More Cowbell and Short Stays

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Jul 312012

How great was Marianne Vos’s Olympic Gold? First Wiggins hauls some major sideburn action into Paris and then Vos takes a brutal-looking rain-soaked women’s race in–if I’m not mistaken–a skinsuit. It was tough to explain to the kids why I was waving a cowbell at the TV.

It’s been one hell of a busy few weeks. The 2013 NoTubes catalog looks to finally be ready to head to print. I’d written parts of that all across the country, including a Holiday Inn laundry room., on the other hand, is just kicking into high gear in anticipation of a launch date that already can’t happen fast enough. It’s all been sufficiently panic-inducing to pull a guy off his pet personal project, which by necessity has to get whatever time I have left at the end of the day start of the next day.

Still, I was able to do a little reworking during my last round of PF30 conversion revisions. I wondered how short I could possible get the chainstays.

Now, there are a million and a half ways to cheat on chainstay length. My favorite is probably cranking up the bottom bracket height, but in Danzig’s case, that wasn’t an option. So the question becomes: how short can I get those chainstays for a bike with 29-inch wheels, a 12.77-inch bottom bracket height (can always go higher, but that’s as low as I’d go) and (let’s just figure) 130mm of travel. With some adjustments I went ahead and made, looks like Danzig might be able to drop chainstay length down below 17.4-inches.

That’s pretty short. It’s not a done deal, yet, but it’s close enough for me to say that’s now my target.

Thanks to Sugar Wheel Works and Digging into Axle Path

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Jul 302012

Thanks to Jude at Sugar Wheel Works, my old Independent Fabrications single-speed is slowly turning into a bike again. When NoTubes sent me some rims to help bring an old Industry Nine wheelset back from the dead, I was really looking forward to asking Jude to do the build. There’s just a great vibe to Sugar Wheel Works, which shares an enormous building with a bunch of other really interesting businesses. In addition to building wheels, Sugar Wheel Works also offers wheelbuilding classes. It’s a simple kind of business model–offer a service, plus classes on how to do it yourself–that seems to be growing. Only today I found out Carl Schlemowitz from Vicious Cycles is starting something similar with frame building and painting.

So the Indy Fab is on the way back to life. Now it’s down to sorting through boxes and trying to find the rest of the parts I need to finish piecing it together.

This weekend I also finished a pivot redesign on Project Danzig that relocated all the pivot points to allow for even more freedom of motion around the bottom bracket shell. The goal was to ensure ample room for PressFit 30 and similar bottom bracket diameters. In the process, I had to rebuild my main frame around the fresh pivot locations and recreate my axle path from the ground up (literally). Here’s an approximation of what it looks like right now.

We’ve looked at instant centers, axle paths and chains a bit, but one of the specific elements I’ve prioritized throughout all the iterations of this design has do with the relationship of the axle path to the chain. The drawing above illustrates my goal for the axle path.

How you arrange your pivots dictates not only how far rearward your axle can travel relative to its starting point, but at what point in the compression the axle is furthest away from the bike’s bottom bracket. As the axle travels upward, it has the opportunity to move rearward slightly. What I want with this design is for the point at which the axle is furthest away from the bottom bracket to be just past the sag point on the bike.

Why is that? Because chains aren’t elastic. Tension through the line of the chain will keep trying to pull the rear axle toward the bottom bracket shell. By designing a suspension system that needs to move rearward in order to keep compressing right at the point at which pedaling tries to pull the rear axle forward to counteract that rearward movement, the obvious goal is to cancel out pedaling forces. We’re talking halves of millimeters in some cases, but the objective is to turn the chain force into a positive when it comes to eliminating pedal bob.

Factor in the much larger wheels of a 29er or 650b bike, and it can become more challenging to align those two. It was a need to create a longer travel 29er that still had short chainstays that led me to design a frame in the first place. Going forward, I’ll try to explain a little more about the challenges of a bike with larger wheels, how axle path gets involved in all this, and how that led me to design this system.

Monkey-approved Kids’ Bikes and Danzig PF30

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Jul 272012

I have to come up with some bikes for my kids. Actually the girl child has a pretty badass little 24-inch Santa Cruz I concocted based on an idea I got from framebuilder and ultimate bike-for-the-kids-creator Jeff Jones. The boys need at least one new bike, though, and I wish I could find something that looks pretty much exactly like that monkey’s bike.

I’m serious. Why doesn’t anybody make like a kids bike with larger wheels, but small crank arms–like 145mm? That’s sort of what I did with the Santa Cruz, and it makes perfect sense. Bikes like that are ultra-stable thanks to the whole sitting “in” the bike with some bigger wheels up around you (you’re basically creating a scaled down 29er in that regard), but everything else is kid-size. So there’s that on the agenda, if I ever get my garage finished.

