Thanks for the question. I learned using a Miller machine and my settings were as follows (with some variables based on what parts I was welding):
Pulsing Unit set as follows:
Peak Amp: 60
Background Amp: 20
Pulses/sec: anywhere from 3.5-7, depending on the finish or what music is playing :)
% on time: 37
Main Power set to 150 Amps (though you'll never use that on a bike frame)...
Now I've got a Cebora machine and I just put the heat setting to full-blast, similar to the base power as demonstrated above. I set the machine with a quick arc up-slope and control everything with the pedal. I've settled on an average pulse frequency of about 4 or so and will sometimes lay the root passes w/o the pulsing to keep in touch with my dabbing technique.
Does that answer your question? If not, keep trying and I'll see if I can zero-in on what you're looking for. I've also posted some info on The Framebuilders' Collective website which might also be useful to you if working with ti. Remember that your welding style will also play a big part in how you setup your machine, so don't think this is the only way to do things. If it doesn't work or if you find that some adjustments need to be made, by all means make those changes.
A snowy shop, for sure! Very cold (for me). Have a look HERE.
I love the silence and beauty of the snow. It is amazing. This sensation unfortunately passes quickly when I realize that ALL the shops (my local suppliers) will be closed for the next week and I lose power about every 10 minutes. They've also closed the road that leads to my house.
It does make me think of that Lenny Kravitz song.."Where Are We Runnin'?" It's good to hear the silence...
you are currently building a frame for me. When I received the pictures you sent me today, I became curious to hear more about your rationale for using a double pass technique. I know that some builders/production houses don't use this technique. Could you talk a bit about how you arrived at this way of doing things? And how do you think it distinguishes your work from those builders who don't?
By the way, I can say to all that Darren has been a true pleasure to deal with since I sent him the initial email. Always responsive, always understanding. I am incredibly excited to receive the mtn bike, and feel grateful already for having put my name in your queue.
Thank you, and best wishes, Joel
You're PR check is in the mail, thanks! :)
Seriously though, thanks for the questions and for your kind words. The subject of welding can get pretty deep into the specifics, but I'll simplify my view of these two processes so as to not bore you.
When I started building with ti in 2001 I was using a single pass. This type of construction typically calls for a larger diameter welding rod. When the tubes are mitered and fitted, ready for the weld, the operator passes with a (proportionally) high amount of heat (amperage) to get the rod to melt onto the work. Depending on the technique used (specific to bike frames) it is usually the rod/weldment that is the providing the dominant fusion between the tubes. With a two-pass method, the "root" pass (no welding rod) actually makes certain the the mitered tubes are "fused" together; allowing a sure joining of the tubes as the miters have to be tight and perfect. Any air/gaps will result in blown holes and insufficient material to fuse the tubes together.
Some quick characteristics of the two styles:
- Less precision needed for mitered tubes
- Less probability of contamination
- Better fusion/penetration characteristics
- Better weld flow/smoother finish
- Lower heat
- Easier to sequence welds
There are some other differences between the two styles, but these are the ones that I consider the most important, especially to my fabrication procedure. Like I said, I started out with one-pass. But as time wore on, I realized that I preferred making a complete root pass which allowed me to sequence my welding as I pleased. This was helpful with my alignment protocol. With one pass, you get one shot to get the frame "into" alignment, otherwise you're cold-setting to a finish-welded frame. Once the root pass is on the frame and it is aligned, it is pretty difficult to take it out of alignment when laying the second pass. Doing this allows me to work out the sequencing and alignment in the root pass, then concentrate on the "perty" welds with the dress pass which also serves to add material and strength to the frame.
When I was welding with only one pass, I didn't like the noticable start/stop areas which were dictated by my sequence. There are fabricators who prefer to do the 1-pass method and some do it really well. I just prefer to take the extra time (you're actually doubling your welding time), keep the heat low, and have better control of the outcome.
