a Paragon headtube... Looks like I'll be sticking with those for the next while.

Thanks again though for the input - if interested I can post more pics/geo whenever I get across the finish line.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #13 ·
For me, I know I would definitely be interested in a heavier walled version of the 44mm head tube, possibly even with a slightly smaller ID in case it does go out of round slightly (though maybe not as small an ID as the PMW at 43.5mm).
 
1 - 13 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top