I spent most of yesterday writing product descriptions, put in what felt like my weakest ride all year to get home, wrestled Facebook in a professional capacity (just like wrestling it for fun, except for the company issued luchador mask), then wrote some javascript to help make a site compatible with iPads. That last one is positively insane, as I haven’t written any genuine javascript functions in over a year. It was a little like meeting an old friend who no longer speaks the same language, and trying to build an airplane together out of shit you found behind a Radio Shack.

Oh, what Javascript and I had been through together! And to think now we barely know one another. I’m so happy with it that way.

Anyway, I seem to’ve found a little extra in the tank to crank out this Danzig redesign. I’m happy to report that after obsessing about pivot locations on my ride into work this morning, and on my sorry excuse for a ride home, it occurred to me that I can generate plenty of space for a PF30, or a PF50, or whatever the hell massive oversized beast becomes the next standard.

The nice thing about the relocation is that it also makes the frame easier to build. The key was a proportional move up and back for the lower pivot. Here’s Danzig PF30.

Remember yesterday when we looked at instant centers and how their vertical position affected axle path? Maybe it didn’t sound like that yesterday, but the bit about the higher the instant center the move rearward the axle path would be–that stuff? It turns out that axle path is my guiding principle when I’m moving my pivot locations. Right or wrong, there’s a set of criteria I’m following that dictates my axle path, and that range is what dictates my pivot locations. Using more goofy graphics and animations, I plan to dig into that next week.

Commute-aways and Fun with Circles

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Jul 262012

It was 84-degrees for the ride home from work today, but just when I was due to shave my head again, this guy robs a Portland video store of its prized classic movie guns and escapes on a bicycle. By 2015, Portland’s goal is to have 30% of all robbery escapes occur by bicycle.

My own theory, based on his facial expression in that photo, is that this guy just really needed to use a bathroom and, finding no public toilet in the video store, stole the gun to put himself out of his misery.

So Danzig. When I started work on this frame, there was no such thing as BB30 or Press-fit 30. The original design was built around a conventional English bottom bracket. Though it looks like the original pivot configuration will work with an oversized bottom bracket, I’ve started to look at optimizing around a much larger diameter bottom bracket shell.

This means adjusting the lower pivot orientation, which is what I was up to late last night.

In case anybody’s curious, raising the lower pivot location kicks the axle path back further initially. This makes sense if you imagine your instant center–the middle of your pivots’ rotation–as the center of a giant circle. The higher up you move the instant center, the higher up you move the whole circle. And the higher the circle, the more your axle kicks backward during that phase of the travel. Here’s a better view of the same image that probably won’t make any of this any clearer, but what the hell. Everyone likes circles.

The red circle is our original pivot center. The blue circle is the revised, higher pivot. The green arrows represent how the height of those circles affects the shape of the axle path. Your axle path is only a slice of pie cut out of that circle. Where you cut it changes how the bike pedals and rides. Completely. Important pie.

So that’s what I’m pissing with currently. Axle path–our slice of the circle–is also directly related to the force of the chain that’s trying to pull the bike together. If I find some magic extra horsepower to stay up late again tomorrow night, and if I’m not arrested for robbing a video store or run down by a perp pulling a daring recumbent getaway in North Portland, we’ll add that force to our circles.

New Pivots All Around

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Jul 252012

Pivot released images of some pretty wild new frames today, including the new Mach 429 Carbon (above) and the Pivot Les hardtail. Impressive as the much anticipated 429 Carbon is, the modular drops on the Les are really intriguing. You can click through the photos for more info.

On the subject of new pivots, I’m definitely back off the Solidworks wagon. After taking some time away from it, I’m definitely back in and I have to say, I love this stuff. I’m going to sound like an ad for the software, but Solidworks is just scary powerful. What you can do with physical spaces in this program is just incredible.

None of this is helping me out right now, though. I have what I need to complete this next phase and be able to create an entirely new 3D model, but I’m obsessed with optimizing the spaces between things here. And so I draw. And redraw, and redraw again.

I’m convinced there’s a way to simplify the new Crankcase (the bottom bracket shell/pivot box) even more. That’s what I’m working on right now.

Feel the Burns and Fresh Drawlings

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Jul 242012

Anyone who gets a chance, please check out the new Stan’s NoTubes Featured Builders page and let me know if it’s displaying OK in whatever browser you’re using. It’s just a basic page, but Stan’s has supported small builders for so long, and the rims and wheels have been a staple of builders at NAHBS, so it only seemed right to give frame builders some space right on the site.

In other news, I’m not blind to the fact that the Tour de France just happened. In fact, I’m keenly aware that history was made–and frankly, it’s about time somebody with Marty Feldman-inspired facial hair brought home the maillot jaune.

Long a fixture on the endurance MTB scene, ’70s comedian manscaping sensibilities have finally won the big one.

I’m also keenly aware of other things. I know, for instance, that I’m teetering dangerously on the verge of too much sleep. In an attempt to put an end to that nonsense, last night I dusted off my sorry Solidworks chops and began a major redraw of Danzig’s mainframe that accommodates the latest shock orientation. There’s a lot left to draw, extrude and carve holes through–and completely rework–but here’s the first draft. Slowly the latest 2D design is creeping on into 3D. Note the shock mount down there by the bottom bracket shell.

(“I’m way more vertical.”)

More as I draw it.

Going Vertical and Krampus Worship

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Jul 232012

Bike build area in the new house is starting to come together. Still plenty of work to go around, but I managed to make some progress this weekend. Also found some time to build a new upper link for the vertical shock placement on Project Danzig.

Last week I tried to explain what I was thinking in the development of Danzig’s instant center, which starts right at the intersection of the chain and middle ring and travels largely backward, along the path of the chain.

There’s also a set of reasons that went into the axle path and the final shock orientation of the frame. After endless hours trying to model exactly what I wanted out of the rear axle, I finally dialed it in using a few simple pieces of paper. In locating the instant center primarily behind the center of the bottom bracket, the swingarm rotates almost on its own center. This allows some pretty interesting shock placement options, but my favorite is the vertical shock. Because the swingarm nearly pivots on its own center, the upper link can drive the shock straight down. I hope to be able to redraw some of this over the coming weeks, but what I like about it is the inherent simplicity. Really short links mean less weight, but also economy of motion. Economy of motion was something I really hoped to build into the design. The vertical shock orientation also means the bottom of the shock anchors right beside the bottom bracket, an inherently strong area.

Really, it’ll take the prototype to see how all of this works out, but I suspect developing anything like this is a matter of balancing all the things you want, and I was really happy with the way all the characteristics seemed to work together on the design. The pivot placement that kept the instant center where I wanted it also led to the axle path; the axle path led to the economical upper link and shock motion and location.

Times like this I wish I were a much faster Solidworks user, instead of a self-taught hack. I’d love to be able to redraw Danzig from the ground up at this point, and I guess that’s what I’m doing while we work to put everything else in place.

In the meantime, I’ve been more than a little unhealthily fixated on Surly’s Krampus.

And how great that the first decent Krampus sightings seem to’ve come from Tae’s blog. (A finer gentleman, you will not find.)

Krampus is so much more than just a 29er with 3-inch wide tires. It’s a reassertion of Surly’s dominance in the realm of blowing minds. Once again, Surly has made the world a little better.

Wayward Watermelon, Simply Irresistible Clones and Danzig Rising

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Jul 202012

My body’s starting to ask some tough questions about this whole commuting thing. I’ve ridden a bike to work for years now, but that was all chickenshit. Chicago’s winter was no fun, but I was only a few miles from work. Same thing with my first months in Portland. But the new dozen miles one way thing is a whole different kettle of fish. And sometimes watermelons.

So far, this that watermelon is the weirdest thing I’ve seen thrown from the 205 bridge. So far.

I’m writing a lot of product copy right now, and my research seems to be teaching me more about web sites than products. I’ve noticed, for instance that every sites offering live chat pretty much use pictures of the same dozen women wearing phone headsets. In fact, I believe that the entire female cast from the “Simply Irresistible” video now does web chat support.

OK, so yesterday I seem to’ve been typing something about Danzig’s instant center. To wrap that up, here’s the full migration of the IC from unladen to just under five inches of travel.

Not my best hasty animation, but should be good enough to give you the idea. It all comes down to this: the orientation of Danzig’s lower linkage tracks along the line of the chain as the rear wheel moves upward relative to the chain’s fixed point on the chainring. In other words, the instant center stays exactly along or very close to the line of torque (the chain) throughout most of the travel. What the hell does that do? Who knows until we actually ride prototypes, but it would stand to reason that maintaining an instant center that tracks along with the line of torque could be very desirable traits. Because the instant center stays so particularly focused right on a relatively small area throughout the entire first three inches of travel, and because it’s orientation is so particularly vertical, the system should be more consistent in all gear combinations, too–that’s just one of those obsessive details I tried to accommodate in the design.

That’s a pretty magnified look at only one tiny aspect of the system. Any suggestions or questions about other aspects, just let me know, and I’ll do my best to answer all questions. More next week.

Past, Present, Future

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Jul 192012

So I’m thinking about this unused part of the new house as my Secret Bike Lair. Multiple platforms give it a certain “really small punk show” vibe. Some of you will recognize that one bike as one of the first full-suspension 29ers ever made. Hell, it might be the first full-suspension 29er, though I’m sure someone built one in a garage in 1976 or so. It arrived from PA last night, and I unpacked it from a travel case after work this afternoon. Rhyno Lite 36-hole polished 29er rims, bitches. That’s how we rolled like a decade ago.

Gonna need to change that decal.

If that’s a bit from my past, my present is looking like one long night. I’d promised a deeper analysis of Danzig’s lower link and instant center for you today, but of course that was before I got hit with some late night gainful employment encroachment before writing this entry last night. As I type this now, it’s pretty damn late, and the better part of the day’s already worked me over pretty good. The whole “suspension analysis” thing takes a while to explain, and probably isn’t best done when you’re as groggy as I am right now, but a promise is a promise.

Come to think of it, I didn’t actually promise, but whatever.

So if any of what I’d written yesterday was coherent, you know that the orientation of Danzig’s lower link is opposite that of just about every other bike made. What’s that mean exactly? It means the swingarm connects to the rocker forward of the main frame’s connection. Here’s a cutaway from the patent.

Project Danzig Lower Link Orientation

Yesterday, I pinpointed the unladen instant center, and may have even explained what an instant center was. I also mentioned the importance of the line the chain makes between gears as it drives the bike along. This is important because that chain is essentially trying to pull those gears toward one another, and that’s a force that has a distinct effect on the suspension system.

Basically, my instant center–like most–aligns right at the point the chain would engage the middle ring. It’s probably the worst-kept secret out there that all full-suspension bikes are optimized for a handful of gears and not for others. Ride around in the granny ring on any full-suspension bike, and you all but feel an engineer cringing.

This isn’t to say bikes don’t work in other gear combinations–they do–but eventually you have to nail down pivot locations and all the combinations of a triple and 11-34t rear cassette are going to create more possible distinct optimal locations that you can possibly cover. So you average. Everyone basically goes with the point at which the chain intersects the middle ring, because that’s what you’re in most often. Luckily, the stuff that causes deviations when you’re in, say, the granny ring, tends to benefit climbing anyway, so life damn near works itself out when it comes to that. Dave Weagle has a phenomenal analysis of why triples actually saved full-suspension bikes from going extinct (or something like that–it’s somewhere out there on the interwebs, if you want to Google Dave’s name and “triples” or something).

So Danzig, unladen, has an instant center sitting right at that sweet spot. But, hey dumbass, you’re thinking, that’s unladen. The minute somebody sags that thing where’s your instant center go then? It can’t stay there.

Right you are.

Where Danzig’s instant center goes is backward, right along the line of the chain.

What the hell does that have to do with anything? We’ll kick that around tomorrow. Probably. No promises.

2D Suspensions and Fun with Instant Centers

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Jul 182012

Hank Matheson from Bicycle Fabrications let Dirt Rag take the wraps off his wild new “2D” suspension system today, and bravo. It’s sufficiently bizarre to have warranted the cloak and dagger. I love that it’s part homage to the old Cannondale Gemini DH frame, and that it’s legitimately something completely different.

Matheson developed it with engineer John Heim, and the truly unique thing about it is the axle path–or really axle paths. The suspension moves vertically, but it also moves horizontally. Square-edged hits allow the rear triangle to kick backward up to 19mm. The whole thing pivots on a large eccentric, so essentially it’s a single pivot on a pivot. The large eccentric onto which the swingarm pivot mounts can rock backward, and that motion’s controlled by a giant elastomer.

I have to admit I’m always a little envious of DH frames because there’s just so much you can do with them. You just don’t have the same chain growth and gear combination concerns.

Today’s Danzig detail deals with instant centers and gear combinations. Draw a line through the pivots of each of your rockers, find the place where those two imaginary lines cross paths, and you have your instant center. Unlike a single-pivot frame that has a fixed instant center, frames with multiple pivots have instant centers that move around. Where that instant center is relative to the chain you’re pulling along between your chainring and whatever cog you’re in dictates how the suspension behaves. Here it gets a little hairy, but the bottom line is that it’s desirable to build a happy relationship between that instant center point and the “line of torque,” i.e. your chain.

A key aspect of the Danzig design is the position of the lower link and how it affects that moving instant center’s relationship with the chain. Danzig’s lower link is basically the mirror opposite of every other lower link orientation out there. This orientation doesn’t just put the instant center right on the line of torque. The way the pivot rotates actually tracks alone with the line of torque as your wheel raises.

Clear as mud, right? For now, here’s the resting point of the instant center (the red dot). Next, I’ll blow out some other drawings so we can look at where it goes when the suspension is compressed and why I worked hard to get it to do that.