If you look at some of the higher production frames, they are almost always one-pass welds. This is evident by the larger weld bead and less refined/smoother finish of the weld. This allows for quicker production and lower labor costs.
I'm glad you're enjoying the project. I'll have some more pics for you tomorrow. I appreciate the trust you've put in me and my product and for the kind words. It has been just as enjoyable for me to be able to collaborate with you on your new frame and I can't wait to get it in your hands.
Thank you for everything you have said, Darren. It is very interesting to hear how and why you have chosen the two-pass technique.
In the course of our conversations I tossed out some ideas and you very gently steered me back on the path of reason and well-constructed bicycles. I greatly appreciated the tact with which you did this.
So in light of my own highly enjoyable experience:
Have you ever told a customer outright that he or she is making a mistake?
Are you ever pained to see what a customer makes of a frame you have built once he or she puts the fork, components, etc on it?
And one final question: what is your view of the recent, largely American trend toward more all-rounder bikes? Is this a genuine niche that should be filled?
Thank you for your time.
As for the above, I did notice one error..
"If you look at some of the higher production frames, they are almost always one-pass welds. This is evident by the larger weld bead and less refined/smoother finish of the weld. This allows for quicker production and lower labor costs."
Should read "less refined/less smooth finish"...sorry if that was confusing..
Sure, I've told many a person what I think. That's part of my job, so to speak. If I didn't, and just built whatever comes down the pipe, I'd probably be out of business by now. Anybody can draw out a ti bike on paper and have it fabricated remotely, so I like to add value to my craft and one component of this value is my experience of building and riding. I've learned that some guidance may be necessary, even with folks who have years of experience on the bike. This may be due to the fact that they are transitioning from another material, have some postural problems, or they just may be in need of some insight regarding their ideal project. I don't claim to have all the answers, but if I can add to the conversation in a constructive way, the collaboration has a much better result.
Like I've said around the way, I appreciate the fact that I've been chosen to collaborate on the project. People spend a good bit of $$ on bikes and if somebody chooses Crisp for their new frame, I take that seriously.That's a lot of would-be grocery money out the door. I don't want their new frame to end up in the back part of the garage because things weren't developed as they should have been.
It also opens up another idea of "how much" of the fingerprint should the builder have on the project. I think it's a pretty interesting subject on a conceptual level. I have some folks who bring pretty wild projects to me. Some I make, others I feel the need to put them in touch with other builders. When does a builder feel like he's reached a level of experience that gives him the confidence to make those important decisions that deviate from the original concept? Not sure about that, but it's pretty easy to see what will not work as opposed to offering up the bold ideas.
Have I ever pained to see what a customer makes of my frame? Sure, I've seen some pretty nasty looking parts being used. Nasty not only because they may detract from the overall look of the frame, but more so because of the quality and construction. A few years ago I started selling my road frames as a frameset (frame/headset/fork) so when the client received the work, we were both confident about those important parts and their interface. That allows me the both of us to better understand in a quantifiable way what the outcome will be when the rubber hits the road. On the mtb end, there is a lot more going on there and things are more dynamic so tolerances and feel can vary greatly. In the end, it's the customer's dream bike, not mine. So I have to step back and let their dream be fulfilled. I'm fulfilling mine by being allowed to participate in their project.
RE: the All-rounder bike. That's a really good question. I think that it is smart to plan ahead and try to build some intrinsic elasticity into the design. If the project requires a certain type of drive train, I like to incorporate dimensions that will put minimal limit on component choice. There's nothing worse than being obsolete in 4-5 years with a project that is designed to be the "last" bike you'll ever need. Saying that, I think that some folks are going a little overboard with the requests, trying to pack a bit much into one design. There are some limits as to what you can build into a frame. I like to be up front about what those expectations are and clear about what the limitations may be. Some of those characteristics overlap and when they can, I like to implement them into the design if possible. On the other hand, I'm pretty direct if I see that there could be conflict. So to answer the question, no, I don't think it is a niche that can or will be filled.