Aero frame & fork

Posted on November 23rd, 2008 by admin under Bikes.
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As promised, I’ve reunited frame and fork of a frame set that I always liked. It, unfortunately, never reached it’s possible potential. The rider, while on a Sunday training ride (his road bike) with the T-town guys, either crashed on his own or was helped ( I like to always add some speculation). So, his Olympic Pursuit trial the following day  was done in a good deal of pain. The bright spot, I guess, is that he managed a 6th in the Points race later in the week, which is all the more tribute to the rider and what is clearly not the best choice of bike for that event. It went to State track finals last year (2010), but was viewed in a poor light by the commissar’s. I was told that it “spanked” a lot of newer and lighter equipment. That is pretty reliable hearsay.

Here’s the general idea. It is Columbus EGO tubing. Mostly wing shaped. The chain stays, as I recall, were available in a couple of different shapes. I choose to use the triangular and have the fattest  side up, so it would help with the chokes, (actually these are venturis-note the cable guide air intakes on stays and the “calibrated” air jets in the choke tubes. Got to love those fat seat stays, even when they’re upside down.

It has a 101cm wheelbase, 77 degree seat, 74 degree head tube, 1.5″ rake (for stable steering on the measurement line) and a 10″ BB height.

These stays are wonderful for track use. They are so stiff, I was able to get the wheel very close to enhance the chokes effectiveness but, not worry that frame flex would cause tire rub. Luckily, that’s not much of an issue on a relatively smooth track. The tire shown is not original. We used Falcon ACCEL stretched Kevlar wheels with Continental Olympic tires.

Everything was done to keep the frontal presentation to the wind to a minimum. The top tube was kept as flat (parallel to ground) to decrease frontal area as the overall seat length would permit under a powerful rider. This is a constant in my racing designs, where the stays and top top rarely meet at the same point on the seat tube.

Here’s one of the old 60mm hubs. A Suntour Superbe. Double discs were used for the actual event.

Here’s the skinny frontal area. This has always troubled me some. Is it better to widen the spacing and just let the air pass through or close it down and use mechanical means to control drag?

This is the “business end” shot of the multi-choke concept. By the way, inserting tubes through tubes like this makes for a really stiff fork and decreases splaying in hard turns, Be careful if you try this, though. It can pull the insertion welds apart if you don’t use the right stuff, and I’m not giving any of those secrets away to my competitors. This one is illegal nowadays, so copy away if you want.

One can see the “calibrated” holes inside the chokes and the air inlets behind the BB shell. Well, they were, looks like some rust has changed the shape a bit.. It was painted black to help hide some of the trickery. Too bad because black looks heavy. A nice light blue metallic always helps the rider psychologically.

Well that’s about it. Have at it guys. Show me your better mouse trap. Incidentally, the frame was nicknamed “Squirt”  in reference to, well, one more squirt, if you get the drift…

One more caveat, This sort of bike is not for the casual customer. To make the details function, the bike must be ridden at over 28MPH.  Turbulent air starts at about 60MPH. So, that means at least 30MPH to get turbulence at the top of the spinning wheel.  I can just manage 26-27MPH for a couple of miles with someone chasing me. Not my cup of tea anymore. I should clarify a bit here, air can be turbulent at lower speeds, but it can remain laminar or in contact with the frame up to 60-ish MPH. All you theorists will argue that point , but my source was one of the smartest Indy car designers ever. I trusted him then and now, so get over it.. ;~)

Hope you enjoyed the pictures and oh, I’m working towards another unique frame set for a rather obscure record attempt. Know any really strong riders? See “new tandem project” herein..

Dave 11/23/08

Here’s another in the same vein. It has 45 holes through various and sundry locations. This was one of the, “well let’s just let the air pass though” versions. There’s another around here somewhere that had an eccentric BB so we could change the relative seat angle. I think that Kent Bostick’s wife set a Kilo record with it but the guys never liked it too much.. I’ll dig it out anon.


  1. Steff Says:

    That’s a fascinating frame. Great to see a “science” bike that isn’t made of high-modulus unobtainum with aerospace kevlar weave.

  2. Dave Says:

    I wish I had more precise empirical data. During the time it was in it’s conception stages the National Lab at Los Alamos had a program wherein they would assist private sector companies. When presented with my ideas for controlling boundary layer on a rotating wheel, they found that they were unable to accurately model all the variables associated with a bicycle moving through the wind. I suspect that with better and faster computers that they could probably address this better some 12 years later. I always found it ironic that we could put a man on the moon, but they couldn’t figure out a bicycle…

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