On tube bending

A local company is trying to bend some 3/4" 4130 tubing to use as stays on BMX frames. I hope to help them make this happen.

I did a little research on this and found this page about bending tubing for recumbents:

Apparently, bends become difficult or impossible when
( tube diameter / wall thickness )
exceeds 20 : 1.

The .75" x .035" wall tube they've been experimenting with has a ratio of 21.4 : 1, which has led to serious crinkling.

So I will recommend either decreasing tube diameter, like to 5/8":
5/8" (.625") x .035" wall = 17.9 : 1

or, better yet, increasing wall thickness, like to .049":
.75" x .049" wall = 15.3 : 1

Of course, changing this tube spec will affect the frame design. Larger-diameter, thinner-walled tubing is generally stiffer (up to a point) than smaller-diameter, thicker-walled tubing.

Furthermore, bends become difficult or impossible when
( bending diameter / tubing diameter )
is below 8 : 1.

Hence .75" tubing ought to be bent on at least a 3" radius mandrel, which is pretty reasonable. A fork blade bent around a 6" radius is considered "tight".

And of course, the bending rig should accommodate the tubing as described in the link above: good rigidity, mandrels shaped to fit the tube closely, etc.

Consumers Are Consuming Raw Materials

Then in the middle of a "Manufacturing Processes" lecture, the prof said something about how, as opposed to manufacturers, consumers don't consume raw materials.

I perked right up. I'm a consumer, I thought to myself, and I consume raw materials all the time.

Moreover, the resurgence of craft in the US* has redefined what it means to be a consumer.

cf. MAKE magazine, steampunk, TechShop & The Crucible, hobbyist/amateur frame builders, this WIRED article mentioned previously, and even The Whole Earth Catalog

These "crafters 2.0" are consuming raw and semi-raw materials (as well as scrap materials, even better). They're a different kind of consumer.

It's a niche, but thanks to The Long Tail, it's a valuable niche.


This way of consuming smacks of a bygone age, when a family used what nature provided to produce what they needed to survive.

The settlers who populated the American frontier didn't head to Wal-Mart to stock the wagon on their way out of town. There was no all-inclusive, Chinese-made, Frontier-Settling Kit.

They processed the raw resources around them, and they used those resources completely, wasting little.

They manufactured on-site a lot of what they needed: a house, a plow, leather goods, clothing, food. Manufactured goods were expensive before mass production, so it was cheaper to make rather than buy.

Perhaps I'm being sentimental.

But I wonder what can be learned from these frontier ancestors. The best of them were tough, innovative, self-sufficient, and hard-working.

Rant/Rave: Online TV ads


I've been watching the TV series Lost via abc.com (highly recommended, but addictive). They have these online ads in between acts of the show. One of them if for Discover card and goes something like this:

"We're a nation of consumers... And there's nothing wrong with that..."

And then it goes on about how we should all get Discover cards so we can be better consumers, manage our debt better, etc.

The thing is...there's a lot wrong with that.


Also, seriously, people, if you're going to pay for ad time on an online TV show, have the decency not to run the same annoying ad over and over. It makes me hate you.

I'm looking at you, Pfizer, with your fybromyalgia medicines. And you, Blackberry, with your catchy but repetitive jingle-video.

The best ad series, which rarely comes on, was from Epson. They were 30-second spots interspersed throughout the episode, each different but all showing a couple talking about printers in a funny way.

This was great. This made me like Epson. Please be like Epson, everybody.