Quote:
Originally Posted by Cycle
I did the calculations for effective wind speed and angle, and put them in a spreadsheet.
It's titled "Wind Speed and Angle.ods". It's in OpenOffice.org .ODS format. See the attached file, zipped up.
I assumed the worst-case scenario of the wind hitting the bike at a 90 degree angle to its direction of travel. I calculated for wind speeds from 0 to 75 MPH, and bike speed from 0 to 150 MPH. You'll note the effective wind speed is always greater than the forward speed of the bike, and much greater than the actual wind speed... so the cross-ducting should work pretty well.
For instance, at 65 MPH forward speed and 25 MPH wind speed at a 90 degree angle, the effective wind speed is 69.642 MPH at 21.038 degrees. A 25 degree scoop would get pretty much the full blast of that effective wind speed, delivering a blast of air to the other side of the bike that exceeds the actual wind speed by ~44 MPH. That would push on the other side of the bike pretty effectively to counteract the side wind.
As the forward speed of the bike increases, the effective wind speed hitting the bike increases, and the angle at which it's hitting the bike decreases. So if I make the inlets at a 25 degree angle, that'll account for quite a variation in wind speed.
The natural inclination when getting hit with a side wind is to slow down. But that may not be the best choice with a cross-duct system... as you slow down, the effective wind speed drops, but the angle increases rapidly. You want to be traveling at a faster speed than the speed of the side wind. I'll have to figure out how to create some electronics that measures side wind and forward speed and recommends the best speed.
|
The volume of air leaving the duct would be miniscule compared to the volume of the leeward separated wake of the rig.I can't imagine that the duct provides enough porosity in the body to compensate for the pressure differential across the body.
Consider the central blow hole in a conventional military parachute canopy.Yes the chute is ventilated,but it still has Cd 1.35.If you land in a wind you must cutaway the capewells or the thing will drag you to your death even though it's 'ducted.'
I'd have to check,but I think that competition at Battle Mountain is suspended if cross-course winds exceed 8-mph.These bikes just blow over and skid into the desert brush.
