duanedr 

...test things by touch?? I have a bucket of standard size HT lugs - way more than I'll ever use. And I have been playing around with a driven die grinder and belt sander for shaping lugs and sleeves and fillets. I spent about 4 hours messing around yesterday and invariably after grinding a shape into a lug socket, I would mindlessly touch it to see if it was smooth!! I think I burned myself half a dozen times doing this!! I know it's hot, I can see it's smooth...WTF am I thinking?? Hopefully your weekend was less painful.

Here's a picture of a Steve Potts inspired segmented crown I'm working on for an upcoming gravel/all-road bike.
In Process:
by Duane Draper, on Flickr
Mostly Finished:
Untitled by Duane Draper, on Flickr
Here's my quality control guy making sure the brazing is up to snuff.
Untitled by Duane Draper, on Flickr

unterhausen

That was something Tony Shalhoub used to do in "Monk." If there was something he shouldn't touch, he would touch it. Always funny.

I inevitably burn myself when I'm doing a lot of brazing. Usually not because I grab it on purpose, but brushing up against it because my shop is small.

That's nice work, did you make any lugs you liked? I have been thinking about doing this, since there are no lugs I like for 1 1/8 steerer.

Andrew R Stewart 

Two touchy/feely stories:

When in was in 10th grade and taking Chemistry we were exposed to glass ware forming. Bunsen burners and all. The teacher said a few times to not touch the glass as it wouldn't look different whether hot or not. Of course I had to test this and got called out by him after. Social humiliation didn't do the trick as I still test touch stuff frequently.

There was a bike shop in the 1970s here that had a Austro Daimler Vent Noir (IIRC that was the name, black chromed frame) on display. It had a "do not touch" sign on it. It was usually covered in finger prints... I once asked the shop owner about the sign and all the fingerprints and he said they wanted people to touch it and figures that reverse phycology would work. It did. Andy

Nice work BTW.

duanedr 

Thanks, yes, I actually like these. They are somewhat traditional but not quite. There are some curves that I don't really like and wish the side tips were sharper. I don't think I'm great with makiing nice shapes like some are able to do. They started as press formed lugs.

I'm also playing around with what the right 'slip fit' feels like and how it helps brazing. I think I generally make the gaps too big which makes the shoreline difficult to get right. I haven't ever had anyone show me what a proper fit feels like so I figured I'd just go figure it out. I did a bunch of measuring to determine what like a .002" gap feels like and what a .005" feels like etc.

I still try to add the filler too early and get a bit dripping down the sides but the shorelines turned out mostly pretty good on these. It was also System 48 filler which flows just a little different than 56. The lugs I have are all 1" steerer and 1" top tube which is no longer fashionable. This was just a couple stubs and the head tube but I think I will turn it into a door handle for a sliding door we have in the house.

Playing around with shapes and slip fit. by Duane Draper, on Flickr
Playing around with shapes and slip fit. by Duane Draper, on Flickr

duanedr 

Thanks, as I was finishing up and wondering why I find it so irresistible to touch hot or sharp things, I was wondering if everyone who works with their hands does the same thing and then thought glassblowers probably don't. I could be wrong.

Andrew R Stewart 

The way I was described the slip fit for lugs is this- For a tight silver fit the lug should slide easily onto the tube with no catches. With the tube held vertically the lug stays put but a slight tap of the tube end on the bench top makes the lug slide a little bit. For brass/bronze the lug should slide down the tube due only to gravity and not want to stay put. Not really "scientific" but pretty much what I have used for decades. I also find that the longer the socket/sleeve the looser the fit works better for me.

I'm in the process of making a 531 frame influenced by the early 1970 Raleigh Pros and decided to use a "fish mouth" lug pattern, after the Haden version. I'll post photos when I have something cool to look at. But some of the lug pattern will be similar to what you just posted above. Nice work. Andy

duanedr 

Thanks, Exactly, I am trying to get a little more scientific with it so I learn the feel. Accurately measuring the inside diameter of a lug socket is trickier than it looks! And did you know tubes aren't perfectly round?!

I know I'm going way off the edge here. A few weeks ago, I stumbled across that chart showing the joint strength relative to the gap for brazed joint (we've all seen it). It got me curious as to what a 0.0015" gap feels like. This is where the strength peaks for silver. Then, like with any rabbit hole, it just keeps going. Looking forward to seeing your progress.

Andrew R Stewart 

One aspect of lug fit and filler strength that I have thought about for decades is that in my real lug fitting life the interface has tight spots and loose ones. So the "fit up" is more like an average and then what is the ability I have to flow filler through that average fit.

That second aspect, the ability to flow filler all the way through a joint, is what i have considered to be a bit more important than the gap and its influence of final joint strength. I have always thought that a lug's surface area of filler bonding is far greater than needed, based on perfect gap and filler strength. So in my world a lug is way overkill joint design and better to have a full fill then the max filler strength but a risk of less fill amount. Andy

duanedr 

Yes, the fact that you can't really get a perfectly round socket and the tube isn't perfectly round sort of messes with the whole idea. You end up chasing your tail even trying to measure one of them to 0.001"!

I found on Lucas Milhaupt or one of the brazing filler suppliers' site a formula to calculate how much overlap is required based on the filler, gap and base metal strengths and you're absolutely correct! I was amazed to find that the depth of the socket really only needs to be a couple mm all the way around to make the joint strength match the base metal strength. Then add in some tips, a belly and swoops and the whole joint is much stronger than the tube.

Andrew R Stewart 

Welders deal with fillet size as part of the joint details routinely, or so I have been told. For brass fillets a 4x or 3x the tube's wall thickness fillet size is enough, more and one gets a larger HAZ and smaller and the fillet is weaker than the tube. Yet the riding masses see large flowingly shaped fillets as a sign of a good frame... thanks Schwinn Andy

schwim

I don't have any useful input regarding the topic at hand but just wanted to say that you do beautiful work.

duanedr 

Thank you for saying that.