Friday, August 3, 2007

Jet Vent

Jet vent is framebuilder slang for internal routing. In this case it's the rear brake that's internally routed through the top tube. The first picture shows the mitered top tube and the stainless steel tube that will be brazed in. You can see it's bent on each end and on the top tube one of the openings for the stainless tube is visible. The bends are so the tube passes through the middle of the top tube. This prevents the tube from hitting the top tube and making an annoying metallic "clink" sound whenever the bike runs over a bump.

Here's a picture of the stainless tube inserted in but not brazed.

The third picture is of the tube brazed in with the flux still there. I took this picture right after turning off the torch. I braze one end and then let it cool before brazing the other end. This reduces any possible issues with jet venting thin top tubes.

The fourth photo shows the same thing as the third but after the flux is soaked off.

The last photo is after the end of the tube has been shaped and the excess silver has been sanded off. The shaping is done with a Dynafile which is a hand held pnuematic belt sander. It makes quick work of it and yields great results.


giff said...

Very nicely done! Thanks for showing us how some of this is done!


thefastfifty said...

thanks Curt

do you have a photo taken through the inside of the tube? or is the frame already together?


Curt Goodrich said...

I don't have a photo of the inside of the tube. Sorry it's already a front triangle. Picture if you will the small stainless tube enters the top tube at an angle, takes a turn slightly, travels down the middle of the inside of the top tube, takes another slight bend and then exits the top tube.

Jim G said...

A friend of mine framesaver'd the top tube of his frame through the internal brake-cable hole. His frame didn't happen to have an internal tube like this...he lost the little red straw inside his top tube, forever gone! ;)