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Aerodynamic downforce with a twist

  1. Jan 31, 2014 #1
    Greetings ....I'm about to embark on a new racing project.....I am a land speed racer ( top speed on a salt lake surface) in Australia, which I have been involved in for some 15 years. This new project involves taking a sit on motorcycle ( similar to a current sports bike but different) to in excess of 500kph I have most of the design sorted BUT I will be attempting to produce traction via inverted wings/ and or ground effects ...this has never been tried before ( for a motorcycle ).

    There are no rule restraints so it is an open book to try anything, the bike will remain in the vertical axis predominately with a small percentage of roll and yaw depending on relative wind direction and velocity.

    Not being an aerodynamicist it is a steep learning curve as to finding what has a chance of success....I have ideas and designs of what may work but have hit a brick wall.

    Seeking some assistance in moving forward

    Cheers
     
  2. jcsd
  3. Jan 31, 2014 #2

    Ranger Mike

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    welcome racer...good to see innovation is alive and well down under!
     
  4. Feb 15, 2014 #3
    I see a lot of guys going to asphalt and concrete for motorcycle records because of the available traction.

    The sanctioning bodies and timing associations will get caught up some day.

    Bill warner made 311mph in 1.5 miles and was on his way to 300mph in the standing mile when he died.
     
  5. Apr 4, 2014 #4
    Hi, I love land speed racing down in ausie-land. I knew a guy that drove a landspeed car down there and was trying to raise money to get his car over here. Cool guy...

    Onto the question. Yes, you can use ground effects on a motorcycle to enhance speed and yes, you can use aerodynamics (not inverted wings) to do so. I don't know many land speed racers who don't use some kind of aero to hold them down but really, most cars try to stay slippery. There is a fine line between hurting and helping and that is your drag co-efficient. You can create down force but it will always add drag, the more drag you add, the more power you need to over come said drag.

    Also in land speed racing you have to be careful about where your drag is. Top heavy drag is really bad. Sure your spoiler may only weigh 15 lbs but when you are going 200 mph it can multiply exponentially (so forget 500 kph if you die at 200 mph).

    Lastly, I might avoid ground effects too much. Reason being ground effects work well with space. If you have a car, you can direct the air away from the tires (less upwards pressure on the car) and out through the back, but with a bike, most of that air is going under your tires... so when does that become a problem? When the compressed air infront of your tires is too much for your bike.

    There is a lot of stuff that I am leaving out but this is a good summery, don't get me wrong, I would love to see it happen but you have to know what you are doing.
     
  6. Jul 7, 2014 #5
    I would think any faring for the tires that comes down close to the ground would help tremendously with reducing lift, and may even generate some downforce. Of course close to the ground it has to be pretty narrow/close to the tire to avoid contact when leaning or turning. Downforce is mainly about moving air which has mass upwards, and creating low pressure areas under the lower surfaces, particularly ones close enough to the ground to have significant ground effect.

    I would think that you would be aiming for near zero lift, compared to a stock bike that has positive lift. Any downforce gained at speeds that it would be useful(when accelleration rates are high) would turn into a lot of drag and too much downforce at Vmax.

    I would concentrate on things that can reduce lift while actually decreasing drag first, like tire fairings and maybe a diffuser of some sort to keep airflow attached at the rear, bringing air from the sides up to meet with the air coming off the rear faring behind the driver.

    Does the bike need to be able to turn around while you are riding it at the end of a run?
     
    Last edited: Jul 7, 2014
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