Thursday, September 25, 2014

More cleanup prior to assembling the rear triangle.

The lugs are mostly filed,the  remaining dreck is gone from tubes.

The front triangle was placed back in the jig, and fell right into place - it looks like everything went together evenly.

The head tube and seat tube are cut to length and rough filed (not faced).

Started to fit chain stays.

It's beginning to look like a bike.

For the curious, at this point, the front triangle is 1.25 KG.

Tuesday, September 23, 2014

Pictures from 2 sessions.  Brazing and Filing, as follows.

Front end pinned and starting to flux it up.

Camera in one hand, torch in the other.

Despite bending the BB to tighten the ST/DT angle, when I started to reassemble the frame, the seat tube wanted to pull back.

A little heat on the front pulls it a bit forward and eliminates the tension.

Here's the seat lug pinned and fluxed.

The seat cluster was only pinned on one side, so I gave it a tack.  And spilled some filler.

The jigs centering cones get in the way of pinning the bottom lug edge, so a tack there as well.

Here the seat lug has been brazed, soaked, wire brushed, and is beginning to be filed.  Al little excess filler was drawn through both ports.  In general, however, the shore lines are nice and crisp - shouldn't be hard to clean up.

And here's the upper head lug at a similar point in the process.

Sunday, September 14, 2014

Back at it on a Sunday afternoon.  No quite as many pictures this time, as you'll see.

Got the BB mounted to the ST, and put the pulley mount on the ST.

In this pic, you can see that I pulled a bit too much brass through the drive side.  But, that's better than not getting complete fill.

Then it was on to the fork.  Start by sanding surfaces clean before brazing:
Here is the steerer after prep

And the crown is now brazed to the steerer.  The crown has a ledge on the bottom that the steerer butts up to.  I cut a pair of openings in the ledge to make it easier to feed the filler wire.

This is my first fork with separate reinforcing tangs.  
There is a pocket in the crown that allows the reinforcer to slide in next to the fork blade.  

You can see the pockets here.

Here the reinforcers are in place.

Apart from more fiddly fitting, there's the question of how best to approach brazing.  

There are three (or more) different weights of metal in play.  The reinforcers are quite thin.  The fork blades are medium weight, and the crown is quite thick.  Moreover, the crown has some delicate curlicues, the points of which are sharp and sensitive to heat.  

This picture better shows how a vise holds the jig while brazing.

It's just waiting for the torch and filler.

Here its been soaked, and I've begun cleaning it up.  

I'm reasonably satisfied with how it came out.  The next one will be better.

That was it for metal work today.  However, it was time to make a repair on my alignment table.  The handles of the nut (giant), that holds the BB in place, are made of what appears to be Bakelite, or something similar.  On two occasions, this has got away from me just as it reached the end of the threads, and fell on the floor.  The whole piece weighs several pounds, enough to break a handle when it falls.  Of course, each time, it landed on a different handle.  

After each incident, I've epoxied the pieces back together, and they've seemed to hold.  However, I wanted a stronger solution.  Today I sleeved the handles with knit CF tubes, I'll probably put another layer on in the future.  Right now, the epoxy is curing under a wrap of electrical tape (sticky side out).  Holes in the tape allow excess epoxy to squeeze out as you see above.

Tuesday, September 09, 2014

Got a few things done before work today, so you get some pictures.

After taking the front triangle out of the jig, I checked the alignment as pinned.

Everything was within a mm or less.  Next the top tube came off:

The tubes need to be marked where fittings will be added.  In this case, not to many bits.  A pair of triple cable stops on the top tube, and a derailleur hanger, pulley mount, and cable stop on the seat tube.  The plan is for the top tube to look like the below.
 And here it is after a quick soak:
The filler is Fred Parr's Fillet Pro from Cycle Design, and the flux was Stainless Light.  This gives good flow underneath and a nice little fillet around the edge.

The front derailleur hanger is from Richard Sachs.  His have a nice touch, an alignment nub which locates the hanger during brazing without any clamps or other holders.  You can see the nub below:
After drilling a hole in the proper location, the hanger will happily sit on the seat tube all by itself.
After some filler and a soak:
The following pix are out of sequence, the front triangle is still pinned together.  They show places where the lugs aren't fully conforming to the tubing, and need to be brought into line.
See the gap?

And below?

And that's it, what I did this morning before going to work.

More soon.

Sunday, September 07, 2014

I recently made the move to an iPhone based on a 1/2 price sale.  The biggest driver was the camera, and now I have a convenient way to document building activities.  Hopefully posts will now be more frequent.

I'm working on a cross bike at the moment.  The lugs are Newvex, meaning that they're probably silly ornate for cross bike.  Still, it'll look nice.

 All the curlicues require clean brazing.  They can't be cleaned up later.

