Friday, December 03, 2010

Tsunami - Preliminary 2.0 Thoughts & Ideas

As soon as I got my first Tsunami I threatened to get a second. The frame fit so well that I couldn't possibly go back to a 5 or 6 cm shorter setup. I always want to have a second bike in case something happens to the first. But life intruded and the whole season went by without a second Tsunami in the quiver.

Okay, to be frank, I bought 3 pairs of HED wheels - that's what intruded. My resources were stretched a bit with that.

Now, with things calming down a bit, I freed up some resources so I could go ahead and get that second frame.

When I ordered my first Tsunami, I knew that I'd want to make changes after I'd ridden it for a bit. I couldn't define the changes, nor could I define how much I'd ride the frame. Within a couple months I'd homed in on some tweaks I'd want to try on a second one.

The overall on the first Tsunami:
- Excellent length and saddle-bar drop.
- Excellent and predictable handling up front, as long as I kept the headset adjusted.
- Rear wheel seems unweighted in fast sweeping turns; requires a shorter stay.
- Rider incapable of exceeded 42 mph in a flat sprint; requires faster rider.

Reviewing the list above, it's apparent that I don't need to fix the fit. It's also apparent the front end is fine (head tube angle + fork rake).

It's also apparent that my forward weighted fit resulted in a little too little weight on the rear wheel. I made up for it by sitting further back on the saddle, but that then unweighted the front wheel. My natural tendency is to really dig in with the front wheel when diving into a turn. The rear wheel follows naturally.

The problem with my stretch limo top tube is that if I really bore down on the bars diving into a turn, the rear wheel was out in la-la land, unweighted, uncared-for, and totally unsupervised. It therefore took a life of it's own, skipping and dancing where ever it wanted.

Okay, it wasn't that bad, but I figured that I needed about 10mm less chainstay because I was sliding backwards on the saddle about 10mm from center. 10mm is about the most we could shorten the chainstay because I hadn't seen a stay less than 395mm long in forever (405mm is normal), and the last frame I saw that had a shorter stay was my own Basso. And that thing was short.

And while I was thinking that, I was secretly thinking about a radical solution that would allow me to get 385 or 390mm stays, perhaps by doing a double seat tube like the old radical crit bikes whose name escapes me once again. They had two seat stays going up from a stub seat tube (enough to hold the front derailleur I think) up to another stub seat tube (to hold the seat post). The twin stays allowed the rear wheel to scoot up a lot, resulting in ridiculously short chainstays to the tune of 370mm or 380mm. I sketched a bunch of these frames over the summer but ultimately decided against it, for reasons explained below.

The max speed of the bike... yeah, this really bothered me. I used to think 42 mph was a bad sprint for me, a ho-hum-haven't-warmed-up-yet sprint. But since the turn of the century (heh) I don't remember going faster than 41 mph in a sprint, and that was when I first got 175 cranks for the road bike.

Although kicking and fighting all the way, I've finally decided that my lack of speed is due to an overabundance of age.

Yeah, I got old.

So, to follow the theories I had as a kid ("old guys have real jobs and have nice bikes but ride slow; young guys have no job, no money, crappy bikes, but ride fast"), I decided to throw some money at the problem. Well, money and theory.

A little while ago I got into a somewhat heated discussion over aero road frames, meaning aero frames for mass start races. I vacillate between being a huge fan and a huge skeptic. I think all pros should be riding aero frames because at their level every bit counts.

At the same time I can see how that "bit" may not be enough to matter. Would it matter if McEwen road an aero road bike in the mountain stages of the Tour? Probably not. However, watching him lose over and over to Petacchi at the Giro (2007), should he have used aero wheels instead of box section ones? Probably.

So the one takeaway I had from the aero frame discussion was... okay, there were two. First, a very experienced wind tunnel engineer pointed out that an aero frame, at sprint speeds, is worth maybe 0.5 kph or about 0.3 mph. It could be as high as 1 kph (0.6 mph) but realistically that's about it.

As he put it, it would be more aero to toss your bottles than to worry about the frame.

The second takeaway was that an aero frame is ALWAYS an aero frame. I could train a lot or a little, eat a lot or a little, put on whatever wheel I felt like, whatever whatever whatever, but the aero frame would always be an aero frame.


