The Mtn Tourer (frame #2) is tacked

My laptop died a couple of days ago…right when I finished a mapping project thankfully.  I left for a meeting, came back home, tried to turn it back on, and it just was black.  Black screen, a slight thumping sound…dead.  It’s about a year and 3 months old and of course I only had a year warranty on it.  I hate it when that happens!  SO…i’m borrowing my girl’s laptop while figure something else out.

When it was dumping snow yesterday (yes, it’s May 15th…) i finished tacking frame #2 (the Rivendell Bombadil copy) inbetween playing with the dogs and having coffee by the fire with my girl.  Friday saw bluebird sunny skies and 62 degrees, and today it was 34 degrees, misty in the morning, and then just huge wet snowflakes all afternoon.  Springtime in the Rockies is awesome.

Frame #2 is SO much different than my 1st one, not just in geometry but in how it’s coming together.  I adjusted my build process and so far so good.  The first different thing I tried was silver brazing all the brazons BEFORE welding the bike.  After soaking them in the tub overnight (which is totally overkill I learned…an hour in hot water is sufficient), I cleaned them all inside and out, and dried them out with the air compressor gun.  I like doing it this way since you get a lot of the cleaning done up front instead of afterwards when it’s all together.A sweet new cleaning tool i found at Ace is the shotgun-barrel cleaner.  It’s $10 for a kit that includes an extenible aluminum rod that comes with different diameter round copper brushes that attach to the end.  It works awesome! I’m sure there are many other methods to getting the inside of the tubes clean, but this and some Simple Green works great.  It’s the brush you see to the right side of the tubes on the ruler in the pic below.

The next process change I tried was putting in a fusion pass on the seat tube where the downtube will overlap.  I tacked the seat tube to the bottom bracket in the frame fixture and made a quick fusion pass (no filler rod).  It’s easy if you have tight miters to do a fusion pass but once there’s even the slightest gap, I had to add filler.  You have to make sure it’s a really small bead weld since the downtube has to still fit tight against the junction. Since I started with a drop of filler rod, I had to file a tiny bit of the point on the driveside side of the downtube to get it to sit just right.

Next, I loaded the downtube and tacked it into place, first at the BB, then at the headtube, trading sides to equalize the pull of the tacks.  Then I loaded the top tube in the jig and tacked it to the head tube and then to the seat tube.  Pretty quickly, the front triangle was tacked and it was starting to look like a frame!

Next, I brazed the dropouts to the chainstays.  This is another new step in the process for me.  Last frame, I tig-tacked the dropouts to the chainstays, and didn’t braze them until I was all done welding the rest of the frame.  I am pretty sure that created a slight lift in the drive-side dropout making the rear wheel sit not perfectly straight (visibly noticeable but not bad).  So this time I followed what most people I read about seem to do with their slotted dropouts, and that’s to fillet braze them in the vise before tacking the chainstays to the frame.  I really like this method because it also makes it faster and easier to clean and file the dropouts post-brazing.  I didn’t take any pictures of the brazed drops…maybe next time.   I have to thank Yipsan Cycles’ YouTube videos on brazing.   He has some nice head-cam videos of him brazing and since I really learn from seeing how things are done the right way, it really was a great help!

After tacking the chainstays to the BB, I took the frame out of the fixture, put it in a bike stand to see how the rear wheel clearance looked.  It looked pretty perfect but then I checked the dropout alignment with my Park tools and the right dropout was about 1mm twisted down from the left.  Some light wrenching on the dropout tool made it better.  Next, I checked the alignment of the front triangle on the Bringheli mini-alignment table (seen in background below) by comparing the center of the seat tube near the bottom bracket to the center of the headtube.   The headtube was pulled a tiny bit up (left) so I put in a couple of small strategic tacks on the right side of the headtube and all was good.  (I’m slowly learning how to tweak alignment by putting in such tacks. So sweet when you don’t have to wrench on a frame and can just pull it in the direction you want by tacking or welding!)  Once the front triangle was aligned, I checked the center of the head tube with the center of the rear axle in the dropouts.  Bringheli’s system comes with a 135mm dummy axle that has a nice clear mark etched right in the middle of the axle to help align the rear triangle.  His small alignment “table” (6″ wide by 48″ long C-shaped steel) is a really nice piece of equipment to have, but a full alignment table must be much easier to use since you don’t have to keep twisting the frame around to check alignment.

Next, I put some finishing touches on the seatstays and jigged them up for tacking.  The Access65 has a bar to lay the seatstays against, but unless your slots at the dropouts are super tight, the bar doesn’t hold the stays in place.  I think this fixture is better for lugged building than TIG in some ways because you have to come up with some creative ways to keep the stays in place while tacking.  The chainstays were no problem but the seatstays just wanted to drop to the floor. (Gotta get the slots perfect next time with no slop in there!) This is one reason that the tacking went a bit worse on this junction compared to when I used a wishbone seatstay (wishbone’s are easier in my opinion).  The one thing about regular seat stays, or at least the ones I have from True Temper, is that they are SUPER thin (0.6mm).  I could’ve used 4130 16mm diameter tubes from Aircraft Spruce which are 0.9mm but I wanted to use “real” seat stays for this bike.  (For anyone out there learning to tig weld (myself included), I recommend practicing joining thicker tubes to thinner tubes since most tubes on a bike are just that.  Also, miter the tubes so they’re not just 90 degrees but in similar arrangements as a bike frame – the seat stay/seat tube junction is a great one to practice.)

Once I had the stays tacked, I put the 2.4″ rear tire in there again to see if all looked good, and thankfully it was golden.  No twist whatsoever so that’s +1 for brazing the dropouts before tacking the frame together.   Next, I’ll miter the seatstay bridge and tack it into place and see if I have enough acetylene fumes to get them brazed to the dropouts.  There’s an acetylene shortage this summer since the main plant that supplies calcium carbonate blew up! No kidding. Now the suppliers have to import more from overseas and from the one other US plant back east.  I would love to upgrade my tiny tanks to something bigger but they won’t let me!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: