Here's the pic: http://forum.slowtwitch.com/gforum.cgi?post=352692
and notes on this fork I received from John Cobb (and no, I am not a dealer for Blackwell):
"If you’re going to set out to build a new TT fork, then it seems that you would need to offer something innovative in air control while offering the expected light weight and side stiffness. Anybody can build a fork with thin cross section legs, that’s what the air sees as the fork is one of the first things to interface with the air on a bicycle. To make a fork offer a significant advantage over a thin legged fork requires some deeper thought as to just what a fork can do.
Air management is a key ingredient to making bikes go through the air with less effort. Everything that the air comes in contact with on a bike requires energy to push through. Humans don’t generate very much power, so making the bike slip through the air with the least disturbance is better. If you look at things on the bike that a fork can effect, it’s three main areas. Fork surface area, wheel interface and air control over the riders legs.
[1] - Thin blade forks can only effect one of those areas, the surface area the air “sees” when moving.
[2] - The front wheel generates some very complex airflow problems at the front of the bike. The spinning wheel takes a lot of power to turn because of the spokes trapping air in the center of the wheel making them act like “paddles” as they try to cut through this air. Another problem is the wheel ads frontal area to the bike, over 12” wide, as the oncoming air has to boat wake around the spinning wheel. This generated frontal area has the same effect as wearing a wind breaker, you’ve seen them on riders, all blown up. Another wheel problem is the parasitic drag of the air staying attached to the tire tread. This air builds up to form a huge bubble right behind the fork crown and requires the tire tread to drag through it as it spins.
[3] Air flowing over the riders legs. If the bikes moving, the legs are usually spinning and this interaction with the air takes power. By having the fork blades help control the width of the air off the front of the bike, we can save several watts of power during pedaling.
The Flow Fork has narrow blades for lower drag but the difference is in the aspect ratio. Flow Fork blades are much wider when looked at from the side than any other fork on the market today. There are reasons for this, stiffness and air management being the main two. The Flow Fork also has a complex frontal shape, it’s wide at the hub area then stays wide about 1/3 up to help control the boat wake formed by the spinning wheel. The fork begins to taper in at the same angle as the wheel spokes run, this continues to help control the amount of air that the wheel has to spin through, eliminating a lot of the “paddle wheel” effect. The width of the fork blades is also very important in this area to help form a guide so the air flow is very narrow as it heads towards the riders legs. The top part of a spinning wheel is the area that requires the most attention. The top of a wheel is going much faster than the forward motion of the bike, generating a lot of air commotion. At the top of the Flow Fork there are two “vents”. These vents are very effective relieving air compression caused by the spinning spokes and also causing a pressure drop by the fork crown so the air bubble can’t build up behind the fork crown area. Controlling the air at the top part of a wheel gives the added benefit of making the wheel faster. Unless it’s a disc wheel, it will have some type of spokes and these take a lot of energy to spin through the air. By pulling some of the air away from the sides of the wheel, the spokes have less to be pushed through.
An added benefit of the Flow Fork is the amount of surface area behind the center line of the fork. This mass area of the fork will act much like a rudder, helping to take the twitchiness out of deep section aero wheels.
I hope this helps explain some of the Flow Fork benefits, this fork was designed with only one goal, to be the fastest, it does not make any concessions to foreign “Pro rules” that don’t apply to American Triathletes and all age group racers. The fork offers a look into the ways of innovative thinking, to make the bike make itself faster.
Thanks,
John cobb"
and notes on this fork I received from John Cobb (and no, I am not a dealer for Blackwell):
Blackwell Flow Fork
"If you’re going to set out to build a new TT fork, then it seems that you would need to offer something innovative in air control while offering the expected light weight and side stiffness. Anybody can build a fork with thin cross section legs, that’s what the air sees as the fork is one of the first things to interface with the air on a bicycle. To make a fork offer a significant advantage over a thin legged fork requires some deeper thought as to just what a fork can do.
Air management is a key ingredient to making bikes go through the air with less effort. Everything that the air comes in contact with on a bike requires energy to push through. Humans don’t generate very much power, so making the bike slip through the air with the least disturbance is better. If you look at things on the bike that a fork can effect, it’s three main areas. Fork surface area, wheel interface and air control over the riders legs.
[1] - Thin blade forks can only effect one of those areas, the surface area the air “sees” when moving.
[2] - The front wheel generates some very complex airflow problems at the front of the bike. The spinning wheel takes a lot of power to turn because of the spokes trapping air in the center of the wheel making them act like “paddles” as they try to cut through this air. Another problem is the wheel ads frontal area to the bike, over 12” wide, as the oncoming air has to boat wake around the spinning wheel. This generated frontal area has the same effect as wearing a wind breaker, you’ve seen them on riders, all blown up. Another wheel problem is the parasitic drag of the air staying attached to the tire tread. This air builds up to form a huge bubble right behind the fork crown and requires the tire tread to drag through it as it spins.
[3] Air flowing over the riders legs. If the bikes moving, the legs are usually spinning and this interaction with the air takes power. By having the fork blades help control the width of the air off the front of the bike, we can save several watts of power during pedaling.
The Flow Fork has narrow blades for lower drag but the difference is in the aspect ratio. Flow Fork blades are much wider when looked at from the side than any other fork on the market today. There are reasons for this, stiffness and air management being the main two. The Flow Fork also has a complex frontal shape, it’s wide at the hub area then stays wide about 1/3 up to help control the boat wake formed by the spinning wheel. The fork begins to taper in at the same angle as the wheel spokes run, this continues to help control the amount of air that the wheel has to spin through, eliminating a lot of the “paddle wheel” effect. The width of the fork blades is also very important in this area to help form a guide so the air flow is very narrow as it heads towards the riders legs. The top part of a spinning wheel is the area that requires the most attention. The top of a wheel is going much faster than the forward motion of the bike, generating a lot of air commotion. At the top of the Flow Fork there are two “vents”. These vents are very effective relieving air compression caused by the spinning spokes and also causing a pressure drop by the fork crown so the air bubble can’t build up behind the fork crown area. Controlling the air at the top part of a wheel gives the added benefit of making the wheel faster. Unless it’s a disc wheel, it will have some type of spokes and these take a lot of energy to spin through the air. By pulling some of the air away from the sides of the wheel, the spokes have less to be pushed through.
An added benefit of the Flow Fork is the amount of surface area behind the center line of the fork. This mass area of the fork will act much like a rudder, helping to take the twitchiness out of deep section aero wheels.
I hope this helps explain some of the Flow Fork benefits, this fork was designed with only one goal, to be the fastest, it does not make any concessions to foreign “Pro rules” that don’t apply to American Triathletes and all age group racers. The fork offers a look into the ways of innovative thinking, to make the bike make itself faster.
Thanks,
John cobb"
