Posted: Thu Jan 30, 2003 4:40 pm
There are a few things going on in regards to flex.
Firstly in regards to the road we have several different kinds of things going on- in regards to flex in the system and maintaining the "correct suspension" ie road contact.
1. We have to absorb the larger surface imperfections in the road (cracks bumps etc.)
2. We must maintain contact with the road surface despite the surface abnormalities on the near micro scale.
3. We must adjust our suspension for differing g-forces through the turn and the effects on turning.
SO for "1" our "macro" suspension is our legs and we endeveor to absorb cracks in the pavement by "deweighting our decks". Since we don't have true shock absorbers and Independent suspension we must deweight the entire deck (not so good a way to deal with it) it would be like comparing how a regular car handles potholes and how a guy in a "hopping lowrider" might try to "pre hop" a pot hole ever so slightly to not bottom out his low ride.
Number "2" handles the courseness or "pebbleyness" of the road. This is optimized through durometer choice- and the thickness of the supported and unsupported uerthane on the wheel. Obviously the ground is not as smooth as glass so our traction patch is reduced. We want enough deformation into the surface to increase our traction patch, but not enough to mush in front of the wheel (Ie pushing a wavefront that is optimally too large relative to the diameter of the wheel) Such a overly deforming wheel would be slow. Go too hard in the wheel or too little supported and unsupported uerthane and you are only riding the "peaks of the pebbles" and with such a small contact patch you can "wax out" during a turn. Not to mention it is a hard ride.
Obviously the more level the asphalt is- the harder a durometer you can run- except to the point of running too hard a wheel which "deforms the pavement on a hot day" and pushes a "pavement wavefront" (yes its on a very micro scale- but sinec pavement is so much more viscous it doesn't take much of a wave height ot have a similar effect)in front of the wheel - also bad and slow.
In "3" we see how the cornering affects grip of the system. in a hard corner we exert more lateral force on the ground and urethane. In a ZERO flex deck the ability to "dole out" a smooth progressive increase in pressure that is perfect in regards to the arc of a turn is limited by the prowess of the rider. And for the harder and faster the run the harder it is to "modulate" the amount of force needed.
Most riders opt for having the FLEX deck do this by loading the deck and having the deck "remodulate" the force to the pavement. Also the deck may be able to assist in "remodulating" the force better than the rider can. For instance....we could all throw a spear, and certainly we could throw a spear the size of an arrow- but using a flexing bow helps to convert one aspect of our fitness into another. Ie we are converting Strength into Quickness- using the flexing bow for conversion.
How the bow accelerates the force is a function of the design of the bow/flexing skateboard and the duration of the speed is the "pop- period" of the deck. The shorter the "pop-period" the better the deck is suited to short turns of fewer degrees at high fequency (TS). The longer the "pop-Period" of the deck the better the deck is suited for drawn out turns that take a while to complete (GS).
Strangley enough....when the turns are very long and wide and drawn out- though small in degrees- we have a turn that is "Slow" enough in terms of building g-forces to react using our body. Such an example would be akin to using a servo controlled subwoofer because the waves are at a low enough frequency for a slow servo to be considered "fast acting" for such a system. Our legs can react fast enough at long drawn out turns in Super G and so long travel flex can become uneeded in these situations- especially where the deck could hit a resonant fequency. (look at how the rider lowers himself in a super g turn and how bent his legs are- he is "human suspension" and pavement changes in terms of very elongated waves are treatable using this riding style- extreme flex would be more a detriment than a help)
Lastly in "3" the wheelbase ELONGATES during high flex- the center of gravity LOWERS and the turning geometry of the trucks INCREASES. Hmmm sounds like we are making any deck more into a GS deck ie longer wheelbase, slightly increased turning geometry for both trucks, and lower camber. And indeed this is what happens.
We are making our board more suited for the longer turn by altering the boards characteristics while riding it- simultaneously increasing our traction by deforming the wheel with downforce (as opposed to overwhelming the wheel with lateral force)and by loading the wheel first in the downward direction we are taking up some of the slop which might otherwise be used to overwhelm the wheel in the lateral direction.
The shortest distance between two points is....a straight line.
So in hitting the apex of the turn in a widely offset course - at slow speeds-sub 15mph (otherwise the wheels might be overwhelmed latterally) a board with significant flex and high camber would allow the turning arc to get much tighter resulting in a "Z" turn (note the shape of the letter Z) with increased steering "around the cones" and straighter steering "between the cones". Such a deck was ridden by Marus Stroble in Morro Bay 2001.
Add a lot of speed and the "Z" turn becomes useless (lateral forces build too quickly due to lateral g's which overwhelm the system) and a different line and board truck type should be used.
So board flex is part suspension, part truck geometry. The flex should match the rider's weight for the intended course and the riders ability to drive into the deck.
And of course we haven't touched on how important the first derivitave of flex ie the acceleration or progressiveness of the flex is.