That double seat stay arrangement with a tire jutting through it suddenly didn't seem like a good idea. Instead of one tube hitting the wind there, there'd be three (tire and two "seat tube stays"), they'd be wider (by the width of the two stays), and to top it off the tire would be pushing air forward.


I questioned Joseph (he of Tsunami Bikes) about aero tubing. You know, do the whole Cervelo aero frame in aluminum thing. He sent me some pictures of aero tubing and after looking at them, I put them aside so I could percolate ideas.

At Interbike 2010 I saw a lot of stuff and, interestingly enough, not a lot of data on aero road frames. No one was out there saying, "You're gonna kick butt because our frame will give you 1 mph in the sprint!" They weren't saying it because they couldn't. Too many variables. You know, the whole "just chuck your bottles, you'd be better off" thing.

And that got me thinking.

Aero road frames, bare, work pretty well. Even with wheels and components (cables) they work pretty well.

Then you have two enormous cylinders in the middle of the air flow.

Yep, water bottles.

What a disgrace. They used to make aero bottles (I have one somewhere, with a matching cage) but those aren't legal. So you have to use those honkin' big bottles.

Or not.

IB2010 showed me, again, the CamelBak gizmo where the water thing is built into the baselayer. I saw them in 2009 but didn't realize their significance in the mass start aero road world.

See, they would eliminate the honkin' big cylinders.

And suddenly aero tubing looked... promising.

Ideas properly percolated, I checked out the aero tubing shots Joseph sent me. I started sketching ideas on how to work on making the frame more aero.

I looked at shots of the bike, head on, sideways, and realized that I'll be in the worst case scenario. My bike is so small that there's barely anything hitting the wind - heck the head tube isn't even 100mm tall!

But you rarely hit wind head on. It's usually a side thing. And side winds, they like surface area. Sails. You can tack into the wind, i.e. sail a sailboat into a wind. That's how much wind likes surface area.

The aero tubing had surface area.

We decided on an aero downtube (of course), aero seat tube (of course - it's now significant if I have no bottles), and he suggested aero seat stays. Booyah!

Then the kicker. The aero seat tube would need to be cut out for the rear wheel. This meant that I could specify the chainstay length because the tubing no longer limited him. I had asked him about a shorter stay, under 400mm if possible.

He countered with an offer for a 390mm stay.

Well now.

He also sent me pictures of said stay, seat tube, etc in action. Probably because he figured I wouldn't believe him, partially to show me the clearance for rims and tires (they should clear the HEDs), and probably because they look so freakin' cool and he's proud of the frames he built.

And let me tell you, the set up will look so freakin' cool it'll blow your socks away. I have no idea how aero it'll be compared to the first Tsunami, but I can tell you that it should corner much better because of the shorter chainstay. It shouldn't lose much in rigidity.

It will weigh a bit more, and although that's not desirable, I figure I can handle that. I'm hoping to get a lighter fork (the original one sports a 456g fork) and possibly one or two other lighter widgets so the overall weight gain is negligible. Or negative even.

There's one more build detail that I have planned but that'll have to wait for a couple months. Stay tuned!


StevenCX said...

Post the design pics!

Aki said...

The design pics aren't too interesting - just the numbers I mentioned on a generic "frame". But as things progress I hope to have the "ultrasound" pics.

RandomAussieSprinter said...

Aki, I read recently that bottles actually make your bike MORE aero and by a significant amount.
The same study found a largish effect from zipping up your jersey if you want to try googling it.
P.S. White on black is hard to read, but enjoy reading your blog on my rss feeder tho!

Aki said...

I've read that too, about the bottle on the seat tube. I'm studiously ignoring it for now :) Seriously though I think that it'd depend on the seat tube, wheel, etc. I'm hoping that my set up will make the bottle "nose cone" (for the seat tube and rear wheel) unnecessary. Overall I'm hoping that the frame helps create a sail effect for those tangential wind conditions most often found in cycling.

I did order a skinsuit, am considering helmet details, and thinking about shoe covers and such. So I'm looking at the big picture.

As a fall back the frame will have bottle bosses. If I decide to use them I'll have the option. I even bought cages for the frame in March or April. Meaning the new frame ordered now, not the frame I'd just built up.