Sunday, February 16, 2020

Plan 2020 - Dolan DF4 Frame

The first step in the whole process was to get a frame. Track frames are different from road frames, and I'd want the frame to be UCI compliant as well, something my beloved Tsunamis are not.

Here's the big thing with track frames: the bars are really narrow.

Wait. Bars? You were talking about frames. Why the bar comment?

It all comes down to that. Nowadays a regular track bar is 33-35 cm wide. In contrast, on the road it's normal to see 40-42 cm, although that's coming down a bit. I'm running 41 cm bars on my Tsunamis, and they look narrow under me.

The ultra narrow track bars cause a problem though. The reach to the bar is shorter, due to the reduced width. If you're reaching 3 cm to each side that's 3 cm of length. If your bars are 3 cm narrower on each side, you have 3 cm more arm "left over".

You need a longer frame.

Therein lies the problem for me. I'm already pushing it with my odd proportions, short legs, long torso. My frame is basically a 50 cm (high) frame, a size which normally comes with a 52-53 cm long top tube. However my frame has a 56.5 cm top tube, and, additionally, has a steeper seat tube angle. That pushes the top tube forward, effectively making it about a 57-57.5 cm top tube. And my head tube, at 12 cm total height, requires a 3 cm drop stem.

I can't commission another Tsunami because they're not UCI compliant.

So I Googled all the track frames I could find. I looked at their frame geometry charts. I needed to find a UCI compliant 50 cm seat tube frame with a 74.5-75 deg seat tube angle, a 57 cm top tube, and a 12 cm head tube. It had to be aero. It had to be a real track frame, not a fixie bike.

And I needed to get it done for less than $2000 shipped.

Dolan DF4

The only frame I could find was the Dolan DF4. A world class frame, no less, raced professionally. Aero design. 50 cm seat tube. 57 cm top tube. 74.5 deg seat tube angle. 12 cm head tube.

It was exactly what I needed.

And with a pre-season discount, it fell way below my $2000 budget, shipped.

Dolan DF4 - size 57 (!!)
It's their second largest size frame.

First, the frame is UCI certified. That means I can do official events, like Worlds. At the very least I know that the frame is okay for Nationals, which is my focus.

The second most important feature of the frame is the geometry - it almost mirrors the Tsunamis. Very long top tube (0.5 cm longer), steep seat tube (1 deg shallower), and short head tube (same height as Tsunami). Although I'll have to move my saddle up within the seat post clamp, I'm at the UCI limit on the Tsunami for a sprint bike (zero setback to nose of saddle) so I should be fine on the Dolan.

The third most important feature, because without it I'd have eliminated it from consideration, is that it is aero. No vintage round tube stuff - this frame is meant to go fast.

After that it's all gravy.

Aero tubing, aero seat post

The aero isn't obvious until you turn the frame. The frame gets real thin real quick.

Cut out for rear tire, but tire will not be as close as on the Tsunami

In my research I've found evidence that a cut out will save a fraction of time, and help a less than optimal rear wheel. In less scientific findings, I think it looks cool. Either way, this frame has a rear wheel cut out.

Rear dropouts.
I need to order spares.

Carbon fiber isn't very strong - it's just a plastic reinforced by carbon fibers. So contact points under pressure tend to be constructed of metal inserts. The rear dropouts on a track frame see a lot of abuse, so those are metal. I forgot to order spares. I'll want to get some dropout screws while I'm at it.

Potential Weak Points

I saw two potential weak points in the frame when researching online. The first was that the rear dropouts are pretty short. This helps handle a problem the longer dropouts had, where the weight of the rider bend the top part of the dropout up. This caused the opening to widen, making it difficult to secure the wheel. If you look at the geometry picture in the Dolan site, you can see the older DF3, with the super long dropouts.

The problem with a short dropout is that you can't move the wheel very much to take up chain slack. This means getting multiple chains for various gear combinations.

Since I prefer a very, very short chain stay, I'd probably want to keep the rear wheel as forward as possible anyway, so this "weakness" becomes a non-issue for me.

The second weak point is the seat post clamp. It's a wedge clamp with a very small bolt, with a very high torque rating. There are reports that it's virtually impossible to tighten enough to deal with jolts, like when you hit a seam on the track.

The workaround is pretty easy - you put a piece of pipe in the seat tube. Cut to the right length, the seat post will just sit on it. I have ideas for that "pipe" as well, so that critical cutting shouldn't be an issue.

So that's the frame. Next up, the wheels.

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