Right Stay

I started on the rear triangle on Sunday!.  My strategy is to get the right side just where I want it, then I can put a wheel/rear triangle t-square in it to properly align the left chainstay.  I'm mostly going at it this way because my homemade jig doesn't keep the dropouts lined up perfectly, and the extra steps let me tweak it on the fly.

The dropout went on easily.  I used some more of the 50N silver; I think I'm starting to get a better feel for it.  It certainly seemed to jump when I wanted it to.

I pinned the bottom bracket in the jig using the square profile nails that Cycle Design sells, then brazed it freehand.

The one issue I noticed was that the pins wanted to draw the stay up just a little bit from how it fit in the Jig, so I used the sophisticated method pictured above the add a little weight to the end.

Here it is, brazed and soaked.  On this bike, I've left all of the bottom bracket miters a bit long., with the intention of grinding the inside smooth when I finish.  

As a bonus, here's a picture of my cable routing:

Crossing the cable from the right shifter to the left side of the down-tube (and the left to the right) keeps the housing from having sharp bends, but looks a little odd since the cables must cross back under the down tube.  I spent a little time with some stainless tubing to solve that.  It's silly, it's overkill, but I like it.  This way the correct cable goes to the correct shifter, but the cross happens out of sight so the cables will stay roughly parallel to the down tube.  As it turns out, this stainless steel ball of spaghetti creates very little friction.

For the curious, here's the great Sheldon Brown's take on crossing the cables.  To keep things balanced, here is an opposing viewpoint.

Also worth noting, I've drilled the bottom bracket for drainage.  Almost all water related damage that I've seen or heard of on a bike was the result of standing water, not just exposure.  Hell, I've been riding my first build, sans-paint, in the rain on and off, for years and the rust hasn't made any real progress.  Since I can't totally seal this area (there's always the potential for a little water to sneak in through the seat tube), I wanted there to be a good way for it to drain.

Jig Interlude

This is a quick one, but there'll be more this weekend.

Here's my home made jig.  I've got the front triangle (already brazed) clamped in it.  I'm using my incredibly intricate chain-stay angle/length tool to set it up for brazing on the chainstays.  I use a digital angle gauge while I jostle it around to find the point where the angles match up with my rattlecad diagram.  

Two quick points: 

1) This works way better with a rigid piece of metal.

2) Referencing off of the head tube instead of the seat tube should yield better results (with a little math).  If the seat tube is forward or back a half degree, you'll most likely be able to account for it with the fore-aft position of your saddle.  If the relative angle of your head tube and chainstays is off, your bottom bracket height will change as will some of the steering characteristics.

Cheers, have a good week.

HIGH TECH!

Jigs and Silver

Jig

I put together my Half-A-Jig (tm) today.  I'm using one piece of extruded aluminum from 80/20 and a couple of v-blocks designed for drilling tubes.  One v-block is cut down to accommodate the lugs on the head tube, the points of which would otherwise keep the tube from lying flat.

The idea here is to help me align the head tube and seat tube so that they stay in plane, without spending $400 bucks and weeks on the materials to make a full jig.  Basically, I wanted a bit flat metal bar, but I didn't want to deal with the issues involved in clamping a round tube to said bar.  I had assumed that, in the process of getting it set up to work with the specific dimensions of my bike, I would have to shim things to get everything flat.  

I was pleasantly surprised to find that the two tubes ended up perfectly in plane!  I had a bit of wavering, but it was between exactly level and .1 degrees off... I think I'll live.  I may add some simple pipe clamps to hold things down so that I can tilt the whole structure to make tacking easier. 

First Silver Lug


I've decided to try my hand at doing lugs with silver.  Silver melts at a lower temperature and has a bit more surface tension and a lower viscosity when melted.  For these reasons, it can be a bit easier to work with than brass.

A practice joint mitered, lugged, fluxed, and ready to go!

Results: I burned some flux.  Having worked with brass mostly before, this isn't super-surprising.  Temperatures that would be fine with brass are way outside of the range that I should have the metal while working with silver.  I need to train myself to keep the flame back and moving more.  If I can spread the heat out more instead of focusing so much, I should be able to draw things through better.

When I cut it open, I found that things were fairly well filled in most places, but still had some voids that I wouldn't want in a finished product.  I'm going to do some more practice with random pieces of tubing and see if I can get past that point before I use the rest of my practice lugs.  

Jigs and Rattlecad

It's Time For a Jig


I've decided to make a jig to hold the frame tubing while I tack things in place.  It's possible to do the job without a more formal jig, but I think that I'm going to be better off with fewer things to think about while I'm putting everything together.  I'll still have to get my skills pretty sharp to keep the frame straight, but at least this way I have a good solid place to start from.

I've decided to make the Jig out of 80/20 aluminum extrusions.  Basically, 80/20 is a system of interlocking parts for building frames, jigs, supports, etc.  They bill it as "the industrial erector set" and that's basically what it is.  Here's an example of one of the extrusions.

This isn't too much of a shot in the dark.  Many builders have made their own 80/20 jigs, and a few pro's have even made production ready jigs out of it.  Mine won't stack up next to an Anvil, but if I'm careful about aligning everything, it should be good enough for me.

I'm basing my design on Suzy's over at Little Fish.  She's been cool enough to put up a plan here.  I'm going to use similar extrusions, but I'm going to move the vertical braces to the front of the jig.  That will make it a bit harder to line up, but it should also allow me to work with a shorter head tube.  As it stands, it looks like you need a really long head tube in that jig to clear the central spine, and then cut it down later.  This will also mean that I'll have to remove the dog leg that centers the axle.  It won't be as precise, but I think it'll serve.

Rattlecad!

I discovered a discrepancy today in the spec's for the fork I'm going to use with my frame.  It's a Surly Pacer fork and I've found the distance between the dropouts (where it holds the wheel) and the crown (where it fits into the bearings of the headset) listed as 371 in one place and 376 in another.  Yikes!

I've mentioned before that I'm using RattleCAD to make my plans and diagrams, instead of normal CAD software or BikeCAD (which you really need to pay for to get all of the information that Rattlecad gives you).  It seems to be the best option for new builders, but it's also being constantly updated (at least 3 in the last month, maybe more).  So, while adjusting the diagram to find out what the changes would have to be if that second number was the right one, I noticed that I could no longer manually change the virtual length of the top tube.  That's the length that it would be if it didn't slant down a bit.  For non-bike people following: this is a really important number because it has a lot of impact on where your handlebars end up.

I made a post in the RattleCAD forum about it and had an answer from the person making the software in less than a day.  And it worked flawlessly.  That's service, and on free software to boot!  So yeah, if you're looking for a way to design your first bike or two, give it a try.

Full disclosure: I don't work for Rattlecad dude, nor do I sell 80/20 as a side gig... I just think they're neat.