I am experimenting with different techniques for welding. Today I turned off the automatic pulse in the welder so that I could use the foot pedal to create “dimes”.
In this technique the foot pedal is used to create each dime as the welder is moving the puddle along. In this style the movement, feeding of the rod, and application of heat has a rhythm that is intended to produce a smooth weld that appears like a stack of dimes.
As you can see, my “dimes” are not very even. I need to work to refine my technique.
For comparison, I did the following recently using the pulse feature and a steady movement of the weld puddle over a rod that was in effect simply consumed as the arc moved to apply the bead. Often this technique is called “lay wire”.
Both techniques are important parts of making good welds. Welding Tricks and Tips has a short video that I find helpful as I am working on my TIG welding skills.
I am getting better at my welding technique but there is still so far to go.
Last weekend I made a big batch of sample tube miters for practice.
Each night after work and riding I have been doing one or two practice joints before bed. TIG is about developing muscle memory and comfort with controlling the weld process. After practice my mind can work the issues while I sleep.
I am not there yet but eventually, I will get my skill to the level I seek.
There will be a lot of tig practice for 2014.
Most high end steel mountain bikes are built with 969 (or thicker) tubing. The notation for 969 means that the tube is built with wall thickness of 0.9mm on the ends and 0.6mm across the middle span. Tubes are built this way to save weight and put the strength where it is needed. The thicker ends support the welding process because it is VERY hard to weld on super thin tubes.
Welding thin tubes requires heat control. Even with “normal” bicycle tubing it’s pretty easy to jack up a joint if you don’t manage and adjust as you are moving through the weld process. Part of what I like about welded bicycle frames is the human element in construction. Especially with TIG heat control is a learned skill and an area where builders are always working to improve.
For today, I cut a few 858 top tubes into short sections for joint practice. With this tube the walls are 0.8mm thick at the ends and then 0.5mm thick across the main part. Making a weld with a short section that came from the middle is hard because the wall is super thin. It’s good practice because it is actually harder to manage then welding on thicker ends.
The practice on the artificially thin tubes will help me improve and will making me better for when I weld “normal” tubes.
It gets pretty busy with commuting, mountain biking, and inline skating but then again, variety is the spice of life.
I have been thinking a bit about road riding and decided to set up one of my mountain bikes with gears and dropped bars. Most of the parts are mountain bike components but I have TRP brakes, Duraace 9 speed shifting, and some fat road tires. The bike has been a lot of fun for commuting and gravel roads in Umstead. Today I decided to give the local road bike group ride a try.
For the group ride, we did around 65 miles. The Raleigh Gyros group is really smooth with a nice rotating paceline. The miles flew by at around a 20mph pace. Based on how much fun I had today I figure building a “true” road bike is on the 2014 agenda. The biggest thing with a “true” road bike is that I will run skinny road tires and an overall lighter package of parts.
The dropped bar mountain bike is not the perfect road bike but but it still did pretty darn good plus it is really an awesome fast commuter and gravel grinder. The gearing on the bike is really tight with a straight 11..19 on the rear and 40/48 up front.
This year I am really working to improve my welding. My current welds are not bad but they are really not great.
A great weld is one with a very small heat affected zone, consistent fillet size, and a very smooth bead transition. Good welds are also look good cosmetically although most of that is lost under powder coating. The main thing that I am going for is that a well executed weld produces the best possible joint strength.
Welding hotter and faster is actually the trick to making the heat affected zone smaller and getting a good smooth bead. The idea is to melt the base metal and the filler with an arc that is super hot and move fast enough that that areas of the tube outside the weld zone don’t have time to get hot.
I still have a long way to go before I am happy with my welding; today I spent some time practicing welding as hot and as fast. These welds are still not all that good but with time I think I will adapt to using a hotter arc.
Also, I am working towards a smooth application with a fairly fast pulse setting on the machine. Often we see the “stack of dimes” look in framebuilding but really each “dime” in a stack of dimes creates an uneven edge that can act as a stress concentration point (aka a stress riser). The strongest way to weld is to put down a fillet that is equal to the strength of the the tube and do so quickly and smoothly so the strength of the tube is not reduced by the input of heat. A correctly sized hot, fast, and smooth bead is stronger than an slow bead that has big fat “dimes”.
When welding a joint on a bicycle there are several places where the builder must stop and then restart the welding process. Often the joint must be welded in four to six short sections that must be connected together. Ideally the builder has a smooth hand and when they are complete it looks like he or she welded the entire joint in one pass.
I struggle to make the transitions in my welding. Often there is a pretty noticeable transition point and this is something that I am working on this year.
I am much better at this than I was last year but I still have a long way to go.