From there, its on to fitting the DT to the BB.  Start by fitting on jig, and setting up pins.  Then I can take it off the jig, and registering the tube to the BB with the pins, scribe lines off the BB.

That's blue layout dye on the tube, but sometimes a black marker works just as well for a scribing medium.

Originally, I planned to use Reynolds 631 but the tube was too short.  That surprised me as the frame isn't that big at 57cm, but I grabbed a True Temper Versus tube and problem solved.

You can see the scribed line below.  Look closely and you'll see one of the holes for the pins.

For this joint, I trimmed with a hacksaw before breaking out the files.

Sometimes trimming first is faster.  Depending on shapes, the hacksaw might be replaced by a rotary tool with a cutoff disk.

OccasionallyI'll use a sanding drum on a bench-top drill press, although generally this is only something I do with carbon tubes.

Here's the trimmed tube:

Now comes my favorite tool: a Grobet USA 14" bastard cut half-round file.  

This is a file that fears no tube (although some take longer to due to being hardened).  

For today, its short work, followed by a little finishing with a 12" 2nd cut and an 8" bastard cut.

Here is a tube, coped to the scribed line.  That, however, isn't quite what we need.  Scribing often involves positions and angles that don't allow the scribe to get right into where we want it.

Now it's time for a test fit, and to determine what needs to be cut back.

The first image was too dark, even using the fancy phone.

Here's a try using an LED bike headlight.  It's better, but probably doesn't show you what I saw, so lets try another angle.

Below you can see that the bottom side of the tube is a bit long.

Small matter, just a few more strokes of the file before its done.  Note in the picture, the BB is again pinned to the tube to ensure proper registration.

So at this point, it was time to trial the seat tube.  The angle between it and the DT, as cast into the BB, was a bit off.  I could force things together, but don't like to build that kind of stress into a frame.

It's time to adjust the BB.  The BB is a pretty heft casting, it's not really going to adjust  very much.  Primarily, the ends of the sockets will move, and the inner socket will then allow some movement by the tubes, so all will be well.

Doing this requires some big heavy bars (I think mine came from Omar at Oasis Cycles).  

This pic should offer a sense of the scale of the bars.  They're solid, with copes built-into the ends so that they can fit together inside the BB or a lug.  

Prop one against the floor, and find a 200 pound weight to hang off the other, and shortly the adjustment is complete.


Often, though, adjustments are necessary to maintain a tight fit of the the socket around the tube.  Spare the hammer and spoil the BB.  It's what I say.

Mounting things into the jig now shows that everything fits together without springing any of the tubes.

And after removing from the jig, we can look at how the seat tube and down tube come together in the BB.

Mind, the seat tube hasn't been fitted for anything but its angle (which is steep on this frame).  

The cope on the bottom will come next, but for now, the square end makes is easier to see how well the tubes fit together.  And they look fine.

The next pic is fun because its hard to see what's going on.  Well, that's what I think.

All of the lugs suffer from oval openings.  In part, this has been corrected by squeezing the longer diameter to make the holes rounder.

This doesn't always work.  For example, the seat cluster is a fairly rigid casting, with the TT socket and seat bolt ears providing a bit of triangulation around the seat tube socket. 

These accouterments also make it impossible to find purchase in the vise for the required squeeze. 

At these times one just has to file away metal to achieve the necessary round bore.  Although it occurs to me now that an adjustable reamer might be worth a try in the future.

To file the backside of the ST bore, the lug was laid on its back, on top of the vise jaws, with the seat bolt ears firmly clamped in place.  

But, I'm no good at filing up side down, making it difficult to file the front side of the bore.  

Luckily, those rigid seat bolt ears can also be used to secure the lug under the vise jaws.  And yes, I could put my weight behind the file while opening up the front of the bore.  

Apart from opening bores on all the lugs, I drilled the vent holes in the head tube.  For those not familiar, a hole is placed behind the lug that provides an open path from the head tube into the down and top tubes.  

This helps the flux removal soak be more effective, and ensures air circulation for the life of the frame, that limits condensation and thus limit internal rust.

The holes are drilled using progressively larger drills until the required diameter is reached.  

In this case the required diameter is 1/2", because that's my largest bit.   

Below is a finished hole.

Some of you may recognize the tubing clamp as being from a Park stand.  I use a table mount Park bike stand as a quick clamp for tubing.  

A lot of drilling, sawing and filing occurs here.  It's much quicker than tubing blocks, albeit not quite as secure.  

When brute strength is employed, I generally revert to tubing blocks and a heavy bench vise.

By the end of the day the front triangle is test fit together with all joints coped and lugs in place.

The top tube lugs still need more pin holes set, and the vent hole in the ST is yet to be drilled.  However it feels like a productive five hours.

With this done, I'll focus on cable stops and the front derailleur hanger.

At that point, I can start brazing up the front triangle.

Meanwhile, you can see that work has started on fitting the chain stays.

Stay tuned.