If you didn't fall going up, you're good.I will get on this with some math when I get home. I am still struggling. Early today I got stuck walking up the down escalator at the mall. Boy am I tired
WAit !!! This little propeller moved this ...You could try this as an experiment next time you're at the track. With the car in neutral when the light turns green floor it and see what your mph is at the end of the 1/8th. You should be able to use an online calculator to figure out how much horsepower it took to make that mph. Be sure to video it and put it on your channel and share the link with us. ; )
Ha Ha !! Thanks for the laugh.However, at what RPM does the fan start to work like a propeller on an airplane and begin pulling the vehicle forward thus helping the vehicle go in a forward motion and offsetting the HP taken to turn the fan??
I'm going to feel totally let down if I can't get an answer ... the question has some merit ???
![]()
What diameter is the fan? How many blades does it have? What is the pitch of the blades? Is there a fan shroud? Is the fan properly positioned in the shroud? How wide are the tires? How much air is in them? Are you using synthetic lubricants? Do you have ceramic wheel bearings? What is the car's coefficient of drag? Why did I read this thread?
NopeI believe the word you are looking for is "cavitation"
Precisely why I called on our sites 2 math gurus!!!What diameter is the fan? How many blades does it have? What is the pitch of the blades? Is there a fan shroud? Is the fan properly positioned in the shroud? How wide are the tires? How much air is in them? Are you using synthetic lubricants? Do you have ceramic wheel bearings? What is the car's coefficient of drag? Why did I read this thread?
It's beyond my skillsPrecisely why I called on our sites 2 math gurus!!!
It's beyond my skills![]()
Propellers absolutely suffer this phenomenon, it's referred to as "stall", but it is a void in the atmosphere that has to collapse....just like a mini thunderclap. It resulted in many test pilot deaths trying to set top speed records early on, it's the reason turbine, impeller, and propeller engineering is so critical......it's true the intensity of hydraulic cavitation is much higher & concentrated on smaller areas, but to a guy/gal 4,000 feet above the ground, having Your prop shatter seems just a little more destructive......lol.Nope
“cavitation occurs only in liquids when the pressure drops below the vapor pressure of the liquid, causing vapor bubbles to form and then collapse, which creates shockwaves and damage. Fans, which operate in air, may experience related phenomena such as air vortices, flow recirculation, or stall due to impediments, but these are distinct from liquid cavitation. “
If You look up the Hall Chaparral CanAm cars, where they used 2 large 'cooling' fans that were actually generating a bunch of downforce,...You can get an idea of what You'd need to put on the front of the car to get any kind of meaningful input force on the car. Figuring the filtering thru' the rad, & the disorganized flow aft not actually applying pressure against the stationary ambient atmosphere, I'd say it has almost -0-% impact. You'd have to seal & streamline the nose of the car to & thru' the rad & the entire engine compartment, & have it exit underneath facing rearward, and I'm not sure it would get the car to move from a stop in neutral.
I guess i could have been more accurate but the point got across, and in air it’s not called cavitation. The McMurtry speirling took the fan car concept and ran with it, look that car up, it’s incredible. But generating downforce through ducted fans and ground effects is much different than generating forward thrust as you seem to know.If You look up the Hall Chaparral CanAm cars, where they used 2 large 'cooling' fans that were actually generating a bunch of downforce,...You can get an idea of what You'd need to put on the front of the car to get any kind of meaningful input force on the car. Figuring the filtering thru' the rad, & the disorganized flow aft not actually applying pressure against the stationary ambient atmosphere, I'd say it has almost -0-% impact. You'd have to seal & streamline the nose of the car to & thru' the rad & the entire engine compartment, & have it exit underneath facing rearward, and I'm not sure it would get the car to move from a stop in neutral.
Point Your exhaust tips straight back & You'll probably get as much thrust/pull, with a lot less work,...but if You wanna try it, I'll follow along......![]()
I guess i could have been more accurate but the point got across, and in air it’s not called cavitation. The McMurtry speirling took the fan car concept and ran with it, look that car up, it’s incredible. But generating downforce through ducted fans and ground effects is much different than generating forward thrust as you seem to know.

To answer the title of the thread proper,...hurting...all the way.
Need to know if that dill is kosher, if so, the answer is yes.....I'm still figuring this one out...."If a hen and a half can lay an egg and a half in a day and a half, how long will it take a one legged monkey to kick all the seeds out of a dill pickle?" I'll jump on the fan problem if/when I get done.
![]()
Through testing we found at an average 5000rpm the propulsion from a 16" fan is good for a 10th in the 1/4 at 3000#'s on averageHowever, at what RPM does the fan start to work like a propeller on an airplane and begin pulling the vehicle forward thus helping the vehicle go in a forward motion
But... you just put it right back at the top !!!Okay I think it's best if we just move on!