# Brazed headtube gusset for mini-DH bike?



## abarthx19 (Jan 13, 2008)

Hi there,

This Christmas break I finally took the plunge and hired an oxy/acetylene torch and have been busy building my first frame, (following evening welding classes a while back and quite a lengthy design process).

My frame is for a mini-DH bike and as such has been designed around a 180mm Rockshox Domain fork.

As this is my first frame and the fact that the Domain fork makes for quite a large lever I have tried to get as much brass as I can around the joints to the headtube, especially the downtube. Theres going to be plenty of filing required to smooth these fillets out.

Originally I was planning to put a head tube gusset on the frame for added security but am currently wondering if it is required, or whether putting additional heat into the tubes in order to braze the gussets will compromise any possible the strength gains.

Below are some photos of the main frame and headtube joints before going into soak. And a photo of a Curtis bike frame that employs a brazed gusset.

































I've got the torch for one more day (this Sunday) and have still to braze the swing arm braces, shock mounts and rocker pivot as an absolute minimum in order to have what will hopefully be a serviceable frame (filing and the like can be done after the torch is returned).

So finally to my main question: if I have enough time left at the end of tomorrow after the essentials are done should I add headtube gussets to the frame, or should gussets be considered essential given the length of the fork?

(Additional info: the frame is all straight gauge chromoly. Downtube is 1.5" dia (0.049"wall thickness), toptube is 1.5" dia (0.035" wall thickness), headtube is a chromoly unit from Nova.

I started a blog to document the project but it is currently way out of date, but there are some CAD images that show the planned headtube gusset and give an idea of what the project is about - www.welwynmachineworks.blogspot.com )

Thank in advance for any feed back.

Cheers,

Mark.


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## beansworks (Jun 10, 2004)

That's pretty cool, good luck in that project of yours! -


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## DWF (Jan 12, 2004)

abarthx19 said:


> Hi there,
> 
> This Christmas break I finally took the plunge and hired an oxy/acetylene torch and have been busy building my first frame, (following evening welding classes a while back and quite a lengthy design process).
> 
> ...


That's way more brass than you'll ever need on 4130 and all that heat is not good for the tubes, especially 4130, so I'd not add to it. Also, your tube sizes are more than adequate for any single crown fork on the market with no additional gusseting.

BTW, as the owner & racer of a Brooklyn Racelink, I can tell you they are one hell of a bike.


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## abarthx19 (Jan 13, 2008)

Thanks for the replys guys. I think i'll forget the gusset then. Time is going to be tight enough just getting the other bits done. This is starting to feel a bit like scrap heap challenge (I think the TVseries was called junk yard wars in the US).

Cheers,

Mark


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## rocwandrer (Oct 19, 2008)

Sweet first bike! That gusset as shown in your drawing would negatively effect fatigue life anyway. Better to leave it off. Have you checked that your headset will press into that head tube ok yet?


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