I am trying to build a small kind of RC car. Since its supposed to go at high speed I am thinking of using a fan to use the suction force to hold it down. When the fan is giving me sufficiently enough friction I can go at high speed to avoid slipping. But, my question is, if I use a DC motor without an encoder, there is bound to be a fluctuation in fan speed. But, is that fluctuation enough to make the speed of my car increase or decrease to a noticeable amount?
So....gravity insufficient or does it run across the ceiling...??
Diagrams and scale of the vehicle would possibly be helpful.
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Google "Brabham BT46"
It sounds like you are trying to simulate "ground effects", it should work but how well etc I do not have a clue.
Did you first try very soft rubber tires?
If the fan were mounted horizontally, I would worry more about the torque and gyroscopic effects on the cars steering.
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Gravity insufficient, runs horizontally
Is the fan for horizontal push?
Remember, ALL the torque/power applied to the fan is ALSO applied to your car body. So, the car will tend to turn in the opposite direction of the fan rotation. Are you prepared to control that torque on the car?
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I didn't quite understand what you meant to say, I thought that if the fan is facing downwards, there shouldn't be any net torque on car in horizontal direction because the fan is facing vertically downwards.
So the torque will be in the horizontal plane, no?
(Yaw)
Really? How does the fan motor operate if NOT attached to the car? If it is just free to turn, the motor will turn when the fan turns. Hold the fan and power the motor. What happens? The motor turns. When the motor is attached to the car, the motor STILL wants to turn.
Ok so, I didnt think so much could happen, I am gonna do some research and then ask about this. Is there any term that can describe this phenomenon?
Even more effect is the gyroscopic reaction at 90 degrees to external force, that is to say If this spinning fan is tilted (pitched forward/backward) on the X axis, the fan will twist (roll left/right) on the Y axis.
How would it be any different than just adding weight (mass)? In both cases, you will increase tire friction (Isn't that what you want?).
Isaac Newton's Third Law.
Will try that.
Because torque effects once the fan is running happen when the axis is tilted fast enough to matter. But yeah a hard spinup of a powerful fan might spin the car too! Torque is not a monopole!
Downforce?