Firstly in regards to the road we have several different kinds of things going on- in regards to flex in the system and maintaining the "correct suspension" ie road contact.
1. We have to absorb the larger surface imperfections in the road (cracks bumps etc.)
2. We must maintain contact with the road surface despite the surface abnormalities on the near micro scale.
3. We must adjust our suspension for differing g-forces through the turn and the effects on turning.
SO for "1" our "macro" suspension is our legs and we endeveor to absorb cracks in the pavement by "deweighting our decks". Since we don't have true shock absorbers and Independent suspension we must deweight the entire deck (not so good a way to deal with it) it would be like comparing how a regular car handles potholes and how a guy in a "hopping lowrider" might try to "pre hop" a pot hole ever so slightly to not bottom out his low ride.
Number "2" handles the courseness or "pebbleyness" of the road. This is optimized through durometer choice- and the thickness of the supported and unsupported uerthane on the wheel. Obviously the ground is not as smooth as glass so our traction patch is reduced. We want enough deformation into the surface to increase our traction patch, but not enough to mush in front of the wheel (Ie pushing a wavefront that is optimally too large relative to the diameter of the wheel) Such a overly deforming wheel would be slow. Go too hard in the wheel or too little supported and unsupported uerthane and you are only riding the "peaks of the pebbles" and with such a small contact patch you can "wax out" during a turn. Not to mention it is a hard ride.
Obviously the more level the asphalt is- the harder a durometer you can run- except to the point of running too hard a wheel which "deforms the pavement on a hot day" and pushes a "pavement wavefront" (yes its on a very micro scale- but sinec pavement is so much more viscous it doesn't take much of a wave height ot have a similar effect)in front of the wheel - also bad and slow.
In "3" we see how the cornering affects grip of the system. in a hard corner we exert more lateral force on the ground and urethane. In a ZERO flex deck the ability to "dole out" a smooth progressive increase in pressure that is perfect in regards to the arc of a turn is limited by the prowess of the rider. And for the harder and faster the run the harder it is to "modulate" the amount of force needed.
Most riders opt for having the FLEX deck do this by loading the deck and having the deck "remodulate" the force to the pavement. Also the deck may be able to assist in "remodulating" the force better than the rider can. For instance....we could all throw a spear, and certainly we could throw a spear the size of an arrow- but using a flexing bow helps to convert one aspect of our fitness into another. Ie we are converting Strength into Quickness- using the flexing bow for conversion.
How the bow accelerates the force is a function of the design of the bow/flexing skateboard and the duration of the speed is the "pop- period" of the deck. The shorter the "pop-period" the better the deck is suited to short turns of fewer degrees at high fequency (TS). The longer the "pop-Period" of the deck the better the deck is suited for drawn out turns that take a while to complete (GS).
Strangley enough....when the turns are very long and wide and drawn out- though small in degrees- we have a turn that is "Slow" enough in terms of building g-forces to react using our body. Such an example would be akin to using a servo controlled subwoofer because the waves are at a low enough frequency for a slow servo to be considered "fast acting" for such a system. Our legs can react fast enough at long drawn out turns in Super G and so long travel flex can become uneeded in these situations- especially where the deck could hit a resonant fequency. (look at how the rider lowers himself in a super g turn and how bent his legs are- he is "human suspension" and pavement changes in terms of very elongated waves are treatable using this riding style- extreme flex would be more a detriment than a help)
Lastly in "3" the wheelbase ELONGATES during high flex- the center of gravity LOWERS and the turning geometry of the trucks INCREASES. Hmmm sounds like we are making any deck more into a GS deck ie longer wheelbase, slightly increased turning geometry for both trucks, and lower camber. And indeed this is what happens.
We are making our board more suited for the longer turn by altering the boards characteristics while riding it- simultaneously increasing our traction by deforming the wheel with downforce (as opposed to overwhelming the wheel with lateral force)and by loading the wheel first in the downward direction we are taking up some of the slop which might otherwise be used to overwhelm the wheel in the lateral direction.
The shortest distance between two points is....a straight line.
So in hitting the apex of the turn in a widely offset course - at slow speeds-sub 15mph (otherwise the wheels might be overwhelmed latterally) a board with significant flex and high camber would allow the turning arc to get much tighter resulting in a "Z" turn (note the shape of the letter Z) with increased steering "around the cones" and straighter steering "between the cones". Such a deck was ridden by Marus Stroble in Morro Bay 2001.
Add a lot of speed and the "Z" turn becomes useless (lateral forces build too quickly due to lateral g's which overwhelm the system) and a different line and board truck type should be used.
So board flex is part suspension, part truck geometry. The flex should match the rider's weight for the intended course and the riders ability to drive into the deck.
And of course we haven't touched on how important the first derivitave of flex ie the acceleration or progressiveness of the flex is.