May 19

May 19, 2005

Big gears, a roll bar vacuum formed fairing and epic training.

My friend James Kenny has been helping me with some gearing issues. My goal, is to hit a cruising speed of around 50 to 60 kph on 120 to 140 watts of input power with a cadence of 70 rpm. It's a bit vague at this point because I'm not sure exactly what the drag coefficient of the fairing will actually be, and what the rolling resistance of the tires will end up at.

John Snyder has been providing some tire and Crr advice - he says that a good clincher should be able to get a Crr of .0025 on a smooth surface, and the word on tubulars is they are LESS efficient than clinchers because of the sticky glue used. Bens computational flow software predicts a CdA of .27'ish (sq ft). With a Crr of .003 and a CdA of .3, I should be able to hit 33 mph (56 kph) with 100 watts of input power and a cadence of 70 rpm with these gears.

The main drive features my custom SRM 155mm cranks bolted onto the SRM power meter and a 39 tooth chain ring. The tire has about 2 mm of clearance between the chain wrapped around that gear - so it's the largest chain ring I can do without the tire hitting it. That chain runs to the secondary drive which is a Tiagra road triple. The small chain ring is a 30 tooth and I bolted on an old 55 tooth ring that I had lying around. The cassette is a standard road 11-23.

My lower speed option is a compact crank set for the intermediary drive which is 50-34. I could make the high speed and low speed chain ring sets swapable, but I would have to replace the chain each time, as the compact chain ring set is much smaller. The compact would get me a top speed of 51 kph at 80 rpm with 100 watts which is also acceptable.

Now - onto the fairing. I would like to vacuum form a clear Vivak fairing using the female mold we're making from the foam plug. There are two reasons I would rather do this than make a carbon or kevlar fairing. The first reason is with a clear plastic fairing, I can spray paint the inside of the fairing and leave small window holes in strategic places for both visibility and avoiding direct sun to reduce solar heating. This is the general idea:

The second reason, is that since my frame is the exact shape of the fairing, it should provide enough rigid structure to solidly support a very thin fairing.

It appears that Vivak is not available in sheets any longer than 8 feet. I do not want a split in the fairing by joining two halves together because it may interfere with clean air flow over the surface, and it would require two separate molds. According to the Vivak properties sheet, it can be ultrasonically welded, so I may be able to join two 8' sheets together to make one large enough to form the entire 10 foot fairing in one shot.

Raymond Gage is building his "Orion Speed Trike" for World Human powered Speed Challenge in Battle Mountain, NV and is also investigating vacuum forming a Vivak fairing. He told me that since Vivak melts at a temperature below boiling water, that it is possible to heat up your Vivak sheet using hot water.

I made a styrofoam mock-up of the horizontal member - I'll call it a 'wing' for lack of some other term which I can't think of.

The point to this wing is to provide extra support for the fairing and some crash protection for the driver. After mocking up a styrofoam version, it occurred to me that even if I were to form it out of carbon fiber, it would be far too thin to provide any kind of rollbar-type crash protection. I think the curved surface of the plastic fairing will maintain it's shape without any kind of side support - especially if it is fastened securely all along the edge of the sandwich frame.

As far as crash protection goes, all I really need is a strong rib that extends out to the width of my shoulders to take the weight of the bike if it tips over. Between that rear rib, and another the width of my feet at the nose, they should take most of the weight if the bike were to crash. A thin layer of Kevlar on the inside wall of the plastic fairing could protect my exposed arms and legs from road rash.

I mocked up some styrofoam ribs to get a better feel for how they could protect me.

3 areas of protection: the rear, just behind the seat back, the base right under my seat bottom and the nose just in front of the full extension of the cranks.

When I tipped it over, I noticed that the middle support was further out than the other two and caused the bike to rock between the nose support and the rear support - which is something that I don't want.

I removed the mid support and it looks like the bike would balance between the nose and rear support ribs taking the majority of the weight. I say majority because in the case of a tip over, gravity would force my body down causing my arms, shoulders and legs to grind across the pavement. However, only my body weight would be pressing me into the ground, while the ribs would keep the weight of the bike off me. Hopefully, a thin kevlar layer bonded to the inside of the plastic fairing should provide enough skid protection to stop my skin from actually peeling away.


Training is going very well - I haven't gotten sick or injured yet and I am holding up to the volume quite well so far.

Elite - ready for the Epic day!

I hit my peak training day yesterday - my 6 week out EPIC TRAINING DAY. 105 km ride to Banff, then a 20 km trail run, then 105 km back to Calgary for a total of 9.5 hours.

I'm taking it easy today - trying to drink lots of water and eat plenty of carbs to restock. Tomorrow is another 100 miler day, but with some serious, steady intensity.

While training, I have been listening to "The Perfect Mile" by Neal Bascomb - a 14 hour audio book about the breaking of the 4 minute mile. Here is the Publisher's summary:

"They said it could never be done. No human could ever run a mile in less than four minutes. In 1952, three amazing athletes begged to differ; English medical student Roger Bannister, Australian privileged son John Landy, and American farm boy Wes Santee. At a time when war raged in Korea and Edmund Hillary dared to scale Mount Everest, these three marvelous runners raced into the spotlight and stole the attention of a breathless world. Dramatic, exciting, and gloriously reminiscent, The Perfect Mile is an endlessly fascinating tale of heroic achievement and a testament to the determination of the human spirit. "

I highly, highly recommend it!


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