Rear Rack Pt. II

The general structure for the rear rack is done. Looks great!!! The Photos speak for themselves:

 My custom rack jig...

 Put attachment points on, powder coat, done!

Rear Rack

Though not part of my contract (final assignment for Metalworking,) I have the general structure for the rear rack complete.

How's it standing? I have no clue myself...

I took three pieces of steel rod, bent them, and fillet-brazed them together. This was my first attempt, so it is by no means symmetrical, but still is pretty visually pleasing. I plan to add detachable low riders, rings at the bottom curves for hooks, and of course attachment points once I have the frame complete. This gives a vague idea of what I'm going for:

It's kinda cute how optimistic I can be, huh?

Frame Drawing

Finally finished the frame drawing. Looks great; too bad I can't really bring out the thin pencil mark lines for you...

Sample of the design. It will be similar to a Kogswell Porteur/Randonneur, except without a few of the more modern attributes. Lugged steel with some fillet-brazing involved. Click on image to get the details.

Also designed some hooks to store tires in the shop. Fillet-brazed fork blades that were hacked off:

Still making it out to ride on the occasion. The weather out here has been beautiful in contrast to the constant rain drizzle that marks the usual. Can't fall too far behind on work though!

SS Cyclocross stop at the beach.

Forging and Final Lug Sample

Attempted forging last week. I was surprised that most of the class seemed to exhibit a fair amount of disinterested in the form, but it meant I had a lot of alone time with the forge. Here are some pictures of the sample iron rod I had manipulated:

The twist was fairly easy to accomplish, but curving the rod back into itself in a aesthetically pleasing manner was a bit more difficult. I also attempted flattening the other end and stamping a hole through it, but got too tired and weak doing it. Too much hammer swinging...

How it looked when I started. Rainy day.

I also attempted another lug sample after getting advice from one of my peers and faculty with some pretty good results:

Ignoring the large puddle of silver, the lines on this attempt are otherwise extremely clean compared to my past attempts. The reason for the puddle is that these two tubes didn't really fit together flush, creating a lot of gaps and inconsistencies. Hopefully, the real deal lugs and tubes will be much more precise.

Still going on plenty of road rides and fewer off-road rides. The longer distances I go, the more I buy into the whole Bicycle Quarterly philosophy. We'll see how I end up building this frame in the long run.

TIG welding vs. Fillet/Lug Brazing

In earlier post, I talked a little bit about the benefits of different joining methods. I've talked to various frame builders as well as metal fabricators in the area, and have come to some interesting conclusions regarding strength and endurance of different joints. Traditional thought would suggest that TIG welding is the strongest joining method; whereas with brazing there is simply a different metal compound that more or less 'glues' the two pieces of metal together, welding actually joins the two pieces into one.

True Temper, a well know fabricator of high quality golf clubs (and lesser known, bicycle tubing) engaged in a test of the 3 different joining methods: TIG, fillet, and lug. Each tests examined the strength of all the different joints without changing the quality of the joint (i.e. having a fixed frame builder for all 3 methods equally experiences in all techniques) or the forces of the test. Fillet and lug brazing both out lasted TIG in True Temper's test. A few conclusions were reached:

1. The greater temperature that TIG inflicts on the steel compromised the strength of the welds to a noticeable degree.

2. Though strong against blunt trauma, TIG as a long standing process did not hold out as long against constant applied pressure.

3. Silver brazing rod was far superior to brass brazing rod in both fillet and lugged joints. Being better at penetrating the grooves between miters and lugs, the surface area covered by silver was a significant improvement over brass of the same quality.

Though TIG was weaker as a lasting joining method, it was not by a considerable margin. All 3 joints proved to withstand the pressures that the average cyclist inflicts on them, leading to some other frame failure before joint failure.

Beyond strength, there are other benefits. With TIG and fillet, there is more freedom with different sizing and customization of the frame geometry due to the precision of the miters. With lugging, each tube is easier to replace if damaged. Aside from this, joining methods often boils down to aesthetic choice.

Finishing details on the frame drawing (or at least the first one.) Will post pictures when completed.

Conversions, Measurements, and yet more Joining

My most recent project in prep for this latest frame build had to do with wheel sizing. Conventional road frames these days measure at a diameter of 622mm, or more commonly referred to as 700c. The problem that many of these frames have is lack of tire and fender clearance as a result of strides made by the U.S. bike market that treats bikes as either play things or work out equipment.

Traditional clearance for road bikes. 23mm wide tires (unusually skinny) with minimal, if any more room for fenders.

To make these bikes practical, it is worth investigating the style of French constrictors from the earlier half of the century. The wheel size they most often used for their cyclo-touring bikes and city load-carrying bikes was 584mm, a.k.a. 650b. Though more difficult to find rims and tires for this size, I found advantages to making the switch. There are many school's of thought regarding wheel sizing; a popular one that I have traditionally followed espouses that wheel size should grow with frame size. Another one that I'm experimenting with is that wheel size should be predicated on tire size. The wider the tire, the smaller the wheel (in a nutshell.) Since I have little interest in 23mm tires that many road bikes come equipped with these days, I figure I would try these theory out on my own racing machine by put 650b wheels on it equipped with 32mm tires.
 

From this...

To this!

The conversion was a success, leaving me room to fit 32mm tires. I also tossed on some fenders that were donated to the shop. Perhaps its a bit blasphemous to equip such a high end bicycle with freebie bent plastic fenders, but it is the wet season after all. The bike has a bit of a clownish element to it, but is otherwise extremely comfortable and zippy.

The wheels were a bit of a challenge to lace, as I had both used spoke washers at the flange as well as laced the drive side 3-cross and the non drive 2-cross. This was to help balance out the torsional loads the wheel experiences from the drive terrain. There is more thought into it than that, but that's the short and narrow of it...

I'm pretty proud of this Chris King free bin score...

Label facing the valve hole perfectly!!!

What this project has taught me is that A: 650b's still feel fine even on large frames B: A bit more clearance while building my frame can open up a world of possibilities on my frame and C: Grand Bois' are a superior tire... SO GOOD!

This past week, I also dropped by the Bike Stand in downtown Olympia for a sizing up for bike fit. Shawn Stevenson of Stevenson frames did the measuring as well as gave a few tips on frame building. I was surprised by the results, as he found that a 63cm top tube would be appropriate (quite long) and that a 62cm seat tube would be like-wise a good fit. The above frame pictured has a 65cm seat tube! I'm not sure what I'm going to do with this information, but it certainly complicates things for me.

I tried silver brazing rod this week. Here are the results:

Lug sample.

Fillet sample.

Everything is coming along nicely, though I am feeling a tad under the weather. Hopefully work rounds out by week 7 and frame construction can start.