Tuesday, August 10, 2010

Chad's frame melted together...

After a couple of long shifts over the weekend at the fire department, I groggily stumbled into the shop on Sunday morning to take care of a few items, namely finishing the plumbing on the fixture so I'd be ready to weld Chad's frame this week.  I've been putting this off for months, but finally buckled down and got it done. 

A view of the backside...routed so that I have full adjustment capability, swivels 360 degrees in two axis without binding, and with the flip of a quarter turn valve on the front, gas where it needs to flow :)


Picking back up where we left off, all of Chad's tubes were mitered and beginning to look like a front triangle.  The last task before being able to put the big clean on the tubes and weld them up is to get the seatpost binder welded on and slotted.  We had previously tacked the binder in place to allow for indicating off of for proper orientation of the tubing for mitering the bottom bracket.  Now, we're going to fully weld it and cut it up :)

I've had some folks express an interest in Ti fabrication, so I've been sharing a bit more on the process to fullfill their curiosity.  We'll look a bit more in depth at this process too.  The welding of Ti must take place in an oxygen free environment, most often resolved by replacing the atmospheric gases inside the tube and in the weld zone outside with an inert gas, Argon.  This is accomplished by sealing up the majority of the tube, leaving a relief hole at the superior portion for the lighter atmospheric gases to escape through.  How long do you have to purge before starting your weld?  I typically allow enough time for the interior gas space to be replaced 3 times.  Although I use a screened cup on the Tig torch that sheilds much of the weld puddle, it is subject to contamination and embrittlement until it cools below 800 degrees, so ya gotta keep it bathed in argon.  Below, I've built a make shift dam out of foil to help hold the spill over argon and prevent any stray air currents from blowing my shielding gas away from my happy little area...


I pre-flow the gas for about 12 - 15 seconds to allow it to pool a bit in the foil dam and then begin to weld...

Your weld should be shiny and bright with no discoloration if you have good gas coverage and heat control.

Here you can see the completed weld...wait, what's that?  He left part of it un-finished, eeegads!  Not to worry, I leave a small section on the center top and bottom of the binder unwelded to allow for easier slotting.  Trying to cut through your weld will dull your tooling in short order.


Off to the mill...

Once my binder is on, it's time to drill the terminal slot hole and slot the sucka!  There are lots of ways to insure that the tube is level and in phase when drilling the hole...here I'm using two squares off of the table surface to get it right.  Once correct, I center the tooling on the tube using the DRO and measure down 1.5" from the peak of the angled cut.  Then I drill away.

Once the relief hole is placed, the tube gets turned 90 degrees, squared up again, and the cutter centered on the tube again.  A nice even speed and plenty of fluid, cut in progress...

The finished product, pre-clean up...

With all the tubes finally finished, everthing gets scrubbed with warm water and mild detergent to get rid of all the oils.  Then it's off to the Scotchbright pads to scrub away the oxidation on the surface, and a final rinse in Acetone to insure that all surfaces are squeeky clean.  From this point forward, I no longer touch the tubes with bare hands, electing to use latex gloves with my golden needle gloves over top for welding.  I placed the bottom bracket and seat tube in the fixture, plugged the holes leaving a small outlet open at the top of the tube, and ran a root pass on the section that will be covered up by the down tube intersection...

I then placed the balance of the tubes and purged the whole shebang, tilting the fixture so that my escape hole was at the highest point to allow the oxygen out...

Once purged, I fusion welded the joints together, using only the base material for the first pass.  Here's what you are looking for...even material use from both tube surface areas, bright shiny finish, and even heat control...
With the whole frame fusion welded, it's off to the granite slab to check for distortion, looks good :)


It was late evening when I finally got home, but I was able to help get some walls up on the shop.  So much to do and seems like there's never enough time...
cheers,

rody

PS...I'm gonna have Christi read over the contest entries and choose a winner tonight, thanks to all who entered.

1 comment:

Craig Ryan said...

Excellent tutorial Rody! Thanks.
Craig