How are the Director dropouts held together

I did a post a few days ago listing the Director patent. It was chalk full of interesting stuff. But the question quickly came up: How is the dropout insert held in place. The drawings show a seam weld, but those don't appear on production models. Eggit helped clear it up with some rawing and bluing of his:

Dropout insert from patent


Eggit's photos show spot welds holding it together


Edit: Comment from G

No spot welds.

Read the patent, look at fig 5 and item 67 in particular...

G.

Director Patent and Construction

I was pleasantly surprised to find this in my Google Reader list this morning. If you don't know about Reader, it is a web based application for aggregating RSS feeds, updated search results, and other periodicals. The recommendation and searching functions are pretty good, but some of the BMX RSS feeds are surrounded by noise (i.e. one good feed with a bunch of dead ones).


Director Forks have interested me since they were first unveiled. Integrating the dropouts with the fork legs is a logical step that was taken by road and some mountain quite a while ago. Eliminating the weld at the dropout avoids cracks there as well. And using a simple insert gives good compression support, while maintaining a hollow dropout for weight. Overall a nice design. Unfortunately, since this is included in the patent, any other company who wishes to go the integrated dropout route will have to find a manufacturing method that does not violate George's patent.

The crown junction is another unique feature of the directors (unless you look at sunday's chainstay wishbone that G had a hand in as well). The claim is that it reduces localized stress and extra material found in conventional open ended steerers.

I'll dig into this deeper after some discussion, but I really have to head off to class, so this simple post is all that is going up for now :)



Some random feeds I subscribe to (post yours up!):

- Bicycle Design is not updated all that often, but can be interesting.

- Sweeter Skins for those of you with Android phones, this is really the future in UI.

- Roues Artisanales mostly posts in French about the road bike weight weenie scene.

- Cool Tools updates often with some neat little productivity tools.

- Scheier on Security is one of my favorite blogs. Written by a security expert who is often contacted to comment on security issues by media, government, and private agencies. He takes a very logical approach to dissecting issues. His post "Fear and Over-reaction" really struck a chord in me.

- Google Patent "Bicycle" Search feed updates every so often with new results (usually patent applications or updates). You can use Google patents to get customized results.

- Endless Innovation has some good posts, but can be a bit repetitive at times.

- Physics World has some neat, informative updates about research findings in classical, relativistic, and quantum physics.

- The Big Picture has great photography, and is updated very regularly. Each post contains a link to 40 high-def photos about a certain topic.

- F-Secure has regular, detailed computer security reports.

- Cycling Tech hasn't been updated in 2 months, but it has some cool stuff when they do.

- Industrial Design has a lot of design *cough* Crap *cough*, but you can find some real gems in there. Be weary of hub-less bicycles, there is a reason they haven't gone to production.

- Ted Talks are a great way to look at a situation from a particular (speaker's) perspective. They are all free videos on a very wide range of topics.

Shadow Torrid V2 Cranks

Flipping through Dan's I saw the shadow Torrid cranks. Now I realize these are not new, but they are interesting. If you take a look at the patent for it, they originally designed the crank to use a chromoly spine (4140 not specified), with an aluminum shell. I'm not sure if they ever made this in a production run, but there are a few reasons why this is not necessarily a good idea:

• Different materials have different properties. Specifically, they have different elasticity, and different rates of thermal expansion.
• Joining (welding) dissimilar materials is difficult. Although there are filler materials available for joining Aluminum and Steel, but they make structural sacrafices in order to get proper fusion of both materials.
• There is no purpose in using two materials. Profile and the new Torrids show how steel is enough on its own.

Now the current version of the Torrid cranks use a 4140 spine and a 4130 shell... Again, I am not so sure this is really necessary, or even advantageous. We can't really know what their goal in using different materials is. However, we can speculate they wanted the stiffness of 4140. I assume they weld the shell to the spine along the ridge, which would stiffen the whole structure by making virtually the whole crank a heat affected zone. Well they could post weld heat treat (anneal), as all welded components should be, but I would assume they would market that as well.

After running a few circles, where are we? Boasting that it is patented, the use of two parts, and two materials, all makes me weary this is mostly just marketing. Does that mean they are crap and will break? No, not at all. But if we are to aim for the highest strength to weight ratio, this design is probably not the way to go.